Dzintars Zacs

The development and validation of a rapid method for the determination of antimicrobial agent residues in milk and meat using ultra performance liquid chromatography coupled to quadrupole--Orbitrap mass spectrometry.

A new multi-class method has been developed for the identification and quantification of the residues of 26 antibiotics from different classes (sulfonamides, macrolides, tetracyclines, penicillins, and quinolones) in milk and meat by ultra performance liquid chromatography coupled to hybrid quadrupole - high resolution Orbitrap mass spectrometry (UPLC-qOrbitrap). The sample preparation included extraction of two analytical portions with acetonitrile and 5% trichloroacetic acid, respectively, followed by centrifugation and filtration. The method was validated over three days at 50% of MRL (maximum residue limit) set in the European Union. Experiments on spiked meat and milk samples showed that the average recovery of the antibiotics ranged from 83% to 112%, and the coefficients of variation were between 8.9% and 39%.

Occurrence of brominated persistent organic pollutants (PBDD/DFs, PXDD/DFs, and PBDEs) in Baltic wild salmon ( Salmo salar ) and correlation with PCDD/DFs and PCBs.

The contamination profiles of polybrominated dibenzo-p-dioxins (PBDDs), dibenzofurans (PBDFs), diphenyl ethers (PBDEs), and mixed monobromo/chloro dibenzo-p-dioxins (PXDDs) and dibenzofurans (PXDFs) were determined in the tissue of Baltic wild salmon and compared with those of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs). Out of the analyzed PXDD/DFs, only the 3-B-2,7,8-triCDF was detected (in the concentration range of 0.039-0.075 pg g(-1) fresh weight (f.w.)). The toxic equivalents (TEQs) for analyzed PBDD/DFs (0.074-0.142 pg TEQ g(-1) f.w.) were found to contribute on average 2.1% to the total PCDD/DF-PBDD/DF-TEQ. The total concentrations of 27 PBDE congeners were in the range of 1.3-5.6 ng g(-1) f.w., with an average of 3.3 ng g(-1) f.w. The levels of PCDD/DFs and PCBs were found to be in the range of 4.53-14.6 pg WHO(2005)-PCDD/DF-PCB-TEQ g(-1) f.w., and concentrations of these compounds in most of the analyzed samples were above the maximum levels specified in Commission Regulation (EU) No. 1259/2011. Good correlation was observed between WHO(2005)-PCDD/DF-TEQ and WHO(2005)-PCB-TEQ (r(2) = 0.98), and these parameters were well correlated with the total sum of PBDE concentrations (r(2) = 0.91 and r(2) = 0.94, respectively). The results suggest that the consumption of Baltic wild salmon has no crucial impact on the average POP intake for typical Latvians.

Ultra high performance liquid chromatography-time-of-flight high resolution mass spectrometry in the analysis of hexabromocyclododecane diastereomers: method development and comparative evaluation versus ultra high performance liquid chromatography coupled to Orbitrap high resolution mass spectrometry and triple quadrupole tandem mass spectrometry.

An efficient ultra high performance liquid chromatography (UHPLC)-time-of-flight high resolution mass spectrometry (TOF-HRMS) method was elaborated for the determination of hexabromocyclododecane (HBCD) diastereomers in fish samples and compared against UHPLC-Orbitrap-HRMS and UHPLC-triple quadrupole (QqQ) tandem MS (MS/MS) techniques. The TOF-HRMS analyzer was operated at high resolution (>10000 full width at half maximum (FWHM)) with scanning the m/z range from 600 to 700, to achieve picogram quantitation limits. The effects of various operational parameters on the instrumental response were systematically investigated. Evaluation of the influence of sample clean-up procedure steps on signal suppression effect including removal of the matrix components by means of destructive acidic treatment or non-destructive gel permeation chromatography (GPC), and additional Florisil column chromatography step showed that the analytical response of UHPLC-TOF-HRMS system is much more affected by the presence of matrix components in the final extracts in comparison with UHPLC-Orbitrap-HRMS and UHPLC-QqQ-MS/MS systems. The method was robustly validated and used for the analysis of eel (Anquilla anquilla) samples originating from a Latvian lake. UHPLC-TOF-HRMS showed a suitable performance under the optimized conditions: recoveries for three selected diastereomers in the range of 99-116%; repeatability and intermediate precision expressed as relative standard deviation (RSD) in the ranges of 2.3-7.1% and 2.9-8.1%, respectively. The elaborated method achieved instrumental limits of quantification (i-LOQ) of 0.9-4.5pg on column that were suitable for the trace analysis of three HBCD diastereomers, corresponding to the method limits of quantification (m-LOQ) of 7.0-29pgg(-1) wet weight (w.w.). The efficiency of UHPLC-TOF-HRMS method was evaluated by comparing the performance characteristics and analytical data from real samples with the validation data and real sample results obtained by applying UHPLC-Orbitrap-HRMS and UHPLC-QqQ-MS/MS techniques for the analysis of HBCD in the same fish samples. Statistical assessment of the experimental data by means of the Fiedmans test revealed that UHPLC-TOF-HRMS, UHPLC-QqQ-MS/MS and UHPLC-Orbitrap-HRMS techniques produced adequate and similar results regarding the HBCD content in fish samples. The presence of HBCD diastereomers was confirmed in all the analyzed eels at concentrations up to 554pgg(-1) w.w. for total HBCD and a diastereomer pattern typical for aquatic biota was observed with strong predominance of α-HBCD. The UHPLC-TOF-HRMS is an appropriate technique for diastereomer-specific quantification of HBCD content in fish samples.

New perspectives on diastereoselective determination of hexabromocyclododecane traces in fish by ultra high performance liquid chromatography-high resolution orbitrap mass spectrometry

A new analytical method is presented for diastereoisomer-specific identification and quantitation of hexabromocyclododecanes (HBCD) in fish samples. The method is based on extraction of the target analytes from samples with a mixture of organic solvents, with further three-stage clean-up including destructive removal of matrix components with sulphuric acid and acid-impregnated silica gel, and Florisil adsorption column chromatography. Ultra high performance liquid chromatography (UPLC) coupled with high resolution (HR) Orbitrap mass spectrometry featuring heated electrospray ionization (HESI-II) interface operated in negative ion mode was employed for the identification/quantitation of contaminants. The developed methodology was robustly validated in terms of recovery, repeatability, intermediate precision, linear calibration ranges, limits of detection and quantitation, and used for analysis of twenty five Baltic wild salmon (Salmo salar) samples. Under the optimized conditions, recoveries for selected analytes were within the range of 91.4-103.6%, and the repeatability and intermediate precision in terms of relative standard deviations (RSDs) were in the ranges 1.6-8.3% and 1.6-12.5%, respectively, for all three validation levels. The elaborated method achieved instrumental limits of quantification (i-LOQ) of 1.3-3.0pg on column for three HBCD diastereoisomers corresponding to the method LOQ of 0.005-0.012ngg(-1) wet weight (w.w.) The presence of HBCD diastereoisomers was confirmed in all the analyzed Baltic salmon samples in the concentration range of 0.39-3.82ngg(-1) w.w. with an average of 1.59ngg(-1) w.w. for total HBCD. The diastereomer pattern typical for aquatic biota was observed with strong predominance of α-HBCD. The newly developed methodology could be employed for a regular diastereomer-specific monitoring of HBCD content in fish samples, representing a good alternative to existing LC-MS/MS methods in terms of sensitivity and accuracy, and providing further possibilities for inclusion of other contaminants in the scope of analysis.

Content of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in fish from Latvian lakes.

Seventeen polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/PCDFs) of the highest priority as well as twelve dioxin-like polychlorinated biphenyls (dl-PCBs) were analyzed in the muscle tissues of the following freshwater fish species sampled from eleven Latvian freshwater lakes: perch (Perca flavescens), carp (Cyprinus carpio), eel (Anguilla rostrata), bream (Abramis brama), chub (Leuciscus cephalus), pike (Esox lucius), sheatfish (Silurus glanis) and roach (Rutilus). To analyze the selected persistent organic pollutants in fish matrices, an optimization of EPA-1613 and EPA-1668A clean-up procedures was carried out, followed by validation of the analytical procedure according to Commission Regulation (EC) No 1883/2006. The adopted analytical procedure was in compliance with requirements of the more recent Commission Regulation (EU) No 252/2012. Modifications of carbon column chromatography clean-up and separation steps were used for treatment of the fish samples. Other clean-up procedure stages were performed according to the methods EPA-1613 and EPA-1668A and involved gel permeation chromatography (GPC), as well as manual acidic silica and Florisil column chromatography for purification and fractionation of the samples. An isotope dilution method was used for the qualitative and quantitative determination of individual congeners. Analytes of interest were separated and detected using gas chromatography - high resolution mass spectrometry. The concentration of PCDD/PCDFs and dl-PCBs in freshwater fish and eel samples ranged from 0.05 to 8.0 pg WHO(1998)-PCDD/PCDF-PCB-TEQ g(-1) fresh weight. These levels are below the EU maximum permissible limits although calculation of the content of these compounds relative to the weight of fat shows contamination levels similar to those found in Baltic herring and sprats, that are known to be highly contaminated. A difference in congener pattern between the Baltic Sea fish and freshwater fish was detected with lower contribution of 2,3,4,7,8-PeCDF to the contamination of inland water fish.

Method development for the simultaneous determination of polybrominated, polychlorinated, mixed polybrominated/chlorinated dibenzo-p-dioxins and dibenzofurans, polychlorinated biphenyls and polybrominated diphenyl ethers in fish

An analytical methodology was developed for simultaneous determination of five groups of persistent organic pollutants (POPs) including polybrominated, polychlorinated and mixed brominated-chlorinated dibenzo-p-dioxins and dibenzofurans (PBDD/DFs, PCDD/DFs and PXDD/DFs, respectively), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in fish samples. The presented analytical approach was based on well established and robust method for determination of PCDD/DFs and PCBs, which was augmented with gas chromatography coupled to high resolution mass spectrometry (GC-HRMS) to include PBDEs, as well as poorly investigated PBDD/DFs and PXDD/DFs at toxicologically significant levels. Intensive clean-up and fractionation procedures in combination with optimized instrumental parameters provided reliable detection and quantification of these compounds. The application of (13)C12-labeled surrogates of analyzed compounds allowed the internal standardization and accurate measurement of selected contaminants. The developed procedure was validated while taking into account the Commission Regulation (EU) 252/2012 requirements for PCDD/DFs and PCBs, and was used to measure the occurrence of priority POPs in Baltic wild salmon.

Brominated, chlorinated and mixed brominated/chlorinated persistent organic pollutants in European eels (Anquilla anquilla) from Latvian lakes

ABSTRACT Fifty-eight European eel (Anquilla anquilla) specimens collected from five Latvian lakes were investigated for six groups of persistent organic pollutants (POPs), including polychlorinated, polybrominated and mixed bromo-chloro dibenzo-p-dioxins and dibenzofurans (PCDD/DFs, PBDD/DFs and PXDD/DFs), polychlorinated and mixed bromo-chloro biphenyls (PCBs and PXBs) and polybrominated diphenyl ethers (PBDEs). PCDD/DFs and PCBs were found to occur in the range 0.85–15.8 pg Total-WHO2005-TEQ g−1 f.w., and concentrations in most of the samples were below the maximum levels specified in European Commission Regulation (EU) No. 1259/2011. The summed concentrations of 27 PBDEs (∑PBDE) and 16 non-dioxin-like PCBs (∑NDL-PCB) were in the ranges of 0.28–26.7 and 6.37–320 ng g−1 f.w., respectively. PBDD/DFs, PXDD/DFs and PXBs show average upper-bound concentrations of 0.05, 0.06 and 0.01 pg TEQ f.w. and collectively contributed 3.4% to the sum TEQ of dioxin-like compounds. The highest contaminant concentrations were measured in samples from lakes near the Baltic Sea and the industrialised area near Riga (Liepajas and Kisezers lakes). A correlation of POP concentration with the length of collected specimens was observed.

A comparison of gas chromatography coupled to tandem quadrupole mass spectrometry and high-resolution sector mass spectrometry for sensitive determination of polycyclic aromatic hydrocarbons (PAHs) in cereal products

Due to the high consumption level, cereals represent one of the major sources of human exposure to PAHs. Taking into account the low maximum permitted level (ML) established in the European Union (EU) for the sum of four priority PAHs (PAH4) in processed cereal-based foods, sensitive and selective analysis for very low concentrations of these carcinogenic compounds was developed and compared by applying two different analytical techniques. Elaborated methods demonstrated appropriate performance in PAHs analysis even at low contamination levels. Limits of detection (LOD) for the PAH4 varied between 0.002μgkg-1 and 0.006μgkg-1, recoveries were in the range of 92-103% for GC-MS/MS and 108-117% for GC-HRMS. Elaborated methods were applied for the analysis of 35 Latvian cereals and bread samples. The concentrations of PAH4 were in a range of 0.22-1.62μgkg-1 with 14% of samples exceeding the current EU maximum permitted levels.

The occurrence of Dechlorane Plus and related norbornene-based flame retardants in Baltic wild salmon (Salmo salar).

Twenty five Baltic wild salmon (Salmo salar) specimens were analysed for the content of Dechlorane-related compounds (DRCs). Out of the ten analysed DRCs, seven compounds were detected in the muscle tissues of salmon, including Dechlorane (Dec) 602, Dec 603, syn- and anti-stereoisomers of Dechlorane Plus (DP), Dechlorane Plus monoadduct (1,3-DPMA), hexachlorocyclopentadienyl-dibromocyclooctane (DBHCTD), and Mirex. The concentrations of Dec 604 and two DP dechlorinated compounds - decachloropentacyclooctadecadiene (Cl10DP) and undecachloropentacyclooctadecadiene (Cl11DP) - were below the limit of detection in all samples. The aggregated concentrations of DRCs (ΣDRC) were in the range of 551-3339 pg g(-1) fresh weight (f.w.) with 1,3-DPMA being the predominant DRC component contributing up to 70% to the ΣDRC. The fractional abundance of syn- and anti-DP stereoisomers showed a pronounced enrichment of anti-DP and was close to the composition of OxyChem(®) DP commercial product. The obtained concentrations of DRCs were substantially lower than those reported in previous studies of biotic samples (among them fish, mollusks, white stork and peregrine falcon eggs) from inland freshwater reservoirs in more industrialised areas throughout Europe and North America. A statistically significant relationships between the concentrations of Dec 602 and the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) was observed.

Polycyclic aromatic hydrocarbons in traditionally smoked meat products from the Baltic states

ABSTRACT A total of 77 traditionally smoked meat samples produced in Latvia, Lithuania, and Estonia were tested for the occurrence of four EU regulated polycyclic aromatic hydrocarbons (PAHs). Levels of PAHs exceeding the EU maximum levels for benzo[a]pyrene and for the sum of four PAHs (PAH4) were detected in 46% and 48% of the samples originating from Latvia. The detected BaP levels in smoked meats ranged from 0.05 to 166 μg kg−1, while the PAH4 content ranged from 0.42 to 628 μg kg−1. The mean dietary exposure to PAHs was estimated at the levels of 5.4 ng BaP/kg bw/day and 36 ng PAH4/kg bw/day. The margin of exposure (MOE) approach was utilised to assess the risks to Latvian consumers due to PAHs and the obtained MOEs were in a range of 7205–24,434, thus indicating a potential concern for consumer health for specific population groups.