LC-ESI-MS Determination of Bilobalide and Ginkgolides in Canine Plasma

A sensitive and selective method using liquid chromatography with electrospray ionization mass spectrometric detection was developed for the quantification of bilobalide and ginkgolides in canine plasma. The analytes were extracted with diethyl ether-dichloromethane-isopropanol (6:3:1, v/v) after spiking the samples with daidzein (internal standard). The lower limit of quantification (LLOQ) of the method was 2.5 μg L⁻¹ for ginkgolide B and 10.0 μg L⁻¹ for bilabolide, ginkgolide A and ginkgolide C. The accuracy of the method was within 15% of the actual values over a wide range of plasma concentrations. The intra-day and inter-day precision was better than 15% (R.S.D.). Finally, the LC-ESI-MS method was successfully applied to study the pharmacokinetics of ginkgolides and bilabolide after administration of Ginkgo biloba extracts to dogs.     

Arsenic Speciation in Plant Samples from the Iron Quadrangle, Minas Gerais, Brazil

Several plants, especially ferns, have been shown to tolerate and accumulate high arsenic concentrations in soils. The leaves and roots of the ferns Pteris vittata (Chinese brake) and Pityrogramma calomelanos as well as a medical plant (Baccharis trimera) were sampled together with their associated soils in a region impacted by ore mining, the Iron Quadrangle in Brazil, where arsenic concentrations in the soils vary sharply (6–900 μg g⁻¹). The bioaccumulation factors were found to be low compared to the literature data, which can be explained by the low water-soluble fraction of arsenic in soil. The arsenic species in the plants were mainly arsenite. In comparison to the rhizoid samples, the concentrations of arsenic were higher in the leaves of the fern samples. The medical plant behaved differently. The bioaccumulation factor was low (0.7), and trimethylarsine oxide was detected as the third arsenic species beside arsenite and arsenate in both the roots and the leaves.     

Analysis of t-Butyldimethylsilyl Derivatives of Chlorophenols in the Atmosphere of Urban and Rural Areas in East of France

A method using GC-MS and derivatization with N-(t-butyldimethylsilyl)-N-ethyltrifluoroacetamide (MTBSTFA) was developed for the analysis of 19 chlorophenols compounds in atmospheric samples (gas and particles). Air sampling was carried out using a Hi-Vol sampler with glass fibre filter and XAD-2 resin at a flow rate of 60 m³ h⁻¹. The particle and gas phases were collected separately over a period of 4 h. Samples were Soxhlet extracted, evaporated to dryness under nitrogen and refilled with acetonitrile. 100 mL of these extracts were derivatized with 100 μL of MTBSTFA at 80 °C for 1 h under strong stirring. Sylylated chlorophenols were injected into a GC-MS in splitless mode and quantified as their TBDMS derivatives in the SIM mode. Mass spectral analysis of the derivatives of the 19 compounds studied indicates that the spectra are highly specific showing an ion at [M - 57]⁺ which is useful for structure confirmation or analysis at low levels using selected ion monitoring. Quantification limits varied between 5 μg L⁻¹ and 10 μg L⁻¹ which correspond to 20 pg m⁻³ and 40 pg m⁻³ for 250 m³ of air sampled. This method was successfully applied to atmospheric samples collected simultaneously in winter 2004 in an urban (Strasbourg) and rural (Erstein) areas in east of France.     

High-Performance Liquid Chromatographic Determination of Isofraxidin in Rat Plasma

For the first time a high-performance liquid chromatographic (HPLC) method, with liquid-liquid extraction and ultraviolet (UV) absorbance detection, has been developed for quantification of isofraxidin in rat plasma. The analysis was performed on a Diamonsil C₁₈ column (200 mm × 4.6 mm i.d., 5 μm particle size) with acetonitrile–0.05% phosphoric acid, 26:74 (v/v), as isocratic mobile phase. The linear range was 0.05–8.0 μg mL⁻¹ and the lower limit of quantification was 0.05 μg mL⁻¹. The intra and inter-day relative standard deviation (RSD) for measurement of 0.25, 2.0, and 6.0 μg mL⁻¹ quality-control (QC) samples ranged from 5.7 to 6.4% and from 6.3 to 7.9%, respectively. Accuracy, as relative error (RE), was from ±5.8% to ±7.3%. The method was validated for specificity, accuracy, and precision and was successfully used in a pharmacokinetic study of isofraxidin in rat plasma after administration of Ciwujia extract.     

Electrocatalytic oxidation of dopamine at an ionic liquid modified carbon paste electrode and its analytical application

A room-temperature ionic liquid N-butylpyridinium hexafluorophosphate was used as a binder to construct an ionic liquid modified carbon paste electrode, which was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The ionic liquid carbon paste electrode (IL-CPE) showed enhanced electrochemical response and strong analytical activity towards the electrochemical oxidation of dopamine (DA). A pair of well-defined quasireversible redox peaks of DA appeared, with the redox peaks located at 215 mV (E _pa) and 151 mV (E _pc) (vs. the saturated calomel electrode, SCE) in pH 6.0 phosphate buffer solution. The formal potential (E ^0′) was calculated as 183 mV (vs. SCE) and the peak-to-peak separation as 64 mV. The electrochemical behavior of DA on the IL-CPE was carefully investigated. Under the optimal conditions, the anodic peak currents increased linearly with the concentration of DA in the range 1.0 × 10⁻⁶–8.0 × 10⁻⁴ mol/L and the detection limit was calculated as 7.0 × 10⁻⁷ mol/L (3σ). The interferences of foreign substances were investigated and the proposed method was successfully applied to the determination of DA injection samples. The IL-CPE fabricated was sensitive, selective and showed good ability to distinguish the coexisting ascorbic acid and uric acid.     

Online preconcentration system for determining ultratrace amounts of Cd in vegetal samples using thermospray flame furnace atomic absorption spectrometry

A system has been developed for online preconcentration and determination of Cd using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS). It is based on the solid-phase extraction of Cd in an Amberlite XAD-2 minicolumn loaded with 2-(2-thiazolylazo)-5-dimethylaminophenol (TAM), and the metal ion is eluted with 1 mol L⁻¹ hydrochloridric acid, followed by its determination. The online system allows determining Cd with a detection limit of 8.0 ng L⁻¹ and a quantification limit of 25.0 ng L⁻¹. The precision (repeatability), calculated as the relative standard deviation (% RSD) in sample solutions containing 0.5 and 3.0 μg L⁻¹ of Cd, was 6.1 and 4.5%, respectively. The preconcentration factor obtained was 24. The system’s accuracy was confirmed by analyzing the following certified reference materials (CRMs): Rice flour NIES 10b, Apple leaves NIST 1515 and Orchard leaves NBS 1571. This procedure was applied to the determination of Cd in cabbage and powdered guarana samples.     

Determination of Levamisole in Sheep Muscle Tissue by High-Performance Liquid Chromatography and Photo Diode Array Detection

A high-performance liquid chromatographic method for the determination of levamisole (LVM) residues in sheep muscle tissue is described. LVM was extracted with ethyl acetate under alkaline conditions and cleanup was performed by liquid-liquid partition between organic-basic and organic-acid medium. Finally, levamisole was back extracted with chloroform carefully transferred into a clean glass vial and evaporated to dryness at 50 °C under a gentle stream of nitrogen. The remaining dry residue was dissolved in the mobile phase used, filtered and an aliquot was injected automatically into the chromatograph for analysis. Chromatography was performed on a Zorbax^?SB-C₁₈ column at 50 °C and detection by a PDA detector monitored at λ_max 220 nm. The mobile phase was a mixture of 0.1 % trifluoroacetic acid (v/v) pH 2.0 and acetonitrile-methanol 3 : 2 (v/v) in a combination of 30 : 70 (v/v) and a flow rate of 1.0 mL min⁻¹, delivered isocratically. This analytical method was validated by assessing recovery efficiency using spiked muscle tissue samples with standard solutions in methanol at four fortification levels of 1/2 MRL, 1 MRL, 2 MRL and 4 MRL and five times for each concentration (n = 5). Mean recovery (R%) achieved for muscle tissue was 75.65 ± 2.74% with an acceptable Relative Standard Deviation RSD% = 10.4. The same method was used also for the analysis of kidney, liver and fat (perirenal) and the recoveries found were 70.25 ± 1.07% (RSD% = 1.52), 72.37 ± 3.6% (RSD% = 4.97) and 69.44 ± 2.22% (RSD% = 3.19), respectively. The limit of detection (LOD) for muscle tissue was found to be 2.0 μg kg⁻¹ and the limit of quantification (LOQ) 5.0 μg kg⁻¹. Revised: 4 and 24 January 2006     

Determination of Veterinary Pharmaceuticals in Production Wastewater by HPTLC-Videodensitometry

An SPE-HPTLC method for simultaneous identification and quantification of seven pharmaceuticals in production wastewater was optimized and validated. The studied compounds were enrofloxacine, oxytetracycline, trimethoprim, sulfamethazine, sulfadiazine, sulfaguanidine and penicillin G/procaine. The method involves solid-phase extraction on hydrophilic-lipophilic balance cartridges with methanol and HPTLC analysis of extracts on CN modified chromatographic plates followed by videodensitometry at 254 and 366 nm. Optimization of chromatographic separation was performed by systematic variation of the mobile phase composition using genetic algorithm approach and the optimum mobile phase composition for TLC separation was 0.05 M H₂C₂O₄:methanol = 0.81:0.19 (v/v). Linearity of the method was demonstrated in the ranges from 1.5 to 15.0 μg L⁻¹ for enrofloxacine, 100–500 μg L⁻¹ for oxytetracycline, 150–600 μg L⁻¹ for trimethoprim, 300–1100 μg L⁻¹ for sulfaguanidine and 100–400 μg L⁻¹ for sulfamethazine, sulfadiazine and penicillin G/procaine with coefficients of determination higher than 0.991. Mean recoveries ranged from 74.6 to 117.1% and 55.1 to 108.0% for wellspring water and production wastewater, respectively. Only sulfaguanidine showed lower results. The described method has been applied to the determination of pharmaceuticals in wastewater samples from pharmaceutical industry.     

Van Gogh’s Painting Grounds: Quantitative Determination of Bulking Agents (Extenders) Using SEM/EDX

A pre-concentration procedure using cloud point extraction is presented for the determination of uranium in natural water using molecular absorption spectrometry. The ligand used was 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. Interferences were eliminated using a masking solution containing trans-1,2-cyclohexanediaminetetraacetic acid (CDTA), sodium fluoride and sulphosalicylic acid. The optimization step was performed using a two-level factorial design and a Doehlert matrix, involving the factors pH, centrifugation time and buffer concentration. The method allows the determination of uranium in water samples with a detection limit of 0.15 μg L⁻¹, a quantification limit of 0.50 μg L⁻¹ and a precision expressed as relative standard deviation of 1.8 and 2.3% for uranium concentrations of 5 and 10 μg L⁻¹, respectively (n = 8). The accuracy was confirmed by analysis of two certified samples of natural water. This method was applied to the determination of uranium in superficial water samples collected at a uranium mine in Brazil. For five samples analyzed, the concentration of uranium varied between 1.1 and 18.1 μg L⁻¹. Tests of addition/recovery were performed for all these samples, and the results varying between 98 and 105% also proved that this procedure is not affected by the matrix and can be applied satisfactorily to the determination of uranium in water samples.     

Determination of proteins in human serum by combination of flow injection sampling with resonance light scattering technique

A flow injection method combined with Resonance light scattering detection was developed for the determination of protein concentration in human serum samples. This method is based on the enhanced RLS signals of protein binding with the dye acid chrome blue K. The enhanced RLS intensities at 264 nm, in an acidic aqueous solution, were proportional to the protein concentration over the range of 2.0–40.0 μg·mL⁻¹ for human serum albumin (HSA) and the limit of detection (3σ) is 85 ng·mL⁻¹. This method was successfully applied to the quantification of total proteins in human serum samples. The maximum relative standard deviation is less than 2% and the recovery is between 97 and 103% for the standard addition method. The sample throughput was 60 h⁻¹.     

Profile distribution of As(III) and As(V) species in soil and groundwater in Bozanta area

The profile distribution of arsenic(III) and arsenic(V) species in soil and groundwater was investigated in the samples collected in 2005 from a hand-drilled well, in the Bozanta area, Baia Mare region, Romania. The total content of arsenic in the soil was in the range of 525–672 mg kg⁻¹ exceeding 21–27 times the action trigger level for sensitive soil. 0.9–11.3 % of the total content was soluble in water, 83.0–92.6 % in 10 mol dm⁻³ HCl and 2.6–13.3 % was the residual fraction. Arsenic(V) was the dominant arsenic species in the soil in the range of 405–580 mg kg⁻¹. The distribution and mobility of arsenic species was governed by soil pH and contents of Al, Fe, and Mn. The mobility of arsenic(V) decreased with depth, while that of arsenic(III) was high at the surface and in the proximity of groundwater. The total concentration of arsenic in groundwater was (43.40 ± 1.70) μg dm⁻³, which exceeded the maximum contaminant level of 10 μg dm⁻³. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

Immobilization of Hexacyanoferrate on a Gold Self-Assembled Monolayer, and its Application as a Sensor for Ascorbic Acid

Hexacyanoferrate (II/III) (HCF) was immobilized on a gold electrode modified with cysteamine (CSTE). The Au/CSTE/HCF/PLL electrode was prepared with layer-by-layer (LBL) technique with HCF and poly-d-lysine (PLL). The Au/CSTE/HCF/PLL electrode presented the electrocatalytic activity for ascorbic acid oxidation. The maximum electrocatalytic current was reached at 0.28 V vs SCE in 0.01 mol L⁻¹ TRIS buffer, at pH 7.0. The Au/CSTE/HCF/PLL electrode response was stable under various oxidation–reduction cycles in TRIS medium, showing that the system is very stable. The solution pH has no effect on the anodic peak potential and anodic peak current in the range from 4 up to 10. The intensity of the anodic peak current varied with the concentration of ascorbic acid from 1 up to 910 μmol L⁻¹, with a sensitivity of 62.9 nA cm⁻² L μmol⁻¹, a detection limit of 0.65 μmol L⁻¹ and a quantification limit of 2.2 μmol L⁻¹. The developed sensor was successfully applied for ascorbic acid determination in pharmaceutical samples. The results compared to those obtained with a reference method were statistically the same with 95% of confidence level.     

Application of multivariate techniques for optimization of direct method for determination of lead in naphtha and petroleum condensate by electrothermal atomic absorption spectrometry

A direct method is proposed for the determination of lead in naphtha and petroleum condensate by electrothermal atomic absorption spectrometry (ET AAS) using palladium as a permanent modifier. The procedure includes the dilution of 3 mL of sample (naphtha or petroleum condensate) to a final volume of 10 mL with xylene, and direct injection of 30 μL of this solution into the graphite furnace. The optimization of the instrumental conditions was performed using multivariate techniques. Firstly, a 2³ full factorial design was performed for preliminary evaluation of the factors: pyrolysis time, pyrolysis temperature and atomization temperature. This experiment showed that in the studied levels only the factors pyrolysis time and atomization temperature were significant. Then, a 3² full factorial design was performed for the determination of the critical conditions of these variables. The method allows the determination of lead using the standard calibration technique with a calibration curve from 2.6 to 30 μg L⁻¹ (correlation coefficient higher than 0.998). A limit of detection (3σ) of 0.8 μg L⁻¹ and a characteristic mass of 35 pg were obtained in the presence of palladium as modifier. The precision expressed as relative standard deviation (RSD) was 1.5 and 0.8% for lead concentrations of 3.0 and 30 μg L⁻¹ (n = 10). Recovery studies demonstrate that lead can be determined in naphtha and petroleum condensate using calibration with organic standard solutions. This method was applied for the determination of lead in three petroleum condensate and two naphtha samples. The concentrations found for the petroleum condensate was between 2.7 and 5.7 μg L⁻¹, while the naphtha samples did not contain any detectable lead.     

A simple linear sweep voltammetric method for the determination of double-stranded DNA with malachite green

In pH 3.5 Britton—Robinson buffer solution double-stranded (ds) DNA can react with malachite green (MG) to form an interaction complex, which resulted in the decrease of the electrochemical response of MG, MG had a well-defined second-order derivative linear sweep voltammetric peak at −0.73 V (vs. SCE). After the addition of dsDNA into MG solution, the reductive peak current decreased with the positive shift of peak potential, which was the typical characteristic of intercalation. Based on the interaction, an indirect electrochemical determination method for dsDNA was established. The optimum conditions for the reaction were investigated and there were little or no interferences from the commonly coexisting substances. The decrease of peak current was linear with the concentration of dsDNA over the range of 0.8–12.0 μg cm⁻³ with the linear regression equation as ΔI _p″/nA = 91.70 C/(μg cm⁻³) + 74.55 (n = 10, γ = 0.990). The detection limit was calculated as 0.46 μg cm⁻³ (3σ). The method had high sensitivity and was further applied to the dsDNA synthetic samples with satisfactory result. The interaction mechanism was discussed with the intercalation of DNA-MG to form a supramolecular complex and the stoichiometry of the supramolecular complex was calculated by electrochemical method with the binding number 3 and the binding constant 2.35 × 10¹⁵ (mol dm⁻³)⁻³.     

Kinetics and the Mechanism of Iron(II) Reduction of cis-α-halogeno(cetylamine) (triethylenetetramine)cobalt(III) Complex Ion in Aqueous Acid Medium

The kinetics and mechanism of iron(II) reduction of cis- α-chloro/bromo(cetylamine)(triethylenetetramine) cobalt(III) surfactant complex ions were studied spectrophotometrically in an aqueous acid medium by following the disappearance of Co^III using an excess of the reductant under pseudo-first-order conditions: [Fe^II = 0.25 mol dm⁻³, [H⁺ = 0.1 mol dm⁻³, [μ = 1.0 mol dm⁻³ ionic strength in a nitrogen atmosphere at 303, 308 and 313 K. The reaction was found to be second order and showed acid independence in the range [H⁺ = 0.05−0.25 mol dm⁻³. The second order rate constant increased with Co^III concentration and the presence of aggregation of the complex itself altered the reaction rate. The effects of [Fe^II], [H⁺] and [ μ] on the rate were determined. Activation and thermodynamic parameters were computed. It is suggested that the reaction of Fe²⁺(aq) with Co^III complex proceeds by an inner-sphere mechanism.     

Liquid Chromatographic Analysis of Arabinosylcytosin and 1-β-D-Arabinofuranosyluracil in Treatment with Cyclophosphamide and Pirarubicin

A reversed-phase liquid chromatographic (RPLC) method has been developed for determination of arabinosylcytosin (Ara-C) and its metabolite 1-β-D-arabinofuranosyluracil (Ara-U) on a 250 mm × 4.6 mm i.d., 5 μm particle, Diamonsil C₁₈ column. The mobile phase was a mixture of 5% methanol and 95% 10 mmol L⁻¹ phosphate buffer adjusted to pH 5.5. The flow-rate was 1.0 mL min⁻¹ and the injection volume 20 μL. Eluting compounds were detected at 270 nm by use of an ultraviolet detector. Under these LC conditions cyclophosphamide (CTX) and pirarubicin (THP), two other medicines given with Ara-C in clinical treatment, do not interfere with measurement of Ara-C and Ara-U. Individual calibration plots of peak area against concentration generated from analysis of standard solutions were used to calculate the concentrations of Ara-C and Ara-U in sample solutions. The calibration plot was linear in the range 2.5–100 μg mL⁻¹, the average recovery of Ara-C and Ara-U was more than 98% (RSD < 2.5%), and between-day and within-day precision, expressed as relative standard deviation (RSD), were below 4.0%. LOQ for both Ara-C and Ara-U was 2 μg mL⁻¹. The method is rapid, simple, accurate and reproducible, and especially useful for application to patient samples.     

Determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples using hollow fiber-protected liquid-phase microextraction and high performance liquid chromatography

A new method based on hollow fiber-protected liquid-phase microextraction (LPME) was developed for the simultaneous determination of atrazine, desethyl atrazine and desisopropyl atrazine in environmental water samples. In LPME, analytes were extracted into 1-octanol immobilized in the micropores of a poly(vinylidene fluoride) porous hollow fiber membrane, and back extracted into the acceptor (4 M HCl) filled in the lumen of the hollow fiber. After LPME, the analytes trapped in the acceptor were analyzed with high-performance liquid chromatography after neutralization. The effect of extraction factors such as sample pH, acceptor pH, salinity, extraction time, stirring rate, and humic acid were studied. Under the optimized conditions, the limits of detection and relative standard deviations were respectively in the range of 0.5–1.0 μg L⁻¹ and 3.9–4.7% (n = 5). The proposed method was applied to determine atrazine, desethyl atrazine and desisopropyl atrazine in wastewater and groundwater samples. The three analytes were below the limits of detection, but good relative spiked recoveries over 90.1 ± 5.9% at 5 μg L⁻¹ spiked level were obtained.     

Rapid Separation on Activated Charcoal of High Oligosaccharides in Honey

A novel, simple and rapid stability-indicating high-performance liquid chromatographic (HPLC) method for pravastatin sodium (PRA) was successfully developed and validated for the assay of in tablets. Chromatographic separation was achieved isocratically on a C₁₈ column (150 mm × 4.6 mm) utilizing a mobile phase of methanol-phosphate buffer (pH 7; 0.02 M) (57:43, v/v) at a flow rate of 1.0 mL min⁻¹ with UV detection at 238 nm. A linear response (r = 0.9999) was observed in the range of 1–5 μg mL⁻¹. The method showed good recoveries (100.50%) and the relative standard deviation of intra and inter-day were 1.40%. The method can be used for both quality control assay of pravastatin in tablets and for stability studies as the method separates pravastatin from its degradation products and tablet excipients.An erratum to this article can be found at     

Determination of As(III) and total as in water by graphite furnace atomic absorption spectrometry after electrochemical preconcentration on a gold-plated porous glassy carbon electrode

Arsenic(III) was preconcentrated in a flow-through electrochemical cell on a gold coated porous carbon electrode. On stripping, arsenic was eluted with diluted nitric acid and determined off-line by GF AAS. The deposition and stripping steps were optimized. The limit of detection and limit of quantification were found to be 1.9 μg L⁻1 and 6.4 μg L⁻¹, respectively. The repeatability and reproducibility were found to be 5.3 % and 9.3 %, respectively. Total arsenic was determined after a microwave assisted chemical reduction of As(V) to As(III) making the procedure suitable for speciation analysis. The method was applied in analysis of water samples.     

HPLC determination of cefotaxime and cephalexine residues in milk and cephalexine in veterinary formulation

An HPLC method was developed and validated for the determination of the cephalosporins cefotaxime and cephalexine in skimmed bovine milk. The analytical column, Kromasil C₁₈ (250 mm × 4.0 mm, 5 μm) was operated at ambient temperature. Mobile phase consisted of CH₃OH-acetate buffer (pH = 4.0) and it was delivered isocratically at a flow rate of 1.0 mL · min⁻¹. Total analysis time was less than 5 min. Caffeine was used as internal standard (5 ng · μL⁻¹). UV detection was performed at 265 nm. Method validation was performed by means of intra-day (n = 5) and inter-day accuracy and precision (n = 8), sensitivity and linearity. Limits of detection (LOD) and limits of quantification (LOQ) were 0.1 and 0.3 ng · μL⁻¹, respectively. The method was applied to the analysis of a veterinary drug (CEPOREX) containing cephalexine. The results were quite accurate with the relative error varying from −8.0 to −3.5%. Solid-phase extraction was applied to remove all matrix interference from milk samples. High extraction recoveries (average 84–121%) were achieved by using Abselut NEXUS cartridges with acetonitrile as eluent and a rinsing step with water and n-butanol. A pre-concentration step was necessary in a 1/10 level to reach the EU MRL concentration level (100 μg · kg⁻¹). RSD values were less than 7% for both cephalosporins. Correspondence: Ioannis N. Papadoyannis, Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece