Multiresidue Analysis of Organic Pollutants in Water by SPE with a C8 and SDVB Combined Cartridge

Abstract

A multi-component target method for screening purposes to determine organic pollutants of different polarities in water is reported. The following classes of chemicals were tested: base-neutral and acidic herbicides, phenolic compounds, polycyclic aromatic hydrocarbons and phthalic acid esters.

Data was initially obtained from the extraction of one liter of water sample, using separate octyl bonded porous silica (C8) and highly crosslinked polystyrene based polymer columns (SDVB) cartridges. A second set of data was obtained using for the extraction a combined cartridge containing both phases. The analysis was carried out directly by GC-MS in SIM mode, without any derivatisation, with the exception of acidic herbicides, derivatised with pentafluorobenzylbromide. The obtained results showed recoveries between 75% and 98% at two different spiking levels, with relative standard deviations below 15%.     

Flow Injection Analysis Using Potassium Permanganate: An Approach for Measuring Chemical Oxygen Demand in Organic Wastes and Waters

Abstract

A rapid and continuous analytical method based on flow injection analysis was developed for the determination of chemical oxygen demand due to organic substances in water pollution. Potassium permanganate and sulfuric acid solutions were individually pumped up as an oxidizing agent and glucose was used as a standard substance. The results for filtered organic waste and water samples were as reasonable as compared to those measured by the manual acidic permanganate method.     

Determination of Low Level Sulfides in Environmental Waters by Automated Gas Dialysis/Methylene Blue Colorimetry

Abstract

A sensitive and rapid automated method has been developed for the selective analysis of acid extractable sulfide in environmental samples by combining gas dialysis separation techniques with methylene blue detection procedures. Acid extractable sulfide is separated from the sample matrix by the gas dialysis membrane and subsequently trapped in a dilute sodium hydroxide receiving stream. This stream is reacted with N, N-dimethyl-p-phenylenediamine and ferric chloride to produce methylene blue which is then quantitated colorimetrically at 660 nm. For standards and nonturbid environmental samples, there is good agreement between the results obtained by this procedure and the standard methylene blue method. The effect of interferences on the accurate determination of sulfide by both methods was also examined and it was found that cupric ions significantly interfered with sulfide estimation. To obtain adequate sulfide recoveries in tap water and environmental samples ascorbic acid must be added as an antioxidant. A detection limit of 2 μg/L of sulfide has been obtained using this procedure.     

Analysis of 29 per- and polyfluorinated compounds in water,sediment, soil and sludge by liquid chromatography–tandem mass spectrometry

Several analytical methods were optimised for the analysis of 29 per- and polyfluoroalkyl substances (PFASs), including perfluorocarboxylic acids, perfluoroalkyl sulphonic acids and fluorotelomers (FTs), such as sulphonate, saturated carboxylic acid, unsaturated carboxylic acid, sulphonamide and sulphonamide betaine (FTAB), in environmental samples in order to assess pollution by PFASs around heavily contaminated sites. Non-filtered water samples were extracted, purified and pre-concentrated by a solid-phase extraction (SPE) procedure. Solid samples (sediments, soils and sludges) were extracted through solvent extraction under acidic conditions and thereafter purified and pre-concentrated using the same SPE procedure as for the water samples. An ultra-high performance liquid chromatography coupled to tandem mass spectrometry in negative electrospray ionisation mode was employed to separate and detect targeted compounds. Twelve labelled internal standards were used to provide an adequate correction compensating for matrix effects. The limits of quantification (LOQs) were between 4 and 10 ng/L in water depending on the analytes. For solid samples, the LOQs were 2 ng/g dry weight (dw) in sediments and soils, and 20 ng/g dw in sludges for all analytes. A surrogate parameter method based on the carboxylation of perfluoroalkyl acid precursors under basic pH conditions was furthermore implemented to estimate the occurrence of non-targeted PFAS compounds. In order to evaluate the reliability of these analytical methods, environmental samples collected around a training area in France, where aqueous fire-fighting foam is used, were analysed. Of all the compounds detected in these environmental samples, 6:2 FTAB was found in the highest concentrations.     

Determination of semivolatile organic compounds in environmental samples by gas chromatography/mass spectrometry after extraction by cyclic steam distillation

A method was developed for the multiple determination of semivolatile organic compounds found in groundwater, river water, seawater, sediment, and soil. Forty standard compounds were determined: n-alkenes, cycloalkanes, aromatic hydrocarbons, and polycyclic aromatic hydrocarbons. The compounds were isolated from water and soil samples by using an essential oil distillator (cyclic steam distillator) with hexane as a solvent. The extract was cleaned by using a silica gel cartridge with an acetone-hexane solution. The compounds were determined by using a gas chromatograph/mass spectrometer with 12 stable isotope-labeled compounds (surrogate compounds). The efficiencies of recoveries from water samples were 80.0-106% for groundwater, 80.1-106% for river water, and 81.2-103% for seawater. The relative standard deviation (RSD) values were 2.05-16.0% for groundwater, 3.22-16.6% for river water, and 4.45-16.0% for seawater. The efficiencies of recoveries from sediment and soil were 71.5-96.4% and 70.1-99.8%, respectively. RSD values ranged from 2.27 to 16.0% for sediment and from 2.12 to 15.1% for soil. Adjustment of recovery efficiencies of standard compounds by using surrogate compounds gave more accurate values. The present study proved that an essential oil distillator provides satisfactory results for multiple determinations of the semivolatile compounds in environmental waters, sediment, and soil.     

Analysis of Trace Levels of Volatile Organic Contaminants in Municipal Drinking Water by Glass Capillary Gas Chromatography Using Simultaneous Flame Ionization and Electron Capture Detection

Abstract

A glass capillary gas chromatographic system using simultaneous flame ionization (FID) and electron capture (ECD) detection has been employed for the analysis of trace volatile organic pollutants in a municipal drinking water supply. The use of dual detectors with glass capillary columns allows resolution and detection of both halogenated and non-halogenated compounds simultaneously at less than microgram per liter (ppb) concentrations. By using diethyl ether as a solvent in preparing standard solutions of volatile organic compounds, standardization is made more accurate due to a reduction in solvent masking of early eluting peaks of interest. Additionally, ether shows promise for use in an internal standard method for quantification of VOA. These techniques were found to alleviate problems previously encountered in the analysis of purgeable organics and are described.     

Monitoring of Polychlorinated Biphenyls in Surface Water Using Liquid Extraction,GC/MS,and GC/ECD

Abstract

A rapid and reliable analytical method, at trace level concentration was developed and validated for monitoring polychlorinated biphenyls (PCBs) in Jordanian surface water. The method combines the advantage of liquid extraction together with gas chromatography‐mass spectrometry (GC/MS) and gas chromatography‐electron capture detector (GC/ECD). The performance of the method was evaluated by analyzing certified reference material (CRM) of the analytes and applied on real water samples collected from different sites in Jordan. A mixture of 60∶40 dichloromethan‐petroleum ether was chosen as a convenient binary solvent for liquid–liquid extraction. The GC conditions for GC/MS were optimized using He as a carrier gas, temperature programming, and chlorpropham as an internal standard (IS).

The conditions for GC/ECD were performed using N₂ gas and a temperature program from 160 to 280°C with different increasing rates. The method of GC/MS in the selective ion mode (SIM) gave linear relationships for all PCBs tested between 0.60–6.0 µg/l with R ²=0.9934 (n=7×18). Recoveries from spiked water samples ranged between 87.6 and 91.4%. The mean accuracy and precision obtained were 4.9% and 2.16%, respectively. The mean of detection limit was 0.14±0.04 µg/l. In GC/ECD, linear relationships for all PCBs examined over the range of 0.3–2.4 µg/l was verified as characterized by a linear regression equation and correlation coefficient, R ²=0.9915 (n=12). The average precision and accuracy were 4.86% and 5.21%, respectively. Analyses results clarified that none of the examined Jordanian water samples contained any of the searched for PCBs within the detection limit achieved.     

Assessment of Organic Source Contributions in Coastal Waters by Principal Component and Factor Analysis of the Dissolved and Particulate Hydrocarbon and Fatty Acid Contents

Abstract

Principal component (PCA) and factor analysis (FA) are evaluated for the interpretation of the information contained in large datasets resulting from the study of environmental samples by gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS). A case involving the identification and quantitation of 64 variables (hydrocarbons and fatty acids) in 87 water samples (dissolved and particulate fractions) of a coastal system (Ebre Delta) has been selected for examination.

PCA has evidenced important differences between the dissolved and particulate materials, as well as between the particulates collected in the bays and those obtained in the river and channels. PCA has also allowed the identification of outlier samples in the dissolved fraction. Independent application of FA to each of these groups has provided a useful method for the characterization of diverse algal, terrestrial, microbial and anthropogenic inputs. Direct correspondences between these source inputs and factor loadings have provided a selection of representative components of each contribution in the coastal system.     

Impurities Released from Extractive Phases Used in the Analysis of Pesticides

Abstract

Elution fractions relative to solid phase extraction (SPE) procedures using C-18 bonded silica and Carbopack B columns plus C-18 membranes have been analyzed by gas chromatography-mass spectrometry (GC-MS) for the characterization of interfering compounds from the phases. Alkanes, alkenes, phthalates and some silyl compounds (silanols, siloxanes) have been tentatively identified. Experiments on commercial C-18 phases prepacked in plastic tubes show that the increased interference compared to the phases alone comes from the polymer container. N-butylbenzensulfonamide (NBBSA) was identified as causing interference when the extraction device used for SPE involved plastic components. Increasing amounts of silanol interferences released from the C-18 phases were observed after passage of the water sample, depending on the acidic pH, as evidence of the hydrolysis of the bonded silica.     

A Fluorescence-Based Sensor for Ammonium and Nitrate

Abstract

Measurement of nitrite and nitrate in rain samples was performed using a fluorescence based sensor. Nitrite and nitrate were reduced to ammonia using Devarda's alloy, and the gas was then passed through a membrane and reacted with o-phthalaldehyde. A linear relationship between the nitrate concentration and the luminescence intensity was observed over the concentration range of 1 – 5 mg/1, with a relative standard deviation (RSD) of 2.3% at a nitrate concentration of 1 mg/1 (n = 5). The system did not show any response toward sulfate or chloride. Results obtained from the measurement of river water samples using the sensor showed good agreement with those obtained using a conventional method.     

A Rapid High Pressure Liquid Chromatographic Assay of Benoxaprofen in Plasma

Abstract

A rapid high-performance liquid chromatographic assay for the determination of the anti-inflammatory drug benoxaprofen in human plasma, is described. Plasma samples of 1.0 ml, to which benoxaprofen, and warfarin as an internal standard, had been added, were extracted with ether under acidic conditions. The samples were analyzed on a MicroPak CN-10 column using 25% acetonitrile in water (pH 2.5 with phosphoric acid). Detection was made on a variable wavelength UV absorbance detector at 309 nm.

Samples containing 0.5–10 μg benoxaprofen gave a mean extraction recovery from control plasma of 90.6 ± 6.8% (n=18). Stability tests have shown that benoxaprofen in plasma is stable for at least two weeks after freezing.     

Comparison of Three Techniques for Lipid Removal from Seal Blubber: Gel Permeation,Acid Treatment,and Dialysis with Semipermeable Membrane

Abstract

Harbor seal blubber samples were analyzed for PCDD/Fs and PCBs by splitting the initial extract into three aliquots and applying three different techniques for lipid removal (the first step of sample cleanup methodology for GC-HRMS analysis): gel permeation chromatography (GPC), sulfuric acid treatment, and dialysis through semipermeable membrane. Correlation coefficients of analyte concentrations obtained from three sets of replicate samples ranged from 0.965 to 0.994. In addition, a number of seal blubber samples were processed without pre-extraction using only the dialysis technique. The analyte concentrations in these samples correlated well with the analyte concentrations obtained from dialyzed blubber extracts (correlation higher than 0.998). For all analyses (PCDD/Fs, NO- and MO-PCBs) the average surrogate standard recoveries for the GPC and dialysis techniques varied from 68 to 111%. The recoveries for PCDD/Fs and MO-PCBs standards ranged from 61 to 89% and 36 to 43% for the NO-PCBs when the acid treatment technique was used. Dialysis was proven to be an efficient technique for lipid removal of biological samples in comparison with the GPC and acid treatment techniques.     

Rapid and Sensitive Analysis of Diclofenac in Human Plasma by GC/SIM/MS

ABSTRACT

An analytical method for the determination of diclofenac with tolfenamic acid as the internal standard was developed and validated in human plasma by capillary gas chromatography-mass spectrometry (GC/MS). After the addition of the internal standard, the compounds were extracted from plasma at acidic pH into diethylether, which was then evaporated to dryness. The compounds were derivatized with pentafluoropropionic anhydride (PFPA) and a mixture (1000:2:3, v/w/w) of N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), ammonium iodide (NH₄I), and dithioerythritol (DTE). They were determined by GC/MS at m/z 349 (a molecular ion) for diclofenac and m/z 270 (a base ion) for tolfenamic acid. The recovery of this procedure was 97.8%, and the linearity for calibration was 0.9907 as the coefficient factor. The detection and quantitation limits were 0.1 and 0.5 ng/mL, respectively.     

A Comparison of Solid-Phase Extraction Techniques for Assay of Drugs in Aqueous and Human Plasma Samples

Abstract

Six commercially available solid adsorbent materials were evaluated for their applicability as effective tools for extraction of drugs from aqueous and human plasma samples. Ten model compounds were selected as representative of the acidic, basic, amphoteric, hydrophobic, and hydrophilic drug classes. Percent recovery and precision data for each model drug on each solid adsorbent material were calculated using spiked water and/or plasma samples. Octadecylsilane materials were the best overall choice for extraction of the different chemical classes of drugs from water and plasma samples, giving both highest recovery and best reproducibility data for a majority of the drugs studied. It was also determined that good extractability for basic drugs could be obtained using either XAD-2, Clin-eht® or cyanopropyl columns. In addition, XAD-2 gave good recoveries of amphoteric compounds and Clin-elut® was good for hydrophobic drugs.     

Flow Injection Analysis of Hydrogen Peroxide,Sulfite, Formaldehyde and Hydroxymethanesulfonic Acid in Precipitation Samples

Abstract

Hydroxymethanesulfonic acid (HMSA), the reaction product of sulfite and formaldehyde plays an important part in the aqueous phase conversion of sulfite to sulfate. HMSA is fairly stable under acidic conditions and in presence of hydrogen peroxide. Sulfite is unstable under these conditions.

A flow injection set-up was developed, which allows the determination of H₂O₂, sulfite, formaldehyde and hydroxymethanesulfonic acid.

H₂O₂ analysis by amperometric detection offers the possibility of a simple, robust field instrument. The detection limit is 5μg/l and the method is linear up to 5mg/l.

Based on the 4,4-dithiodipyridine/sulfite reaction selective and sensitive spectrophotometric detections were developed for sulfite, formaldehyde and hydroxymethanesulfonic acid. The detection limit of these compounds is 50μg/l and the method is linear up to 5mg/l.

A large fraction of S(IV) is present as HMSA in fog, dew and precipitation samples in The Netherlands.     

Membrane Extraction of Volatile Organic Compounds in Combination with Mobile Gas Chromatographic Analysis

Abstract

The field of application of a mobile gas chromatographic device (Airmobtx monitor HC 1000 manufactured by Airmotec GmbH) originally conceived for the analysis of BTEX in air was extended to water analysis by using it in conjunction with membrane extraction. Volatile organic compounds diffuse out of water through a hollow fibre or flat membrane, are enriched onto sorption tubes integrated in the device, and then thermally desorbed and analysed by the gas chromatograph/flame ionisation detector. The suitability of various flat membranes and hollow fibres was investigated. Maximum extraction efficiency was obtained with a silicone hollow fibre measuring 0.3 m long, and with an inner diameter of 0.7 mm and a wall thickness of 100 μm. The extraction parameters were optimised. The linear dynamic range of the optimised method spans two orders of magnitude and the detection limits were found to be 0.1 μg/L for all BTEX compounds. By way of environmental applications, highly contaminated groundwater samples were analysed. The results correspond well to those achieved using conventional headspace/gas chromatography/flame ionisation detection.     

Clay Catalysis: Synthesis of Organosulphur Synthons

Abstract

The Montmorillonite KSF catalyses the synthesis of a large variety of organic sulphur compounds from carbonyl compounds: dithianes, thioacetals, thioketals, thiochromanes.

Clay minerals are known to cataiyse a variety of organic reactions(1). In these reaction, the clay catalyst acts as a solid Bronsted acid. One of the most acidic, Montmorillonite manufactured by Sud Chemie, is the KSF catalyst. Clay is inexpensive and offers several advantages to the classic acid: a strong acidity (Ho = ?8 to ?9), no corrosive action, selectivity and easy work-up.

We report here, that KSF clay is a convenient catalyst for the synthesis of useful thio-organic reagents : dithianes, thioketals, trithioorthoformiates, thiochromanes. The condensations of the thiol with the carbonyl compounds were completed in refluxing toluene in presence of KSF with the azeotropic separation of water. Generally the pure compound was obtained in these reactions and the work-up very simple.     

Simple Multiresidue Determination of Fluoroquinolones in Bovine Milk by Liquid Chromatography with Fluorescence Detection

Abstract

A simple and sensitive method for the simultaneous determination of five fluoroquinolones (ciprofloxacin, enrofloxacin, danofloxacin, difloxacin, and sarafloxacin) in bovine milk was developed. Protein precipitation from milk samples was achieved by the addition of acetonitrile and o‐phosphoric acid. Acetonitrile was removed with dichloromethane, leaving the fluoroquinolones in the acid aqueous extract. The aqueous extract was analyzed by liquid chromatography with fluorescence detection (LC–FD). The mobile phase was composed of acetonitrile and 10 mM citrate buffer solution of pH 4.5, with an initial composition of acetonitrile‐water (12∶88, v/v) and using linear gradient elution. Norfloxacin was used as an internal standard. The limits of detection found ranged from 1 to 6 ng · mL^?1 and were below the maximum residue limits (MRLs) established by the European Union. The proposed method was applied to the determination of these compounds in different bovine milk samples. Method validation was carried out by a recovery assay.     

Determination of Halide Traces in Environmental Samples by Mass Spectrometric Isotope Dilution Analysis

Abstract

Since 1985, the Goulden large-sample extractor (GLSE) has been used to isolate a broad array of trace-organic contaminants from large volumes of water. In this study, field-applied quality control measures, including matrix and surrogate spikes and blanks, were used to monitor method performance from GLSE extraction through GC-MS analysis. The method was applied to the determination of multiple classes of pesticides isolated from 4- to 112-L filtered surface-water samples. Average recoveries of six surrogate compounds ranged from 84 ± 18% for [²H₁₀]diazinon to 15 ± 13% for 4,4′-[²H₈]DDT, the low recoveries for which were largely a result of unmonitored breakdown of this surrogate by the GC injection system. Field-matrix-spike samples were prepared by fortifying 10-L, 35-L, and 110-L filtered surface-water samples with 68 pesticides to amended concentrations of 11-to 50-ng/L each. Recoveries ranged from not detected to greater than 100%. Variability in pesticide recoveries from triplicate 10-L water samples collected at one site averaged 5.7% relative standard deviation and did not exceed 19%.     

Multiresidue Analysis of Pesticides in Water from Rice Cultures by On-line Solid Phase Extraction Followed by LC-DAD

Abstract

An automated on-line solid phase extraction procedure followed by liquid chromatography with diode array detection was investigated for the determination of different classes of pesticides in water samples containing varied amount of humic substances. The different pesticides used were: carbendazin, carbofuran, atrazine, diuron, propanil, molinate, alachlor, parathion-ethyl, diazinon, trifluralin and the degradation products deisopropylatrazine and deethylatrazine. Humic substances extracted from a Brazilian sediment were used from 5 to 80 mg/l and their influence on recoveries was evaluated in neutral and acidic media. Recoveries higher than 70% were obtained for all the pesticides, from the preconcentration of 75 ml of aqueous sample fortified at 2 ng/ml using precolumns packed with PLRP-S. Good recoveries were obtained at neutral pH for most of the analytes up to 40 mg/l of humic acid. Only at 80 mg/l the recoveries were significantly affected, both at acidic and neutral pH. The method was applied to the determination of pesticides in river water spiked at 0.1 to 1 ng/ml. Detection limits obtained for water containing 10 mg/l of humic acid were between 0.05 and 0.3 ng/ml.