Comparison of standard and reaction cell inductively coupled plasma mass spectrometry in the determination of chromium and selenium species by HPLC-ICP-MS

Elemental speciation is becoming a common analytical procedure for geochemical investigations. The various redox species of environmentally relevant metals can have vastly different biogeochemical properties, including sorption, solubility, bioavailability, and toxicity. The use of high performance liquid chromatography (HPLC) coupled to elemental specific detectors, such as inductively coupled plasma mass spectrometry (ICP-MS), has become one of the most important speciation methods employed. This is due to the separation versatility of HPLC and the sensitive and selective detection capabilities of ICP-MS. The current study compares standard mode ICP-MS to recently developed reaction cell (RC) ICP-MS, which has the ability to remove or reduce many common polyatomic interferences that can limit the ability of ICP-MS to quantitate certain analytes in complex matrices. Determination of chromium and selenium redox species is achieved using ion-exchange chromatography with elemental detection by standard and RC-ICP-MS, using various chromium and selenium isotopes. In this study, method performance and detection limits for the various permutations of the method (isotope monitored or ICP-MS detection mode) were found to be comparable and generally less than 1 μg L⁻¹. The method was tested on synthetic laboratory samples, surface water, groundwater, and municipal tap water matrices.     

Monitoring of pesticides in surface water: Off-line SPE followed by HPLC with UV detection and confirmatory analysis by mass spectrometry

Summary The presence of 16 of the most widely used pesticides in southern Italy (plus atrazine, the use of which is currently restricted in Europe) has been monitored in ten surface waters of the Calabria Region. The analytes were extracted from water by off-line solid-phase extraction with a Carbograph cartridge. Base-neutral, and acid pesticides were then isolated by differential elution. Analyte fractionation and quantification were performed by liquid chromatography (HPLC) with UV detection. Recoveries of analytes from 0.5 L river water (200 ngL⁻¹ spike level) were ≥84%. Confirmatory analysis was performed by HPLC coupled with ion-spray mass spectrometry (LC-ESI-MS).     

Bioanalytical methods for determination of tamoxifen and its phase I metabolites: a review

The selective estrogen receptor modulator tamoxifen is used in the treatment of early and advanced breast cancer and in selected cases for breast cancer prevention in high-risk subjects. The cytochrome P450 enzyme system and flavin-containing monooxygenase are responsible for the extensive metabolism of tamoxifen into several phase I metabolites that vary in toxicity and potencies towards estrogen receptor (ER) alpha and ER beta.An extensive overview of publications on the determination of tamoxifen and its phase I metabolites in biological samples is presented. In these publications techniques were used such as capillary electrophoresis, liquid, gas and thin layer chromatography coupled with various detection techniques (mass spectrometry, ultraviolet or fluorescence detection, liquid scintillation counting and nuclear magnetic resonance spectroscopy). A trend is seen towards the use of liquid chromatography coupled to mass spectrometry (LC-MS). State-of-the-art LC-MS equipment allowed for identification of unknown metabolites and quantification of known metabolites reaching lower limit of quantification levels in the sub pg mL⁻¹ range. Although tamoxifen is also metabolized into phase II metabolites, the number of publications reporting on phase II metabolism of tamoxifen is scarce. Therefore the focus of this review is on phase I metabolites of tamoxifen.We conclude that in the past decades tamoxifen metabolism has been studied extensively and numerous metabolites have been identified. Assays have been developed for both the identification and quantification of tamoxifen and its metabolites in an array of biological samples. This review can be used as a resource for method transfer and development of analytical methods used to support pharmacokinetic and pharmacodynamic studies of tamoxifen and its phase I metabolites.     

Development and validation of a reversed‐phase high‐performance liquid chromatographic method with solid‐phase extraction for the quantification of hydrochlorothiazide in ex vivo permeation studies

Hydrochlorothiazide (HCT) is a diuretic used to treat hypertension. In order to study its intestinal permeation behavior applying an ex vivo methodology, a rapid, sensitive and selective reversed‐phase liquid chromatography (RP‐HPLC) method coupled with UV detection (RP‐HPLC UV) was developed for the analysis of HCT in TC199 culture medium used as mucosal and serosal solutions in the everted rat intestinal sac model. Also, analytical procedures for the quantification of HCT by RP‐HPLC with UV detection required a sample preparation step by solid‐phase extraction. The method was validated in the concentration range of 8.05 × 10⁻⁷ to 3.22 × 10⁻⁵ m for HCT. Chromatographic parameters, namely carry‐over, lower limit of quantification (1.4491 × 10⁻⁷ m ), limit of detection (3.8325 × 10⁻⁸ m ), selectivity, inter‐ and intraday precision and extraction recovery, were determined and found to be adequate for the intended purposes. The validated method was successfully used for permeability assays across rat intestinal epithelium applying the ex vivo everted rat gut sac methodology to study the permeation behavior of HCT.     

Determination of organophosphate pesticides in sea and surface water with ultrasound-assisted dispersive liquid–liquid micro-extraction coupled to GC-MS/MS analysis

A sensitive enrichment method for the detection and quantification of 20 organophosphate pesticides in sea water and surface water was improved and validated. The compounds were extracted using ultrasound-assisted dispersive liquid–liquid microextraction and were analysed with an optimised Gas Chromatography - Tandem Quadrupole Mass Spectrometry (GC-MS/MS) method. Calibrations and validations were conducted for spiked local pond and Baltic Sea water. Recoveries of the organophosphate compounds from the different matrices ranged from about 25% to 70% and from 30% to 130% for pond and sea water, respectively. Obtained limit of detection (LoD) for both matrices was about 3 ng L^?1 and the limit of quantification (k = 3) was 12 and 7 ng L^?1 for pond and sea water, respectively. Valid extractability at the LoD level could be proven.     

HPLC-UV analytical method for determination of pizotifen after in vitro transdermal diffusion studies

Pizotifen malate is an antihistamine and serotonin inhibitor used in the preventive treatment of migraine and eating disorders. A simple, rapid, accurate and precise high‐performance liquid chromatography (HPLC) method involving ultraviolet detection was validated for the quantitative analysis of pizotifen malate in samples from in vitro transdermal diffusion studies. The method was validated for specificity, linearity, accuracy, precision, limit of detection, limit of quantification and robustness. Drug stability in the solution was also determined under different conditions. Separation was carried out using a 250 × 4.0 mm Kromasil^® C₁₈ column at room temperature. The detector response, fitted at 254 nm, was found to be linear in a concentration range between 0.24 and 24.0 µg/mL. The limit of detection was 0.02 µg/mL and the limit of quantification was 0.07 µg/mL. Finally, in vitro transdermal diffusion of pizotifen malate was characterized using the validated HPLC method. Copyright © 2011 John Wiley & Sons, Ltd.     

Simple and Rapid Determination of Cordycepin in Cordyceps militaris Fruiting Bodies by Quantitative Nuclear Magnetic Resonance Spectroscopy

The major compound in Cordyceps militaris (C. militaris), cordycepin, has been known to have a variety of pharmacological properties. The cordycepin concentration in artificially cultivated fruiting bodies of C. militaris was determined using quantitative ¹H nuclear magnetic resonance spectroscopy (NMR). The results were compared with a high performance liquid chromatography (HPLC) method. There were no statistically significant differences in the cordycepin concentration by the two methods. Validation of each method was performed in terms of linearity, limit of detection, limit of quantification, intra- and inter-day precision, repeatability, stability, and accuracy. Better inter-day precision, repeatability, stability, and accuracy were obtained by NMR than by HPLC. These results show that NMR is an alternative to HPLC for the determination of cordycepin in C. militaris fruiting bodies.     

Dabsyl chloride derivatisation of melamine followed by high-performance liquid chromatography determination in water samples

A new and sensitive precolumn derivatisation with dabsyl chloride was developed for the analysis of melamine in water samples by high-performance liquid chromatography (HPLC) with visible detection. Derivatisation with dabsyl chloride leads to improving sensitivity and hydrophobicity of melamine. Under optimum conditions of derivatisation and microextraction, the method yielded a linear calibration curve ranging from 10 to 2000 µg L^?1 with a determination coefficient (R²) of 0.9952. Limit of detection (LOD) and limit of quantification (LOQ) were 2.0 and 6.0 µg L^?1, respectively. The relative standard deviation per cent (RSD%) for intraday and inter-day extraction and determination at 20 and 200 µg L^?1 levels of melamine was less than 8.2% (n = 6). Finally, the proposed method was successfully applied for the determination of melamine in different water samples and satisfactory results were obtained (relative recovery ≥91%).     

Determination and Validation of an LC Method for Fluvoxamine in Tablets

A new, simple, rapid and specific reversed-phase high-performance liquid chromatography (HPLC) method was developed and validated for the determination of fluvoxamine in pharmaceutical dosage forms. The HPLC separation was achieved on a C₁₈ μ-Bondapack column (250 mm × 4.6 mm) using a mobile phase of acetonitrile–water (80:20, v/v) at a flow rate of 1 mL min⁻¹. Proposed method is based on the derivatization of fluvoxamine with 1,2-naphthoquinone-4-sulphonic acid sodium salt (NQS) in borate buffer of pH 8.5 to yield a orange product. The HPLC method is based on measurement of the derivatized product using UV-visible absorbance detection at 450 nm. The method was validated for specificity, linearity, precision, accuracy, robustness. The degree of linearity of the calibration curves, the percent recoveries of fluvoxamine, the limit of detection and quantification, for the HPLC method were determined. The assay was linear over the concentration range of 45–145 ng mL⁻¹ (r = 0.9999). Limit of detection and quantification for fluvoxamine were 15 and 50 ng mL⁻¹, respectively. The results of the developed procedure (proposed method) for fluvoxamine content in tablets were compared with those by the official method. The method was found to be simple, specific, precise, accurate, reproducible and robust.     

Ionic liquid/Ammonium Sulfate Aqueous Two-phase System Coupled with HPLC Extraction of Sulfadimidine in Real Environmental Water Samples

Room temperature ionic liquids are novel solvents with a rather specific blend of physical and solution properties that make them of interest for applications in separation science. In this study, a green, simple, and sensitive sample pretreatment procedure coupled with high-performance liquid chromatography (HPLC) was developed for the analysis of sulfadimidine (SM2) that exploits an aqueous two-phase system based on 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄) and ammonium sulfate ((NH₄)₂SO₄) using a liquid?Cliquid extraction technique in real environmental water samples. The influences of the concentration of (NH₄)₂SO₄, pH value, temperature, and concentration of SM2 on the extraction efficiency of SM2 were determined. Under optimal conditions, the extraction efficiencies of SM2 were over 93.7%. Calibration curves yielded good linearity (R ² = 0.9998) over the range 3?C240 ng mL^?1, and the limit of detection and limit of quantification for analytes were 0.9 ng mL^?1 and 3 ng mL^?1, respectively. The proposed method was successfully applied to the quantification of SM2 in water samples and recoveries were in the range of 101.2?C107%.     

Quantitative analysis of boldine alkaloid in natural extracts by cyclic voltammetry at a liquid-liquid interface and validation of the method by comparison with high performance liquid chromatography

The quantitative determination of boldine alkaloid in boldo leaf extracts by employing cyclic voltammetry, at a liquid/liquid interface as well as the validation of this methodology against the reference method, high performance liquid chromatography (HPLC), are reported in the present paper. The voltammetric analysis was performed successfully and economically using two kinds of liquid/liquid interfaces: water/1,2-dicholoroethane and water/PVC (polyvinyl chloride)-gelled 1,2-dichloroethane. Linear calibration curves in the concentration range of 1.04 × 10⁻⁵ mol L⁻¹ to 5.19 × 10⁻⁴ mol L⁻¹ were obtained with a detection limit equal to (6.1 ± 0.7) × 10⁻⁵ mol L⁻¹ and the quantitative determination of this alkaloid, in complex matrixes such as boldo leaf extracts, by the electrochemical technique proposed was found to be equal to the values obtained using the standard HPLC method. The validation analysis of this methodology against HPLC demonstrated that accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ), specificity and precision are acceptable. The electroanalytical technique proposed is economical and selective, involves simple equipment and can be applied for the quantitative determination of boldine alkaloid in complex matrixes such as leaf extracts without special drug separation. Moreover, cyclic voltammetry (CV) experiments applied at the liquid/liquid interface under different experimental conditions allowed us to study the transfer mechanism of boldine, and determine a value of pK_a^w = 6.90 for protonated boldine, from the variation of voltammetric peak current with pH.     

Detection challenges in quantitative polymer analysis by liquid chromatography

Accurate quantification of polymer distributions is one of the main challenges in polymer analysis by liquid chromatography. The response of contemporary detectors is typically influenced by compositional features such as molecular weight, chain composition, end groups, and branching. This renders the accurate quantification of complex polymers of which there are no standards available, extremely challenging. Moreover, any (programmed) change in mobile‐phase composition may further limit the applicability of detection techniques. Current methods often rely on refractive index detection, which is not accurate when dealing with complex samples as the refractive‐index increment is often unknown. We review current and emerging detection methods in liquid chromatography with the aim of identifying detectors, which can be applied to the quantitative analysis of complex polymers.     

Concurrent detection of cabozantinib as an anticancer agent and its major metabolites in human serum using fluorescence-coupled micellar liquid chromatography

A novel, highly sensitive, simple, and rapid strategy was designed and developed for simultaneous determination of cabozantinib (CBZ) as an anticancer agent and its main metabolites including monohydroxy sulfate (EXEL-1646), N-oxide (EXEL-5162(, amide cleavage product (EXEL-5366), and 6-desmethyl amide cleavage product sulfate) EXEL-1644). Measurements were done through a micellar liquid chromatography (MLC) method coupled with fluorescence detection. The high-performance liquid chromatography (HPLC) was performed using a Kinetex C18 100 Å column as well as acetonitrile, cetyltrimethylammonium bromide (CTAB; 0.2 mol.L^?1), and tris buffer (pH 8.5) solutions as the mobile phase at a 40:50:10 (v/v) ratio. The method’s linearity (20 to 700 ng.mL^?1), limit of detection (LOD; 2.11 to 3.69 ng.mL^?1), limit of quantification (LOQ; 20 to 30 ng.mL^?1), intra- and inter-day precisions (RSD < 4.00%), selectivity, recovery, and robustness were fully evaluated. According to the obtained results, the developed method can be used for simple and rapid (~35 min) quantification of CBZ as an anticancer drug and its major metabolites in human serum samples with high sensitivity and low cost.     

Quantitative determination of rifampicin in aquatic products by stable isotope-dilution high liquid chromatography–tandem mass spectrometry

Rifampicin is a semi-synthetic broad-spectrum antibiotic obtained from rifamycin B. It is one of the most effective first-line antituberculosis drugs and is widely used in clinical practice. In the present study, we describe a rapid and sensitive method for the determination of rifampin in aquatic products by stable isotope-dilution high liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Samples were extracted with the acetonitrile, degreased by hexane, and then concentrated by nitrogen blowing. After separation using a C₁₈ column with a mixture of acetonitrile and water as mobile phase, it was determined by HPLC–MS/MS using the stable isotope-dilution calibration method. The performance of our method was validated. The limit of detection was 0.25 μg kg⁻¹ and the limit of quantification was 0.5 μg kg⁻¹. At the three spiked levels of 0.5, 1.0 and 5.0 μg kg⁻¹, the average recoveries of rifampicin in different aquatic products were between 75.28 and 107.6%, and the relative standard deviation ranged from 0.81 to 13.23%. This method was successfully applied for the determination of rifampin in different kinds of aquatic products and rifampicin residue was found in aquatic products obtained from markets in Beijing, China.     

Characterization of the Chemical Profile of Euphorbia Species from Turkey by Gas Chromatography–Mass Spectrometry (GC-MS), Liquid Chromatography–Tandem Mass Spectrometry (LC-MS/MS), and Liquid Chromatography–Ion Trap–Time-of-Flight–Mass Spectrometry (LC-IT-TOF-MS) and Chemometric Analysis†

The Euphorbiaceae family comprises of about 300 genera and 5000 species primarily distributed in America and tropical Africa. The Euphorbia genus is represented by 105 species and locally named as “Sütle?en” and “Xa?îl” in Turkey. The present study aimed to determine the chemical constituents of E. aleppica, E. eriophora, E. macroclada, E. grisophylla, E. seguieriana subsp. seguieriana, E. craspedia, E. denticulata, E. falcata, and E. fistulosa, and classify them by utilizing the chemometric techniques of principal component analysis (PCA) and hierarchical cluster analysis (HCA). Linoleic acid, 17-tetratriacontane, palmitic acid, and hexatriacontane were the major fatty acids from the gas chromatography–mass spectrometry (GC/MS) analyses. Characterization of 268 constituents of the studied species was achieved by liquid chromatography–ion trap–time-of-flight–mass spectrometry (LC-IT-TOF-MS). Furthermore, a new liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous quantitative determination of 11 compounds (quinic acid, protocatechuic acid, rutin, hesperidin, eugenol, p-coumaric acid, piceatannol, scopoletin, dl-kavain, chrysophanic acid, and resiniferatoxin) in these species. The developed method was validated for the linearity, limit of detection, limit of quantification, repeatability, and recovery.     

HPLC Determination and Pharmacokinetic Study of Indapamide in Human Whole Blood

A rapid and sensitive HPLC method for the quantification of indapamide in human whole blood is described. The procedure involves liquid–liquid extraction of human whole blood with methyl tertiarybutyl ether coupled with reversed-phase HPLC and UV detection. Separation was performed on a YMC^® ODS-A reverse column (5 µm particle size, 4.6×150 mm i.d.). The mobile phase was composed of acetonitrile - 2-propanol ?0.1 triethylamine in water (adjusting to pH 3.75 with 85% phosphoric acid) (35:5:60, v/v/v). The linear concentration range for indapamide was 5.0–500 ngmL^?1. The lower limit of quantification (LLOQ) was 5.0 ngmL^?1 for indapamide. Intra- and inter-assay RSD ranged from 2.36% to 4.53% and 1.68% to 8.01%, respectively. The sensitivity and precision were sufficient for determination of whole blood concentrations after therapeutic administration of both drugs and the method can be used for the estimation of pharmacokinetic parameters.     

Comparative Evaluation of CE and HPLC for Determination of Cotinine in Human Urine

Two rapid and popular methods—capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) have been compared for analysis of cotinine in human urine. Cotinine was analyzed in less than 7 min, with detection limits of 5 and 3.2 ng mL⁻¹ for CE and HPLC, respectively. The performance of the methods was evaluated in terms of sensitivity, specificity, precision, accuracy, and limits of detection and quantification. Calibration plots were linear in the range 50–4,000 ng mL⁻¹, at least, and mean recoveries were satisfactory for both techniques. The methods were successfully used for quantification of cotinine in urine.     

In‐situ preparation of porous monolithic polymer inside hollow fiber as a micro‐solid phase extraction device for glucocorticoids in cosmetics

Glucocorticoids have a certain whitening effect on the skin. However, frequent and long‐term use of cosmetics including glucocorticoids is harmful to health. Herein, we proposed a novel micro‐solid phase extraction method for the detection of prednisolone acetate, prednisone, and prednisolone in cosmetics coupled with high‐performance liquid chromatography. In this method, porous monolithic polymer micro‐extraction bars were prepared by “one‐step, one‐pot” in situ photopolymerization combined with sacrificial support in hollow fiber under water atmosphere. The crucial factors such as pH of sample solution, extraction, and elution times that influence micro‐extraction were optimized and found to be 9.0, 2 h, and 32 min, respectively. Under the optimum experimental conditions, the linear range of the calibration curves were from 5.0 to 2000 µg/L with correlation coefficients (R²) between 0.9922 and 0.9996. The limit of detection and limit of quantification were 1.5 µg/L and 5.0 µg/L, respectively, and the recoveries were found to be in range of 69.0–113.3%. The analysis of precision for intraday and interday were less than 10.40 and 10.59%. The device has been successfully achieved photopolymerization under water atmosphere. The results indicated that this method is simple, accurate, and satisfactory for the pretreatment and determination of glucocorticoids in complex cosmetics samples.     

Determination of theophylline in serum by high performance liquid chromatography/mass spectrometry with atmospheric pressure chemical-ionization (APCI HPLC/MS)

 A method for the determination of theophylline (TH), without derivatization, in serum by isotope dilution mass spectrometry using labelled [1, 3-¹⁵N₂-2-¹³C]theophylline (LTH) as internal standard is described. After deproteinization, the analyte is directly injected into a high performance liquid chromatography – mass spectrometer operating with atmospheric-pressure chemical-ionization (APCI HPLC/MS). The concentrations of TH in sera measured by APCI HPLC/MS are compared with results from gas chromatography – isotope dilution mass spectrometry (GC-ID/MS), high performance liquid chromatography (HPLC) and fluorescence polarization immunoassay (FPIA). The accuracy, precision and recovery of the APCI HPLC/MS and GC-ID/MS methods are discussed. The coefficient of variation (CV) determined from duplicate samples was less than 2%. The detection limit was 10 ng/ml at a signal-to-noise ratio of 3:1. Received: 17 January 1996/Revised: 26 March 1996/Accepted: 5 April 1996     

Determination of Bromate in Bottled Drinking Water from Saudi Arabian Markets by HPLC/ICP-MS

The determination of bromate BrO₃ ^? in 50 different bottled drinking water samples collected from Saudi Arabian markets has been investigated using liquid chromatography inductively coupled plasma mass spectrometry (HPLC/ICP-MS). For analysis, samples were injected directly without any further pretreatment or dilution, using only a 50 μL injection volume. The method showed: detection limit of 0.5 μg/L, limit of quantification of 1.0 μg/L, 1.0 ? 200.0 μg/L linearity range (r² = 0.9998), relative standard deviation (%RSD) for reproducibility (inter-day precision) values of 14% and 4% for low and high concentration levels (10,100 μg/L), respectively. The results obtained for bromate showed that 30% of the samples are acceptable as US EPA standards (10 μg/L), 40% of the samples are acceptable as Gulf (Saudi Arabia) standards (25 μg/L), and almost 60% of the samples exceed the allowable limits for bromate in bottled drinking water.