Trace element determination of Argentine wines using ETAAS and USN-ICP-OES.

The objective of this work was to develop a method to determine the metal content in wine samples from the province of Mendoza in Argentina. Ten samples of white wine and 10 samples of red wine available in the supermarket were analyzed for the metals aluminium, cadmium, calcium, chromium, copper, iron, nickel, lead and zinc by electrothermal atomic spectrometry (ETAAS) and ultrasonic nebulization was coupled to inductively coupled plasma optical emission spectrometry (USN-ICP-OES). The aluminium, cadmium, calcium, copper, iron, lead, zinc, chromium concentrations were between 17.0-18.0 microg l(-1), 1.0-4.7microg l(-1), 10.0-15.0 mg l(-1), 23.0-28.0 microg l(-1), 480-790 microg l(-1), 50-90 microg l(-1), 24-130 microg l(-1), and <0.2-6.25 microg l(-1), respectively. The levels compare well with those reported for similar wines from some other parts of the world. A significant aspect in this paper is the samples mineralization step, which allowed the direct determination of the metals. Concerning to the Cd determination, a refluxing digestion system was used for the pretreatment of the samples.     

Optimisation of parameters for determination of rubidium in spent CAPD fluids by flame and electrothermal atomic absorption spectrometry

An analytical procedure is reported for the determination of rubidium in spent continuous ambulatory peritoneal dialysis (CAPD) fluids by flame and electrothermal atomic absorption spectrometry (FAAS, ETAAS). Samples of spent CAPD fluids were collected as 5 ml aliquots in polyethylene tubes and stored in a freezer at -20 degrees C. Before analysis, samples were equilibrated to room temperature and analysed within 8 h. A total of 2 mg ml(-1) of caesium was added to each sample and standard solution to overcome interferences from ionisation. An air-acetylene flame was applied in FAAS determinations. Analysis was performed against aqueous standards. The calibration graph was linear from 30.0 up to 5000 microg l(-1) Rb, while the limit of detection (3 s) was found to be 20.0 microg l(-1) rubidium. Good repeatability of measurement (RSD 1%) was obtained. Parameters were also optimised for determination of rubidium in spent CAPD fluids by ETAAS. Ten-fold diluted samples (3.5% nitric acid) were analysed applying standard addition calibration. The calibration graph was linear from 2.0 up to 30.0 microg l(-1) rubidium, while the limit of detection (3 s) was found to be 1.0 microg l(-1) rubidium (sample volume 10 microl). Good repeatability of measurement (RSD 5%) was obtained. The results of direct determination by FAAS and ETAAS were compared to those obtained after acid digestion of samples in Parr bombs. The accuracy of the procedure for direct determination was checked by spiking samples. In 73% of samples analysed, the differences between the results obtained by the two techniques, either for direct determinations of samples or for samples digested in a Parr bomb did not exceed +/-10%.     

A flow-through optosensing device with fluorimetric transduction for rapid and sensitive determination of dipyridamole in pharmaceuticals and human plasma

A flow-through optosensor with fluorimetric transduction has been prepared for the sensitive and selective determination of dipyridamole in aqueous solutions and biological fluids. The method is based on a monochannel flow-injection analysis system using Sephadex QAE A-25 resin, placed into a Hellma 176-QS fluorimetric flow-through cell, as an active sorbing substrate. The native fluorescence of dipyridamole fixed on the solid sorbent is continuously monitored at wavelengths of 305 and 490 nm for excitation and emission, respectively. After obtaining the maximum fluorescence intensity, the eluent solution (KH(2)PO(4)/NaOH buffer solution, c(T)=0.05 mol l(-1), pH 6.0) is allowed to reach the flow cell, the analyte is removed, and the resin support is regenerated. When an NaOH (10(-4) mol l(-1))/NaCl (0.1 mol l(-1)) solution is used as carrier solution, at a flow-rate of 1.56 ml min(-1), the sensor responds linearly in the measuring range of 10-500 microg l(-1) with a detection limit of 0.94 microg l(-1) and a throughput of 22 samples per hour (300 microl of sample volume). The relative standard deviation for ten independent determinations (200 microg l(-1)) is less than 0.82%. The method was satisfactorily applied to the determination of dipyridamole in pharmaceutical preparations and human plasma.     

Photo-induced chemiluminometric determination of Karbutilate in a continuous-flow multicommutation assembly

The present paper deals with the chemiluminescent determination of the herbicide Karbutilate on the basis of its previous photodegradation by using a low-pressure Hg lamp as UV source in a continuous-flow multicommutation assembly (a solenoid valves set). The pesticide solution was segmented by a solenoid valve and sequentially alternated with segments of the 0.001 mol l(-1) of NaOH solution, the suitable media for the formation of photo-fragments; then it passes through the photo-reactor and was lead to the flow-cell after being divided in small segments which were sequentially alternated with the oxidizing system; 2 x 10(-5) mol l(-1) of potassium permanganate in 0.2% pyrophosphoric acid. The studied calibration range, from 0.1 microg l(-1) to 65 mg l(-1), resulted in a linear behaviour over the range 20 microg l(-1)-20 mg l(-1) and fitting the linear equation: I=(1180+/-30)C+(15+/-5) with the correlation coefficient 0.9998. The limit of detection was 10 microg l(-1) and the sample throughput 17 h(-1). After testing the influence of a large series of potential interfering species, the method was applied to water and human urine samples.     

A study of the determination of the hypertensive drug captopril by square wave cathodic adsorptive stripping voltammetry

In this work, the determination of captopril (CPL) was studied by square wave cathodic adsorptive stripping voltammetry (SWCAdSV) on a hanging mercury drop electrode (HMDE). CPL was adsorptively preconcentrated on the mercury surface as a sparingly soluble mercury salt under stirring of the solution and then the accumulated species was reduced by a cathodic square wave voltammetric scan. The reduction current was related to the CPL concentration in the sample. The chemical and instrumental parameters affecting the response were investigated and optimized for the CPL determination. The calibration curve was linear from 0.5 to 180 microg l(-1) of CPL (depending on the preconcentration time), the limit of detection at a S/N ratio of 3 was 0.5 microg l(-1) with 300 s of preconcentration and the relative standard deviation was 3.2% at the 20 microg l(-1) level (with 120 s of preconcentration, n=8). The method was applied to the determination of CPL in two pharmaceutical formulations with recoveries of 97.9 and 98.8%. Finally, the potential for applying the proposed method to the determination of CPL in biological media is briefly discussed.     

On-line preconcentration and determination of chromium in parenteral solutions by flow injection-flame atomic absorption spectrometry

An on-line chromium preconcentration and determination system implemented with flame atomic absorption spectrometry (FAAS) associated to flow injection (FI) was studied. For the retention of chromium, 4-(2-Thiazolylazo)-resorcinol (TAR) and Amberlite XAD-16 were used, at pH 5.0. The Cr-TAR complex was removed from the micro-column with ethanol. An enrichment factor of 50 was obtained for the preconcentration of 50 ml of sample solution. The detection limit value for the preconcentration of 50 ml of aqueous solution of Cr was 20 ng l(-1). The precision for ten replicate determinations at the 5 microg l(-1) Cr levels was 2.9% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for chromium was linear with a correlation coefficient of 0.9997 at levels near the detection limits up to at least 100 microg l(-1). The method was successfully applied to the determination of chromium in parenteral solution samples.     

A zucchini-peroxidase biosensor applied to dopamine determination

A biosensor modified with peroxidase from crude extract of zucchini (Cucurbita pepo) was developed for the determination of dopamine in pharmaceutical samples. This enzyme catalyses the oxidation of dopamine to dopaminequinone, in presence of hydrogen peroxide, which the electrochemical reduction can be followed at a peak potential of -0.02 V. The recovery of dopamine from the samples ranged from 94.8% to 106% and a rectilinear analytical curve for dopamine concentration from 5.0 x 10(-4) to 3.0 x 10(-3) mol L-1 (r=0.9982) was obtained. The detection limit was 2.6x10(-5) mol L-1 and the relative standard deviation was less than 1.2% for 7.9 x 10(-4) mol L-1 dopamine in 0.1 mol L-1 phosphate buffer solution at pH 6.0 (n=10).     

Determination of cadmium in wine by electrothermal atomic absorption spectrometry

A method is described for direct electrothermal atomic absorption spectrometric (ETAAS) determination of cadmium in untreated samples of wine. Pyrolytic graphite tubes and graphite tubes with standard L'vov pyrolytic platforms were tested as atomizers. The detection limit achieved was 0.08 microg L(-1) Cd in wine. The relative standard deviation for the concentration range from 0.2 to 10 microg L(-1) Cd ranged from 1 to 7%. The accuracy of the method was confirmed by comparing the current results with those found for wet digested wine samples and by the analysis of spiked samples. By applying the proposed method it was found that the cadmium concentration in Macedonian wines ranges from 0.10 to 0.90 microg L(-1).     

Determination of iron and molybdenum in a dietetic preparation by flame AAS after dry ashing

Methods for the determination of iron and molybdenum in a dietetic pharmaceutical preparation by flame atomic absorption spectrometry (FAAS) after dry ashing at 600 degrees C have been validated. Linearity, precision, accuracy, detection and quantification limits, specificity and robustness have been determined. Linearity of response was verified for concentrations ranging from 0.50 to 4.00 mg l(-1) of iron and 1.00 to 6.00 mg l(-1) of molybdenum. Precision of the methods, performed under conditions of repeatability and reproducibility, gave relative standard deviations of 0.4 and 1.1%, respectively, for the iron determination and of 1.0 and 6.5%, respectively, for the molybdenum determination. Mean recoveries determined after spiking dietetic preparation placebos ranged from 97.1 to 102.6% for iron and 95.2 to 102.9% for molybdenum. The limit of detection for iron was 126 microg g(-1) and for molybdenum 129 microg l(-1). Quantification limits were 420 and 433microg l(-1) for iron and molybdenum, respectively. No interference in the iron and molybdenum determination due to other components present in the dietetic capsules was found. Day-to-day and analyst-to-analyst variability was less than 1.1% for iron and 4.5% for molybdenum. Results show the suitability of the method for measurement of iron and molybdenum in a complex matrix sample such as a dietetic pharmaceutical preparation.     

Flow injection chemiluminescence determination of cefadroxil using potassium permanganate and formaldehyde system

A simple, rapid and precise flow injection chemiluminescence (FI-CL) method is proposed for the determination of cefadroxil and is suitable for application to other antibiotics containing phenolic hydroxyl groups. A possible mechanism for this selectivity is suggested. The method is based on the CL-emitting reaction between cefadroxil and potassium permanganate in sulfuric acid medium, enhanced by formaldehyde (HCHO). Under the optimum conditions, calibration graphs over the ranges of 0.05-0.8 and 1.0-10.0 microg ml(-1) were obtained. The proposed method was successfully applied to the determination of cefadroxil in pharmaceutical formulations with no evidence of interference from common excipients. The detection limit (3sigma) of this method is 25 ng ml(-1) (6.9 x 10(-8) mol l(-1)). The relative standard deviation was less than 2% for 0.4 and 4.0 microg ml(-1) cefadroxil (n = 20). The sample throughput was found to be 120 h(-1).     

19F NMR as a powerful technique for the assay of anti-psychotic drug haloperidol in human serum and pharmaceutical formulations

19F nuclear magnetic resonance was used as a suitable analytical tool for the identification and selective determination of haloperidol in human serum and pharmaceutical preparations. The method is based on the integration of appropriate signals of haloperidol and trifluoroacetic acid as an internal standard. The proposed method is a rapid and facile, while without any sample pretreatment, manipulation of large samples and lengthy instrument time. The regression equation for haloperidol in human serum showed a good linearity in the range of 60-600 microg ml(-1) with a detection limit of 1.4 microg ml(-1). The mean recovery results on human serum samples ranged from about 96-103%, with relative standard deviations <8%. The method was also applied successfully to the determination of haloperidol in real pharmaceutical samples, and compared with the results obtained by a reference method. The drug's degradation was studied by the proposed method in hydrochloric acid media and main products were identified.     

Simple spectrophotometric determination of acyclovir in bulk drug and formulations

A simple and cost effective spectrophotometric method is described for the determination of acyclovir in bulk drug and in formulations. The method is based on the formation of blue coloured chromogen when the drug reacts with Folin-Ciocalteu (F-C) reagent in alkaline medium. The coloured species has an absorption maximum at 760 nm and obeys Beer's law in the concentration range 50-450 microg ml(-1). The absorbance was found to increase linearly with increasing concentration of acyclovir, which is corroborated by the calculated correlation coefficient value of 0.9998 (n = 9). The apparent molar absorptivity and Sandell sensitivity were 1.65 x 10(2) l mol(-1) cm(-1) and 1.36 microg cm(-2), respectively. The slope and intercept of the equation of the regression line are 6.87 x 10(-4) and 8.33 x 10(-3), respectively. The limit of detection was 5.68 microg ml(-1) and the limit of quantification was 18.95 microg ml(-1). The proposed method was successfully applied to the determination of acyclovir in pharmaceutical formulations. The reliability of the assay method was established by parallel determination by standard-addition method, and by recovery studies. The results demonstrated and the procedure is at least as accurate, precise and reproducible (RSD < 2%) as the official method, while being simple and less time consuming. A statistical analysis indicated that there was no significant difference between the results obtained by the proposed procedure and those of the official method.     

基于溶解氧乙酰螺旋霉素极谱平行催化氢波的研究

目的提出一种极谱测定乙酰螺旋霉素(ASPM)的新方法。方法应用单扫描极谱法,在含溶解氧的0.1 mol·L^-1 NH₄Cl-NH₃·H₂O(pH 8.9)缓冲液中ASPM产生1个灵敏的平行催化氢波［峰电位E_p=-1.63 V(vs SCE)］。结果该平行催化氢波的二阶导数峰峰电流i″与ASPM浓度在1.74×10^-3～3.48 μg·mL^-1呈良好线性关系(r=0.997 9,n=13),检出限为5.80×10^-4 μg·mL^-1(3σ)。对0.871 μg·mL^-1 ASPM溶液进行13次平行测定,RSD为1.24%。结论本方法可用于ASPM片剂中ASPM含量的测定。     

HPLC determination and pharmacokinetic study of homoeriodictyol-7-O-beta-D-glucopyranoside in rat plasma and tissues

Homoeriodictyol-7-O-beta-D-glucopyranoside (HEDT-Glu) was isolated from Viscum coloratum and identified by MS, 1H- and 13C-NMR. A HPLC method was developed for determination of HEDT-Glu in rat plasma and tissues. All biological samples were pretreated by protein precipitation with acetone. Vanillin was selected as internal standard. The mobile phase consisted of methanol-water-glacial acetic acid (45 : 55 : 0.5, v/v/v). Good linearity were observed over the concentration ranges of 0.1-200.0 microg.ml(-1) in rat plasma and 0.05-5.0 microg.ml(-1) in tissues. Both intra- and inter-day precisions of HEDT-Glu, expressed as the relative standard deviation, were less than 13.1%. Accuracy, expressed as the relative error, ranged from -0.8 to 5.4% in plasma and from -5.6 to 9.4% in tissues. The mean extraction recovery of HEDT-Glu was above 73.17% in biological samples. The described assay method was successfully applied to the pre-clinical pharmacokinetic study of HEDT-Glu. After intravenous administration of HEDT-Glu to rat, AUC and CL(tot) were 16.04+/-3.19 microg.h.ml(-1) and 0.85+/-0.17 l.kg(-1).h(-1), respectively. T(1/2,alpha) and t(1/2,beta) were 0.06+/-0.01 h and 1.27+/-0.31 h, respectively. HEDT-Glu was cleared from the blood and mainly distributed to the liver and small intestine.     

Ochratoxin A in nephropathic patients from two cities of central zone in Portugal

Ochratoxin A (OTA) produced by Aspergillus and Penicillium genera contaminates several foods. OTA is nephrotoxic to all animal species studied so far, and most likely to humans, who show the longest half-life for elimination of this toxin among all examined species. OTA has other toxic effects such as teratogenicity, immunotoxicity, genotoxicity, and is also mutagenic and carcinogenic, all of which lead to life-threatening pathologies through several molecular pathways. A sensitive, specific and rapid method applying high performance liquid chromatography coupled to a spectrofluorimeter for the determination of ochratoxin A in human serum was validated. Serum samples were extracted with chloroform-orthophosphoric acid, and cleaned-up through immunoaffinity column (IAC). The separation and identification was performed by HPLC coupled to a spectrofluorimeter, and, after OTA methylation, the confirmation was achieved. Chromatographic separation of the analyte was performed on a reverse phase column with a mobile phase of water:acetonitrile:glacial acetic acid (49.5:49.5:1.0). Linearity was established between the range of 1 and 10 ng/ml. Under the optimized conditions, the recoveries were higher than 83.0% for all fortification levels. The intra-day precision oscillated between 8.0 and 5.0% at levels of 0.25 and 0.5 microg/l, while the inter-day precision was in the range of 10.7-16.0%. The limit of quantification of the method was 0.05 microg/l. The method is appropriate for quantitative determination of OTA in human serum and has been successfully applied to the analysis of OTA in haemodialysis patients from two principal cities of Portugal, in order to evaluate its exposure degree. Levels of OTA in Coimbra were higher than in Aveiro, 0.50 microg/l versus 0.49 microg/l. In respect to gender, levels of OTA were higher in males from Aveiro than in females, 0.52 microg/l versus 0.44 microg/l, and in Coimbra were similar, 0.50 microg/l versus 0.51 microg/l. However, in none of the cases, significant statistical differences were found.     

Optimal sample preparation conditions for the determination of uranium in biological samples by kinetic phosphorescence analysis (KPA)

Kinetic phosphorescence analysis (KPA) is a proven technique for rapid, precise, and accurate determination of uranium in aqueous solutions. Uranium analysis of biological samples require dry-ashing in a muffle furnace between 400 and 600 degrees C followed by wet-ashing with concentrated nitric acid and hydrogen peroxide to digest the organic component in the sample that interferes with uranium determination by KPA. The optimal dry-ashing temperature was determined to be 450 degrees C. At dry-ashing temperatures greater than 450 degrees C, uranium loss was attributed to vaporization. High temperatures also caused increased background values that were attributed to uranium leaching from the glass vials. Dry-ashing temperatures less than 450 degrees C result in the samples needing additional wet-ashing steps. The recovery of uranium in urine samples was 99.2+/-4.02% between spiked concentrations of 1.98-1980 ng (0.198-198 microg l(-1)) uranium, whereas the recovery in whole blood was 89.9+/-7.33% between the same spiked concentrations. The limit of quantification in which uranium in urine and blood could be accurately measured above the background was determined to be 0.05 and 0.6 microg l(-1), respectively.     

HPTLC screening assay for urinary cotinine as biomarker of environmental tobacco smoke exposure among male adolescents

For selective screening determination of urinary cotinine, i.e. (S)-1-methyl-5-(3-pyridyl)-2-pyrrolidinone, the major metabolite of nicotine, the high-performance thin-layer chromatographic (HPTLC) method have been proposed. Prior the final HPTLC analysis the procedure required a solid-phase extraction (SPE) of cotinine from collected urine samples with 1-methyl-2-pyrrolidinone as an internal standard. Densitometrical quantitation of cotinine on the chromatograms have been performed with a 16-grayscale scanner using the specialized software implemented on a desktop microcomputer. The lower detection limit of cotinine was 6 microg/l allowing the method to be applied for the measurement a concentration of this compound in urine samples collected from 35 elementary schoolboys exposed on both moderate and/or significant ETS. The mean recovery of cotinine from urine samples was 93%. The mean intra-day accuracy for the analysis of cotinine in range 6-750 microg/l. including four paralell measurements, was 2.9 %. The results of cotinine measurements by proposed SPE-HPTLC procedure were used in the pilot studies for assessment of hazard from home ETS on the health status of elementary schoolboys, especially an increased risk for infectious respiratory track diseases.     

Spectrophotometric method for the determination of nifedipine with 4-(methylamino)phenol and potassium dichromate

A new simple, sensitive and reproducible spectrophotometric method for the determination of nifedipine in pure and dosage forms has been proposed. It is based on the reduction of nifedipine with Zn/NNH4Cl, followed by coupling with N-methyl-1,4-benzoquinoneimine--the oxidation product of 4-(methylamino)phenol, to give a chromophore which absorbed maximally at 525 nm. The experimental conditions were optimised and Beer's law was obeyed over the concentration range of 5-175 microg ml(-1). The molar absorptivity, detection limit, recovery and RSD were found to be 1.9 x 10(3) l mol(-1) cm(-1), 1.1 microg ml(-1), 99.7-100.5% and 0.3-0.8%, respectively. The proposed method was compared favourably with the official B.P. method.     

Determination of arsenic in urine by atomic absorption spectrophotometry for biological monitoring of occupational exposure to arsenic.

An atomic absorption spectrophotometric (AAS) method was successfully applied to analysis of urine for arsenic (As) as a measure of biological monitoring of occupational exposure to As in Vietnam. The application of the method to urine samples from 75 non-exposed control urbanites (after 2-day abstinence from sea foods) gave a reference level of 62.4 +/- 11.6 microg/l (as mean +/- S.D.), from which the upper limit of the normal value (74 microg/l as mean +/- 1 S.D.) and the acceptable limit (100 microg/l as mean +/- 3S.D.) were deduced. Further application to urine samples from 147 workers occupationally exposed to As in Bacthai Non-ferrous Metallurgic Corporation showed significantly elevated levels of As in urine, with mean +/- S.D. of 78.5 +/- 20.2 microg/l. Improvement of working conditions to reduce As exposure resulted in substantial reduction in the ratio of those with urinary As at the level in excess of the acceptable limit. The practical importance of total arsenic determination in urine after 2-day sea food abstinence is discussed in connection with current conditions in analytical laboratories in Vietnam.     

Liquid chromatographic determination of fluoxetine

A simple, accurate and sensitive high pressure liquid chromatographic technique is described for the determination of fluoxetine in the capsule dosage form, human plasma and in biological fluid. Analysis is performed with a reversed phase-C18 column with ultraviolet detection at 228 nm. The isocratic mobile phase (1.5 ml/min.) consists of acetonitrile and triethylamine buffer (48 + 52, V/V). A linear calibration model (correlation coefficient 0.99863) was developed using pyridoxine as internal standard. The retention times were 2.10 and 3.20 min for pyridoxine and fluoxetine, respectively. The method was applied for the quantitation of fluoxetine in spiked human plasma samples. The detection limit is 5 microg/l and the absorbance varies with fluoxetine concentrations in the range (10-300) microg/l. The mean % recovery +/- S.D. was found to be 97.99% +/- 2.39. The proposed method was applied successfully for monitoring of fluoxetine in human plasma after single dose administration of one prozac capsule.