Determination of Nimesulide by Ion Pair High-Performance Liquid Chromatography Using Tetrabutylammonium as the Counterion

A new method for nimesulide was developed using ion-pair reversed phase liquid chromatography and tetrabutylammonium hydrogen sulfate as the ion-pairing reagent. The influence of the ion pair forming reagent concentration, pH, and mobile phase composition on the retention time of nimesulide were studied. The optimum experimental conditions included a C18 column, a mobile phase of a 50/50 (v/v) mixture of acetonitrile and 15 mM phosphate buffer (pH 8.00) containing 6 mM tetrabutylammonium hydrogen sulfate, 25°C, isocratic elution, a flow rate of 1 mL/min, a run time of 10 minutes, and photodiode array detection at 404 nm. From the analysis of the results, the mechanism for the separation of nimesulide was also established. The retention time for nimesulide was 4.76 ± 0.05 min. The method was linear between concentrations of 9 µg/mL to 64 µg/mL, with limits of detection and quantification of 1.111 µg/mL and 3.390 µg/mL, respectively. The method is simple, rapid, accurate, and precise, and successfully applied for the determination of nimesulide in pharmaceutical products.     

Liquid Chromatographic Determination of Glyoxal and Methylglyoxal from Serum of Diabetic Patients using Meso‐Stilbenediamine as Derivatizing Reagent

Abstract

Meso‐stilbenediamine has been used as derivatizing reagent for liquid chromatographic (LC) determination of glyoxal (Go), methylglyoxal (MGo), and dimethylglyoxal (DMGo) at pH 3. Liquid chromatographic elution and separation was carried out from the column Kromasil 100 C‐18, 5 µm (15×0.46 mm i.d.) with methanol: water:acetonitrile (59:40:1, v/v/v) with a flow rate of 1 mL/min and ultraviolet detection at 254 nm. The linear calibration curves were obtained for Go, MGo, and DMGo within 0.97–4.86 µg/mL, 1.52–7.6 µg/mL, and 1.41–7.08 µg/mL with detection limits of 48 ng/mL, 76 ng/mL, and 70.8 ng/mL, respectively. The method was applied for the determination of Go and MGo from serum of patients suffering from diabetes and ketosis. The amounts of Go and MGo found were 0.150–0.260 µg/mL and 0.160–0.270 µg/mL with coefficient of variation (C.V.) 2.6–4.7% and 2.5–4.6%, respectively. The results obtained were compared with normal subjects with Go and MGo contents of 0.025–0.065 µg/mL and 0.030–0.070 µg/mL with C.V 1.5–4.9% and 1.6–4.8% in the serum.     

Spectrophotometric determination of Hg(II) in water samples by dispersive liquid liquid microextraction with use ionic liquid after derivatization with a water soluble Fe(II) phthalocyanine

This study reports the synthesis of water soluble iron(II) phthalocyanine and a facile method for spectrophotometric determination of Hg(II) in environmental water samples by ionic liquid based dispersive liquid–liquid microextraction (IL-DLLME). In the method, 1-heptyl-3-methylimidazolium hexafluorophosphate (250 µL) as extraction solvent, acetonitrile (750 µL) as dispersive solvent and Triton X-100 (200 µL) as anti-sticking agent were used. After the extraction of the Hg(II) complex (Hg(II):q-Fe(II)-Pc) into thin droplets of ionic liquid, the sample was centrifuged for 4 min at 2000 rpm. The upper aqueous phase was removed and the residue diluted to 250 µL with methanol and transferred to a 250 µL cell for spectrophotometric detection at 280 nm. The linear range of the method is 0.05–1 µg/mL. The limits of detection and quantification is 0.01 and 0.03 µg/mL, respectively. The RSD for the developed method was calculated as 0.78% at 0.50 µg/mL Hg(II).     

Development and Validation of Stability-Indicating HPLC Methods for Quantitative Determination of Pravastatin,Fluvastatin, Atorvastatin,and Rosuvastatin in Pharmaceuticals

Abstract

High-performance liquid-chromatographic (HPLC) methods were validated for determination of pravastatin sodium (PS), fluvastatin sodium (FVS), atorvastatin calcium (ATC), and rosuvastatin calcium (RC) in pharmaceuticals. Two stability-indicating HPLC methods were developed with a small change (10%) in the composition of the organic modifier in the mobile phase. The HPLC method for each statin was validated using isocratic elution. An RP-18 column was used with mobile phases consisting of methanol–water (60:40, v/v, for PS and RC and 70:30, v/v, for FVS and ATC). The pH of each mobile phase was adjusted to 3.0 with orthophosphoric acid, and the flow rate was 1.0 mL/min. Calibration plots showed correlation coefficients (r) > 0.999, which were calculated by the least square method. The detection limit (DL) and quantitation limit (QL) were 1.22 and 3.08 µg/mL for PS, 2.02 and 6.12 µg/mL for FVS, 0.44 and 1.34 µg/mL for ATC, and 1.55 and 4.70 µg/mL for RC. Intraday and interday relative standard deviations (RSDs) were <2.0%. The methods were applied successfully for quantitative determination of statins in pharmaceuticals.     

Preconcentration of beryllium via octadecyl silica gel microparticles doped with aluminon, and its determination by flame atomic absorption spectrometry

A simple and sensitive method is presented for solid phase extraction (SPE) and preconcentration of trace quantities of beryllium using octadecyl silica gel modifed with aurin tricarboxylic acid (aluminon). Beryllium is then determined by flame atomic absorption spectroscopy. Parameters affecting SPE such as pH, sample solution and eluent flow rate, type, concentration and volume of eluent, interfering ions and breakthrough volume, were investigated. Under optimal conditions, the beryllium ions were retained on the sorbent at pH 6–6.7, while 3.0 mL of 0.05 mol L^?1 HNO₃ is sufficient to elute the ions. The limit of detection (LOD) based on 3σ was 0.8 µg L^?1 for 250 mL sample solution and 5 mL 0.05 mol L^?1 HNO₃ as eluent. The LOD can reach 0.1 µg L^?1 for 1 L sample solution and 3 mL of 0.05 mol L^?1 HNO₃. The accuracy and precision (RSD %) of the method is >90% and <10%, respectively. The method was applied to the determination of beryllium in aqueous samples.     

Simultaneous determination of four hormonal compounds in oral contraceptive tablet formulations by high performance liquid chromatography

A rapid, accurate, and precise HPLC method has been developed for simultaneous determination of four contraceptive hormonal compounds namely ethinylestradiol (EE), drospirenone (DR), gestodene (GS), and levonorgestrel (LV) in oral contraceptive tablet dosage form. The chromatographic separation was achieved on a C18 (150 × 4.6 mm, 5μ) column; the mobile phase consists of acetonitrile: water (50:50, v/v) pumped at a flow rate of 1.0 mL/min; and UV detection was set at 200 nm. The limit of detection was 0.0086 µg/mL for (EE), 0.0397 µg/mL for (GS), 2.80 µg/mL for (DR), and 0.229 µg/mL for (LV), whereas the limit of quantitation (LOQ) was 0.028 µg/mL for (EE), 0.132 µg/mL for (GS), 9.500 µg/mL for (DR), and 0763 µg/mL for (LV), respectively. The correlation coefficient (r) values of the four compounds ranged from 0.99995 to 0.99999. The method was validated as per ICH guidelines and USP 34 for estimation of (EE), (DR), (GS), and (LV) in commercially available tablet dosage form. The validation results were found satisfactory. The proposed method can be useful in quality control of bulk manufacturing and pharmaceutical dosage forms.     

Microwave Assisted Extraction of Polycyclic Aromatic Hydrocarbons and their Determination by Gas Chromatography–Mass Spectrometry: Validation of the Method and Application to Marine Sediments

Microwave-assisted extraction of sixteen polycyclic aromatic hydrocarbons and their gas chromatographic mass spectrometric detection are presented herein. An efficient extraction was achieved in 15 minutes using 10 mL of 1:1 n-hexane-acetone while a clean-up step was developed studying the elution curves on solid phase extraction silica cartridges. The analytical method was optimized and validated using a certified reference marine sediment; satisfactory figures of merit were obtained with limits of detection in the range 0.001–0.004 µg/g, precision within 6%, and good linearity (regression coefficients generally higher than 0.998, in the concentration range 0.010–1.000 µg/mL). The developed method was successfully applied to the determination of polycyclic aromatic hydrocarbons in real marine sediments collected in two coastal areas of Italy exposed to different anthropic impact: three tourist sites of Liguria and the Venetian Lagoon. The total concentration of the analytes in the samples was in the range 1.027–3.827 µg/g and the use of common markers suggested their probable pyrolytic origin.     

Construction of Three Single‐Chain Antibody Fragment Variable Fusion Structures for Sensitive Detection of Nucleocapsid Protein of Hantaan Virus

Abstract

Three single‐chain fragment variable (scFv) fusion structures were constructed for use in rapid and sensitive detection of nucleocapsid protein (NP) of Hantaan virus. The detection of NPs on glass chips was signalized by enzyme labeling or fluorescence dye Cy3, or Cy5 cluster nanoparticles. The sensitivity of the methods with different signal systems was evaluated and compared. The detection limits of scFv‐alkaline phosphatase fusion, fluorescence labeling (scFv‐Cy3), and nanoparticles labeling (scFv‐SBP‐streptavidin‐nanoparticle) were 0.1 µg/mL, 1 ng/mL, and 0.1 ng/mL NP, respectively, which were all lower than that in a conventional enzyme‐linked immunosorbent assay (ELISA) (1 µg/mL). Twenty Hantaan virus isolates were detected using the proposed methods.     

Simple Determination of 1-Deoxynojirimycin in a New Dietary Supplement by Liquid Chromatography

A simple and fast chromatographic method using ultraviolet diode-array detector (UV-DAD) was developed for the high performance liquid chromatography determination of the content of 1-deoxynojirimycin (DNJ) in a new dietary supplement in the form of granules for oral solution preparation. The derivatization reaction was carried out at room temperature for 15 min at pH 7. The reaction reached completeness at a reagent to analyte molar ratio of about 60. The chromatographic separations were performed on a C18 Phenomenex Synergi Fusion stainless steel column (250 mm?×?4.6 mm; 4 µm) with detection at λ?=?254 nm. The mobile phase consisted of triethylammonium (TEA) phosphate buffer (0.05 M; pH 3) and acetonitrile under gradient conditions at a flow-rate ramping from 1 to 1.2 mL/min. The validation parameters (linearity, sensitivity, accuracy, precision, specificity and stability) were satisfactory. Intra-day precision (relative standard deviation, RSD) was ≤?2.23% for peak area and retention time without significant differences between intra- and inter-day data. Recovery studies gave good results (93.59%; n?=?15) with a RSD of 2.64%. The developed method is suitable for the quality control of DNJ in raw material and industrial products. The method can be applied in any analytical laboratory and does not require sophisticated instrumentation.     

Square Wave Adsorptive Stripping Voltammetric Determination of Cyromazine Insecticide with Multi-Walled Carbon Nanotube Paste Electrode

The electrochemical behavior of cyromazine (N-cyclopropyl-1,3,5-triazine-2,4,6 triamine) insecticide has been studied at newly prepared multi-wall carbon nanotubes paste electrodes using square wave stripping voltammetry. The cyromazine was accumulated at 0.0 mV [vs. Ag/AgCl (3 M NaCl)] and a well-defined anodic peak obtained at +1110 mV in 0.1 M H₂SO₄. The cyclic voltammetric measurements showed an irreversible nature of oxidation wave in the range of scan rates comprised between 500 and 4000 mV s^?1. The calibration curve obtained from square wave stripping voltammetry was linear in the range 0.41 to 83.30 µg/mL with a detection limit of 0.12 µg/mL. The method was applied to the direct determination of cyromazine in natural water samples. Recoveries calculated for river and tap water samples spiked with 10.0 µg/mL level were 101.5 ± 1.9% and 100.6 ± 2.3% at 95% confidence level, respectively. The method was extended to the determination of cyromazine in agrochemical formulation Trigard® with a recovery of 100.49% and accuracy was in agreement with that obtained by HPLC comparison method. Influences of some interfering ions and pesticides were also investigated.     

Determination of traces of As,Cd, Cr,Hg, Mn,Ni, Sb,Se, Sn and Pb in human hair by triple quadrupole ICP-MS

With the wide range of metallic contaminants discharged in the environment, studying the human health requires a growing number of elements to be monitored in biological samples. Hair analysis has been suggested as a suitable tool for biomonitoring environmental and occupational exposure to toxic elements. This study describes a method for the determination of 10 trace elements in hair samples using ICP-QQQ-MS. Combining the power of the MS/MS high-energy Helium mode with the MS/MS O₂ mass-shift mode, the method offers great analytical performances with detection limits reaching 0.0014 µg g^?1 for As, 0.0016 µg g^?1 for Cd, 0.012 µg g^?1 for Cr, 0.0035 µg g^?1 for Hg, 0.0055 µg g^?1 for Mn, 0.10 µg g^?1 for Ni, 0.0012 µg g^?1 for Sb, 0.0083 µg g^?1 for Sn, 0.011 µg g^?1 for Se and Pb. The accuracy of the method was tested on a human hair ERM® certified reference material. Percent recoveries varied from 91.3% and 106.9% being always in the acceptance range of 90–110%. For all analysed elements, RSD% of repeatability ranged between 0.6% and 9.0% and those of intermediate precision did not exceed the limit of 20% being always lower than 10% (except for As). The proposed method was applied for the determination of trace elements in hair samples from 20 unexposed subjects. The geometric mean levels were as follows: Cr 0.28 µg g^?1, Mn 0.30 µg g^?1, Sn 1.04µg g^?1, Sb 0.07 µg g^?1, Hg 0.42 µg g^?1, As 0.02 µg g^?1, Cd 0.03 µg g^?1, Ni 0.51 µg g^?1, Se 0.45 µg g^?1 and Pb 1.83 µg g^?1. Element concentrations were in the same range with the reported data. The reported results may be useful for environmental exposure assessment or comparisons studies when establishing reference values of trace elements in exposed population.     

Determination of Plumbagin in Plant Extracts and Polyherbal Formulations by High-Performance Liquid Chromatography with Fluorescence Detection

Plumbagin, a naturally occurring naphthoquinone derivative, is known to possess various pharmacological activities. A rapid, sensitive, and specific high-performance liquid chromatographic method using fluorescence detection is reported for the determination of plumbagin in two Plumbago species and five polyherbal formulations. The method employed a reverse phase C18 column with isocratic elution using 65:35 pH 3.2 methanol and 0.1% aqueous o-phosphoric acid at a flow rate of 1.0 mL/min. Plumbagin displayed maximal fluorescence with excitation at 264 nm and emission at 605 nm. A linear calibration relationship was obtained for 1 to 10 µg/mL plumbagin with limits of detection and quantitation of 8 ng/mL and 30 ng/mL, respectively. The relative standard deviation values for intraday and interday precision were less than 2%. The recoveries were greater than 97% with relative standard deviations less than 3%. This is the first study to employ high-performance liquid chromatography with fluorescence detection for the determination of plumbagin. The method was rapid, sensitive, and accurate for the analysis of plants and polyherbal formulations.     

Development and validation of a fully automated online-SPE–ESI–LC–MS/MS multi-residue method for the determination of different classes of pesticides in drinking,ground and surface water

The present work describes a fully automated method based on online solid phase extraction–liquid chromatography–tandem mass spectrometry for the determination of different classes of pesticides, including acidic and polar pesticides and six thiamethoxam metabolites. Sample preconcentration was performed by extracting 4 mL of the sample with a single styrene-divinylbenzene polymer. Elution of the compounds was done within the high performance liquid chromatography gradient and tandem mass spectrometry determination was performed in the selected reaction monitoring mode, by recording 1–3 transitions per compound. The overall pretreatment and analysis time per sample was less than 15 min. Method validation was performed in drinking, ground and surface water. For nearly all compounds a recovery between 70% and 120% could be achieved. The limit of detection ranges from 1.2 to 18 ng/L in drinking water and 3.0 to 23 ng/L in ground and surface water. The correlation coefficients for a calibration range of 0.05–2 µg/L are between 0.9915 and 0.9999. The limit of quantification (LOQ) for all compounds lies below the required limit of 0.1 µg/L, to fulfil the Council Directive 98/83/EC. Most of the compounds easily reach an LOQ below 0.05 µg/L.     

Analytical Methods for the Determination of Traces of Cr(VI) in Water Samples with Suppressed Ion Chromatography

A rapid and sensitive method for the direct determination of hexavalent chromium in natural waters has been developed. Anion exchange chromatography was used for the fast separation of chromates from matrix anions, within 15 minutes, using a 35 mM KOH eluant. Mobile phase suppression was employed prior to direct conductivity (CD) detection, comparing two different electrolytic suppressor models and achieving a 10 times lower detection limit. Post column derivatization of Cr(VI) with diphenylcarbazide was used for further selective diode array (PDA) detection. Possible Cr(III) interference was evaluated with the addition of concentrations up to 10 mg/L of Cr(III) in a Cr(VI) positive natural water sample resulting in negligible interference. Both detection techniques gave instrumental LOD of 0.05 µg/L and method LOD of 0.08 µg/L for CD and 0.05 µg/L for PDA detection in underground water. Average repeatability and reproducibility (%RSD) was 1.3% and 5.4% for CD and 1.3% and 6.1% for PDA detection for two concentration levels. Recovery ranged from 70% to 103% for CD and from 90% to 100% for PDA. Method accuracy was additionally confirmed by analyzing positive samples with LC-ICP-MS. The method was successfully applied to the determination of Cr(VI) in several tap, spring and groundwater samples from the wider area of Asopos River, Greece. High concentrations where confirmed to the majority of the analyzed samples, revealing the serious and expanded problem of industrial pollution.     

Flow Injection Post-Chemiluminescence Reaction of Astemizole in N-Bromosuccinimide-Calcein System and Its Application

A flow injection post chemiluminescence (FI-PCL) reaction was found when astemizole was mixed with the CL reaction mixture of N-bromosuccinimide and calcein under alkaline conditions. Based on this observation, a simple and sensitive post chemiluminescence (PCL) technique for the assay of astemizole was described. Under the optimized conditions, the PCL values responded linearly to the concentration of astemizole in the range 1.0 × 10^?3–3.0 µg/mL, with a detection limit of 7.0 × 10^?4 µg/mL. The relative standard deviation was 1.7% for 1.0 × 10^?2 µg/mL astemizole solution (n = 13). It was applied to the determination of astemizole in pharmaceutical preparations with satisfactory results.     

Development and validation of a dried blood spot–HPLC assay for the determination of metronidazole in neonatal whole blood samples

A selective and sensitive high-performance liquid chromatography method with UV detection for the determination of metronidazole in dried blood spots (DBS) has been developed and validated. DBS samples [spiked or patient samples] were prepared by applying blood (30 µL) to Guthrie cards. Discs (6 mm diameter) were punched from the cards and extracted using water containing the internal standard, tinidazole. The extracted sample was chromatographed without further treatment using a reversed phase system involving a Symmetry® C18 (5 µm, 3.9?×?150 mm) preceded by a Symmetry® guard column of matching chemistry and a detection wavelength of 317 nm. The mobile phase comprised acetonitrile/0.01?M phosphate solution (KH₂PO₄), pH 4.7, 15:85, v/v, with a flow rate of 1 mL/min. The calibration was linear over the range 2.5–50 mg/mL. The limits of detection and quantification were 0.6 and 1.8 µg/mL, respectively. The method has been applied to the determination of 203 DBS samples from neonatal patients for a phamacokinetic/pharmacodynamic study.     

A novel liquid chromatography-fluorescence method for the determination of delafloxacin in human plasma

Delafloxacin is a novel fluoroquinolone antibiotic that was approved by the European Medicine Agency to treat bacterial infections of the skin and underlying tissues, and community-acquired pneumonia. Despite being in the market since 2019 in the European Union, there is no published liquid chromatography-fluorescence method for delafloxacin quantification in biological samples. A novel, rapid, and sensitive high-performance liquid chromatographic method was developed to determine delafloxacin in human plasma using its native fluorescence. Plasma delafloxacin concentrations were determined by reverse-phase chromatography with fluorescence detection at 405/450 nm of excitation/emission wavelengths. Delafloxacin was separated on a Kromasil C18 column 250 × 4.6 mm id, 5 µm using isocratic elution. The mobile phase was a mixture of 0.05% trifluoroacetic acid/acetonitrile (52/48). Retention times were 5.4 and 11.6 min for delafloxacin and valsartan (internal standard), respectively. Regression calibration curves were linear over the range of 0.1–2.5 µg/mL. The lower limit of detection was 0.05 µg/mL, and the lower limit of quantification was 0.1 µg/mL. Accuracy and precision were always <11%, and the limit of quantification was <16%. Mean recovery was 98.3%. This method can be applied to determine delafloxacin in human plasma and could be useful to perform pharmacokinetic studies.     

Determination of Arbutin,Niacinamide, and Adenosine in Functional Cosmetic Products by High-Performance Liquid Chromatography

A reversed-phase high-performance liquid chromatography method using a diode array detector at 260 nm was developed and validated for the determination of arbutin, niacinamide, and adenosine in cosmetics. The analytes were extracted using methanol and deionized water. The separations were performed on a C₁₈ column with gradient elution. At the optimized conditions, the limits of detection for arbutin, niacinamide, and adenosine were 0.75, 0.12, and 0.01 µg/mL, respectively. The average recoveries were between 98.1% and 107.5%. The method was used to analyze thirty cosmetics.     

Use of ionic liquid based chitosan as sorbent for preconcentration of fluoroquinolones in milk,egg, fish,bovine, and chicken meat samples by solid phase extraction prior to HPLC determination

The possibility of using ionic liquid based chitosan sorbent for the separation and preconcentration of fluoroquinolone antibiotics (marbofloxacin, enoxacin, ofloxacin, ciprofloxacin, and enrofloxacin) has been studied. For this reason, different ionic liquids were prepared and coated on the chitosan sorbent. The conditions of the preconcentration of fluoroquinolones on a microcolumn have been optimized and the extraction efficiencies of the prepared sorbents have been compared. The compounds were eluted with 5 mL of 20% NH₃ (v/v, MeOH) solution and determined by HPLC with diode array and fluorescence detector. The limits of detection were found as 4.23 µ g L^?1 for marbofloxacin, and 1.09 µg L^?1 for enoxacin; 3.23 × 10^?3 µg L^?1 for ofloxacin; 8.39 × 10^?3 µg L^?1 for ciprofloxacin; and 19.50 × 10^?3 µg L^?1 for enrofloxacin. The developed method was applied for the analysis of fluoroquinolone in milk, egg, fish, bovine, and chicken samples and the recoveries were obtained in the range 70–100%.     

Dispersive Liquid-Liquid Microextraction Coupled to Gas Chromatography-Electron Capture Detection for the Analysis of Trihalomethane Formation Potential

Dispersive liquid-liquid microextraction (DLLME) is an attractive miniaturized technique that utilizes microliter volumes of extraction solvents. In this study, a DLLME technique was employed for the determination of four major trihalomethane (THM) compounds and analyzed using gas chromatography-electron capture detection. Optimization was conducted in terms of type and volume of disperser solvent, type and volume of extraction solvent, and addition of salt and extraction time. Optimized conditions employed methanol (0.25 mL) as the disperser solvent containing carbon disulfide (20 µL) as the extraction solvent. The linear range was 0.020–4.00 µg/L. Low limits of detection for the analytes were obtained in the range of 0.01 to 0.24 µg/L with enrichment factors ranging from 95–283. The relative recoveries of THMs from water samples at spiking level of 2 µg/L were in the range of 79.9 to 103.4%. This method was successfully applied to the determination of THM formation potential (THMFP) in river water samples. It was found that the concentration of THMFP in three Malaysian rivers were below the maximum permissible limits of World Health Organization (WHO).