Strata-X Cartridges Research Articles

Residues of veterinary antibiotics in solid natural and organic fertilizers-method development and sample analysis.

Livestock excrement is used around the world as natural fertilizers or, after processing, as organic fertilizers for crops and grasslands. But due to the presence of veterinary antibiotics in them, they may pose a threat not only to the natural environment, mainly to soil microorganisms, but also to human and animal health. This article describes a method for detecting 21 antibacterial substances in solid natural and organic fertilizers. Antibiotics from fertilizers were extracted with a mixture of acetonitrile and McIlvain-Na2EDTA buffer, twice. The extracts were purified by solid phase extraction technique on Strata-X cartridges and analyzed with the use UHPLC-MS/MS technique. The method was validated in accordance with EU Commission Implementing Regulation 2021/808; the obtained recovery ranged from 93.6 to 116.6% (depending on the analytes), and the linearity ranged from 50 to 1000µg/kg. The developed method was used to analyze 73 samples of solid natural and organic fertilizers. Our research has shown that over 38% of natural fertilizers were contaminated with antibiotics, mainly doxycycline in concentrations reaching several dozen milligrams per kilogram of fertilizers. In the case of processed organic fertilizers, the presence of antibiotics was found in over 37% of the analyzed samples. The research results showed that the developed and validated analytical method may be useful for assessing the presence and content of antibacterial substances in solid natural and organic fertilizers.

Investigating the etiology of Haff disease: Optimization and validation of a sensitive LC-MS/MS method for palytoxins analysis in directly associated freshwater and marine food samples from Brazil

Haff disease typically develops after eating contaminated marine or freshwater species, especially fish. Despite still having an unknown etiology, recent reports have suggested its possible correlation with palytoxins. Therefore, the present work aimed to optimize and perform a validation of a sensitive method using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) for the analysis of palytoxin and some of its analogs, with the main purpose of investigating their presence in marine and freshwater food samples associated with Haff disease in Brazil. The method optimization was performed using a central composite rotatable design and fish samples fortified with the palytoxin standard. Then, the optimized method was validated for different food matrices, including freshwater and marine fish, mollusks, and crustaceans. The sample preparation involved a solid–liquid extraction using methanol and water, solid-phase extraction using Strata-X cartridges, and on-column palytoxin oxidation. The detection of the main oxidized fragments (amino and amide aldehydes) was achieved by LC-MS/MS with electrospray ionization in positive mode, using a C18 column, as well as acetonitrile and water as mobile phases, both acidified with 0.1 % of formic acid. After optimization and validation, the etiological investigation involved the analysis of 16 Brazilian Haff disease-related food samples (in natura and leftover meals) from 2022. The method was demonstrated to be appropriate for quantitative analysis of freshwater and marine species. So far, it has proven to be one of the most sensitive methods related to palytoxin detection (LOD 10 μg/kg), being able to work in a range that includes the provisional ingestion limit (30 μg/kg). Regarding the Haff disease-related samples analysis, there is a strong indication of palytoxin contamination since the amino aldehyde (common fragment for all palytoxins) was detected in 15 of the 16 samples. Selected results were confirmed using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS).

Does sildenafil citrate affect the pharmacokinetics of metformin in rats? Screening of mechanism through analytical and molecular docking approach.

In the present study, the effect of sildenafil on the pharmacokinetics of metformin was studied in experimental rats, and we also postulated the molecular mechanism by performing molecular docking studies. Analysis of metformin and sildenafil (SIL) from rat plasma was done by high performance liquid chromatography. Optimum chromatographic separation and quantification of MET, SIL and Cetirizine was achieved on Phenomenex EVO C18 column with triethyl amine (0.3%): Methanol: Acetonitrile (70:05:25 v/v) as mobile phase maintaining flow rate of 1 ml/min, the detector was tuned at 224 nm. The extraction of MET and sildenafil from rat plasma was achieved by solid-phase extraction using Strata-X cartridges. The method was validated as per the ICH guidelines. For docking studies, the crystal structure of organic cation transporter 1 (OCT1) protein and multidrug and toxin extrusion (MATE) protein (5XJJ) were downloaded from the PubChem database. The docking study was performed by PyRx virtual screening software, and the results were analyzed by BIOVIA Discovery Studio. The validation of HPLC method was done, intraday and interday precision study of HPLC method demonstrated %RSD values less than 5%, the extraction recovery for MET and SIL were near to 80 % for low, medium and high QC samples. The plasma stability of MET and SIL showed % RSD values <10% for low, medium, and high QC samples. A sensitivity study for MET and SIL in rat plasma suggested a lower limit of quantification values of 8 and 10 ng/mL, respectively. The pharmacokinetic parameters were recorded, Cmax of experimental and control rats was 611.2 and 913.2 ng/mL; t1/2 1.66 and 1.98, AUC (0-t) 1637.5 and 2727.24, AUC (0-∞) 1832.38 and 2995.24 for MET. The results suggested that the Cmax of MET in experimental rats (MET + SIL) was 33.07% lower than the control (MET only) and also the t1/2 was 0.32 h shorter. Docking analysis suggested a higher binding affinity of sildenafil with MATE protein (5XJJ) compared to OCT1, suggesting possible involvement of MATE family proteins for pharmacokinetic alterations of MET. The HPLC and solid-phase extraction method were developed and applied successfully for the pharmacokinetics of MET and SIL. Intake of SIL altered the pharmacokinetics of MET in rats. Molecular docking studies suggested the involvement of MATE family proteins for alterations of MET pharmacokinetics.

Selective solid phase extraction of phototoxic furanocoumarins using molecularly imprinted polymers

Furanocoumarins are secondary plant metabolites found in citrus plants. Essential oils from these plants are widely used in cosmetic products. They have attracted attention for their phototoxicity, which can even lead to skin burns. Therefore, the furanocoumarin concentration is controlled by the European Union according to Regulation (EC) No. 1223/2009, where a limit of 1 mg kg−1 is specified in sun protection and bronzing agents. This study describes the synthesis of two molecularly imprinted polymers (methacrylamide and methacrylic acid as monomers) as novel materials for solid phase extraction. After optimisation of the extraction protocol, both polymers gave satisfying recovery results for a furanocoumarin standard mixture containing the six markers proposed by the International Fragrance Association (IFRA). Furthermore, spiked sun oil samples were extracted using an adapted extraction protocol. Since the studies showed promising results including 75–149 % recovery and 100 % loading efficiency for the methacrylic acid polymer, a validation of the analytical method was performed. Analysis was performed using HPLC-MS/MS in high specificity multi-reaction monitoring mode. The validation showed acceptable results for most parameters. In addition, a comparison with commercially available Strata-X cartridges was completed, revealing superior recovery performance of the molecularly imprinted polymer. In conclusion, molecularly imprinted polymers represent a novel and efficient method for selective solid-phase extraction of phototoxic furanocoumarins.

Quantification of quaternary ammonium compounds by liquid chromatography-mass spectrometry: Minimizing losses from the field to the laboratory

Quaternary Ammonium Compounds (QACs) are widely used in household, medical and industrial settings. As a consequence, they are ubiquitously found in the environment. Although significant efforts have been put into the development of sensitive and reproducible analytical methods, much less effort has been dedicated to the monitoring of QACs upon sample storage and sample preparation. Here we studied the effect of storage, concentration, and extraction procedures on the concentrations of QACs in samples. Thirteen QACs selected amongst benzalkonium compounds (BACs), dialkyldimethylammonium compounds (DADMACs) and alkyltrimethylammonium compounds (ATMACs) were quantified in aqueous and solid samples using LC-MS/MS. Most QACs adsorbed on container walls could be recovered using a short washing step with MeOH containing 2 % v/v formic acid. Concentrations of QACs from aqueous solutions using solid phase extraction (SPE) with Strata-X cartridges and elution with acidified MeOH utilized to wash the emptied containers gave highly satisfactory recoveries (101–111 %). Good recoveries (89–116 %) were also obtained when extracting a spiked organic-rich synthetic soil using accelerated solvent extraction (ASE) with acidified MeOH at low solid/solvent ratio (0.4 g/20 mL). Applying the recommended methodologies to real samples collected from a Canadian wastewater treatment plant (WWTP) gave QAC concentrations in the ranges of 0.01–30 µg/L, < 1.2 µg/L, and 0.05–27 mg/kg for the influent, effluent and biosolids samples, respectively.

Multiclass cyanotoxin analysis in reservoir waters: Tandem solid-phase extraction followed by zwitterionic hydrophilic interaction liquid chromatography-mass spectrometry

The presence of cyanobacteria and cyanotoxins in all water bodies, including ocean water and fresh water sources, represents a risk for human health as eutrophication and climate change are enhancing their level of proliferation. For risk assessment and studies on occurrence, the development of reliable and sensitive analytical approaches able to cover a wide range of cyanotoxins is essential. This work describes the development of an HILIC-MS/MS multiclass method for the simultaneous analysis of eight cyanotoxins in reservoir water samples belonging to three different classes according to their chemical structure: cyclic peptides (microcystin-LR, microcystin-RR and nodularin), alkaloids (cylindrospermopsin, anatoxin-a) and three non-protein amino acids isomers such as β-methylamino-L-alanine, 2,4-diaminobutyric acid and N-(2-aminoethyl)glycine). A SeQuant ZIC-HILIC column was employed to achieve the chromatographic separation in less than 12 min. Previously, a novel sample treatment based on a tandem solid-phase extraction (SPE) system using mixed cation exchange (MCX) and Strata-X cartridges was investigated with the aim of extracting and preconcentrating this chemically diverse group of cyanotoxins. The Strata-X cartridge, which was configured first in the line of sample flow, retained the low polar compounds and the MCX cartridge, which was at the bottom of the dual system, retained mainly the non-protein amino acids. The optimization procedure highlighted the importance of sample ion content for the recoveries of some analytes such as the isomers β-N-methylamino-L-alanine and 2-4-diaminobutyric acid. Method validation was carried out in terms of linearity, limit of detection (LOD) and quantification (LOQ), recoveries, matrix effect and precision in terms of repeatability and intermediate precision. This work represents the first analytical method for the simultaneous analysis of these multiclass cyanotoxins in reservoir water samples, achieving LOQs in the very low range of 7·10−3 – 0.1 μg L−1. Despite high recoveries obtained at the LOQ concentration levels (101.0–70.9%), relative standard deviations lower than 17.5% were achieved.

An improved automated one-pot synthesis of O-(2-[18F]fluoroethyl)-L-tyrosine ([18F]FET) based on a purification by cartridges

IntroductionO-(2-[18F]Fluoroethyl)-L-tyrosine ([18F]FET) is an established radiotracer used for oncology investigations by Positron Emission Tomography (PET). Main limitations to its widespread use are the synthesis itself (time; cost; radiochemical yield; complexity) and a troublesome and time-consuming HPLC purification. Aim of this work was to improve the preparation overall efficiency and, most important, to achieve an efficient and reliable purification by means of disposable cartridges. Methods[18F]FET was synthesized by direct nucleophilic radiofluorination of O-(2-tosyloxy-ethyl)-N-trityl-L-tyrosine t-butylester (TET) followed by acid hydrolysis with HCl. Several conditions and materials were tested for the synthesis and purification step. For the latter, a number of different commercial cartridges, varying in amount, particulate size and adsorbent, were examined. Best results were obtained by a combination of STRATA-X, tC18 and QMA cartridges. ResultsStarting from only 5 mg of TET, up to 11 GBq of injectable solutions of [18F]FET were produced within 36 min with 54–65% radiochemical yields and radiochemical purities >99%. No D-form was observed by chiral HPLC. Chemical purity was 1–2 order of magnitude below the limits imposed by the European Pharmacopoeia's monograph on [18F]FET.A radiochemical purity decrease by radiolysis, observed only on relatively large batches of [18F]FET, was efficiently suppressed by preloading in the receiving final vial a small amount of ethanol (<2% v/v). ConclusionsBy combining improvements to a known synthetic route with a novel cartridge-based purification, [18F]FET was obtained in a very efficient and reproducible way. The whole process was easily implemented on a commercial automated module presently used for [18F]FDG production. Advances in knowledge and implications for patient careA few drawbacks regarding the HPLC conditions recommended in the European Pharmacopoeia were highlighted. An alternative method able to cope with them is herein proposedThe simplified preparation herein described is expected to encourage a more widespread clinical use of [18F]FET.

Analysis of ibuprofen and its main metabolites in roots, shoots, and seeds of cowpea (Vigna unguiculata L. Walp) using liquid chromatography-quadrupole time-of-flight mass spectrometry: uptake, metabolism, and translocation.

A liquid chromatography quadruple time-of-flight mass spectrometry (LC-QqTOF-MS/MS) method was developed for simultaneous quantitative analysis of ibuprofen (IBU), 1- and 2-hydroxyibuprofen (1-OH IBU and 2-OH IBU), and carboxyibuprofen (CBX IBU) while preserving the ability of the instrument to get precursor and product ion mass spectra of non-target compounds. The trigger was the precursor ions reaching 100cps intensity. Sample preparation was carried out by ultrasound solid-liquid extraction with methanol as extraction solvent at pH < 2 followed by solid-phase extraction (SPE) clean-up using STRATA-X cartridges and methanol as an eluent. Linearity was obtained in the range 50-10,000ngmL-1 for IBU, each OH IBU and CBX IBU (r ≥ 0.99). The proposed method was satisfactorily validated showing absolute recoveries of > 70% for all target analytes at low and high concentration levels. The lowest limit of quantification was < 50ngg-1 in plant. This method was applied to investigate IBP behavior in cowpea (Vigna unguiculata (L.) Walp) treated at high IBU concentrations and its presence in vegetables irrigated with treated water. Up to 46 metabolites, mostly hydroxylated metabolites and conjugates with hexosides and amino acids, were identified. The most abundant metabolites were also identified in an eggplant sample. Graphical Abstract ᅟ Ibuprofen metabolite identification.

An improved LC-MS/MS method for the quantification of alverine and para hydroxy alverine in human plasma for a bioequivalence study☆

A highly sensitive and selective high performance liquid chromatography-tandem mass spectrometry method was developed and validated for the quantification of alverine (ALV) and its active metabolite, para hydroxy alverine (PHA), in human plasma. For sample preparation, solid phase extraction of analytes was performed on Phenomenex Strata-X cartridges using alverine-d5 as the internal standard. The analytes were separated on Symmetry Shield RP18 (150mm×3.9mm, 5µm) column with a mobile phase consisting of acetonitrile and 10mM ammonium formate (65:35, v/v). Detection and quantitation was done by electrospray ionization mass spectrometry in the positive mode using multiple reaction monitoring. The assay method was fully validated over the concentration range of 15.0–15,000pg/mL for ALV and 30.0–15,000pg/mL for PHA. The intra-day and inter-day accuracy and precision (% CV) ranged from 94.00% to 96.00% and 0.48% to 4.15% for both the analytes. The mean recovery obtained for ALV and PHA was 80.59% and 81.26%, respectively. Matrix effect, expressed as IS-normalized matrix factor ranged from 0.982 to 1.009 for both the analytes. The application of the method was demonstrated for the specific analysis of ALV and PHA for a bioequivalence study in 52 healthy subjects using 120mg ALV capsules. The assay reproducibility was also verified by reanalysis of 175 incurred subject samples.

Determination of pharmaceutical residues in wastewater using high performance liquid chromatography coupled to quadrupole-Orbitrap mass spectrometry

A multi-class method for the determination of 24 emerging pharmaceutical residues has been developed and validated. The method is based on solid-phase extraction of wastewater samples using Strata-X cartridges followed by high performance liquid chromatography coupled to hybrid quadrupole − Orbitrap high resolution mass spectrometry (HPLC-Q-Orbitrap-HRMS). A single-laboratory validation procedure showed satisfactory analytical performance. The analysis of 21 samples collected at the wastewater treatment plant in Riga revealed the occurrence of 20 compounds of different therapeutic classes. The highest concentration was found for the central nervous system stimulator caffeine − up to 12μgL−1, the analgesic acetaminophen up to 4.2μgL−1, the antibiotic ciprofloxacin in the concentration range of 250–400ngL−1, and the non-steroidal anti-inflammatory drug (NSAID) ibuprofen at 100–325ngL−1.

LC–tandem mass spectrometry method for the simultaneous determination of metformin and sitagliptin in human plasma after ion-pair solid phase extraction

A reversed-phase liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) method was established for simultaneous determination of two oral hypoglycemic drugs metformin (MET) and sitagliptin (STG) in human plasma. The analytes were extracted from 50μL human plasma by ion-pair solid phase extraction using sodium lauryl sulphate on Phenomenex Strata-X (30mg/1mL) cartridges. The chromatographic separation was accomplished on XSelect HSS CN (150×4.6mm, 5μm) column using mobile phase consisting of methanol-8.0mM ammonium formate in water, pH 4.5 (80:20, v/v) under isocratic condition. Tandem MS detection was performed on a triple quadrupole spectrometer equipped with an electrospray ionization source, operated in the positive mode. Multiple reaction monitoring (MRM) was used to quantify the analytes following transitions, m/z 130.1→60.1 and m/z 408.3→235.1 for MET and STG respectively. The method displayed acceptable linearity in the concentration range of 4.00–3200ng/mL for MET and 1.00–800ng/mL for STG. The intra-batch and inter-batch precisions were ≤5.1% and accuracy ranged from 96.5 to 103.3% for both the drugs. The mean recovery of MET and STG obtained from spiked plasma samples was 82.5% and 90.4% respectively with minimal matrix interference. Both the drugs were found to be stable under all mandatory storage conditions. The validated method was successfully applied to a clinical pharmacokinetic study for a fixed-dose tablet formulation containing 500mg MET and 50mg STG in 16 healthy volunteers.

Quantitative Analysis of Bacitracin in Porcine Edible Tissues by High-Performance Liquid Chromatography–Electrospray Ionization Tandem Mass Spectrometry and Its Application to Residue Depletion Study

The residue kinetics of bacitracin in animals has rarely been quantitatively described due to inadequate sensitivity of analytical methods. A sensitive and selective quantitative liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) method was developed to determine the residue depletion kinetics of zinc bacitracin in pigs. The tissues samples were extracted with acidified methanol/water solution (v/v, 1:1, 1 % formic acid) and followed by liquid-liquid extraction with saturated solution of 0.1 mmol dithizone in chloroform. The extracts were subjected to Phenomenex Strata-X cartridges for further cleanup with 0.1 % formic acid in methanol. Analysis was performed on a C18 column with positive-ion electrospray mass spectrometry and multiple-reaction monitoring mode. The product ions at m/z 199 and 227 were selected for bacitracin A confirmation and at 199 for quantification. The developed method was linear in the concentration ranges of 150–4000 μg/L for bacitracin with limit of detection (LOD) and limit of quantification (LOQ) of 25 and 50 μg/kg for kidney and 20 and 50 μg/kg for skin with fat, liver, and muscle. The recoveries from different tissues were higher than 82.1 % at three different spiking levels with relative standard deviations (RSDs) less than 8.8 %. The residue depletion study showed that higher concentration and longer residue time were detected in kidney than in other three tissues. The elimination half-life in kidney was 0.45 days, and the recommended withdrawal period was zero. These results suggest that the established method satisfactorily enables a closer study of residue depletion kinetics of bacitracin in swine.

소변 중 다환방향족탄화수소 대사체의 분석법 확립 및 교차분석

Objectives: This study was performed to evaluate the analytical method for PAH metabolites in human urine using enzyme hydrolysis and solid-phase extraction coupled with LC-(ESI)-MS/MS technique. Methods: We employed HPLC tandem mass spectrometry techniques with appropriate pre-treatment for analysis of 16 OH-PAHs in human urine. Samples were hydrolysis by <TEX>${\beta}$</TEX>-flucuronidase/Aryl sulfatase, and target compounds were extracted by solid-phase extraction with a strata-x cartridge. Cross-validation was performed between Eulji University and Green Cross laboratories with 200 human urine samples. Results: The accuracies were between 90.3% and 118.8%, and precisions (relative standard deviations) were lower than 10%. The linearity obtained was satisfying for the 16 OH-PAH compounds, with a coefficient of determination (<TEX>$r^2$</TEX>) higher than 0.99. The results of cross-validation at the two organizations were compared by ICC (interclass correlation coefficient) values. The cross-validation results were excellent or good for all compounds. Conclusion: An analytical method was validated for low nanogram levels of 16 OH-PAHs in human urine. Also, satisfying results were obtained for method validation such as accuracy, precision and ICC of cross-validation.

Determination of lercanidipine in human plasma by an improved UPLC–MS/MS method for a bioequivalence study

An improved and reliable ultra-performance liquid chromatography/tandem mass spectrometry (UPLC–MS/MS) method has been developed and validated for the determination of lercanidipine in human plasma. Plasma samples with lercanidipine-d3 as an internal standard (IS) were prepared by solid phase extraction on Phenomenex Strata-X cartridges using 100µL of human plasma. Chromatographic analysis was performed on UPLC BEH C18 (50mm×2.1mm, 1.7µm) column under isocratic conditions. Linear calibration curves were obtained over a wide dynamic concentration range of 0.010–20.0ng/mL. Matrix effect was assessed by post-column infusion, post-extraction spiking and standard-line slope methods. The mean extraction recovery was >94% for the analyte and IS. Inter-batch and intra-batch precision (% CV) across five quality controls was <5.8%. Bioequivalence study was performed with 36 healthy subjects after oral administration of 10mg of lercanidipine and the assay reproducibility was evaluated by reanalysis of 133 incurred samples.

Simultaneous quantification of atenolol and chlorthalidone in human plasma by ultra-performance liquid chromatography-tandem mass spectrometry.

A simple, sensitive and reproducible ultra-performance liquid chromatography-tandem mass spectrometry method has been developed for the simultaneous determination of atenolol, a β-adrenergic receptor-blocker and chlorthalidone, a monosulfonamyl diuretic in human plasma, using atenolol-d7 and chlorthalidone-d4 as the internal standards (ISs). Following solid-phase extraction on Phenomenex Strata-X cartridges using 100 μL human plasma sample, the analytes and ISs were separated on an Acquity UPLC BEH C18 (50 mm × 2.1 mm, 1.7 µm) column using a mobile phase consisting of 0.1% formic acid-acetonitrile (25:75, v/v). A tandem mass spectrometer equipped with electrospray ionization was used as a detector in the positive ionization mode for both analytes. The linear concentration range was established as 0.50-500 ng/mL for atenolol and 0.25-150 ng/mL for chlorthalidone. Extraction recoveries were within 95-103% and ion suppression/enhancement, expressed as IS-normalized matrix factors, ranged from 0.95 to 1.06 for both the analytes. Intra-batch and inter-batch precision (CV) and accuracy values were 2.37-5.91 and 96.1-103.2%, respectively. Stability of analytes in plasma was evaluated under different conditions, such as bench-top, freeze-thaw, dry and wet extract and long-term. The developed method was superior to the existing methods for the simultaneous determination of atenolol and chlorthalidone in human plasma with respect to the sensitivity, chromatographic analysis time and plasma volume for processing. Further, it was successfully applied to support a bioequivalence study of 50 mg atenolol + 12.5 mg chlorthalidone in 28 healthy Indian subjects.

Simultaneous determination of traditional and emerging illicit drugs in sediments, sludges and particulate matter

An analytical method for determining traditional and emerging drugs of abuse in particulate matter, sewage sludge and sediment has been developed and validated. A total of 41 drugs of abuse and metabolites including cocainics, tryptamines, amphetamines, arylcyclohexylamines, cathinones, morphine derivatives, pyrrolidifenones derivatives, entactogens, piperazines and other psychostimulants were selected. Samples were ultrasound extracted with McIlvaine buffer and methanol, and the extracts were cleaned up by solid phase extraction (SPE) using Strata-X cartridges. Drugs were eluted using methanol and methanol–dichloromethane and determined by liquid chromatography tandem mass spectrometry. The optimum solid–liquid extraction (SLE) conditions were: weight 1g of sample and ultrasound assisted extraction (UAE) with 10mL of methanol–McIlvain buffer (1:1, v/v, pH 4.5) for 10min. Recoveries for all compounds were ≥50% in the three matrices with the exception of ephedrine (EPHE), 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), ecgonine methyester (ECME), heroin (HER), 3,4-methylendioxyamphetamine (MDA) and 4-acetoxy N,N′-dimethyltryptamine (4-AcO-DIPT) and methadone (MET). Data acquisition was done by selective reaction monitoring (SRM), and the two most abundant product ions were used for confirmation. Limits of detection were lower than 1.32ngg−1 dry weight (d.w.) and limits of quantification were between 0.12 and 3.96ngg−1 (d.w.). The method was applied to the analysis of particulate matter, where cocaine (COC), benzoylecgonine (BECG), ecgoninemethylester (ECME), cocaethylene (COCET), methadone (MET) and codeine (COD) were mostly detected. In the case of dehydrated sludge, opioids are at higher concentration than cocainics and some emerging drugs such as 4-methoxyamphetamine (PMA), ketamine (KET) and bufotenine (BUF) were detected. In sediment COC, 4-methoxyphencyclidine (4-MeO-PCP), MET and BECG were most relevant compounds.

A Simplified Analytical Procedure for Simultaneous Determination of Alkylphenol Ethoxylates and Brominated Flame Retardants in Fish Tissue Samples from Vaal River, South Africa

In this study, the concentration of alkylphenol ethoxylates (APEs) and brominated flame retardants (BFRs) were determined in fish samples, Labeo umbratus and Carp, collected from the Vaal River in South Africa. Ultrasonic-assisted extraction technique was used to extract the organic contaminants from fish samples, and the resulting extract was purified by sulphuric acid lipid removal followed by Strata X-cartridge SPE clean-up. The APEs and BFRs were derivatized using heptafluorobutyric anhydride before analysis with GC-MS. In both types of fish samples, lower oligomers of APEs were more abundant than the higher oligomers, while HBCD, BDE99 and PBB101 were the dominant BFRs. The concentrations of these pollutants ranged from 1.061 ng/g lipids (t-BP) in Labeo umbratus to 11.860 ng/g lipids (HBCD) in Carp.

Comparison of Two Analytical Methods for the Determination of Traces of Veterinary Antibiotics and Steroid Hormones in Soil Based on Pressurised Liquid Extraction (PLE) and Quick, Easy, Cheap, Effective, Rugged, Safe (Modified-Quechers) Extraction

Veterinary antibiotics and steroid hormones can be present at low levels in soil. Analytical methodologies are therefore necessary to analyse these compounds at the trace level in such a complex matrix. The goal of this work was to compare Pressurised Liquid Extraction (PLE), which is usually used to extract drugs from soil, and a modified-QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method. Furthermore, several clean-up methods were evaluated. Selective Pressurised Liquid Extraction (SPLE) and Dispersive Solid Phase Extraction (dSPE) used after PLE and QuEChERS, respectively, were tested. These techniques permit a fast and simple purification step. SPE, which is frequently used, was also evaluated. To perform this comparison, both recoveries and matrix effects were compared and the analyses were performed using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). SPLE and dSPE did not significantly decrease matrix effects. A tandem SPE using SAX and Strata-X cartridges offered the best efficiency. Regarding the comparison between PLE and QuEChERS, the modified-QuEChERS led to better recoveries for certain substances. No significant differences were noted in term of matrix effects. Therefore, the modified-QuEChERS method is recommended.

Simultaneous detection of three antiviral and four antibiotic compounds in source-separated urine with liquid chromatography

An analytical method for the simultaneous screening of three antiviral agents (nevirapine, zidovudine, lamivudine), four antibiotics (sulfamethoxazole, trimethoprim, ciprofloxacin, rifampicin) and one reference compound (carbamazepine) in human urine was developed. Separation was achieved with a Kinetex XB-C18 (75 × 4.6 mm, 2.6 μm) column after the extraction of pharmaceuticals from urine with SPE. Gradient elution with a mobile phase consisting of acetonitrile and 10 mM KH2 PO4 (pH 2.5), and diode array detection with monitoring at 210 and 264 nm was applied. The developed method was validated in terms of selectivity, linearity, stability and sensitivity. Repeatability (n = 3) and between-day precision (n = 3) revealed RSD <5%. The detection limits were estimated as 0.02-0.54 g/L (depending on compound). The method was validated for human urine and successfully applied to the simultaneous quantification of selected compounds. Strata-X cartridges provided good recoveries ranging from 81 to 109%. The limits of detection for urine varied between 0.04 and 1.61 g/L. The method is suitable for the fast determination of selected pharmaceuticals from source-separated urine samples for further environmental risk assessment and degradation potential evaluation. It provides a way to enhance safe nutrient recycling from wastewater streams and promotes the safe use of urine as fertiliser.

A liquid chromatography/electrospray ionization tandem mass spectrometric method for the quantification of calcitriol in human plasma: application to pharmacokinetic study in human subjects

Calcitriol is a synthetic vitamin D analog which is active in the regulation of the absorption of calcium from the gastrointestinal tract and its utilization in the body. Circulating concentrations of endogenous calcitriol complicate the analysis of pharmacokinetic parameters and the determination of bioequivalence (BE) when the drug is administered exogenously. The main objective of this study is to evaluate the significance of endogenous concentration and baseline correction in the bioequivalence assessment of drug Calcitriol. An ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method has been developed for the determination of Calcitriol in human plasma using Calcitriol d6 as the internal standard by means of baseline correction approach. The plasma samples were prepared by solid phase extraction on Phenomenex Strata-X cartridges using 500µL human plasma sample. Chromatography was carried out on Waters Acquity UPLC BEH C18 (100mm × 2.1mm, 1.7µ) analytical column under gradient conditions using a mobile phase consisting of acetonitrile–4.0 mM ammonium trifluoroacetate. The precursor to product ion transition for the analyte and IS was monitored on Waters Xevo TQ-S triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and positive ionization mode. The method was validated over a wide dynamic concentration range of 5–200 pg/mL for Calcitriol. Stability was evaluated under different conditions including bench top, processed sample, freeze and thaw and long term. The method was applied to support a bioequivalence study of 0.5 mcg fixed dose formulation in 10 healthy Indian subjects. Assay reproducibility was demonstrated by reanalysis of 120 incurred samples.