Turbidity absorbance

Measure bacterial growth by increasing turbidity (absorbance)... 

Turbidity, Absorbance. As light is scattered, the transmitted light is diminished as it passes through a sol. Transmittance and absorbance are related by the equation... 

Turbidity has to be removed by filtration or, in case of minor turbidity signals, compensated by using differential spectrophotometers with the chemically imtreated water sample as reference. Correction of the results for a measured turbidity absorbance is another option. 

For precision measurements it is necessary to correct the absorbance of the sample for turbidity (even if samples have been filtered). This is done by adding the sulphanilamide reagent to 50 mL of the sample. It is necessary to do this because, for example, some of the turbidity may be caused by calcareous particles that are dissolved by the acid in the reagent and, thus, would not contribute any further to the turbidity. The turbidity absorbance (At) is measured using the same cuvette size as for the samples against ZW. 

Clarity of the solution. The solution must be free from precipitate if comparison is to be made with a clear standard. Turbidity scatters as well as absorbing the light. 

When a beam of light is intercepted by a turbid medium, part of the incident light is absorbed, part is directly reflected, and part is scattered. The attentuation produced is a function of the concn, particle size distribution and color of the suspension... 

For IR sensing, three transducer principles are standard classical transmission for (sufficiently) transparent samples, (diffuse) reflection for opaque samples, in particular solids and strongly turbid liquids and attenuated total reflection (ATR), in particular for strongly absorbing samples and fluids with varying amounts of suspended solids or gas bubbles. 

The relative absorbance E3/4 to characterize the turbidity in the supernatant liquid. 

Without polymer all absorbances increase with decreasing pH and with increasing salt concentration. This behaviour can be explained by the increased aggregation of the particles at low pH and at high salt concentration leading to a more turbid suspension. 

In the analysis of seawater, the only significant interference arises from turbidity caused by particles in the sample. Prior filtration of the sample is therefore necessary. For anoxic waters, however, sulfide concentrations over 2 pm were found to decrease the absorbance. This was overcome by adding an excess of either Cd2+ or Hg2+ to the sample [171,172],... 

Avigad and Milner224 used a turbidimetric method based on the measurement of residual turbidity caused by complexing the acid polysaccharide with such quaternary ammonium detergents as cetyl-pyridinium bromide. The activity unit was expressed as the amount of enzyme bringing about a decrease of absorbance at 400 nm of 0.01/min. 

The substance to be determined need not itself absorb whilst a degree of background absorbance or turbidity can be tolerated. 

Turbidity is caused by any solid material which is dissolved or suspended in a liquid. The intensity of light scattered by a sample is measured and compared with that measured for standard formazin suspensions, and expressed as nephelometric turbidity units (NTU). Colour is determined as the absorbance (measured spectrophotometrically at 400 nm) of the sample filtered through a 0.4S micron pore size membrane filter [12, 13]. 

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