ASTM D4059 Test Method forAnalysis of Polychlorinated Biphenyls in Insulating Liquids by Gas Chromatography
12. Procedure
12.1 Preparation - Equilibrate the chromatograph to the conditions recommended in Section 8. Clean all glassware and syringes by repeated rinsing in pesticide grade solvent. Ensure that a satisfactory level of cleanliness has been obtained by injecting aliquots of the solvent washings into the chromatograph. A solvent peak will be recorded, but the chromatogram should not contain any peaks with a retention time greater than 1 min.
12.2 Standardization - Use the standard solution of Aroclor(s) as prepared in 11.3 to obtain standard chromatograms. Measure and record values of the detector response, Ri(s), and calculate the values for Mi (11.4).
12.3 Sample Preparation - Weigh 0.1 to 0.2 gm of the test specimen into a volumetric flask and dilute to volume with solvent (9.3). Dilute the test specimen by a minimum solvent-to-sample ratio of 50:1. Record the weight, Wx g, of the test specimen. Record the total volume of the diluted test specimen, Vx, mL.
12.3.1 It may be necessary to further dilute specimens containing large amounts of PCB to ensure that the EC detector remains within its linear response range. Adjust the solvent-to-oil ratio for mineral oil test specimens to match the solvent-to-oil ratio of the standard. This can be done conveniently by using the stock oil-solvent solution in making further secondary dilutions.
12.3.2 Prior approximate analysis to estimate PCB content is helpful at this stage in deciding the appropriate dilution.
12.3.3 Alternatively, the volume, V, mL, and density, d (g/mL), of the test specimen may be measured and recorded. Measure the volume by a properly calibrated pipet or syringe. The density at room temperature of mineral oils in current use may be assumed to be 0.89 g/mL in routine analysis with a loss in accuracy of 2 to 3 %, at most. The typical density of silicone insulating liquid has been found to be 0.96 g/mL.
12.4 Removal of Interferences:
12.4.1 Adsorbent Treatment - Place approximately 0.25 g of adsorbent in a clean glass vial. Pour the solution prepared in 12.3 into the vial and seal the vial with the lined cup. Shake thoroughly. Allow the adsorbent to settle and decant the treated solution into a second vial. Use this solution for analysis.
12.4.2 Acid Treatment - Carefully place a volume of concentrated sulfuric acid approximately equal to one half of that of the diluted test specimen into a clean glass vial. Pour the solution prepared in 12.3 in the vial and seal the vial with the lined cap. Shake thoroughly. Allow the sulfuric acid phase to separate and settle and decant the upper sample phase into a second vial. Use this solution for analysis.
12.4.3 Acid treatment alone has been found to be effective for silicone test specimens and for most mineral oil test specimens. Machine shaking for 10 min, followed by standing for 15 min to allow the phases to separate in the vial is often adequate. Separation of the acid and test specimen can be enhanced by centrifuging. Treatment with adsorbent, alone or following treatment with acid, is effective in removal of interferences from some mineral oil test specimens. Interferences can also be removed by other treatments. Refer to Appendix X2.
12.5 GC Analysis - Inject 1 to 5 µL (nx) of the diluted sample into the chromatograph. Record the chromatogram at the same attenuation setting and chart speed as used in the standardization procedure. Additional dilutions may be necessary to bring the chromatogram on scale.
12.5.1 The volume vx for mineral oil test specimens should be the same as the volume vs used for calibration in 11.4, so that the EC detector responds to the same volume of oil with both injections.
