Automated hollow‐fiber liquid‐phase microextraction followed by liquid chromatography with mass spectrometry for the determination of benzodiazepine drugs in biological samples

In this study, two‐phase hollow‐fiber liquid‐phase microextraction and three‐phase hollow‐fiber liquid‐phase microextraction based on two immiscible organic solvents were compared for extraction of oxazepam and Lorazepam. Separations were performed on a liquid chromatography with mass spectrometry instrument. Under optimal conditions, three‐phase hollow‐fiber liquid‐phase microextraction based on two immiscible organic solvents has a better extraction efficiency. In a urine sample, for three‐phase hollow fiber liquid‐phase microextraction based on two immiscible organic solvents, the calibration curves were found to be linear in the range of 0.6–200 and 0.9–200 μg L^?1 and the limits of detection were 0.2 and 0.3 μg L^?1 for oxazepam and lorazepam, respectively. For two‐phase hollow fiber liquid‐phase microextraction, the calibration curves were found to be linear in the range of 1–200 and 1.5–200 μg L^?1 and the limits of detection were 0.3 and 0.5 μg L^?1 for oxazepam and lorazepam, respectively. In a urine sample, for three‐phase hollow‐fiber‐based liquid‐phase microextraction based on two immiscible organic solvents, relative standard deviations in the range of 4.2–4.5% and preconcentration factors in the range of 70–180 were obtained for oxazepam and lorazepam, respectively. Also for the two‐phase hollow‐fiber liquid‐phase microextraction, preconcentration factors in the range of 101–257 were obtained for oxazepam and lorazepam, respectively.     

Determination of Iodate in Iodized Salt by Reversed-Phase High-Performance Liquid Chromatography with UV Detection

A method for the determination of iodate was developed by reversed-phase high-performance liquid chromatography with UV detection. Iodate was converted to iodine, which was separated from the matrix using a reversed-phase Ultrasphere C₁₈ column (250 × 4.6 mm, 5 μm) with methanol-1 mmol L^?1 H₃PO₄ (20:80, v/v) as mobile phase at 1.00 mL min^?1 and UV detection at 224 nm. The calibration graph was linear from 0.05 μg mL^?1 to 5.00μg mL^?1 for iodine with a correlation coefficient of 0.9994 (n=7). The detection limit was 0.01 μg mL^?1. The method was successfully applied to the determination of iodate in iodized salt. The recovery was from 96% to 101% and the relative standard deviation was in the range of 1.5% to 2.9%.     

Headspace single-drop microextraction coupled with gas chromatography electron capture detection of butanone derivative for determination of iodine in milk powder and urine

A new detection method using headspace single-drop microextraction (HS-SDME) coupled to gas chromatography (GC) was established to determine the iodine in milk powder and urine. The derivative from the reaction between iodine and butanone in the acidic media was extracted into a micro-drop then determined by GC-ECD. With the optimisation of HS-SDME and derivatisation, the calibration curve showed good linearity within the range of 0.004–0.1 μg mL^?1 (0.004–0.1 μg g^?1) (R ² = 0.9991), and the limits of detection for milk powder and urine were 0.0018 μg g^?1 and 0.36 μg L^?1, respectively. The mean recoveries of milk powder and urine were 90.0–107 % and 89.4–101 % with mean RSD of 1.7–3.4 % and 2.7–3.3 %, respectively. This detection method affords a number of advantages, such as being simple, rapid, and inexpensive, with low organic solvent consumption, and is remarkably free from interference effects, rendering it an efficient method for the determination of iodine in milk powder and urine samples.     

Modification of Soxhlet Extractor for Rapid and Effective Recovery of Phenolic Pollutants Adsorbed on XAD-4 Resin

A newly modified extractor facilitated rapid extraction (10.0 mL, 1 h) of eleven phenols from XAD-4 resin for comparable recoveries to those with conventional Soxhlet extractor (80.0 mL, 3 h). Combined with analysis by gas chromatography and gas chromatography-mass spectrometry in selected ion monitoring mode as tert-butyldimethylsilyl derivatives, the overall method was linear (≥ 0.9991) with satisfactory precision (≤ 9.2% RSD), accuracy (≤ 7.7% RE), detection limit (≤ 0.02 μg L^?1), and recovery rates (≥ 75.0%) in 0.05 to 1.0 μg L^?1. Six phenolic pollutants were quantitatively screened along with bisphenol A (0.028 μg L^?1) from river water.     

Validated LC Determination of the Piroxicam-β-Cyclodextrin Inclusion Complex in Tablets and in Human Plasma

A simple, rapid, specific, sensitive HPLC method has been developed for the determination of piroxicam in the tablet dosage form and in human plasma. The method totally eliminates solvent extraction and time-consuming separation procedures. Plasma proteins were precipitated by addition of 3:1 (v/v) acetonitrile-methanol, ZnSO₄, and MgSO₄ and the supernatant was injected directly on to a 250 mm × 4.6 mm, 5 μm particle Spherisorb analytical column. Acetonitrile-methanol-0.04 mol L^?1 KH₂PO_4, 40:10:50 (v/v); pH 3.8, was used as mobile phase. The drug was detected by UV detection at 330 nm. The response was linear over the range of 0.01–10 μg mL^?1 and 0.025–5 μg mL^?1 in mobile phase and human plasma samples, respectively. The proposed method was used without interference from the endogenous substances, for determination of piroxicam in plasma samples obtained from healthy volunteers. The results revealed that the method would be useful in monitoring plasma levels of the drug during pharmacokinetic studies. Assay of piroxicam in its dosage forms for quality-control purposes could also be performed successfully by use of this method.     

Determination of Tetracyclines in Water Samples Using Liquid Chromatography with Fluorimetric Detection

A liquid chromatographic method with fluorimetric detection is proposed for the determination of trace levels of oxytetracycline, tetracycline, chlortetracycline and doxycycline in water samples. The analytes are preconcentrated by solid phase extraction using reversed phase polymeric cartridges and acetonitrile as eluent. Preconcentration factors up to 125 can be obtained. The chromatographic separation is performed on a polymeric column with a gradient elution program using mobile phases based on mixtures of acetonitrile and 0.01 mol L^?1 oxalic acid aqueous solution at a flow rate of 1.2 mL min^?1. Tetracyclines are post-column derivatized with a reagent solution consisting of 0.1 mol L^?1 Mg(II) at pH 9 at a flow rate of 0.6 mL min^?1. The highly fluorescent Mg(II) chelates are detected at λ _ex = 374 nm and λ _em = 499 nm. The detection limits of the whole process are in the low μg L^?1 level. The proposed method has been applied to the analysis of spiked natural water samples, and recovery rates higher than 80% have been obtained.     

Development of Dispersive Liquid‐Liquid Microextraction Based on Solidification of Floating Organic Drop for the Determination of Trace Cobalt in Water Samples

A liquid‐phase microextraction technique was developed using dispersive liquid‐liquid microextraction based on solidification of floating organic drop combined with flame atomic absorption spectrometry, for the extraction and determination of trace amounts of cobalt in water samples. Microextraction efficiency factors, such as the type and volume of extraction and dispersive solvents, pH, extraction time, the chelating agent amount, and ionic strength were investigated and optimized. Under optimum conditions, an enrichment factor of 160 was obtained from 10.0 mL of water sample. The calibration graph was linearin the range of 1.15‐110 μg L^?1 with a detection limit of 0.35 μg L^?1. The relative standard deviation for ten replicate measurements of 10 and 100 μg L^?1 of cobalt were 3.26% and 2.57%, respectively. The proposed method was assessed through the analysis of certified reference water or recovery experiments.     

Temperature-controlled ionic liquid dispersive liquid phase microextraction combined with ultra-high-pressure liquid chromatography for the rapid determination of triclosan, triclocarban and methyl-triclosan in aqueous samples

As extraction solvents, ionic liquids have green characteristics. In this study, an environmentally benign analytical method termed temperature-controlled ionic liquid dispersive liquid phase microextraction (TIL-DLME) combined with ultra-highpressure liquid chromatography (UHPLC)-tunable ultraviolet detection (TUV) was developed for the pre-concentration and determination of triclosan (TCS), triclocarban (TCC) and methyl-triclosan (M-TCS) in water samples. Significant parameters that may affect extraction efficiencies were examined and optimized, including the types and amount of ionic liquids, volume of the diluent, heating temperature, cooling time, salt effect and pH value. Under the optimum conditions, linearity of the method was observed in the ranges of 0.0100–100 μg L^?1 for TCS and M-TCS, and 0.00500–50.0 μg L^?1 for TCC with correlation coefficients (r ²) > 0.9903. The limits of detection (LODs) ranged from 1.15 to 5.33 ng L^?1. TCS in domestic water and TCC in reclaimed water were detected at the concentrations of 1.01 and 0.126 μg L^?1, respectively. The spiked recoveries of the three target compounds in reclaimed water, irrigating water, waste water and domestic water samples were obtained in the ranges of 68.4%–71.9%, 61.6%–87.8%, 58.9%–74.9% and 64.9%–92.4%, respectively. Compared with the previous dispersive liquid-liquid microextraction method (DLLME) about the determination of TCS, TCC and M-TCS, this method is not only more environmentally friendly but also more sensitive.     

Separation and Quantification of Enkephalin and Vasopressin Related Peptides in Reversed-Phase Capillary Liquid Chromatography

A method for determination of some biologically active penta- and nona-peptides under isocratic conditions in capillary liquid chromatography was developed. Separation system consisting of XTerra C18 stationary phase and mobile phase composed of a mixture of acetonitrile with 0.1% trifluoroacetic acid (TFA) and water with 0.1% TFA in the ratios 75/25 (v/v) and 85/15 (v/v) was suitable not only for a good resolution of enkephalin and vasopressin related peptides, respectively, but it also enabled separation of the respective biopeptides from other constituents of human urine. Calibration curves for the studied peptides were linear in the measured concentration range from 1.00 to 1.57×10^?2 mg mL^?1. The limit of detection and limit of quantification were in the range of units of μg mL^?1 and tens of μg mL^?1, respectively; slightly higher values were obtained for nonapeptides. Determination of certain biologically active peptides in urine can serve in future as a tool for diagnosis of various diseases, e.g. autism.     

Determination of Steroids in Human Urine by Micellar Liquid Chromatography

Abstract

A simple and sensitive method for the determination of steroids using micellar liquid chromatography is described. The steroids, including hydroxycorticosterone. corticosterone, northisterone, testosterone, mexdroprogesterone acetate and progesterone, were separated by reversed-phase using a micelles mobile phase following UV detection at 245 nm. The parameters affecting retention of the test solutes such as the concentration of sodium dodecyl sulfate (SDS) and n-butanol-1 in the mobile phase were investigated. It was found that the retention of the solutes was dependent on the composition of mobile phase. The linear calibration plots range from 0.1 to 10 μg ml^?1 in mobile phase containing 5.0 × 10^?2 mol l^?1 SDS/9 % n-butanol-1 at pH 6.0, and the detection limit in order of 0.1 μg ml^?1 was obtained. The proposed method was used for the determination of steroids in urine using direct injection of samples without previous treatment.     

Ultrasound Assisted Emulsification Microextraction Based on dimetyl (E)‐2‐[(Z)‐1‐acetyl)‐2‐hydroxy‐1‐propenyl]‐2‐butenedioate for Determination of Total Amount of Iron in Water and Tea Samples

An ultrasound assisted emulsification microextraction (USAEME) is successfully used for extraction and determination of trace amount of iron in water and tea samples, followed by flame atomic absorption spectroscopy (FAAS). In this approach, a new synthetic ligand dimetyl (E)‐2‐[(Z)‐1‐acetyl)‐2‐hydroxy‐1‐propenyl]‐2‐butenedioate (DAHPB) is used as chelating agent and chloroform is selected as an extraction solvent. The factors influencing the complex formation and extraction by USAEME method are optimized. These factors are extraction solvent type as well as extraction volume, time, temperature, pH, and the amount of chelating agent. Under optimum conditions, an enrichment factor of 202.9 is obtained from only 7.1 mL of aqueous phase. The calibration graph using the preconcentration system for iron is linear between 40.0 and 800.0 μg L^?1 with a detection limit of 7.4 μg L^?1. The relative standard deviation (R.S.D) for ten replicate measurements of 500.0 μg L^?1 of iron is 2.5%.     

Cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction and HPLC–DAD analysis of ezetimibe and simvastatin in human plasma and urine

A new cetyl‐alcohol‐reinforced hollow fiber solid/liquid‐phase microextraction (CA–HF–SLPME) followed by high‐performance liquid chromatography–diode array detection (HPLC–DAD) method was developed for simultaneous determination of ezetimibe and simvastatin in human plasma and urine samples. To prepare the CA–HF–SLPME device, the cetyl‐alcohol was immobilized into the pores of a 2.5 cm hollow fiber micro‐tube and the lumen of the micro‐tube was filled with 1‐octanol with the two ends sealed. Afterwards, the prepared device was introduced into 10 mL of the sample solution containing the analytes with agitation. Under optimized conditions, calibration curves plotted in spiked plasma and urine samples were linear in the ranges of 0.363–25/0.49–25 μg L^?1 for ezetimibe/simvastatin and 0.193–25/0.312–25 μg L^?1 for ezetimibe/simvastatin in plasma and urine samples, respectively. The limit of detection was 0.109/0.174 μg L^?1 for ezetimibe/simvastatin in plasma and 0.058/0.093 μg L^?1 for ezetimibe/simvastatin in urine. As a potential application, the proposed method was applied to determine the concentration of selected analytes in patient plasma and urine samples after medication and satisfactory results were achieved. In comparison with reference methods, the CA–HF–SLPME–HPLC–DAD method demonstrates considerable potential in the biopharmaceutical analysis of selected drugs.     

Speciation analysis of chromium in water samples using nanometer zirconium dioxide and direct ultrasonic slurry sampling with electrothermal atomic absorption spectrometry

A new analytical procedure for the determination of chromium Cr(III) and Cr(VI) species in different water samples was developed. The method involves solid-phase extraction (SPE), direct ultrasonic slurry sampling (DUSSS), and subsequent electrothermal atomic absorption spectrometry (ETAAS). The nanometer-sized zirconium dioxide (ZrO₂) was used as the sorbent material. The optimal conditions for the proposed solid phase extraction were: 50 mg ZrO₂, 20 min extraction time, pH 2.5 for Cr(VI) and pH 8.0 for Cr(III) and for the ETAAS measurement: 1500°C pyrolysis and 2300°C atomisation temperatures, 1.5 g L^?1 Mg(NO₃)₂ as matrix modifier. The samples were sonicated directly in the autosampler cup, using an ultrasonic probe at 20% power setting for 10 seconds prior to injection into the graphite tube with ?vov platform. In this way, all drawbacks due to the elution procedure were eliminated. The limit of detection and limit of quantification for Cr(III) obtained under optimised conditions were 0.48 μg L^?1, and 1.61 μg L^?1, respectively, and for Cr(VI) 0.27 μg L^?1 and 0.90 μg L^?1. The pre-concentration factors attained for both the species were 25. The effects of alkaline, alkaline earth and some metal ions and some anions were also examined. The relative standard deviation estimated from six replicate measurements at a concentration of 0.4 μg L^?1 for both Cr(III) and Cr(VI) with a pre-concentration factor of 25 was 2.96% and 4.06%, respectively. The accuracy of the method was confirmed by analysis of the standard reference material SRM 1643e “Trace Elements in Water?. The proposed technique is simple, sensitive, environmentally friendly, and the risk of contamination is low. Hence, it was successfully applied to spiked synthetic and real water samples with recoveries ranging from 91.3% to 109.2%     

Optimization of dispersive liquid–liquid microextraction with central composite design for preconcentration of chlordiazepoxide drug and its determination by HPLC‐UV

A simple, rapid, and sensitive method based on dispersive liquid–liquid microextraction combined with HPLC‐UV detection applied for the quantification of chlordiazepoxide in some real samples. The effect of different extraction conditions on the extraction efficiency of the chlordiazepoxide drug was investigated and optimized using central composite design as a conventional efficient tool. Optimum extraction condition values of variables were set as 210 μL chloroform, 1.8 mL methanol, 1.0 min extraction time, 5.0 min centrifugation at 5000 rpm min^?1, neutral pH, 7.0% w/v NaCl. The separation was reached in less than 8.0 min using a C₁₈ column using isocratic binary mobile phase (acetonitrile/water (60:40, v/v)) with flow rate of 1.0 mL min^?1. The linear response (r² > 0.998) was achieved in the range of 0.005–10 μg mL^?1 with detection limit 0.0005 μg mL^?1. The applicability of this method for simultaneous extraction and determination of chlordiazepoxide in four different matrices (water, urine, plasma, and chlordiazepoxide tablet) were investigated using standard addition method. Average recoveries at two spiking levels were over the range of 91.3–102.5% with RSD < 5.0% (n = 3). The obtained results show that dispersive liquid–liquid microextraction combined with HPLC‐UV is a fast and simple method for the determination of chlordiazepoxide in real samples.     

Surfactant‐assisted dispersive liquid–liquid microextraction of nitrazepam and lorazepam from plasma and urine samples followed by high‐performance liquid chromatography with UV analysis

Surfactant‐assisted liquid–liquid microextraction followed by high‐performance liquid chromatography with UV detection has been developed for the simultaneous preconcentration and determination of lorazepam and nitrazepam in biological fluids. In this study, an ionic surfactant (cetyltrimethyl ammonium bromide) was used as an emulsifier. The predominant parameters affecting extraction efficiency such as the type and volume of extraction solvent, the type and concentration of surfactant, sample pH, and the concentration of salt added to the sample were investigated and opted. Under the optimum conditions (extraction solvent and its volume, 1‐octanol, 70 μL; surfactant and its concentration, 1 mL of ultra‐pure water containing 2 mmol L^?1 cetyltrimethyl ammonium bromide; sample pH = 9 and salt content of 10% NaCl w/v), the preconcentration factors were obtained in the range of 202–241 and 246–265 for nitrazepam and lorazepam, respectively. The limits of quantification for both drugs were 5 μg L^?1 in water sample and 10 μg L^?1 in biological fluids with R² values higher than 0.993. The suitability of the proposed method was successfully confirmed by the extraction and determination of the target drugs in human urine and plasma samples in the range of microgram per liter.     

Analysis of Arecoline in Rat Urine, and Identification of its Metabolites, by Liquid Chromatography–Tandem Mass Spectrometry

A simple and rapid high-performance liquid chromatographic–electrospray ionization (ESI) tandem mass spectrometric method has been developed for elucidation of the structures of the metabolites of arecoline in rat urine after administration of a single dose (20 mg kg^?1). The urine samples were purified on a C₁₈ solid-phase extraction cartridge and analysis was then performed on a reversed-phase C₁₈ column with 60:40 (v/v) methanol–0.01% triethylamine solution (2 mmol L^?1, adjusted to pH 3.5 with formic acid) as mobile phase and detection by on-line MS–MS. Identification of the metabolites and elucidation of their structures were performed by comparing molecular masses (ΔM), retention-times, and product ion spectra with those of the parent drug. The parent drug arecoline, four phase-I metabolites, and one phase-II metabolite were identified in rat urine.     

Dispersive liquid–liquid microextraction based on solidification of floating organic drop combined with field‐amplified sample injection in capillary electrophoresis for the determination of beta(2)‐agonists in bovine urine

Dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME–SFO) was for the first time combined with field‐amplified sample injection (FASI) in CE to determine four β₂‐agonists (cimbuterol, clenbuterol, mabuterol, and mapenterol) in bovine urine. Optimum BGE consisted of 20 mM borate buffer and 0.1 mM SDS. Using salting‐out extraction, β₂‐agonists were extracted into ACN that was then used as the disperser solvent in DLLME–SFO. Optimum DLLME–SFO conditions were: 1.0 mL ACN, 50 μL 1‐undecanol (extraction solvent), total extraction time 1.5 min, no salt addition. Back extraction into an aqueous solution (pH 2.0) facilitated direct injection of β₂‐agonists into CE. Compared to conventional CZE, DLLME–SFO–FASI–CE achieved sensitivity enhancement factors of 41–1046 resulting in LODs in the range of 1.80–37.0 μg L^?1. Linear dynamic ranges of 0.15–10.0 mg L^?1 for cimbuterol and 15–1000 μg L^?1 for the other analytes were obtained with coefficients of determination (R²) ≥ 0.9901 and RSD% ≤5.5 (n = 5). Finally, the applicability of the proposed method was successfully confirmed by determination of the four β₂‐agonists in spiked bovine urine samples and accuracy higher than 96.0% was obtained.     

Determination of hexavalent chromium in traditional Chinese medicines by high‐performance liquid chromatography with inductively coupled plasma mass spectrometry

An analytical method that combined high‐performance liquid chromatography with inductively coupled plasma mass spectrometry has been developed for the determination of hexavalent chromium in traditional Chinese medicines. Hexavalent chromium was extracted using the alkaline solution. The parameters such as the concentration of alkaline and the extraction temperature have been optimized to minimize the interconversion between trivalent chromium and hexavalent chromium. The extracted hexavalent chromium was separated on a weak anion exchange column in isocratic mode, followed by inductively coupled plasma mass spectrometry determination. To obtain a better chromatographic resolution and sensitivity, 75 mM NH₄NO₃ at pH 7 was selected as the mobile phase. The linearity of the proposed method was investigated in the range of 0.2–5.0 μg L^?1 (r² = 0.9999) for hexavalent chromium. The limits of detection and quantitation are 0.1 and 0.3 μg L^?1, respectively. The developed method was successfully applied to the determination of hexavalent chromium in Chloriti lapis and Lumbricus with satisfactory recoveries of 95.8–112.8%.     

Chiral Separation of Nateglinide and its L Enantiomer on a Molecularly Imprinted Polymer-Based Stationary Phase

A new chiral stationary phase for nateglinide (N-(trans-4-isopropylcyclohexylcarbonyl)-D-phenylalanine) based on a molecularly imprinted polymer has been prepared by non-covalent imprinting. For chromatographic analysis the effects on the separation of mobile phase composition, flow rate, and temperature were investigated, and the optimum conditions for HPLC were shown to be: mobile phase, acetonitrile; flow rate, 0.5 mL min^?1; temperature, 25 °C. It was shown that the nateglinide-imprinted polymer was capable of recognizing the enantiomeric difference between nateglinide and its L enantiomer, whereas the non-imprinted polymer had no such ability. Scatchard analysis was used to investigate the binding characteristics of the nateglinide-imprinted stationary phase; this indicated that two classes of binding site were present in the imprinted polymer. The equilibrium dissociation constant (K _D) and the apparent maximum number (Q _max) of high- and low-affinity binding sites were 3.7 × 10^?4 mol L^?1 and 11.38 μmol g^?1, and 1.81 × 10^?3 mol L^?1 and 27.73 μmol g^?1, respectively.     

Simultaneous Determination of Three Flavonoids in Rat Plasma by RP-LC After Oral Administration of the Total Flavonoids of Scutellaria barbata

A liquid chromatographic method for the simultaneous determination of three flavonoids, scutellarin (SCU), isoscutellarein-8-O-glucuronide (ISO) and luteolin (LUT) in rat plasma was developed and validated. Following a single-step liquid–liquid extraction with ethyl acetate, the analytes and internal standard (IS) (rutin) were successfully separated on a Diamonsil C₁₈ column using a mobile phase composed of acetonitrile (A)–0.2% phosphoric acid aqueous solution (B) (0–5 min, 20% A–29% A; 5–25 min, 29% A, v/v) at a flow rate of 1.0 mL min^?1. The linear range was 0.044–2.20 μg mL^?1 for SCU, 0.042–2.08 μg mL^?1 for ISO, and 0.056–2.80 μg mL^?1 for LUT, with the correlation coefficients of 0.9995, 0.9989 and 0.9963, respectively. The limit of quantification of SCU, ISO and LUT were 44, 41.6 and 56 ng mL^?1, respectively. The accuracy of assay was between 88.4 and 103.0%. The inter-day and intra-day precisions (RSD) were less than 10.5%. The developed method was simple, rapid and applied successfully to study the pharmacokinetics of SCU, ISO and LUT after oral administration of the total flavonoids of Scutellaria barbata.