Michael Oehme

Comparison of three types of mass spectrometers for HPLC/MS analysis of perfluoroalkylated substances and fluorotelomer alcohols.

The performance of three different types of mass spectrometer (MS) coupled to high performance liquid chromatography (HPLC), was compared for trace analysis of perfluoroalkylated substances (PFAS) and fluorotelomer alcohols (FTOHs). An ion trap MS in the full-scan and product-ion mass spectrometry (MS2) mode, time-of-flight (ToF) high-resolution MS and quadrupole MS in the selected ion mode, as well as triple quadrupole tandem MS were tested. Electrospray ionisation in the negative-ion mode [ESI(–)] was best suited for all instruments and compounds. PFAS could only be separated by a buffered mobile phase, but the presence of buffer suppressed the ionisation of FTOHs. Therefore, two independent chromatographic methods were developed for the two compound classes. Mass spectra and product-ion spectra obtained by in-source and collision-induced dissociation fragmentation are discussed, including ion adduct formation. Product ion yields of PFAS were only in the range of 0.3 to 12%, independent of the applied MS instrument. Ion trap MS2 gave product ion yields of 20 to 62% for FTOHs, whereas only 4.1 to 5.8% were obtained by triple quadrupole tandem MS. Ion trap MS was best suited for qualitative analysis and structure elucidation of branched isomeric structures of PFAS. Providing typical detection limits of 5 ng injected in MS2 mode, it was not sensitive enough for selective trace amount quantification. ToF high-resolution MS was the only technique combining high selectivity and excellent sensitivity for PFAS analysis (detection limits of 2 to 10 pg), but lacked the possibilities of MS/MS. Triple-quadrupole tandem MS was the method of choice for quantification of FTOHs with detection limits in the low pg range. It is also well suited for the determination of PFAS, although its detection limits of 10 to 100 pg in tandem MS mode are about one order of magnitude higher than for ToF MS.

Sources and pathways of persistent polychlorinated pollutants to remote areas of the North Atlantic and levels in the marine food chain: a research update

A summary is given of research conducted by our laboratory since 1991 on the dispersion and pathways of persistent organochlorines (POCs) to remote regions of the Northern North Atlantic. This review includes data not previously published and an overall interpretation of our results. Levels of polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls and pesticides in marine mammals and sediments from these areas are presented and discussed. Special attention is given to the levels of polychlorinated bornanes (toxaphene), to date the most heavily used insecticide worldwide. Finally, temporal trends are presented.

Enantioselective Analysis of Organochlorine Pesticides in Herring and Seal from the Swedish Marine Environment

Abstract Factors influencing the changes of enantiomeric ratios (ERs) in herring ( Clupea harengus ), grey seal ( Halichoerus grypus ), harbour seal ( Phoca vitulina ) and ringed seal ( Phoca hispida ) collected along the Swedish coastline were studied by enantioselective high-resolution gas chromatography (HRGC). Three-year-old male and female herring individuals from different sampling sites were selected, whereas seal blubber and liver samples represented different species, sexes and geographical locations. Enantioselective analysis of α-hexachlorocyclohexane (α-HCH), chlordanes and chlordane metabolites were performed. In general, herring showed similar ERs within the Baltic Sea. Results indicate that species specific differences are important factors controlling the ERs of Baltic seals. Inverse ERs in seal blubber and liver, and a low deviation from the racemic ratio of some components in the liver, indicate that not only enantioselective degradation but also stereoselectivity of other processes are responsible for the changes of ERs in biota.

Toxaphene. Analysis and Environmental Fate of Congeners

Toxaphene is an organochlorine pesticide of complex composition. Several hundreds of components consisting mainly of polychlorinated bornanes are present in technical mixtures. This number is high but low in comparison to the theoretically possible number of congeners which exceeds 30,000. In the environment and particularly in higher organisms, most of the components of toxaphene are degraded, and only few are accumulated. A direct synthesis of individual polychlorinated bornanes is not possible. Nevertheless, more than 40 individual compounds were produced by partial synthesis and/or degradation combined with further isolation. Several of these polychlorinated bornanes have been used as external standards for the quantitation of toxaphene in environmental samples. This article summarizes recent results on the chemistry, characterization, and environmental fate of single toxaphene congeners.

Determination of enantiomer ratios of bornane congeners in biological samples using heart cut multidimensional gas chromatography

The enantiomeric ratios of the chlorinated bornanes, 2-exo, 5,5,9,9,10, 10-heptachlorobornane (B[20030]-(022)), 2-endo,3-exo,5-endo,6-exo,8, 8,10,10-octachlorobornane (B[12012]-(202), Parlar No. 26), 2-exo,3-endo,6-endo,8,9,10,10-heptachlorobornane (B[21001]-(112)), 2,2,5,5,9,9, 10,10-octachlorobornane (B[30030]-(022), Parlar No. 38), 2-endo,3-exo,5-endo6-exo,8,8,9,10,10-nonachlorobornane (B[12012]-(212), Parlar No. 50), and 2,2,5,5,8,9,9,10,10-nonachlorobornane (B[30030]-(122), Parlar No. 62) were determined in a hake liver (Merluccius merluccius) and in two whitebeaked dolphin blubber (Lagenorynchus albirostris) samples. The analysis was performed by heart-cut multidimensional gas chromatography using an electron capture detector (ECD). Ultra 2 (5%-phenyl-95%-methylsilicone) was used as stationary phase in the first column and enantioselectivity was obtained in the second column with a phase consisting of a mixture of OV-1701 and heptakis(2,3,6-O-tert- butyldimethylsilyl)-β-cyclodextrin (10 : 1). All reference standards were also tested on the enantioselective column alone. The comparison of the two systems showed that deviations of ±0.12 from the racemic enantiomer ratio can be observed for the single column due to co-eluting impurities which are present in the reference standards. In most of the heart-cut chromatograms of the biota samples about 15 peaks could be found, showing the importance of a multidimensional separation system for an interference-free quantification by ECD. In all biological samples a significant deviation from the racemic enantiomer ratio was found for B[30030]-(022) (Parlar No. 38) and for B[30030]-(122) (Parlar No. 62). This indicates that an enantioselective disposition of the congeners occurs. In addition, considerations are presented concerning the relationship between congener structure and enantiomeric disposition.

High-resolution gas chromatographic test for the characterisation of enantioselective separation of organochlorine compounds: Application to tert.-butyldimethylsilyl β-cyclodextrin

Capillaries based on tert.-butyldimethylsilylated β-cyclodextrin (TBDMS-CD) diluted in OV-1701 have gained increasing interest for the enantioselective separation of lipophilic polychlorinated pesticides. A modified test according to Schurig for chiral stationary phases was not suitable for testing TBDMS-CD due the lack of sufficiently lipophilic compounds. A test mixture was developed containing the chiral polychlorinated pesticides α-hexachlorocyclohexane, cis- and trans-chlordane, heptachlor-exo-epoxide and 2-exo,3-endo,5-exo,6-endo,8,8,9,10,10-nonachloro-bornane. They are especially sensitive to changes in the enantioselective properties of TBDMS-CD which is also frequently used for these compounds. Cis- and trans-chlordane with different enantiomer ratios facilitate the detection of changes of the enantiomer elution order. Test results of laboratory-made and commercial capillaries are presented showing the usefulness of the test to detect differences in the enantioselective behaviour such as changes in the elution order of enantiomers. Electrospray MS was used for the characterisation of TBDMS-CD. The analysed batches contained homologues with 7–10 TBDMS groups in a mixture of variable composition. This is assumed to be the reason for the observed differences.

Altitude profiles of total chlorinated paraffins in humus and spruce needles from the Alps (MONARPOP)

Chlorinated paraffins (CPs) are toxic, bioaccumulative, persistent, and ubiquitously present in the environment. CPs were analyzed in humus and needle samples, which were taken within the Monitoring Network in the Alpine Region for Persistent and other Organic Pollutants (MONARPOP) at sampling sites of 7 different altitude profiles in the Alps. Gas chromatography combined with electron ionization tandem mass spectrometry (EI-MS/MS) was used for the determination of total CPs (sum of short, medium and long chain CPs). CPs were found in all samples; the concentrations varied between 7 and 199 ng g(-1) dry weight (dw) and within 26 and 460 ng g(-1) dw in humus and needle samples, respectively. A clear vertical tendency within the individual altitude profiles could not be ascertained. Within all altitude profiles, elevated concentrations were observed in humus samples taken between 700 and 900 m and between 1300 and 1500 m. In the needle samples no similar correlation could be observed due to higher variation of the data.

Optimization of tandem columns for the isomer and enantiomer selective separation of toxaphenes

Abstract A tandem column system for the isomer and enantiomer selective separation of 18 toxaphenes was optimized by applying the theory of Purnell and Williams. Polymethylbiphenylsiloxane (OP) and heptakis(2,3,6- O-t -butyldimethylsilyl)-β-cyclodextrin (CD) dissolved in OV-1701 were used as stationary phases on the single columns. The isothermal separation required by the theory was modified by adding a steep temperature program rate ahead of the selected isothermal temperature to make it applicable to toxaphenes. This change had no influence on the predictability of the elution order by the theory. A length combination of 19 m CD plus 6 m of OP was most favorable. Details about the optimization process are given including the required precision of pressure measurements. A further temperature program optimization allowed separation of the most important congeners Parlar No. 26, 32, 50 and 62 on the tandem system without any interference from others isomers and enantiomers which are part of the commercial standard mixture containing 22 toxaphene congeners.

Development of a comprehensive analytical method for the determination of chlorinated paraffins in spruce needles applied in passive air sampling

Conifer needles are used for the monitoring of atmospheric persistent organic pollutants. The objective of the present study was to develop a method for the detection of airborne chlorinated paraffins (CPs) using spruce needles as a passive sampler. The method is based on liquid extraction of the cuticular wax layer followed by chromatographic fractionation and detection of CPs using two different GCMS techniques. Total CP concentrations (sum of short (SCCP), medium (MCCP) and long chain CPs (LCCP)) were determined by EI-MS/MS. SCCP and MCCP levels as well as congener group patterns (n-alkane chain length, chlorine content) could be evaluated using ECNI-LRMS. For the first time, data on environmental airborne CPs on spruce needles taken within the Monitoring Network in the Alpine Region for Persistent and other Organic Pollutants (MONARPOP) are presented providing evidence that spruce needles are a suitable passive sampling system for the monitoring of atmospheric CPs.

Enantiomer ratios, patterns and levels of toxaphene congeners in human milk from Germany.

High resolution gas chromatography (HRGC) coupled to quadrupole negative ion chemical ionization (NICI) mass spectrometry (MS) was used to investigate congener patterns, levels and enantiomer distribution of selected toxaphene congeners (#26, #41, #44, #50, #63, B7-1453) in human milk from Germany. #50 and #26 were the most abundant congeners. Furthermore, the identification of B7-1453, B8-1412, #41, #42, #44 and #63 was possible. Levels for the sum of #26, #41, #44 and #50 ranged from 7 to 24 microg kg(-1) milk fat and contributed between 2 and 9% to the total burden of investigated organochlorines such as selected compounds of the chlordane group, HCH, DDT and polychlorinated biphenyls (PCB). Capillaries coated with heptakis-(2,3,6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (TBDMS-CD) or octakis-(2,3,6-tri-O-ethyl)-gamma-cyclodextrin (TEG-CD) were used for the enantioselective separations. Enantiomer ratios (ER) and enantiomer fractions (EF) of the abundant toxaphene congeners #26 and #50 as well as of B7-1453, #41 and #63 were determined. Greatest deviations from a racemic composition in individual human milk samples were found for #41 (1.54-2.37), #50 (1.37-1.72) and #63 (0.53-0.71) whereas ERs for #26 were close to 1. Compared to wildlife biota such as fish and raptors ER changes were more pronounced in human milk but comparable to human adipose tissue.