Potentiality of proton nuclear magnetic resonance and multivariate calibration methods for the determination of dermatan sulfate contamination in heparin samples

A 1H NMR method for the quantification of dermatan sulfate impurities in heparin industrial samples is proposed. The method is based on the analysis of 1H NMR spectral data by multivariate calibration. The 1H NMR spectra of heparin and dermatan sulfate standards showed characteristic profiles. Thus, differences in the methyl peaks of acetamido groups of heparin and dermatan sulfate were greatly advantageous for the analysis. Other hydrogens of the sugar ring were also relevant in this study. Thus, the determination of dermatan sulfate by multivariate calibration depended on all these differences. Partial least squares regression (PLS) was chosen as the calibration method. In addition, a data standardization procedure was developed in order that 1H NMR spectra registered with different instruments operating under different measurement conditions were comparable. The quantification of dermatan sulfate in the samples was satisfactory, with an overall prediction error of 6%.

Analysis of glycosaminoglycan monosaccharides by capillary electrophoresis using indirect laser-induced fluorescence detection

Two methods for monosaccharide analysis by capillary electrophoresis (CE) using counterelectroosmotic and coelectroosmotic modes with indirect laser-induced fluorescence detection were optimised and compared. A mixture of seven glycosaminoglycan-derived hexoses was separated in alkaline fluorescein-based electrolytes and detected in both counterelectroosmotic and coelectroosmotic conditions. The fluorescein concentration and pH of the background electrolyte, and the influence of the reversal of electroosmotic flow by addition of hexadimethrine bromide on the separation were studied. Coelectroosmotic CE conditions provided better resolution and limits of detection. A 10(-6) M fluorescein solution at pH 12.25 containing 0.0005% (w/v) hexadimethrine bromide was used as background electrolyte. Quality parameters such as run-to-run, day-to-day precision and limits of detection were calculated, and better figures of merit were obtained for the coelectrooosmotic conditions than for the counterelectroosmotic mode. The coelectroosmotic method was applied to the quantitation of the hexosamine contents in glycosaminoglycans after acid hydrolysis. The method proved to be suitable for the determination of dermatan sulfate in heparin down to 2% (w/w).

Determination of heterocyclic aromatic amines in meat extracts by liquid chromatography-ion-trap atmospheric pressure chemical ionization mass spectrometry

When protein-rich foods are processed under normal cooking conditions, heterocyclic aromatic amines (HAAs) can be generated at a few parts per billion level. In this work, we have analyzed the HAAs present in a lyophilized meat extract by means of a simplified solid-phase extraction procedure. All the analytes were collected in a single extract with recoveries in the range of 45.6-75.2%, so the analysis time has been greatly reduced. Problems derived from the less exhaustive purification of the extract have been solved by using MS(ion trap) detection. The RSD for quantification ranged from 2.1% to 5.1% for run-to-run precision and from 5.2% to 11% for day-to-day precision. The limits of detection for standard solutions ranged from 20 to 150 pg injected. For the meat extract analyzed limits of detection from 0.9 to 11.2 ng g(-1) were obtained. Results of the quantification are in agreement with those obtained using different clean-up procedures.

On-line ion-pair solid-phase extraction-liquid chromatography-mass spectrometry for the analysis of quaternary ammonium herbicides

An ion-pair on-line solid-phase extraction procedure using C8 extraction disks, suitable for liquid chromatography-mass spectrometry analysis is developed to determine quaternary ammonium herbicides (quats) in water samples. The separation of these compounds was performed using ion-pair chromatography with heptafluorobutyric acid (15 mM, pH 3.3) and acetonitrile gradient elution. Detection was carried out using a quadrupole mass spectrometer. Water sample volumes up to 50 ml can be preconcentrated with recoveries higher than 70%. Good precision and accuracy (day-to-day and run-to-run) were obtained and the detection limits ranged from 6 to 85 ng l(-1). The proposed on-line ion-pair solid-phase method enables compliance with European Community directives for drinking waters (100 ng l(-1)).

New carrier electrolytes for the separation of chlorophenols by capillary electrophoresis

Optimum conditions for the separation of positional isomers of chlorophenols by capillary zone electrophoresis (CZE) were established. The behavior of five volatile electrolytes (L-cysteic acid, 3-amino-1-propanesulfonic acid, aminomethanesulfonic acid, diethylmalonic acid, and ammonium acetate) was compared. The best performance based on low electrophoretic current and high separation efficiency was obtained for diethylmalonic acid as working electrolyte. The influence of pH on the separation, using both uncoated fused-silica capillaries and modified capillaries (NaAMPS from EKT) with anionic coating, was discussed. Moreover, the effect of electrolyte concentration and applied voltage using fused-silica capillaries was studied. The optimum CZE conditions that allowed the separation of 16 chlorophenols were 20 kV, 30 mM diethylmaIonic acid, pH 7.25, and uncoated fused-silica capillary. Figures of merit such as run-to-run and day-to-day precision, linearity, and limits of detection were calculated.

Gas chromatography/ion trap tandem mass spectrometry for the analysis of halobenzenes in soils by solid-phase microextraction

Headspace solid-phase microextraction combined with gas chromatography/ion trap tandem mass spectrometry (HS-SPME/GC/ITMS/MS) was used for the analysis of 12 halobenzenes from soil samples. For MS/MS optimisation, the experiments were performed by precursor ion selection and software controlled operations. Collision-induced dissociation (CID) can be achieved by two different approaches, resonant and non-resonant excitation modes. Different results were obtained using the two approaches, and the resonant excitation mode was chosen as the best for all halobenzenes. Parameters such as the CID excitation amplitude, excitation RF storage level and CID bandwidth frequency were optimised to maximise the formation of halobenzene product ions. A 100-microm polydimethylsiloxane fibre was used for the isolation and preconcentration of the analytes. The HS-SPME/GC/ITMS/MS method was applied to the analysis of halobenzenes in an agricultural soil sample. The halobenzenes were quantified by standard addition, which led to good reproducibility (RSD between 4.7 and 9.2%) and detection limits in the low pg/g range. The method was validated by comparing the results with those obtained in a European inter-laboratory exercise.

Solid-phase microextraction coupled with gas chromatography-ion trap mass spectrometry for the analysis of haloacetic acids in water

Headspace solid-phase microextraction (SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of haloacetic acids (HAAs) in water. The method involves derivatization of the acids to their ethyl esters using sulphuric acid and ethanol after evaporation, followed by headspace SPME with a polydimethylsiloxane fibre and gas chromatography-ion trap mass spectrometry (GC-IT-MS). The derivatization procedure was optimized: maximum sensitivity was obtained with esterification for 10 min at 50 degrees C in 30 microl of sulphuric acid and 40 microl of ethanol. The headspace SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25 degrees C, an absorption time of 10 min, the addition of 0.1 g of anhydrous sodium sulfate and a desorption time of 2 min. Good precision (RSD lower than 10%) and detection limits in the ng l(-1) range (from 10 to 200 ng l(-1)) were obtained for all the compounds. The optimized procedure was applied to the analysis of HAAs in tap water and the results obtained by standard addition agreed with those of EPA method 552.2, whereas discrepancies due to matrix interferences were observed using external calibration. Consequently, headspace SPME-GC-IT-MS with standard addition is recommended for the analysis of these compounds in drinking water.

Solid-phase microextraction for the determination of iodinated trihalomethanes in drinking water

A headspace solid-phase microextraction (HS-SPME) method has been developed for the determination of iodinated trihalomethanes (ITHMs) in treated water samples. Mixed THMs (bromochloroido-, bromodiiodo-, chlorodiiodo-, dibromoiodo- and dichloroiodo-) were previously synthesized since commercial standards are not available. HS-SPME has shorter equilibration times than direct SPME, a cleaner background and a longer fiber life. Experimental parameters such as the selection of SPME coatings, sample volume, extraction time and addition of salts were studied. The Carbowax-divinylbenzene fiber appears to be the most suitable for the determination of ITHMs. Analytical parameters such as linearity, limit of detection and precision were also evaluated. HS-SPME was compared to liquid-liquid microextraction for the analyses of spiked treated water samples, obtaining a good agreement. It is concluded that HS-SPME has a great potential for drinking water analysis.

Evaluation of different clean-up procedures for the analysis of heterocyclic aromatic amines in a lyophilized meat extract

Along with other mutagenic and carcinogenic contaminants in foods such as aflatoxins, and polycyclic aromatic hydrocarbons, heterocyclic aromatic amines (HAAs) have received considerable attention in recent years. A major drawback in the analysis of HAAs in foods is their very low level of concentration (0.1 50 ng g-1) as well as matrix interferences. Solid-phase extraction (SPE), forming an integral part of chromatographic analysis, is one of the procedures currently used for the extraction and purification of HAAs in food samples. In this paper a comparative study of several SPE procedures for HAAs determination was performed. Recoveries of the heterocyclic amines in the analysis of both a simple matrix such as a standard methanolic solution and a contaminated meat extract were established. HAAs were determined by HPLC analysis with photodiode-array detection (DAD) of the purified extracts, and the adequacy of different clean-up procedures for the analysis of a contaminated meat extract was discussed.

Ion-pair liquid chromatography--atmospheric pressure ionization mass spectrometry for the determination of quaternary ammonium herbicides

High-performance liquid chromatography coupled with atmospheric pressure ionization mass spectrometry (electrospray and atmospheric pressure chemical ionization) has been used to characterize some quaternary ammonium herbicides (quats). The separation of these compounds was carried out using ion-pair chromatography with heptafluorobutyric acid (15 mM, pH 3.3) and acetonitrile gradient elution for successful coupling to mass spectrometry. Detection limits down to 0.1-4 micrograms l-1 were obtained for spiked tap water following a preconcentration step. Good reproducibilities (day-to-day and run-to-run) were also obtained.

Use of reversed polarity and a pressure gradient in the analysis of disaccharide composition of heparin by capillary electrophoresis

A capillary electrophoresis method with reversed polarity, combining both the application of a voltage and a pressure gradient between the buffer vials, was developed for the analysis of eight heparin-derived delta-disaccharides obtained by enzymatic depolymerization. A 60 mM formic acid buffer at pH 3.40 was selected as running electrolyte, with an applied voltage of -15 kV and an over-imposed pressure gradient (3.45.10(-3) MPa) for 6 min from inlet to outlet starting at 20 min. Figures of merit such as run-to-run and day-to-day precision, and limits of detection were established. The electrophoretic method was applied to the analysis of depolymerization products of different kinds of heparins. The composition of the depolymerization buffer was selected in order to reduce baseline distortions in the electrophoretic separation, thus a buffer solution containing 20 mM Tris, 50 mM sodium chloride, and 3 mM calcium chloride at pH 7.10 was used. Percentages of molar disaccharide compositions for unfractionated heparins from porcine, bovine and ovine intestinal mucosa, and bovine lung were determined. In addition, low-molecular-mass heparins from bovine and porcine intestinal mucosa were analysed as well.

Experimental design approach for the optimization of supercritical fluid extraction of chlorophenols from polluted soils

Supercritical fluid extraction and liquid chromatography-electrochemical detection (LC-ECD) were used to the determination of chlorophenols in contaminated soil samples. Full factorial design experiments were used in order to optimize the extraction parameters: pressure, extraction cell temperature and percentage of modifier. Pressure and percentage of modifier (methanol) had statistically significant effects on the recovery of the chlorophenols. Good repeatability (4.9-11.8%) and reproducibility (4.9-12.5%) were achieved and low detection limits (3-150 ng g-1) were obtained. The method was validated by comparing the results with those obtained in a European intercomparison exercise.

Liquid chromatography-atmospheric pressure ionization mass spectrometry for the determination of chloro- and nitrophenolic compounds in tap water and sea water

Liquid chromatography coupled to atmospheric-pressure ionization mass spectrometry (LC-API-MS) with negative ion detection was studied for the determination of a variety of phenolic compounds in environmental waters. An isocratic mobile phase of 0.05% acetic acid-acetonitrile (50:50, v/v) was used. The influence of post-column addition of different bases on the sensitivity of the detection in electrospray (ES) was studied. The [M-H]-ion was the base peak for all the compounds using both ES and atmospheric-pressure chemical-ionization (APCI) ion sources. Moreover, abundant structural information was obtained by increasing the extraction voltage. Detection limits for standard solutions ranging from 2 to 13 ng injected for LC-ES-MS and from 0.02 to 20 ng for LC-APCI-MS were obtained. Good reproducibilities (day-to-day and run-to-run) were observed. The optimum LC-ES-MS and LC-APCI-MS conditions thus determined were used for a quantitative analysis of some phenolic compounds in spiked tap water and sea water samples.

Liquid chromatography-atmospheric-pressure chemical ionization mass spectrometry as a routine method for the analysis of mutagenic amines in beef extracts

A liquid chromatography-mass spectrometry (LC-MS) method using atmospheric-pressure chemical ionisation as interface was developed for the simultaneous determination of 14 heterocyclic aromatic amines and related compounds in beef extracts. The separation was performed on a conventional C18 column using a binary mobile phase composed of acetonitrile and 50 mM ammonium acetate at pH 5.7, and elution was carried out in gradient mode. Several parameters influencing the mass spectra were optimized, and the effect of the variation of cone voltage on the mass spectra was studied. The [M+H]+ ions and some fragments produced in the source were observed in the mass spectra when several extraction voltages were applied. Quality parameters (run-to-run and day-to-day reproducibility, intervals of linearity, and limits of detection) were studied in the optimum working conditions. The method was used to analyze the heterocyclic amines present in a commercial beef extract. Therefore, a solid-phase extraction clean-up procedure was performed prior the LC-MS analysis due to the complexity of the sample and the compounds Glu-P-1, Harman, Norharman and A alpha C were identified in the samples at ppb levels and successfully confirmed using in-source fragmentation.

Liquid chromatography-electrospray mass spectrometry with in-source fragmentation for the identification and quantification of fourteen mutagenic amines in beef extracts

Conditions for the liquid chromatography-electrospray mass spectrometric (LC-ES-MS) determination of the fourteen most abundant heterocyclic amines and related compounds that can be produced in thermally processed foods were established. The simultaneous separation of all HAs on an octadecylsilane microbore column using a gradient elution with 5 mM ammonium acetate, pH 4.0, and acetonitrile was optimized. The mass spectra obtained at different extraction voltages were studied. The highest extraction voltages provided structural information for the characterization of these amines. Good detection limits comparable with those of LC and electrochemical detection were obtained. The method was applied to the analysis of these mutagens in beef extracts after a solid-phase extraction clean-up and in-source fragmentation had been applied for confirmation purposes. The levels of several heterocyclic amines measured were estimated to be in the range of 7.8-135.2 ng g-1.

Solid-phase extraction for the selective isolation of polycyclic aromatic hydrocarbons, azaarenes and heterocyclic aromatic amines in charcoal-grilled meat

A method for the simultaneous analysis of 12 mutagenic and/or carcinogenic compounds is described; these substances belong to three different chemical groups: polycyclic aromatic hydrocarbons (PAHs), azaarenes, i.e., nitrogen-containing polycyclic aromatic hydrocarbons (PANHs), and heterocyclic aromatic amines (HAAs). The selective enrichment procedure includes coupling of solid-phase extraction (SPE) steps using diatomaceous earth, propylsulfonic acid, silica gel and octadecylsilane columns. The eluted fractions were analysed by high-performance liquid chromatography with UV and electrochemical detection. Levels measured were estimated to be 4-19 ng g-1. Peak confirmation was carried out by GC-MS for both PAHs and PANHs, and by LC with a photodiode array detector for HAAs. The method was applied to the analysis of charcoal-grilled meat and was judged to be generally applicable for detection of these mutagens at the ppb level in processed foods.

Determination of heterocyclic amines by pneumatically assisted electrospray liquid chromatography-mass spectrometry

Electrospray ionization mass spectrometry was applied to the study of the amines IQ, Trp-P-1, Trp-P-2, PhIP and A alpha C and the co-mutagens harman and norharman. The results obtained on a triple quadrupole mass spectrometer equipped with a pneumatically assisted electrospray source are reported. The chromatographic conditions were optimized with a reversed-phase column (1 mm I.D.) using acetonitrile-5 mM ammonium acetate (pH 6.7) (50:50) as the mobile phase at a flow-rate of 50 microliters min-1. Different parameters influencing the mass spectra were investigated. For these compounds [M + H]+ in the positive-ion mode and also some fragments produced through collisionally activated decomposition in the interface were observed. Detection limits of 5.4-44 pg were obtained for standard solutions of these amines. Analysis of a meat extract was performed by HPLC-MS using single-ion monitoring after a solid-phase extraction clean-up.

Isolation by solid-phase extraction and liquid chromatographic determination of mutagenic amines in beef extracts

A solid-phase extraction method was successfully optimized for the isolation and preconcentration of five mutagenic amines, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, 3-amino-1-methyl-5H-pyrido[4,3-b]indole, 2-amino-9H-pyrido[2,3-b]indole, 2-amino-3-methyl-9H-pyrido[2,3-b]indole and 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine, and two co-mutagens, 1-methyl-9H-pyrido[4,3-b]indole and 9H-pyrido[4,3-b]indole. Coupling of diatomaceous earth, propylsulphonyl silica gel, and octadecylsilane cartridges was used to separate selectively the imidazopyridine and indolpyridine derivatives from those of quinoxaline and quinoline. A method based on this sample preparation was applied to the determination of twelve heterocyclic amines and related substances in a commercial beef extract using HPLC with electrochemical and fluorescence detection. Good recovery values were obtained, ranging between 55 and 99%. The co-mutagens 1-methyl-9H-pyrido[4,3-b]indole (harman) and 9H-pyrido[4,3-b]indole (norharman) were found in the beef extract at levels of 110 and 53 ng g-1, respectively, and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) and 2-amino-9H-pyrido[2,3-b]indole (A alpha C) were tentatively identified.

Investigation of the metabolism of ebrotidine in human urine by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Ebrotidine is a new H2-receptor antagonist that, in addition to its antisecretory activity, exhibits a remarkable ability for gastric mucosal protection and acts as a potent inhibitor of protease and lipase enzymes elaborated by Helicobacter pylori. To study the metabolism of ebrotidine in human urine, HPLC/MS with an atmospheric pressure chemical ionization (APCI) interface and simultaneous UV detection was conducted. HPLC/MS separation of the reference compounds was performed, and positive and negative APCI mass spectra were obtained. Compounds of low molecular weight (M(r) < 300) showed predominantly the quasi-molecular ion. Intermediate size compounds (300 < M(r) < 400) gave a different type of spectra, depending on the ion mode: the positive mass spectra showed only the protonated molecular ion, whereas in the negative mass spectra many fragments appeared in addition to the deprotonated molecular ion. For molecules with a higher molecular weight (M(r) > 400), high fragmentation was observed. LC/MS with an APCI interface in positive and negative modes allowed the identification of ebrotidine, 4-bromobenzenesulfonamide, and four S-oxidized metabolites in human urine.

Environmental analysis of polychlorinated terphenyls: distribution in shellfish from the Ebro Delta (Mediterranean)

Polychlorinated terphenyls (PCTs) have characteristics almost identical with those of polychlorinated biphenyls (PCBs) and have been used for analogous applications, but only sporadic reports of the occurrence of PCTs in the environment have been published. High-resolution gas chromatography with electron-capture detection (HRGC-ECD) and mass spectrometric detection in the selected ion monitoring mode was used to analyse samples for PCTs. The homologue distribution of Aroclor 5432, 5460, Leromoll 141 and the PCTs in samples of shellfish from the Ebro Delta (Catalonia, Spain) was established, taking into account the contribution of the [M-Cl2]+ fragments. Quantification was achieved by HRGC-ECD. Concentrations were between 790 and 3 ng/g (dry mass).

Nitriles and isonitriles as interferents in cyanide determination in polluted waters

The interference of nitriles and isonitriles in cyanide determination was studied using the pyridine-barbituric acid direct spectrophotometric method or the same method after distillation of the sample, a microdiffusion-potentiometric (ion-selective electrode) also being used. Phenylacetonitrile, benzonitrile, acrylonitrile, iminodiacetonitrile and acetonitrile were tested as nitriles. Benzyl isocyanide butyl isocyanide and 1-[(isocyanomethyl)sulphonyl]-4-methylbenzene were assayed as isonitriles. It can be concluded that both nitriles and isonitriles should be considered as interferents in all the methods of cyanide determination studied. The level of interference generally increases with the ratio of interfering compound to cyanide and is greatest for low cyanide concentrations.

Liquid chromatographic determination of available lysine in soybean and fish meal

A method for the determination of available lysine on the basis of the reactivity of the epsilon-amino group with fluorodinitrobenzene (FDNB) has been optimized. Hydrolysis is performed in closed vessels in an autoclave. Conditions for different meals were established by using a modified sequential simplex method. Hydrolysis for 4 h was sufficient for the meals studied--soybean and fish. The use of liquid chromatography to determine available lysine was studied, and optimum conditions were established for separation and quantitation of epsilon-DNB-lysine. The proposed method is faster, more accurate, and more precise than commonly used methods.