BACKGROUNDInter-laboratory measurement results of total petroleum hydrocarbons (TPH) in soils determined by current Gas Chromatography-Flame Ionization Detector, are not comparable due to specified TPH ranges of alkanes and/or different calibration standards between laboratories.

OBJECTIVESTo establish a standardized calibration and quantitation method of TPH and to develop the adjacent-peak calibration and quantitation method (APCQM).

METHODSThe APCQM mainly includes:(1) defining TPH range as all compounds eluting between n-hexane and n-tetracontane; (2) division of TPHs into volatile petroleum hydrocarbons (VPH) and semivolatile petroleum hydrocarbons (SPH). Specify and calibrate procedure of TPH. Reference materials (RM) for VPH are 5 n-alkanes, from n-hexane to n-decane, whereas SPH RMs are 31 n-alkanes, from n-decane to n-tetracontane. Calibration equations of peak area and concentration of n-alkanes can be constructed by average response factor or linear regression methods; (3) quantitative concentrations of all target chromatographic peaks acquired by adjacent standard peak calibration; (4) calculation of the contents of n-alkanes, TPH and optional TPH fractions.

RESULTSUsing the normal calibration and quantitation method, TPH recoveries of laboratory fortified blanks and laboratory fortified sample matrices could be underestimated or overestimated by 10%. By using the APCQM the paradox in quality control processes was resolved, and thus reliable measurement results of TPH were obtained in laboratories.

CONCLUSIONSThe APCQM is applicable to standardization analysis of TPH fractions in environmental samples.