Simultaneous Determination of Fluvoxamine and Its Metabolites in Human Liver Microsomes by High‐Performance Liquid Chromatography with Solid‐Phase Extraction

Abstract

A simple and sensitive high‐performance liquid chromatography method was developed for the simultaneous quantitative determination of fluvoxamine and its two metabolites, fluvoxamino alcohol and fluvoxamino acid, in human liver microsomes. Chromatographic separation was achieved with a Grand‐pak C4‐5 column using a mobile phase at pH 2.5 of 0.5% KH₂PO₄‐acetonitrile (75:25, v/v). Analysis involved a solid‐phase extraction with an Oasis HLB cartridge, which gave high extraction recovery (>92.8%) with good selectivity. The lower limit of quantification of this assay was 78.6 nM for fluvoxamine and fluvoxamino acid, and 82.2 nM for fluvoxamino alcohol, respectively. The coefficient of variation of intra‐ and interday assays was less than 5.8% and accuracy was within 5.3% for all analytes (concentration range 78.6 nM–2.36 µM for fluvoxamine and fluvoxamino acid, and 82.2 nM–2.47 µM for fluvoxamino alcohol, respectively). This method is applicable for accurate and simultaneous determination of oxidative metabolites of fluvoxamine by human liver microsomes.     

Carbon Nanofibers as Solid‐Phase Extraction Adsorbent for the Preconcentration of Trace Rare Earth Elements and Their Determination by Inductively Coupled Plasma Mass Spectrometry

Abstract

Systematic investigations were carried out into the sorption of rare earth elements (REEs) on carbon nonofibers (CNFs) by inductively coupled plasma mass spectrometry (ICP‐MS). The experimental parameters for preconcentration of REEs, such as pH, sample flow rate and volume, eluent concentration, and interfering ions on preconcentration of REEs have been examined in detail. The studied metal ions can be adsorbed quantitatively on CNFs in a pH range from 2.0 to 5.0, and then eluted completely with 0.5 mol l^?1 HNO₃. Based on the above facts, a novel method using a microcolumn packed with carbon nanofibers as an adsorption material was developed for the separation and preconcentration of REEs prior to their determination by ICP‐MS. The proposed method has been successfully applied to the determination of light (La), medium (Eu and Gd) and heavy (Yb) rare earth elements in real sample with the recovery more than 90%. In order to validate this method, two certified reference materials of tea leaves (GBW 07605) and mussel (GBW 08571) were analyzed, and the determined values are in good agreement with the certified values.     

Determination of Chlorophenols and Alkylphenols in Water and Juice by Solid Phase Derivative Extraction and Gas Chromatography–Mass Spectrometry

A solid phase derivative extraction method using acetic anhydride was developed for the determination of chlorophenols and alkylphenols in water and fruit juice by gas chromatography–mass spectrometry (GC–MS). The quantitative extraction was performed by passing 100 mL of sample prepared in 0.1 mol L^?1 sodium hydroxide through a column packed with 500 mg of a strong anion-exchange resin at a flow rate of 0.75 mL min^?1. The retained phenols were quantitatively derivatized in the column by the introduction of 0.25 mL of acetic anhydride. The derivatized phenols were eluted with 3.0 mL of hexane and the effluent was dried under nitrogen. The final volume was diluted to fifty microliters with hexane and analyzed by GC–MS. Under the optimum conditions, preconcentration factors of 2000, limits of detection between 0.005 and 1.796 µg L^?1, and relative standard deviations of 2.1% to 6.7% were obtained. The method was successfully applied to wastewater and fruit juice and the recoveries of phenols were between 76% and 111%.     

Determination of Ginsenoside Rg2 in Rat Plasma by High‐Performance Liquid Chromatography–Mass Spectrometry after Solid‐Phase Extraction

Abstract

A sensitive liquid chromatography‐mass spectrometric (LC/MS) method for the quantification of ginsenoside Rg2 (Rg2) in rat plasma was developed after solid‐phase extraction (SPE). Chromatographic separation was achieved on a reversed‐phase Kromasil C₁₈ column with the mobile phase of acetonitrile‐ammonium chloride (500 µM/L) and step gradient elution resulted in a total run time of about 9 min. The analytes were detected using electrospray negative ionization mass spectrometry in the selected ion monitoring (SIM) mode. A good linear relationship was obtained in the concentration range (5–2500 ng/mL) (r=0.9999). Limit of quantification (LOQ) was 5 ng/mL and the limit of detection (LOD) was 2 ng/mL using 100 µL plasma sample. Average recoveries ranged from 72.43–84.73% in plasma at the concentrations of 20, 200, and 2000 ng/mL. Intra‐ and interday coefficients of variation for the assay were 4.93–10.87% and 4.06–7.84%, respectively. The method was successfully applied to the analysis of ginsenoside Rg2 in rat plasma. The applicability of this assay was examined in a preliminary pharmacokinetic study of ginsenoside Rg2 in rats.     

Simultaneous Spectrofluorimetric Determination of Paracetamol and Caffeine in Pharmaceutical Preparations in Solid‐Phase Using Partial Least Squares Multivariate Calibration

Abstract

Partial least‐squares algorithm (PLS)‐1 was used for the solid‐phase spectrofluorimetric determination of paracetamol (PA) and caffeine (CF) in pharmaceutical formulations. In despite of the closely overlapping spectral bands, the method allows the simultaneous quantification and sample preparation prior to analysis is not required. The calibration set consisted of 96 samples with 100–400 mg/g^?1 PA plus 10–65 mg/g^?1 CF; another set of 25 samples was used for external validation. Agreement between predicted and experimental concentrations was fair (r=0.993 and 0.964 for PA and CF models). Prediction performance was evaluated in terms of the coefficient of variability (CV), relative predictive determination (RPD), and ratio error range (RER). The PLS‐1 model was used for the determination of PA and CF in pharmaceutical formulations.     

Determination of Cotinine in Urine by Molecularly Imprinted Polymer Solid Phase and Liquid–Liquid Extraction Coupled with Gas Chromatography

A comparison between molecularly imprinted solid phase extraction (MISPE) and liquid–liquid extraction (LLE) was performed for cotinine in human urine followed by gas chromatography analysis. The molecularly imprinted polymer (MIP) was synthesized via bulk methodology employing cotinine, methacrylic acid, and ethylene glycol dimethacrylate as template, functional monomer, and cross-linker, respectively. Both methods were validated with good precision and accuracy. The LLE method (limit of quantification = 10 nanograms per milliliter) was slightly more sensitive than the MISPE (limit of quantification = 15 nanograms per milliliter) procedure, but both methods were able to determine cotinine at typical concentrations in urine. An important advantage of the molecularly imprinted polymer approach was its ability to be reused up to at least 100 times. Other advantages of the MISPE include simple manipulation, low solvent consumption, and low worker exposure.     

Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Preconcentration of Some Trace Metal Ions from Drinking and Tap Water Samples by Sorption on Amberlite XAD‐4 after Complexation with Di‐2‐Pyridyl Ketone Thiosemicarbazone

Abstract

A method was established for enrichment of trace levels of Co(II), Ni(II), Fe(II), and Cu(II) ions in aqueous solutions. These metals were quantitatively retained on an Amberlite XAD‐4 column, after complexation with di‐2‐pyridyl ketone thiosemicarbazone (DPKT). After elution with 1 M HNO₃ in acetone, concentration of metals were measured by atomic absorption spectrometry. The effect of major cations of drinking and tap water samples on the sorption of metal ions also were investigated. The amount of the analyte metal ions determined after preconcentration was basically in agreement with the added amount.

The developed method was used for the determination of trace amounts of metal ions in drinking and tap water samples with good results, such as relative standart deviations below 2% (N=6) and recoveries greater than >95%.     

Matrix Effects in Determination of Triazines and Atrazine Metabolite in Waters with Solid‐Phase Extraction Followed by High Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry

Abstract

A method for determination of selected triazines in waters was developed. The method includes off‐line solid‐phase extraction of triazines on the polymeric sorbent, high‐pressure liquid chromatographic separation, and determination with tandem mass spectrometer. The linearity extended from 0.008 to 1.000 µg L^?1 for each triazine while the limits of detection ranged from 0.001 to 0.004 µg L^?1. Solid‐phase extraction recoveries from ground, surface, and waste waters ranged from 64% to 96%. Possible water interferences were investigated. Natural humic acids and salts did not influence the ionization process. The presence of humic acids did not affect binding ability of the solid‐phase sorbent, while the presence of salts increased the extraction efficiency by approximately 10%.     

Dispersive Liquid–Liquid Microextraction and Micro-Solid Phase Extraction for the Rapid Determination of Metals in Food and Environmental Waters

A rapid and novel two-step dispersive liquid–liquid microextraction and dispersive micro-solid phase extraction method was established for the separation and enrichment of trace cadmium, nickel, and copper in food and environmental water prior to determination by inductively coupled plasma-mass spectrometry (ICP-MS). In the first microextraction step, carbon tetrachloride was employed to extract metal-diethyldithiocarbamate chelates from aqueous solution with ultrasound. In the following step, Fe₃O₄ magnetic nanoparticles were added and used to collect the analytes in the organic solvent. The sample pH, type and volume of extraction solvent, mass of magnetic nanoparticles, concentration of the chelating agent, concentration of sodium chloride, and sonication time were optimized. The linear dynamic range was from 0.01 to 20 micrograms per liter with correlation coefficients between 0.9990 and 0.9992. Enrichment factors were 78, 79, and 81 for cadmium, nickel, and copper, respectively. The limits of detection for cadmium, nickel, and copper were 0.007, 0.009, and 0.017 micrograms per liter, with relative standard deviations from 1.1 to 2.6 percent. The developed method was validated by the determination of cadmium, nickel, and copper in rice and mussel certified reference materials, food, and environmental water with satisfactory results.     

Determination of Cd and Pb in Honey by SF‐ICP‐MS: Validation Figures and Uncertainty of Results

Abstract

A method based on microwave‐assisted acid digestion of honey and quantification of Cd and Pb by Sector Field Inductively Coupled Plasma Mass Spectrometry was in‐house validated and the combined uncertainty was estimated according to the Eurachem/Citac Guide. Limits of detection and quantification were 0.07 and 0.20 ng g^?1 for Cd, and 0.70 and 2.10 ng g^?1 for Pb; recovery was 103.9% for Cd and 98.5% for Pb; repeatability was 10.7% for Cd and 18.5% for Pb; within‐laboratory reproducibility was 15.2% for Cd and 21.4% for Pb. Relative combined uncertainty in honey was 15% for Cd and 22% for Pb, with the main contribution coming from the within‐laboratory reproducibility. The method showed robustness when subjected to different working conditions and when applied to various Italian honeys. Cadmium content ranged 0.2–1.37 ng g^?1 and Pb 4.6–30.5 ng g^?1 in flower honeys, while the highest concentrations were presented by honeydew honeys.     

Diesel-Range Organics Extraction and Determination in Environmental Samples by Gas Chromatography‒Mass Spectrometry: Headspace Solid Phase Microextraction vs. Solvent Extraction

An accurate and sensitive analytical method for the determination of diesel-range organics (DRO) is the basis to monitoring and soil remediation studies. In the present work, the determination of DRO in different water and soil samples was optimized. Solvent extraction procedures, i.e. ultrasonic assisted extraction (USAE) (for water samples) and accelerated solvent extraction (ASE) (for soil samples), and a solvent-free procedure, headspace solid phase microextraction (HS-SPME), were optimized to achieve the highest recoveries for the simultaneous determination of all DRO. One hour of USAE for water samples and ASE of soil samples at 100°C, 2000 psi and two extraction cycles lead to analytical recoveries of 70?100%. Using HS-SPME, 30 min of incubation at 90°C were sufficient to achieve analytical recoveries up to 90% for water and soil samples. HS-SPME enables higher preconcentration factors, which makes this method more appropriate for samples with trace DRO concentrations.     

Determination of Chlorfenvinphos in Soils by Microwave‐Assisted Extraction and Stripping Voltammetry with an Ultramicroelectrode

Abstract

A methodology for the determination of the pesticide chlorfenvinphos by microwave‐assisted solvent extraction and square‐wave cathodic stripping voltammetry at a mercury film ultramicroelectrode in soil samples is proposed. Optimization of microwave solvent extraction performed with two soils, selected for having significantly different properties, indicated that the optimum solvent for extracting chlorfenvinphos is hexane‐acetone (1∶1, v/v). The voltammetric procedure is based on controlled adsorptive accumulation of the insecticide at the potential of?0.60 V (vs. Ag/AgCl) in the presence of Britton‐Robinson buffer (pH 6.2). The detection limit obtained for a 10 s collection time was 3.0×10^?8 mol l^?1. The validity of the developed methodology was assessed by recovery experiments at the 0.100 µg g^?1 level. The average recoveries and standard deviations for the global procedure reached by MASE‐square‐wave voltammetry were 90.2±2.8% and 92.1±3.4% for type I (soil rich in organic matter) and type II (sandy soil) samples, respectively. These results are in accordance to the expected values which show that the method has a good accuracy.     

Determination of Microcystins in Cyanobacteria by Supercritical Fluid Extraction and Liquid Chromatography‐Tandem Mass Spectrometry

Abstract

A method for the detection of microcystins (microcystin LR, RR, and YR) in cyanobacteria by supercritical fluid extraction (SFE) and liquid chromatography‐mass spectrometry (LC/MS) has been developed. Supercritical fluids for the analytical extraction of nonvolatile, higher molecular weight compound, and microcystins from cyanobacteria were investigated. The microcystins included in this study are sparsely soluble in neat supercritical fluid CO₂. However, the microcystins was successfully extracted with a ternary mixture (90% CO₂, 9.5% methanol, 0.5% water) at 40°C and 250 atm. The polar carbon dioxide‐aqueous methanol fluid system gave high extraction efficiency for the extraction of the polar microcystins from cyanobacteria. The microcystins were determined by liquid chromatography‐tandem mass spectrometry (LC/MS/MS).     

Development of a Solid‐Phase Extraction‐Enzyme‐Linked Immunosorbent Assay Method with a New Sorbent of Multiwall Carbon Nanotube for the Determination of Estrone in Water

Abstract

A sensitive solid‐phase extraction‐enzyme‐linked immunosorbent assay (SPE‐ELISA) method was developed to analyze the estrone in environmental water. A new SPE sorbent of the multiwall carbon nanotube was tested and proved to have similar adsorbability for estrone comparing to the commercial C₁₈ SPE. A specific polyclonal antibody for estrone (A‐E1) and a broad‐spectrum antibody for estrone, estradiol and estriol (A‐E2) were produced. For A‐E1, the limit detection of estrone was 0.04 µg/l and for A‐E2 were 0.07, 0.04 and 0.2 µg/l of estrone, estradiol and estriol, respectively. Different river water samples were analyzed by ELISA and HPLC method.     

Sorption–Atomic Absorption Determination of Trace Elements in Natural Waters Using Simultaneous Atomization of a Solid Concentrate and Suspended Matter

A sorption–atomic absorption technique with dynamic preconcentration on DETATA adsorbents in a microcolumn crucible followed by the direct atomization of a solid matrix (concentrate + suspended matter) was used to determine the total dissolved and suspended Cd, Pb, and Tl (El_dis+ El_susp) in natural waters. The detection limits were 1–3 ng/L for Cd and 5–30 ng/L for Pb and Tl. The results of the sorption–filtration atomic absorption determination of the total dissolved and suspended elements can provide extra information for the speciation analysis of waters.     

Solid‐Phase Microextraction Followed by High‐Performance Liquid Chromatography with Fluorimetric and UV Detection for the Determination of Polycyclic Aromatic Hydrocarbons in Water

Abstract

We have developed a solid‐phase microextraction procedure for polycyclic aromatic hydrocarbons. A simplex experimental design was employed to optimize the process. A polydimethylsiloxane/divinylbenzene fiber was selected. The optimum conditions were: an extraction step in the immersion mode, over a period of 60 min at 70°C using high‐speed stirring, and an 8 min desorption step using acetonitrile (90 µl). Linear relationships were obtained for all compounds, except for naphthalene. Our method showed a good precision and accuracy with a detection limit between 0.005 and 0.306 µg l^?1. Our method was used to detect PAHs in real water samples.     

Determination of Chlorophenols in Wastewater with Methyl Chloroformate Derivatization,Solid Phase Extraction,and Gas Chromatography–Mass Spectrometry

The determination of chlorophenols in wastewater with methyl chloroformate derivatization, solid phase extraction, and gas chromatography–mass spectrometry is reported. In order to employ this combined solid phase derivative extraction method, quantitative extraction was performed by the introduction of 100 mL of sample in 1.0 mol L^?1 sodium hydroxide into a column containing 500 mg of packed resin at a flow rate of 1.0 mL/min. The chlorophenols were retained and derivatized quantitatively in the column by the introduction of 0.25 mL of methyl chloroformate. The derivatized analytes were eluted with 5.0 mL of hexane before the effluent was dried under a stream of nitrogen. The dried solution was diluted to a volume of 50 µL with hexane followed by analysis by gas chromatography–mass spectrometry. The preconcentration parameters were optimized and under these conditions: limits of detection from 0.010 to 0.423 µg L^?1, a preconcentration factor of 2500, and precision values from 4.8 to 7.7% as the relative standard deviation were obtained. The method was employed for the analysis of water samples and the recoveries of the analytes were between 76 and 103%.