Injection port derivatization following ion-pair hollow fiber-protected liquid-phase microextraction for determining acidic herbicides by gas chromatography/mass spectrometry

Injection port derivatization following ion-pair hollow fiber-protected liquid-phase microextraction (LPME) for the trace determination of acidic herbicides (2,4-dichlorobenzoic acid, 2,4-dichlorophenoxyacetic acid, 2-(2,4-dichlorophenoxy)propionic acid, 3,5-dichlorobenzoic acid, 2-(2,4,5-trichlorophenoxy)propionic acid) in aqueous samples by gas chromatography/mass spectrometry (GC/MS) was developed. Prior to GC injection port derivatization, acidic herbicides were converted into their ion-pair complexes with tetrabutylammonium chloride in aqueous samples and then extracted by 1-octanol impregnated in the hollow fiber. Upon injection, ion pairs of acidic herbicides were quantitatively derivatized to their butyl esters in the GC injection port. Thus, several parameters related to the derivatization process (i.e., injection temperature, purge-off time) were evaluated, and main parameters affecting the hollow fiber-protected LPME procedure such as extraction organic solvent, ion-pair reagent type, pH of aqueous medium, concentration of ion-pair reagent, sodium chloride concentration added to the aqueous medium, stirring speed, and extraction time profile, optimized. At the selected extraction and derivatization conditions, no matrix effects were observed. This method proved good repeatability (RSDs <12.3%, n = 6) and good linearity (r2 > or = 0.9939) for spiked deionized water samples for five analytes. The limits of detection were in the range of 0.51-13.7 ng x L(-1) (S/N =3) under GC/MS selected ion monitoring mode. The results demonstrated that injection port derivatization following ion-pair hollow fiber-protected LPME was a simple, rapid, and accurate method for the determination of trace acidic herbicides from aqueous samples. In addition, this method proved to be environmentally friendly since it completely avoided open derivatization with potentially hazardous reagents.     

Fully automated dynamic in-syringe liquid-phase microextraction and on-column derivatization of carbamate pesticides with gas chromatography/mass spectrometric analysis

A new fully automated dynamic in-syringe liquid-phase microextraction (LPME) and on-column derivatization approach, with gas chromatography/mass spectrometric (GC/MS) analysis, was developed to determine carbamate pesticides from water samples. With the use of a CTC CombiPal autosampler and its associated Cycle Composer software, a sample preparation-GC/MS method was enabled that allowed sample extraction, extract injection, and analyte derivatization to be carried out completely automatically. Optimization of extraction parameters was carried out by orthogonal array design which required a minimum of 16 experiments; the entire set of experiments was performed completely automatically and consecutively without any human intervention. Low limits of detection ranging from 0.05 to 0.1 μg/L were achieved for the carbamates. Effective enrichment of the analytes at a low concentration of 0.01 mg/L was also achieved (enrichment factors of between 57 and 138). The precision of the optimized method was satisfactory, with relative standard deviations of <6.0% (n = 6). High relative recoveries of between 81 and 125% were obtained when the method was applied to the analysis of real water samples, indicating that the sample matrix had little effect on the developed method. This automated dynamic in-syringe LPME approach demonstrated the feasibility of a complete analytical system comprising sample preparation and GC/MS that might be operated onsite, fully automatically without human intervention.     

Simultaneous analysis of multiple classes of antibiotics by ion trap LC/MS/MS for assessing surface water and groundwater contamination

Solid-phase extraction (SPE) and liquid chromatography in combination with ion trap mass spectrometry (LC/MS/MS) conditions were optimized for the simultaneous analysis of 13 antibiotics belonging to multiple classes and caffeine in 3 different water matrixes. The single-cartridge extraction step was developed using a reversed-phase cartridge, resulting in recoveries for the 14 compounds ranging from 71 to 119% with relative standard deviations of 16% or lower. The analytes were separated in one chromatographic run, and the SPE-LC/MS/MS detection limits ranged from 0.03 to 0.19 microg/L. The SPE procedure was validated in groundwater, surface water, and wastewater. The analysis of samples from each of the three water matrixes revealed clindamycin (1.1 microg/L) in surface water and multiple antibiotics in wastewater (0.10-1.3 microg/L). The use of identification points to unambiguously assign the identity of antibiotics in various water matrixes was applied to an ion trap data-dependent scanning method, which simultaneously collects full scan and full scan MS/MS data for the unequivocal identification of target analytes.     

Development of a solid-phase microextraction GC-NPD procedure for the determination of free volatile amines in wastewater and sewage-polluted waters.

An analytical procedure for the determination of free volatile C1-C6 amines in aqueous matrixes has been developed and applied to their determination in waste-water, primary and secondary effluents, and sewage-polluted river samples. The developed analytical procedure involves headspace sampling using solid-phase microextraction with a poly(dimethylpolysiloxane) coating (100 microns) followed by GC-NPD determination and GC/MS confirmation using a tailor-made PoraPLOT amines capillary GC column for volatile amines. Procedural detection limits were compound dependent but ranged from 3 to 56 micrograms L-1, being close to or lower than the odor threshold concentration, and the reproducibility was ca. 15% (N = 5) in real water samples. The developed analytical procedure is solvent free, cost-effective (no cryogenic trap needed), and faster than existing methods because no derivatization step is involved in the determination. Linearity was compound dependent but ranged at least from 50 to 600 micrograms L-1.     

Determination of polar drug residues in sewage and surface water applying liquid chromatography-tandem mass spectrometry

A simple and rapid method is presented for the trace-level analysis of 10 polar pharmaceutical residues in various types of water samples from the aquatic environment. Using this method, the pharmaceuticals and several drug metabolites can be analyzed in drinking and surface waters and in wastewater (treated and untreated sewage) at concentrations down to 0.01 microg/L. Samples are prepared by a simple in situ derivatization enabling the preconcentration of very polar metabolites by automated solid-phase extraction. The analytes were separated by liquid chromatography with tandem mass spectrometric detection and quantified by comparison with an internal standard. Limits of quantification were between 0.01 and 0.02 microg/L for three phenazone-type pharmaceuticals, six of their metabolites, and the antiepileptic drug carbamazepine. Except for dimethylaminophenazone, recoveries for all analytes were between 87 and 117% for raw and purified sewage, groundwater, and surface and drinking water. Investigations of some environmental samples revealed that sewage and surface water treatment causes a slight reduction of the concentrations of some analytes whereas other compounds were persistent during water treatment. Thus, some compounds were detected at the low-microgram per liter level in sewage effluents of wastewater treatment plants in Berlin (Germany) and were also found at high-nanogram per liter concentrations in Berlin surface water samples.     

Simultaneous determination of estrogenic short ethoxy chain nonylphenols and their acidic metabolites in water by an in-sample derivatization/solid-phase microextraction method

An in-sample derivatization headspace solid-phase microextraction method has been developed for the simultaneous determination of nonylphenol, nonylphenol mono- and diethoxylates (NP, NP1EO, NP2EO), and their acidic metabolites (NPlEC, NP2EC) in water. The analytical procedure involves derivatization of NPEOs and NPECs to their methyl ethers--esters with dimethyl sulfate/NaOH and further headspace (HS) solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) determination. Parameters affecting both derivatization efficiency and headspace SPME procedure, such as the selection of the SPME coating, derivatizationextraction time, temperature and ionic strength were optimized. The commercially available Carbowax-divinylbenzene (CW-DVB) fiber appears to be the most suitable for the simultaneous determination of both NPEOs-NPECs. Run-to-run precision of the in-sample derivatization/HS-SPME-GC/MS method gave relative standard deviations between 8 and 18%. The method was linear for NP over 2 orders of magnitude, and detection limits were compound dependent but ranged from 20 to 1500 ng/L. The SPME procedure was compared with a solid-phase extraction SPE-GC/MS method for the analysis of NPEOs-NPECs in water samples and good agreement was obtained. Therefore, in-sample derivatization HS-SPME-GC/MS can be used as a method for the simultaneous determination of short ethoxy chain nonylphenols and their acidic metabolites in water.     

Two trace analytical methods for determination of hydroxylated PCBs and other halogenated phenolic compounds in eggs from Norwegian birds of prey

Two new trace analytical methods are presented for identification and quantification of phenolic compounds in complex biological matrixes such as bird of prey eggs. One method is based on derivatization with methyl chloroformate prior to GC/high-resolution MS (HRMS) analysis in electron impact ionization mode. Alternatively, the underivatized phenolic analytes were separated and detected by HPLC coupled to time-of-flight MS (TOF-MS) in the negative ion electrospray ionization mode. For both methods, the egg samples were homogenized and dried with acidified sodium sulfate, cold column-extracted, and cleaned up by gel permeation chromatography and subsequently a Florisil column. Recovery rates for pentachlorophenol (PCP), tetrabromobisphenol A (TBBPA), and selected hydroxylated PCBs (HO-PCBs) from spiked hen's eggs (spiking level 1 ng/g of wet weight (ww)) were in the range of 56-98% for the HPLC/MS method and 57-108% for GC/MS including derivatization. Typical detection limits of the HPLC/TOF-MS method were 5 pg/g ww (1-2 pg injected) for HO-PCBs and PCP and 20 pg/g ww (3 pg injected) for TBBPA. The GC/HRMS method achieved detection limits of approximately 1 pg/g ww in predatory bird eggs for all analytes (0.2 pg injected for derivatized TBBPA and 0.05 pg injected for derivatized HO-PCBs and PCP). Eight eggs from four different Norwegian predatory bird species were analyzed. The concentrations determined with the two different quantification methods corresponded well with each other. PCP and TBBPA were found in all samples at concentrations up to 1350 and 13 pg/g ww, respectively (GC/HRMS values). A total of 55 penta- to nonachloro-HO-PCB congeners were detected in the eight eggs, 10 of those could be structurally identified. The maximum HO-PCB congener concentration was found for 4-HO-CB 187 in a peregrine falcon egg with estimated 388 pg/g ww. Another peregrine falcon egg was highest contaminated with sum HO-PCBs (estimated 2.1 ng/g ww). This level was 1.2 per thousand of the sum PCBs value for the same egg. Furthermore, indications were found that the HO-PCB congener distribution pattern could be species specific for predatory birds.     

Sol-gel capillary microextraction

Sol-gel capillary microextraction (sol-gel CME) is introduced as a viable solventless extraction technique for the preconcentration of trace analytes. To our knowledge, this is the first report on the use of sol-gel-coated capillaries in analytical microextraction. Sol-gel-coated capillaries were employed for the extraction and preconcentration of a wide variety of polar and nonpolar analytes. Two different types of sol-gel coatings were used for extraction: sol-gel poly(dimethylsiloxane) (PDMS) and sol-gel poly(ethylene glycol) (PEG). An in-house-assembled gravity-fed sample dispensing unit was used to perform the extraction. The analysis of the extracted analytes was performed by gas chromatography (GC). The extracted analytes were transferred to the GC column via thermal desorption. For this, the capillary with the extracted analytes was connected to the inlet end of the GC column using a two-way press-fit fused-silica connector housed inside the GC injection port. Desorption of the analytes from the extraction capillary was performed by rapid temperature programming (at 100 degrees C/min) of the GC injection port. The desorbed analytes were transported down the system by the helium flow and further focused at the inlet end of the GC column maintained at 30 degrees C. Sol-gel PDMS capillaries were used for the extraction of nonpolar and moderately polar compounds (polycyclic aromatic hydrocarbons, aldehydes, ketones), while sol-gel PEG capillaries were used for the extraction of polar compounds (alcohols, phenols, amines). The technique is characterized by excellent reproducibility. For both polar and nonpolar analytes, the run-to-run and capillary-to-capillary RSD values for GC peak areas remained under 6% and 4%, respectively. The technique also demonstrated excellent extraction sensitivity. Parts per quadrillion level detection limits were achieved by coupling sol-gel CME with GC-FID. The use of thicker sol-gel coatings and longer capillary segments of larger diameter (or capillaries with sol-gel monolithic beds) should lead to further enhancement of the extraction sensitivity.     

The use of slurry sampling for the determination of manganese and copper in various samples by electrothermal atomic absorption spectrometry

Manganese and copper in multivitamin-mineral supplements and standard reference materials were determined by slurry sampling electrothermal atomic absorption spectrometry. Slurries were prepared in an aqueous solution containing Triton X-100. The effects of different parameters such as ratio of solid to liquid phase volume, total slurry volume and addition of Triton X-100 as a dispersant on the analytical results were investigated. The graphite furnace programs were optimized for slurry sampling depending on the analytes and their concentrations in the samples. The linear calibration method with aqueous standard solutions was used for the quantification. At optimum experimental conditions, R.S.D. values were below 5%. The analytes were determined in the limits of 95% confidence level with respect to certified values in coal and soil standard reference materials and to those found by wet-digestion in multivitamin-mineral supplements. Detection limits (3delta) for Mn and Cu were 0.10 microg L(-1) and 1.82 microg L(-1) for 10 microL coal standard reference material slurry, respectively.     

Speciation of alkyllead and inorganic lead by derivatization with deuterium-labeled sodium tetraethylborate and SPME-GC/MS

A method for full speciation and determination of alkyllead and inorganic lead(II) in aqueous samples was developed. This was accomplished by in situ derivatization with deuterium-labeled sodium tetraethylborate NaB(C2D5)4 (DSTEB). The derivatization was carried out directly in the aqueous sample and the derivatives were extracted from the headspace by a solid-phase microextraction (SPME) fiber. The extracted analytes were then transferred to a GC/MS or a GC/FID for separation and detection. The research presented demonstrates that SPME and the derivatization reagent DSTEB can be used successfully for the speciation of Pb2+, Pb(CH3)3+, Pb(C2H5)3+, and Pb(C2H5)4 in water samples. All derivatives, Pb(C2D5)4, (CH3)3Pb(C2D5), (C2H5)3Pb(C2D5), and Pb(C2H5)4, are separated using an SBP-5 column. This method was applied to monitor degradation of tetraethyllead in water. This is the first report of ethylation by DSTEB for full speciation of methyllead, ethyllead, and inorganic lead compounds. This approach can be extended to other organometallic compounds as demonstrated for ethyltin speciation. This full speciation method will aid in monitoring occurrence, pathways, toxicity, and biological effects of these compounds in the environment. It is easily adopted for field analysis.     

In situ derivatization/solid-phase microextraction for the determination of haloacetic acids in water

An in situ derivatization solid-phase microextraction method has been developed for the determination of haloacetic acids (HAAs) in water. The analytical procedure involves derivatization of HAAs to their methyl esters with dimethyl sulfate, headspace sampling using solid-phase microextraction (SPME), and gas chromatography-ion trap mass spectrometry (GC/ITMS) determination. Parameters affecting both derivatization efficiency and head-space SPME procedure, such as the selection of the SPME coating, derivatization-extraction time and temperature, and ionic strength, were optimized. The commercially available Carboxen-poly(dimethylsiloxane) (CAR-PDMS) fiber appears to be the most suitable for the determination of HAAs. Moreover, the formation of HAA methyl esters was dramatically improved (up to 90-fold) by the addition of tetrabutylammonium hydrogen sulfate (4.7 micromol) to the sample as ion-pairing agent in the derivatization step. The precision of the in situ derivatization/HS-SPME/GC/ITMS method evaluated using an internal standard gave relative standard deviations (RSDs) between 6.3 and 11.4%. The method was linear over 2 orders of magnitude, and detection limits were compound-dependent, but ranged from 10 to 450 ng/L. The method was compared with the EPA method 552.2 for the analysis of HAAs in various water samples, and good agreement was obtained. Consequently, in situ derivatization/HS-SPME/GC/ITMS is proposed for the analysis of HAAs in water.     

Low part per trillion determination of reactive alkanethiols in wastewater by in situ derivatization-solid-phase microextraction followed by GC/MS

A solid-phase microextraction (SPME) procedure for the simultaneous determination of volatile alkanethiols (i.e., methane-, ethane-, propanethiol) and dihydrogen sulfide in aqueous samples as stable thioethers followed by GC/MS determination was developed. Accordingly, N-ethylmaleimide as derivatization reagent in the aqueous phase was used for the first time, improving the analyte stability and method sensitivity in comparison to the determination of free forms. Thus, pH of the aqueous medium, reaction time, and derivatization reagent concentration have been evaluated, and the main parameters affecting the SPME process (i.e., coating selection, extraction mode and time profile, extraction and desorption temperatures) optimized. At the selected derivatization and extraction conditions, the proposed method provided no matrix effect either in the derivatization reaction or in the microextraction steps. RSD values were lower than 11% and LODs from 0.74 to 5.2 ng L(-1). The developed procedure was successfully applied to different water and wastewater samples, where dihydrogen sulfide and some of the target alkanethiols were identified at low-microgram per liter concentrations.     

Direct coupling of ionic liquid based single-drop microextraction and GC/MS

The use of ionic liquids as extracting media in single-drop liquid-phase microextraction (SDME) and its direct coupling to gas chromatography/mass spectrometry (GC/MS) is presented. For this purpose, a new removable interface that enables the introduction of the extracted analytes into the GC system, while preventing the ionic liquid from entering the column, has been developed. The determination of three representative pollutants in water samples has been used as a model analytical problem in order to demonstrate the feasibility of the proposed interface. The analytes (dichloromethane, p-xylene, and n-undecane) were coextracted from the aqueous sample in a 2-microL drop of 1-butyl-3-methylimidazolium hexaflourophosphate. Then, the syringe used to perform the SDME was directly introduced into the interface, which was held at 140 degrees C in order to achieve a complete volatilization of the target compounds. After the injection, the ionic liquid was retained in the interface, while a carrier gas transferred the volatilized analytes into the GC inlet. The optimization of the operational variables affecting the new interface (temperature, carrier flow rate, sample volume and injection technique) was accomplished. The analytes could be determined with detection limits in the low-nanogram per milliliter concentration range, and the relative standard deviations were between 3.3 and 4.4%.     

Determination of methionine and selenomethionine in yeast by species-specific isotope dilution GC/MS

A method for the simultaneous determination of methionine (Met) and selenomethionine (SeMet) in yeast using species-specific isotope dilution (ID) gas chromatography/mass spectrometry (GC/MS) is described. Samples were digested by refluxing for 16 h with 4 M methanesulfonic acid. Analytes were derivatized with methyl chloroformate and extracted into chloroform for GC/MS analysis. In addition to use of commercially available 13C-enriched Met and SeMet spikes for species specific ID analysis, a 74Se-enriched SeMet spike was also available for comparison of results. In selective ion monitoring mode, the intensities of ions at m/z 221, 222, 269, 270, and 263 were used to calculate the 221/222, 269/270, and 269/263 ion ratios for quantification of Met and SeMet. Concentrations of 5959 +/- 33 and 3404 +/- 12 microg g(-1) (one standard deviation, n = 6) with relative standard deviations of 0.55 and 0.36% for Met and SeMet, respectively, were obtained using 13C-enriched spikes. A concentration of 3417 +/- 8 microg g(-1) (one standard deviation, n = 6) was obtained using the 74Se-enriched SeMet spike. The concentration of SeMet measured in the yeast is equivalent to 66.43 +/- 0.24% of total Se and 30.31 +/- 0.11% of total Met is in the form of SeMet. Method detection limits (three times the standard deviation) of 3.4 and 1.0 microg g(-1) were estimated for Met and SeMet, respectively, based on a 0.25-g subsample of yeast with 1 mL of extract used for derivatization. A similar concentration of 5930 +/- 29 microg g(-1) (one standard deviation, n = 4) for Met and a lower concentration of 2787 +/- 49 microg g(-1) (one standard deviation, n = 4) for SeMet were obtained for this yeast sample using species-specific ID analysis based on GC/MS with 13C-enriched Met and SeMet spikes when a 2-h open microwave digestion approach using 8 M methanesulfonic acid was used.     

On-line solid-phase extraction with surfactant accelerated on-column derivatization and micellar liquid chromatographic separation as a tool for the determination of biogenic amines in various food substrates

A sensitive method was developed for the determination of biogenic amines at very low levels by combining solid phase extraction (SPE) and derivatization on-line with HPLC. The on-line derivatization and SPE were performed simultaneously on a commercially available ODS guard column, which was installed instead of the filling loop on the HPLC apparatus. Resolution of the peaks and quantification was further enhanced with micellar liquid chromatography and sensitization of the benzene ring absorption at 254 nm. Detection limits of the benzoyl derivatives of biogenic amines were in the vicinity of 0.1 microg L(-)(1), which is even lower than those obtained by fluorescence detection and is unparallel to any other UV approach. The correlation coefficients of determinations were 0.9850-0.9998. The method was applied to the determination of Biogenic amines, that is, putrescine, cadaverine, agmatine, tyramine, tryptamine, phenylethylamine, spermine, spermidine and histamine in fish, chicken, and wine samples. Recovery of the proposed method ranged from 94 to 106%.     

Speciation of inorganic lead and ionic alkyllead compounds by GC/MS in prescreened rainwaters

A simple and novel screening method for lead compounds in environmental waters is proposed. The analytes, in an acetic medium, are sorbed on a C60 fullerene column as diethyldithiocarbamate complexes and subsequently eluted with isobutyl methyl ketone (IBMK), the lead being determined by flame atomic absorption spectrometry. The screening method acts as filter and indicates whether the target analytes are present above or below the detection limit of the method (0.5 ng/mL), giving no false positives. Positive samples were speciated by GC/MS, using a flow system similar to that of the screening method. Lead(II) and ionic di- and trialkyllead are derivatized with a Grignard reagent. Both methods use similar chemical and flow variables except for the eluent, IBMK in the screening method and n-hexane in the speciation method. The GC/MS speciation method is very sensitive; it exhibits a linear range of 0.02-5 ng/mL, and detection limits of 1-4 ng/L are achieved. Also, its repeatibility, as RSD, is less than 6%. The method was applied to the speciation of Pb2+ and di- and trialkyllead in positive prescreened rainwater samples from three different urban areas.     

A biosorption system for metal ions on Penicillium italicum-loaded on Sepabeads SP 70 prior to flame atomic absorption spectrometric determinations

A solid phase extraction (SPE) preconcentration system, coupled to a flame atomic absorption spectrometer (FAAS), was developed for the determination of copper(II), cadmium(II), lead(II), manganese(II), iron(III), nickel(II) and cobalt(II) ions at the microg L(-1) levels on Penicillium italicum-loaded on Sepabeads SP 70. The analytes were adsorbed on biosorbent at the pH range of 8.5-9.5. The adsorbed metals were eluted with 1 mol L(-1) HCl. The influences of the various analytical parameters including pH of the aqueous solutions, sample volume, flow rates were investigated for the retentions of the analyte ions. The recovery values are ranged from 95-102%. The influences of alkaline, earth alkaline and some transition metal ions were also discussed. Under the optimized conditions, the detection limits (3s, n=21) for analytes were in the range of 0.41microg L(-1) (cadmium) and 1.60microg L(-1) (iron). The standard reference materials (IAEA 336 Lichen, NIST SRM 1573a Tomato leaves) were analyzed to verify the proposed method. The method was successfully applied for the determinations of analytes in natural water, cultivated mushroom, lichen (Bryum capilare Hedw), moss (Homalothecium sericeum) and refined table salt samples.     

Analysis of perchlorate in water by reversed-phase LC/ESI-MS/MS using an internal standard technique

A new method was developed for the analysis of perchlorate in water by using reversed-phase liquid chromatograhy/electrospray ionization-mass spectrometry/mass spectrometry (LC/ESI-MS/MS) in the negative ESI mode. Selective and sensitive perchlorate detection was obtained by monitoring the 35ClO4- --> 35ClO3- and 37ClO4- --> 37ClO3- mass transitions. The 35ClO4- --> 35ClO3- transition was quantitated against the internal standard oxygen-labeled sodium perchlorate (NaCl18O4). Sample pretreatment for the removal of major common anions and dissolved metal ions along with internal standard quantitation sufficiently compensated for ion suppression caused by the matrix. The 37ClO4- --> 37ClO3- transition was examined to provide additional specificity. The method sensitivity, accuracy, and precision were investigated by analyzing fortified blank samples, field samples, and performance evaluation samples. The results (1.01-13.5 microg/L) for the proficiency evaluation samples differed from the certified values (1.04-14.1 microg/L) by 3-18%. The developed reversed-phase LC/ESI-MS/MS method was rapid, accurate, and reproducible. The calculated method detection limits were 0.007 microg/L for deionized reagent water and 0.009 microg/L for synthesized reagent water, respectively. The minimum reporting limit was conservatively set to 0.05 microg/L.     

Application of porous membrane-protected micro-solid-phase extraction combined with HPLC for the analysis of acidic drugs in wastewater

This report describes the use of a porous membrane-protected micro-solid-phase extraction (micro-SPE) procedure to extract acidic drugs from wastewater that are then determined by high-performance liquid chromatography with ultraviolet detection. The micro-SPE device consists of C18 sorbent held within a membrane envelope made of polypropylene. Ketoprofen and ibuprofen were selected as model compounds, and extraction parameters were optimized. Correlation coefficients of 0.9980 and 0.9953 were obtained for ketoprofen and ibuprofen, respectively, across a concentration range of 1-250 microg/L. Relative extraction recoveries were between 94 and 112%. The relative standard deviation of the analytical method ranged between 2 and 10%, respectively. The method detection limits for these target analytes in wastewater ranged from 0.03 to 0.08 microg/L. When compared to conventional solid-phase extraction (SPE), this new method showed better detection limits with good reproducibility. The results shows that this micro-SPE technique is a feasible alternative to multistep SPE for the extraction of analytes in complex samples.     

Determination of parabens and triclosan in indoor dust using matrix solid-phase dispersion and gas chromatography with tandem mass spectrometry

A simple sample preparation method for the determination of four parabens and triclosan in indoor dust is presented. Analytes were extracted from the sample and isolated from interfering species using the matrix solid-phase dispersion technique. After that, they were silylated and determined by gas chromatography combined to tandem mass spectrometry (GC/MS/MS). The influence of several factors on the yield and selectivity of the extraction was evaluated in detail. Under final working conditions, samples (0.5 g) were mixed with the same amount of anhydrous sodium sulfate and dispersed on 1.25 g of C18. This blend was transferred to the top of a polypropylene cartridge containing 2 g of Florisil. After removing less polar species with 10 mL of dichloromethane, analytes were recovered using 10 mL of acetonitrile. This extract was concentrated to 1 mL, derivatized, and injected in the GC/MS/MS system. Derivatization was carried out at 45 degrees C in 5 min using 100 microL of N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide. Quantification limits from 0.6 to 2.6 ng/g and absolute recoveries between 80 and 114% were achieved. Analysis of dust samples demonstrated the presence of the target species in indoor dust from private houses. The highest average concentration (702 ng/g) corresponded to triclosan.