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ANALYSIS OF PERFLUORINATED CARBOXYLIC ACIDS IN SOILS: DETECTION AND QUANTITATION ISSUES AT LOW CONCENTRATIONS
Citation:
WASHINGTON, J. W., J. J. ELLINGTON, T. JENKINS, AND J. J. EVANS. ANALYSIS OF PERFLUORINATED CARBOXYLIC ACIDS IN SOILS: DETECTION AND QUANTITATION ISSUES AT LOW CONCENTRATIONS. JOURNAL OF CHROMATOGRAPHY A. Elsevier Science Ltd, New York, NY, 1154(1-2):111-120, (2007).
Impact/Purpose:
The general goals of this research are to meet OPPT's need for data and information regarding the stability of TBPPs in soils. We plan to address these needs with a series of lab experiments in which FBPs are exposed to selected natural and amended soils. We anticipate that, as we learn about the general behavior of FBPs in soils, we will develop a protocol for testing FBPs in soils that has procedures similar to the guidelines described in OECD 307.
Description:
Methods were developed for the extraction from soil, identification, confirmation and quantitation by LC/MS/MS of trace levels of perfluorinated octanoic acid (PFOA), perfluorinated nonanoic acid (PFNA) and perfluorinated decanoic acid (PFDA). Whereas PFOA, PFNA and PFDA all can be quantitated using the method of standard additions, PFOA also can be quantitated less laboriously using 13C4-PFOA as a matrix internal standard. The impact of extract matrices on signal varied between soils and temporally during analytical runs rendering 13C4-PFOA unsuitable as a matrix internal standard for quantitating perfluorinated carboxylic acids (PFCAs) other than PFOA, which co-elutes with 13C4-PFOA. In fact, for soil extracts quantitation of PFCAs based on external calibrations proved about as accurate as use of matrix internal standards for target analytes that do not co-elute with the matrix internal standard. Also, 13C4-PFOA should be used carefully as a matrix internal standard for trace levels of PFOA because some 13C4-PFOA standards contain trace impurities of unlabelled PFOA. When the presence of PFCAs in soil extracts is being determined by LC/MS/MS, detection limits are best defined by statistical methods that quantify the significance of contrast between analytical signal and background noise using multiple analyses. Further, when developing a calibration of low concentrations using weighted regression, the central tendency of the calibration line is best fitted using graphical depictions of error. As the MDL for the transition-product quantitation ion is approached in LC/MS/MS, relatively weak signals of transition-product confirmation ions can be used as a rejection criterion by looking for anomalously high values of the ratio of the confirmation to the quantitation ion.