Metabolites In Aqueous Samples Research Articles

Determination of polybrominated diphenyl ethers and metabolites by single-drop microextraction and GC–MS/MS

A simple, fast and virtually solvent-free method for the simultaneous determination of 13 polybrominated diphenyl ethers (PBDEs) congers and their metabolites in aqueous samples was developed using single-drop microextraction (SDME) coupled with gas chromatography-tandem mass spectrometry (GC–MS/MS). Optimization over GC–MS/MS parameters of both electron ionization (EI) and negative chemical ionization (NCI) sources were studied and compared with a result that EI is more sensitive and selective, especially for lower brominated congeners. Optimization of SDME was subsequently conducted. Under optimum conditions (1 μL drop of chlorobenzene in 2 mL sample solution, pH 5.0, 30 min extraction time, stirring rate of 400 rpm), the assay linearity of target PBDEs was confirmed over 2–3 orders of magnitudes, with a coefficient of determination (r2) ranged from 0.9929 to 0.9998. The limit of detection (LODs) and limit of quantification (LOQs) for lower brominated congeners were found to be better than 6 ng·L−1 and 20 ng·L−1, respectively. Real sample analysis with an isotopic internal standard was carried out. The recoveries, relative standard deviation (RSD) and enrichment factors obtained ranged from 73.4 to 128.0%, 7.52 to 25.0% and 8 to 60, respectively, indicating the developed method is suitable for the determination of PBDE congers in aqueous samples.

Characterization of supported liquid extraction as a sample pretreatment method for eicosanoids and related metabolites in biological fluids

Sample pretreatment is an important process in liquid chromatography-mass spectrometry-based quantitative lipidomics. Reversed-phase solid phase extraction (RP-SPE) has been widely used for analyzing various types of samples, including aqueous samples such as cell culture media, plasma, serum, urine, and other biological fluids. Because lipid mediators are often protein-bound, prior deproteinization is necessary for their effective recovery. Deproteinization is typically performed by the addition of organic solvents, which requires time-consuming evaporation–reconstitution, or dilution with aqueous solvents before RP-SPE; however, both of these approaches compromise the analytical performance. As a potential alternative, we attempted to utilize supported liquid extraction (SLE), an automation-compatible variant of liquid-liquid extraction, for the determination of eicosanoids and related metabolites in aqueous samples. We screened 81 different sample diluent–eluent conditions and found that the use of 0.1% formic acid-water as the diluent and 0.1% formic acid-methyl acetate as the eluent enabled the optimum recovery of a variety of eicosanoids, except for peptide leukotrienes. The optimized SLE method efficiently removed protein from human plasma, while phospholipids and neutral lipids were modestly recovered. Moreover, the proposed method exhibited a quantitative performance comparable to that of typical ordinary RP-SPE method in the analysis of human platelets stimulated with thrombin receptor-activating peptide 6. Thus, we propose SLE as an attractive option for rapid lipid mediator extraction from aqueous samples.

A fast and sensitive analytical procedure for monitoring of synthetic pyrethroid pesticides' metabolites in environmental water samples

In this paper, we report a simple, fast, and sensitive analytical procedure for monitoring of synthetic pyrethroid pesticides' (SPPs') metabolites in environmental water samples using a novel vortex-assisted salt-induced liquid-liquid microextraction (VA-SI-LLME) method coupled with liquid chromatography/tandem mass spectrometric (LC-MS/MS) analysis. VA-SI-LLME was carried out by taking 4 mL of sample solution followed by the addition of isopropanol and ethyl acetate (0.4 mL, 1:2, v/v) as a binary extraction solvent, and 4 g of ammonium sulfate for phase separation. Then, the mixture solution was vortex for 2 min and centrifuged for 3 min to collect the extractant and inject into LC-MS/MS for analysis. Experimental factors affecting the VA-SI-LLME including extraction solvent, extraction solvent volume, salt type, amount of salt, extraction time, and sample pH were completely optimized. The developed analytical method was validated, and the results exhibited good linearity in the concentration ranges between 0.01–100 ng mL−1 with the correlation coefficient (r2) >0.992 for the target SPPs' metabolites. Excellent limit of quantification and precision were achieved in the range between 0.01–0.1 ng mL−1, and 1.55–5.06% (in terms relative standard deviation), respectively. The developed method was employed to determine the target SPPs' metabolites in tap, lake, river water, and influent wastewater samples collected in Kaohsiung city area, Taiwan. The extraction recoveries of spiked samples were satisfactory. Therefore, the presented method can be used as a potential alternative analytical procedure for monitoring of pesticides' metabolites in aqueous samples.

Innovative SPE-LC-MS/MS technique for the assessment of 63 pharmaceuticals and the detection of antibiotic-resistant-bacteria: A case study natural water sources in Lebanon

A powerful analytical method for simultaneous determination of 63 pharmaceuticals and some metabolites in aqueous samples has been developed. The list of compounds amenable to the methods includes different therapeutic classes belonging to antibiotics, stimulants, antidepressants, mucolytics, and antiparasites. The method involves concentration and clean up by an offline solid phase extraction SPE followed by liquid chromatography coupled to tandem mass spectrometry (LC-ESI-MS/MS). The recovery of the target compounds from water samples was most efficient on Waters Oasis HLB SPE cartridge, while acetonitrile/water (60/40) was shown to be the most suitable solvent for desorbing the compounds from SPE. In addition, acidification of samples prior to SPE was optimized to enhance the recovery of the compounds. In terms of method validation, the recoveries of analytes ranged from 68% to 134%. Repeatability and intermediate precision were <11% and 14%, respectively. The method detection limits ranged from 2.3ngL−1 to 94.3ngL−1. An optimized method was applied in a monitoring program to study the occurrence of pharmaceuticals to more than hundred samples collected from rivers, lakes, fountains, and wells overall Lebanon from April to June 2016. Caffeine, erythromycin and its degradation forms, were the most frequently detected compounds at levels reaching >10,000ngL−1 and 2000ngL−1, respectively. Moreover, bacterial analysis showed that the samples were contaminated by Escherichia coli (23%), intestinal Enterococcus (48%) and Pseudomonas aeruginosa (27%). Therefore, in order to evaluate if a correlation exists between finding antibiotics in water samples and the development of resistant-bacteria, an antimicrobial susceptibility test was conducted to the identified isolates using disk diffusion method. Multiple-antibiotic-resistant strains in both intestinal Enterococcus and E. coli were evident in many water samples, while P. aeruginosa was resistant to only one studied antibiotic.

NMR profiling clarifies the characterization of Finnish honeys of different botanical origins

The Finnish varietal honeys are valued specialty foods with unique characteristics, owing to their botanical origin. 1H NMR metabolomics was applied to examine the compositional differences and origin-related markers of naturally complex boreal honeys (buckwheat, clover, dandelion, heather, Himalayan balsam, honeydew, linden, lingonberry, multifloral). Special focus was on the metabolites in aqueous samples. Chloroform extracts of selected samples were also analyzed for additional metabolic evidence.Qualitative profiling revealed 2-hydroxy-3-methylbutyric, 2-hydroxy-3-methylpentanoic, 3-methyl-2-oxopentanoic and 4-methyl-2-oxopentanoic acids as specific markers for dandelion (Taraxacum spp.) honeys. Full discrimination of buckwheat, dandelion, heather, and honeydew honeys was achieved with principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Melezitose, glucose, and fructose explained 83% of the variation in the PCA. The OPLS-DA loadings highlighted the discriminatory effect of the origin-specific non-saccharide metabolites.This study is a platform for a national honey library and analysis service. The results will facilitate and rationalize the characterization and quality control of the boreal varietal honeys.

Direct silylation of Trypanosoma brucei metabolites in aqueous samples and their GC-MS/MS analysis.

A simple two-step method for the derivatization of polar compounds (lactate, alanine, glycerol, succinate and glucose) using hexamethyldisilazane (HMDS) and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) was developed. This method allows direct derivatization of aqueous samples wihout sample pretreatment. The method was used for the analysis of the metabolites of the unicellular organism Trypanosoma brucei. The limits of detection by GC-MS/MS analysis were in the range of 0.02 mg L(-1) for glucose to 0.85 mg L(-1) for lactate.

Rapid determination of dichlorodiphenyltrichloroethane and its main metabolites in aqueous samples by one-step microwave-assisted headspace controlled-temperature liquid-phase microextraction and gas chromatography with electron capture detection

A rapid and sensitive analytical method for the determination of dichlorodiphenyltrichloroethane (DDT) and its main metabolites in environmental aqueous samples has been developed using one-step microwave-assisted headspace controlled-temperature liquid-phase micro-extraction (MA-HS-CT-LPME) technique coupled with gas chromatography–electron-capture detection (GC–ECD). In this study, the one-step extraction of DDT and its main metabolites was achieved by using microwave heating to accelerate the evaporation of analytes into the controlled-temperature headspace to form a cloudy mist vapor zone for LPME sampling. Parameters influencing extraction efficiency were thoroughly optimized, and the best extraction for DDT and its main metabolites from 10-mL aqueous sample at pH 6.0 was achieved by using 1-octanol (4-μL) as the LPME solvent, sampling at 34 °C for 6.5 min under 249 W of microwave irradiation. Under optimum conditions, excellent linear relationship was obtained in the range of 0.05–1.0 μg/L for 1-dichloro-2,2-bis-( p′-chlorophenyl)ethylene ( p, p′-DDE), 0.1–2.0 μg/L for o, p′-DDT, 0.15–3.0 μg/L for 1,1-dichloro-2,2-bis-( p′-chlorophenyl)ethane ( p, p′-DDD) and p, p′-DDT, with detection limits of 20 ng/L for p, p′-DDE, and 30 ng/L for o, p′-DDT, p, p′-DDD and p, p′-DDT. Precision was in the range of 3.2–11.3% RSD. The proposed method was validated with environmental water samples. The spiked recovery was between 95.5% and 101.3% for agricultural-field water, between 94% and 99.7% for sea water and between 93.5% and 98% for river water. Thus the established method has been proved to be a simple, rapid, sensitive, inexpensive and eco-friendly procedure for the determination of DDT and its main metabolites in environmental water samples.

Determination of triazines and their metabolites in environmental samples using molecularly imprinted polymer extraction, pressurized liquid extraction and LC–tandem mass spectrometry

Summary The present work describes the development of a selective and sensitive method for the simultaneous determination of triazines and triazine metabolites in waters and soils, and its further application to natural samples. The method is based on sample extraction and pre-concentration with commercial molecularly imprinted polymer cartridges (MIP4SPE Triazine 10) followed by liquid chromatography–tandem mass spectrometric (LC–MS/MS) analysis operating in the selected reaction monitoring (SRM) mode. Method detection limits achieved were as low as 0.015 ng L −1 (ground water) and 0.2 ng kg −1 (soil and sludge). Method recovery rates were found to be analyte dependent, ranging from 55% to 123%. The intra-day and inter-day precision was given by RSD values between 2% and 4% and between 6% and 10%, respectively for the latter for most compounds. The suitability of the method for the environmental trace analysis of triazine pesticides and their metabolites in aqueous samples was demonstrated through the analysis of several ground water and sludge-amended soil samples. The outcomes of this study revealed that simazine was the most frequently found analyte in ground water, with values up to 105.11 ng L −1 . Results also evidenced that all the pesticides investigated were present in the solid matrices, being sebuthylazine that at the highest concentrations, with values ranging from 0.46 to 2.26 ng g −1 . Pesticide concentrations in the sludge applied as fertilized were generally low, which indicated that their contribution to the total amount of pesticides in the soil was not quantitatively relevant in comparison with that of pesticides coming from direct spreading to agricultural lands.

Automated high-performance liquid chromatographic extraction and quantification procedure for lipoxygenase metabolites

A number of methods have been used to measure various lipoxygenase metabolites in aqueous samples. These methods, however, suffer from three major limitations: first, they require extensive extraction and isolation from protein-containing media; second, mainly due to the first limitation, they have poor recoveries; and third, these methods usually require a two-step procedure, one for the actual extraction and the other for the quantification of the lipoxygenase metabolites. We have developed a fully automated high-performance liquid chromatographic method which circumvents these limitations. As a result, we are able to obtain high recoveries of various lipoxygenase metabolites from protein-containing samples (i.e. biological samples) while simultaneously quantifying each metabolite. The method employs a column venting technique, whereby the fatty acids are extracted by a pre-column and the proteins are vented to waste. The pre-column eluate is then directed through the analytical column which separates the lipoxygenase metabolites. The described method is reproducible and minimizes both the time and the cost involved in assaying a sample.