An On-Line Solid Phase Extraction-Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Perfluoroalkyl Acids in Drinking and Surface Waters

Figure 3

Development of the on-line SPE method. (a) Effect of different elution gradients, “plug gradient” or “early gradient” compared with “unchanged gradient,” on the analyte peak height; injection of 5 mL of acidified aqueous standard at 200 ng/L. (b) Effect of the sample volume on the peak area; injection in “early gradient” mode of aqueous standard at 200 ng/L. (c) Extraction efficiency of the 5 mL on-line SPE injection volume; on-line SPE injection in “early gradient” mode of 5 mL of aqueous standard at 200 ng/L and direct injection of 25 μL of aqueous standard at 40 μg/L. (d) Effect of acidification of the sample on the peak area; injection in “early gradient” mode of aqueous standard at 200 ng/L.

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