Determination of the "new" problem group chloroparaffins in sediments by HRGC-LRMS

Chloroparaffins (CPs) are complex mixtures of n-alkanes homologues with variable chain lengths
and chlorine contents consisting of several thousands of congeners, homologues, isomers and
enantiomers. Although chloroparaffins belong to chemicals of high volume production, little
attention has been paid to the analysis and environmental levels of these compounds in the last
decades. Short chain chloroparaffins have been included in several regulation programs worldwide
since studies demonstrated toxicity to aquatic organisms. However, environmental levels still
missing for a detailed risk assessment, especially for aquatic systems.
The aim of the work was to develop a method for the determination of short and medium chain
chloroparaffins in sediments. The clean-up should be as simple as possible and the detection carried
out by high resolution gas chromatography (HRGC) coupled to low resolution mass spectrometry
(LRMS). In total, three mass spectrometric methods were applied for the detection of
chloroparaffins in sediments using different ionization techniques (electron ionization (EI), electron
capture negative ionization (ECNI) and chloride attachment chemical ionization (CACI)). They
allowed to determine short (SCCP) and medium chain CP (MCCP) levels and patterns in sediments
from the North and Baltic Sea.
Soxhlet extraction was followed by a clean-up consisting of adsorption chromatography with silica
gel and Florisil®, which allowed the separation of CPs from other interfering organochlorines such
as polychlorinated biphenyls, toxaphene and DDT-related compounds.
At first, thirty three sediments from the North and Baltic Sea were investigated by EI-MS/MS.
Secondly, eight additional sediments from the Seine estuary, Tromsø and Hamburg harbour were
analysed as well as fifteen suspended particular matter samples from the rivers Rhine, Neckar, Elbe
and from the North Sea. EI-MS/MS allowed simultaneous determination of short, medium and long
chain chloroparaffins. Concentrations ranged between 5-355 ng/g dry weight (d.w.) for the North
Sea, 45-377 ng/g d.w. for the Baltic Sea, 70-156 ng/g d.w. for the Seine estuary and the harbours of
Tromsø and Hamburg as well as 127-669 ng/g d.w. for the samples from Rhine and Neckar.
The application of ECNI-MS and CACI-MS allowed the separate quantification of short and
medium chain chloroparaffins and of the homologue and congener group patterns. SCCP
concentrations ranged between 8-144 ng/g d.w. and MCCP between 23-407 ng/g d.w. in twenty
eight samples (ECNI-MS). The SCCP and MCCP content was determined in those samples
exceeding ca. 50 ng/g total CP. Below this level the quantities were too low for this differentiation
based on single formular and congener groups. MCCP levels were highest in all samples.
Differences in the CP patterns were obtained. Sea sediments were predominated by chlorinated doand
tridecanes and those from rivers, harbours and suspended particular matter samples by
chlorinated un- and dodecanes. No difference was observed between the MCCP patterns.
Concentrations obtained by CACI-MS were in the range of 13-128 ng/g d.w. for SCCP and between
36-303 ng/g d.w. for MCCP in eighteen sediments from the North and Baltic Sea. The
MCCP/SCCP ratios varied between 1.5 and 3.2 and were in good agreement (< 25% relative
deviation) with the same sampling location and different years of sample collection. Results
obtained by the three methods were in a good agreement with each other (< 34% relative standard
deviation).
Furthermore, principal component analysis (PCA) was applied to compare the CP patterns of
sediments and suspended particular matter with those of technical mixtures from European
producers. Congener and homologue group patterns of marine sediments showed similarities with
technical SCCP and MCCP mixtures and differences with those of river sediments and suspended
particular matter (ECNI-MS). CP patterns of marine sediments obtained by CACI-MS were similar
to technical mixtures with chlorine contents < 50%. Additionally, cluster analysis (CA) was used
for the differentiation between technical SCCP and MCCP mixtures. The main criterion of
differentiation was the degree of chlorination.
Congener and homologue group patterns of technical SCCP and MCCP mixtures were registered
and compared using ECNI-MS and CACI-MS. In contrast to CACI-MS, homologue and congener
group patterns obtained by ECNI-MS showed always a shift to the next higher chlorinated congener
of the same carbon chain length group. Consequently, the calculated molecular masses and chlorine
contents were always higher for ECNI-MS. However, for sediment samples a pronounced shift to
congeners with 2-3 more chlorine atoms was observed due to interfering compounds not removed
by the clean-up.
Technical CP mixtures and sediments were also characterized by comprehensive two-dimensional
(GC×GC) gas chromatography coupled to quadrupole LRMS. For single CP mixtures with the same
chlorine content but different carbon chain lengths the same main CP congeners were detected, e.g.
congeners with 5-8 chlorine atoms for mixtures with 50% chlorine content. Separation of MCCPs a
SCCPs could not be achieved with the selected stationary phase combination of ZB1-ms (first
column) and DB-17MS (second column). The applicability of this method was demonstrated for
sediments.
The developed clean-up procedure allowed also the determination of chlordane compounds in sea
sediments. Detection was carried out by conventional ECNI-MS on two different instruments and
by a newly developed method based on electron ionization tandem mass spectrometry (MS/MS).
This method showed comparable detection limits in the low pg range except for cisheptachlorepoxide,
where detection limits were higher one order of magnitude. Levels of
heptachlor, trans/cis-chlordane and trans/cis–nonachlor were determined. The concentrations
ranged between 7-144 pg/g d.w. for trans-nonachlor, < 2-29 pg/g d.w. for the cis isomer, < 2-135
pg/g d.w. for trans-chlordane, < 7-126 pg/g d.w. for cis-chlordane and 42-64 pg/g d.w. for
heptachlor. trans-Nonachlor concentrations were highest in all samples.