This is a high performance liquid chromatography (HPLC) method applicable to the determination of benzidines in municipal and industrial discharges as provided under 40 CFR Part 136.1. A measured volume of sample, approximately 1-L, is extracted with chloroform using liquid-liquid extractions in a separatory funnel. The chloroform extract is extracted with acid. The acid extract is then neutralized and extracted with chloroform. The final chloroform extract is exchanged to methanol while being concentrated using a rotary evaporator. The extract is mixed with buffer and separated by HPLC. The benzidine compounds are measured with an electrochemical detector.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | All samples must be extracted within seven days of collection. Extracts may be held up to seven days before analysis, if stored under an inert (oxidant free) atmosphere. The extract should be protected from light. |
| Preservatives: | All samples must be iced or refrigerated at 4°C and stored in the dark from the time of collection until extraction. If residual chlorine is present, add 80 mg of sodium thiosulfate per liter of sample and mix well. If 1,2- diphenylhydrazine is likely to be present, adjust the pH of the sample to 4.0 to prevent rearrangement to benzidine. |
| Required Preps: | Glass bottle |
| Collection Method: | Grab or composite sampling |
| Analytical Methodology: | HPLC with electrochemical detection. |
| Documentation: | 
605
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| 3,3'-Dichlorobenzidine | C12H10Cl2N2 |
91-94-1 |
0.13 |
µg/L |
| Benzidine | C12H12N2 |
92-87-5 |
0.08 |
µg/L |
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.