EPA-OGWDW/TSC: 531.2: N-Methylcarbamoyloximes and N-Methylcarbamates in Water by HPLC with Post Column Derivitization
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Official Method Name
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Measurement of N-Methylcarbamoyloximes and N-Methylcarbamates in Water by Direct Aqueous Injection HPLC With Postcolumn Derivitization |
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Current Revision
| Revision 1.0, September 2001 |
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Media
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WATER |
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Instrumentation
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High Performance Chromatography with Post Column Derivitization and Fluorescence Detection |
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Method Subcategory
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Organic |
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Method Source
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Citation
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Brief Method Summary
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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. |
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Scope and Application
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Method is applicable to determination of certain N-methylcarbamoyloximes and N-methylcarbamates in finished drinking waters. |
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Applicable Concentration Range
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0.2-10 ug/L |
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Interferences
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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. |
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Quality Control Requirements
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Initial demonstration of accuracy (average recovery must be + or - 20% of true value), precision (RSD must be <20% ) and low system background are required. Calibration and continuing calibration checks (CCC) are required with a second source standard for the CCC and the Detection Limit must be determined over a 3 day period. A field duplicate (FD) and a Laboratory Fortified Sample Matrix (LFSM) and laboratory reagent blanks (LRB) are required with each analysis batch. Subtracting blank values from sample results is not permitted. |
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Sample Handling
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Amber 40 or 60 mL bottles with PTFE-lined screw caps are used for sample collection. Prior to sample collection potassium dihydrogen citrate is added as a dry solid in sufficient amounts to adjust the sample pH to about 3.8 in order to protect against degradation (especially of oxamyl, 3-hydroxycarbofuran, carbaryl, and methiocarb which hydrolyze in neutral or basic pH water). Also prior to sample collection sodium thiosulfate is added as a dry solid for a dechlorinating agent (especially for aldicarb and methiocarb which rapidly degrade in chlorinated water). Sample bottles thus must not be pre-rinsed before collection. Samples do not need to be collected free of headspace and must be kept cool, not exceeding 10 deg. C during the first 48 hours after collection. The laboratory must confirm receipt of samples at 10 deg. C. or below. |
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Maximum Holding Time
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28 days |
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Relative Cost
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$201 to $400 |
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Sample Preparation Methods
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