Method 515.1

Determination of Chlorinated Acids in Water by Gas Chromatography With an Electron Capture Detector


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.


(EPA: Office of Water)

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Method Data

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 List*

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.