NEPHELOMETRY AND TURBIDIMETRY

Turbidimetry and nephelometry are two related techniques in which an incident source of radiation is elastically scattered by a suspension of colloidal particles. In turbidimetry, the detector is placed in line with the radiation source, and the 

A method in which the decrease in transmitted radiation due to scattering is measured. 

A method in which the intensity of scattered radiation is measured at an angle of 90° to the source. 

Determining Concentration by Turbidimetry In turbidimetry the measured transmittance, T, is the ratio of the transmitted intensity of the source radiation, fy, to the intensity of source radiation transmitted by a blank, Iq. 

The relationship between transmittance and the concentration of the scattering particles is similar to that given by Beer s law 

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Turbidimetry and Nephelometry. In contrast to classical absorbance methods, immunoassay reactions frequently involve agglutination in which the optical scatter signal of the agglutinated particles is measured by turbidimetric or nephelometric means. The principles of light scattering as it relates to analytical methods is discussed in reference 6. 

Turbidimetry and nephelometry are methods used to measure scattered light. Their measurement has proven useful for the quantitation of serum proteins (see Chapters 9 and 20). 

The choice between turbidimetry and nephelometry depends on the application and the available instrumentation. Neph-eloraetry, however, sfill offers some advantage in sensitivity when measuring low-level antigen-antibody reactions. ... 

These two optical techniques are particularly applicable to methods measuring the precipitate formation in antigen antibody reactions (see Chapter 9). Turbidimetry is used in several chemistry immunoassay systems for therapeutic drug monitoring and specific protein assays. Details of turbidimetry and nephelometry are discussed in Chapter 3. 

Introduction Separation Methods Chromatographic Separations Gas Chromatography High-Performance Liquid Chromatography Basis for Spectral Methods Fluorometry Flame Photometry Atomic Absorption Spectroscopy Turbidimetry and Nephelometry Defining Terms References... 

Nephelometry is the measurement of turbidity by the direct evaluation of the degree of light scattering taking place in the medium. It is much more appropriate to media of lower turbidity in which the suspended particles are small. Turbidimetry and nephelometry can offer considerable time-saving advantages over gravimetric methods for the determination of particle concentrations, and are nondestructive techniques. 

Turbidimetry and nephelometry give no information on particle shape. However, if the principle of nephelometry is combined with time-dependent measurement, photon correlation spectroscopy can provide information on the shape of the scattering particle. This dynamic light scattering has become very important in colloid chemistry [197], [198],... 

The important related fields of emission spectroscopy (including flame photometry, fluorometry, spectroradiometry, and phosphorim-etry), turbidimetry and nephelometry, and color measurement and speciHcation are not discussed. All are worthy of separate treatment. 

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