Optimization and evaluation of low-pressure gas chromatography-mass spectrometry for the fast analysis of multiple pesticide residues in a food commodity.
ABSTRACT A fast method of analysis for 20 representative pesticides was developed using low-pressure gas chromatography-mass spectrometry (LP-GC-MS). No special techniques for injection or detection with a common quadrupole GC-MS instrument were required to use this approach. The LP-GC-MS approach used an analytical column of 10 m x 0.53 mm I.D., 1 microm film thickness coupled with a 3 m x 0.15 mm I.D. restriction capillary at the inlet end. Thus, the conditions at the injector were similar to conventional GC methods, but sub-atmospheric pressure conditions occurred throughout the analytical column (MS provided the vacuum source). Optimal LP-GC-MS conditions were determined which achieved the fastest separation with the highest signal/noise ratio in MS detection (selected ion monitoring mode). Due to faster flow-rate, thicker film, and low pressure in the analytical column, this distinctive approach provided several benefits in the analysis of the representative pesticides versus a conventional GC-MS method, which included: (i) threefold gain in the speed of chromatographic analysis; (ii) substantially increased injection volume capacity in toluene; (iii) heightened peaks with 2 s peak widths for normal MS operation; (iv) reduced thermal degradation of thermally labile analytes, such as carbamates; and (v) due to larger sample loadability lower detection limits for compounds not limited by matrix interferences. The optimized LP-GC-MS conditions were evaluated in ruggedness testing experiments involving repetitive analyses of the 20 diverse pesticides fortified in a representative food extract (carrot), and the results were compared with the conventional GC-MS approach. The matrix interferences for the quantitation ions were worse for a few pesticides (acephate, methiocarb, dimethoate, and thiabendazole) in LP-GC-MS, but similar or better results were achieved for the 16 other analytes, and sample throughput was more than doubled with the approach.
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ABSTRACT: This chapter describes an easy, rapid, and low-cost sample preparation approach for the determination of pesticide residues in foods using gas and/or liquid chromatographic (GC and/or LC) analytical separation and mass spectrometric (MS) detection. The approach is known as QuEChERS, which stands for "quick, easy, cheap, effective, rugged, and safe." Originally, QuEChERS was a particular "method" for pesticide residue analysis, but it is very flexible and has evolved into an "approach," which has been used in many methods, and not just for pesticide residues. Two of the QuEChERS versions using buffering have been validated in interlaboratory trials for dozens of pesticides in several food matrices, and both have successfully met performance criteria to achieve "official" status from international standard organizations (AOAC Official Method 2007.01 and CEN Standard Method EN 15662). The main aspects of the QuEChERS approach consists of extraction of a well-homogenized sample by shaking with solvent (typically acetonitrile) in a centrifuge tube, salt-out partitioning of water with salts including magnesium sulfate (MgSO(4)), and cleanup using "dispersive solid-phase extraction" (dSPE), in which common matrix components are retained by sorbent(s) and the analytes remain in the extract. For widest analytical scope, concurrent analysis is done for hundreds of pesticides using GC-MS(/MS) and LC-MS/MS. The aim of this chapter is to review the QuEChERS sample preparation methodology and provide a summary of up-to-date information with modification options depending on the application needs.Methods in molecular biology (Clifton, N.J.) 01/2011; 747:65-91. · 1.29 Impact Factor
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ABSTRACT: Emerging flame retardants are used in a great variety of household goods and thus have the potential to pollute our indoor environment. Health concerns regarding exposure to these flame retardants demand new methods to survey their occurrence in humans. This work describes development and optimization of an analytical method comprising solid phase extraction and gas chromatography coupled to mass spectrometry for the determination of besides 15 polybrominated diphenyl ethers, 7 emerging halogenated flame retardants in human serum (1,2-bis[2,4,6-tribromophenoxy] ethane, decabromodiphenyl ethane, hexabromobenzene, Dechlorane Plus(®), hexachlorocyclopentenyl-dibromocyclooctane, dechlorane 602 and 603). The method was thoroughly validated at three spiking levels obtaining averaged recoveries >80% with a RSD of 5% (n=12). Accuracies ranged from 88 to 125% except for DBDPE, which averaged 66% with overall RSD of 11% (n=12). Method limits of detection (MLD) ranged from 0.3 to 5.4pg/mL serum, except for decabromodiphenyl ether and decabromodiphenyl ethane for which MLDs were 14 and 20pg/mL serum, respectively. In human serum samples from Norway, we were able to detect and quantify hexabromobenzene, 1,2-bis[2,4,6-tribromophenoxy] ethane, Dechlorane Plus(®), Dechlorane 602 and 603.Journal of Chromatography A 08/2013; · 4.61 Impact Factor
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ABSTRACT: In this study, we evaluate advantages and disadvantages of three hyphenated techniques for mercury speciation analysis in different sample matrices using gas chromatography (GC) with mass spectrometry (GC-MS), inductively coupled plasma mass spectrometry (GC-ICP-MS) and pyrolysis atomic fluorescence (GC-pyro-AFS) detection. Aqueous ethylation with NaBEt(4) was required in all cases. All systems were validated with respect to precision, with repeatability and reproducibility <5% RSD, confirmed by the Snedecor F-test. All methods proved to be robust according to a Plackett-Burnham design for 7 factors and 15 experiments, and calculations were carried out using the procedures described by Youden and Steiner. In order to evaluate accuracy, certified reference materials (DORM-2 and DOLT-3) were analyzed after closed-vessel microwave extraction with tetramethylammonium hydroxide (TMAH). No statistically significant differences were found to the certified values (p=0.05). The suitability for water samples analysis with different organic matter and chloride contents was evaluated by recovery experiments in synthetic spiked waters. Absolute detection and quantification limits were in the range of 2-6 pg for GC-pyro-AFS, 1-4 pg for GC-MS, with 0.05-0.21 pg for GC-ICP-MS showing the best limits of detection for the three systems employed. However, all systems are sufficiently sensitive for mercury speciation in environmental samples, with GC-MS and GC-ICP-MS offering isotope analysis capabilities for the use of species-specific isotope dilution analysis, and GC-pyro-AFS being the most cost effective alternative.Journal of Chromatography A 07/2011; 1218(28):4545-51. · 4.61 Impact Factor
EASTERN REGIONAL RESEARCH CENTER
AGRICULTURAL RESEARCH SERVICE
UNITED STATES DEPARTMENT OF AGRICULTURE
600 E. MERMAID LANE
WYNDMOOR, PA 19038
Optimization and Evaluation of Low-Pressure Gas Chromatography-Mass
Spectrometry for the Fast Analysis of Multiple Pesticide Residues in a Food
Author(s): K. Mastovska, S.J. Lehotay and J. Hajslova
Journal of Chromatography A (2001) 926: 291-308
This article was written and prepared by U.S. Government employees on official time, and is
therefore in the public domain.
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