Energy and Environmental Research Center, University of North Dakota, Box 9018, Grand Forks, North Dakota 58202, USA.
Anal Chem. 2009 Aug 15;81(16):6936-43. doi: 10.1021/ac901001j.
Determining dissolved concentrations of polychlorinated biphenyls (PCBs) in sediment pore (interstitial) water with conventional solvent extraction methods is problematic because obtaining large (liter) quantities of pore water, separating it from the sediment, and removing the influence of colloids can be very difficult. However, solid-phase-microextraction (SPME) can achieve similar detection limits using milliliter water samples as achieved with organic solvent extraction requiring a liter of pore water. Five different SPME sorbents were evaluated for their ability to yield the best detection limits for di- to octachlorobiphenyl congeners, both with GC/ECD and with GC/MS (both positive ion EI and negative ion CI). SPME using the 7 microm PDMS fiber with GC/MS (positive ion EI) yielded the best combination of signal-to-noise and selectivity using a 30 min extraction, although ECD was also suitable. Pore water was obtained by centrifuging wet sediment followed by flocculation to remove colloids. Quantitative calibration was simplified by adding dichloro- to hexachlorobiphenyl internal standards chosen to be compatible with either ECD or MS detection. Calibration curves and relative response factors (including the SPME and GC steps) were determined for all 62 PCB congeners that are present in above-trace quantities in commercial Aroclors. Calibrations were linear (r(2) typically >0.995) from low pg/mL to ng/mL concentrations, with near zero intercepts. Detection limits for all individual PCB congeners ranged from <1 to 3 pg/mL using 1.5 mL water samples. Dissolved organic matter (DOM) had no measurable effect on dichloro- and trichlorobiphenyls, but did contain about 10 to 25% of the tetrachlorobiphenyls and up to 60% of the hexachlorobiphenyl congeners. Log DOC/water partitioning coefficients (log K(DOC)) ranged from 3.6 to 4.6 for 2,3,5,6-tetrachlorobiphenyl and from 4.2 to 5.5 for 3,3',4,4',5,5'-hexachlorobiphenyl.
用常规溶剂萃取方法测定沉积物孔隙（间隙）水中多氯联苯（PCBs）的溶解浓度存在问题，因为获得大量（升）孔隙水，将其与沉积物分离，并去除胶体的影响可能非常困难。然而，固相微萃取（SPME）可以使用毫升水样达到与需要 1 升孔隙水的有机溶剂萃取相同的检测限。评估了五种不同的 SPME 吸附剂，以确定其对二氯至八氯联苯同系物的最佳检测限的能力，同时使用 GC/ECD 和 GC/MS（正离子 EI 和负离子 CI）进行检测。使用 7 微米 PDMS 纤维进行 SPME 并用 GC/MS（正离子 EI）进行检测，在 30 分钟的萃取过程中获得了最佳的信噪比和选择性组合，尽管 ECD 也适用。通过离心湿沉积物然后絮凝去除胶体来获得孔隙水。通过添加二氯至六氯联苯内标物简化定量校准，这些内标物选择与 ECD 或 MS 检测兼容。确定了所有 62 种存在于商用 Aroclors 中痕量以上的 PCB 同系物的校准曲线和相对响应因子（包括 SPME 和 GC 步骤）。校准曲线在低 pg/mL 至 ng/mL 浓度范围内呈线性（r²通常>0.995），截距接近零。使用 1.5 毫升水样，所有单个 PCB 同系物的检测限均小于 1 至 3 pg/mL。溶解的有机物（DOM）对二氯和三氯联苯没有可测量的影响，但确实包含约 10%至 25%的四氯联苯和高达 60%的六氯联苯同系物。2,3,5,6-四氯联苯的 logDOC/水分配系数（log K(DOC)）范围为 3.6 至 4.6，3,3',4,4',5,5'-六氯联苯的 log K(DOC)范围为 4.2 至 5.5。
