A rapid HPLC method for the determination of carboxylic acids in human urine using a monolithic column

A rapid HPLC method for the determination of carboxylic acids in urine samples using a Chromolith Performance RP/18e 100/4.6 with Chromolith Guard Cartridge RP/18e 10/4.6 (Merck KgaA, Darmstadt, Germany) was developed. The method facilitates the simultaneous determination of aromatic hydrocarbon metabolites mandelic acid (MA) and phenylglyoxylic acid (PGA) from styrene and ethylbenzene, hippuric acid (HA) from toluene and 2-, 3-, 4-methylhippuric acids (MHA) from xylene. 3-Hydroxybenzoic acid (3-HBA) was used as internal standard. A chromatographic run is completed within less than 5 min for styrene, ethylbenzene and toluene metabolites, and within 10 min for xylene metabolites. The detection limits are 9 mg L^–1 urine for MA, 1.25 mg L^–1 urine for PGA, 4.9 mg L^–1 urine for HA, 22 mg L^–1 urine for 2-MHA, and 18.5 mg L^–1 urine for 3-MHA.No significant differences of the MA, PGA and HA concentrations in human urine samples obtained by HPLC chromatography on LiChrosorb RP 18 and on Chromolith RP/18e columns were found. The results were evaluated by using ANOVA.Abbreviations MA mandelic acid - PGA phenylglyoxylic acid - HA hippuric acid - MHA methylhippuric acid - 3-HBA 3-hydroxybenzoic acid - ANOVA analyses of variance - GC gas chromatography - HPLC high-performance liquid chromatography     

Multiresidue method using SPME for the determination of various pesticides with different volatility in confined atmospheres

An analytical method is described for assessing the vapour concentration of 11 pesticides (bioallethrin, chlorpyriphos methyl, folpet, malathion, procymidone, quintozene, chlorothalonil, fonofos, penconazole and trimethacarb) in confined atmospheres (e.g. a greenhouse after pesticide application). This study is a successful extension of a method previously developed by the authors for dichlorvos to much less volatile pesticides. Sampling was performed by using polydimethylsiloxane–solid phase micro-extraction (PDMS–SPME) fibres immersed in a 250-mL sampling flask through which air samples were dynamically pumped from the analysed atmosphere. After a 40-min sampling duration, samples were analysed by GC/MS.Calibration was performed from a vapour-saturated air sample. The linearity of the observed signal versus pesticide concentration in the vapour phase was proved from spiked liquid samples whose headspace concentrations were measured by using the proposed method. This procedure gave calibration curves with regression coefficients (R²) greater than 0.98, and the repeatability of these measurements was found with RSDs of 1.9–7.6%. As a field application test, this analysis procedure was used for the determination of gaseous procymidone concentrations as a function of time in the atmosphere of an experimental 8-m² and 20-m³ greenhouse. The pesticide was sprayed according to real cultivation conditions, and measurements were made for 80 h after application (8 measurements). The observed concentrations found ranged from 200 to 500 µg m^–3, thus indicating the level of contamination of the air breathed by people in such working conditions.Abbreviations GC/MS gas chromatography/mass spectrometry - SIM selective ion monitoring - FC43 perfluorotributylamine - RSD relative standard deviation - LOD limit of detection - LOQ limit of quantification     

2-(5-Nitro-2-Pyridylazo)-5-(N-Propyl-N-Sulfopropylamino)Phenol as a new analytical reagent for flow-injection spectrophotometric determination of trace vanadium(V)

A flow injection method using 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol-(Nitro-PAPS) as a new chromogenic reagent is presented for sensitive and rapid determination of vanadium. Nitro-PAPS reacts with vanadium(V) in weakly acidic medium to form a water soluble complex of molar absorptivity of 8.0 × 10⁴L mol^–1 cm^–1 at 592 nm (maximum absorption wavelength), which permits the straightforward application of a flow injection system to the sensitive determination of vanadium. Under the optimum conditions established, a linear calibration graph was obtained in the range 1–120 ng mL^–1. The relative standard deviation for 60 ng mL^–1 vanadium was 2.2% (n = 5) and the limit of detection was 1 ng mL^–1. The sample throughput is about 40 h^–1. Most inorganic and organic anions examined did not interfere even at concentrations of 3000–6000 times of vanadium. Interference from cobalt(II), copper(II) and nickel(II) at 200ng mL^–1 levels can be overcome by the addition of N-(dithio-carboxy)sarcosine. The recoveries for each 20 and 10 ng mL^–1 vanadium added to the river water were 98 and 97%, respectively.The authors express their thanks to Miss Miho Suzuki and Miss Hiroyo Yamada for their experimental assistance in part.     

Determination of decabromodiphenyl ether in sediments using selective pressurized liquid extraction followed by GC–NCI-MS

A method based on selective pressurized liquid extraction (SPLE) followed by gas chromatography–negative ion chemical ionization-mass spectrometry (GC–NCI-MS) has been evaluated for analysis of decabromodiphenyl ether (PBDE-209) in sediment samples. Instrumental operating conditions such as source temperature and system pressure were optimized in the NCI-MS system, giving an instrumental detection limit of 2 pg. The limit of determination of the entire SPLE–GC–NCI-MS procedure was around 50 pg g^–1 dry weight (dw), with repeatability of replicates between 4 and 21% relative standard deviation. Application of the method to 13 different river and marine sediment samples collected in Spain revealed that levels of decabromodiphenyl ether ranged between 2 and 132 ng g^–1 dry weight.     

Optimization and Validation of a Headspace Solid-Phase Microextraction with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometric Detection for Quantification of Trace Aroma Compounds in Chinese Liquor (Baijiu)

The detection of trace aroma compounds in samples with complex matrices such as Chinese liquor (Baijiu) requires a combination of several methods, which makes the analysis process very complicated. Therefore, a headspace solid-phase microextraction (HS-SPME) method coupled with two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed for the quantitation of a large number of trace compounds in Baijiu. Optimization of extraction conditions via a series of experiments revealed that dilution of the alcohol content of 8 mL of Baijiu to 5%, followed by the addition of 3.0 g of NaCl and subsequent SPME extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. To check the matrix effects, various model Baijiu matrices were investigated in detail. The quantitative method was established through an optimized model synthetic solution, which can identify 119 aroma compounds (esters, alcohols, fatty acids, aldehydes and ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The developed procedure provided high recovery (86.79–117.94%), good repeatability (relative standard deviation < 9.93%), high linearity (R² > 0.99), and lower detection limits than reported methods. The method was successfully applied to study the composition of volatile compounds in different types of Baijiu. This research indicated that the optimized HS-SPME–GC×GC-TOFMS method was a valid and accurate procedure for the simultaneous determination of different types of trace compounds in Baijiu. This developed method will allow an improved analysis of other samples with complex matrices.     

Selective determination of total vanadium in water samples by cloud point extraction of its ternary complex

A highly sensitive micelle-mediated extraction methodology for the preconcentration of trace levels of vanadium as a prior step to its determination by flame atomic absorption spectrometry (FAAS) has been developed. Vanadium was complexed with 1-(2-pyridylazo)-2-naphthol (PAN) and hydrogen peroxide in acidic medium (0.2 mol L⁻¹ phosphoric acid) using Triton X-100 as surfactant and quantitatively extracted into a small volume of the surfactant-rich phase after centrifugation. The color reaction of vanadium ions with hydrogen peroxide and PAN in phosphoric acid medium is highly selective. The chemical variables affecting cloud point extraction (CPE) were evaluated and optimized. The R.S.D. for 5 replicate determinations at the 20 μg L⁻¹ V level was 3.6%. The calibration graph using the preconcentration system for vanadium was linear with a correlation coefficient of 0.99 at levels near the detection limits up to at least 0.6 μg L⁻¹. The method has good sensitivity and selectivity and was applied to the determination of trace amounts of vanadium in water samples with satisfactory result. The proposed method is a rare application of CPE-atomic spectrometry to vanadium assay, and is superior to most other similar methods, because its useful pH range is in the moderately acidic range achieved with phosphoric acid. At this pH, many potential interferents are not chelated with PAN, and iron(III) as the major interferent is bound in a stable phosphate complex.     

Selective Determination of Nickel in Biological Samples by High Performance Liquid Chromatography

A highly selective method for the determination of trace amounts of nickel(II) by high performance liquid chromatography was developed. 2-[(2-Hydroxyphenyl)azo]-4,5-diphenylimidazole (HAI) was used for pre-column derivatization of nickel(II) in reversed-phase chromatographic separation followed by spectrophotometric detection. In the presence of nickel(II), iron(III), cobalt(II), copper(II), cadmium(II), zinc(II), manganese(II), aluminum(III) and vanadium(V), only nickel(II) chelate with HAI gave a resolved peak in chromatograms with a C8-bonded reversed phase column and a 45% (w/w) acetonitrile-water mobile phase containing 1.0 × 10⁻⁴ mol kg⁻¹ ethylenediaminetetraacetic acid and 5.0 × 10⁻³ mol kg⁻¹ sodium acetate (pH 7.5). The nickel(II) chelate was detected spectrophotometrically at 585 nm. When 100 µL of a test solution was injected, the calibration graph was linear up to 240 pg for nickel(II), and the detection limit defined as three times the standard deviation of the reagent blank was 0.8 pg at 0.001 absorbance unit full scale. The proposed method was applied to the analysis of rice, tea leaves and mussels.     

A multiresidue method using ion-trap gas chromatography–tandem mass spectrometry with or without derivatisation with pentafluorobenzylbromide for the analysis of pesticides in the atmosphere

A multiresidue method using gas chromatography coupled to ion-trap tandem mass spectrometry (MS/MS) was developed for the analysis of 27 pesticides, commonly used in Alsace, in atmospheric samples (particle and gas phases). As pesticides are expected to be present at very low concentrations and in a complex matrix, the analytical method used was both highly selective and sensitive. These two properties were obtained by associating chromatography with ion-trap MS/MS. To develop this method, analysis of electron impact in single MS was first conducted to choose the parent ions of the pesticides studied. Among the 27 pesticides analysed, seven of them require a derivatisation step. This was the case of some ureas (chlorotoluron, diuron and isoproturon), phenoxy acids (2,4-dichlorophenoxyacetic acid, 4-chloro-2-methylphenoxyacetic acid and mecoprop) and of bromoxynil. The derivatisation was performed with success with pentafluorobenzylbromide. Then, a MS/MS method was optimised by parameters such as the radio frequency storage level and the collision-induced dissociation excitation voltage. Finally, a last step enabled the development of two calibrating programs based on the quantification of daughter ions for the 20 pesticides analysed directly (run 1) and for the seven pesticides which needed derivatisation (run 2). With this analytical procedure, the detection limits varied between 2.5 and 1,250 pg m^–3 depending on the compounds studied. This method was tested with success for atmospheric samples collected in Strasbourg (France) during intensive pesticide treatment in 2002.     

Determination of trace vanadium in soil by cloud point extraction and graphite furnace atomic absorption spectroscopy

This work describes a new analytical procedure for trace vanadium by graphite furnace atomic absorption spectroscopy coupled to cloud point extraction (CPE) as the separation-preconcentration method. The CPE behavior of vanadium using methylene blue as complex agent and Triton X-100 as a surfactant was investigated systematically. Under the optimized conditions, the detection limit was 0.7 ng · mL⁻¹, and the relative standard deviation was 4.3% for vanadium (c = 50.0 ng · mL⁻¹, n = 5). The recovery of vanadium was in the range of 98.9–102.8%. The method was applied to the analysis of vanadium in certified reference materials and real samples. The results obtained were in good agreement with the certified values. Correspondence: Xiashi Zhu, Key Laboratory of Environmental Material and Environmental Engineering of Jiangsu province/College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, P.R. China     

Stir bar sorptive extraction coupled to liquid chromatography for the analysis of strobilurin fungicides in fruit samples

A stir bar microextraction (SBSE) procedure for the determination of seven strobilurin fungicides in fruit samples using liquid chromatography (LC) and diode array detection (DAD) has been developed. The samples were sonicated in the presence of ethanol before submitting the extracts to SBSE. The incorporation of drazoxolon as an internal standard before SBSE allowed calibration without the need to use the standard additions method. Under the optimized conditions, detection limits were in the 0.3–2 ng g⁻¹ range, corresponding to trifloxystrobin and metominostrobin, respectively. The SBSE–LC–DAD procedure showed good repeatability (RSD below 11% in all cases) and provided recoveries of 80–105% from spiked samples. The method was applied to fifteen fruit samples, and low levels of pyraclostrobin and trifloxystrobin were found in two of them.     

Development of a new method for the separation of vanadium species and chloride interference removal using modified silica capillaries-DIN-ICP-MS

A new on-line method for the separation of vanadium (IV) and vanadium (V) as well as for the removal of ClO⁺ mass spectral interference on vanadium determination by quadrupole-ICP-MS has been developed. The sample introduction system consists of a modified fused silica capillary coupled to a direct injection nebuliser (DIN), between the solvent delivery system and the ICP. Fused silica capillaries were treated with different anion and cation exchanger reagents and were tested for the retention of Cl⁻ and the separation of vanadium ions at μg l⁻¹ levels. A suitable strong anion exchanger functional group (3-aminopropyltrimethoxy silane) was selected. Chlorine anions were retained in this anionic capillary and the separation between V(IV) and V(V) was possible in the pH range 2–4. The selections of instrumental ICP-MS conditions for the minimisation of the ClO+ interference were carefully considered. Factors affecting the chromatographic separation such as sample pH, sample flow rate, effect of methanol in the mobile phase and length of the capillary for the separation were optimised. The proposed methodology provides a simple and rapid method for vanadium speciation. A relative detection limit of 12 l⁻¹ (i.e. absolute detection limits of 120 pg) for V(IV) based on peak height measurements was obtained. The relative standard deviation for V(IV) was 2.4% for a 10 μl injection (n=6).     

SPME-GC-MSD for Determination of Nine Phenyl Compounds in Snow Water in Beijing China

Solid phase microextraction (SPME) then capillary gas chromatography with mass spectrometric detection have been used for determination of nine phenyl compounds in snow water in Beijing City. Headspace extraction with a fiber coated with 100 µm PDMS was used to extract the compounds. Extraction and desorption times were optimized at 8 and 2 min, respectively. Relative standard deviation (RSD) of the analytical method was found to be less than 5%. The linear range was wide and limits of detection were less than 5 ng mL⁻¹ for the nine target analytes. Several phenyl compounds at ng mL⁻¹ levels were detected in snow samples in Beijing, indicating the corresponding air pollution.     

Direct determination of nickel in gas oil by atomic absorption spectrometry with electrothermal atomization

A rapid graphite-furnace atomic absorption procedure with simple dilution of samples was tested for the direct determination of sub-ppm levels of nickel in gas oils. The selection of appropriate graphite-furnace parameters, the type of solvent and organometallic standard, the effect of gas oil concentration in diluted samples, precision, accuracy and detection limit were investigated. Sample dilution was necessary because of high viscosity. Results obtained by standard addition for heavy gas oils were confirmed by a wet-ashing flame atomic absorption procedure. The relative standard deviation (r.s.d.) for consecutive determinations of nickel in gas oil solution containing 19 μg Ni l^?1 was 3.1%, and day-to-day r.s.d. for a reference gas oil sample was 5.3%. Accuracy was determined with an NBS standard reference oil GM-5 (4.6 ± 4.7% relative error in four determinations). Recovery experiments gas 104 ± 12% of the added nickel.     

Flow-injection spectrophotometry of vanadium by catalysis of the bromate oxidation of N,N'-bis(2-hydroxyl-3-sulfopropyl)-tolidine

A highly sensitive flow-injection method is proposed for the catalytic determination of vanadium(V) at sub-nanogram per milliliter levels using a new indicator reaction. The method is based on the catalytic effect of vanadium(V) on the bromate oxidation of N,N′-bis(2-hydroxyl-3-sulfopropyl)-tolidine. 1,2-Dihydroxybenzene-3,5-disulfonate was used as an activator in the vanadium(V)-catalyzed reaction and significantly enhanced the sensitivity of the method. Vanadium(V) in the range 0.01-3.0 ng ml⁻¹ was easily determined with sampling rate of about 30 h⁻¹. Vanadium(IV) could be also determined. The limit of detection (S/N=3) was 0.008 ng ml⁻¹ and the relative standard deviations were 1.4 and 1.6% for ten determinations of 0.2 ng ml⁻¹ vanadium(IV) and vanadium(V), respectively. Interferences from metal ions could be suppressed by the addition of ethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid) as a masking agent. The proposed method was successfully applied to the determination of vanadium in water samples.     

Determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and environmental samples by gas chromatography with helium microwave plasma atomic emission detection

A highly sensitive and specific method is described for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and environmental samples by gas chromatography–plasma atomic emission detection (GC–AED). The procedure is simple, rapid and free from interferences. The absolute limit of detection is 0.5 fg of MMT (0.5×10⁻¹⁵ g) expressed as Mn. The precision for replicate injections ( n =5) of an MMT solution (10 pg Mn) was 2.8% relative standard deviation (RSD ). Applications of the method to analysis of gasoline (petrol), and preliminary results of the analyses of environmental samples such as air and roadside dirt, are given. © 1997 by John Wiley & Sons, Ltd.     

Vanadium in Italian waters: monitoring and speciation of V(IV) and V(V)

In this work, a highly sensitive method was developed to separate vanadium (IV) from vanadium (V), which are both contained in water at trace levels. A suitable strong anionic exchange column (SAX) loaded with disodium ethylendiaminetetraacetic acid (Na₂EDTA) was used to trap both vanadium species dissolved in 10–100 ml of water at pH 3. The vanadyl ion was selectively eluted by means of 15 ml of an aqueous solution containing Na₂EDTA, tetrabutylammonium hydroxide (TBA⁺OH⁻), and isopropanol (ⁱPr-OH) and was subsequently determined by atomic absorption spectroscopy with electrothermal atomization. The concentration of vanadate ion was calculated by subtracting the vanadyl concentration from the total concentration of vanadium. The optimal conditions for a selective elution were evaluated. The recovery of vanadium (IV) was 95% or better. The proposed method provides a simple procedure for the speciation of vanadium in aqueous matrices. The collection of the two forms could easily be carried out at the sampling site. Therefore, the risk of changing the concentration ratio between vanadium species was widely reduced. The detection limits were 1 μg/l for both species, when a 10-ml sample was eluted through the column. The method was applied successfully to vanadium speciation on different kinds of Italian volcanic water: Mount Etna (Sicily), Lake Bracciano and Castelli Romani (Latium).     

Tributyltin speciation in aquatic matrices by CGC-FPD and CGC-MS confirmation

An analytical procedure for the determination of tributyltin (TBT) in seawater, sediments and biota is described. Extraction of TBT as chloride is achieved by hydrochloric acid treatment followed by a liquid extraction using a modified solvent with a metal coordinating ligand, and a Grignard derivatization (CH₃MgCl). The organotin fraction was isolated from the derivatized extract by column chromatography. The final determination was accomplished by on-column capillary gas chromatography (CGC) coupled to a flame photometric detector (FPD) and mass spectrometry (MS) confirmation. The relative detection limits of the analytical procedure were dependent of the environmental compartment, 0.5 ng 1^–1 (as TBT) for seawater, and 0.1 ng g^–1 and 0.4 ng g^–1 for sediments and biota, respectively. The TBT recovery of fortified samples was in the range of 90% for water and biota, and of 60% in case of sediments. The reproducibility (RSD) of the whole procedure for three independent replicates was around 15%.     

Liquid chromatographic determination of vanadium in petroleum oils and mineral ore samples using 2-acetylpyridne-4-phenyl-3-thiosemicarbazone as derivatizing reagent

Liquid chromatographic method has been developed, based on precolumn derivatization of vanadium(V) with 2-acetylpyridine-4-phenyl-3-thiosemicarbazone (APPT). The complex is extracted in chloroform together with palladium(II), tin(II) and iron(III) and eluted and separated completely from Kromasil 100 C-18, 10 μm (25 cm × 4.6 mm i.d.) column with methanol:water:acetonitrile (60:30:10, v/v/v) with a flow rate of 1 ml/min. UV detection was at 260 nm. Linear calibration curve was obtained with 1-12.5 μg/ml vanadium(V) with detection limit of 8 ng/injection (20 μl). A number of metal ions tested did not affect the determination of vanadium. The test mixtures were analyzed for vanadium(IV) and vanadium(V) contents and relative% error was obtained ±1-8%. The method was applied for the determination of vanadium in petroleum oils and mineral ore samples with vanadium contents of 0.32-2.3 and 121.7-717.3 μg/g with R.S.D. of 1.5-4.5 and 0.38-4.7%, respectively. The results correlated with reported values and by atomic absorption spectrophotometry.     

Sensitive spectrophotometric determination of vanadium with 2-(5-bromo-2-pyridylazo)-5-diethyl-aminophenol (5-Br-PADAP)

A new sensitive and highly selective method is described for the spectrophotometric determination of microgram amounts of vanadium(V). First, vanadium is isolated by extraction withN-benzoyl-N-phenylhydroxylamine (BPHA) in chloroform from about 4M hydrochloric acid medium. Then, chloroform is evaporated and the residue mineralized with mixture of cone. perchloric and nitric acid. Finally, a colour reaction of vanadium(V) separated with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) in an acetate buffer (pH 4.5) gives a molar absorptivity of 5.48×10⁴l·mol^–1·cm^–1 at 585 nm. The proposed method was applied for the determination of traces of vanadium in aluminium samples. The results obtained show a good precision and accuracy of the method.     

Determination of methylcyclopentadienylmanganesetricarbonyl by gas chromatography—atomic absorption spectrometry at ng m-3 levels in air samples

A procedure is given for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) at ng m^-3 concentrations in air. The method involves trapping of MMT in a small segment of gas chromatographic column and then determination by gas chromatography with an electrothermal atomic absorption detector. The detection limit of the procedure is 0.05 ng m^-3. Air samples from an underground car-park (when MMT was detected) were found to contain between 0.1 and 0.3 ng m^-3 MMT. MMT was not detected in any of the street air samples taken.