Determination of polycyclic aromatic hydrocarbons in honey by matrix solid-phase dispersion and gas chromatography/mass spectrometry

A multiresidue method was developed for the de termination of 16 polycyclic aromatic hydrocarbons (PAHs) in unifloral and multifloral honeys. The analytical procedure is based on the matrix solid-phase dispersion of honey on a mixture of Florisil and anhydrous sodium sulfate in small glass columns and extraction with hexane-ethyl acetate (90 + 10, v/v) with assisted sonication. The PAH residues are determined by gas chromatography with mass spectrometric detection using selected-ion monitoring. Average recoveries for all the PAHs studied were in the range of almost 80 to 101%, with relative standard deviations of 6 to 15%. The limits of detection ranged from 0.04 to 2.9 microg/kg. The simultaneous extraction and cleanup of samples makes this method simple and rapid, with low consumption of organic solvents     

Multiresidue determination of pesticides in honey by matrix solid-phase dispersion and gas chromatography with electron-capture detection

A multiresidue method was developed for the determination of 15 pesticides (organochlorines, organophosphorus compounds, pyrethroids, and other acaricides) in various commercial honeys (eucalyptus, lavender, orange, rosemary, and multifloral). The analytical procedure is based on the matrix solid-phase dispersion of honey in a mixture of Florisil and anhydrous sodium sulfate; the mixture is placed in small plastic columns and extracted with hexane-ethyl acetate (90 + 10, v/v). The pesticide residues are determined by capillary gas chromatography with electron-capture detection. Recoveries with the method at concentrations between 0.15 and 1.5 microg/g ranged from 80 to 113%, and relative standard deviations were <10% for all the pesticides studied. The pesticide detection limits were within the range 0.5-5 microg/kg for organochlorines, around 3 microg/kg for the chlorinated organophosphorus pesticides studied, near 15 microg/kg for fluvalinate, and about 3 microg/kg for the other pyrethroids.     

Determination of thiabendazole in orange juice and rind by liquid chromatography with fluorescence detection and confirmation by gas chromatography/mass spectrometry after extraction by matrix solid-phase dispersion

A method was developed for the determination of thiabendazole (TBZ) in orange juice and rind based on matrix solid-phase dispersion (MSPD). TBZ was extracted with ethyl acetate and the extract was subsequently cleaned up on a solid-phase extraction column. Fungicide residues were determined by liquid chromatography with fluorescence detection. Recoveries through the method ranged from 87 to 97% with relative standard deviations < or = 11%. The detection and quantitation limits were 0.15 and 0.50 microg/kg, respectively. The confirmation of TBZ residues in positive samples was performed by solid-phase microextraction followed by gas chromatography with mass spectrometric detection using selected ion monitoring. The developed method was applied to determine TBZ levels in commercial orange juices and in juice and rind of fresh oranges. The influence of storage and washing of fruits on TBZ residues was also studied.     

Determination of phthalate esters in water samples by solid-phase microextraction and gas chromatography with mass spectrometric detection

Solid-phase microextraction (SPME) with an 85 microm polyacrylate fiber, coupled to gas chromatography-mass spectrometry was used to determine six phthalate esters and bis(2-ethylhexyl) adipate in water samples. The variables affecting the SPME absorption process were optimized and the method developed was applied to analyze both tap and commercial mineral water samples as well as water from the Ebro river and fishing and industrial ports. For real samples, the linear range in full scan acquisition mode was between 0.02 and 10 microg l(-1) for most compounds, and the limits of detection of the method were between 0.006 and 0.17 microg l(-1). Commercial water samples contained in recipients which were made from different materials were analyzed, and the influence of the material of the recipients on the concentration of phthalates was evaluated.     

Determination of coumaphos, chlorpyrifos and ethion residues in propolis tinctures by matrix solid-phase dispersion and gas chromatography coupled to flame photometric and mass spectrometric detection

A new analytical method has been developed and successfully evaluated in routine application for the quantitative analysis of a selected group of organophosphate pesticides (coumaphos, chlorpyrifos and ethion) which can be found at trace levels in propolis tinctures (ethanolic propolis extracts); a valuable commodity used as raw material in the food and pharmaceutical industries for which there have been few attempts for pesticide residue analysis reported in the literature. The proposed methodology is based on matrix solid phase dispersion (MSPD) using aluminum sulfate anh. a novel dispersant material and subsequent column chromatography clean-up in silica gel prior to gas chromatography (GC) with both flame photometric detector (FPD) and mass spectrometry (MS) detection used for the routine quantification and identification of the residues, respectively. The limits of detection, for coumaphos, chlorpyrifos and ethion were below 26.0 μg/kg in FPD and 1.43 μg/kg for MS detection. Mean recoveries were in the range of 85-123% with RSD values below 13%, which suggests that the proposed method is fit for the purpose of analyzing pesticides in propolis tinctures containing high concentration of polyphenolics. The method has been successfully applied in our laboratory for the last 2 year in the analysis of real propolis tinctures samples.     

Determination and identification of isoflavonoids in Radix astragali by matrix solid-phase dispersion extraction and high-performance liquid chromatography with photodiode array and mass spectrometric detection

The isoflavonoids in Radix astragali were determined and identified by HPLC-photodiode array detection-MS after extraction employing matrix solid-phase dispersion (MSPD). As a new sample preparation method for R. astragali, the MSPD procedure was optimized, validated and compared with conventional methods including ultrasonic and Soxhlet extraction. The amounts of two major components in this herb, formononetin (6) and ononin (2), were determined based on their authentic standards. Four major isoflavonoids, formononetin (6), ononin (2), calycosin (5) and its glycoside (1), and three minor isoflavonoids, (6aR,11aR)-3-hydroxy-9, 10-dimethoxypterocarpan (7), its glycoside (3), and (3R)-7,2'-dihydroxy-3',4'-dimethoxyisoflavone-7-O-beta-D-glycoside (4), were identified based on their characteristic two-band UV spectra and [M + H], [aglycone + H]+ and [A1 + H]+ ions, etc. The combined MSPD and HPLC-DAD-MS method was suitable for quantitative and qualitative determination of the isoflavonoids in R. astragali.     

Determination of carphedon in human urine by solid-phase microextraction using capillary gas chromatography with nitrogen-phosphorus detection

Carphedon is a phenyl derivative of nootropil and is effective in increasing physical endurance and cold resistance, and is used for amnesia treatment. Carphedon was extracted from human urine samples by solid-phase microextraction with a 65 microns carbowax-divinylbenzene-coated fiber. This analysis was performed by using capillary gas chromatography with nitrogen-phosphorus detection and optimized at pH 9.6, 30% NaCl, immersion time 10 min and desorption in the GC injector at 250 degrees C for 3 min. The regression equation for carphedon showed good linearity in the range from 0.1 to 10 micrograms ml-1 for human urine samples. The limit of detection was 0.01 microgram ml-1. The developed method is more sensitive and simpler in sample preparation than liquid-liquid extraction and can be applied to doping analysis for stimulants.     

Determination of tobacco alkaloids by gas chromatography with nitrogen-phosphorus detection

An improved method, gas chromatography (GC) with nitrogen-phosphorus detection (NPD), has been used for determination of alkaloids in green and cured tobacco. Tobacco alkaloids of interest included nicotine, nornicotine, myosmine, anabasine, and anatabine. Tobacco samples were treated with a small quantity of aqueous ammonia solution to "loosen" tobacco tissue and to adjust pH, then extracted with solvent. The composition of the extraction solvent solution affected recoveries of the alkaloids, particularly nornicotine, and also contributed to other phenomena such as carry-over in the injection liner and "quenching" of the nitrogen-phosphorus detector. Use of a packed injection liner (e.g. with Carbowax-KOH on Chromosorb) to reduce carry-over was studied. Quenching of the nitrogen-phosphorus detector was eliminated by reducing the injection volume (i.e. increasing the split ratio), by use of a packed injection liner, and by reducing the amount of pretreatment with aqueous ammonia. A narrow bore capillary column (i.e. 0.18 mm id) was used to improve sensitivity and resolution and to increase the speed of GC analysis. An internal standard, 2,4'-dipyridyl, was used for quantitative measurement of these tobacco alkaloids.     

Determination of minor and trace volatile compounds in wine by solid-phase extraction and gas chromatography with mass spectrometric detection

A new method for the quantitative determination of important wine odorants has been developed. The wine (50 ml) is extracted in a 200 mg solid-phase extraction (SPE) cartridge filled with Lichrolut-EN resins from Merck. The elution is carried out with 1.3 ml of dichloromethane. These extracts are directly analyzed by GC-Ion Trap-MS without further concentration. Twenty-seven important wine odorants, such as volatile phenols, vanillin derivatives, aliphatic lactones, nor-isoprenoids, minor esters and terpenols, can be quantitatively determined in a single gas chromatography-mass spectrometry (GC-MS) run. The recoveries in the SPE isolation are in good agreement with those expected from the calculation of breakthrough volumes from solid-liquid distribution coefficients and are higher than 90%, except for guaiacol, vanillin, 2,6-dimethoxyphenol and 4-vinylphenol. In most cases, precision is below 10%. Method linearity is satisfactory, with r2 higher than 0.99 in all cases. The analysis of spiked samples has shown that there is good agreement between the real mass of compound added to the wine and that determined by analysis. In all cases detection limits are below the odor detection threshold of the compounds, and the calibrated interval covers the natural range of occurrence of the compounds in wine.     

Determination of phenolic compounds in wines by novel matrix solid-phase dispersion extraction and gas chromatography/mass spectrometry

A novel matrix solid-phase dispersion (MSPD) extraction method was developed to extract simultaneously 23 phenolic compounds from wine samples prior to determination by gas chromatography with mass spectrometric detection in the selected ion monitoring mode. Different parameters of the MSPD technique such as dispersant solid-phase, eluting solvent, and sample ionic strength and pH were optimized. The optimized MSPD procedure requires a small volume of wine (1 mL), commercial silica gel (1.5 g) as dispersant solid-phase and a small volume of ethyl acetate (5 mL) as eluting solvent. Under these conditions, the extraction of the studied compounds was almost complete (mean values of recoveries between 87 and 109%) in a short time (15 min). Moreover, satisfactory standard deviations of repeatability (RSD<9% in most cases), linear regression coefficients (r(2)>0.993) and detection limits (<8 microg/L) confirm the usefulness of the methodology for routine monitoring of the concentration of individual phenolic antioxidants in wines. Application was illustrated by analysis of different wine samples.     

Determination of pesticide residues in soil by modified matrix solid-phase dispersion and gas chromatography

Modified matrix solid-phase dispersion (MMSPD) and gas chromatography have been developed for quantitative analysis of various classes of pesticides (pirimicarb, metalaxyl, metolachlor, isopropalin and pendimethalin) in soil. MMSPD used Florisil as dispersant and acetone as solvent. Determination was carried out by gas chromatography with nitrogen-phosphorus detection (GC-NPD). The effect of the residence time of pesticides in soil on the recoveries was studied. MMSPD was compared with continuous liquid-solid extraction (LSE). MMSPD had good extraction efficiency and cleanup efficiency and the extract obtained could be directly subjected to GC analysis without further purification. The method gave recoveries ranging from 93% to 100% with relative standard deviations (RSDs) lower than 10%. The limits of detection (LODs) ranged from 0.2 to 2.0 ng g(-1).     

Determination of thiodyglycol in groundwater using solid-phase extraction followed by gas chromatography with mass spectrometric detection in the selected-ion mode

A highly sensitive analytical procedure is described for determining thiodiglycol in groundwater. Samples are initially fortified with 3,3'-thiodipropanol (surrogate), then both species are extracted using sequential solid-phase extraction with both C18 and Ambersorb 572 columns. The C18 column, which removes extraneous groundwater components, is discarded; the Ambersorb 572 column is dried thoroughly before eluting polar components with a small volume of dichloromethane. The extract is taken to dryness using dry flowing nitrogen, and the resulting residue is derivatized using N-(tert.-butyldimethylsilyl)-N-methyltrifluoroacetamide and pyridine. The derivatized products are diluted to a final volume with toluene, chromatographed using a fused-silica capillary column, and detected with a quadrupole mass spectrometric detector in its selected-ion mode. Two independent, statistically unbiased, procedures were used to evaluate the detection limits for thiodiglycol; the values ranged between 4 and 16 microg(-1) groundwater.     

Sample preparation methods to analyze fipronil in honey by gas chromatography with electron-capture and mass spectrometric detection

Several sample preparation methods have been assayed to analyze residues of fipronil in honey. After diluting the honey, liquid-liquid extraction (LLE) with organic solvents, and solid-phase extraction (SPE) on commercial cartridges or Florisil-packed column have been tested at three concentration levels: 0.01, 0.1 and 1 mg/kg. LLE with n-hexane or SPE on a Florisil column resulted to be the most suitable procedures to analyze fipronil at trace concentrations. Fipronil was quantified by gas chromatography (GC) with electron-capture detection (ECD) or mass spectrometric (MS) detection after conventional or matrix-matched calibration. The detection limit of fipronil in honey samples was below 1 microg/kg. The degradation of fipronil in honey has also been studied, being identified three minor degradation products in the extracts.     

Determination of lewisite oxide in soil using solid-phase microextraction followed by gas chromatography with flame photometric or mass spectrometric detection

A rapid, sensitive, and convenient method is described for determining Lewisite oxide in soil. Samples are initially fortified with phenylarsine oxide (surrogate), then both species are extracted using ascorbic acid solutions containing 1,3-propanedithiol (derivatizing reagent). The corresponding filtered supernatant is sampled using a solid-phase microextraction fiber. Collected analytes are thermally desorbed in a heated gas chromatographic inlet, separated using fused-silica capillary columns ("primary" and "confirmatory"), and detected with either a mass spectrometric (selected ion monitoring mode) or flame photometric (sulfur-selective mode) detector. Two independent statistically-unbiased procedures were used to evaluate the detection limit for Lewisite oxide; the values range between 0.1 and 0.5 microg g(-1) soil.     

Determination of fungicides in natural waters using solid-phase microextraction and gas chromatography coupled with electron-capture and mass spectrometric detection

This study develops a method for the analysis of seven fungicides in environmental waters, using solid-phase microextraction (SPME). The analyzed compounds--dicloran, chlorothalonil, vinclozolin, dichlofluanid, captan, folpet and captafol--belong to different classes of chemical compound (chloroanilines, sulphamides, phthalimides and oxazolidines) and are used mainly in agriculture and as antifouling paints. Their determination was carried out by gas chromatography with electron-capture and mass spectrometric detection. To perform SPME, four types of fibre have been assayed and compared: polyacrylate (85 microm), polydimethylsiloxane (100 and 30 microm), carbowax-divinylbenzene (CW-DVB 65 microm) and polydimethylsiloxane-divinylbenzene (65 microm). The main parameters affecting the SPME process such as pH, salt additives, methanol content, memory effect, stirring rate and adsorption-time profile were studied. The method was developed using spiked natural waters such as ground water, sea water, river water and lake water in a concentration range of 0.1-10 microg/l. Limits of detection of studied compounds were determined in the range of 1-60 ng/l, by using electron-capture and mass spectrometric detectors. The recoveries of all fungicides were in relatively high levels (70.0-124.4%) and the average R2 values of the calibration curves were above 0.990 for all the analytes. The SPME conditions were finally optimized in order to obtain the maximum sensitivity. The potential of the proposed method was realized by applying it to the trace-level screening determination of fungicides and antifouling compounds in sea water samples originating from various Greek marinas.     

Determination of carbamate insecticides in Chinese medicinal herbs by gas chromatography with a nitrogen-phosphorus detector

A simplified method for determining carbamate insecticides (including metolcarb, isoprocarb, fenobucarb, carbofuran, pirimicarb, and carbaryl) in Chinese medicinal herbs (White Peony Alba, Red Peony Root, and Baical Skullcap Root) is described. Standards were fortified into Chinese medicinal herbs at 3 levels (0.05-0.5 mg/kg). The carbamates were extracted with dichloromethane in a Soxhlet apparatus and analyzed by gas chromatography with a nitrogen-phosphorus detector. The results showed average recoveries between 80.77 and 104.56%. The method evidenced good robustness, accuracy, and precision for monitoring carbamates in Chinese medicinal herb samples, and it is a suitable alternative to replace the currently dedicated analytical systems. The minimum detectable amount ranged from 3.0 x 10(-10) to 5.0 x 10(-10)g, and the limit of quantification was 0.05 mg/kg. The method is rapid, simple, sensitive, and reproducible, and it can be conveniently used as a low-cost, rapid method for measuring the carbamate insecticide contamination of Chinese medicinal herbs.     

Determination of organophosphorous flame retardants in fish tissues by matrix solid-phase dispersion and gas chromatography

Organophosphate esters (OPEs), utilized as flame retarding agents and/or plasticizers, are almost ubiquitous in environmental compartments, and biota and foods could be contaminated by bioaccumulation or during the treatment processes. A multiresidue method is proposed for the determination of 13 OPEs in fish tissues: analytes were simultaneously extracted and purified using the matrix solid phase dispersion technique and then determined by gas chromatography with nitrogen–phosphorus detection. The main parameters affecting extraction yield and selectivity, such as the type of dispersant material, clean-up co-sorbent, rinse and elution solvents, were evaluated to obtain lipid-free extracts and quantitative recoveries for OPEs. Under optimal conditions, 0.5 g of samples was dispersed with 2 g Florisil and 1 g anhydrous sodium sulphate and transferred to a solid phase extraction cartridge containing 1 g alumina. The lipids were removed using 5 mL n-hexane/dichloromethane (1:1) and analytes were recovered with 10 mL n-hexane/acetone (6:4) and directly analysed. The method developed provided recoveries between 70 and 110% for different kinds of fish, and the day-to-day variability was between 1 and 9%. This procedure constitutes the first analytical method for the analysis of OPEs in a food matrix and it is applicable to analyse a large number of samples to evaluate the occurrence and sources of OPEs in biota and foods.     

Determination of methanol in cosmetics by headspace and multidimensional gas chromatography with mass spectrometric detection

A novel, reliable, and robust analytical method using headspace and multidimensional GC coupled to MS was successfully developed for determining the methanol content in cosmetics. The methanol was quantitatively analyzed and confirmed by heart-cutting multidimensional GC and mass selective detection in full scan mode. The average recovery was 99.8% with an RSD of 4.3%; the LOQ was 5 mg/kg. The proposed method showed good accuracy and precision while minimizing erroneous results due to false positives compared with conventional single-column GC analysis.     

Determination of natural and synthetic estrogens in water by gas chromatography with mass spectrometric detection

A procedure for the determination of six natural and synthetic estrogens (diethylstilbestrol, estrone, 17beta-estradiol, mestranol, 17alpha-ethinylestradiol and estriol) in water samples is described. Samples, up to 2000 ml, were concentrated using Oasis HLB solid-phase extraction cartridges. Analytes were derivatized with N-methyl-N-(trimethylsilyl)trifluoroacetamide and determined by GC-MS or GC-MS-MS. The reactivity of several silylation reagents versus aliphatic and aromatic hydroxyl groups contained in the structure of the selected analytes was evaluated. Influence of parameters such as sample pH, nature of the water samples and derivatization conditions on the performance of the whole analytical procedure was systematically studied. Under optimal conditions, quantification limits between 1 and 3 ng/l were achieved for the determination of the considered estrogens in sewage water.     

Determination of polyamines in human erythrocytes by capillary gas chromatography with nitrogen-phosphorus detection

A capillary gas chromatographic method with nitrogen-phosphorus detection is used to determine simultaneously 1,3-diaminopropane, putrescine, cadaverine, spermidine and spermine in human erythrocytes. The compounds are isolated by adsorption on silica and converted into their heptafluorobutyryl derivatives. We give quality-control data and (age-dependent) normal values for 48 apparently healthy controls.