Determination of the Sum of Short Chain Polychlorinated n‐Alkanes with a Chlorine Content of Between 49 and 67% in Water by GC‐ECNI‐MS and Quantification by Multiple Linear Regression

Abstract

This new approach for the quantification of the sum of short chain polychlorinated alkanes in mixtures (commonly abbreviated as SCCPs, where P stands for paraffin) with average chlorine contents between 49 and 67% and different C-number distributions is the background for ISO CD 12010, allowing standardized analysis according to the European water framework directive in unfiltered surface water, ground water, drinking water and waste water. A quantification method for the sum of short chain polychlorinated n-alkanes by GC-ECNI-MS (gas chromatography coupled with electron capture chemical ionization mass spectrometry), independent of the chlorine content and robust against changes in C-number distribution, was developed. This means that the very different response factors in GC-ECNI-MS, depending on the chlorine content, are no longer a problem for the analysis of SCCPs. Furthermore, problems with the selection of analytical standards due to batch dependent technical mixtures and different environmentally occurring mixtures can be overcome by using this robust method. The calibration was performed using synthetic mixtures mimicking a variety of different technically produced SCCP mixtures with average chlorine contents between 49 and 67% and different C-number distributions. By this means, the calibration is also traceable. The method was based on the integration of selected m/z value (mass/charge relation value) signals over the full retention range of the compounds. Quantification was performed using multiple linear regression calibration with two selected m/z signals, and verified with two other mass combinations. The selection of the m/z values used for quantification was carried out by means of an orthogonal calibration design. A stepwise procedure was utilized to produce the best quantification results, with the minimum number of quantification m/z signals, together with the minimization of potential interferences to be encountered in water analysis. The weighted sum of the peak areas of two m/z values, m/z 327 and 423, led to a sum determination which was applicable to the different SCCP mixtures most likely to be found in the aquatic environment. The problem with the very different response factors of the selected m/z values in GC-ECNI-MS, caused by the differing chlorine content of the SCCP mixtures, was overcome as well by forming the weighted sum of the two selected peak areas. The method was especially suitable for water analysis because of the low detection limit achieved by GC-ECNI-MS for chlorinated compounds.

Parameters optimization using experimental design for headspace solid phase micro-extraction analysis of short-chain chlorinated paraffins in waters under the European water framework directive

“…replicates. A c c e p t e d M a n u s c r i p t 33 [19,21] SPE with GC/ECNI-MS [20] DI-SPME with GC/ECNI-MS [20] SBSE with GC/ECD [23] HS-SPME with GC/ECNI-MS (this work) 0.05 (seawater) a n.r. : not reported b : LOD obtained by using DI-SPME coupled to GC/ECD c n.m.: not measured Table 4: Occurrences and concentration levels (ng.L -1 ) of SCCPs in south France aquatic environment.…”

“…Coefficient of determination (r 2 ) for the calibration curves are given in Table 3 and good correlation (r 2 ≥0.971) were obtained in the three matrices tested. Precision of the experimental procedure was evaluated by A c c e p t e d M a n u s c r i p t 19 calculating the relative standard deviation (RSD) at 1 µg.L -1 (see Table 3). The RSD values were as low as 1 to 9%…”

“…This is mainly due to the number of isomers (up to 7,000) of which this class of compounds consists [2], and the lack of pure solutions of individual SCCPs for calibration as well as the lack of matrix reference materials. Several approaches have been attempted [1,3,[16][17][18][19] and the studies mainly focused on the determination of SCCPs in sediment, sludge or biota. Due to their high hydrophobicity (Log K ow between 5.06 and 8.12) and their low water solubility (0.49 to 1260 µg.L -1 ) [1,3], SCCPs are indeed hardly detectable in water samples, even if obligatory in the track of the WFD.…”

Recent developments in capabilities for analysing chlorinated paraffins in environmental matrices: A review

“…A disadvantage of this method is the high amount of solvent required for extracting CPs. An LLE method using less solvent was reported by Geiß et al (2010), who extracted SCCPs from 1 L river water using only 10 mL of n-heptane. Reported LOD values for SCCPs, MCCPs and LCCPs were around 50-100 ng L À1 for all studies.…”

Quantification of short- and medium-chain chlorinated paraffins in environmental samples by gas chromatography quadrupole time-of-flight mass spectrometry

“…This technique is well-suited to routine analyses, and has been employed in our laboratory [7]. Recently, two-dimensional gas-chromatography (GC × GC) methods have also been applied to separate SCCPs [8,9], as have mathematical methods such as principal component analyses (PCA) and multiple linear regression [10][11][12]. Alternative methods include the determination of SCCPs by short-column GC/ECNI-MS [13], carbon skeleton reaction gas chromatography [14], and on-line dechlorination-hydrogenation of chlorinated paraffin mixtures using GC and GC/MS [15,16].…”