EPA Method 531.2

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EPA Method 531.2:
N-Methylcarbamoyloximes and N-Methylcarbamates in Water by HPLC with Post Column Derivitization. Official Name: Measurement of N-Methylcarbamoyloximes and N-Methylcarbamates in Water by Direct Aqueous Injection HPLC With Postcolumn Derivitization

A filtered water sample (up to 1.0 mL) is injected into a HPLC system equipped with a reversed phase (C-18) column. After elution from the column, the analytes are hydrolyzed in a postcolumn reaction with sodium hydroxide at 80-100 deg C. to form methyl amine. Methyl amine is reacted with o-phthalaldehyde (OPA) and 2-mercaptoethanol (or N,N-dimethyl-2-mercaptoethylamine) to form a highly fluorescent isoindole which is detected by a fluorescence detector. Analytes are quantitated using the external standard technique.

Method is applicable to determination of certain N-methylcarbamoyloximes and N-methylcarbamates in finished drinking waters.

EPA Web site for Analytical Methods for Drinking Water

Contamination: Interferences may be caused by contaminants, especially amines and ammonia, in solvents, reagents, glassware, and other sample processing apparatus that lead to discrete artifacts or elevated baselines. Samples or the analytical system may be contaminated from being handled with bare fingers. Clean glassware and test for contaminants by analyzing laboratory reagent blanks per the method.

QC Requirements:
Initial demonstration of accuracy (average recovery must be + or - 20% of true value), precision (RSD must be

Maximum Holding Time:
28 days



0.2-10 ug/L

Precision and accuracy were determined by analyzing seven replicates of fortified reagent water and a 1.0 mL injection volume (see Table 6 of the method), under the conditions specified in Table 1 of the method. Additional data are available in the method.

Detection Limits were determined by analyzing 7 replicate laboratory fortified blanks (LFB) at a concentration estimated to be near the Detection Limit over a 3 day period, using the Waters postcolumn carbamate system with the Waters model 474 detector (see Table 3 of the method). The procedure is similar to that found in 40 CFR 136, Appendix B, with the addition of a multi-day component.

Revision Number:
Revision 1.0, September 2001

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