共查询到20条相似文献,搜索用时 46 毫秒
1.
《Electroanalysis》2004,16(4):311-318
A rapid multiresidue method has been developed for the analysis of eight pesticides (triazines, triazinones and ureas) in environmental waters. A simple end‐column electrochemical detector was used in combination with an available commercial capillary electrophoresis instrument with UV detection. The determination of these pesticides using micellar electrokinetic capillary chromatography (MEKC) with dual electrochemical and UV detection is the first time reported. In both detection systems, a linear range was obtained for the eight pesticides, concentrations lower than 5.0×10?5 mol L?1, in 0.020 mol L?1 boric acid at pH 8.3 and containing 0.025 mol L?1 of sodium dodecylsulfate, to obtain selectivity in the additional separation by micellar distribution process. Under these conditions a lower detection limit than 2.0×10?6 mol L?1 (0.15 pmol of pesticide) was achieved for the most of them. The eight pesticides are resolved in less than 14 min. 相似文献
2.
A simple end-column electrochemical detector was designed and attached to an available commercial capillary electrophoresis instrument with UV detection to detect different kind of herbicides and to determinate methyl-4-aminophenyl-sulfonylcarbamate (asulam) in water samples. The designed cell is very easy to assemble and disassemble in a short period of time; the working electrode positioning is also quickly achieved without micropositioners. The alignment between working electrode and capillary outlet was very reproducible for the all checked electrodes; the R.S.D. obtained was lower than 6.0% for 100 μm gap distance. In this mode, the non-electroactive and electroactive compounds could be detected by UV and electrochemical detection, respectively at the same time. The electrochemical determination of asulam using micellar electrokinetic capillary chromatography (MEKC) is the first time that is reported. In both detection systems, a linear range was obtained for asulam concentrations lower than 25.0 mg l−1, in boric acid 0.020 mol l−1 at pH 8.20 and containing 0.025 mol l−1 of sodium dodecyl sulfate, to obtain selectivity additional separation by the micellar distribution process. Under these conditions, an experimental detection limit of 0.4 mg l−1 was achieved. A new experimental scheme is also described for asulam determination in tap waters with a previous preconcentration step. Using both, UV and electrochemical detection, with a previous extraction procedure, the detection limits of asulam in tap water samples were of 1.0 and 0.8 μg l−1, respectively. 相似文献
3.
Summary A method has been developed for the determination of thirteen phenylurea herbicide residues in milk. It involves one-step solvent extraction of the milk with methanol by ultrasonication. The extract is cleaned up on an Amberchrom resin cartridge. Reversed-phase, gradient elution, high-performance liquid chromatography with UV detection at 242 nm is used to analyse the residues. The recovery of thirteen phenylurea pesticides is quantitative, ranging from 71.4% to 97.9% for the individual herbicides investigated at concentrations around 0.05 mg kg–1 and from 65.1% to 95.6% around 0.005 mg kg–1. The method is not associated with any of the emulsion problems common to conventional solvent extraction, which considerably reduce the sample clean-up process compared with existing methods. 相似文献
4.
Spectral and electrochemical studies have been carried out on the interaction of pefloxacin with calf thymus double-stranded dsDNA. The voltammetric behavior of pefloxacin was investigated at glassy carbon, carbon paste and dsDNA-modified carbon paste electrodes using cyclic voltammetry. Pefloxacin was oxidized, yielding one irreversible oxidation peak. The modification of the carbon paste surface with dsDNA allowed an accumulation process to take place for pefloxacin such that higher sensitivity was achieved compared with the bare surface. The response was characterized with respect to ionic strength, accumulation time, pefloxacin concentration, and other variables. The stripping differential pulse voltammetric response showed a linear calibration curve in the range 1.0×10–7–1.0×10–5 mol l–1
with a detection limit of 5.0×10–8 mol l–1 at the dsDNA modified electrode. The method was applied to the direct determination of pefloxacin in diluted urine samples. 相似文献
5.
A novel amperometric sensor and chromatographic detector for determination of parathion has been fabricated from a multi-wall carbon nano-tube (MWCNT)/Nafion film-modified glassy-carbon electrode (GCE). The electrochemical response to parathion at the MWCNT/Nafion film electrode was investigated by cyclic voltammetry and linear sweep voltammetry. The redox current of parathion at the MWCNT/Nafion film electrode was significantly higher than that at the bare GCE, the MWCNT-modified GCE, and the Nafion-modified GCE. The results indicated that the MWCNT/Nafion film had an efficient electrocatalytic effect on the electrochemical response to parathion. The peak current was proportional to the concentration of parathion in the range 5.0×10–9–2.0×10–5 mol L–1. The detection limit was 1.0×10–9 mol L–1 (after 120 s accumulation). In high-performance liquid chromatography with electrochemical detection (HPLC–ED) a stable and sensitive current response was obtained for parathion at the MWCNT/Nafion film electrode. The linear range for parathion was over four orders of magnitude and the detection limit was 6.0×10–9 mol L–1. Application of the method for determination of parathion in rice was satisfactory. 相似文献
6.
A flow-injection chemiluminescence (CL) method for the determination of pipemidic acid is described. It is based on energy transfer from excited state peroxynitrous acid to pipemidic acid, in which the excited state peroxynitrous acid is synthesized on-line by the mixing of acid hydrogen peroxide with nitrite in a flow system and the CL is from two excited states of pipemidic acid. The proposed method allows the measurement of pipemidic acid over the range of 2.0×10–7–2.0×10–5 mol l–1 . The detection limit is 6.3×10–8 mol l–1, and the relative standard deviation for 2.0×10–6 mol l–1 pipemidic acid (n= 9) is 0.9%. This method was evaluated by the analysis of pipemidic acid in pharmaceutical preparations. 相似文献
7.
Zhou H Huang Y Hoshi T Kashiwagi Y Anzai J Li G 《Analytical and bioanalytical chemistry》2005,382(4):1196-1201
Sinapine (O-sinapoyl choline) is a crucial component, with much medicinal value, of many dietary and medicinal plants. It has been found that sinapine gives an electrochemical response at a pyrolytic graphite electrode. The electrochemical properties of sinapine have been investigated. The peak current in the cyclic voltammogram is linear in the concentration range 1.9×10–6–2.5×10–4 mol L–1 and the limit of detection is 9.9×10–7 mol L–1. These properties can be applied to the determination of sinapine in extracts from three kinds of medicinal plant. The electrochemical method reported here is highly selective, sensitive, and stable. 相似文献
8.
The present paper describes the application of capillary electrophoresis in the micellar mode to the separation and quantitative determination of five phenylurea herbicides, viz. monuron, linuron, diuron, isoproturon, and monolinuron, in water samples. Using uncoated fused silica capillary and phosphate-borate buffer (pH 7.0) containing SDS, the five pesticides are resolved in less than 15 min and quantitatively determined by an ultraviolet detector at 244 nm. Method optimization and validation parameters are presented. Good linearity and repeatability were observed for all the compounds studied (correlation coefficients 0.999). The feasibility of the method developed was tested by simultaneous determination of these herbicides in environmental and drinking water samples at the minimum residue levels (MRLs) (0.1 μg/L) after solid-phase extraction (SPE) preconcentration procedure. 相似文献
9.
3-Amino-1,2,4-triazole (amitrole) is a widely used pesticide, with many difficulties to be analyzed at the regulatory level in drinking water, because its high solubility in water. This paper describes a simple and fast method for the simultaneous determination of amitrole and atrazin-2-hydroxy, principal degradation product of s-triazines, by capillary zone electrophoresis. Separation and determination of these herbicides in water samples was performed in 0.02 mol l−1 phosphate buffer at pH 3.2. The method allows determination of the amitrole and atrazin-2-hydroxy in water samples in concentration lower than 100 μg l−1. The detection limits using a previous preconcentration step of amitrole in Alberche River (Comunidad Autónoma de Madrid, Spain) and drinking water spiked samples was of 4 μg l−1. 相似文献
10.
A. Möller I. Helms G. Henze F. Scholz 《Fresenius' Journal of Analytical Chemistry》1993,345(8-9):567-569
Summary A determination of silicon is described which utilizes the selective extraction of molybdosilicic acid with methyl-iso-butyl-ketone. The extract is mixed with iso-propanol. No additional electrolyte is necessary because sufficient sulphuric acid is coextracted and provides good conductivity. The 3s-limit of detection was found to be 4×10–8 mol l–1 Si. The method was applied to determine silicon in cereals. 相似文献
11.
A fast and simple KMnO4-OP chemiluminescence system for flow-injection analysis of hydrogen peroxide is described. When a mixture of sample and OP is injected into acidic KMnO4, solution in a flow-cell, strong chemiluminescence occurs. The response is linear to the concentration of hydrogen peroxide in the range of 1.0 × 10–8 to 6.0 × 10–5 mol/l with 0.1 mol/l permanganate, and the upper limit of linear response could be extended to 6 × 10–3 mol/l by increasing the permanganate concentration. The relative standard deviation of the method is between 1.6 and 2.3%. The detection limit is 6.0 × 10–9 mol/l. This method is suitable for automatic and continuous analysis and has been successfully tested for determination of hydrogen peroxide in rain water. The chemiluminescence intensity was found to be remarkably enhanced in the presence of the OP micellar system. 相似文献
12.
Summary A simple multi-residue procedure has been developed and applied to the analysis of pesticides in groundwater samples from the Comunidad Valenciana, a predominantly agricultural area on the Mediterranean coast of Spain. The procedure includes a liquid-liquid extraction, after addition of NaCl on the samples, and a subsequent analysis by capillary gas chromatography using a dual detection system with electron capture and nitrogen-phosphorous detectors. This allows the determination of more than 30 compounds (organophosphorous, organochlorine and pyrethroid pesticides) at the low ppb (g l–1) levels. Detection limits obtained varied between 0.01 g l–1 (lindane, fonofos) and 0.5 g l–1 (cypermethrin). An additional injection of the sample extracts into a gas chromatograph equipped with a column of different polarity and electron capture detector is used for the confirmation of chromatographic peaks. The recommended procedure has been applied to 66 ground water samples. Pesticides, including organophosphorus and organochlorine compounds were detected in 31 of them, in levels ranging from 0.02 to 0.7 g l–1. 相似文献
13.
Portela DC Pereira IM Paíga P Delerue-Matos C Vaz MC 《Analytical and bioanalytical chemistry》2003,377(2):356-361
The work presented describes the development and evaluation of two flow-injection analysis (FIA) systems for the automated determination of carbaryl in spiked natural waters and commercial formulations. Samples are injected directly into the system where they are subjected to alkaline hydrolysis thus forming 1-naphthol. This product is readily oxidised at a glassy carbon electrode. The electrochemical behaviour of 1-naphthol allows the development of an FIA system with an amperometric detector in which 1-naphthol determination, and thus measurement of carbaryl concentration, can be performed. Linear response over the range 1.0×10–7 to 1.0×10–5 mol L–1, with a sampling rate of 80 samples h–1, was recorded. The detection limit was 1.0×10–8 mol L–1. Another FIA manifold was constructed but this used a colorimetric detector. The methodology was based on the coupling of 1-naphthol with phenylhydrazine hydrochloride to produce a red complex which has maximum absorbance at 495 nm. The response was linear from 1.0×10–5 to 1.5×10–3 mol L–1 with a detection limit of 1.0×10–6 mol L–1. Sample-throughput was about 60 samples h–1. Validation of the results provided by the two FIA methodologies was performed by comparing them with results from a standard HPLC–UV technique. The relative deviation was <5%. Recovery trials were also carried out and the values obtained ranged from 97.0 to 102.0% for both methods. The repeatability (RSD, %) of 12 consecutive injections of one sample was 0.8% and 1.6% for the amperometric and colorimetric systems, respectively. 相似文献
14.
The clinical manifestations of gout result from the formation and deposition of uric acid (UA) crystals. The monitoring of UA level in less invasive biological samples such as saliva is suggested for diagnosis and therapy of gout, hyperuricemia and the Lesch–Nyhan syndrome. In order to investigate the correlation between trace amounts of UA in human saliva and urine and explore the potential application in fast diagnosis of gout, capillary electrophoresis with electrochemical detection (CE–ED) was applied for the determination of UA in human saliva and urine in this work. Under the optimum conditions, UA and three coexisting analytes could be well separated within 14 min at the separation voltage of 14 kV in 80 mmol L–1 borax running buffer (pH 7.8). A good linear relationship was established between peak current and concentration of analytes over two orders of magnitude with detection limits (S/N=3) ranging from 1.09×10–7 to 5.0×10–7 mol L–1 for all analytes. This proposed method has been successfully applied for study of the correlation between the UA content of human saliva and urine, providing an alternative and convenient method for rapid diagnosis of gout. 相似文献
15.
为探索用电化学方法检测生物样品中氯霉素残留的高灵敏度技术,本实验研究了阳离子表面活性剂十六烷基三甲基溴化铵(CTMAB)对氯霉素在玻碳电极上伏安行为的影响,实验结果表明,以0.02 mol/L高氯酸为支持电解质,在0.40~-0.60 V的范围内进行伏安扫描时,2×10-5mol/L CTMAB能显著提高氯霉素在-0.41 V处的还原峰电流。利用这种改进的电化学方法检测氯霉素的线性范围为0.0026~8 mg/L,检出限达到0.83μg/L。研究了缓冲液种类及其酸碱度及其它表面离子活性剂等对测试氯霉素的影响。 相似文献
16.
The development of a fluorimetric method for the determination of zinc, based on the fluorescence of the zinc-8-(benzenesulphonamido) quinoline chelate in a micellar medium of sodium dodecylsulfate, is reported. The detection limit is 0.2 g l–1, the working range is 0.5–700 g l–1, and the sample throughput is 145 h–1. The method was evaluated for the determination of zinc in food samples.A batch procedure for the simultaneous determination of zinc and cadmium, based on the synchronous and derivative spectra, is also proposed. 相似文献
17.
B. Zygmunt H. B. Hanekamp P. Bos R. W. Frei 《Fresenius' Journal of Analytical Chemistry》1982,311(3):197-200
Summary A polarographic detector with a horizontal, fast dropping mercury electrode has been applied for the determination of thiols in physiological fluids. To establish suitable detection conditions first some basic studies on the polarographic behaviour of penicillamine, glutathione and cysteine were performed. This type of detection shows a high selectivity and reasonably low detection limits for sulphhydryl compounds. Detection limits of 6×10–7 mol l–1 for penicillamine and cysteine and 8×10–7 mol l–1 for glutathione were found. A good linearity has been observed over a concentration range of three orders. The detector has successfully been applied to the determination of penicillamine in urine and serum samples.
Dedicated to Prof. Dr. H. Weisz on occasion of his 60th birthday
On leave from the Technical University of Gdansk 相似文献
Bestimmung von Sulfhydrylverbindungen in physiologischen Flüssigkeiten durch Flüssigkeits-Chromatographie mit polarographischer Detektion
Zusammenfassung Ein polarographischer Detektor mit horizontaler, schnell tropfender Quecksilberelektrode wurde zur Bestimmung von Thiolen in physiologischen Flüssigkeiten angewendet. Zur Feststellung geeigneter Bedingungen wurden zunächst grundlegende Untersuchungen zum polarographischen Verhalten von Penicillamin, Glutathion und Cystein durchgeführt. Das Verfahren bietet hohe Selektivität und niedrige Nachweisgrenzen (6 · 10–7 mol/l für Penicillamin und Cystein, 8 · 10–7 mol/l für Glutathion). Linearität besteht über drei Größenordnungen. Der Detektor wurde mit gutem Erfolg für die Penicillaminbestimmung in Harn und Serum verwendet.
Dedicated to Prof. Dr. H. Weisz on occasion of his 60th birthday
On leave from the Technical University of Gdansk 相似文献
18.
Xiaohua Cai Kurt Kalcher Christian Neuhold Walter Goessler Irena Grabec Boidar Ogorevc 《Fresenius' Journal of Analytical Chemistry》1994,348(11):736-741
The voltammetric behaviour of a 2-mercaptoimidazole (2-MI) containing carbon paste electrode was studied. When mixed to carbon paste as an electrode modifier, 2-MI can be reduced at negative potentials (–1 V vs. SCE), but it does not give a response in the potential range where Ag(0) is oxidized to Ag(I). Silver could be accumulated from 0.1 mol l–1 acetate buffer onto a 2-MI modified carbon paste electrode without a potential applied; after medium exchange, it was reduced at –1 V vs. SCE in 0.1 mol l–1 acetate buffer solution and determined by differential pulse anodic stripping voltammetry. With suitable preconcentration times, the detection limit was 0.1 g l–1; a linear relation between current and concentration was found to exist within a range of 0.5 to 1000 g l–1. In the presence of EDTA, common metal ions have no or only little effect on the voltammetric determination of silver. 相似文献
19.
A method of capillary electrophoresis with wall-jet amperometric detection (AD) has been developed for separation and determination of l-tyrosine (Tyr) and its metabolites, such as Tyramine (TA), p-hydroxyphenylpyruvic (pHPP), homogentisic acid (HGA) and some dipeptides containing Tyr, such as Tyr-Gly-Gly (YGG), Tyr-Arg (YR) and Tyr-d-Arg (Y-d-R). A carbon disk electrode was used as the working electrode and the optimal detection potential was 1.00 V (versus Ag/AgCl). At 18 kV of applied voltage, the seven compounds were completely separated within 20 min in 110 × 10−3 mol/L Na2HPO4–NaH2PO4 buffer (pH 7.10) containing 3 × 10−3 mol/L β-cyclodextrin (β-CD). Good linear relationship was obtained for all analytes and the detection limits of seven analytes were in the range of 0.95–4.25 ng/mL. The proposed method has been applied to examine the metabolic process of l-tyrosine in rabbit's urine. 相似文献
20.
A novel chemically modified electrode is prepared on the basis of the attachment of multiwall carbon nanotubes (MWNTs) to the surface of a glassy carbon electrode (GCE) in the presence of a hydrophobic surfactant. The electrochemical behavior of tannins at the MWNTs-modified GCE is investigated. Tannins yield a well-defined oxidation at about 0.30 V (SCE) at the MWNTs-modified GCE. MWNT-film shows remarkable enhancement effect on the oxidation peak current of tannins. The experimental parameters are optimized, and a direct electrochemical method to detect tannins is proposed. The oxidation peak current is proportional to the concentration of tannins over the range from 4 × 10–7 to 2 × 10–4 M, and the detection limit is 1 × 10–7 mol/l after 5 min of accumulation. The relative standard deviation of 6% for determination of 2 × 10–6 mol/l tannins indicates excellent reproducibility. The analysis method is demonstrated by using tea and Chinese gall samples. 相似文献