Sequential Solid-phase Extraction Research Articles

Sequential combination of solid-phase sorbents to enhance the selectivity of organosulfur compounds for flavour analysis.

Flavour analysis remains challenging due to the range of selectivity demands, from the extraction of multiclass volatile compounds to the purification of low-concentration odourants (e.g. organosulfur compounds) amidst the high food matrix noise. In this study, the varying selectivities of solid-phase extraction (SPE) were leveraged upon for both multiclass and organosulfur compound analysis, using coffee as a model matrix. Polymeric SPE (Bond Elut ENV) was screened for significant (p<0.05) parameters affecting the recovery of 37 multiclass compounds, and the most influential parameters were optimised using a Box-Behnken design (elution solvent of 67:33 dichloromethane:ethyl acetate, loading pH of 4.8, and wash solvent of water). Following this, low-concentration organosulfur compounds which were challenging to detect in the complex coffee matrix were purified by adding a sequential SPE step for selectivity. A silver-based ligand-exchange SPE step (MetaSEP IC-Ag) was optimised for organosulfur compound recovery (wash solvents of dichloromethane and 43% acetonitrile in dichloromethane, elution solvent of 90mmol/L 1,4-dithiothreitol in dichloromethane). This was found to be complementary to polymeric SPE's matrix clean-up effect (which improved average organosulfur compound recovery by 5.45 times). Finally, both multiclass and sequential organosulfur extraction techniques demonstrated good performance in terms of reproducibility (1.0-9.0%) and linearity (R2>0.995), allowing for the detection of 3-mercapto-3-methylbutyl formate (3.741±0.387ng/mL) in coffee samples. In conclusion, this study highlights the potential for SPE to address a variety of complex flavour analysis demands with the appropriate selection and combination of solid-phases.

Changes in dissolved organic matter during water treatment by sequential solid-phase extraction and unknown screening analysis

Isolation of complex dissolved organic matter (DOM) from environmental water is a major challenge for unknown screening analysis by high-resolution mass spectrometry. In this study, DOM in process water during advanced drinking water treatment was fractionated sequentially by three solid-phase extraction (SPE) cartridges based on the polarity and charge of DOM molecules. By sequential SPE with unknown screening analysis, over 3000 DOM features were found in raw water, whereas around 2000 were obtained by a single SPE. The hydrophobic neutral (HPON) fraction contained CHO features with highest averaged molecular weight followed by hydrophobic acid (HPOA) and then hydrophilic acid (HPIA). The average degree of carbon double bond equivalents and carbon oxidation states indicated that the HPON fraction contained molecules that were more unsaturated and less oxidized than those of the HPOA and HPIA fractions. Ozone selectively decomposed (1) more unsaturated and less oxidized HPON features, (2) more unsaturated HPOA compounds, and (3) less oxidized HPIA molecules. Oxidation by-products were mostly HPON and HPIA compounds that were more oxidized than the decomposed molecules. During biological activated carbon (BAC) filtration, less oxidized HPON were preferentially removed, whereas HPOA were removed without selectivity. HPON and HPIA molecules with more oxidized character were found to be refractory to BAC treatment. HPON with more unsaturated and HPIA with more oxidized characters were decomposed by chlorine. Many types of HPIA decomposed during chlorination were the oxidation by-products of ozonation that were refractory to BAC treatment. Sequential SPE with unknown screening analysis provided previously unknown details of the molecular characteristics of DOM and its changes during advanced water treatment.

Optical Properties of Soil Dissolved Organic Matter Are Related to Acidic Functions of Its Components as Revealed by Fractionation, Selective Deuteromethylation, and Ultrahigh Resolution Mass Spectrometry.

The goal of this study was to establish a relationship between the optical properties of soil dissolved organic matter (DOM) and acidic functions carried out by its individual constituents. We obtained 12 fractions of DOM samples using sequential solid phase extraction on nonionic sorbent at steadily lowered pH values: 7, 5, 3, 2, which correspond to low bounds of pKa values of phenols, aliphatic, and aromatic carboxylic acids, and ketoacids. The structural studies were conducted with the use of NMR and selective deuteromethylation of isolated fractions coupled to ultrahigh resolution mass spectrometry. First, a gradual shift of molecular compositions was observed from reduced components to aromatic oxidized compounds isolated at pH 7 and 2, respectively. Changes in molecular compositions were accompanied by a red shift of fluorescence spectra. Further application of deuteromethylation enabled us to distinguish DOM constituents with different amounts of carboxylic groups. Moreover, identification of structural isomers in a single DOM sample was achieved. Statistical analysis revealed that red shift of fluorescence is facilitated by the increase of a contribution of aromatic poly(carboxylic acid)s with high conjugation lengths. Additionally, analysis of the labeled fractionated permafrost thaw DOM directly showed carboxyl-rich alicyclic molecules, while the same components from lower-latitude DOM were assigned to lignin-like species.

Separation of Benzoic and Unconjugated Acidic Components of Leonardite Humic Material Using Sequential Solid-Phase Extraction at Different pH Values as Revealed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and Correlation Nuclear Magnetic Resonance Spectroscopy.

Here, we report on sequential solid-phase extraction of leonardite hymatomelanic acid (CHM) on a non-ionic sorbent at four steadily lowered pH values: 7, 5, 3, and 2, yielding fractions with different acidic properties. Using nuclear magnetic resonance (NMR) spectroscopy and ultrahigh-resolution mass spectrometry, we revealed a gradual shift of dominating scaffolds in the fractions of CHM from reduced saturated to oxidized aromatic compounds. An increase on the average aromaticity of the CHM fractions was accompanied by a red shift in fluorescence spectra. These results were supported by heteronuclear single quantum coherence and heteronuclear multiple bond correlation NMR experiments. We have demonstrated that the CHM fraction isolated at pH 5 was dominated by aliphatic carboxyl carriers, while the pH 3 fraction was dominated by aromatic carboxyl acids. The developed fractionation technique will enable deeper insight on structure-property relationships and the design of the humic-based materials with tailored reactive properties.

The impact of wine components on fractionation of Cu and Fe in model wine systems: Macromolecules, phenolic and sulfur compounds

A variety of techniques have been developed with the ability to measure different forms of metals in wine with the ultimate aim of providing a more accurate indicator of metal induced spoilage of wine. This study was conducted in order to identify which wine components influence the measurement of Cu and Fe in their fractionated and/or electrochemically active forms. The measurement techniques involved detection of labile Cu by stripping potentiometry and fractionation of Cu and Fe by sequential solid phase extraction, with detection by inductively coupled plasma-optical emission spectroscopy. The wine components assessed included those extracted from wine (red wine tannin, white wine protein, white wine polysaccharide, red wine polyphenol, white wine polyphenol), and commercially available monomeric compounds, including phenolic compounds and sulfur-containing compounds. For Cu, only hydrogen sulfide, which is known to induce the formation of Cu(I) sulfide, showed any appreciable influence on the fractionation and electrochemical detection of Cu. This form of Cu was also identified as the major component of red and white wines. For Fe, the fractionation was different for red versus white wine, and influenced significantly by extracted red wine polyphenol, (−)-epicatechin, gallic acid and tartaric acid. The wine components showed more influence on Fe at pH4.00 compared to pH3.25. These results enable a targeted use of these techniques in the assessment of metal-induced spoilage of wine.

Chiral liquid chromatography-mass spectrometry (LC-MS/MS) method development for the detection of salbutamol in urine samples.

A sequential solid-phase extraction (SPE) method was developed and validated using liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) for the detection and quantification of salbutamol enantiomers in porcine urine. Porcine urine samples were hydrolysed with β-glucuronidase/arylsulfatase from Helix pomatia and then subjected to a double solid-phase extraction (SPE) first using the Abs-Elut Nexus SPE and then followed by the Bond Elut Phenylboronic Acid (PBA) SPE. The salbutamol enantiomers were separated using the Astec CHIROBIOTIC™ T HPLC column (3.0mm×100mm; 5μm) maintained at 15°C with a 15min isocratic run at a flow rate of 0.4mL/min. The mobile phase constituted of 5mM ammonium formate in methanol. Salbutamol and salbutamol-tert-butyl-d9 (internal standard, IS) was monitored and quantified with the multiple reaction monitoring (MRM) mode. The method showed good linearity for the range of 0.1-10ng/mL with limit of quantification at 0.3ng/mL. Analysis of the QC samples showed intra- and inter-assay precisions to be less than 5.04%, and recovery ranging from 83.82 to 102.33%.

Toxicity and composition profiles of solid phase extracts of oil sands process-affected water

After fractionation using sequential solid phase extraction, the presence of toxic components in oil sands process-affected water (OSPW) was detected by the Microtox® acute toxicity assay using effect-directed analysis. The composition of each fraction was determined by high-resolution electrospray ionization-Orbitrap mass spectrometry. Partial least-squares discriminant analysis (PLS-DA) was used to determine which chemical constituents in all seven fractions co-varied most strongly with toxicity. Although O2 compounds with double bond equivalence (DBE) between 3 and 9 positively correlated with toxicity, C15–C18 O2-NAs with DBE=4 (tricyclic structure), as well as C14–C17 O2-NAs with DBE=3 (bicyclic structure), were found to be most likely associated with OSPW toxicity, consistent with published toxicity studies of surrogate NAs. O4, many O3 (i.e. possibly hydroxylated O2 c-NAs) and a few O2 compounds were found to negatively correlate with toxicity. The results demonstrate the utility of the fractionation and the PLS-DA approach for evaluating composition-response relationships in a complex mixture and also contribute to a better understanding of the toxic compounds in OSPW. These findings will help to focus study on the most environmentally significant components in OSPW.

Preparative Isolation of Antioxidant Flavonoids from Small Black Soybeans by Centrifugal Partition Chromatography and Sequential Solid-Phase Extraction

Unlike other members of the leguminous family that are generally used as food, Rhynchosia volubilis, a small soybean with a black seed coat, is used as a folk medicine in Korea. Using an on-line high performance liquid chromatography-2,2ʹ-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation screening system, one peak in the ethyl acetate fraction exhibited outstanding antioxidant capacity. To purify and determine the antioxidant compounds associated with this peak, we developed a centrifugal partition chromatography (CPC) method. The ethyl acetate fraction (500 mg) was subjected to CPC using a two-phase solvent system of n-hexane–ethyl acetate–ethanol–water (0.1:8:2:7, v/v) with a dual-mode CPC (descending-ascending order) in a bid to separate glycitin (3.1 mg), daidzin (14.4 mg), 6ʹʹ-O-acetyl genistin (6.9 mg), 6ʹʹ-O-acetyl daidzin (5.3 mg), and a mixture of epicatechin and genistin. The mixture was further separated through solid-phase extraction to yield epicatechin (6.8 mg) and genistin (23.5 mg), respectively. Structural identification of the R. volubilis flavonoids was performed by NMR and ESI-MS.

Sunlight-driven photochemical halogenation of dissolved organic matter in seawater: a natural abiotic source of organobromine and organoiodine.

Reactions of dissolved organic matter (DOM) with photochemically generated reactive halogen species (RHS) may represent an important natural source of organohalogens within surface seawaters. However, investigation of such processes has been limited by difficulties in quantifying low dissolved organohalogen concentrations in the presence of background inorganic halides. In this work, sequential solid phase extraction (SPE) and silver-form cation exchange filtration were utilized to desalt and preconcentrate seawater DOM prior to nonspecific organohalogen analysis by ICP-MS. Using this approach, native organobromine and organoiodine contents were found to range from 3.2-6.4 × 10(-4) mol Br/mol C and 1.1-3.8 × 10(-4) mol I/mol C (or 19-160 nmol Br L(-1) and 6-36 nmol I L(-1)) within a wide variety of natural seawater samples, compared with 0.6-1.2 × 10(-4) mol Br/mol C and 0.6-1.1 × 10(-5) mol I/mol C in terrestrial natural organic matter (NOM) isolates. Together with a chemical probe method specific for RHS, the SPE+ICP-MS approach was also employed to demonstrate formation of nanomolar levels of organobromine and organoiodine during simulated and natural solar irradiation of DOM in artificial and natural seawaters. In a typical experiment, the organobromine content of 2.1 × 10(-4) mol C L(-1) (2.5 mg C L(-1)) of Suwannee River NOM in artificial seawater increased by 69% (from 5.9 × 10(-5) to 1.0 × 10(-4) mol Br/mol C) during exposure to 24 h of simulated sunlight. Increasing I(-) concentrations (up to 2.0 × 10(-7) mol L(-1)) promoted increases of up to 460% in organoiodine content (from 8.5 × 10(-6) to 4.8 × 10(-5) mol I/mol C) at the expense of organobromine formation under the same conditions. The results reported herein suggest that sunlight-driven reactions of RHS with DOM may play a significant role in marine bromine and iodine cycling.

Determination of polybrominated diphenyl ethers and polychlorinated biphenyls in fishery and aquaculture products using sequential solid phase extraction and large volume injection gas chromatography/tandem mass spectrometry

A new method was developed to determine polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in fishery and aquaculture products. Samples were extracted by an accelerated solvent extraction system and cleaned up by sequential solid phase extraction (SPE) including dispersive SPE (D-SPE) and tandem SPE. PBDEs and PCBs were analyzed by a large-volume injection gas chromatography triple quadrupole mass spectrometry (LVI-GC-QqQ-MS/MS). Good linearity (R(2)≥0.9958) was achieved. Method detection limits (MDLs) were 0.16-3.3pgg(-1) (wet weight, ww) for PBDEs and 0.13-0.97pgg(-1)ww for PCBs. Mean recoveries were 60-140% with relative standard deviations (RSDs) of less than 20% in weever fish, scallop and shrimp samples spiked at a lower level of 13-31pgg(-1)ww and a higher level of 50-125pgg(-1)ww. Certified reference materials were analyzed with acceptable results. The method reduced solvent consumption, analytical time and labor, and is suitable for the routine analysis of PBDEs and PCBs in fishery and aquaculture products.

Investigation of Color Instability in a Liquid Laundry Detergent

AbstractDuring reformulation of a liquid laundry detergent, an undesirable color change was observed: the normally blue color of the formulation was found to turn green when exposed to elevated temperatures during accelerated stability testing. Spectroscopic analysis revealed formation of a yellow substance, whose transmission spectrum combined with that of the blue dye to yield the observed green color. Sequential solid phase extraction using cation and anion exchange indicated the yellow substance was a base. Liquid chromatography–mass spectrometry (LC–MS) analysis of the isolate demonstrated a series of related compounds whose elemental composition and fragmentation suggested polyethenyl imines (PEIs). These results support a mechanism involving metal‐catalyzed oxidative degradation of triethanolamine (TEA) with subsequent acetaldehyde‐mediated formation of conjugated PEIs as primary factors responsible for the observed color change.

The effect of pH and natural microbial phosphatase activity on the speciation of uranium in subsurface soils

The biomineralization of U(VI) phosphate as a result of microbial phosphatase activity is a promising new bioremediation approach to immobilize uranium in both aerobic and anaerobic conditions. In contrast to reduced uranium minerals such as uraninite, uranium phosphate precipitates are not susceptible to changes in oxidation conditions and may represent a long-term sink for uranium in contaminated environments. So far, the biomineralization of U(VI) phosphate has been demonstrated with pure cultures only. In this study, two uranium contaminated soils from the Department of Energy Oak Ridge Field Research Center (ORFRC) were amended with glycerol phosphate as model organophosphate source in small flow-through columns under aerobic conditions to determine whether natural phosphatase activity of indigenous soil bacteria was able to promote the precipitation of uranium(VI) at pH 5.5 and 7.0. High concentrations of phosphate (1–3 mM) were detected in the effluent of these columns at both pH compared to control columns amended with U(VI) only, suggesting that phosphatase-liberating microorganisms were readily stimulated by the organophosphate substrate. Net phosphate production rates were higher in the low pH soil (0.73 ± 0.17 mM d −1) compared to the circumneutral pH soil (0.43 ± 0.31 mM d −1), suggesting that non-specific acid phosphatase activity was expressed constitutively in these soils. A sequential solid-phase extraction scheme and X-ray absorption spectroscopy measurements were combined to demonstrate that U(VI) was primarily precipitated as uranyl phosphate minerals at low pH, whereas it was mainly adsorbed to iron oxides and partially precipitated as uranyl phosphate at circumneutral pH. These findings suggest that, in the presence of organophosphates, microbial phosphatase activity can contribute to uranium immobilization in both low and circumneutral pH soils through the formation of stable uranyl phosphate minerals.

Transformation and Sorption of the Veterinary Antibiotic Sulfadiazine in Two Soils: A Short-Term Batch Study

The worldwide use of veterinary antibiotics poses a continuous threat to the environment. There is, however, a lack of mechanistic studies on sorption and transformation processes for environmental assessment in soils. Two-week batch sorption experiments were performed with the antibiotic sulfadiazine (SDZ) in the plow layer and the subsoil of a loamy sand and a silty loam. The sorption and transformation parameters of SDZ and its main transformation products N1-2-(4-hydroxypyrimidinyl) benzenesulfanilamide (4-OH-SDZ) and 4-(2-iminopyrimidin-1(2H)-yl)aniline (An-SDZ) were estimated using a global optimization algorithm. A two-stage, one-rate sorption model combined with a first-order transformation model adequately described the batch data. Sorption of SDZ was nonlinear, time-dependent, and affected by pH, with a higher sorption capacity for the loamy sand. Transformation of SDZ into 4-OH-SDZ occurred only in the liquid phase, with half-life values of 1 month in the plow layers and 6 months in the subsoils. Under the exclusion of light, An-SDZ was formed in substantial amounts in the silty loam only, with liquid phase half-life values of 2 to 3 weeks. Despite the rather large parameter uncertainties, which may be reduced using additional information obtained from sequential solid phase extraction, the proposed method provides a framework to assess the fate of antibiotics in soils.

Evaluation of the Removal of Pollutants from Petrochemical Wastewater Using A Membrane Bioreactor Treatment Plant

A submerged membrane bioreactor (MBR) was used to treat two types of petrochemical wastewater: olefin process wastewater and total petrochemical wastewater. Various operational MBR conditions, such as influent pH and hydraulic retention time (HRT), were tested while these wastewaters were treated. The MBR treatment of olefin process wastewater reduced chemical oxygen demand (COD) and total organic carbon (TOC) by around 90% in both cases, and more than 90% of the suspended solids (SS) were removed. When MBR was used, the reduction in COD and TOC was also high for the total petrochemical wastewater, and was compared with the reduction obtained when the conventional activated sludge treatment plant was used (CASP). However, MBR effluent wastewaters showed high conductivity so for some reuse purposes subsequent reverse osmosis (RO) treatment would be needed. We characterized the MBR influent and MBR effluent wastewaters using a sequential solid phase extraction (SSPE) followed by gas chromatography-mass spectrometry (GC–MS) analyses. The main compounds that were tentatively identified were hydrocarbons, alkyl benzenes, phenols, acidic acids and esters, almost all of which could be partially or completely removed by MBR treatment.

Fast urinary screening for imipramine and desipramine using on-line solid-phase extraction and selective derivatization

A continuous-flow configuration based on sequential solid-phase extraction and derivatization is proposed for the screening of urine samples for imipramine and related metabolites. For the first time, a 50/50 (v/v) methanol/nitric acid mixture is used as both eluent and derivatizing reagent. Sample aliquots are injected into the flow manifold and driven by a water stream to an RP-C 18 column where the drugs are quantitatively retained. Following clean-up step with 40/60 (v/v) methanol/water, the eluent/derivatizing reagent is injected and passed through the sorbent column, eluted drugs reacting with nitric acid to form a blue dye that is monitored at 600 nm. The global signal thus obtained for the antidepressants can be used to estimate their total concentration in the samples without the need to individually quantify the analytes. This total index can be used for timely decision-making in case of overdosage. The proposed method is sensitive and selective; thus, typical interferents such as endogenous and diet compounds have no substantial effect on the analytical signal. This allows imipramine and its metabolites to be determined at therapeutic levels in urine samples.

European ring exercise on water toxicity using different bioluminescence inhibition tests based on Vibrio fischeri, in support to the implementation of the water framework directive

An inter-laboratory comparison exercise was conducted under the European Union funded project entitled: Screening Methods for Water Data Information in Support of the Implementation of the Water Framework Directive (SWIFT-WFD) and coordinated by the Consejo Superior de Investigaciones Científicas (CSIC), in order to evaluate the reproducibility of different toxicity tests based on the bioluminescence inhibition of Vibrio fischeri, for the rapid water toxicity assessment. For the first time, this type of exercise has been organized in Europe, and using different tests based on the same principle. In this exercise, 10 laboratories from 8 countries (Austria, Cyprus, Germany, Greece, Italy, Portugal, Romania, and Spain) took place, and a total number of 360 samples were distributed. During the exercise, six series of six samples were analyzed along 5 months. Every batch of samples was composed by three real samples and three standard solutions. The real samples were: a raw influent and the effluent of a wastewater treatment plant (WWTP), and a sample from a first settlement of the WWTP spiked with a mixture of toxicant standards. A final number of 330 (91.7%) samples was analyzed, 3300 values in duplicate were collected, and the results for each sample were expressed as the 50% effective concentration (EC 50) values calculated through five points of dilution inhibition curves, after 5 and 15 min of incubation times. A statistical study was initiated using 660 results. The mean values, standard deviations ( σ), variances ( σ 2), and upper and lower warning limits (UWL and LWL) were obtained, using the EC 50 values calculated with the result from the participating laboratories. The main objectives of this toxicity ring study were to evaluate the repeatability ( r) and reproducibility ( R) when different laboratories conduct the test, the influence of complex matrix samples, the variability between different tests based on the same principle, and to determine the rate at which participating laboratories successfully completed tests initiated. In this exercise, the 3.93% toxicity values were outliers according with the Z-score values and the Dixon test. The samples with the greater number of outliers were those with the smallest variability coefficient, corresponding to the greater and the smaller toxicity level. No relation was found through the cluster analysis, between the final results and the different commercial devices involved. Testing by multiple commercial devices did not appear to reduce the precision of the results, and the variability coefficient for the exercise was nearby to the average value for past editions carried out at national level, where the different participants used the same commercial device. Stability of samples was also followed during the exercise. While statistical significance differences were not found for the greater part of samples, for the sample from the WWTP influent, a significant decrease of the toxicity value was found along this study. Nevertheless, this was a type of sample with a high toxicity level during all the exercise. On the other hand, in order to obtain the chemical characterization of real samples, those were analyzed by chromatographic techniques, using different sequential solid phase extraction (SSPE) procedures, followed by liquid chromatography coupled with mass spectrometry (LC–MS), and gas chromatography–mass spectrometry (GC–MS). Good agreement was found between the chemical analysis results and the toxicity level of the samples.

Systematic Analysis of the Epidermal Growth Factor Receptor by Mass Spectrometry Reveals Stimulation-dependent Multisite Phosphorylation

Multisite phosphorylation of proteins is a general mechanism for modulation of protein function and molecular interactions. Definition of phosphorylation sites and elucidation of the functional interplay between multiple phosphorylated residues in proteins are, however, a major analytical challenge in current molecular cell biology and proteomic research. In the present study, we used mass spectrometry to determine the major phosphorylated residues of the human epidermal growth factor (EGF) receptor at various well defined cellular conditions. Activation of EGF receptor was achieved by several types of stimulation, i.e. by sodium pervanadate, EGF, and integrin-dependent adhesion. The contribution of cell-matrix adhesion was also determined by activating the EGF receptor by EGF in cells kept in suspension. We developed an analytical strategy that combined miniaturized sample preparation techniques and MALDI tandem mass spectrometry and determined a total of nine phosphorylation sites in the EGF receptor. We discovered one novel phosphorylation site (Ser967) and revealed constitutive phosphorylation of Thr669, Ser967, Ser1002, and Tyr1045 and stimulation-dependent differential phosphorylation of Tyr1068, Tyr1086, Ser1142, Tyr1148, and Tyr1173. The EGF receptor was purified from HeLa cells or ECV304 cells by immunoprecipitation and SDS-PAGE and then digested with trypsin. Phosphopeptides in the range of 0.8-3.7 kDa were recovered by combinations of IMAC, perfusion chromatography, and graphite powder chromatography and subsequently detected and sequenced by MALDI quadrupole time-of-flight tandem mass spectrometry. Two phosphorylation sites were detected in the peptide 1137GSHQISLDNPDYQQDFFPK1155; however, only Tyr1148 was phosphorylated upon EGF treatment; in contrast Ser1142 was only phosphorylated by integrin-dependent adhesion in the absence of EGF treatment, suggesting differential phosphorylation of this region by distinct stimuli. This MALDI MS/MS-based analytical approach demonstrates the feasibility of systematic analysis of signaling molecules by mass spectrometry and provides new insights into the dynamics of receptor signaling processes.

Validated toxicological determination of 30 drugs of abuse as optimized derivatives in oral fluid by long column fast gas chromatography/electron impact mass spectrometry

An analytical procedure was developed for the simultaneous sensitive identification, screening and quantitation of 30 drugs of abuse using 250 microl of human oral fluid. The method employs sequential mixed-mode solid-phase extraction (SPE), optimized derivative formation and long-column fast gas chromatography/electron impact mass spectrometry (GC/EI-MS). After sequential SPE elution, the most sensitive and stable derivatives were formed by taking careful account of the characteristics of the active functional groups and possible steric hindrances affecting derivatization chemistry. Amphetamine-type stimulant drugs were acylated with heptafluorobutyric anhydride, benzodiazepines and Delta(9)-tetrahydrocannabinol were silylated with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide and benzoylecgonine, codeine, ethylmorphine, 6-monoacetylmorphine, morphine, pholcodine, buprenorphine and norbuprenorphine with N-methyl-N-(trimethylsilyl)trifluoroacetamide. In addition, the following analytes were included: methadone, cocaine, alprazolam, midazolam, fentanyl and zolpidem. In GC separation, fast temperature ramping and high carrier gas flow-rate combined with long 30 m columns of i.d. 0.32 mm offered a reduction in analysis time and sharp peak shapes while still maintaining sufficient resolution and high sample capacity. Validated parameters including selectivity, linearity, accuracy, intra- and inter-day precision, extraction efficiency and limit of quantitation were all within required limits. In contrast to previously published methods, this single procedure is suitable for the simultaneous toxicological determination of the most common illicit drugs and benzodiazepines, and also zolpidem, in a small amount of oral fluid.

Multi-component analysis of polar water pollutants using sequential solid-phase extraction followed by LC-ESI-MS.

A multi-component screening analysis method for polar to medium-polar water pollutants was developed. Sample clean-up and group separation are performed by sequential solid-phase extraction (SSPE) using automated SPE with C18 and polymeric sorbent materials. Analyses are performed by liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) using a single-quadrupole instrument. More than 90 priority compounds of environmental interest--comprising the most important chemical and substance classes: phenols, carboxylic acids, aromatic sulfonates, aromatic amines, pharmaceuticals, surfactants, dyes, and pesticides--have been chosen for the experiments. The compounds are divided by the SSPE procedure into 3 different polarity classes. The extraction recoveries were determined in the 3 fractions for every single substance, and were for most of the analytes in the range of 50-100%. A mixture of hexane-dichloromethane was used for the elution of nonpolar compounds like alkylphenols from C18. Methanol and acetone are well suited for the elution of more polar substances. The limits of detection (LODs) were determined for all compounds. Effluents from municipal and industrial wastewater treatment plants (WWTPs) treating waste water from textile industries; and the corresponding receiving waters (rivers and lakes) have been analysed with the developed method. Urban and industrial pollution was observed in rivers and streams in the area north of Milan, Italy. In the water samples different phenols (nitrophenols, bisphenol A, nonylphenol), alkylphenol ethoxylate surfactants, their metabolites with endocrine disrupting potential, aromatic sulfonates, linear alkylbenzenesulfonate surfactants, dyes, pesticides, pharmaceuticals, and a dichlorobenzidine compound were identified.

Monitoring of aromatic monosulfonic acids in coastal waters by ion-pair liquid chromatography followed by electrospray-mass spectrometric detection

Spain is one of the European countries that still discharges untreated wastewaters and sewage sludge into the sea. Aromatic monosulfonated compounds were detected in 36 seawater samples collected bimonthly on the Catalonian coast (Spain) over a period of 18 months. These compounds are of environmental concern because of their limited biodegradability and high mobility within the aquatic system. A method based on a sequential solid-phase extraction procedure (SSPE) followed by ion-pair liquid chromatography coupled to electrospray ionization-mass spectrometry (IPC-ESI-MS) in negative ionization mode was used to monitor aromatic monosulfonated compounds in the Catalonian coastal waters. Triethylamine (TEA) and acetic acid (HOAc) were used as volatile mobile-phase additives. A comparison of two polymeric solid-phase extraction (SPE) materials for the extraction of 15 aromatic monosulfonated compounds of environmental concern was performed. The investigated adsorbents were the polystyrene-divinylbenzene materials Lichrolut EN, from Merck, and Isolute ENV+, from International Sorbent Technology (IST). The influence of the matrix on the analysis of seawater samples was also studied. Applications of the developed analytical procedure to seawater samples gave limits of detection (n = 3) ranging from 0.6 to 45 pg on column for the target analytes. Barcelona and Tarragona locations were chosen along the Catalonian coast as sampling sites because of their large sewage discharges and intensive industrial activities. Samples were acquired from submarine outfalls of two rivers, Besos and Llobregat, located in the north and south of Barcelona city, respectively. Samples from petrochemical industry submarine outfalls located near the commercial port of Tarragona were also studied. Concentrations of benzenesulfonates (BS) and naphthalenesulfonates (NS) were of the order of ng/ml. Most of the collected samples were found to contain both isomers of mononaphthalenesulfonate. The study showed that these compounds can contaminate marine coastal waters.