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澄清度檢查法系將藥品溶液與規(guī)定的濁度標準液相比較，用以檢查溶液的澄清度。除另有規(guī)定外，應采用第一法進行檢測。
品種項下規(guī)定的“澄清”，系指供試品溶液的澄清度與所用溶劑相同，或不超過0.5號濁度標準。“幾乎澄清”，系指供試品溶液的濁度介于0.5號至1號濁度標準液的濁度之間。
第一法（目視法）
除另有規(guī)定外，按各品種項下規(guī)定的濃度要求，在室溫條件下將用水稀釋至一定濃度的供試品溶液與等量的濁度標準液分別置于配對的比濁用玻璃管（內徑15-16 mm,平底，具塞，以無色、透明、中性硬質玻璃制成）中，在濁度標準液制備5 分鐘后，在暗室內垂直置于傘棚燈下，照度為1000 lx，從水平方向觀察、比較。除另有規(guī)定外外，供試品溶解后應立即檢視。
第一法無法準確判定兩者的澄清度差異時，改用第二法進行測定，并以其測定結果進行判定。
濁度標準存貯液的制備 稱取于105℃干燥至恒重的硫酸肼1.00 g，置于100 ml量瓶中，加水適量使溶解，必要時可在40℃的水浴中溫熱溶解，并用水稀釋至刻度，搖勻，放置4-6小時；取此溶液于等容量的10%烏洛托品溶液混合，搖勻，于25℃避光靜置24小時，即得。該溶液置冷處避光保存，可在2個月內使用，用前搖勻。
濁度標準原液的制備 取濁度標準貯備液15.0 ml，置1000 ml量瓶中，加水稀釋至刻度，搖勻，取適量，置1 cm吸收池中，照紫外-可見分光光度法（通則0401），在550 nm的波長處測定，其吸光度在0.12-0.15范圍內，該溶液應在48小時內使用，用前搖勻。
濁度標準液制備 取濁度標準原液與水，按照下表配置，即得。濁度標準液應臨用時制備，使用前充分搖勻。
第二法（濁度儀法）
供試品的濁度可采用濁度儀測定。溶液中不同大小、不同特性的微粒物質包括有色物質均可使入射光產生散射，通過測定透射光或者散射光的強度，可以檢查供試品的濁度。儀器測定模式通常有三種類型，透射光式、散射光式和透射光-散射光比較測量模式（比率濁度模式）。
1.儀器的一般要求
采用散射光式濁度儀時，光源峰值波長為860 nm；測量范圍應包含0.01-100NTU。在0-10NTU范圍內分辨率應為0.01NTU；在10-100NTU范圍內分辨率應為0.1NTU.
2.適用范圍及檢測原理
本法采用散射光式濁度儀，適用于低、中濁度無色供試品溶液的濁度測定（濁度值為100NTU以下的供試品。）因為高濁度的供試品會造成多次散射現象，時散射光強度迅速下降，導致散射光強度不能正確反映供試品的濁度值。0.5-4號濁度標準液的濁度值范圍約為0-40NTU。
采用散射光式濁度儀測定時，入射光和測定的散射光呈90℃夾角，入射光強度和散射光強度關系式如下。
I=K’T I0
式中 I為散射光強度，單位為cd；
I0 為入射光強度，單位為cd；
K’為散射系數；
T為供試品溶液的濁度值，單位為NTU（NTU是基于福爾馬肼濁度標準液液測定的散射濁度單位，福爾馬肼濁度標準液即為第一法中的濁度標準貯備液）。
在入射光I0不變的情況下，散射光強度I與濁度值成正比。因此，可以將濁度測量轉化為散射光強度的測量。
3.系統(tǒng)的適用性試驗
儀器應定期（一般每月一次）對濁度標準液的線性和重復性進行考察，采用0.5號至4號濁度標準液進行濁度值測定，濁度標準液的測定解果（單位NTU）與濃度間應呈線性關系，線性方程的相關系數應不低于0.999；取0.5號至4號濁度標準液，重復測定5次，0.5號和1號濁度標準液測量濁度值的相對標準偏差應不大于5%，2-4號濁度標準液測量濁度值的相對標準偏差不大于2%。
4.測定法
按照儀器說明書要求并采用規(guī)定的濁度液進行儀器校正。溶液劑直接取樣測定；原料藥或者其它劑型按照個論項下的標準規(guī)定制備供試品溶液，臨用時制備。分別取供試品溶液和相應濁度標準液進行測定，測定前應搖勻，并避免產生氣泡，讀取濁度值。供試品溶液濁度值不得大于相應濁度標準液的濁度值。
The purpose of this test is to provide the details for the visual comparison of the color and/or turbidance of sample solutions of certain concentration to a standard solution or a series of standard solutions of known concentration. Where a color or turbidity comparison is directed, follow the procedures and conditions outlined below for performing these tests.
本試驗的目的是提供特定濃度的樣品溶液與已知濃度的標準溶液或一系列標準溶液的顏色和/或濁度的視覺比較細節(jié)。如果需要進行顏色或濁度比較，請遵循以下程序和條件進行這些測試
Comparison vessels: Color-comparison tubes matched as closely as possible in internal diameter, in depth of sample solution, and in all other respects should be used.
對比容器：應使用內徑、樣品溶液深度和所有其他方面盡可能匹配的顏色對比管。
Viewing conditions for turbidity comparison: Tubes should be viewed horizontally against a dark background with the aid of a light source directed from the sides of the tubes.
濁度比較的觀察條件：應在黑暗背景下，借助從管子側面發(fā)出的光源水平觀察管子。
Viewing conditions for color comparison: Tubes should be viewed downward against a white background. Most of the time, common room lighting is sufficient to perform the assessment. A light source directed from beneath the bottoms of the tubes may be used if needed and if the practice is consistent between the materials under comparison.
顏色比較的觀察條件：管子應在白色背景下向下觀察。大多數情況下，公共空間照明足以進行評估。如果需要，并且對比材料之間的實踐一致，可以使用從管底部下方引導的光源
1. INTRODUCTION 介紹
Nephelometry and turbidimetry are analytical techniques that are based on the principles of light-scattering phenomena. Light scattering is the physical phenomenon in which a beam of light changes its direction of propagation (known as deflection) as a result of interaction with sufficiently small matter particles. It has been established from the Maxwell electromagnetic theory that a prerequisite for scattering to occur is that the refractive indexes of the suspended particles must be different from those of the suspending liquid. The larger the difference, the more intense the scattering becomes. There are two types of light scattering: 1) elastic scattering, in which the wavelength of the scattered light and incident light are the same; and 2) inelastic light scattering, in which the wavelength of the scattered light and incident light are different. Only the first type of light scattering (elastic) is relevant to nephelometry and turbidimetry.
散射光濁度法和透射光比濁法是基于光散射現象原理的分析技術。光散射是一種物理現象，其中光束由于與足夠小的物質粒子相互作用而改變其傳播方向（稱為偏轉）。根據麥克斯韋電磁理論，散射發(fā)生的先決條件是懸浮顆粒的折射率必須不同于懸浮液體的折射率。差異越大，散射越強烈。光散射有兩種類型：1）彈性散射，其中散射光和入射光的波長相同；2）非彈性光散射，其中散射光和入射光的波長不同。只有前一種光散射（彈性）與散射光濁度法和透射光比濁法有關。
In turbidimetry, the intensity of the transmitted light is measured and the attenuation of the intensity of incident light as a result of scattering is measured at the direction of incident light (i.e., 0°) and compared to the intensity of incident light (blank measurement). The measured property is an indirect measurement of the scattering effect of the suspended particles and is referred to as turbidance. Any absorbance of light by the suspended sample will result in additional attenuation of light intensity (see Ultraviolet-Visible Spectroscopy <857> and Ultraviolet-Visible Spectroscopy—Theory and Practice <1857>). Hence, it is important to ensure that the material being measured does not absorb light at the measurement wavelength. Indeed the equations governing absorption and turbidimetry are the same (albeit with different values for the attenuation constants). In nephelometric techniques, the intensity of the scattered light at a 90° angle from the propagation direction of the incident light is measured. Therefore, a nephelometric measurement is a direct measurement of the scattering effect of suspended matter.
在透射光比濁法中，測量透射光的強度，并在入射光方向（即0°）測量散射導致的入射光強度的衰減，并與入射光強度進行比較（空白測量）。被測特性是懸浮顆粒散射效應的間接測量，稱為濁度。懸浮樣品對光的任何吸收都會導致光強度的額外衰減（參見<857> Ultraviolet-Visible Spectroscopy和<1857> Ultraviolet-Visible Spectroscopy—Theory and Practice）。因此，確保被測材料不會吸收測量波長處的光非常重要。實際上，控制吸收和濁度測定的方程式是相同的（盡管衰減常數的值不同）。在散射光濁度法中，測量與入射光傳播方向成90°角的散射光強度。因此，散射光濁度法濁度測量是對懸浮物散射效應的直接測量。
2. TERMS AND DEFINITIONS 術語和定義
Terms commonly used in describing turbidimetric and nephelometric techniques are:
• Turbidance (symbol, S): A measure of the decrease of the transmitted incident light beam intensity as a result of the light-scattering effect of suspended particles. The amount of suspended matter may be measured by observation of either the transmitted light (turbidimetry) or the scattered light (nephelometry).
log I0/It = kbc = T
I0 = intensity of incident light
It = intensity of transmitted light
k = molar turbidity coefficient
b = cell path length
c = concentration
T = turbidance
• Turbidity (symbol, τ): In turbidimetric measurements, the turbidity is the measure of the decrease in incident beam intensity/unit length of a given suspension. The International Organization for Standardization defines turbidity as “the reduction of transparency of a liquid caused by the presence of undissolved matter”.
• Turbidity Measurement Units: The turbidity units are stated using a descriptor which indicates the method of measurement.
• Nephelometric Turbidity Units (NTUs): When the turbidity is measured using a nephelometer, which measures the scattered light at a 90° angle from the direction of propagation of incident light, the units of turbidity are called nephelometric turbidity units (NTUs). The magnitude of NTU is defined based on the turbidity generated by primary formazin standard (a suspension made by mixing solutions of hydrazine sulfate and hexamethylenetetramine in water). Safer polymer-bead suspensions are now commercially available and are recognized as an acceptable alternative. However, all those standards are traced to formazin. The primary formazin standard solution has been assigned a turbidity of 4000 NTUs.
Other recognized units for turbidity include the formazin turbidity unit (FTU) and the formazin nephelometric unit (FNU). These units are equivalent to NTU for the range from 0–40 NTUs.
描述濁度法和濁度法的常用術語包括：
•濁度（符號S）：由于懸浮顆粒的光散射效應，透射入射光束強度降低的一種度量。懸浮物的量可以通過觀察透射光（比濁法）或散射光（濁度法）來測量。
log I0/It = kbc = T
I0=入射光強度
It=透射光強度
k=摩爾濁度系數
b=樣品池路徑長度
c=濃度
T=濁度
•濁度（符號，τ）：在透射光濁度測量中，濁度是給定懸浮液的入射光束強度/單位長度減少的量度。國際標準化組織將濁度定義為“由于存在未溶解物質而導致液體透明度降低”。
•濁度測量單位：渾濁度單位用一個描述符表示，該描述符指示測量方法。
•散射光濁度計濁度單位（NTU）：當使用散射光濁度法測量濁度時，濁度計以與入射光傳播方向成90°角的角度測量散射光，濁度單位稱為散射光濁度法濁度單位（NTU）。NTU的大小是根據初級福爾馬肼標準品（一種將硫酸肼和六亞甲基四胺溶液混合在水中制成的懸浮液）產生的濁度定義的。更安全的聚合物微珠懸浮液現已上市，并被*為可接受的替代品。然而，所有這些標準都可以追溯到福爾馬肼。初級福爾馬肼標準溶液的濁度為4000 NTU。
其他*的濁度單位包括福爾馬肼比濁法單位（FTU）和福爾馬肼濁度法單位（FNU）。這些單位相當于0-40 NTU范圍內的NTU。
3. APPLICATIONS 應用
Turbidimetric and nephelometric techniques have applications that include 1) concentration determination of solutions and/or suspensions (determination of several cations and anions by precipitating and suspending the resulting precipitate at well-controlled reaction parameters); 2) measurement of the degree of turbidity of turbid solutions or suspensions; 3) determination of weight-average molecular weights and dimensions of polydisperse systems in the molecular weight range from 1000 to several hundred million; 4) measurement of immunoassays’ reaction kinetics or kinetics of immunoprecipitations (rate nephelometry); 5) monitoring of cell and bacteria growth; and 6) particle size distribution determination of suspended material, particle counting, etc.
透射光比濁法和散射光濁度法技術的應用包括1）溶液和/或懸浮液的濃度測定（通過在控制良好的反應參數下沉淀和懸浮產生的沉淀物，來測定幾種陽離子和陰離子）；2）測量混濁溶液或懸浮液的濁度；3）測定分子量在1000到數億之間的多分散體系的重均分子量和尺寸；4）測量免疫分析的反應動力學或免疫沉淀動力學（比率散射濁度法）；5）監(jiān)測細胞和細菌的生長；6）懸浮物粒度分布測定、顆粒計數等。
Rate nephelometry is widely used for vaccine components assays and/or quantitation of components in blood serum. It is also used for host cell protein qualification in recombinant biopharmaceuticals. When using the technique, the measurement of the change in the light-scattering response by antigen–antiserum or antigen-purified antibody complexes is used to calculate the amount of antigen (Ag) or antibody (Ab) responsible for the immunological Ab-Ag precipitation reaction or agglutination reaction. Often the antigens under consideration are linked covalently or adsorbed to polymeric microspheres to increase the scattering efficiency; the resulting technique is known as "particle-enhanced immunoassay". Although the technique is described as nephelometry, usually both scattered and transmitted light are measured using the ratio instruments.
比率散射濁度法廣泛用于疫苗成分分析和/或血清成分的定量。它還用于重組生物制藥中的宿主細胞蛋白質鑒定。當使用該技術時，通過測量抗原-抗血清或抗原純化抗體復合物的光散射反應的變化，來計算導致免疫抗體-抗原沉淀反應或凝集反應的抗原（Ag）或抗體（Ab）的量。通常考慮抗原共價連接或吸附在聚合物微球上，以提高散射效率；由此產生的技術被稱為“顆粒增強免疫分析”。雖然這項技術被稱為散射光濁度法，但通常散射光和透射光都是用比率儀器測量的。
Nephelometric measurements are more reliable in low turbidity ranges (relatively low concentration of the scattering medium). In this range, a linear relationship is observed between the sample concentration and the detector’s signal intensity expressed as NTU. As the concentration increases, so does the incidence of multiple scattering that deviates the response from the linearity. The maximum NTU value, which supports a reliable linearity relationship, is in the range of 1750–2000 NTUs. Turbidimetry is preferred for higher turbidity ranges (concentrations of the scattering media). To achieve consistent results, all measurement variables must be carefully controlled. Where such control is possible, extremely dilute suspensions may be measured.
散射光法濁度測量在低濁度范圍（散射介質濃度相對較低）更可靠。在該范圍內，觀察到樣品濃度與檢測器信號強度（以NTU表示）之間存在線性關系。隨著濃度的增加，多次散射的入射角也會增加，從而偏離線性響應。支持可靠線性關系的最大NTU值在1750–2000 NTU范圍內。透射光比濁法適用于更高的濁度范圍（散射介質的濃度）。為了獲得一致的結果，必須仔細控制所有測量變量。在可能的情況下，可以測量極稀的懸浮液。
4. INSTRUMENTATION 儀器儀表
Instruments used for turbidimetric and nephelometric measurements are called turbidimeters and nephelometers, respectively. Generally, these instruments consist of a mercury lamp with filters for the strong green or blue lines, a shutter, a set of neutral filters with known transmittance, and a sensitive photomultiplier, which can be mounted fixed at 0° or at a 90° angle from the incident light propagation direction, or on an arm that can be rotated around the solution cell and set at any angle from −135° to 0° to +135° by a dial outside of the light-tight housing. Solution cells are of various shapes, such as square for measuring 90° scattering; semioctagonal for 45°, 90°, and 135° scattering; and cylindrical for scattering at all angles (see Figure 1).
用于透射光比濁法和散射光濁度法測量的儀器分別稱為透射光濁度計和散射光濁度計。通常，這些儀器包括一個帶有濾光器的汞燈（用于強綠線或藍線）、一個快門、一組具有已知透射率的中性濾光器和一個靈敏的光電倍增管，該光電倍增管可安裝在與入射光傳播方向成0°或90°角的位置，或者在一個臂上，它可以圍繞溶液單元旋轉，并通過不透光外殼外的表盤設置為−135°到0°到+135°的任何角度。溶液池的形狀多種多樣，例如用于測量90°散射的正方形；45°、90°和135°散射為半八角形；圓柱形可適用于所有角度的散射（見圖1）。
Figure 1. Representative nephelometric (turbidimetric) instrument. Note that Detector 2 may be mounted on a movable arm.
圖1。代表性濁度儀。注意，探測器2可安裝在可移動臂上。
Turbidity also can be measured with a standard photoelectric filter photometer or spectrophotometer, preferably with illumination in the blue portion of the spectrum. Nephelometric measurements require an instrument with a photocell placed so as to receive scattered, rather than transmitted, light. Because this is the same geometry used in fluorometers, they can be used as nephelometers by proper selection of filters. A ratio turbidimeter combines the technology of 90° nephelometry and turbidimetry. It contains photocells that receive and measure scattered light at a 90° angle from the sample as well as receiving and measuring the forward scatter in front of the sample. It also measures light transmitted directly through the sample. Linearity is attained by calculating the ratio of the 90° angle scattered light measurement to the sum of the forward scattered light measurement and the transmitted light measurement. The benefit of using a ratio turbidimetric system is that the measurement of stray light becomes negligible. In addition, the determination of turbidity of colored suspensions is done exclusively using turbidimetric or nephelometric instruments with ratio mode because this procedure compensates for the attenuation of light as the result of the suspension color. Typically, the light source in these instruments is a tungsten lamp with most of the light intensity at about 550 nm operating at the filament temperature of 2700 K. Other suitable light sources are also available. Typically, the detectors are ▲silicon diodes▲ (ERR 1-May-2019) and photomultipliers. An alternative for eliminating the color effect involves using an infrared light-emitting diode as a light source, which yields an emission maximum centered at about 860 nm and a spectral bandwidth of 60 nm. When laser light sources are also used, especially in nephelometric instruments, the technique is commonly known as "laser nephelometry". The advantage of using laser nephelometers is the significant improvement in signal-to-noise ratio at very low detection levels. Usually the light source is a laser diode with a working wavelength at 660 nm. The high-power density of the laser beam gives rise to higher scattered intensity from smaller particles. Combined with a light trap, which absorbs the unscattered light, the system lowers the stray light significantly. When the use of a nephelometer or turbidimeter is indicated for a procedure in a monograph, instruments working in ratio mode may be used instead.
濁度也可以用標準光電濾光光度計或分光光度計測量，最好是在光譜的藍色部分進行照明。散射光濁度法測量需要一個裝有光電管的儀器，以便接收散射光，而不是透射光。由于這與熒光計中使用的幾何結構相同，因此可通過適當選擇濾光片將其用作濁度計。比率濁度計結合了90°散射光濁度法和透射光比濁法。它包含光電管，接收和測量與樣品成90°角的散射光，以及接收和測量樣品前面的前向散射光。它還測量直接穿過樣品的光。通過90°角散射光測量值，前向散射光測量值和透射光測量值之和，計算兩者的比值，可獲得線性度。使用比率濁度測量系統(tǒng)的好處是雜散光的測量變得可以忽略不計。此外，彩色懸浮液的濁度測定僅使用透射光比濁法濁度儀或濁度儀（帶比率模式）進行，因為該程序補償了懸浮液顏色導致的光衰減。通常，這些儀器中的光源是鎢燈，在2700 K的燈絲溫度下工作，大部分光強約為550 nm。也可使用其他合適的光源。通常，探測器是▲硅二極管▲和光電倍增管。另一種消除顏色效應的方法是使用紅外發(fā)光二極管作為光源，其最大發(fā)射中心約為860 nm，光譜帶寬為60 nm。當激光光源也被使用時，尤其是在濁度測量儀器中，這種技術通常被稱為“激光濁度測量”。使用激光散射光濁度計的優(yōu)點是，在非常低的檢測水平下，信噪比顯著提高。通常光源是工作波長為660 nm的激光二極管。激光束的高功率密度使較小粒子產生更高的散射強度。與吸收未散射光的光阱相結合，該系統(tǒng)可顯著降低雜散光。當專著中的某個程序指示使用散射光濁度計或透射光濁度計時，可以使用在比率模式下工作的儀器。
5. FORMAZIN TURBIDITY STANDARDS福爾馬肼濁度標準
Formazin is the only known primary turbidity standard. All other standards are secondary and must be traced to formazin. The primary standard is defined in the ▲IUPAC Compendium of Chemical Terminology,▲ (ERR 1-May-2019) 2nd ed. (the Gold Book) as one that is prepared by the user from traceable materials using well-defined methodologies and conditions.
福爾馬肼是唯yi已知的主要濁度標準。 所有其他標準都是次要的，必須追溯到福爾馬肼。 主要標準在▲IUPAC Compendium of Chemical Terminology▲（ERR 1-May-2019）第 2 版（金書）中被定義為由用戶使用明確定義的方法和條件從可追溯的材料準備的標準。
Formazin suspension has many features that ensure its suitability as a primary standard. It can be consistently and accurately prepared from reagent-grade starting materials. The suspension consists of random polymers with different lengths and of random configurations, which result in moieties of varying shapes and sizes ranging from less than 0.1 μm to more than 10 μm. Although the polymer chain length distribution has been shown to vary from preparation to preparation, the overall resulting turbidity has been very reproducible.
福爾馬肼懸浮液有許多特點，以確保其適合作為主要標準。它可以從試劑級的起始材料中始終如一、準確地制備。該懸浮液由不同長度和隨機構型的聚合物組成，其組成的聚合物的形狀和尺寸從小于0.1 μm到大于10 μm不等。盡管聚合物鏈長分布已被證明因制備而異，但總的濁度結果是可以很好地重現的。
5.1 Preparation of the Formazin Standards 福爾馬肼標準液的制備
[NOTE—All procedures described below must be performed at 20 ± 2° (see Volumetric Apparatus <31>.]
• Hydrazine sulfate solution: Dissolve 1.000 g of ACS grade hydrazine sulfate (N2H4·H2SO4) in particle-free water in a 100-mL Class A volumetric flask and dilute with particle-free water to volume. Allow this solution to stand for 4–6 h.
•Primary formazin standard: Dissolve 2.50 g of analytical grade hexamethylenetetramine [(CH2)6N4] in 25.0 mL of particle-free water in a 100-mL flask. Add 25.0 mL of hydrazine sulfate solution using a Class A 25-mL “to deliver” pipette and mix thoroughly. Allow the preparation to stand for 48 h at 25 ± 1° before using. The resulting suspension is stable for 2 months.
•Formazin stock standard suspension 1: Using a 15-mL Class A “to deliver” pipette, transfer 15 mL of the Primary formazin standard to a 1-L volumetric flask, and dilute with particle-free water to volume and mix. The resulting suspension has a turbidity of 60 NTU.
• Formazin stock standard suspension 2: Using a 50-mL Class A “to deliver” pipette, transfer 50 mL of Primary formazin standard to a 200-mL volumetric flask, and dilute with particle-free water to volume and mix. The resulting suspension has a turbidity of 1000 NTUs.
• Formazin reference suspensions: Prepare by mixing in a 100-mL volumetric flask, portions of the respective Formazin stock standard suspension and particle-free water according to Table 1.
[注：以下所有的程序必須在20±2°的條件下進行（參見<31 Volumetric Apparatus >）]
•硫酸肼溶液：將1.000 g ACS級硫酸肼（N2H4·H2SO4）溶解在100 mL 的A類容量瓶中中，并用無顆粒水稀釋至刻度。讓該溶液靜置4-6小時。
•初級福爾馬肼標準液：將2.50 g分析級六亞甲基四胺[(CH2)6N4]溶于25.0 mL無顆粒水中，裝入100 mL燒瓶。使用A類25ml移液管加入25.0 mL硫酸肼溶液，并充分混合。使用前，讓制劑在25±1°的溫度下靜置48小時。由此產生的懸浮液可穩(wěn)定運行2個月。
•福爾馬肼儲備標準懸浮液1：使用15 mL A類移液管，將15 mL福爾馬肼初級標準液轉移至1 L容量瓶中，并用無顆粒水稀釋至刻度并混合。所得懸浮液的濁度為60 NTU。
•福爾馬肼儲備標準懸浮液2：使用50 mL A類移液管，將50 mL福爾馬肼初級標準液轉移至200 mL容量瓶中，并用無顆粒水稀釋至刻度并混合。所得懸浮液的濁度為1000 NTU。
•福爾馬肼參考懸浮液：根據表1，在100 mL容量瓶中混合各份福爾馬肼儲備標準懸浮液和無顆粒水，制備福爾馬肼參考懸浮液。
6. QUALIFICATION OF TURBIDIMETERS AND NEPHELOMETERS 透射光式濁度儀與散射光式濁度儀的鑒定
The suitability of a specific instrument for a given procedure is ensured by a stepwise life cycle evaluation for the desired application from selection to instrument retirement. The qualification comprises three components: 1) installation qualification (IQ), 2) operational qualification (OQ), and 3) performance qualification (PQ) (see Analytical Instrument Qualification <1058>).
特定儀器對給定程序的適用性由從選擇到儀器報廢的預期應用的逐步生命周期評估來確保。鑒定包括三個部分：1）安裝鑒定（IQ）、2）操作鑒定（OQ）和3）性能鑒定（PQ）（參見<1058>Analytical Instrument Qualification章節(jié)）。
The purpose of this section is to provide test methods and acceptance criteria to ensure that the instrument is suitable for its intended use (OQ), and that it will continue to function properly over extended time periods (PQ). As with any spectrometric device, a turbidimetric and nephelometric spectrometer must be qualified for both wavelength (x-axis, if not fixed) and photometric (y-axis, or signal axis) accuracy and precision, and meet the requirements for the stray light. OQ is carried out across the operational ranges required within the laboratory for both the absorbance and wavelength scales.
本節(jié)的目的是提供測試方法和驗收標準，以確保儀器適合其預期用途（OQ），并在延長的時間段（PQ）內繼續(xù)正常工作。與任何光譜儀一樣，透射光式和散射光式濁度光譜儀必須具備波長（x軸，如果不固定）和光度（y軸或信號軸）的準確度及精度，并滿足雜散光的要求。OQ是在實驗室內吸光度和波長標度所需的操作范圍內進行的。
Acceptance criteria for critical instrument parameters that establish “fitness for purpose” are verified during IQ and OQ. Specifications for particular instruments and applications can vary depending on the analytical procedure used and the desired accuracy of the final result. Instrument vendors often have samples and test parameters available as part of the IQ/OQ package.
在IQ和OQ期間，驗證確定“用途適用性”的關鍵儀器參數的驗收標準。特定儀器和應用的規(guī)格可能因使用的分析程序和最終結果的預期準確度而異。儀器供應商通常將樣品和測試參數作為IQ/OQ包的一部分提供。
Wherever possible in the procedures detailed as follows, primary reference standards or certified reference materials (CRMs) are to be used. Formazin is the only primary reference standard used in turbidimetry and nephelometry. All the other standards, including the CRMs, must be correlated to formazin. The CRMs should be obtained from a recognized accredited source and include independently verified traceable value assignments with associated calculated uncertainty. CRMs must be kept clean and free from dust. Recertification should be performed periodically to maintain the validity of the certification.
在以下詳述的程序中，應盡可能使用主要參考標準或認證參考材料（CRM）。福爾馬肼是比濁法法和濁度法中唯yi使用的主要參考標準。所有其他標準，包括CRM，必須與福爾馬肼相關。CRM應從認可的認證來源獲得，并包括獨立驗證的可追溯值分配及相關的計算不確定性。CRM必須保持清潔，無灰塵。應定期進行重新認證，以保持認證的有效性。
6.1 Calibration校準
All of the turbidimetric and nephelometric instruments are calibrated against standards of known turbidity. The instrument must be calibrated using formazin turbidity standards prior to its first time use and at least every 3 months or as specified by the vendor. Calibration is performed using at least four formazin turbidity standards whose turbidity proportionally covers the range of interest. Many instrument manufactures provide calibration verification standards. They usually consist of sealed sample cells filled with a latex suspension or with metal oxide particles in polymer gel. These standards must be used only for checking the calibration in the time intervals between the instrument recommended calibrations.
所有透射光式濁度儀和散射光式濁度儀均根據已知濁度的標準進行校準。在首ci使用之前，必須使用福爾馬肼濁度標準液對儀器進行校準，至少每3個月或按照供應商的規(guī)定進行一次校準。使用至少四種福爾馬肼濁度標準液進行校準，其濁度按比例覆蓋感興趣的范圍。許多儀器制造商提供校準驗證標準。它們通常由其中充滿聚合物凝膠中的金屬氧化物顆粒的密封樣品池或乳膠懸浮液組成。這些標準只能用于檢查儀器推薦校準的時間間隔內的校準。
6.2 Stray Light雜散光
Stray light (stray radiant energy) is a very significant error source, especially for measurements in the range of the lower turbidity readings. It is defined as external light that reaches the detector without being scattered from the sample. There are several sources of stray light including the inherent cell surface imperfections, reflections from within the cell that are unaccounted for, optical system parts, light sources, and, to a smaller degree, the electronics fluctuations. Although there are many design features that instrument vendors use to minimize the stray light, a complete mitigation of the stray light cannot be achieved. Unlike spectrophotometric measurements, the stray light cannot be compensated for in turbidimetry. The stray light must be measured and the values should be within the specification range set by the vendor of the particular instrument or <0.15 NTUs for the measurement in the range of 0–10 NTUs and 0.5 NTUs for the measurements in the range of 10– 1100 NTUs, whichever is smaller.
雜散光(雜散光輻射能)是一個非常重要的誤差源，特別是在較低的濁度讀數范圍內的測量。它被定義為到達探測器而不被樣品散射的外部光線。雜散光有幾種來源，包括電池表面固有缺陷、電池內部未被解釋的反射、光學系統(tǒng)部件、光源，以及在較小程度上的電子波動。盡管儀器供應商使用了許多設計功能來最小化雜散光，但無法*緩解雜散光。與分光光度測量不同，濁度法無法補償雜散光。必須測量雜散光，其值應在特定儀器供應商設定的規(guī)格范圍內，或在0-10 NTU范圍內測量時小于0.15 NTU，在10-1100 NTU范圍內測量時小于0.5 NTU，以較小者為準。
6.3 Range of Measuring Capability測量能力的范圍
The instrument must be able to measure the turbidity in the range of 0.01–1100 NTUs or from 50%–200% of the target turbidity. To demonstrate the linearity for the intended measurements range, choose at least four appropriate reference suspensions from Table 1.
儀器必須能夠測量0.01–1100 NTU范圍內或目標濁度50%-200%范圍內的濁度。為了證明預期測量范圍的線性，從表1中選擇至少四種合適的參考懸浮液。
6.4 Resolution 解決方案
Instrument resolution must be 0.01 NTU or less for the measurements range of 0–9.99 NTUs; 0.1 NTU or less for the measurements range of 10–99.9 NTUs; and 1 NTU for the measurements above 100 NTUs.
對于0-9.99 NTU的測量范圍，儀器分辨率必須小于等于0.01 NTU；測量范圍為10-99.9 NTU時，小于等于0.1 NTU；100 NTU以上的測量分辨率值為1 NTU。
6.5 Accuracy準確度
The instrument reading accuracy must be ±10% of the reading + 0.01 NTU for the measurement range from 0–19.9 NTUs, and ±7.5% of the reading for the measurement range from 20–1100 NTUs.
對于0-19.9 NTU的測量范圍，儀器讀數準確度必須為讀數+0.01 NTU的±10%，對于20-1100 NTU的測量范圍，儀器讀數準確度必須為讀數的±7.5%。
6.6 Performance Qualification性能鑒定
The instrument PQ is accomplished periodically or as needed between the calibrations. Primary turbidity standards (formazin) or secondary calibration verification standards (latex suspensions or metal oxide particles in polymer gels contained in sealed sample cells) supplied by instrument manufacturers may be used.
定期或根據需要在校準期之間完成儀器PQ。可使用儀器制造商提供的一級濁度標準（福爾馬肼）或二級校準驗證標準（乳膠懸浮液或密封樣品池中聚合物凝膠中的金屬氧化物顆粒）。
7. PROCEDURE步驟
7.1 Turbidimetric Procedures 透射光比濁法測試步驟
SAMPLE CELL PREPARATION 樣品池準備
The sample cells for sample measurements must be clean. Follow the sample cell or instrument manufacturer recommendations for cleaning the sample cells appropriately. For low turbidity measurements it is a good practice to use a single-indexed sample cell or a flow cell, which help ensure adequate precision and repeatability of the measurements. Using particle-free water, find the sample cell orientation in the sample cell holder that gives the lowest reading. For higher values of turbidity, different sample cells may be used. However, the sample cells must be matched (the difference in readings for a standard prepared at nominal sample concentration from two different sample cells must be within ±0.005 NTU or below the measurement precision requirement, whichever is lower).
用于樣品測量的樣品室必須清潔。按照樣品池或儀器制造商的建議適當清潔樣品池。對于低濁度測量，最好使用一個單指數樣品池或流動池，這有助于確保測量的足夠精度和可重復性。使用無顆粒水，在樣品池支架中找到讀數最di的樣品池方向。對于較高的濁度值，可使用不同的樣品池。然而，樣品池必須匹配（兩個不同樣品池在標稱樣品濃度下制備的標準品讀數差異必須在±0.005 NTU范圍內或低于測量精度要求，以較低者為準）。
SAMPLE PREPARATION樣品準備
Prepare the samples as prescribed in the individual monograph. Carefully mix the samples thoroughly by swirling or inverting the volumetric flask slowly several times. Avoid shaking or stirring since it may introduce bubbles. Degassing the samples helps to improve the measurements. For degassing, the samples could stand for several minutes or a vacuum could be applied, or they could be gently sonicated using an ultrasonic bath. After degassing, let the samples stand for several minutes and mix again by carefully inverting two to three times. Transfer the sample to the sample cell and take the readings.
按照各專題中的規(guī)定制備樣品。通過緩慢旋轉或倒置容量瓶數次，仔細混合樣品。避免搖晃或攪拌，因為這可能會產生氣泡。對樣品進行脫氣有助于改進測量。對于脫氣，樣品可以靜置幾分鐘，或者可以施加真空，或者可以使用超聲波浴對其進行輕輕的超聲波處理。脫氣后，讓樣品靜置幾分鐘，然后小心地反轉兩到三次，再次混合。將樣品轉移至樣品池并讀取讀數。
USE OF FLOW CELLS流動池的使用
Flow cells are mainly used for low turbidity measurements for samples with small particles. When such cells are used, the sample is introduced by carefully pouring it down the interior edge of the inlet reservoir.
In practice, it is advisable to ensure that settling of the particles being measured is negligible. This is usually accomplished by including a protective colloid in the liquid-suspending medium. It is important that results be interpreted by a comparison of readings with those representing known concentrations of suspended matter, produced under precisely the same conditions.
流動池主要用于小顆粒樣品的低濁度測量。當使用這種樣品池時，通過小心地將樣品倒入進水倉的內邊緣來引入樣品。
在實際過程中，建議確保被測顆粒的沉降可以忽略不計。這通常通過在液體懸浮介質中加入保護膠體來實現。重要的是，通過將讀數與在*相同的條件下產生的已知懸浮物濃度的讀數進行比較來解釋結果。
7.2 Nephelometric Procedures散射光濁度法步驟
Nephelometric procedures are performed similarly to turbidimetric procedures for both direct measurements and measurements in the ratio mode as described above.
散射光濁度法步驟的執(zhí)行方式與透射光比濁法程序類似，適用于直接測量和上述比率模式下的測量。
RATE NEPHELOMETRIC PROCEDURES比率模式散射光濁度法步驟
The overall procedure for monitoring the progress of the reaction consists of three well-defined steps: 1) record a baseline reading of the turbidity of the medium (blank); 2) record the turbidity after the first reagent (antigen) is added, which results in an increase of the turbidity until a plateau is reached; and 3) add the second reagent (antibody), which results in another turbidity increase and a second plateau followed by a final turbidity increase that continues until a third plateau is reached. The measurement zone is selected from the addition of the antibody until the third plateau, depending on the purpose of the assay and the respective component concentrations. Kinetic nephelometry and Endpoint nephelometry are two general procedures that are used for quantifying the immune complexes formed in the immunoassay methods (also known as immunonephelometry because the measured turbidity is due to immunocomplexes that are formed). For each procedure, there are several parameters that need to be optimized in each individual application. The main parameters are 1) with or without particle enhancement; 2) particle types, sizes, and respective optimum wavelength, if applicable; 3) monitoring reaction kinetic or endpoint; 4) antibody/antigen under consideration and, related to that, the optimum level of antigen loading; 5) buffers and other ionic species and respective optimal pH; 6) type and concentration of polymers used to modify the solubility of proteins; and 7) temperature and other environmental factors. Generally these parameters are optimized during the method development and the values are given in specific monograph(s) and/or chapter(s) as applicable.
監(jiān)測反應進程的總體程序包括三個明確定義的步驟：1）記錄介質濁度的基線讀數（空白）；2） 在添加一種試劑（抗原）后，記錄濁度，這會導致濁度增加，直到達到一個穩(wěn)定期；3）添加第二種試劑（抗體），這會導致另一個濁度增加和第二個穩(wěn)定期，然后是最終濁度增加，直到達到第三個穩(wěn)定器。根據分析目的和各自的組分濃度，從添加抗體到第三個穩(wěn)定期中間選擇測量區(qū)。動力學散射比濁法和終點散射比濁法是兩種通用程序，用于量化免疫分析方法中形成的免疫復合物（也稱為免疫散射比濁法，因為測得的濁度是由形成的免疫復合物引起的）。對于每一個步驟，都有幾個參數需要在每個單獨的應用中進行優(yōu)化。主要參數為1）有無粒子增強；2） 顆粒類型、尺寸和各自的最佳波長（如適用）；3） 監(jiān)測反應動力學或終點；4） 考慮中的抗體/抗原，以及與之相關的抗原負載的最佳水平；5） 緩沖液和其他離子種類以及各自的最佳pH值；6） 用于改變蛋白質溶解度的聚合物的類型和濃度；7）溫度和其他環(huán)境因素。通常，這些參數在方法開發(fā)過程中進行了優(yōu)化，具體的專著和/或章節(jié)（如適用）中給出了這些值。
Kinetic nephelometry: The kinetic nephelometry is advantageous compared to the endpoint nephelometry mainly because of the capability to take a sample blank reading in addition to a reagent blank reading. This procedure assesses the rate of the immunocomplex formation based on the increased intensity response of the scattered light of the chosen wavelength. The reaction kinetic may be monitored continuously or a certain number of data points may be taken, depending on the time response of the instrument used and the type of application. At times it may involve only two data points; however, proper care must be exercised because the choice of point selection can influence the overall accuracy in cases where differences in reaction kinetics exist between samples and calibrating standards. Careful consideration should be given to the appropriate choice of specificity control strategy.
動力學散射比濁法：與終點散射比濁法相比，動力學散射比濁法具有優(yōu)勢，主要是因為除了試劑空白讀數外，還能夠讀取樣品空白讀數。該程序基于所選波長的散射光的增強強度響應來評估免疫復合物的形成速率。根據所用儀器的時間響應和應用類型，可連續(xù)監(jiān)測反應動力學，或采集一定數量的數據點。有時它可能只涉及兩個數據點；但是在樣品和校準標準之間存在反應動力學差異的情況下，選擇點可能會影響整體準確度。應仔細考慮特異性控制策略的適當選擇。
Endpoint nephelometry: In this method, an initial measurement is performed before adding the reagent, which represents the blank reading. A second measurement is performed after the immune complex is formed after approximately 60 min. The difference between these two measurements is proportional to the content of the component being assayed.
終點散射比濁法：在該方法中，在添加試劑之前進行初始測量，這代表空白讀數。大約60分鐘后，在免疫復合物形成后進行第二次測量。這兩次測量之間的差異與所分析成分的含量成正比。
8. VALIDATION AND VERIFICATION 驗證與核查
8.1 Validation 驗證
Validation is required when a nephelometric/turbidimetric method is intended for use as an alternative to the official procedure for testing an official article. The objective of nephelometric/turbidimetric method validation is to demonstrate that the measurement is suitable for its intended purpose, including quantitative determination of the main component in a drug substance or a drug product (Category I assays), quantitative determination of impurities or limit tests (Category II), and identification tests (Category IV). Depending on the category of the test (see Validation of Compendial Procedures <1225>, Table 2), the analytical method validation process for nephelometry/turbidimetry requires testing for accuracy, precision, specificity, detection limit (DL), quantitation limit (QL), linearity, range, and robustness. These analytical performance characteristics apply to externally standardized procedures and those that use standard additions.
當散射比濁法/透射濁度法擬用作官fang物品測試程序的替代方法時，需要進行驗證。當散射比濁法/透射濁度法驗證的目的是證明測量適用于其預期目的，包括原料藥或藥品中主要成分的定量測定（I類分析）、雜質的定量測定或限度試驗（II類）以及鑒定試驗（IV類）。根據試驗的類別（參見<1225>Validation of Compendial Procedures，表2），透射濁度法/散射比濁法的分析方法驗證過程需要對準確度、精密度、特異性、檢測限（DL）、定量限（QL）、線性、范圍和穩(wěn)健性進行試驗。這些分析性能特征適用于外部標準化程序和那些使用標準添加的程序。
Validation of Compendial Procedures <1225> provides definitions and general guidance on analytical procedures validation without indicating specific validation criteria for each characteristic. The intention of the following sections is to provide the user with specific validation criteria that represent the minimum expectations for this technology. For each particular application, tighter criteria may be needed in order to demonstrate suitability for the intended use.
<1225>Validation of Compendial Procedures章節(jié)提供了分析程序驗證的定義和一般指南，但沒有說明每個特征的具體驗證標準。以下各節(jié)的目的是向用戶提供具體的驗證標準，這些標準代表了對該技術的最di期望。對于每個特定應用，可能需要更嚴格的標準，以證明其適用于預期用途。
ACCURACY 準確度
For Category I, II, and III procedures, accuracy can be determined by conducting recovery studies with the appropriate matrix spiked with known concentrations of the analyte. Analysts can also compare the assay results obtained using the nephelometric/ turbidimetric procedure under validation to those from an established analytical procedure.
Validation criteria: 98.0%–102.0% mean recovery for the drug substances, 95.0%–105.0% mean recovery for the drug product assay, and 80.0%–120.0% mean recovery for the impurity analysis. These criteria are met throughout the specified range.
對于I類、II類和III類程序，可通過使用加入已知分析物濃度的適當基質進行回收研究來確定準確度。分析員還可以將使用驗證中的散射光濁度法/透射光比濁法程序獲得的分析結果與已建立的分析程序獲得的結果進行比較。
驗證標準：原料藥的平均回收率為98.0%–102.0%，藥品分析的平均回收率為95.0%–105.0%，雜質分析的平均回收率為80.0%–120.0%。這些標準在整個規(guī)定范圍內都得到滿足。
PRECISION精度
Repeatability: The repeatability of the analytical procedure is assessed by measuring the concentrations of six independently prepared sample solutions at of the assay test concentration. Alternatively, it can be assessed by measuring the concentrations of three replicates of three separate sample solutions at different concentrations. The three concentrations should be close enough so that the repeatability is constant across the concentration range. If this is done, the repeatability at the three concentrations is pooled for comparison to the acceptance criteria.
Validation criteria: The relative standard deviation is NMT 1.0% for the drug substance, NMT 2.0% for the drug product assay, and NMT 20.0% for the impurity analysis.
重復性：通過測量六種獨立制備的樣品溶液在分析試驗濃度下的濃度來評估分析程序的重復性?；蛘撸梢酝ㄟ^測量三種不同濃度的單獨樣品溶液的三個重復的濃度來評估。三種濃度應足夠接近，以便在整個濃度范圍內重復性保持恒定。如果這樣做，將三種濃度下的重復性匯總，以與驗收標準進行比較。
驗證標準：原料藥的相對標準偏差為NMT 1.0%，藥品分析的相對標準偏差為NMT 2.0%，雜質分析的相對標準偏差為NMT 20.0%。
Intermediate precision: The effect of random events on the analytical precision of the method must be established. Typical variables include performing the analysis on different days, using different instrumentation, and/or having the method performed by two or more analysts. At a minimum, any combination of at least two of these factors totaling six experiments will provide an estimation of intermediate precision.
Validation criteria: The relative standard deviation is NMT 1.5% for the drug substance, NMT 3.0% for the drug product assay, and NMT 25.0% for the impurity analysis.
中間精度：必須確定隨機事件對方法分析精度的影響。典型的變量包括在不同的日期使用不同的儀器進行分析，和/或由兩名或兩名以上的分析員進行分析。至少，這些因素中的至少兩個的組合，總共6個實驗，將提供中等精度的評估。
驗證標準：原料藥的相對標準偏差為NMT 1.5%，藥品分析的相對標準偏差為NMT 3.0%，雜質分析的相對標準偏差為NMT 25.0%。
SPECIFICITY 特異性
In nephelometric/turbidimetric measurements, specificity is demonstrated by the lack of interference from other components present in the matrix (other components of the matrix produce a true solution).
在散射光濁度法/透射光比濁法的濁度測量中，特異性通過基質中其他成分的干擾（基質的其他成分產生真實溶液）的缺乏來證明。
DETECTION LIMIT 檢測限
The DL can be estimated by calculating the concentration of a solution that would give the signal-to-noise ratio of ≥3.3. The estimated DL must be confirmed by analyzing samples at the calculated concentration.
可以通過計算溶液的濃度來估計檢測限DL，該濃度將給出信號的信噪比≥3.3. 必須通過分析計算濃度下的樣品來確認估計的DL。
QUANTITATION LIMIT 定量限
The QL can be estimated by calculating the concentration of a solution that would give the signal-to-noise ratio of ≥10.0. The estimated QL must be confirmed by analyzing samples at the calculated concentration. Measurement of a test solution prepared from a representative sample matrix spiked at the required QL concentration must be performed to confirm sufficient sensitivity and adequate precision. The observed signal-to-noise ratio at the required QL should be >10.
Validation criteria: For the estimated limit of quantitation to be considered valid, the measured concentration must be accurate and precise at a level ≤50% of the specification.
定量限QL可以通過計算溶液的濃度來估算，該濃度將給出信號的信噪比≥10.0. 必須通過分析計算濃度下的樣品來確認估算的QL。必須對以所需QL濃度添加的代表性樣品基質制備的試液進行測量，以確認其具有足夠的靈敏度和精度。在所需QL下觀察到的信噪比應大于10。
驗證標準:估計的定量限被認為是有效的，測量的濃度必須是準確的，并且在≤50%的規(guī)格水平上是精確的。
LINEARITY線性
A linear relationship between the analyte concentration and measured turbidity response must be demonstrated by preparation of at least four standard solutions at concentrations encompassing the anticipated concentration of the test solution. The standard curve is then evaluated using appropriate statistical methods such as a least-squares regression. Deviation from linearity results from instrumental or sample factors, or both, can be reduced to acceptable levels by reducing or increasing the analyte concentration, thereby respectively decreasing or increasing the turbidity readings to within the nephelometer/turbidimeter instrument linearity range.
Validation criteria: The correlation coefficient (R) must be NLT 0.995 for Category I assays and NLT 0.99 for Category II quantitative tests.
分析物濃度和測得的濁度響應之間的線性關系必須通過制備至少四種標準溶液來證明，其濃度包括試驗溶液的預期濃度。然后使用適當的統(tǒng)計方法（如最小二乘回歸）評估標準曲線。通過降低或增加分析物濃度，可將儀器或樣品因素或兩者的線性偏差降低至可接受水平，從而分別將濁度讀數降低或增加至透射光法濁度計/散射光濁度計儀器線性范圍內。
驗證標準：對于I類分析，相關系數（R）必須為NLT 0.995，對于II類定量測試，相關系數（R）必須為NLT 0.99。
RANGE 范圍
The operational range of an analytical instrument (and the analytical procedure as a whole) is the interval between the upper and lower concentrations (amounts) of analyte in the sample (including these concentrations) for which it has been demonstrated that the instrumental response function has a suitable level of precision, accuracy, and linearity.
Validation criteria: For Category I tests, the validation range for 100.0% centered acceptance criteria is 80.0%–120.0%. For non-centered acceptance criteria, the validation range is 10.0% below the lower limit to 10.0% above the upper limit. For Category II tests, the validation range covers 50.0%–120.0% of the acceptance criteria.
分析儀器（以及整個分析程序）的操作范圍是樣品中分析物的上下濃度（數量）（包括這些濃度）之間的間隔，已證明儀器響應函數具有適當的精度、準確度和線性水平。
驗證標準：對于I類試驗，100.0%中心驗收標準的驗證范圍為80.0%–120.0%。對于非中心驗收標準，驗證范圍為下限以下10.0%到上限以上10.0%。對于II類試驗，驗證范圍涵蓋驗收標準的50.0%–120.0%。
ROBUSTNESS穩(wěn)健性
The reliability of an analytical measurement is demonstrated by deliberate changes to experimental parameters. For nephelometry/turbidimetry this can include, for example, measuring the stability of the analyte under specified storage conditions, varying pH, and adding possible interfering species. Robustness is determined concurrently using a suitable design for the experimental procedure.
分析測量的可靠性通過有意改變實驗參數來證明。 對于散射光濁度法/透射光比濁法，這可以包括：測量分析物在特定儲存條件、變化的 pH 值和添加可能的干擾物質下的穩(wěn)定性。使用適合實驗程序的設計，同時確保穩(wěn)健性。
8.2 Verification核查
Current U.S. Good Manufacturing Practices regulations [21 CFR 211.194(a)(2)] indicate that users of analytical procedures described in the U.S. Pharmacopeia and National Formulary are not required to validate these procedures if provided in a monograph. Instead, they simply must verify their suitability under actual conditions of use.
現行的《美國生產規(guī)范條例》[21 CFR 211.194（a）（2）]表明，如果專論中提供了這些程序，則美國藥典和國家處方集中描述的分析程序的用戶無需驗證這些程序。相反，他們只需驗證其在實際使用條件下的適用性。
The objective of nephelometric/turbidimetric procedure verification is to demonstrate the suitability of a test procedure under actual conditions of use. Performance characteristics that verify the suitability of a nephelometric/turbidimetric procedure are similar to those required for any analytical procedure. A discussion of the applicable general principles is found in Verification of Compendial Procedures <1226>. Verification is usually performed using a reference material and a well-defined matrix. Verification of compendial nephelometric/turbidimetric procedures includes, at minimum, the execution of the validation parameters for specificity, accuracy, precision, and QL, when appropriate, as indicated in 8.1 Validation.
散射光濁度法/透射光比濁法程序驗證的目的是證明測試程序在實際使用條件下的適用性。驗證散射光濁度法/透射光比濁法程序適用性的性能特征與任何分析程序所需的性能特征相似。適用的一般原則的討論見<1226>Verification of Compendial Procedure 章節(jié)。通常使用參考材料和明確定義的基質進行驗證。 藥典散射光濁度法/透射光比濁法程序的驗證至少包括對特異性、準確度、精密度和 QL 的驗證參數的執(zhí)行（如 8.1 驗證中所述）。
Opalescence is the effect of light being absorbed or scattered by submicroscopic particles or optical density inhomogeneities. The absence of any particles or inhomogeneities in a solution results in a clear solution.
光被亞微觀粒子吸收或散射、或光密度不均勻的產生的效果即為乳光。溶液中不存在任何粒子或不均勻性，就會得到清澈的溶液。
A liquid is considered clear if its clarity is the same as that of water R or of the solvent used, or if its opalescence is not more pronounced than that of reference suspension I (see Table 2.2.1.-1), when examined under the conditions described below.
在下述條件下檢查時，如果液體的透明度與水或所用溶劑的透明度相同，或者其乳光不比參考懸浮液I（見表2.2.1.-1）的乳光更明顯，則認為液體是透明的。
Requirements in monographs are expressed in terms of the visual method by comparing with the defined reference suspensions (see Table 2.2.1.-1). However, instrumental methods may also be used for determining compliance with monograph requirements once the suitability of the instrument has been established as described below and calibration with reference suspensions I-IV and with water R or the solvent used has been performed.
通過與規(guī)定的參考懸浮液進行比較（見表2.2.1.-1），以目視法表達專著中的要求。然而，一旦儀器的適用性如下所述建立，儀器方法也可用于確定是否符合專論要求，并使用參考懸浮液I-IV和水或所用溶劑進行校準。
VISUAL METHOD目視法
Using identical test-tubes of colourless, transparent, neutral glass with a flat base and an internal diameter of 15-25 mm, compare the liquid to be examined with a reference suspension freshly prepared as described below. Ensure that the depths of the layers in the 2 test-tubes are the same (about 40 mm).
使用相同的無色透明中性玻璃試管，底座平坦，內徑為15-25 mm，將待檢液體與下述新制備的參考懸浮液進行比較。確保兩個試管中各層的深度相同（約40 mm）。
Compare the liquids in diffused daylight 5 min after preparation of the reference suspension, viewing vertically against a black background.
制備參考懸浮液5分鐘后，在漫射日光下比較液體，在黑色背景下垂直觀察。
System suitability. The diffusion of light must be such that reference suspension I can readily be distinguished from water R, and that reference suspension II can readily be distinguished from reference suspension I (see Table 2.2.1.-1).
系統(tǒng)適用性。光的擴散必須確保參考懸浮液I可以很容易地與水區(qū)分開，并且參考懸浮液II可以很容易地與參考懸浮液I區(qū)分開（見表2.2.1.-1）。
INSTRUMENTAL METHOD 儀器法
The instrumental assessment of clarity and opalescence provides a more discriminatory test that does not depend on the visual acuity of the analyst. Numerical results are more useful for process control and quality monitoring, especially in stability studies. For example, previous numerical data on stability can be extrapolated to determine whether a given batch of a preparation will exceed shelf-life limits prior to the expiry date.
儀器法評估給透明度和乳光度的提供了一種更具辨別力的測試，它不依賴于分析人員的視力。 數值結果對于過程控制和質量監(jiān)控更有用，尤其是在穩(wěn)定性研究中。 例如，可以從以前關于穩(wěn)定性的數字數據外推，來確定給定批次的制劑是否會在有效期之前超過保質期限制。
TURBIDIMETRY AND NEPHELOMETRY比濁法和濁度法
When a suspension is viewed at right angles to the direction of the incident light, the system appears opalescent due to the scattering of light by the particles of the suspension (Tyndall effect). A certain portion of the light beam entering a turbid liquid is transmitted, another portion is absorbed and the remaining portion is scattered by the suspended particles. The light-scattering effect of suspended particles can be measured either indirectly by observation of the transmitted light (turbidimetry) or directly by measuring the scattered light (nephelometry). Turbidimetry and nephelometry are more reliable in low turbidity ranges, where there is a linear relationship between turbidity values and detector signals. As the degree of turbidity increases, not all the particles are exposed to the incident light and the scattered or the transmitted radiation of other particles is hindered on its way to the detector.
當以與入射光方向成直角的角度觀察懸浮液時，由于懸浮液顆粒對光的散射（丁達爾效應），系統(tǒng)呈現乳白色。進入混濁液體的光束的一部分被透射，另一部分被吸收，其余部分被懸浮顆粒散射。懸浮顆粒的光散射效應可以通過觀察透射光（比濁法）間接測量，也可以通過測量散射光（濁度法）直接測量。比濁法和濁度法在低濁度范圍內更可靠，濁度值和檢測器信號之間存在線性關系。隨著濁度的增加，并非所有粒子都暴露在入射光下，其他粒子的散射或透射輻射在到達探測器的過程中會受到阻礙。
For quantitative measurements, the construction of calibration curves is essential. Linearity must be based on at least 4 levels of concentrations. Reference suspensions must show a sufficiently stable degree of turbidity and must be produced under well-defined conditions.
對于定量測量，校準曲線的構建至關重要。線性必須基于至少4個濃度水平。參考懸浮液必須顯示足夠穩(wěn)定的濁度，并且必須在明確的條件下產生。
MEASUREMENTS IN RATIO MODE比率模式下的測量
The determination of opalescence of coloured liquids is done using instruments with ratio mode, since colour provides a negative interference, attenuating both incident and scattered light and lowering the turbidity value. The effect is so great, even for moderately coloured samples, that conventional nephelometers cannot be used.
由于顏色會產生負干擾，衰減入射光和散射光，降低濁度值，因此使用具有比率模式的儀器測定有色液體的乳光。 這種影響是如此之大，即使是中等顏色的樣品，以至于不能使用傳統(tǒng)的濁度計。
In turbidimetry or nephelometry with ratio mode, the ratio of the transmission measurement to the 90° scattered light measurement is determined. This procedure compensates for the light that is diminished by the colour of the sample. Instruments with ratio mode use as light source a tungsten lamp with spectral sensitivity at about 550 nm operating at a filament colour temperature of 2700 K. Other suitable light sources may also be used. Silicon photodiodes and photomultipliers are commonly used as detectors and record changes in light scattered or transmitted by the sample. The light scattered at 90 ± 2.5° is measured by the primary detector. Other detectors measure back and forward scatter (reflected light) as well as transmitted light. The results are obtained by calculating the ratio of the 90° scattered light measured to the sum of the components of forward scattered and transmitted light values.
在比濁法或濁度法中，通過比率模式，確定透射測量與90°散射光測量的比率。該程序補償因樣品顏色而減弱的光線。具有比率模式的儀器使用光譜靈敏度約為550 nm的鎢燈作為光源，在2700 K的燈絲色溫下工作。也可以使用其他合適的光源。硅光電二極管和光電倍增管常用作探測器，記錄樣品散射或透射光的變化。由主探測器測量90±2.5°處的散射光。其他探測器測量前后散射（反射光）以及透射光。通過計算測得的90°散射光與前向散射光和透射光值分量之和的比值，可以獲得結果。
The instruments used are calibrated against standards of known turbidity and are capable of automatic measurement of turbidity. The test results are obtained directly from the instrument and compared to the specifications in the individual monograph.
使用的儀器根據已知濁度標準進行校準，并能夠自動測量濁度。測試結果直接從儀器中獲得，并與各專著中的規(guī)范進行比較。
Alternatively, the influence of the colour of the sample may also be eliminated by using an infrared light-emitting diode (IR LED) having an emission maximum at 860 nm with a 60 nm spectral bandwidth as the light source of the instrument.
或者，也可以通過使用最大發(fā)射波長為860nm、光譜帶寬為60nm的紅外發(fā)光二極管（IR LED）作為儀器光源來消除樣品顏色的影響。
INSTRUMENT REQUIREMENTS儀器要求
Instruments complying with the following characteristics and verified using reference suspensions as described below may be used instead of visual examination for determination of compliance with monograph requirements.
可使用符合以下特征并使用下述參考懸浮液驗證的儀器代替目視檢查，以確定是否符合專論要求。
– Measuring unit: NTU (nephelometric turbidity units). NTU is based on the turbidity of a primary standard of formazin. FTU (formazin turbidity units) or FNU (formazin nephelometric units) are also used, and are equivalent to NTU in regions of low turbidity (up to 40 NTU). These units are used in all 3 instrumental methods (nephelometry, turbidimetry and in ratio mode).
– Measuring range: 0.01-1100 NTU.
– Resolution: 0.01 NTU within the range 0-9.99 NTU; 0.1 NTU within the range 10.0-99.9 NTU; and 1 NTU for the range > 100 NTU.
– Accuracy: ± (10 per cent of reading + 0.01 NTU) with in the range 0-20 NTU; ± 7.5 per cent within the range 20-1100 NTU.
– Repeatability: ± 0.05 NTU within the range0-20 NTU; ± 2 per cent of the reading within the range 20-1100 NTU.
測量單位：NTU（濁度測量單位）。NTU是基于福爾馬肼一級標準品的濁度。也可使用FTU（福爾馬肼濁度單位）或FNU（福爾馬肼濁度單位），相當于NTU的在低濁度區(qū)域（最高40 NTU）。這些單位適用于所有3種儀器方法（比濁法、濁度法和比率模式）。
–測量范圍：0.01-1100 NTU
–分辨率：0-9.99 NTU范圍內為0.01 NTU；10.0-99.9 NTU范圍內為0.1 NTU；對于大于100 NTU的范圍，則為1 NTU
–準確度：范圍在0-20 NTU之間，讀數準確度偏差為±（讀數的10%+0.01 NTU）；范圍在20-1100 NTU時，讀數準確偏差為±7.5%。
–重復性：在0-20 NTU范圍內重復性為±0.05 NTU；在20-1100 NTU范圍內讀數重復性為±2%。
Instruments with measuring range or resolution, accuracy and repeatability capabilities other than those mentioned above may be used provided they are sufficiently validated and are capable for the intended use.
測量范圍或分辨率、精度和重復性能力不同于上述測量范圍或分辨率、精度和重復性能力的儀器經過有效驗證，也能夠應用于預期用途。
CONTROL OF INSTRUMENT PERFORMANCE儀器性能的控制
– Calibration: performed with at least 4 reference suspensions of formazin covering the measuring range of interest. Reference suspensions described in this chapter or suitable reference standards calibrated against the primary reference suspensions may be used.
–校準：使用至少4種福爾馬肼參考懸浮液進行校準，覆蓋感興趣的測量范圍?？墒褂帽菊滤龅膮⒖紤腋∫夯蚋鶕饕獏⒖紤腋∫盒实倪m當參考標準。
– Stray light: < 0.15 NTU within the range 0-10 NTU; < 0.5 NTU within the range 10-1100 NTU. Stray light is defined as that light that reaches the nephelometric detector without being a result of scatter from the sample. Stray light is always a positive interference and is a significant source of error in low-range turbidity measurements. Sources of stray light include: imperfections in and scratches on sample cells, internal reflections of the optical system, contamination of the optics or sample cell chamber with dust, and electronic noise. Instrument design can also affect stray light. The influence of stray light becomes negligible in ratio mode measurements.
雜散光：在0-10NTU范圍內<0.15 NTU；在10-1100 NTU范圍內<0.5 NTU。雜散光是指到達濁度檢測器的光，而不是樣品散射的結果。雜散光總是一種正干擾，是低范圍濁度測量中的一個重要誤差源。雜散光的來源包括：樣品池中的缺陷和劃痕、光學系統(tǒng)的內部反射、光學元件或樣品池被灰塵污染，以及電子噪聲。儀器設計也會影響雜散光。在比率模式測量中，雜散光的影響可以忽略不計。
The test methodology for the specific substance/product to be analysed must also be verified to demonstrate its analytical capability. The instrument and methodology shall be consistent with the attributes of the substance to be examined.
還必須驗證待分析特定物質/產品的試驗方法，以證明其分析能力。儀器和方法應與待檢物質的屬性一致。
Measurements of standards and samples should be carried out under the same temperature conditions, preferably between 20 °C and 25 °C.
標準品和樣品的測量應在相同的溫度條件下進行，最好在20 °C和25 °C之間。
REFERENCE SUSPENSIONS 參考懸浮液
Formazin has several desirable characteristics that make it an excellent turbidity standard. It can be reproducibly prepared from assayed raw materials. The physical characteristics make it a desirable light-scatter calibration standard. The formazin polymer consists of chains of different lengths, which fold into random configurations. This results in a wide variety of particle shapes and sizes, which allows the analysis of different particle sizes and shapes that are found in real samples. Stabilised formazin suspensions that can be used to prepare stable, diluted turbidity standards are commercially available and may be used after comparison with the standards prepared as described.
福爾馬肼有幾個理想的特性，使其成為一個優(yōu)秀的濁度液標準。它可以從經過分析的原材料中重復制備。其物理特性使其成為理想的光散射校準標準。福爾馬肼聚合物由不同長度的鏈組成，這些鏈折疊成隨機構型。這會產生各種各樣形狀和尺寸的顆粒，從而可以分析真實樣品中發(fā)現的不同顆粒大小和形狀?？捎糜谥苽浞€(wěn)定稀釋濁度標準品的穩(wěn)定福爾馬肼懸浮液是可商購的，并可在與所述制備的標準品進行比較后使用。
All steps of the preparation of reference suspensions as described below are carried out at 25 ± 3 °C.
下述參考懸浮液制備的所有步驟均在25±3°C下進行。
Hydrazine sulfate solution. Dissolve 1.0 g of hydrazine sulfate R in water R and dilute to 100.0 mL with the same solvent. Allow to stand for 4-6 h.
硫酸肼溶液。 將 1.0 g 硫酸肼溶解在水中，并用相同的溶劑稀釋至100.0 mL。 靜置 4-6 小時。
Primary opalescent suspension (formazin suspension). In a 100 mL ground-glass-stoppered flask, dissolve 2.5 g of hexamethylenetetramine R in 25.0 mL of water R. Add 25.0 mL of the hydrazine sulfate solution. Mix and allow to stand for 24 h. This suspension is stable for 2 months, provided it is stored in a glass container free from surface defects. The suspension must not adhere to the glass and must be mixed thoroughly before use.
初級乳白色懸浮液（福爾馬肼懸浮液）。在100 mL磨砂玻璃塞燒瓶中，將2.5g六亞甲基四胺溶解在25.0 mL水中。添加25.0 mL硫酸肼溶液?；旌喜㈧o置24小時。如果該懸浮液儲存在無表面缺陷的玻璃容器中，則可穩(wěn)定2個月。懸浮液不得粘附在玻璃上，使用前必須*混合。
Standard of opalescence. Dilute 15.0 mL of the primary opalescent suspension to 1000.0 mL with water R. This suspension is freshly prepared and may be stored for up to 24 h.
乳白色的標準濁度液。用水將15.0 mL初級乳白色懸浮液稀釋至1000.0 mL。該懸浮液是新制備的，可儲存24小時。
Reference suspensions. Prepare the reference suspensions according to Table 2.2.1.-1. Mix and shake before use.
參考懸浮液。根據表2.2.1-1制備參考懸浮液。使用前混合并搖勻。
Measurements of reference suspensions I-IV in ratio mode show a linear relationship between the concentrations and measured NTU values (see Table 2.2.1.-2).
在比率模式下，參考懸浮液I-IV的測量結果顯示，濃度與測量的NTU值之間存在線性關系（見表2.2.1.-2）。
Turbidity measurement is used to determine the turbidity (degree of opalescence) for the decision whether the article to be examined complies with the clarity requirement stated in the Purity.
As a rule, the visual method is specified for the requirement in individual monograph.
濁度測量用于確定濁度（乳光度），以決定待檢查的物品是否符合純度中規(guī)定的透明度要求。
作為一項規(guī)則，目視法是針對個別專論中的要求說明的。
1. Visual method目視法
This is used to determine the degree of opalescence with white (or faintly-colored) fine particles. So the degree of opalescence of a colored sample is liable to be determined lower that it is difficult to compare the degree correctly without using similarly colored reference suspension.
這是用來確定乳白色(或淡色)細顆粒的乳光程度。因此，有色樣品的乳光度容易被測定得較低，因此，如果不使用類似顏色的參考懸浮液，就很難正確地比較其乳光度。
1.1. Reference suspensions參考懸浮液
Pipet 5 mL, 10 mL, 30 mL and 50 mL of formazin opalescence standard solution, dilute them separately to exactly 100 mL with water, and use these solutions so obtained as Reference suspensions I, II, III and IV, respectively. Shake before use. Degrees of opalescence of Reference suspensions I, II, III and IV are equivalent to 3 NTU, 6 NTU, 18 NTU and 30 NTU, respectively.
用移液管分別吸取5 mL、10 mL、30 mL、50 mL福爾馬肼標準液，用水分別稀釋至100 mL，分別作為參比懸液I、II、III、IV。在使用前搖晃。參考懸浮液I、II、III和IV的乳光度分別相當于3 NTU、6 NTU、18 NTU和30 NTU。
1.2. Procedure步驟
Place sufficient of the test solution, water or the solvent to prepare the test solution and, where necessary, newly prepared Reference suspensions in separate flat-bottomed test tubes, 15 – 25 mm in inside diameter and of colorless and transparent, to a depth of 40 mm, and compare the contents of the tubes against a black background by viewing in diffused light down the vertical axes of the tubes. The diffused light must be such that Reference suspension I can be readily distinguished from water, and that Reference suspension II can readily be distinguished from Reference suspension I.
取足夠的待測溶液、水或溶劑，以準備測試溶液，必要時，將新制備的參考懸浮液置于獨立的平底試管中，試管內徑15 - 25mm，無色透明，深度40 mm。然后在一個黑色的背景下通過漫射光下垂直于管軸進行觀察，比較管內的內容。漫射光必須能使參考懸浮體I容易與水區(qū)分開來，參考懸浮體II容易與參考懸浮體I區(qū)分開來。
In this test Reference suspensions are used when the clarity of the test solution is obscurely and it is not easy to determine that its degree of opalescence is similar or not similar to water or to the solvent used to prepare the test solution.
在此測試中，當測試溶液的透明度模糊不清，并且不容易確定其乳光度與水或與用于制備測試溶液的溶劑是否相似時，使用參考懸浮液。
1.3. Interpretation注釋
A liquid is considered “clear” when its clarity is the same as that of water or of the solvent used to prepare the liquid or its turbidity is not more pronounced than that of Reference suspension I. If the turbidity of the liquid is more than that of Reference suspension I, consider as follows: When the turbidity is more than that of Reference suspension I but not more than that of Reference suspension II, express “it is not more than Reference suspension II”. In the same way, when the turbidity is more than that of Reference suspension II but not more than that of Reference suspension III, express “it is not more than Reference suspension III”, and when the turbidity is more than that of Reference suspension III but not more than that of Reference suspension IV, express “it is not more than Reference suspension IV”. When the turbidity is more than that of Reference suspension IV, express “it is more than Reference suspension IV”.
當液體的澄清度與水或與用于制備液體的溶劑的澄清度相同或其濁度不比參比懸浮液 I 更明顯時，該液體被視為“澄清”。如果液體的濁度大于參考懸浮液I，考慮如下：當濁度大于參考懸浮液I但不超過參考懸浮液II時，表示“不超過參考懸浮液II”。 同理，當濁度大于參比懸濁液Ⅱ但不大于參比懸濁液Ⅲ時，表示“不大于參比懸濁液Ⅲ”，當濁度大于參比懸濁液Ⅲ時 但不超過參考懸浮液IV，表示“不超過參考懸浮液IV”。 當濁度大于參考懸浮液IV時，表示“大于參考懸浮液IV”。
1.4. Reagent solutions試劑溶液
Formazin opalescence standard solution: To exactly 3 mL of formazin stock suspension add water to make exactly 200 mL. Use within 24 hours after preparation. Shake thoroughly before use. Degrees of opalescence of this standard solution is equivalent to 60 NTU.
福爾馬津乳光標準溶液：準確地取 3 mL福爾馬肼儲備懸浮液，加水至 200 mL。 配制后24小時內使用。使用前*搖勻。此標準溶液的乳光度相當于 60 NTU。
2. Photoelectric photometry光電光度法
The turbidity can also be estimated by instrumental measurement of the light absorbed or scattered on account of submicroscopic optical density inhomogeneities of opalescent solutions and suspensions. The photoelectric photometry is able to provide more objective determination than the visual method. Though they can determine the turbidity by measuring the scattered or transmitted light, the measuring system and light source must be specified in individual test method, and for the comparison of observed data, the same measuring system and light source should be used.
由于乳光溶液和懸浮液的亞顯微光密度不均勻性，還可以通過儀器測量吸收或散射的光來估計濁度。光電光度法比目測法能夠提供更客觀的測定。 雖然他們可以通過測量散射光或透射光來確定濁度，但必須在單獨的測試方法中標明測量系統(tǒng)和光源，并且為了比較觀察數據，應使用相同的測量系統(tǒng)和光源。
In each case, the linear relationship between turbidity and concentration must be demonstrated by constructing a calibration curve using at least 4 concentrations. For colored samples, the turbidity value is liable to be estimated lower because of attenuating both incident and scattered lights due to the absorption by the color, and the transmission-dispersion method is principally used.
在每種情況下，濁度和濃度之間的線性關系必須通過使用至少4種濃度構建校準曲線來證明。對于有顏色的樣品，由于顏色的吸收，入射光和散射光都被衰減，濁度值容易被估計得較低，主要采用透射-色散法。
2.1. Turbidimetry透射光比濁法
When a light passes through a turbid liquid the transmitted light is decreased by scattering with the particles dispersed in the liquid. A linear relationship is observed between turbidity and concentration when the particles with a constant size are uniformly dispersed, the size is small and the suspension is not higher concentration. The turbidity can be measured by Ultraviolet-visual Spectrophotometry <2.24> using spectrophotometer or photoelectric photometer. The turbidity of the sample in higher concentration can also be measured, however, it is susceptible to the color of the sample, and the measurement is usually performed at around 660 nm to avoid possible disturbance occurred from the absorption by the color.
當光通過混濁液體時，透射光通過分散在液體中的顆粒散射而減少。當粒徑恒定的顆粒分散均勻、粒徑較小且懸浮液濃度不高時，濁度與濃度呈線性關系。濁度可以通過紫外分光光度法<2.24>使用分光光度計或光電光度計進行測量。較高濃度的樣品的濁度也可以測量，但它易受樣品顏色的影響，通常在660 nm左右進行測量，以避免顏色吸收可能產生的干擾。
2.2. Nephelometry散射光濁度法
When a suspension is viewed at right angles to the direction of the incident light, it appears opalescent due to the refraction of light from the particles of the suspension (Tyndall effect). A certain portion of the light entering a turbid liquid is transmitted, another portion is absorbed and the remaining portion is scattered by the suspended particles. The scattered light measuring method shows the linear relationship between the nephelometric turbidity units (NTU) values and relative detector signals in a low turbidity range. As the degree of turbidity increases, not all the particles are exposed to the incident light and the scattered radiation of other particles is hindered on its way to the detector.
當懸浮物與入射光方向成直角時，由于懸浮物粒子的光線折射(丁達爾效應)，懸浮物呈現乳白色。進入混濁液體的光，一部分被透射，一部分被吸收，剩下的部分被懸浮的粒子散射。散射光測量方法顯示了低濁度范圍內散射濁度單位(NTU)值與相對檢測器信號之間的線性關系。隨著濁度的增加，并不是所有的粒子都暴露在入射光下，其他粒子的散射輻射在到達探測器的過程中會受到阻礙。
2.3. Ratio Turbidimetry比率濁度法
This method measures both scattered and transmitted light values at the same time, and the turbidity is determined from the ratio of the scattered light value to the transmitted light value. This procedure compensates for the light that is diminished by the color of the sample and eliminates the influence of the color. When the measurement is performed by using an integrating sphere, it is particularly called the integrating sphere method, which measures the total transmitted light value as well as the scattered light value occurred with the suspended particles, and the turbidity can be determined from the ratio of them.
該方法同時測量散射光值和透射光值，濁度由散射光值與透射光值的比值確定。此程序可補償因樣品顏色而減弱的光線，并消除顏色的影響。當用積分球進行測量時，特別稱為積分球法，它測量懸浮粒子的總透射光值和散射光值，由它們的比值可以確定濁度。
2.4. Application of photoelectric photometry for monograph requirements
光電光度法在專著要求中的應用
The turbidity of the test solution, determined by the photoelectric photometry, can be used as an indicating standard for the conformity to the clarity requirements by converting into NTU by using turbidity known reference solutions such as Reference suspensions I – IV, if needed, and water or the solvent used. In an automatically compensable apparatus being calibrated with turbidity known reference solutions, the measuring result is given in NTU and it can be compared directly with required specified value.
由光電光度法測定的測試溶液的濁度，可以作為指示標準，通過使用濁度已知的參考溶液，如參考懸浮液 I-IV，如果需要，水和使用的溶劑液也可以，將其以NTU為單位的數據轉出。在使用濁度已知參考溶液校準的自動補償裝置中，測量結果以 NTU 為單位給出，并且可以直接與所需的規(guī)定值進行比較。
NTU is often used as the unit in the turbidity determinations. It is the unit used in the case when the turbidity is estimated by the instrument which measures the 90 ± 30°scattered light against the incident light intensity, using tungsten lamp, and in the case the estimation is performed by the instrument which measures the 90 ± 2.5°scattered light against the incident light intensity using 860 nm infrared light, FNU is used as the unit. FNU is equivalent to NTU at a range of smaller measurements (less than 40 NTU). For the unit of formazin concentration, FTU is also used, which is defined as a suspension of 1 mg formazin in 1L of purified water is 1 FTU.
在濁度測定中經常使用NTU作為單位。它是測量用90±30°散射光對入射光強度的得到濁度信息時使用的單位，使用鎢燈，采用860 nm紅外光測量90±2.5°的散射光對入射光強度，此時以FNU為單元。在較小的測量范圍內(小于40 NTU)，FNU相當于NTU。福爾馬肼的濃度單位也用FTU，即1L純凈水中1 mg 福爾馬肼的懸浮液為1 FTU。
Formazin stock suspension. To 25 mL of hexamethylenetetramine TS add 25 mL of hydrazinium sulfate TS, mix, and use after allowing to stand at room temperature for 24 hours. Store in a glass container free from surface defects. Use within 2 months. Shake thoroughly before use. The turbidity of this suspension is equivalent to 4000 NTU.
福爾馬肼貯備懸浮液：向 25 mL六亞甲基四胺中加入25 mL硫酸肼，混勻，室溫靜置 24 小時后使用。 儲存在沒有表面缺陷的玻璃容器中。2個月內使用。使用前*搖勻。這種懸浮液的濁度相當于4000 NTU。
Formazin opalescence standard solution. To 15 mL of formazin stock suspension add water to make 1000 mL. Use within 24 hours after preparation. Shake thoroughly before use.
福爾馬肼標準液：向 15 mL 的福爾馬肼貯備懸浮液中加水至 1000 mL。配制后24小時內使用。使用前*搖勻。
上海胤煌科技針對藥劑的澄清度檢查推出了以下產品，符合各國藥典的溶液澄清度檢查規(guī)范。
1、澄清度檢查專用傘棚燈
HN-100A型和HN-200A型澄清度檢查專用傘棚燈符合各國藥典中目視法檢測溶液澄清度的儀器要求，具有光林帶型光源，能有效減少目視過程中光對眼睛的刺激，其照度可達5000 Lux。其中HN-200A型專用傘棚燈增加了RGB三色光源，可以對有色樣品進行澄清度檢測。
2、YH-CLS-1201澄清度檢查分析儀
此儀器采用全彩液晶觸摸屏進行操作控制，可以直接檢測注射用原料藥和注射劑的澄清度，并具備四級權限管理和審計追蹤功能，*GMP的數據完整性要求，是液體一致性評價的有效儀器。
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