Development and validation of a rapid multiresidue method for pesticide determination using gas chromatography-mass spectrometry: a realistic case in vineyard soils

A rapid and simultaneous method for residue identification and quantification for seven pesticides in agricultural soils has been developed to study a realistic situation in vineyard. The target compounds are two insecticides, two herbicides and three fungicides, from different chemical families. The procedure is based on a pressurized liquid extraction (PLE) with acetone, before a multiresidue GC-MS analysis. The recovery of PLE is between 53.8 ± 2.4 and 99.9 ± 4.4% according to pesticide. A limit of detection (LOD) between 1.4 and 4.6 μg kg⁻¹ of dry soil was obtained for five analytes. This procedure for testing soil contamination is sensitive and easy to perform.     

Montmorillonite as an adsorbent for extraction and concentration of atrazine, propazine, deethylatrazine, deisopropylatrazine and hydroxyatrazine

Adsorption properties of the clay mineral montmorillonite in the potassium homoionic form (KMT) was investigated to achieve the extraction and concentration of the herbicides atrazine (AT) and propazine (PROP), as well as the main degradation products of atrazine, namely deethylatrazine (DEA), deisopropylatrazine (DIA) and hydroxyatrazine (ATOH). A batch approach was proposed, with recovery percentages for AT, PROP and DIA higher than 90% at concentrations of 0.50 and 2.50 μg L⁻¹. For DEA and ATOH, however, low recoveries were obtained. For DEA, this fact can be explained by its low K_d with KMT, contrary to ATOH, which interacts strongly with the mineral surface, hindering the complete desorption and hence, generating low recovery percentages. The influence of pH, ionic strength and humic acid was studied, and a comparison with the C₁₈ phase as SPE cartridges was carried out. Montmorillonite showed a similar performance to commercial cartridge for concentrations of AT, DEA and PROP, but better recoveries for DIA was obtained using the clay mineral. For ATOH the recovery was also higher on the clay mineral, although for this compound the most suitable SPE cartridge is constituted by cation exchange resin. After the concentration and elution steps, the 0.50 and 2.50 μg L⁻¹ gave chromatographic peak areas that could be easily quantified with an analytical curve obtained in the concentration range between 7.5 and 100 μg L⁻¹. The obtained concentration factors are suitable to allow the application of the method to the monitoring of triazine residues in drinking water.     

On-line solid-phase extraction of large-volume injections coupled to liquid chromatography-tandem mass spectrometry for the quantitation and confirmation of 14 selected trace organic contaminants in drinking and surface water

We describe the development and validation of an on-line solid-phase extraction of large-volume injections coupled to liquid chromatography-tandem mass spectrometry method for the simultaneous quantitation and confirmation of 14 selected trace organic contaminants in drinking and surface water. Selected compounds were: anti-infectives (clarithromycin, sulfamethoxazole and trimethoprim), an anticonvulsant (carbamazepine) and its transformation product 10,11-dihydrocarbamazepine, an antihypertensive (enalapril), antineoplastics (cyclophosphamide and methotrexate), herbicides (atrazine, cyanazine, and simazine) and two of their transformation products (deethylatrazine and deisopropylatrazine) and an antiseptic (triclocarban). The breakthrough volume determinations showed that out of all the investigated sorbents, the Strata-X on-line solid-phase extraction column showed the best performance. The method used a load volume of 10.0 mL and was validated using the corresponding matrices, yielding for most compounds, R² > 0.99. Extraction recoveries ranged from 60 to 109%. The intra- and inter-day precision were <14 and <16%, respectively. The method detection limits ranged from 0.6 to 6 ng L⁻¹. Matrix effects were in general low. The performance of the on-line method was demonstrated with the analysis of real water samples. The application of alternative techniques of confirmation was also explored using accurate mass measurements on a time-of-flight mass spectrometer and the data-dependent reverse energy ramp scan on a triple quadrupole.     

Determination of mercury species with a resin functionalized with a 1,2-bis(o-aminophenylthio)ethane moiety

A method for the simultaneous preconcentration and determination of Hg(II) and MeHg(I) at the ng ml⁻¹ level has been developed. This method is based on solid phase extraction using a newly synthesized chelating resin containing nitrogen and sulphur donor sites of the 1,2-bis(o-aminophenylthio)ethane moiety that is very selective for mercury. The characterization of the resin has been carried out by elemental analyses, infrared spectral data, thermogravimetric analysis and metal ion capacities. The resin is highly selective for Hg(II) and MeHg(I) with an exchange capacity of 0.38 and 0.30 mmol g⁻¹, respectively. Various parameters like pH, column flow rate, desorbing agents are optimized. Cold vapour atomic absorption spectrometry (CVAAS) was used to measure the concentration of both species of mercury. The calibration graph was linear upto 10 ng ml⁻¹ with a 3σ detection limit of 0.09 ng ml⁻¹. The recovery of Hg(II) and MeHg(I) was found to be 98.9±2.0 and 98.0±1.1%, respectively. The method has been used for routine determination of trace levels of mercury species in natural waters to comply with more stringent regulations.     

Determination of 15 isomers of chlorobenzoic acid in soil samples using accelerated sample extraction followed by liquid chromatography

A study was conducted to elaborate a fast, simple and efficient method for determination of 15 isomers chlorobenzoic acids (CBAs) in soil using HPLC-UV. Artificially contaminated soil samples were extracted using accelerated solvent extraction (ASE) with 1% acetic acid in a mixture of hexane and acetone (1:1, V/V) under a pressure of 10.34 MPa and temperature of 150 °C. The recovery of the ASE method was above 82%. The extracts were concentrated; dimethyl sulfoxide was used to prevent CBA volatilization and the final analysis was performed with a C18 XBridge HPLC column employing a mobile phase consisting of acetonitrile and 0.1% trifluoracetic acid in water. A HPLC procedure with gradient elution and UV detection was developed and validated. The method exhibited a linear range for 2-CBA; 2,6-CBA; 3-CBA; 4-CBA; 2,3-CBA; 2,3,6-CBA; 2,5-CBA; and 2,4-CBA from 5 to 120 μg/mL with a limit of quantification (LOQ) of 5 μg/mL, RSD from 2.42 to 9.42% and accuracy from 82 ± 2 to 103 ± 3%. The linear range of determination of 2,4,6-CBA, 3,4-CBA, 2,3,5,6-CBA, 3,5-CBA, 2,3,5-CBA, 2,3,4,5,6-CBA and 2,3,4,5-CBA was 10-120 μg/mL with LOQ 10 μg/mL, RSD from 0.74 to 5.84% and accuracy from 94 ± 1 to 114 ± 1%. The optimized analytical procedure was finally applied on two historically PCB contaminated soils and 9 CBAs were quantified in the samples.     

Alumina modified by dimethyl sulfoxide as a new selective solid phase extractor for separation and preconcentration of inorganic mercury(II)

Dimethyl sulfoxide (DMSO) was simply immobilized to neutral alumina via quite strong hydrogen bonding between sulfoxide oxygen and surface alumina hydroxo groups. The produced alumina-modified dimethyl sulfoxide (AMDMSO) solid phase (SP)-extractor experienced high thermal and medium stability. Moreover, the small and compact size of DMSO moiety permit high surface coverage evaluated to be 2.1 ± 0.1 mmol g⁻¹ of alumina. Hg(II) uptake was 1.90 mmol g⁻¹(distribution coefficient log K_d = 5.658) at pH 1.0 or 2.0, 1.68 mmol g⁻¹ (log K_d = 4.067) at pH 3.0 or 4.0 while the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low values 0.513-0.118 mmol g⁻¹ (log K_d < 3.0) in the pH range 4.0-7.0. A mechanism was suggested to explain the unique uptake of Hg(II) ions by binding as neutral and chloroanionic species predominate at pH values ≤ 3.0 of a medium rich in chloride ions. A direct and fast batch separation mode was achieved successfully to retain selectively Hg(II) in presence of other eight coexisting metal ions. Thus, Hg(II) was completely retained; Ca(II), Co(II), Ni(II) and Cd(II) were not retained, while Pb(II), Cu(II), Zn(II) and Fe(III) exhibited very low percentage retention evaluated to be 0.42, 0.49, 1.4 and 5.43%, respectively. The utility of the new modified alumina sorbent for concentrating of ultratrace amounts of Hg(II) was performed by percolating 2 l of doubly distilled water, drinking tap water, and Nile river water spiked with 10 ng/l over 100 mg of the sorbent packed in a minicolumn used as a thin layer enrichment bed prior to the determination by CV-AAS. The high recovery values obtained (98.5 ± 0.5, 98.5 ± 0.5 and 103.0 ± 1.0) based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51-0.97%, N = 3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.     

Dispersive solid-phase extraction followed by dispersive liquid–liquid microextraction for the determination of some sulfonylurea herbicides in soil by high-performance liquid chromatography

Dispersive solid-phase extraction (DSPE) combined with dispersive liquid–liquid microextraction (DLLME) has been developed as a new approach for the extraction of four sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl and chlorimuron-ethyl) in soil prior to high-performance liquid chromatography with diode array detection (HPLC-DAD). In the DSPE-DLLME, sulfonylurea herbicides were first extracted from soil sample into acetone–0.15 mol L⁻¹ NaHCO₃ (2:8, v/v). The clean-up of the extract by DSPE was carried out by directly adding C₁₈ sorbent into the extract solution, followed by shaking and filtration. After the pH of the filtrate was adjusted to 2.0 with 2 mol L⁻¹ HCl, 60.0 μL chlorobenzene (as extraction solvent) was added into 5.0 mL of it for DLLME procedure (the acetone contained in the solution also acted as dispersive solvent). Under the optimum conditions, the enrichment factors for the compounds were in the range between 102 and 216. The linearity of the method was in the range from 5.0 to 200 ng g⁻¹ with the correlation coefficients (r) ranging from 0.9967 to 0.9987. The method detection limits were 0.5–1.2 ng g⁻¹. The relative standard deviations varied from 5.2% to 7.2% (n = 5). The relative recoveries of the four sulfonylurea herbicides from soil samples at spiking levels of 6.0, 20.0 and 60.0 ng g⁻¹ were in the range between 76.3% and 92.5%. The proposed method has been successfully applied to the analysis of the four target sulfonylurea herbicides in soil samples, and a satisfactory result was obtained.     

Stereoselective quantitation of mecoprop and dichlorprop in natural waters by supramolecular solvent-based microextraction,chiral liquid chromatography and tandem mass spectrometry

Liquid chromatography (LC)/tandem mass spectrometry (MS/MS) after supramolecular solvent-based microextraction (SUSME) was firstly used in this work for the enantioselective determination of chiral pesticides in natural waters. The method developed for the quantitation of the R- and S-enantiomers of mecoprop (MCPP) and dichlorprop (DCPP) involved the extraction of the herbicides in a supramolecular solvent (SUPRAS) made up of reverse aggregates of dodecanoic acid (DoA), analyte re-extraction in acetate buffer (pH = 5.0), separation of the target enantiomers on a chiral column of permethylated α-cyclodextrin under isocratic conditions, and detection of the daughter ions (m/z = 140.9 and 160.6 for MCPP and DCPP, respectively) using a hybrid triple quadrupole mass spectrometer equipped with an electrospray source operating in the negative ion mode. Similar recoveries (ca. 75%) and actual concentration factors (ca. 94) were obtained for both phenoxypropanoic acids (PPAs). The quantitation limits were 1 ng L⁻¹ for R- and S-MCPP, and 4 ng L⁻¹ for R- and S-DCPP, and the precision, expressed as relative standard deviation (n = 6) was in the ranges 2.4–2.7% ([R-MCPP] = [S-MCPP] = 5 ng L⁻¹ and [R-DCPP] = [S-DCPP] = 15 ng L⁻¹) and 1.6–1.8% (100 ng L⁻¹ of each enantiomer). The SUSME-LC–MS/MS method was successfully applied to the determination of the enantiomers of MCPP and DCPP in river and underground waters, fortified at concentrations between 15 and 180 ng L⁻¹ at variable enantiomeric ratios (ER = 1–9).     

Stability indicating high-performance thin-layer chromatographic determination of gatifloxacin as bulk drug and from polymeric nanoparticles

A simple, sensitive, selective, precise and stability indicating high-performance thin-layer chromatographic method for determination of gatifloxacin both as a bulk drug and from polymeric nanoparticles was developed and validated as per the International Conference on Harmonization (ICH) guidelines. The method employed thin-layer chromatography (TLC) aluminium plates precoated with silica gel 60F-254 as the stationary phase and the mobile phase consisted of n-propanol-methanol-concentrated ammonia solution (25%) (5:1:0.9, v/v/v). This solvent system was found to give compact spots for gatifloxacin (R_f value of 0.60 ± 0.02). Densitometric analysis of gatifloxacin was carried out in the absorbance mode at 292 nm. The linear regression analysis data for the calibration plots showed good linear relationship with r = 0.9953 with respect to peak area in the concentration range of 400-1200 ng spot⁻¹. The mean value (±S.D.) of slope and intercept were 9.66 ± 0.05 and 956.33 ± 27.67, respectively. The method was validated for precision, accuracy, ruggedness and recovery. The limits of detection and quantitation were 2.73 and 8.27 ng spot⁻¹, respectively. Gatifloxacin was subjected to acid and alkali hydrolysis, oxidation, photodegradation and dry heat treatment. The drug undergoes degradation under acidic and basic conditions and upon wet and dry heat treatment. The degraded products were well separated from the pure drug. The statistical analysis proves that the developed method for quantification of gatifloxacin as bulk drug and from polymeric nanoparticles is reproducible and selective. As the method could effectively separate the drug from its degradation products, it can be employed as stability-indicating one.     

HPLC-UV and HPLC-MSn multiresidue determination of amidosulfuron, azimsulfuron, nicosulfuron, rimsulfuron, thifensulfuron methyl, tribenuron methyl and azoxystrobin in surface waters

The paper presents a new HPLC method, with UV and MSⁿ detection, for the determination of seven pesticides, including the sulfonylurea herbicides amidosulfuron, azimsulfuron, nicosulfuron, rimsulfuron, thifensulfuron methyl, tribenuron methyl, and the fungicide azoxystrobin characterised by a methoxyacrilate structure. The methodology consists of a preconcentration/SPE (solid phase extraction) step and HPLC-UV (240 nm detection wavelength)-MSⁿ analysis. Under the optimised conditions and after a 1000/1 preconcentration factor, the limits of detection were lower than 14.5 ng L⁻¹ for UV detection and lower than 8.1 ng L⁻¹ for MS detection. The limits of quantification were lower than 48.3 ng L⁻¹ in UV detection and than 26.9 ng L⁻¹ in MSⁿ detection. The analysis of two samples, spiked with a mixture of the pesticides at threshold level concentrations, gave more than 60% recovery.     

Species selective preconcentration and quantification of gold nanoparticles using cloud point extraction and electrothermal atomic absorption spectrometry

The determination of metallic nanoparticles in environmental samples requires sample pretreatment that ideally combines pre-concentration and species selectivity. With cloud point extraction (CPE) using the surfactant Triton X-114 we present a simple and cost effective separation technique that meets both criteria. Effective separation of ionic gold species and Au nanoparticles (Au-NPs) is achieved by using sodium thiosulphate as a complexing agent. The extraction efficiency for Au-NP ranged from 1.01 ± 0.06 (particle size 2 nm) to 0.52 ± 0.16 (particle size 150 nm). An enrichment factor of 80 and a low limit of detection of 5 ng L⁻¹ is achieved using electrothermal atomic absorption spectrometry (ET-AAS) for quantification. TEM measurements showed that the particle size is not affected by the CPE process. Natural organic matter (NOM) is tolerated up to a concentration of 10 mg L⁻¹. The precision of the method expressed as the standard deviation of 12 replicates at an Au-NP concentration of 100 ng L⁻¹ is 9.5%. A relation between particle concentration and the extraction efficiency was not observed. Spiking experiments showed a recovery higher than 91% for environmental water samples.     

High-performance liquid chromatography and pharmacokinetics of aceclofenac in rats

A simple and sensitive high-performance liquid chromatographic (HPLC) method was developed for quantification of aceclofenac in rat plasma. Ibuprofen was used as an internal standard (IS). The present method used protein precipitation for extraction of aceclofenac from rat plasma. Separation was carried out on reversed-phase C₁₈ column (250 mm × 4.6 mm, 5 μ) and the column effluent was monitored by UV detector at 282 nm. The mobile phase used was methanol-triethylamine (pH 7.0; 0.3% v/v in Milli-Q water) (60:40%, v/v) at a flow rate of 1.0 mL min⁻¹. This method was linear over the range of 50.0-3500.0 ng mL⁻¹ with regression coefficient greater than 0.99. The mean recovery of aceclofenac and IS were 84.62 ± 3.23 and 89.19 ± 1.57%, respectively and the method was found to be precise, accurate, and specific during the study. The method was successfully applied for pharmacokinetic study of aceclofenac in rats.     

Determination of osthole in rat plasma by high-performance liquid chromatograph using cloud-point extraction

A new straightforward method based on cloud-point extraction (CPE) was developed to determine osthole in rat plasma by reversed phase high-performance liquid chromatography with ultraviolet detection using a photodiode array detector. The non-ionic surfactant Triton X-114 was chosen as the extract solvent. Variable parameters affecting the CPE efficiency were evaluated and optimized. A Zorbax SB-C₁₈ column was used for elution separation at 25 °C with detection wavelength at 322 nm. Under the optimum conditions, the method was shown to be reproducible and reliable with intra-day precision below 7.62%, inter-day precision below 6.37%, and accuracy within ±5.02% and mean extraction recovery more than 90.4%, which were all calculated using a range of spiked samples at three concentrations of 0.5, 5.0 and 15.0 μg mL⁻¹ for osthole in plasma. The calibration curve for the analyte was linear in the range from 0.1 to 20 μg mL⁻¹ with the correlation coefficients greater than 0.9981. Limit of detection (S/N = 3) was less than 0.03 μg mL⁻¹and limit of quantification (S/N = 10) was less than 0.1 μg mL⁻¹. After strict validation, the method was successfully applied to the pharmacokinetic study of osthole in rats after oral and intravenous administration, respectively.     

Sorption of As(V) from waters using chitosan and chitosan-immobilized sodium silicate prior to atomic spectrometric determination

A natural biosorbent containing amine functional groups, chitosan, and a novel sorbent, chitosan-immobilized sodium silicate, were prepared and utilized for the selective sorption of As(V) from waters prior to its determination by atomic spectrometric techniques, namely, hydride generation atomic absorption spectrometry (HGAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Chitosan was synthesized from chitin and sodium silicate was used as the immobilization matrix due to its straightforward synthesis. Through sequential sorption studies, it was shown that chitosan-immobilized sodium silicate has exhibited a better chemical stability than the chitosan itself which demonstrates the advantage of immobilization method. Both chitosan and chitosan-immobilized sodium silicate were shown to selectively adsorb As(V), arsenate, from waters at pH 3.0 at which neither chitin nor sodium silicate displayed any sorption towards As(V). The sorption of arsenate by chitosan is supposed to have electrostatic nature since pH of 3.0 is both the point at which the amino groups in chitosan are protonated and also the predominant form of As(V) is H₂AsO₄⁻. A pre-oxidation step is required if both As(III) and As(V) are to be determined. Desorption from the sorbents was realized with 1.0% (w/v) l-cysteine prepared in a pH 3.0 solution adjusted with HCl. Among the possible interfering species tested, only Te(IV) and Sb(III) were shown to cause a decrease in the sorption capacity especially at high interferant concentrations. High concentrations of Sb(III) also resulted in gas phase interference during hydride generation.The validity of the method was checked both via spike recovery experiments and also through the analysis of a standard reference material. Spike recovery tests were carried out with four different types of water; namely, ultra-pure, bottled drinking, tap, and sea water; and percent recovery values were found to be 114 (±4), 112 (±2), 43 (±4), and 0 (±1), respectively. It was concluded that the proposed methodology can be applied efficiently to low-to-medium ionic strength solutions, such as most drinking waters. The accuracy of the method was additionally investigated through the analysis of a standard reference material and a good correlation was found between the determined (26.6 ± 2.4 μg L⁻¹) and the certified (26.67 μg L⁻¹) value.     

A novel cloud point extraction approach using cationic surfactant for the separation and pre-concentration of chromium species in natural water prior to ICP-DRC-MS determination

A novel cloud point phase separation of cationic surfactant, Aliquat-336 and capabilities of its reactive solubilizing sites for selective extraction of chromium species at ultra trace levels was examined in natural water. The phase separation behavior of Aliquat-336 is studied with various additives. The nonionic surfactant, Triton X-114 was found to induce the cloud point phase separation of Aliquat-336. The separation of anionic Cr(VI) was enabled by the formation of ion associate with quaternary ammonium head group of Aliquat-336 at pH 2, and the recovery of Cr(VI) and Cr(III) were 101.4 ± 1.4% and 2.2 ± 0.4%, respectively at 0.5-1 ng mL⁻¹, Total Cr was pre-concentrated as Cr-APDC species using the hydrophobic tail group at pH 6.5. The Cr(III) concentration was obtained by subtracting Cr(VI) from total Cr. The recovery of total Cr was 99.5 ± 1.2%. Parameters affecting extraction were assessed. The procedure was applied to NIST 1643c and NIST 1643d waters, and the sum of individual species obtained was compared with the certified chromium values. The method was also applied to various natural waters with limits of detection and pre-concentration factor of 0.010 and 0.025 ng mL⁻¹; 10 and 10, respectively, for Cr(VI) and Cr(III)-APDC using ICP-MS operated in DRC mode.     

Use of ion mobility spectroscopy with an ultraviolet ionization source as a vanguard screening system for the detection and determination of acetone in urine as a biomarker for cow and human diseases

An ion mobility spectrometer equipped with an ultraviolet lamp was used for the qualitative and quantitative determination of acetone in urine samples. This analyte can be used as a biomarker for some fat metabolism-related diseases in humans and cows. Samples require no pretreatment other than warming at 80 °C for 5 min, after which an N₂ stream is used to drive volatile analytes to the ion mobility spectrometer. The precision of the ensuing method, expressed as relative standard deviation (%RSD), is better in all cases than 6.7% for peak height and calculated at three levels of concentration. The analyte concentration range studied was from 5 to 80 mg L⁻¹, its limit of detection in the aqueous matrix 3 mg L⁻¹ and recoveries from spiked urine samples 109 ± 3%. The calculated reduced mobility for acetone in the urine samples, 1.75 ± 0.04 cm² V⁻¹ s⁻¹, was similar to previously reported values. Also, the results were consistent with those provided by test strips used for reference. The proposed method provides a new vanguard screening system for determining acetone in urine samples.     

Determination of nateglinide in human plasma by high-performance liquid chromatography with pre-column derivatization using a coumarin-type fluorescent reagent

A sensitive and selective high-performance liquid chromatographic method has been developed and validated for the determination of nateglinide in human plasma. Nateglinide and the internal standard, undecylenic acid, were extracted from plasma by liquid-liquid extraction using a mixture of ethyl acetate-diethyl ether, 50:50 (v/v). Pre-column derivatization reaction was performed using a coumarin-type fluorescent reagent, N-(7-methoxy-4-methyl-2-oxo-2H-6-chromenyl)-2-bromoacetamide. The derivatization proceeded in acetone in the presence of potassium carbonate and catalyzed by 18-crown-6 ether. The fluorescent derivatives were separated under isocratic conditions on a Hypersil BDS-C8 analytical column (250.0 mm × 2.1 mm i.d., particle size 5 μm) with a mobile phase that consisted of 65% acetonitrile in water and pumped at a flow rate of 0.50 mL min⁻¹. The excitation and emission wavelengths were set at 345 and 435 nm, respectively. The assay was linear over a concentration range of 0.05-16.00 μg mL⁻¹ for nateglinide with a limit of quantitation of 0.05 μg mL⁻¹. Quality control samples (0.05, 4.50 and 16.00 μg mL⁻¹) in five replicates from five different runs of analysis demonstrated intra-assay precision (%coefficient of variation <6.8%), inter-assay precision (%coefficient of variation <1.6%) and an overall accuracy (%relative error) less than −3.4%. The method can be used to quantify nateglinide in human plasma covering a variety of pharmacokinetic or bioequivalence studies.     

Analysis of chloroacetanilide herbicides in water samples by solid-phase microextraction coupled with gas chromatography-mass spectrometry

A solid-phase microextraction (SPME) method has been developed for the determination of 3 chloroacetanilide herbicides in both fresh and seawater samples. The extracted sample was analyzed by gas chromatography with mass spectrometry detection (GC-MS), and parameters affecting SPME operation including fibre type, sample pH, sample temperature, mixing speed and extraction time have been evaluated and optimized. The amount of dissolved organic matter (DOM) and the salt content both affected SPME extraction efficiency, but the presence of other competitive extractants such as organochlorine pesticides (OCPs) in the matrix showed no insignificance interference. The limit of detection (LOD) for acetochlor, metolachlor and butachlor were 1.2, 1.6 and 2.7 ng L⁻¹, respectively. The recoveries for the herbicides ranged from 79 to 102%, and the linear dynamic range was from 10 to 1000 ng L⁻¹. The developed method has been used to monitor herbicides contaminations in coastal water samples collected around Laizhou bay and Jiaozhou bay in Shandong peninsula, China. The concentrations of acetochlor and metolachlor ranged from undetectable to 78.5 ng L⁻¹ and undetectable to 35.6 ng L⁻¹, respectively. Butachlor was not observed but in only one sample and the concentration is lower than the limit of quantification (LOQ). The concentrations of the three herbicides in this study are low compared to most of the other places reported.     

Determination of ethyl glucuronide in urine using reversed-phase HPLC and pulsed electrochemical detection (Part II)

A direct, versatile method for the determination of ethyl glucuronide (EtG), a biomarker of ethanol consumption, in urine has been developed using reversed-phase liquid chromatography with pulsed electrochemical detection (PED). EtG and methyl glucuronide (MetG), which serves as an internal standard, are readily separated using a mobile phase consisting of 1% acetic acid/acetonitrile (98/2, v/v). Post-column addition of NaOH allows for the detection of all glucuronides using PED at a gold working electrode. Upon optimization, EtG was found to have a limit of detection of 0.03 μg/mL (7 pmol; 50 μL injection volume) and repeatability at the limit of quantitation of 1.7%R.S.D. (relative standard deviation). Solid-phase extraction (SPE) using an aminopropyl phase was used to remove interferents in urine samples prior to their analysis. Compound recovery following SPE was approximately 50 ± 2%. The forensic utility of this method was further validated by the analysis of 29 post-mortem urine specimens, whose results agreed strongly with certified determinations.     

Quantitative analysis of poly- and perfluoroalkyl compounds in water matrices using high resolution mass spectrometry: Optimization for a laser diode thermal desorption method

An alternative analysis technique for the quantitation of 15 poly- and perfluoroalkyl substances (PFASs) in water matrices is reported. Analysis time between each sample was reduced to less than 20 s, all target molecules being analyzed in a single run with the use of laser diode thermal desorption atmospheric pressure chemical ionization (LDTD/APCI) coupled with high resolution accurate mass (HRMS) orbitrap mass spectrometry. LDTD optimal settings were investigated using either one-factor-at-a-time or experimental design methodologies, while orbitrap parameters were optimized simultaneously by means of a Box–Behnken design. Following selection of an adequate sample concentration and purification procedure based on solid-phase extraction and graphite clean-up, the method was validated in an influent wastewater matrix. Environmentally significant limits of detection were reported (0.3–4 ng L⁻¹ in wastewater and 0.03–0.2 ng L⁻¹ in surface water) and out of the 15 target analytes, 11 showed excellent accuracies (±20% of the target values) and recovery rates (75–125%). The method was successfully applied to a selection of environmental samples, including wastewater samples in 7 locations across Canada, as well as surface and tap water samples from the Montreal region, providing insights into the degree of PFAS contamination in this area.