Pentafluorobenzylation of the fungicide metabolite fenpropimorphic acid for GC/MS investigations of soil samples

For the determination of fenpropimorphic acid in soil samples, a derivatization step with pentafluorobenzylbromide has been established in order to perform GC/MS with negative chemical ionization. In spite of forming the electrophilic pentafluorobenzyl ester, only the fenpropimophic acid anion was detected. Additional derivatization reactions with diazomethane and 2,2,2-trichloroethanol showed that the formation of this acid anion was depending on the leaving group. In comparison with the determination of the methyl ester with GC/MS and electron impact ionization, the detection limit was however improved from 10 microg/kg to 2 microg/kg dry soil and the analytical quality was ensured due to higher stability of the pentafluorobenzyl ester standards.     

Determination of misoprostol free acid in human breast milk and serum by gas chromatography/negative ion chemical ionization tandem mass spectrometry

To study an expected transition of misoprostol from human blood into breast milk, a novel method for the determination of its active metabolite misoprostol acid (MPA) was developed. MPA was determined in serum and breast milk samples by an isotope dilution assay using gas chromatography/negative ion chemical ionization tandem mass spectrometry (GC/NICI-MS/MS). After addition of (15S)-15-methylprostaglandin E(2) (15-methyl-PGE(2)) as an internal standard, MPA was extracted from both matrices using a reversed-phase cartridge. The prostanoids were derivatized with O-2,3,4,5,6-pentafluorobenzylhydroxylamine hydrochloride (PFBHA) and 2,3,4,5,6-pentafluorobenzyl bromide (PFBB) to the pentafluorobenzyl oxime (PFBO)-pentafluorobenzyl ester (PFB) derivatives. The sample was subjected to thin-layer chromatography with ethyl acetate-hexane (1 : 1 (v/v)) as the developing solvent. The corresponding zone was extracted. After derivatization to the trimethylsilyl ether, MPA was determined by GC/NICI-MS/MS using the [molecule (M) - pentafluorobenzyl (PFB)](-) ([P](-)) ions as precursor in the negative ion chemical ionization mode. The product ions used for quantification were [P - 2TMSOH - C(6)F(5)CH(2)OH](-) (MPA) and [P - 2TMSOH - C(6)F(5)CH(2)OH - CO(2)](-)(15-methyl-PGE(2)), respectively. The limit of quantification for MPA was approximately 1 pg ml(-1) in breast milk and serum samples. The correlation coefficients of the calibration curves for MPA were r > 0.997 in the 0.5-2000 pg ml(-1) range for both tested matrices.     

Gas chromatographic-mass spectrometric method for quantification of 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone in chlorinated water samples

A method for the determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2[5H]-furanone (MX), in drinking water by GC-MS with a limit of detection of 3.0 microg/l and a limit of quantification of 7.0 microg/l is presented. Clean-up by SPE and extraction of water samples with dichloromethane were carried out before the preconcentration of MX, which was derivatized directly in the injector of the GC, and the MX trimethylsilyl derivative was identified and quantitatively determined by MS.     

Multiresidue determination of pesticides in sediment by ultrasonically assisted extraction and gas chromatography/mass spectrometry

A gas chromatographic/mass spectrometric (GS/MS) method was developed for the multiple determination of pesticides in sediment. The investigated pesticides included 85 compounds, i.e., 13 fungicides, 43 herbicides, and 29 insecticides. The pesticides were extracted from sediment samples by an ultrasonically assisted procedure. The extract was cleaned up by using reversed-phase column chromatography followed by normal-phase column chromatography. A styrene-divinylbenzene copolymer cartridge and a silica gel cartridge were used as the reversed-phase column and the normal-phase column, respectively. The compounds were determined by GC/MS with 2 internal standard compounds. The overall recoveries were 70-105%, and the relative standard deviations ranged from 1.5 to 18%. The minimum detectable concentrations were 2-10 microg/kg. This method was successfully applied to sediment samples from the Shin River in Niigata, Japan. Twenty-five pesticides (6 fungicides, 11 herbicides, and 8 insecticides) were detected in the sediment samples. The concentrations of the detected pesticides ranged from 3 to 69 microg/kg. Herbicides were found May through July; insecticides and fungicides were found July through August, and during July through September, respectively. The presence of pesticides in the river sediment was correlated with the time of pesticide application in the Shin River basin.     

Ultra trace determination of fluorinated aromatic carboxylic acids in aqueous reservoir fluids by solid phase extraction in combination with negative ion chemical ionisation mass spectrometry after derivatisation with pentafluorobenzyl bromide

A new GC/MS method for the ultra trace analysis of fluorinated aromatic carboxylic acids after solid phase extraction and derivatisation with pentafluorobenzyl bromide is described. The pentafluorobenzyl esters formed were determined by negative ion chemical ionisation GC/MS in aqueous reservoir samples in concentrations as low as 0.010 μg/L. Determination of selected fluorinated aromatic carboxylic acids in aqueous reservoir samples, already injected as water tracers in North Sea reservoirs, confirmed the applicability of the method. Received: 5 September 1997 / Revised: 21 January 1998 / Accepted: 26 January 1998     

Performance of gas chromatography/tandem mass spectrometry in the analysis of pyrethroid insecticides in environmental and food samples

The performance of gas chromatography coupled with tandem mass spectrometry (GC/MS/MS) was tested for the simultaneous determination of twelve pyrethroid insecticides. First, a comparison of two different ionization modes, electron ionization (EI) and negative chemical ionization (NCI), was carried out using MS and MS/MS. NCI-MS/MS provided the best results in terms of selectivity and sensitivity giving very low detection limits of 0.11 to 450 fg injected. The reliability of the method was confirmed through the evaluation of quality parameters such as accuracy (70-100%), and repeatability and reproducibility, with coefficients of variation below 15% and 10%, respectively. The applicability of the GC/MS/MS method to real samples and influence of matrix effects were evaluated through the analysis of spiked water, sediment and milk at 0.25 ng L(-1) , 5 ng g(-1) dry weight (dw) and 25 ng g(-1) (dw), respectively, of each pyrethroid insecticide considered. Using GC/NCI-MS/MS, matrix spectral interferences were minimized providing method limits of detection (MLODs) of 0.05-2.59 ng L(-1) , 0.10-87.7 pg g(-1) dw, 2.29-1071 pg g(-1) lipid weight (lw) for water, sediment and milk, respectively. To the best of our knowledge, the MLOD values found in our study were better than those reported in previous studies; in particular for sediment and food samples, they were one order of magnitude lower.     

Ultra trace determination of fluorinated aromatic carboxylic acids in aqueous reservoir fluids by solid phase extraction in combination with negative ion chemical ionisation mass spectrometry after derivatisation with pentafluorobenzyl bromide

A new GC/MS method for the ultra trace analysis of fluorinated aromatic carboxylic acids after solid phase extraction and derivatisation with pentafluorobenzyl bromide is described. The pentafluorobenzyl esters formed were determined by negative ion chemical ionisation GC/MS in aqueous reservoir samples in concentrations as low as 0.010 μg/L. Determination of selected fluorinated aromatic carboxylic acids in aqueous reservoir samples, already injected as water tracers in North Sea reservoirs, confirmed the applicability of the method. Received: 5 September 1997 / Revised: 21 January 1998 / Accepted: 26 January 1998     

Quantification of 4-hydroxy-2,5-dimethyl-3-furanone in fruit samples using solid phase microextraction coupled with gas chromatography-mass spectrometry

Furaneol is an important aroma compound. It is very difficult to extract furaneol from food matrices and separate it on a gas chromatography column due to its high polarity and instability. A new quantitative method was developed to quantify furaneol in aqueous samples by the use of derivatization/solid phase microextraction (SPME) coupled with gas chromatography/mass spectrometry (GC/MS). The derivatization was carried out by reacting pentafluorobenzyl bromide with furaneol in basic solutions at elevated temperatures. The derivative was stable and less polar so that SPME-GC/MS could be applied for extraction, separation and detection. The automated analytical method had a limit of detection (LOD) of 0.5 ng mL(-1), a limit of quantification (LOQ) of 2 ng mL(-1), a repeatability of 9.5%, and a linear range from 2 to 500 ng mL(-1). The method was applied to analyze fruit samples. And it was found that the concentrations of furaneol in tomato ranged from 95 to 173 μg kg(-1), in strawberries ranged from 1663 to 4852 μg kg(-1). The results were verified with a LC procedure. To facilitate analytical method development, some physico-chemical parameters for furaneol were determined in this work. Its solubility in water was determined as 0.315 g mL(-1) (25°C). Its LogD in water and LogP in 0.1 M phosphate buffer were -0.133 and 0.95 (20 °C), respectively. Its pKa was 8.56 (20 °C).     

Global and selective detection of organohalogens in environmental samples by comprehensive two-dimensional gas chromatography-tandem mass spectrometry and high-resolution time-of-flight mass spectrometry

We successfully detected halogenated compounds from several kinds of environmental samples by using a comprehensive two-dimensional gas chromatograph coupled with a tandem mass spectrometer (GC×GC-MS/MS). For the global detection of organohalogens, fly ash sample extracts were directly measured without any cleanup process. The global and selective detection of halogenated compounds was achieved by neutral loss scans of chlorine, bromine and/or fluorine using an MS/MS. It was also possible to search for and identify compounds using two-dimensional mass chromatograms and mass profiles obtained from measurements of the same sample with a GC×GC-high resolution time-of-flight mass spectrometer (HRTofMS) under the same conditions as those used for the GC×GC-MS/MS. In this study, novel software tools were also developed to help find target (halogenated) compounds in the data provided by a GC×GC-HRTofMS. As a result, many dioxin and polychlorinated biphenyl congeners and many other halogenated compounds were found in fly ash extract and sediment samples. By extracting the desired information, which concerned organohalogens in this study, from huge quantities of data with the GC×GC-HRTofMS, we reveal the possibility of realizing the total global detection of compounds with one GC measurement of a sample without any pre-treatment.     

Analysis of aldehydes in water by solid-phase microextraction with on-fiber derivatization

The solid-phase microextraction (SPME) technique with on-fiber derivatization was evaluated for the analysis of aldehydes in water. The poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber was used and O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) were first loaded onto the fiber. The aldehydes in water sample were agitated into headspace and extracted by SPME with on-fiber derivatization. Gas chromatography/mass spectrometry (GC/MS) was used for the analysis of oximes formed and the adsorption-time profiles were examined. The precision, recovery and method detection limits (MDLs) were evaluated with spiked bidistilled water, chlorinated tap water as well as well water. The relative standard deviations from different spiked water sample were all less than 10% and the recoveries were 100 +/- 15%. With 2 ml of water sample, MDLs were in the range of 0.12-0.34 microg/l. Compared with other techniques, the study shown here provided a simple, fast and reliable method for the analysis of aldehydes in water.     

Fast gas chromatography with solid phase extraction clean-up for ultratrace analysis of pesticide residues in baby food

A sample preparation method based on single solvent phase extraction and solid-phase extraction (SPE-NH2) clean-up is studied in combination with fast capillary gas chromatography (GC) to determine 18 selected pesticides belonging to various chemical classes in apples, the common raw material for baby food production and baby food, at the concentration level < or = 10 microg/kg maximum residual limit (MRL). Possibilities of mass spectrometry (MS) detector and electron capture detector (ECD) in fast gas chromatography (GC) of samples with complex matrice at ultra trace levels of pesticide residues were studied and compared. MS detection in single ion monitoring (SIM) mode provided higher selectivity compared to ECD. Optimisation of extraction as well as the simplifying of the whole process of sample preparation was carried out. Recoveries obtained at concentration level of 5 microg/kg (the required value for limit of quantification (LOQ) in baby food) were >90%, except of dimethoate (77.7%) and captan (46.4%) with MS detection. The obtained LOQs were at least 1 order lower than 5 microg/kg for the majority of compounds. The repeatability of gas chromatography-mass spectrometry (GC-MS) measurements of the matrix matched standards expressed as relative standard deviation was <11% except of captan and cypermethrin.     

High-throughput GC/MS and HPLC/MS/MS techniques for the multiclass, multiresidue determination of 653 pesticides and chemical pollutants in tea

An efficient and sensitive method has been established for simultaneous determination of 653 pesticides in teas by GC/MS and HPLC/MS/MS. The method involved extraction with acetonitrile followed by cleanup using Cleanert-TPT SPE and subsequent identification and quantitation of 490 pesticides by GC/MS and 448 pesticides by HPLC/MS/ MS. The LODs for pesticides determined by GC/MS were between 1.0 and 500 microg/kg, and those determined by HPLC/MS/MS were between 0.03 and 4820 microg/kg. At the low fortification levels of 0.01-100 microg/kg, the average recoveries of 94% of the pesticides determined by GC/MS were between 60 and 120%, 77% of which had an RSD below 20%. For 91% of pesticides determined by HPLC/MS/MS, the average recoveries were between 60 and 120%, 76% of which had an RSD below 20%. The paper also reports a novel SPE column, Cleanert TPT, which comprised graphitized carbon black (PestiCarb), polyamine silica, and amide polystyrene for purifying the tea samples. The results indicated good repeatiblity and reproducibility.     

Improved analysis of volatile halogenated hydrocarbons in water by purge-and-trap with gas chromatography and mass spectrometric detection

An analytical system composed of a purge-and-trap injection system coupled to gas chromatography with mass spectrometric detection (PTI-GC-MS) specific for the analysis of volatile chlorinated hydrocarbons (VCHCs) (chloroform; 1,1,1-trichloroethane; tetrachloromethane; 1,1,2-trichloroethylene; tetrachloroethylene) and trihalomethanes (THMs) (chloroform; bromodichloromethane; dibromochloromethane; bromoform) in water was optimised. Samples were purged and trapped in a cold trap (-100 degrees C) fed with liquid nitrogen (cryo-concentration). In order to make this method suitable also for only slightly contaminated waters, some modifications were made to PTI sample introduction, in order to avoid any air intake into the system. PTI, GC and MS conditions were optimised for halogenated compound analysis and limits of detection (LOD) were evaluated. The proposed method allows analysis of samples whose concentrations range from microg/L to ng/L. It is, therefore, applicable to drinking waters, in analyses required by law, and to slightly contaminated aqueous matrices, such as those found in remote areas, in environmental monitoring. Moreover, by changing cold trap temperature, even sparkling mineral waters can be analysed, thus avoiding CO2 interference during the cryo-concentration phase. Our method has been successfully used on real samples: tap water, mineral water and Antarctic snow.     

Development of a rapid and sensitive method for the simultaneous determination of 1,2-dibromoethane, 1,4-dichlorobenzene and naphthalene residues in honey using HS-SPME coupled with GC-MS

A new method for the simultaneous determination of 1,4-dichlorobenzene (p-DCB), naphthalene and 1,2-dibromoethane (1,2-DBE) residues in honey has been developed. Analysis is carried out using gas chromatography-mass spectrometry (GC/MS) in selected ion monitoring mode (SIM), after extraction and preconcentration of target analytes by headspace solid-phase microextraction (HS-SPME), with a 100 microm film thickness polydimethylsiloxane (PDMS) fiber. Several parameters affecting the extension of the adsorption process (i.e., addition of salt, extraction time, extraction temperature) were studied. The optimal conditions for the determination of these analytes were established. The proposed HS-SPME method showed good sensitivity, without carryover between the samples. Linearity was studied from 5 to 2500 microg kg(-1) for p-DCB, 0.5 to 500 microg kg(-1) for naphthalene and 5 to 500 microg kg(-1) honey for 1,2-DBE with correlation coefficients (r(2)) ranging from 0.9901 to 0.9999. Precision was assessed and both intra and inter-day R.S.D.s (%) were below 6.3%. The detection limits were found to be 1, 0.1 and 2 microg kg(-1) honey for p-DCB, naphthalene and 1,2-DBE, respectively. The percentage recoveries that were evaluated with the proposed HS-SPME method and the standard addition calibration technique gave values among 72.8 and 104.3% for measurements in samples spiked with one target analyte or mixtures of the three. This method has been applied for the analysis of unknown honey samples. The results showed an excellent applicability of the proposed method for the determination of the target compounds in honey samples.     

A novel approach for simultaneous determination of 2-mercaptobenzimidazole and derivatives of 2-thiouracil in animal tissue by gas chromatography/mass spectrometry

A novel approach for determination of 2-mercaptobenzimidazole (MBI) and other thyreostatic residues in animal tissues by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring mode was developed. The analytes in animal tissues (including hypothyroid, pork muscle and beef samples) were extracted by acetonitrile, and then purified by a matrix solid-phase dispersion (MSPD) procedure after the extraction residues had been dissolved in water. The thyreostatic residues were derivatized by pentafluorobenzyl bromide (PFBBr) under strong basic conditions and then N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) before GC/MS analysis. Different kinds of solid supports with various polarities for the MSPD procedure were investigated, and it was found that silica gel was suitable for the purpose. The average recoveries of the thyreostatic drugs in animal tissues ranged from 71.5-96.9% with the relative standard deviations below 10%. By using the developed method, the limits of detection were 10 microg/kg for MBI; 5 microg/kg for 6-phenyl-2-thiouracil; and 2 microg/kg for 2-thiouracil, 6-methyl-2-thiouracil and 6-propyl-2-thiouracil. The stability of the thyreostatic drugs in spiked animal tissues was tested, and the results showed that the thyreostatic drugs did not decompose within 3 months if the sample was stored in darkness below -20 degrees C.     

Pentafluorobenzylation of the fungicide metabolite fenpropimorphic acid for GC/MS investigations of soil samples

For the determination of fenpropimorphic acid in soil samples, a derivatization step with pentafluorobenzylbromide has been established in order to perform GC/MS with negative chemical ionization. In spite of forming the electrophilic pentafluorobenzyl ester, only the fenpropimophic acid anion was detected. Additional derivatization reactions with diazomethane and 2,2,2-trichloroethanol showed that the formation of this acid anion was depending on the leaving group. In comparison with the determination of the methyl ester with GC/MS and electron impact ionization, the detection limit was however improved from 10 g/kg to 2 g/kg dry soil and the analytical quality was ensured due to higher stability of the pentafluorobenzyl ester standards.     

Trace determination of organotin compounds in water,sediment and mussel samples by low-pressure gas chromatography coupled to tandem mass spectrometry

A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain).     

Evaluation of atmospheric pressure ionization interfaces for quantitative measurement of sulfonamides in honey using isotope dilution liquid chromatography coupled with tandem mass spectrometry techniques

A comparison was made between electrospray, atmospheric pressure chemical and atmospheric pressure photospray ionizations to evaluate the MS/MS responses of standard sulfonamides and honey spiked samples. The sample preparation entails an acidic hydrolysis followed by a liquid/liquid extraction. Full method validation was realised by LC-APPI-MS/MS. Decision limit and detection capability were calculated for each analyte (at 50 microg/kg) and ranged between 53.6 and 56.9 and 57.5 and 63.2 microg/kg, respectively. Limits of detection and of quantification ranged, respectively, at 0.4-4.5 and 1.2-15.0 microg/kg. Precursor ion scan experiments of m/z 92 were also carried out as a survey experiment, linked with an enhanced product ion scan experiment to potentially identified additional sulfonamides via a library search.     

A new and fast extraction method for the determination of priority phenols from marine sediments by liquid chromatography

A new and fast method for the determination of priority phenols in marine sediment samples by high-performance liquid chromatography using microwave-assisted micellar extraction is optimized. This study is carried out using the nonionic surfactants polyoxyethylene 9 lauryl ether (polidocanol) and genapol X-080 as extractants. Parameters studied include surfactant concentration, solution pH, extraction time, and power. Once the method is optimized, it is applied to different spiked marine sediments from of the Canary Islands coastlines (Spain). The results obtained indicate that a power irradiation of 500 W for 2 min achieved the best extraction efficiency (approximately 100% recovery) and less than 10% relative standard deviation. Detection limits are obtained in the 2-20 microg/g range for the phenols studied. Finally, the proposed method provides a simple, fast, and organic solvent-free procedure to analyze phenols from marine sediment samples.     

Drop-to-drop solvent microextraction coupled with gas chromatography/mass spectrometry for rapid determination of trimeprazine in urine and blood of rats: application to pharmacokinetic studies

A simple and rapid method based on drop-to-drop solvent microextraction (DDSME) coupled with gas chromatography/mass spectrometry (GC/MS) has been successfully applied for the pharmacokinetic studies of trimeprazine in 8 microL of urine and blood samples of rats. Several factors that influenced the extraction efficiency of DDSME, such as selection of organic solvent, extraction time, exposure volume of organic phase, addition of salt and pH, were optimized. Linearity was obtained over the concentration ranges of 0.2-10, 0.25-7.0 and 0.5-6.0 microg/mL with correlation coefficients of 0.998, 0.996 and 0.993 in deionized water, urine and blood samples of rats, respectively. The limits of detection (LODs) of trimeprazine were 0.05, 0.06 and 0.1 microg/mL in deionized water, urine and blood samples. The concentrations of trimeprazine obtained in urine and blood samples of rats were 0.21-1.25 and 2.72-0.22 microg/mL, respectively, after a single intravenous administration of this drug. The enrichment factors and LOD values obtained by DDSME coupled to GC/MS were compared with those of hollow fiber liquid-phase microextraction (HF-LPME) combined with GC/MS. We believe that this novel approach can be very useful in clinical application since only one microdrop of biological samples was required to perform the pharmacokinetic studies from rats, so the sample pretreatments for animal experiments can be very easy too.