This is a gas chromatographic (GC) method applicable to the determination of certain chlorinated acids in ground water and finished drinking water. This method is also applicable to the determination of salts and esters of analyte acids. The form of each acid is not distinguished by this method. Results are calculated and reported for each listed analyte as the total free acid. A measured volume of sample of approximately 1 L is adjusted to pH 12 with 6 N sodium hydroxide and shaken for one hour to hydrolyze derivatives. Since many of the herbicides contained in this method are applied as a variety of esters and salts, it is vital to hydrolyze them to the parent acid prior to extraction. Extraneous organic material is removed by a solvent wash. The sample is acidified, and the chlorinated acids are extracted with ethyl ether by shaking in a separatory funnel or mechanical tumbling in a bottle. The acids are converted to their methyl esters using diazomethane as the derivatizing agent or alternatively, trimethylsilyldiazomethane (TMSD). Excess derivatizing reagent is removed, and the esters are determined by capillary column/GC using an electron capture detector (ECD). The method provides aa optional Florisil separation procedure to aid in the elimination of interferences that may be encountered.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | Most method analytes present in samples were stable for 14 days when stored in appropriate conditions. |
| Preservatives: | If residual chlorine is present, add 80 mg of sodium thiosulfate per liter of sample to the sample bottle prior to collecting the sample. The samples must be iced or refrigerated at 4°C away from light from the time of collection until extraction. |
| Required Preps: | Glass bottles |
| Collection Method: | Grab sampling |
| Analytical Methodology: | GC/ECD |
| Documentation: | 
515.1
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| 4-Nitrophenol | C6H5NO3 |
100-02-7 |
0.14 |
µg/L |
| Dichloroprop | C9H8Cl2O3 |
120-36-5 |
0.22 |
µg/L |
| Chloramben | C7H5Cl2NO2 |
133-90-4 |
0.097 |
µg/L |
| Dicamba | C8H6Cl2O3 |
1918-00-9 |
0.085 |
µg/L |
| Picloram | C6H3Cl3N2O2 |
1918-02-1 |
0.15 |
µg/L |
| Bentazon | C10H12N2O3S |
25057-89-0 |
0.11 |
µg/L |
| Acifluorfen | C14H7ClF3NO5 |
50594-66-6 |
0.026 |
µg/L |
| 3,5-Dichlorobenzoic acid | C7H4O2Cl2 |
51-36-5 |
0.065 |
µg/L |
| Dalapon | C3H4Cl2O2 |
75-99-0 |
1.3 |
µg/L |
| 5-Hydroxydicamba | C8H6Cl2O4 |
7600-50-2 |
0.017 |
µg/L |
| Pentachlorophenol | C6HCl5O |
87-86-5 |
0.032 |
µg/L |
| Dinoseb | C10H12N2O5 |
88-85-7 |
0.33 |
µg/L |
| 2,4,5-TP (Silvex) | C9H7Cl3O3 |
93-72-1 |
0.21 |
µg/L |
| 2,4,5-T | C8H5Cl3O3 |
93-76-5 |
0.045 |
µg/L |
| 2,4-D | C8H6Cl2O3 |
94-75-7 |
0.078 |
µg/L |
| 2,4-DB | C10H10Cl2O3 |
94-82-6 |
1.7 |
µg/L |
| DCPA Acid Metabolites | 0.067 |
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.