Diluting Water Samples; Summary Of Method - Hach DR2400 Manual

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Diluting Water Samples

ALA_None_Other_IMM_Eng_Ody.fm

Other levels of Alachlor can be tested by diluting the sample and comparing the

results to the 0.1 ppb Calibrator. Select the appropriate sample volume from the

table below, place it in a graduated mixing cylinder, and dilute it to 50 mL with

deionized water.

Dilute 2.5 mL of sample to 50 mL with deionized water. Run the diluted sample

in the procedure along with the 0.1 ppb calibrator. If the absorbance of the

diluted sample is less than the 0.1 ppb calibrator, the concentration of the

original sample is greater than 2 ppb.

Hach immunoassay tests use antigen/antibody reactions to test for specific

organic compounds in water and soil. Alachlor-specific antibodies, attached to

the walls of plastic cuvettes, selectively bind and remove Alachlor from complex

sample matrices. A prepared sample and a reagent containing enzyme-conjugate

molecules (analyte molecules attached to molecules of an enzyme) are added to

the Antibody Cuvettes. During incubation, enzyme-conjugate molecules and

Alachlor compete for binding sites on the antibodies. Samples with higher levels

of analyte will have more antibody sites occupied by Alachlor and fewer

antibody sites occupied by the enzyme-conjugate molecules.

After incubation, the sample and unbound enzyme conjugate are washed from

the cuvette and a color-development reagent is added. The enzyme in the

conjugate catalyzes the development of color. Therefore, there is an inverse

relationship between color intensity and the amount of Alachlor in the sample.

The resulting color is then compared with a calibrator to determine whether the

Alachlor concentration in the sample is greater or less than the threshold levels.

Test results are measured at 450 nm.

Representative Concentration using

0.1 ppb Calibrator