Evaluation of Supercritical Fluid Extraction for Isotope Dilution Gas Chromatography-Mass Spectrometric Quantification of Polychlorinated Biphenyls in Sediment

Abstract

Polychlorinated biphenyls (PCBs) are representative persistent organic pollutants and suspected to be endocrine disrupters. Although PCBs have been removed from production and use in Japan since the early 1970s, they still remain in the environment. One of the major environmental sinks for PCBs is the sediment matrix, and thus the accurate quantification of trace PCBs in this matrix is important for evaluating their risk.In general, the quantification of PCBs in the sediment includes three analytical processes: the extraction of PCBs from the sediment, cleanup of the extracts, and analysis by gas chromatography (GC) with either mass spectrometry (MS) or electron-capture detection. The classical extraction methods, such as Soxhlet extraction 1,2 and saponification, followed by solvent extraction, 3 are usually applied as extraction techniques, but these methods are time-consuming and require a large amount of organic solvents. Supercritical fluid extraction (SFE) can possibly overcome these disadvantages. 4 A number of articles have appeared on the SFE of PCBs from sediments. Compared with Soxhlet extraction, SFE can provide a comparable or higher extraction efficiency. [5][6][7][8][9] However, the recovery yields of PCBs by SFE were significantly affected by various operating parameters, including the extraction temperature, [6][7][8][9][10][11][12][13] extraction pressure 8,9,12-14 and modifier addition. 8,9,[14][15][16][17] Therefore, optimization of the SFE conditions is very important for the accurate quantification of PCBs in sediments.Isotope dilution mass spectrometry (IDMS) has potential to be operated as a primary method of measurement. 18 Accurate quantification of PCBs may be expected when the IDMS technique is applied with GC-MS. However, equilibration between isotope-labeled compounds added as internal standards and native analytes in the sample is a prerequisite in the IDMS technique. The results from ID-GC-MS would show an incorrectly low amount of PCBs if equilibration is not achieved, as would occur if the quantitative extraction of analytes from a solid matrix is not achieved. 19Therefore, highly efficient extraction is required for the accurate quantification of PCBs in sediments, even if isotope-labeled PCB congeners are used as internal standards.The National Metrology Institute of Japan (NMIJ) has developed two kinds of marine sediment certified reference materials (CRMs) to be used for the validation of PCB quantification. [20][21][22] In the certification process, five kinds of independent extraction methods were applied for IDMS quantification to avoid any possible procedural bias. For that purpose, we developed four accurate extraction methods for PCBs in sediments in advance. We developed pressurized liquid extraction 23,24 and microwave-assisted extraction 25 as extraction techniques for the IDMS quantification. A method of saponification, followed by solvent extraction, was also optimized to give higher recovery yields of PCB congeners. 26SFE is another extraction technique we have d...

Immunoassay-based screening of polychlorinated biphenyls (PCB) in sediments: requirements for a new generation of test kits

“…Various techniques have been reported to optimize the solvent use and time in the PCB sediment extraction as well as the cleanup steps. The most widely applied techniques are Accelerated Solvent extraction (ASE), 25,33 Microwave Assisted Extraction (MAE), 34,35 Supercritical Fluid Extraction (SFE), 36,37 ultrasound assisted extraction (UE) 38,39 and Solid Phase Micro-extraction (SPME). 40,41 After extraction by using those systems quantification is normally performed by the classical GC approach, therefore reducing the total analysis time and solvent consumption but not the cost of analysis.…”

Determination of Polychlorinated Biphenyls in Solid Samples by Isotope Dilution Mass Spectrometry Using 37Cl-Labeled Analogues

“…The analysis of a solid sample requires the quantitative extraction of all target PCBs from the matrix. This has been carried out during the past years applying different extraction techniques such as Soxhlet, microwaves, sonication, supercritical fluid extraction (SFE), or pressurized liquid extraction (PLE). − Many of these techniques require long extraction times and/or high amounts of organic solvents and expensive laboratory glassware. Recently, focused microwave technology has been proposed as a rapid and efficient technique capable of providing quantitative extraction of organometallic compounds and Cr­(VI) in a few minutes using minimal amounts of sample and solvent.…”