High-performance anion-exchange chromatography–mass spectrometry method for determination of levoglucosan, mannosan, and galactosan in atmospheric fine particulate matter

Biomass burning has a strong influence on the atmospheric aerosol composition through particulate organic, inorganic, and soot emissions. When biomass burns, cellulose and hemicelluloses degrade, producing monosaccharide anhydrides (MAs) such as levoglucosan, mannosan, and galactosan. Therefore, these compounds have been commonly used as tracers for biomass burning. In this study, a fast water-based method was developed for the routine analysis of MAs, based on high-performance anion-exchange chromatography with electrospray ionization mass spectrometry detection. This method combines simple sample preparation, fast separation, and the advantages of the selective detection with MS. Analysis run was optimized to the maximum separation of levoglucosan, mannosan, and galactosan with 15-min analysis. The validation results indicated that the method showed good applicability for determination of MA isomer concentrations in ambient samples. The limit of detection was 100 pg for levoglucosan and 50 pg for mannosan and galactosan. Wide determination ranges enabled the analysis of samples of different concentration levels. The method showed good precision, both for standard solutions (3.9–5.9% RSD) and for fine particle samples (4.3–8.5% RSD). Co-elution of internal standard (carbon-13-labeled levoglucosan) and sugar alcohols with levoglucosan decreased the sensitivity of levoglucosan determination. The method was used to determine the MA concentrations in ambient fine particle samples from urban background (Helsinki) and rural background (Hyytiälä) in Finland. The average levoglucosan, mannosan, and galactosan concentrations were 77, 8.8, and 4.2 ng?m^?3 in Helsinki (winter 2008–2009) and 17, 2.3, and 1.4 ng?m^?3 in Hyytiälä (spring 2007), respectively. The interrelation of the three MA isomers was fairly constant in the ambient fine particle samples.     

Derivatization procedures and determination of levoglucosan and related monosaccharide anhydrides in atmospheric aerosols by gas chromatography-mass spectrometry

This study evaluated the derivatization procedures for detecting the three most commonly monosaccharide anhydrides (MAs) (levoglucosan, mannosan and galactosan) in atmospheric aerosols using gas chromatography-mass spectrometry (GC-MS). Various silylating agents, mainly trimethylsilylating agents (TMS), were compared and the effects of various contents of trimethylchlorosilane (TMCS, as a stimulator) were evaluated to optimize the conditions for detecting these compounds in aerosol samples. Differences among the abundances of the derivatives were caused by the sterical hindrance of three hydroxyl groups in the structures of monosaccharide anhydrides. The effects of the reaction time and temperature were also examined. The optimal reaction time and temperature were 60 min and 80 °C with 1% TMCS plus 0.2% 1,4-dithioerythritol (DTE). Under these conditions, the percentages of formation of bis-O-TMS derivatives (as by-products) were 23, 29 and 10% for galactosan, mannosan and levoglucosan, respectively. The concentrations of galactosan, mannosan and levoglucosan in particles of smoke samples ranged from 29 to 88, 23 to 69 and 77 to 380 ng/m³, respectively; and in particles of atmospheric aerosols ranged from 0.06 to 0.75, n.d. to 0.49 and 1.6 to 132 ng/m³, respectively. Levoglucosan was the dominant MAs detected in both type of samples. Less than 10% quantitation difference was obtained when bis-O-TMS derivatives were included in the calculation.     

Determination of methylisothiocyanate in soil and water by HS-SPME followed by GC–MS–MS with a triple quadrupole

Methylisothiocyanate (MITC) is the main degradation product of metam sodium, a soil disinfectant widely used in agriculture, and is responsible for its disinfectant properties. Because MITC is highly toxic and volatile, metam sodium has to be applied in a manner that tries to reduce atmospheric emissions but still maintains adequate concentration of MITC in soil to ensure its disinfectant effect. Thus, monitoring of MITC concentrations in soil is required, and to this end sensitive, fast, and reliable analytical methods must be developed. In this work, a headspace solid-phase microextraction (HS-SPME) method was developed for MITC determination in water and soil samples using gas chromatography-tandem mass spectrometry (GC–MS–MS) with a triple-quadrupole analyzer. Two MS–MS transitions were acquired to ensure the reliable quantification and confirmation of the analyte. The method had linear behavior in the range tested (0.026–2.6 ng mL^?1 in water, 1–100 ng g^?1 in soil) with r ² over 0.999. Detection limits were 0.017 ng mL^?1 and 0.1 ng g^?1 in water and soil, respectively. Recoveries for five replicates were in the range 76–92 %, and RSD was below 7 % at the two spiking levels tested for each matrix (0.1 and 1 ng mL^?1 for water, 4 and 40 ng g^?1 for soil). The potential of using multiple HS-SPME for analyzing soil samples was also investigated, and its feasibility for quantification of MITC evaluated. The developed HS-SPME method was applied to soil samples from experimental plots treated with metam sodium following good agriculture practices. Figure

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LC–MS–MS Simultaneous Determination of l-Dopa and Its Prodrug l-Dopa n-Pentyl Ester Hydrochloride in Rat Plasma

A sensitive, simple and rapid LC–MS–MS method has been developed and validated for the simultaneous determination of l-dopa and l-dopa n-pentyl ester hydrochloride in rat plasma in the present study. The analytes were separated on a C₁₈ column (5 μm, 2.1 × 150 mm) with a security guard C₁₈ column (5 μm, 4 × 20 mm) and a triple-quadrupole mass spectrometer was applied for detection. The method was linear over the concentration ranges of 25–5,000 ng mL^?1 for l-dopa and 12.5–2,500 ng mL^?1 for l-dopa n-pentyl ester hydrochloride. Finally, the method was successfully applied to support the pharmacokinetic study.     

Determination of migrated phthalic acid residues into edible oils using a green mode of air-assisted liquid–liquid microextraction followed by high-performance liquid chromatography–diode array detector

In this study, for the first time, an organic solvent-free air-assisted liquid–liquid microextraction method has been reported for the extraction and preconcentration of phthalic acids (o-phthalic acid, m-phthalic acid, and p-phthalic acid) from edible oil samples. The method is based on the repeated aspirating/injection of an alkaline aqueous solution and the oil sample mixture in a conical bottom centrifuge tube to form a cloudy solution. After phase separation by centrifuging, the sedimented phase is directly analyzed by high-performance liquid chromatography–diode array detection. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.11–0.29 and 0.28–0.91 ng mL^?1, respectively. Extraction recoveries and enrichment factors were from 81 to 97% and 406 to 489, respectively. The relative standard deviations for the analysis of 5 ng mL^?1 of each analyte were less than 5.9% for intraday (n = 6) and interday (n = 5) precisions. Finally, different oil samples were successfully analyzed using the proposed method and m-phthalic acid, and p-phthalic acid were determined in some of them at ng mL^?1 level.     

Enantioselective Separation and Determination of Carnosine in Rat Plasma by Fluorescence LC for Stereoselective Pharmacokinetic Studies

A sensitive fluorescence liquid chromatographic analytical method was developed for the simultaneous determination of carnosine enantiomers in rat plasma. The method was applied to pharmacokinetic studies. Chiral separation of carnosine enantiomers was achieved by pre-column derivatization with o-phthaldialdehyde and the thiol N-acety-l-cysteine as derivating reagents. They were separated on an ODS column and detected by fluorescence detection (λ_ex = 350 nm, λ_em = 450 nm). γ-Aminobutyric acid was used as internal standard. The method was linear up to 6,000 ng mL^?1 for l-carnosine, 4,000 ng mL^?1 for d-carnosine. Low limit of quantitation (LLOQ) was 40 ng mL^?1 for each isomer. The relative standard deviations obtained for intra- and inter-day precision were lower than 12% and the recoveries were higher than 75% for both enantiomers. The method was applied to a stereoselective study on the pharmacokinetics of carnosine after oral administration with a single dose (carnosine, 75 mg kg^?1 for each isomer) to a rat. The initial data indicated that l-carnosine had a larger value of the highest plasma concentration than d-carnosine (C _max 5,344 vs. 1,914 ng mL^?1), and that of l-carnosine had a lower value of AUC_(0?∞) and t _1/2(h) (AUC_(0?∞) 5,306 vs. 6,321 ng h mL^?1, t _1/2 1.43 vs. 3.37 h). Our results indicated that the pharmacokinetic of l-carnosine and d-carnosine revealed enantioselective properties significantly.     

Determination of phthalate esters in edible oils by use of QuEChERS coupled with ionic-liquid-based dispersive liquid–liquid microextraction before high-performance liquid chromatography

A selective and low organic-solvent-consuming method of sample preparation combined with high-performance liquid chromatography with diode-array detection is introduced for analysis of phthalic acid esters in edible oils. Sample treatment involves initial liquid–liquid partitioning with acetonitrile, then QuEChERS cleanup by dispersive solid-phase extraction with primary secondary amine as sorbent. Preconcentration of the analytes is performed by ionic-liquid-based dispersive liquid–liquid microextraction, with the cleaned-up extract as disperser solvent and 1-hexyl-3-methylimidazolium hexafluorophosphate as extraction solvent. Under the optimized conditions, correlation coefficients (r) were 0.998–0.999 and standard errors (S _y/x ) were 2.67–3.37?×?10³ for calibration curves in the range 50–1000 ng g^?1. Detection limits, at a signal-to-noise ratio of 3, ranged from 6 to 9 ng g^?1. Intra-day and inter-day repeatability, expressed as relative standard deviation, were in the ranges 1.0–6.9 % and 2.4–9.4 %, respectively. Recovery varied between 84 % and 106 %. The developed method was successfully used for analysis of the analytes in 28 edible oils. The dibutyl phthalate content of four of the 28 samples (14 %) exceeded the specific migration limit established by domestic and international regulations.

Chitosan-poly(m-phenylenediamine)@Fe3O4 nanocomposite for magnetic solid-phase extraction of polychlorinated biphenyls from water samples

A extraction medium based on chitosan-poly(m-phenylenediamine) (CS-PPD) @Fe₃O₄ nanocomposite was synthesized by chemical polymerization of m-phenylenediamine in the presence of chitosan coated magnetic nanocomposite, and for the first time, used as the sorbent for the magnetic solid-phase extraction (MSPE) of seven polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, and PCB180) at trace levels in water samples. Gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was used for PCBs quantification and detection. Several factors related to MSPE efficiencies, such as type and amount of sorbent, extraction time, sample pH, and desorption conditions were investigated. Under the optimized conditions, an excellent linearity was observed in the range of 1.0–200 ng L^–1 for PCB180, 0.5–200 ng L^–1 for the other six PCBs with the correlation coefficients ranging from 0.9954 to 0.9993. The good recoveries at spiked levels of 10.0, 20.0, and 50.0 ng L^–1 were obtained in the range of 94 %–108 %, and the coefficients of variations were less than 6 %. The proposed method was feasible, rapid, and easy to operate for the trace analysis of the PCBs in local aquaculture water, livestock breeding water, and sewage water samples. Graphical Abstract

Fig. 1 Schematic diagram for the preparation of chitosan–poly(m-phenylenediamine) @Fe₃O₄ nanocomposite.     

Magnetic titanium oxide nanoparticles for hemimicelle extraction and HPLC determination of organophosphorus pesticides in environmental water

We report on a method for the extraction of organophosphorus pesticides (OPPs) from water samples using mixed hemimicelles and magnetic titanium dioxide nanoparticles (Fe₃O₄@TiO₂) modified by cetyltrimethylammonium. Fe₃O₄@TiO₂ nanoparticles were synthesized by a hydrothermal process and then characterized by scanning electron microscopy and Fourier transform IR spectrometry. The effects of the quantity of surfactant, extraction time, desorption solvent, pH value, extraction volume and reuse of the sorbent were optimized with respect to the extraction of OPPs including chlorpyrifos, dimethoate, and trichlorfon. The extraction method was applied to analyze OPPs in environmental water using HPLC along with UV detection. The method has a wide linear range (100–15,000 ng L^?1), good linearity (r?>?0.999), and low detection limits (26–30 ng L^?1). The enrichment factor is ~1,000. The recoveries (at spiked levels of 100, 1,000 and 10,000 ng L^?1) are in the range of 88.5–96.7 %, and the relative standard deviations range from 2.4 % to 8.7 %.

Cetyltrimethylammonium-coated magnetic nanoparticles for the extraction of bromate,followed by its spectrophotometric determination

We report on a combination of magnetic solid-phase extraction and spectrophotometric determination of bromate. Cetyltrimethylammonium ion was adsorbed on the surface of phenyl-functionalized silica-coated Fe₃O₄ nanoparticles (Ph-SiO₂@Fe₃O₄), and these materials served as the sorbent. The effects of surfactant and amount of sorbent, the composition of the desorption solution, the extraction time and temperature were optimized. Under optimized conditions, an enrichment factor of 12 was achieved, and the relative standard deviation is 2.9 % (for n?=?5). The calibration plot covers the 1–50 ng mL^?1 range with reasonable linearity (r ²?>?0.998); and the limit of detection is 0.5 ng mL^?1. The method is not interfered by ionic compounds commonly found in environmental water samples. It was successfully applied to the determination of bromate in spiked water samples.

A sensitive immunosorbent bio-barcode assay based on real-time immuno-PCR for detecting 3,4,3',4'-tetrachlorobiphenyl

A functionalized gold-nanoparticle bio-barcode assay, based on real-time immuno-PCR (IPCR), was designed for the determination of 3,4,3',4'-tetrachlorobiphenyl (PCB77). 15 nm gold nanoparticles were synthesized, and modified with thiol-capped DNA and goat anti-rabbit IgG. The nanoparticle probes were used to replace antibody–DNA conjugate in the IPCR, and were fixed on the PCR tube wall via the immune reaction. Real-time PCR was performed to quantify the DNA signal directly. Under optimized conditions, the new method was used to detect PCB77 with a linearity range from 5 pg L^?1 to 10 ng L^?1, and the limit of detection (LOD) was 1.72 pg L^?1. Real samples of Larimichthys polyactis, collected from the East China Sea, were analyzed. Recovery was from 82 % to 112 %, and the coefficient of variation (CV) was acceptable. The results were compared with GC–ECD, revealing that the method would be acceptable for providing rapid, semi-quantitative, and reliable test results for making environmental decisions.

Phytochemical Study of the Rhizome of Pinellia ternata and Quantification of Phenylpropanoids in Commercial Pinellia Tuber by RP-LC

Four phenylpropanoids, (E)-p-coumaryl alcohol (1), 3,4-dihydroxycinnamyl alcohol (2), sachaliside 1 (3), and coniferin (4) have been isolated from the rhizome of Pinellia ternata. Their structures were elucidated by spectroscopic methods. Compounds 1–3 were isolated from the genus Pinellia for the first time. Compound 4 was isolated from this plant for the first time. A rapid, sensitive, and accurate reversed-phase high-performance liquid chromatographic method with UV detection at 260 nm was established for simultaneous separation and determination of the four phenylpropanoids in nineteen batches of dried rhizomes of P. ternata. Compounds were separated on a 250 × 4.6 mm C₁₈ column with methanol–acetonitrile–water–phosphoric acid, 20:5:75:0.3, as mobile phase. The amounts of 1–4 in the rhizome of P. ternata could be easily determined within 30 min. The linear calibration ranges for 1–4 were 0.05–137.50, 0.66–1050.00, 0.06–30.00, and 0.05–67.50 μg mL^?1, respectively. Recovery of 1–4 was 97.43–103.73%, with RSD from 0.12 to 1.62%. Limits of quantification for 1–4 were 50, 660, 60, and 50 ng mL^?1, respectively. The method was successfully used for phytochemical analysis of phenylpropanoids from the rhizome of P. ternata.     

Preconcentration of trace cadmium ion using magnetic graphene nanoparticles as an efficient adsorbent

Graphene-based magnetic nanoparticles (G-Fe₃O₄) were prepared and used as an effective adsorbent for the solid-phase extraction of trace quantities of cadmium from water and vegetable samples. The method avoids some of the time-consuming steps associated with traditional solid phase extraction. The excellent sorption property of the G-Fe₃O₄ system is attributed to π - π stacking interaction and hydrophobic interactions between graphene and the Cd-PAN complex. The effects of pH, the amount of G–Fe₃O₄, extraction time, type and volume of eluent, desorption time and interfering ions on the extraction efficiency were optimized. The preconcentration factor is 200. Cd(II) was then quantified by flame atomic absorption spectrometry with a detection limit of 0.32 ng mL^?1. The relative standard deviation (at 50 ng mL^?1; for n?=?10) is 2.45 %. The method has a linear analytical range from 1.1 to 150 ng mL^?1, and the recoveries in case of real samples are in the range between 93.1 % and 102.3 %.

LC–MS/MS Determination of Antihypertension Drugs in Rat Plasma and Urine: Applications to Pharmacokinetics

A sensitive, rapid and reproducible LC–MS/MS method for the determination of olmesartan (OLM), amlodipine (ALM) and hydrochlorothiazide (HCZ) in rat plasma and urine has been developed and validated. Irbesartan (IRB) was used as an internal standard. The analytes were separated on a Waters XTerra-C₁₈ column using gradient elution with acetonitrile and 10 mM ammonium acetate buffer (pH 3.5, adjusted with acetic acid) at a flow rate of 1.0 mL min^?1. The three analytes were ionized by positive ion electrospray using multiple-reaction monitoring (MRM) mode to monitor precursor?→?product ion transitions m/z 447.31?→?234.97 for OLM, 408.87?→?238.18 for AML and 290.1?→?204.85 for HCZ. The specificity, matrix effect, recovery, sensitivity, linearity, accuracy, precision, and stabilities were all validated over the concentration range 0.4–100 ng mL^?1 for AML, 0.2–100 ng mL^?1 for OLM, 0.1–100 ng mL^?1 for HCZ. The mean concentrations (C_max) are 10.32, 587, and 3.4 for OLM, ALM, and HCZ, respectively, by the oral administration of 15 mg kg^?1 of each analyte.     

LC-MS Determination and Pharmacokinetic Study of Luteolin-7-O-β-d-glucoside in Rat Plasma after Administration of the Traditional Chinese Medicinal Preparation Kudiezi Injection

A rapid and sensitive LC-MS method has been developed for the determination of luteolin-7-O-β-d-glucoside in rat plasma after solvent extraction. Separation was on an Elite Hypersil ODS2 column (250 mm × 4.6 mm i.d., 5 μm) with a mobile phase of acetonitrile-0.3% acetic acid (26:74, v/v). The samples were analyzed by using positive electrospray ionization MS in selected ion monitoring mode. The selected ions for luteolin-7-O-β-d-glucoside and the internal standard, isoquercitrin, were m/z 448.95 and m/z 464.95. Good linearity was observed over the range of 20–2,000 ng mL^?1 with a lower limit of quantification of 20 ng mL^?1. No interference peaks or matrix effects were observed. The validated method was applied to the pharmacokinetic study of luteolin-7-O-β-d-glucoside in rat plasma after intravenous administration of Kudiezi Injection.     

Separation and Sensitive Analysis of Chlorophenols by MEEKC

A new microemulsion electrokinetic chromatographic method has been established for separation and sensitive analysis of the three chlorophenols 2-chlorophenol, 4-chlorophenol, and 2,4-dichlorophenol. The optimum microemulsion system was 15 mM SDS, 112 mM n-butanol, and 10 mM n-octane in 20 mM sodium tetraborate (pH 9.0). Under the optimum conditions, baseline separation was achieved within 8 min. The method was used for analysis of a real water sample previously pretreated by SPE. The linear ranges, precision of migration time and peak area, and limits of detection (LOD) were in the ranges of 0.5–50 μg L^?1, 4.85–9.75%, 0.49–0.706% (n = 6), and 0.6–1 μg L^?1, respectively, for the three chlorophenols.     

Simultaneous Determination of Levoglucosan,Mannosan and Galactosan at Trace Levels in Snow Samples by GC/MS

A method for the simultaneous determination of levoglucosan, mannosan and galactosan at trace levels in snow samples is reported by using GC/MS. This method is an improvement on previous aerosol studies. The required sample volume for this method is a mere 5.00 mL of melt water. Discrimination of three isomers is analyzed on the basis of different retention time and fragmentation patterns. The limit of detection is 0.070, 0.058 and 0.046 ng mL^?1 ice melt water for three isomers. This method has the advantage of simultaneous determination of three monosaccharide anhydrides at trace concentration levels in small sample volumes. The relatively high extraction efficiency and low limit of detection will facilitate further studies on biomass burning recorded in snow and ice samples.     

An Improved Narrow-Bore LC Method for Quantification of Alfuzosin in Pharmaceutical Formulations

A simple rapid and stability-indicating LC method using a narrow-bore column has been developed, fully validated, and applied to the quantification of alfuzosin in pharmaceutical formulations. Chromatography was achieved isocratically on a narrow-bore, 5-μm particle size, C₈ analytical column. The mobile phase was a 35:65 (v/v) 0.0125 m ammonium formate–acetonitrile at a flow rate of 0.35 mL min^?1. Detection was by UV absorption at 245 nm. Evaluation over the range 200–800 ng mL^?1 revealed linearity was good. Limits of detection and quantification for alfuzosin were 22.9 and 69.5 ng mL^?1, respectively. Intra-day and inter-day RSD were less than 6.4%, and the relative percentage error was less than ?1.7% (n = 5). Accelerated degradation performed under different stress conditions including oxidation, hydrolysis, and heat, proved the selectivity of the procedure. The method was successfully used for quality-control and content-uniformity testing of commercial tablets.     

Micro-solid phase extraction of ochratoxin A, and its determination in urine using capillary electrophoresis

We describe a simple, environmentally friendly and selective technique for the determination of ochratoxin A (OTA) in urine. It involves (a) the use of a molecularly imprinted polymer as a sorbent in micro-solid-phase extraction in which the sorbent is contained in a propylene membrane envelope, and (b) separation and detection by capillary electrophoresis (CE). Under optimized conditions, response is linear in the range between 50 and 300 ng mL^?1 (with a correlation coefficient of 0.9989), relative standard deviations range from 4 to 8 %, the detection limit for OTA in urine is 11.2 ng mL^?1 (with a quantification limits of 32.5 ng mL^?1) which is lower than those of previously reported methods for solid-phase extraction combined with CE. The recoveries of OTA from urine spiked at levels of 50, 150 and 300 ng mL^?1 ranged from 93 to 97 %.

An automated headspace solid-phase microextraction followed by gas chromatography–mass spectrometry method to determine macrocyclic musk fragrances in wastewater samples

A fully automated method has been developed for determining eight macrocyclic musk fragrances in wastewater samples. The method is based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography–mass spectrometry (GC-MS). Five different fibres (PDMS 7 μm, PDMS 30 μm, PDMS 100 μm, PDMS/DVB 65 μm and PA 85 μm) were tested. The best conditions were achieved when a PDMS/DVB 65 μm fibre was exposed for 45 min in the headspace of 10 mL water samples at 100 °C. Method detection limits were found in the low ng L^?1 range between 0.75 and 5 ng L^?1 depending on the target analytes. Moreover, under optimized conditions, the method gave good levels of intra-day and inter-day repeatabilities in wastewater samples with relative standard deviations (n?=?5, 1,000 ng L^?1) less than 9 and 14 %, respectively. The applicability of the method was tested with influent and effluent urban wastewater samples from different wastewater treatment plants (WWTPs). The analysis of influent urban wastewater revealed the presence of most of the target macrocyclic musks with, most notably, the maximum concentration of ambrettolide being obtained in WWTP A (4.36 μg L^?1) and WWTP B (12.29 μg L^?1), respectively. The analysis of effluent urban wastewater showed a decrease in target analyte concentrations, with exaltone and ambrettolide being the most abundant compounds with concentrations varying between below method quantification limit (<MQL) and 2.46 μg L^?1.