Simultaneous determination of benzotriazole and benzothiazole derivatives in aqueous matrices by mixed-mode solid-phase extraction followed by liquid chromatography–tandem mass spectrometry

An improved selectivity method for the simultaneous determination of four benzotriazoles (benzotriazole, 4-methylbenzotriazole, 5-methylbenzotriazole, and 5,6-dimethyl-1H-benzotriazole) and six benzothiazoles (benzothiazole, 2-hydroxybenzothiazole, 2-benzothiazolamine, mercaptobenzothiazole, 2-methylbenzothiazole, and 2-methylthiobenzothiazole) in aqueous matrices has been developed. Under optimal conditions, analytes are concentrated using a MAX solid-phase extraction (SPE) cartridge, based on divinylbenzene-N-vinylpyrrolidone functionalized with quaternary amine groups, which allows reversed-phase interactions in combination with ionic exchange. Selected compounds are recovered with methanol–acetone 7:3 (v/v) whereas acidic interferences remained attached to the sorbent, and as determined by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), LOQs for surface, urban and industrial wastewater are in the range of 0.002–0.29 ng/mL. Figures of merit of the method revealed good precision (RSD% <12%), linearity (R ² > 0.99) and accuracy (%R = 80–100%) for surface waters and effluents allowing direct external standard quantification. For more complex samples, such as urban and industrial raw wastewater, either the standard addition method or pseudo-external standard calibration using matrix matched standards are recommended. Analysis of different real samples, surface, urban wastewater and, for the first time, metal industry wastewater, reflected concentrations up to 310 ng/mL. The methylbenzotriazole isomers ratio was also determined.     

Simultaneous determination of 15 steroidal oral contraceptives in water using solid-phase disk extraction followed by high performance liquid chromatography–tandem mass spectrometry

A rapid, accurate and sensitive method for simultaneous determination of 15 steroidal hormones including four estrogens (estrone, 17β-estradiol, 17α-ethynylestradiol, estriol) and eleven progestogens (17β-estradiol-3-benzoate, 19-norethindrone, gestodene, levonorgestrel, medroxyprogesterone, cyproterone acetate, megestrol-17-acetate, progesterone, norethindrone acetate, chlormadinone-17-acetate, and hydroxy progesterone caproate) in environmental waters was developed by coupling solid-phase disk extraction (SPDE) to ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) with electrospray ionization. Among three types of extraction tested (C₈ SPDE, C₁₈ SPDE and C₁₈ SPE), the most satisfactory result was achieved using C₁₈ SPDE for its satisfactory recovery (75.6 to 101.4%) and short extraction time (15 min for 1 L deionised water). The validity of this method was investigated and good analytical performance for all the analytes was obtained, including low limits of method detection (0.5–3.4 ng/L) and excellent linear dynamic range (1.0–50.0 ng/L). The method was applied to determine the steroidal hormones in 10 environmental waters including tap water, river water, lake water and waste water in Beijing. No progestogen was detected in all samples and estrone, estriol, 17α-ethynylestradiol were found in most samples at levels between 1.8 and 127.9 ng/L.     

Dispersive solid-phase extraction followed by liquid chromatography–tandem mass spectrometry for the multi-residue analysis of pesticides in raw bovine milk

A fast multi-residue method based on dispersive solid-phase extraction (DSPE) followed by liquid chromatography–tandem mass spectrometry was developed for the simultaneous determination of 44 pesticides in raw bovine milk. Raw bovine milk samples did not percolate through SPE cartridges usually applied for pesticide extraction from homogenized pasteurized milk samples. Therefore, a DSPE technique was implemented and validated for the first time in this work. Graphitized non-porous carbon and C18 modified silica materials were tested both in combination with magnesium sulfate and bonded silica with ethylenediamine-N-propyl phase. The efficiency of the DSPE process was studied at several concentration levels obtaining the higher recoveries with C18 material. The method performance was also assessed and the limits of quantification reached the ng g⁻¹ level, complying with the most recent maximum residue levels. The DSPE method was also shown to be suited to both the fatty and skimmed fractions issued from raw milk. Finally, the extraction method was successfully applied to the analysis of raw milk samples collected in 23 farms of dairy cattle from NW Spain (Galicia).     

Dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry for the rapid and sensitive determination of UV filters in environmental water samples

The performance of the dispersive liquid–liquid microextraction (DLLME) technique for the determination of eight UV filters and a structurally related personal care species, benzyl salicylate (BzS), in environmental water samples is evaluated. After extraction, analytes were determined by gas chromatography combined with mass spectrometry detection (GC-MS). Parameters potentially affecting the performance of the sample preparation method (sample pH, ionic strength, type and volume of dispersant and extractant solvents) were systematically investigated using both multi- and univariant optimization strategies. Under final working conditions, analytes were extracted from 10 mL water samples by addition of 1 mL of acetone (dispersant) containing 60 μL of chlorobenzene (extractant), without modifying either the pH or the ionic strength of the sample. Limits of quantification (LOQs) between 2 and 14 ng L⁻¹, inter-day variability (evaluated with relative standard deviations, RSDs) from 9% to 14% and good linearity up to concentrations of 10,000 ng L⁻¹ were obtained. Moreover, the efficiency of the extraction was scarcely affected by the type of water sample. With the only exception of 2-ethylhexyl-p-dimethylaminobenzoate (EHPABA), compounds were found in environmental water samples at concentrations between 6 ± 1 ng L⁻¹ and 26 ± 2 ng mL⁻¹.     

Molecularly imprinted polymers for simultaneous determination of antiepileptics in river water samples by liquid chromatography–tandem mass spectrometry

A restricted access media–molecularly imprinted polymer (RAM–MIP) for cyclobarbital has been developed for selective extraction of antiepileptics in river water samples. The RAM–MIP was prepared using 4-vinylpyridine and ethylene glycol dimethacrylate as a functional monomer and cross-linker, respectively, by a multi-step swelling and polymerization method followed by a surface modification technique. The RAM–MIP for cyclobarbital showed molecular recognition abilities for phenobarbital, amobarbital and phenytoin as well as cyclobarbital. Thus, selective analysis of antiepileptics in river water samples was attained with RAM–MIP extraction followed by column-switching liquid chromatography–tandem mass spectrometry. The concentrations of phenobarbital and phenytoin in river water samples were about 15 and 4 ng/L, respectively, while that of amobarbital was below the limit of quantitation.     

Using bamboo charcoal as solid-phase extraction adsorbent for the ultratrace-level determination of perfluorooctanoic acid in water samples by high-performance liquid chromatography–mass spectrometry

In recent years, bamboo charcoal, a new kind of material with special microporous and biological characteristics, has attracted great attention in many application fields. In this paper, the potential of bamboo charcoal to act as a solid-phase extraction (SPE) adsorbent for the enrichment of the environmental pollutant perfluorooctanoic acid, which is one of the newest types of persistent organic pollutants in the environment, has been investigated. Important factors that may influence the enrichment efficiency—such as the eluent and its volume, the flow rate of the sample, the pH of the sample and the sample volume—were investigated and optimized in detail. Under the optimum conditions, the limit of detection for PFOA was 0.2 ng L⁻¹. The experimental results indicated that this approach gives good linearity (R ² = 0.9995) over the range 1–1000 ng L⁻¹ and good reproducibility, with a relative standard deviation of 4.0% (n = 5). The proposed method has been applied to the analysis of real water samples, and satisfactory results were obtained. The average spiked recoveries were in the range 79.5∼118.3 %. All of the results indicate that the proposed method could be used for the determination of PFOA at ultratrace levels in water samples.     

Monolithic molecularly imprinted solid-phase extraction for the selective determination of trace cytokinins in plant samples with liquid chromatography–electrospray tandem mass spectrometry

Cytokinins (CTKs) are a class of growth-regulating hormones involved in various physiological and developmental processes. More novel analytical methods for the accurate identification and quantitative determination of trace CTKs in plants have been desired to better elucidate the roles of CTKs. In this work, a novel method based on monolithic molecularly imprinted solid-phase extraction followed by liquid chromatography–electrospray tandem mass spectrometry (mMI-SPE-LC-MS/MS) was developed for accurate determination of four CTKs in plant samples. The molecularly imprinted polymer monolith was prepared by using kinetin as the template in syringes and exhibited specific recognition ability for the four CTKs in comparison with that of non-imprinted polymer monolith. Several factors affecting the extraction performance of mMI-SPE, including the pH of loading sample solution, the nature and volume of elution solvent, the flow rate of sample loading, and sample volume, were investigated, respectively. Under the optimized conditions, the proposed mMI-SPE-LC-MS/MS method was successfully applied in the selective extraction and determination of four CTKs in plant tissues, and it offers detection limits (S/N?=?3) of 104, 113, 130, and 89 pg/mL and mean recoveries of 85.9%, 79.3%, 73.5%, and 70.1% for kinetin, kinetin glucoside, trans-zeatin, and meta-topolin (mT), respectively, with the corresponding RSDs less than 15%.

Ultra-preconcentration and determination of thirteen organophosphorus pesticides in water samples using solid-phase extraction followed by dispersive liquid–liquid microextraction and gas chromatography with flame photometric detection

An ultra-preconcentration technique composed of solid-phase extraction (SPE) and dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–flame photometric detection (GC–FPD) was used for determination of thirteen organophosphorus pesticides (OPPs) including phorate, diazinon, disolfotane, methyl parathion, sumithion, chlorpyrifos, malathion, fenthion, profenphose, ethion, phosalone, azinphose-methyl and co-ral in aqueous samples. The analytes were collected from large volumes of aqueous solutions (100 mL) into 100 mg of a SPE C₁₈ sorbent. The effective variables of SPE including type and volume of elution solvent, volume and flow rate of sample solution, and salt concentration were investigated and optimized. Acetone was selected as eluent in SPE and disperser solvent in DLLME and chlorobenzene was used as extraction solvent. Under the optimal conditions, the enrichment factors were between 15,160 and 21,000 and extraction recoveries were 75.8–105.0%. The linear range was 1–10,000 ng L^?1 and limits of detection (LODs) were between 0.2 and 1.5 ng L^?1. The relative standard deviations (RSDs) for 50 ng L^?1 of OPPs in water with and without an internal standard, were in the range of 1.4–7.9% (n = 5) and 4.0–11.6%, respectively. The relative recoveries of OPPs from well and farm water sat spiking levels of 25 and 250 ng L^?1 were 88–109%.     

Optimization of antibiotic analysis in water by solid-phase extraction and high performance liquid chromatography–mass spectrometry/mass spectrometry

This paper describes the development of an optimized method based on solid-phase extraction (SPE) followed by liquid chromatography–electrospray ionization tandem mass spectrometry (LC–MS/MS) for the simultaneous analysis of ten antibiotic compounds including tetracyclines, sulfonamides, macrolides and quinolones. LC–MS/MS sensitivity has been optimized by alterations to both LC and MS operations. Of the two high resolution columns tested, Waters Symmetry C₁₈ endcapped and Agilent Zorbax Bonus-RP, the latter was found to show better performance in producing sharp peaks and clear separation for most of the target compounds. Optimization of the MS fragmentation collision and cone energy enhanced the peak areas of the target analytes. The recovery of the target compounds from water samples was most efficient on Waters Oasis HLB SPE cartridge, while methanol was shown to be the most suitable solvent for desorbing the compounds from SPE. In addition, acidification of samples prior to SPE was shown to enhance the recovery of the compounds. To ensure a satisfactory recovery, the flow rate through SPE should be maintained at ≤10 mL min⁻¹. The method was successfully applied to the analysis of antibiotics from environmental water samples, with concentrations being <LOD in tap water, between <LOD to 28 ng L⁻¹ in river water and between <LOD to 230 ng L⁻¹ in sewage effluent.     

Study of the metabolism on tobacco-specific N-nitrosamines in the rabbit by solid-phase extraction and liquid chromatography–tandem mass spectrometry

Metabolism of four tobacco-specific N-nitrosamines (TSNAs), N′-nitrosonornicotine (NNN), N′-nitrosoanatabine (NAT), N′-nitrosoanabasine (NAB), and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) has been studied by solid-phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS–MS). 4-(Methylnitrosamino)-4-(3-pyridyl)-1-butanol (iso-NNAL) was used as internal standard. SPE and LC–MS–MS was found to be a rapid, simple, sensitive, and selective method for analysis of TSNAs in rabbit serum. The relative standard deviation (R.S.D., n = 6) for analysis of 5 ng mL⁻¹ and 0.5 ng mL⁻¹ standards and of serum sample spiked with 5 ng mL⁻¹ standards of five TSNAs was 2.1–11% and recovery of 5 ng mL⁻¹ standards from serum was 100.2–112.9%. A good linear relationship was obtained between peak area ratio and concentration in the range of 0.2–100 ng mL⁻¹ for NNAL and 0.5–100 ng mL⁻¹ for other four TSNAs, with correlation coefficients (R ²) >0.99 (both linear and log–log regression). Detection limits for standards in solvent were between 0.04 and 0.10 ng mL⁻¹. Doses of TSNAs administered to rabbits via the auricular vein were 4.67 μg kg⁻¹ and 11.67 μg kg⁻¹, in accordance with the different levels in cigarettes. Metabolic curves were obtained for the four TSNAs and for 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), a metabolite of NNK; on the basis of these curves we modeled metabolic kinetic equations for these TSNAs by nonlinear curve fitting.     

Pre-concentration of phenolic compounds in water samples by novel liquid–liquid microextraction and determination by gas chromatography–mass spectrometry

Pre-concentration and determination of 8 phenolic compounds in water samples has been achieved by in situ derivatization and using a new liquid–liquid microextraction coupled GC–MS system. Microextraction efficiency factors have been investigated and optimized: 9 μL 1-undecanol microdrop exposed for 15 min floated on surface of a 10 mL water sample at 55 °C, stirred at 1200 rpm, low pH level and saturated salt conditions. Chromatographic problems associated with free phenols have been overcome by simultaneous in situ derivatization utilizing 40 μL of acetic anhydride and 0.5% (w/v) K₂CO₃. Under the selected conditions, pre-concentration factor of 235–1174, limit of detection of 0.005–0.68 μg/L (S/N = 3) and linearity range of 0.02–300 μg/L have been obtained. A reasonable repeatability (RSD ≤ 10.4%, n = 5) with satisfactory linearity (0.9995 ≥ r² ≥ 0.9975) of results illustrated a good performance of the present method. The relative recovery of different natural water samples was higher than 84%.     

Identification of dissolved organic species in non-drinking tap water by solid-phase extraction and gas chromatography–mass spectrometry

A method is presented for qualitative identification of dissolved volatile organic compounds (VOCs) in non-drinking tap water samples based on applications of both solid-phase extraction (SPE) and gas chromatography–mass spectrometric (GC–MS) techniques. Water samples were collected and passed over a micro-column packed with acid treated active silica gel phase (pH = 2.6) for adsorption of dissolved organic species under this pH-condition. Silica-bound-organics were then divided into equal portions followed by suspension into organic solvents of different polarities such as methanol, ethanol, butan-1-ol, ethyl acetate, diethyl ether and chloroform. These suspensions were then automatically shaken for 1 h at room temperature. The organic extracts were subjected to GC–MS analysis under temperature programming conditions. The mass spectrum of each eluted chromatographic peak was library searched or manually interpreted to identify the correct name and structure. Blank solvent and silica samples were also subjected to the same GC–MS analysis for comparison.     

Quantitative determination of 22 primary aromatic amines by cation-exchange solid-phase extraction and liquid chromatography–mass spectrometry

Primary aromatic amines (PAAs) have been broadly studied due to their high toxicity. In this work a method for the analysis of 22 PAAs in aqueous simulants has been developed. The method is based on a solid-phase extraction step using cation-exchange cartridges and the subsequent analysis of the extracts by ultra-high-performance liquid chromatography with mass spectrometric detection. The recoveries obtained for all the amines analyzed ranged between 81 and 109%, linear range was between 0.03 and 75 μg L⁻¹, with the RSD values between 4.5 and 13.4% and an average value of 7.5% and limits of detection at μg L⁻¹ level. The method has been applied to two real samples obtained from migration experiments of polyurethane based laminates to simulant B (water with 3% (w/v) acetic acid) which represents the worst case for the migration of aromatic amines. The main amines found in both samples were methylenedianiline isomers, obtained from the corresponding residual diisocyanates used during polyurethane adhesive polymerization. The total amine concentration found was 26 and 6.3 μg of aniline equivalents per kg of food simulant.     

Stir-bar-sorptive extraction and ultra-high-performance liquid chromatography–tandem mass spectrometry for simultaneous analysis of UV filters and antimicrobial agents in water samples

Stir-bar-sorptive extraction (SBSE) with liquid desorption (LD) and ultra-high-performance liquid chromatography–electrospray ionization triple-quadrupole tandem mass spectrometry (UHPLC–(ESI)MS–MS) were used for analysis of six personal care products in environmental water: four UV filters (2,2-dihydroxy-4-methoxybenzophenone, benzophenone-3, octocrylene, and octyldimethyl-p-aminobenzoic acid) and two antimicrobial agents (triclocarban and triclosan). Experimental conditions that affect SBSE-LD sorption efficiency (extraction time and temperature, sample pH, and ionic strength) and desorption efficiency (solvent, temperature, and time) were optimized. The method proved to be sensitive—a 50-mL sample was used to determine these compounds in environmental waters at trace levels. The detection limits of the analytical method were 2.5 ng L⁻¹ for river water and 5–10 ng L⁻¹ for effluent and influent sewage water. In river waters, benzophenone-3 was found at levels from 6 ng L⁻¹ to 28 ng L⁻¹ and triclosan at levels <LOQ. Benzophenone-3 was found between 75 and 127 ng L⁻¹ in influent sewage, whereas concentrations of benzophenone-3 and triclosan were commonly below 25 ng L⁻¹ in effluent sewage.     

Microwave-assisted extraction combined with gel permeation chromatography and silica gel cleanup followed by gas chromatography–mass spectrometry for the determination of organophosphorus flame retardants and plasticizers in biological samples

An analytical method for the determination of 14 organophosphorus flame retardants (OPFRs), including halogenated OPFRs, non-halogenated OPFRs and triphenyl phosphine oxide (TPPO) in biological samples was developed using gas chromatography–mass spectrometry (GC/MS). Biological samples were extracted using microwave-assisted extraction (MAE) with hexane/acetone (1:1, v/v) as the solvent; then, a two-step clean-up technique, gel permeation chromatography (GPC) combined with solid phase extraction (SPE), was carried out before GC/MS analysis. Experimental results showed that the developed method efficiently removed the lipid compounds and co-extract interferences. Moreover, using the relatively “narrow” column (with an i.d. of 10 mm) significantly decreased the elution volume and, therefore, prevented the loss of the most volatile OPFRs, especially trimethyl phosphate (TMP) and triethyl phosphate (TEP). The method detection limits (MDLs) for OPFRs in the biological samples ranged from 0.006 to 0.021 ng g⁻¹ lw, and the recoveries were in the range of 70.3–111%, except for TMP (38.9–55.6%), with relative standard deviations (RSDs) of less than 14.1%. The developed method was applied to determine the amount of the target OPFRs in biological samples (i.e., fish and domestic birds) that were collected from the Pearl River Delta (PRD) region in southern China. Of the 14 OPFRs, tri-n-butyl phosphate (TnBP), tris(2-chloroethyl) phosphate (TCEP), tris(chloropropyl) phosphate (TCPP) and tributoxyethyl phosphate (TBEP) were present in all of the biological samples that were analyzed, and dominated by TnBP, TCEP and TBEP. The concentrations of OPFRs in the biological samples that were collected from the PRD region were higher than those reported in other locations.     

Quantification of atrazine and its metabolites in urine by on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry

We have developed a method using on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry (SPE-HPLC-MS/MS) and isotope dilution quantification to measure atrazine and seven atrazine metabolites in urine. The metabolites measured were hydroxyatrazine, diaminochloroatrazine, desisopropylatrazine, desethylatrazine, desethylatrazine mercapturate, atrazine mercaturate and atrazine itself. Our method has good precision (relative standard deviations ranging from 4 to 20% at 5, 10 and 50 ng/mL), extraction efficiencies of 67 to 102% at 5 and 25 ng/mL, relative recoveries of 87 to 112% at 5, 25, 50 and 100 ng/mL limits of detection (LOD) ranging from 0.03 to 2.80 ng/mL. The linear range of our method spans from the analyte LOD to 100 ng/mL (40 ng/mL for atrazine and atrazine mercapturate) with R ² values of greater than 0.999 and errors about the slope of less than 3%. Our method is rapid, cost-effective and suitable for large-scale sample analyses and is easily adaptable to other biological matrices. More importantly, this method will allow us to better assess human exposure to atrazine-related chemicals. Figure A schematic representation showing the elution of the analytes from the solid-phase extraction cartridge onto the analytical column for chromatographic separation prior to MS/MS analysis     

The determination of pharmaceutical residues in cooked and uncooked marine bivalves using pressurised liquid extraction, solid-phase extraction and liquid chromatography–tandem mass spectrometry

An optimised and validated method for the determination of pharmaceutical residues in blue mussels (Mytilus spp.) is presented herein, as well as an investigation of the effect of cooking (by steaming) on any potential difference in human exposure risk. Selected pharmaceuticals included two non-steroidal anti-inflammatory drugs (diclofenac and mefenamic acid), an antibiotic (trimethoprim), an anti-epileptic (carbamazepine) and a lipid regulator (gemfibrozil). An in vivo exposure experiment was set up in the laboratory in which mussels were exposed either directly by injection (10 ng) or daily through spiked artificial seawater (ASW) over 96 h. In liquid matrices, pharmaceutical residues were either determined using liquid chromatography–tandem mass spectrometry (LC-MS/MS) directly, or in combination with solid-phase extraction (SPE) for analyte concentration purposes. The extraction of pharmaceuticals from mussel tissues used an additional pressurised liquid extraction step prior to SPE and LC-MS/MS. Limits of quantification of between 2 and 46 ng L^?1 were achieved for extracted cooking water and ASW, between 2 and 64 μg L^?1 for ASW in exposure tanks, and between 4 and 29 ng g^?1 for mussel tissue. Method linearities were achieved for pharmaceuticals in each matrix with correlation coefficients of R ²?>?0.975. A selection of exposed mussels was also cooked (via steaming) and analysed using the optimised method to observe any effect on detectable concentrations of parent pharmaceuticals present. An overall increase in pharmaceutical residues in the contaminated mussel tissue and cooking water was observed after cooking.

Ultra-high-pressure liquid chromatography–tandem mass spectrometry method for the determination of alkylphenols in soil

A novel method has been developed for the determination of alkylphenols in soil by ultra-high-pressure liquid chromatography employing small particle sizes, combined with tandem mass spectrometry. Soil samples were extracted with pressurized liquid extraction (PLE) and then cleaned with solid-phase extraction (SPE). The extracts were separated on C18 column (1.7 μm, 50 mm × 2.1 mm) with a gradient elution and a mobile phase consisting of water and acetonitrile, and then detected by an electrospray ionization tandem mass spectrometry in negative ion mode with multiple reaction monitoring (MRM). Compared with traditional liquid chromatography, it took ultra-high-pressure liquid chromatography much less time to analyze alkylphenols. Additionally, the ultra-high-pressure liquid chromatography/tandem mass spectrometry method produces satisfactory reliability, sensitivity, and accuracy. The average recoveries of the three target analytes were 74.0–103.4%, with the RSD < 15%. The calibration curves for alkylphenols were linear within the range of 0.01–0.4 μg/ml, with the correlation coefficients greater than 0.99. When 10 g soil sample was used for analysis, the limits of quantification (LOQs) of the three alkylphenols were all 1.0 μg/kg.