Separation of enantiomers of butorphanol and cycloamine by capillary zone electrophoresis

Butorphanol tartrate is a synthetic opioid agonist-antagonist used as analgesic, possessing three chiral centres in the basic part of the molecule. Its chiral purity is routinely controlled only by optical rotation. A new capillary zone electrophoresis method, capable to separate the enantiomers of butorphanol and intermediate of its synthesis, cycloamine, was developed. Different electrolyte composition (type and concentration of carrier ion, pH, and organic solvent addition), and type and concentration of several chiral selectors (natural and modified cyclodextrins) were tested. Using the optimized conditions (acidic electrolyte with the addition of highly sulphated gamma-cyclodextrin) as low as 0.05% of undesirable enantiomers can be detected. Selected method characteristics, i.e., linearity (0-50 mg/l), precision (2.5% at 20 mg/l), and accuracy (101 +/- 2% at 20 mg/l) were evaluated. The optimized method was applied for the analysis of real batches of butorphanol and cycloamine. It was found that butorphanol tartrate manufactured by IVAX Pharmaceuticals contains less than 0.05% of undesirable enantiomer.     

Evaluation of a reagent-injection flow injection technique for sample background absorption elimination: determination of chloride in cigarettes

The applicability of reagent-injection flow injection (FI) technique in elimination of background absorption was evaluated by using the FI determination of water-soluble chloride in cigarettes, based on the mercury thiocyanate method, as a model. Some parameters of the proposed reagent-injection FI method were optimized and the proposed procedure had a linear range of 0-7.5 mg l(-1) Cl, a detection limit of 0.02 mg l(-1) Cl, a sampling rate of 60 h(-1) and a relative standard deviation of 0.1% at 5 mg l(-1) Cl. Eight cigarette samples were analyzed by this proposed reagent-injection FI method and the referential membrane dialysis FI procedure. The relative errors were <4.3%, and paired t-test shows that there are no significant differences between these two methods. As no dialysis unit was needed, the reagent-injection FI method has much simpler flow system than the existed CFA and FI methods.     

Isotachophoretic determination of theanine

Free amino acids, the key quality components of tea, are contained in higher amounts in higher grade teas. Among free amino acids in tea, the content of theanine, which is the amino acid of the highest amount, shows high correlation to the price of green tea. A capillary isotachophoresis (CITP) method was developed for the analysis of L-theanine in tea and food supplements. The optimized electrolyte system was following: 0.01 mol/l HCl + 0.02 mol/l TRIS + 0.05% HEC (leading electrolyte), 0.01 mol/L-valine + barium hydroxide to pH 10 (terminating electrolyte). Good separation of L-theanine from other components of sample was achieved within 20 min. Method characteristics, i.e., linearity (0–200 mg/l), accuracy (99 ± 2 %), intra-assay (1.5 %), quantification limit (2 mg/l), and detection limit (0.7 mg/l) were determined. Sufficient sensitivity, low labouriousness (extraction only) and low running cost are important attributes of this method. It was proved that the developed method is suitable for the routine analysis of L-theanine in green tea and food supplements containing green tea extract.     

Catalytic-voltammetric determination of the antioxidant tert-butylhydroxyanisole (BHA) at a nickel phthalocyanine modified carbon paste electrode

The voltammetric behaviour of the antioxidant tert-butylhydroxyanisole (BHA), at a carbon paste electrode modified with the electron mediator nickel phthalocyanine, is described, and a method for the determination of this antioxidant, based on its oxidation on the modified electrode, is proposed. Cyclic voltammograms showed a well-defined oxidation peak for BHA slightly shifted towards less positive potentials with respect to that obtained at the plain carbon paste electrode. The peak current measured at the modified electrode is considerably higher than that obtained at the unmodified electrode. A modifier percentage of 2%, a methanol percentage of 2% and a 0.1 mol/HClO(4) medium were chosen as working conditions. The i(p)vs v1 2 plot obtained by linear sweep voltammetry showed a linear relationship over the whole scan rate range studied (5-2000 mV/sec) which is typical of a diffusion-controlled current. Using differential pulse voltammetry at DeltaE = 50 mV, linear calibration graphs were obtained in the concentration ranges 1.0-30.0, 0.10-1.0 and 0.02-0.10 mg/l BHA. The detection limit was 0.0036 mg/l (2.0 x 10(-8) mol/l). Interferences from other substances commonly present in commercial antioxidant mixtures were tested. The developed method was applied to the determination of BHA in spiked potato flakes.     

Simultaneous determination of Cr(III)-EDTA and Cr(VI) by ion interaction chromatography using a C18 column

The simultaneous determination of Cr(III) and Cr(VI) by ion interaction chromatography has been investigated. The mobile phase consisted of a 5 mM octylammonium orthophosphate at pH 4.0 with 35% (v/v) MeOH. The Nucleosil-100, C18 (5 microm, 250 x 4.6 mm) was used as the separating column and the component was detected at 200 nm. The separation of Cr(III) and Cr(VI) was based on anionic interaction. Since the Cr(III) did not exist as an anionic form like the Cr(VI) (Cr2O7(2-)) presented at the optimum condition, Cr(II) was firstly reacted with EDTA (1:40 mole ratio) to form the anionic complex prior to injecting into the chromatographic system. The characteristics of the method for separation of Cr(III)-EDTA and Cr(VI) were satisfactory. The wide linear range (0.3-50.0 mg l(-1)) was achieved. The repeatabilities (%R.S.D.) calculated from peak areas were 0.49% and 0.14%, detection limit (signal to noise ratio of 3) of 0.02 mg l(-1) and 0.3 mg l(-1) were obtained and the average of percent recoveries were found to be 98.5% and 99.6% for Cr(III) and Cr(VI), respectively.     

Determination of selenium in blood serum by inductively coupled plasma atomic emission spectrometry with pneumatic nebulization

The possibility of determining selenium in blood serum using inductively coupled plasma emission spectrometry with conventional pneumatic nebulization was studied. A high-resolution spectrometer (SBW=6 pm) with laterally viewed ICP was employed. Analysis with conventional pneumatic nebulization could overcome laborious and demanding digestion, which is necessary for hydride generation. A pressure digestion with nitric acid at 160 degrees C was sufficient to decrease the carbon content in the serum sample to 5%-10% of its original value. Spectral interference of the CN band was observed and mathematically corrected. It was found that the carbon-induced selenium line emission enhancement occurred even under ICP optimized conditions. A method of determination was developed and applied to the analysis of blood serum. True limit of detection in real samples is 0.01-0.02 mg/L and the limit of quantification (RSD 10%) is 0.03-0.07 mg/L using Se I 196.090 nm line at an integration time of 10-2 s. The method was tested by analysis of porcine blood serum and the serum reference material Seronorm MI 0181.     

Simultaneous determination of flucytosine and fluorouracil in human plasma by high-performance liquid chromatography

A validated, sensitive and precise reversed-phase high-performance liquid chromatographic method for the simultaneous determination of 5-flucytosine (5-FC) and 5-fluorouracil (5-FU) in human plasma is described. Two compounds, 5-methylcytosine (5-MC) and 5-chlorouracil (5-CU), were used as internal standards for the determination of 5-FC and 5-FU, respectively. Plasma samples were deproteinized with trichloroacetic acid and chromatographed on an octylsilica column, maintained at 30 degrees C during elution, using a 0.04 M phosphate buffer, pH 7.0, as eleunt. Spectrophotometric diode array detection was used at 266 nm. 5-FC, 5-FU, 5-MC and 5-CU were found to have retention times of 4.8, 5.8, 7.7 and 11.0 min respectively. Recoveries of 91-120% with reproducibility and repeatability coefficients of variation of 0.8-6% were obtained. Mean correlation coefficients of 0.99989 and 0.9995 were found for the linear calibration curves (n = 2) of 5-FC (4.816-192.6 mg/l) and 5-FU (0.05368-5.368 mg/l), respectively. The limits of quantitation were 0.3 mg/l for 5-FC and 0.05 mg/l for 5-FU.     

Analysis of residues of 81 pesticides on ginkgo leaves using QuEChERS sample preparation and gas chromatography/mass spectrometry

Pesticide residues on Ginkgo leaves are a safety concern. A fast and reliable method was developed for the analysis of 81 pesticides on Ginkgo leaves, which are pharmaceutically valuable. The method consists of a modified Quick, Easy, Cheap, Effective, Rugged, and Safe sample preparation method and GC/MS detection. Five sorbents (graphitized carbon black, primary secondary amine, amino, alumina, and Florisil) and two solvents (toluene and hexane) were optimized for the cleanup procedure. The LOD and LOQ ranged from 0.05 to 17.6 and 0.16 to 58.8 microg/kg, respectively. A majority of the pesticides (86-94%) gave satisfactory recoveries (70-110%), and 1-6% of the substances gave recoveries higher than 110% of the spiked concentration (n = 5) at 0.02, 0.05, and 0.1 mg/kg. Less than 5% of the substances showed recoveries lower than 70%. The method was proven to be repeatable with RSDs lower than 20%.     

Flow injection spectrofluorimetric determination of reserpine in tablets by on-line acetone sensitized photochemical reaction

On-line photochemical reaction of reserpine in the presence of acetone was investigated. Acetone was found to speed up the on-line photochemical conversion of reserpine into an intensively fluorescent compound. Not only reaction acidity but also the acetate buffer concentration affected the on-line photochemical induced fluorescence signal. Based on the observation an automated flow injection photochemical fluorimetric approach was developed. An injected sample zone was carried by a water stream to be merged with a acetate buffer (pH 3.4) solution containing 0.02% acetone in a knotted PTFE reactor (KR), which was freely coiled around a 6-W low pressure mercury lamp. While passing the KR, reserpine was transformed into an intensively fluorescent compound. It was on-line detected in a flow-through cell at the emission wavelength of 490 nm and excitation wavelength of 386 nm. At optimized conditions, a detection limit 0.45 mug l(-1) was achieved at a sampling rate of 90 h(-1). Eleven determinations of a 0.5 mg l(-1) reserpine standard solution gave a R.S.D. of 0.3%. The linear dynamic range of reserpine calibration curve was 0.01-0.75 mg l(-1). The proposed method was applied to assay the reserpine content in tablets and to monitor the dissolution profile of reserpine tablets. Satisfactory results were obtained for both the assays and dissolution studies.     

Validation and transferability study of a method based on near-infrared hyperspectral imaging for the detection and quantification of ergot bodies in cereals

In recent years, near-infrared (NIR) hyperspectral imaging has proved its suitability for quality and safety control in the cereal sector by allowing spectroscopic images to be collected at single-kernel level, which is of great interest to cereal control laboratories. Contaminants in cereals include, inter alia, impurities such as straw, grains from other crops, and insects, as well as undesirable substances such as ergot (sclerotium of Claviceps purpurea). For the cereal sector, the presence of ergot creates a high toxicity risk for animals and humans because of its alkaloid content. A study was undertaken, in which a complete procedure for detecting ergot bodies in cereals was developed, based on their NIR spectral characteristics. These were used to build relevant decision rules based on chemometric tools and on the morphological information obtained from the NIR images. The study sought to transfer this procedure from a pilot online NIR hyperspectral imaging system at laboratory level to a NIR hyperspectral imaging system at industrial level and to validate the latter. All the analyses performed showed that the results obtained using both NIR hyperspectral imaging cameras were quite stable and repeatable. In addition, a correlation higher than 0.94 was obtained between the predicted values obtained by NIR hyperspectral imaging and those supplied by the stereo-microscopic method which is the reference method. The validation of the transferred protocol on blind samples showed that the method could identify and quantify ergot contamination, demonstrating the transferability of the method. These results were obtained on samples with an ergot concentration of 0.02 % which is less than the EC limit for cereals (intervention grains) destined for humans fixed at 0.05 %.

Optimization of nonequilibrium liquid-phase microextraction for the determination of nitrobenzenes in aqueous samples by gas chromatography-electron capture detection.

In the present work, a novel method for the determination of nitrobenzenes in water has been described. It is based on nonequilibrium liquid-phase microextraction and gas chromatography-electron capture detection (GC-ECD). Extraction conditions such as solvent selection, organic solvent dropsize, stirring rate, content of NaCl and extraction time were found to have significant influence on extraction efficiency. The optimized conditions were 1.5 microl toluene and 20 min extraction time at 400 rpm stirring rate without NaCl addition. The linear range was 0.1 - 50 microg l(-1) for most nitrobenzenes. The limits of detection (LODs) ranged from 0.02 microg l(-1) (for 2.6-DNT) to 0.4 microg l(-1) (for NB); and relative standard deviations (RSD) for most of the nitrobenzenes at the 10 microg l(-1) level, except for 2,6-DNT in 3 microg l(-1), were below 10%. Natural samples collected from Miyun Reservoir and tap water samples from a laboratory were successfully analyzed using the proposed method, but none of the analytes were detected. The relative recoveries of spiked water samples (at the 10 microg l(-1) level except for 2,6-DNT in 3 microg l(-1)) were from 82.6 to 118.7%.     

整体柱在线固相微萃取-高效液相色谱同步富集检测水中的苯氧羧酸类除草剂

采用C18毛细管整体柱作为固相微萃取整体柱,构建在线固相微萃取-高效液相色谱联用系统,同步富集检测环境水样中的5种苯氧羧酸类除草剂。详细考察了联用系统运行条件对富集检测的影响。联用系统运行最佳参数为:固相微萃取整体柱长度20 cm,进样流速0.04 mL/min,进样13 min,洗脱流速0.02 mL/min,洗脱5 min。在最佳条件下,5种苯氧羧酸类除草剂的检出限为:9 μg/L (苯氧丙酸)、4 μg/L (2-(2-氯)-苯氧丙酸)、4 μg/L (2-(3-氯)-苯氧丙酸)、5 μg/L (2,4-二氯苯氧乙酸)、5 μg/L (2-(2,4-二氯苯氧基)丙酸)。与HPLC系统直接进样对比,联用系统对5种检测对象表现出优良的富集能力。5种苯氧羧酸类除草剂的回收率在79.0%~98.0%之间(RSD≤3.9%)。该方法成功应用于水样中5种苯氧羧酸类除草剂的检测,结果令人满意。     

Photochemical reactivity of sulfamethoxazole and other sulfa compounds with photodiode array detection

The photochemical activities of six sulfa compounds [sulfacetamide (CET), sulfadiazine (DIA), sulfaguanidine (GUA), sulfamerazine (MER), sulfamethoxazole (SMX), and sulfamethizole (MET)] under different experimental conditions such as photolysis time, solvent and buffer pH are investigated by photodiode array (PDA) spectrophotometry. With no photolysis, the sulfa drugs CET and DIA show no absorbance at 332 nm and the other compounds only modest absorbance. Upon photolysis for 4 min, absorbance enhancements at 332 nm of three to four times for GUA and MET and 12-15 times for SMX and MER are observed. For CET and DIA after photolysis, the (absorbance) l/mg is now approximately 0.01-0.02 units. Although two pH optima of approximately 3-4 and 7 are noted, the optimum solvent for photolysis is ethanol without pH adjustment. For flow injection (FI) with on-line photolysis and PDA detection, a mobile phase of 100% ethanol with a step flow rate from 0.1 to 1 ml/min is used providing a 4-min reaction time. The FI detection limit for SMX with photolysis at 330 nm is 1 mg/l. The relative standard deviation data (n=4) of seven individual points in a calibration curve from 5 to 150 mg/l are 0-4%. The recovery of SMX from pharmaceutical tablets is 99.7% indicating no interference from trimethoprim which is not photochemically active.     

Improved coupled-column liquid chromatographic method for the determination of glyphosate and aminomethylphosphonic acid residues in environmental waters

An existing method for the determination of glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) in water has been improved. It is based on precolumn derivatization with the fluorescent reagent 9-fluorenylmethylcloroformate (FMOC) followed by large-volume injection in a coupled-column LC system using fluorescence detection (LC-LC-FD). The derivatization step was slightly modified by changing parameters such as volume and/or concentration of sample and reagents to decrease the limits of quantification (LOQ) of glyphosate and AMPA to 0.1 microg/l. Additionally, the use of Amberlite IRA-900 for preconcentration of glyphosate, prior to the derivatization step, was investigated; the LOQ of glyphosate was lowered to 0.02 microg/l. Drinking, surface and ground water spiked with glyphosate and AMPA at 0.1-10 microg/l concentrations were analysed by the improved LC-LC-FD method. Recoveries were 87-106% with relative standard deviations lower than 8%. Drinking and ground water spiked with glyphosate at 0.02 and 0.1 microg/l were analysed after preconcentration on the anion-exchange resin with satisfactory recoveries (94-105%) and precision (better than 8%).     

High-performance liquid chromatographic determination of benzoylurea insecticides residues in grapes and wine using liquid and solid-phase extraction

A method for the determination of the benzoylurea insecticides diflubenzuron, triflumuron, teflubenzuron, lufenuron and flufenoxuron in grapes and wine by HPLC has been developed and validated. Grape samples (50 g) were homogenized and extracted with ethyl acetate-sodium sulfate and further cleaned-up by solid-phase extraction on silica sorbent. Wine samples (10 ml) diluted with water (1:3) were solid-phase extracted on an octadecyl sorbent using methanol as the eluent. The pesticides were separated on a reversed-phase octadecyl narrow-bore column by gradient elution and the residues were determined with a UV diode array detector. The calibration plots were linear over the range 0.05-5 micrograms/ml. Recoveries of benzoylurea pesticides from spiked grapes (0.02-2.0 mg/kg) and wine (0.01-0.2 mg/l) were 85.8-101.6% and 69.1-104.8%, respectively, and the limits of quantification for these insecticides were < 0.01 mg/kg for grapes and < 0.01 mg/l for wine. The method was applied to the determination of flufenoxuron and teflubenzuron residues in grapes from treated fields and in produced wine.     

Spectrophotometric determination of acid volatile sulfide in river sediments by sequential injection analysis exploiting the methylene blue reaction

This paper demonstrates the application of sequential injection analysis to perform sulfide determination using the methylene blue chemistry, based on two reagents: 3.63 mmol l(-1)N,N dimethyl-p-phenylene diamine hydrochloride in 1.1 mol l(-1) HCl solution and 19 mmol l(-1) FeCl(3), also in 1.1 mol l(-1) HCl. These solutions are aspirated inside the holding coil of the sequential injection system as two reagent zones sandwiching the sample zone. Under optimized conditions, the detection limit was calculated at 40 mug l(-1) S(2-), with a linear dynamic range from 0.05 to 2 mg l(-1) S(2-). This linear range can be extended up to 32 mg l(-1) using in-line dilution for sulfide concentrations greater than 2 mg l(-1). The robust characteristic of the SI system with syringe pump leads to very stable analytical curves (precision of 4%), minimizing the laborious preparation of sulfide standards. The method was applied in the determination of acid volatile sulfide in river sediments.     

Determination of Zidovudine in Pharmaceuticals by Differential Pulse Voltammetry

The zidovudine (AZT) has been extensively used in the treatment of HIV patients due to its antiretroviral activity. The quality control of this substance in drugs is of outstanding importance to public health because of its undesirable effects and short therapeutic interval. For the determination of AZT in pharmaceuticals, an alternative analytical methodology using voltammetry was developed. The reduction of AZT at a hanging mercury drop electrode (HMDE) is at ?0.96 V at pH 8.0. The influence of electroanalytical parameters, such as scan rate (20 mV/s), amplitude (50 mV), nature of the support electrolyte (phosphate buffer), and pH (8.0) on the voltammetric signal, was optimized. Under these optimized conditions, the AZT peak current varied linearly with its concentration from 0.25 to 1.25 mg/L (1 to 5 μM). Detection and determination limits of 0.0025 and 0.025 mg/L, respectively, and recovery of 99.88% with a relative standard deviation of 0.95% were obtained. The results obtained using this methodology in analyzing drugs containing AZT were compared favorably with those obtained by technique liquid chromatography as recommended by The United States Pharmacopoeia.     

Separation and determination of metallocyanide complexes of Fe(II), Ni(II) and Co(III) by ion-interaction chromatography with membrane suppressed conductivity detection applied to analysis of oil refinery streams (sour water)

A separation and determination method for the analysis of cyanometallic complexes of Fe(II), Ni(II) and Co(III) was developed to be applied to the analysis of petroleum refinery streams (sour water). Ion-interaction chromatography was used employing an analytical column IonPac NS1 10 microm and a chromatographic system ICS 2500 equipped with a membrane conductivity suppression ASRS ultra 4mm, both supplied by Dionex Corporation. The mobile phase was composed of 2 mmol l(-1) TBAOH, 1 mmol l(-1) Na(2)CO(3), 0.1 mol l(-1) NaCN and ACN (77:23, v/v), flowing at 0.7 ml min(-1). At the optimized conditions, detection limits estimated by the calibration curve parameters and relative standard deviation were: 0.002 mg CNl(-1) and 3.1% for Fe(CN)(6)(4-); 0.003 mg CNl(-1) and 2.5% for Ni(CN)(4)(2-) and 0.003 mg CNl(-1) and 2.8% for Co(CN)(6)(3-). Sour water samples without any pretreatment (except membrane filtration) from a petroleum refinery in Brazil were analyzed successfully by external calibration method.     

Production of Biopesticides in an In Situ Cell Retention Bioreactor

The seeds of Azadirachta indica contain azadirachtin and other limonoids, which can be used as a biopesticide for crop protection. Significant variability and availability of seed only in arid zones has triggered biotechnological production of biopesticides to cope up with its huge requirement. Batch cultivation of A. indica suspension culture was carried out in statistically optimized media (25.0 g/l glucose, 5.7 g/l nitrate, 0.094 g/l phosphate and 5 g/l inoculum) in 3 l stirred tank bioreactor. This resulted in 15.5 g/l biomass and 0.05 g/l azadirachtin production in 10 days leading to productivity of 5 mg l(-1) day(-1). Possible inhibition by the limiting substrates (C, N, P) were also studied and maximum inhibitory concentrations identified. The batch kinetic/inhibitory data were then used to develop and identify an unstructured mathematical model. The batch model was extrapolated to simulate continuous cultivation with and without cell retention in the bioreactor. Several offline computer simulations were done to identify right nutrient feeding strategies (with respect to key limiting substrates; carbon, nitrate and phosphate) to maintain non-limiting and non-inhibitory substrate concentrations in bioreactor. One such continuous culture (with cell retention) simulation was experimentally implemented. In this cultivation, the cells were propagated batch-wise for 8 days. It was then converted to continuous cultivation by feeding MS salts with glucose (75 g/l), nitrate (10 g/l), and phosphate (0.5 g/l) at a feed rate of 500 ml/day and withdrawing the spent medium at the same rate. The above continuous cultivation (with cell retention) demonstrated an improvement in cell growth to 95.8 g/l and intracellular accumulation of 0.38 g/l azadirachtin in 40 days leading to an overall productivity of 9.5 mg l(-1) day(-1).     

Sorption-spectrometric determination of lanthanum in the presence of uranium and thorium with the reagent Arsenazo M on the solid phase of fibrous filled sorbents

The possibility of the determination of La(III) in the presence of U(VI) and Th(IV), a solid phase with the reagent Arsenazo M, was examined. It was demonstrated that the determination of lanthanum with Arsenazo M in 0.05 M HCl in the presence of 3-, 2-, 1-, and 10-fold amounts of U(VI), Th(IV), Zr(IV), and Ti(IV) is possible after sorption on polyacrylonitrile fiber filled an ion exchanger with iminodiacetate groups (PANV-ANKB-50). For sorption under the optimum conditions at pH 5, the detection limit of lanthanum is 0.01 μg/mL. The method for the determination of lanthanum was verified by the added-found method in the analysis of tap water. To decrease the matrix effect, it is recommended to perform sorption in the analysis of water at pH 2.5. In this case, the detection limit of La(III) is 0.02 μg/mL, RSD < 20%. The time of the analysis of 5 or 6 samples is no longer than 20 min.