歐洲藥典：

Clarity and degree of opalescence of liquids

VISUAL METHOD一般方法

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, the depth of the layer being 40 mm. Compare the solutions in diffused daylight 5 min after preparation of the reference suspension, viewing vertically against a black background. 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.

在內(nèi)徑15～25mm，平底，無色、透明、中性玻璃管中，加入等量的供試溶液與濁度標準液，使液位的深度都為40mm，按如下所述方法進行比較。濁度標準液制備5分鐘后，以色散自然光照射濁度標準溶液和供試溶液，在黑色背景下從垂直方向觀察、比較澄清度或

渾濁程度。色散自然光必須較容易區(qū)分濁度標準溶液Ⅰ與水，濁度標準溶液Ⅱ與濁度標準溶液Ⅰ

A liquid is considered clear if its clarity is the same as that of water R or of the solvent used when examined under the conditions described above, or if its opalescence is not more pronounced than that of reference suspension I.

如果供試溶液的澄清、透明程度與水相同，或者與所用溶劑相同，或者其澄清度不超過Ⅰ號濁度標準溶液，那么可判定該溶液為澄清。

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.

***肼溶液：取1.0g***肼溶于水，加水稀釋至100.0ml，靜置4～6小時。

Hexamethylenetetramine solution. In a 100 mL ground-glass-stoppered flask, dissolve 2.5 g of hexamethylenetetramine R in 25.0 mL of water R.

烏洛托品（六亞甲基四胺）溶液 ：在100ml容量瓶中，以25.0ml水溶解2.5g烏洛托品。

Primary opalescent suspension (formazin suspension).

To the examethylenetetramine solution in the flask 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 well mixed before use.

濁度標準貯備液：在存放烏洛托品溶液的100ml容量瓶中，加25.0ml的***肼溶液。混合，靜置24小時，貯存在無表面要求的玻璃容器中，可在2個月內(nèi)使用。該濁度液不得黏附玻璃，用前必須充分搖勻。

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.

濁度標準原液：取濁度標準貯備液15ml，加水稀釋、定容至1000ml。該液臨用前制備，至多保存24小時。

Reference suspensions. Prepare the reference suspensions according to Table 2.2.1.-1. Mix and shake before use.

濁度標準液：由濁度標準原液與水按表1-1配制,即得。本液應(yīng)臨用前配制。

Table 1.-1

Turbidity standard. The formazin suspension prepared by mixing equal volumes of the hydrazine sulfate solution and the hexamethylenetetramine solution is defined as a 4000 NTU (nephelometric turbidity units) primary reference standard. Reference suspensions I, II, III and IV have values of 3 NTU, 6 NTU, 18 NTU and 30 NTU respectively. Stabilised formazin suspensions that can be used to prepare stable, diluted turbidity standards are available commercially and may be used after comparison with the standards prepared as described.

濁度標準：乳光懸濁貯備液[***肼溶液和烏洛托品（六亞甲基四胺）溶液以等量體積混合]定為4000NTU（比濁測定法的濁度單位）儲備液對照標準.濁度標準液I, II, III 和 IV相應(yīng)的NTU值分別是3 NTU, 6 NTU, 18 NTU 和 30 NTU。穩(wěn)定的乳光懸濁貯備液可用于稀釋制備濁度標準，具有現(xiàn)實的商業(yè)價值，也可以與上述的標準化制備進行較。

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 assay of particle shapes and sizes, which analytically fits the possibility of different particle sizes and shapes that are found in the real samples. Due to formazin’s reproducibility, scattering characteristics and traceability, instrument calibration algorithms and performance criteria are mostly based on this standard.

因福馬爾肼具有一些我們所希望的特性，所以它是一種非常優(yōu)良的濁度標準物。它可以從被測原料中反復(fù)制備。具有所想要的光閃射校正標準化的物理特性。福馬爾肼聚合物由不同長度的鏈組成，他們可以折成各種形狀，應(yīng)此可以分析不同大小和形狀的粒子。這一特性使得我們可以對現(xiàn)實樣品中所具有的不同大小及性狀的粒子進行測定。由于。福馬爾肼具有可重復(fù)性、光散射性、可描繪性、儀器校準可算和操作標準化的特性，使其成為了濁度標準物。

instrumental methods Introduction

儀器方法簡介

The degree of opalescence may also be determined by instrumental measurement of the light absorbed or scattered on account of submicroscopic optical density inhomogeneities of opalescent solutions and suspensions. 2 such techniques are nephelometry and turbidimetry. For turbidity measurement of coloured samples, ratio turbidimetry and nephelometry with ratio selection are used.

該儀器是根據(jù)渾濁液和懸濁液亞顯微鏡光密度的不均一性來測量光的吸收或光的散射，即散射測濁法和透射測濁法。對于有色樣品的濁度測試法，要用到比率透射比濁法和可選擇比率的散射比濁法。

The light scattering effect of suspended particles can be measured by observation of either the transmitted light (turbidimetry) or the scattered light (nephelometry). Ratio turbidimetry combines the principles of both nephelometry and turbidimetry. Turbidimetry and nephelometry are useful for the measurement of slightly opalescent suspensions. Reference suspensions produced under well-defined conditions must be used. For quantitative measurements, the construction of calibration curves is essential, since the relationship between the optical properties of the suspension and the concentration of the dispersed phase is at best semi-empirical.

通過投射光（投射比濁法）或散射光（散射比濁法）來測量混懸粒子的光散射效能。濁度比率結(jié)合了透射比濁法和散射比濁法二者的原理。透射比濁法和散射比濁法用于測量具有輕微乳光的混懸液。必須使用在精確的條件下制得的標準混懸液。因為混懸液的光學(xué)性質(zhì)與分散相的濃度之間的關(guān)系最多是一個半經(jīng)驗值，所以定量測定主要使用標準曲線法。

The determination of opalescence of colored liquids is done with ratio turbidimeters or nephelometers with ratio selection, since color provides a negative interference, attenuating both incident and scattered light and lowering the turbidity value. The effect is so great for even moderately colored samples that conventional nephelometers cannot be used.

因為溶液顏色會產(chǎn)生負干擾，衰減入射光和散射光并降低濁度值，用比率透射濁度法和可選擇比率的散射濁度法測定有色溶液的乳光。對于正好適度的有色樣品，效果非常好，以至于常規(guī)的濁度儀不再使用。

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 quality monitoring and process control, especially in stability studies. For example, previous numerical data on stability can be projected to determine whether a given batch of dosage formulation or active pharmaceutical ingredient will exceed shelf-life limits prior to the expiry date.

用儀器來判斷澄清度和乳光，試驗所提供的分辨能力更強，不再依靠分析者的視覺敏銳性來判斷。對于定性監(jiān)控和過程控制，特別是穩(wěn)定性研究，數(shù)字化結(jié)果更有用。例如，之前所得的關(guān)于穩(wěn)定性的數(shù)字化資料用于判斷一個給定批號的劑量成分或活***物組分是否超過了貯存期限或者沒過有效期。

Nephelometry

When a suspension is viewed at right angles to the direction of the incident light, the system appears opalescent due to the reflection of light from 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. If measurement is made at 90° to the light beam, the light scattered by the suspended particles can be used for the determination of their concentration, provided the number and size of particles influencing the scattering remain constant. The reference suspension must maintain a constant degree of turbidity and the sample and reference suspensions must be prepared under identical conditions. The Tyndall effect depends upon both the number of particles and their size. Nephelometric measurements are more reliable in low turbidity ranges, where there is a linear relationship between

nephelometric turbidity unit (NTU) values and relative detector signals. 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. The maximum nephelometric values at which reliable measurements can be made lie in the range of 1750-2000 NTU. Linearity must be demonstrated by constructing a calibration curve using at least 4 concentrations.

散射比濁法當混懸液在垂直于入射光的方向觀察，因混懸液粒子產(chǎn)生的反射，系統(tǒng)出現(xiàn)乳光 (丁達爾效應(yīng)).。進入一個渾濁液的光束，一部分被透過，一部分被吸收，剩余部分被懸濁粒子散射。如果在與光束90°的方向檢測，假如粒子數(shù)量和大小對散射的影響維持常數(shù)，可以用懸濁粒子的光散射來測定他們的濃度。照溶液的濁度必須保持不變，并且樣品和對照混懸液在一樣的條件下制備。丁達爾效應(yīng))依賴于粒子的大小和數(shù)量。在低濁度范圍，光散射濁度法更可靠，散射法濁度單位值和有關(guān)檢測器信號成線性。隨濁濁度的增加，不是所有的粒子都能暴露在入射光下的，并且在到達檢測器的途徑中，其他粒子的散射光被阻礙。一個可靠的測量所能測量的比較大散射濁度值是1750-2000 NTU。必須用至少4個濃度構(gòu)建標準曲線來證明線性。

Turbidimetry

The optical property expressed as turbidity is the interaction between light and suspended particles in liquid. This is an expression of the optical property that causes light to be scattered and absorbed rather than transmitted in a straight line through the sample. The quantity of solid material in suspension can be determined by the measurement of the transmitted light. A linear relationship between turbidity and concentration is obtained when the particle sizes are uniform and homogeneous in the suspension. This is true only in very dilute suspensions containing small particles. Linearity between turbidity and concentration must be established by constructing a calibration curve using at least 4 concentrations.

透射濁度法在液體中懸濁粒子和光之間存在相關(guān)性，這一光學(xué)特性表示為濁度。表示的是光在直線方向上發(fā)生的散射和吸收，而不是光直線通過樣品的透射光學(xué)特性，通過測量透射光來測定混懸液中固體物質(zhì)的量。當混懸液中粒子的大小均一且性質(zhì)相同，可獲得濁度和濃度之間的線性關(guān)系。僅僅在很稀的含有少量粒子的混懸液中，才可實現(xiàn)線性。必須使用至少4個濃度構(gòu)建標準曲線來證明濁度和濃度間呈線性。

Ratio Turbidimetry

In ratio turbidimetry the relationship 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. The influence of the colour of the sample may also be eliminated by using an infrared light-emitting diode (IR LED) at 860 nm as the light source of the instrument. The instrument’s photodiode detectors receive and measure scattered light at a 90° angle from the sample as well as measuring the forward scatter (light reflected) in front of the sample along with the measurement of light transmitted directly through the sample. The measuring results are given in NTU(ratio) and are obtained by calculating the ratio of the 90° angle scattered light measured to the sum of the components of forward scattered and transmitted light values. In ratio turbidimetry the influence of stray light becomes negligible. Nephelometers are used for measurements ofthedegreeofopalescenceof；比率透射比濁法測定的是******光的測量和90°方向上；

Table 2.2.1.-2

INSTRUMENTAL DETERMINATION OF OPALESCENCE

乳光的儀器測定

Requirements in monographs are expressed in terms of the visual examination method with the defined reference suspensions. Instrumental methods may also be used for determining compliance with monograph requirements once the suitability of the instrument as described below has been established and calibration with reference suspensions I-IV and with water R or the solvent used has been performed.

乳光的儀器測定在用準確的參比混懸液定義可見方法時已表明了要求。一旦后面所規(guī)定的建立了儀器的適應(yīng)性，并用參比混懸液I-IV和水或使用的溶劑進行校正，文中的方法也使用于儀器校正。

Apparatus. Ratio turbidimeters or nephelometers with selectable ratio application use as light source a tungsten lamp with spectral sensitivity at about 550 nm operating at a filament colour temperature of 2700 K, or IR LED having an emission maximum at 860 nm with a 60 nm spectral bandwidth. 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 detected by

the primary detector. Other detectors are those to detect back and forward scatter as well as transmitted light. The instruments used are calibrated against standards of known turbidity and are capable of automatic determination of turbidity. The test results expressed in NTU units are obtained directly from the instrument and compared to the specifications in the individual monographs.

儀器：使用可選擇的比率濁度計和濁度計時，用鎢燈作光源，在2700K的譜線標記溫度時，鎢燈在大約550nm處有特殊選擇性，或者用在860nm處有比較大發(fā)射并且有60nm光譜寬度的紅外發(fā)光二級管。也可以使用其他合適的光源。常用硅制光電二極管和光電倍增管作檢測器，并記錄因樣品產(chǎn)生的光散射或光透射的改變。主要檢測器檢測在90 ± 2.5°方向上的光散射。其他的檢測器檢測朝后和朝前的光散射，就像測光透射一樣。使用的儀器用已知濁度的標準溶液來校正，并能夠自動測定濁度。從儀器上直接獲得用NTU單位表示的測定結(jié)果，并且，在個別文中與規(guī)定進行比較。

Instruments complying with the following specifications are suitable.

根據(jù)后面的說明使用儀器

— Measuring units: NTU. NTU is based on the turbidity of a primary reference standard of formazin. FTU (Formazin Turbidity Units) or FNU (Formazin Nephelometry Units) are also used, and are equivalent to NTU in low regions (up to 40 NTU). These units are used in all 3 instrumental methods (nephelometry, turbidimetry and ratio turbidimetry).

— 測量單位：NTU，NTU根據(jù)的是福爾馬肼標準儲備液的濁度。液使用FTU（福爾馬肼濁度單位）或FNU（福爾馬肼散射測濁法單位）單位，在低濁度范圍內(nèi)等于NTU（大于40NTU）。這些單位在散射測濁法、濁度法、比率濁度法，三種儀器方法中均可使用。

— Measuring range: 0.01-1100 NTU.

— 測量范圍：0.01-1100NTU

— Resolution: 0.01 NTU within the range of 0-10 NTU, 0.1 NTU within the range of 10-100 NTU, and 1 NTU for the range > 100 NTU. The instrument is calibrated and controlled with reference standards of formazin.

— 分辨率：在0-10NTU范圍內(nèi)分辨率為0.01NTU，在10-100NTU范圍內(nèi)分辨率為 0.1NTU，在>100NTU范圍內(nèi)分辨率為1NTU。用福爾馬肼的參比標準校正和控制儀器。

— Accuracy: 0-10 NTU: ± (2 per cent of reading + 0.01) NTU. 10-1000 NTU: ± 5 percent.

— 精確度：0-10 NTU±（2%測量讀數(shù)+0.01）NTU，10-1000 NTU: ± 5%

— Repeatability: 0-10 NTU: ± 0.01 NTU. 10-1000 NTU: ± 2 per cent of the measured value.

— 重復(fù)性：0-10 NTU± 0.01 NTU，10-1000 NTU± 2%的測量值

— Calibration: with 4 reference suspensions of formazin in the range of interest.

Reference suspensions described in this chapter or suitable reference standards calibrated against the primary reference suspensions may be used.

— 校正：用在感興趣范圍內(nèi)的4中福爾馬肼參比混懸液?？梢杂冒幢菊乱?guī)定的參比混懸液或合適的相對于參比混懸液儲備液標有刻度的參比標準來校正。

— Stray light: this is a significant source of error in low level turbidimetric measurement;

stray light reaches the detector of an optical system, but does not come from the sample; < 0.15 NTU for the range 0-10 NTU, < 0.5 NTU for the range 10-1000 NTU. — 雜散光：在低水平的濁度測定中，雜散光是主要的誤差來源。雜散光就是能到達光學(xué)系

統(tǒng)的檢測器，但不是由于樣品而產(chǎn)生的光。0-10 NTU的范圍內(nèi)雜散光< 0.15 NTU，10-100NTU的范圍內(nèi)雜散光< 0.5 NTU。

Instruments complying with the above characteristics and verified using the reference suspensions described under Visual method may be used instead of visual examination for determination of compliance with monograph requirements.

符合上面的特性，并用在可見方法下規(guī)定的參比混懸液進行校正的儀器，在這范圍內(nèi)，這些儀器可替代可視檢查，這些檢查和文中要求一致。

Instruments with 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. The test methodology for the specific substance/product to be analysed must also be validated to demonstrate its analytical capability. The instrument and methodology should be consistent with the attributes of the product to be tested.

所提供的儀器的使用范圍、分辨率、準確度、重復(fù)性、容量及其它上面提到的參數(shù)，這些是十分有效的并能夠預(yù)期使用。對于分析特殊的物質(zhì)/產(chǎn)品，也必須進行試驗方法學(xué)驗證來說明其分析能力。儀器和方法學(xué)應(yīng)該和測試樣品的特性一致。