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ABSTRACT: A gas chromatographic method for the determination of endocrine disruptor pesticides (Chlorpyrifos, Penconazole, Procymidone, Iprodione, Bromopropylate and Lambda-Cyhalothrin) in wine samples is described. A general DFG-S19 method for residual pesticide determination in all kind of food stuff was investigated to simplify and adopt for wine samples in this work. Alternative sample preparation routes were elucidated and compared according to their recovery values. Four different separation techniques were tested and the method employing florosil column after a LLE procedure was applied for wine samples with satisfactory recovery ratios (72-97%). The pesticides were extracted from the sample by cyclohexane-ethyl acetate mixture (1:1 v/v) and cleaned up by florosil column. The regression coefficients were at least 0.99 and relative standard deviations were no higher than 16%. Detection limits were in the range of 0.6-2.9ng/mL and the relative expanded measurement uncertainties were calculated in the 7-22% range.
Food Chemistry 05/2013; 138(1):54-61. · 3.65 Impact Factor
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ABSTRACT: A robust in house solid-phase micro extraction (SPME) surface has been developed for the headspace (HS)-SPME determination of endocrine disruptor pesticides, namely, Chlorpyrifos, Penconazole, Procymidone, Bromopropylate and Lambda-Cyhalothrin in wine sample by using sodium dodecylsulfate doped polypyrrole SPME fiber. Pyrrole monomer was electrochemically polymerized on a stainless steel wire in laboratory conditions in virtue of diminishing the cost and enhancing the analyte retention on its surface to exert better selectivity and hence the developed polymerized surface could offer to analyst to exploit it as a fiber in headspace SPME analysis. The parameters, mainly, adsorption temperature and time, desorption temperature, stirring rate and salt amount were optimized to be as 70°C and 45min, 200°C, 600rpm and 10gL(-1), respectively. Limit of detection was estimated in the range of 0.073-1.659ngmL(-1) for the pesticides studied. The developed method was applied in to red wine sample with acceptable recovery values (92-107%) which were obtained for these selected pesticides.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 04/2013; 929C:90-96. · 2.78 Impact Factor
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ABSTRACT: Present paper describes the results of a novel method which combines the Head space (HS) preconcentration of the analyte on the electrode prior to the voltammetric analysis. Thereafter, the method was called HS-Voltammetry. The performance of the method was tested upon using an electroactive and volatile molecule, phenol molecule, which gives an oxidation peak at conventional electrodes. In this study, a glassy carbon electrode was modified with polypyrrole by electropolymerization and then, the electrode was placed over the solution in a sealed vial heated gently on a hotplate with a stirrer for phenol determination. By controlling the thickness of the polymeric coating and optimizing preconcentration parameters such as vial pH and temperature, stirring rate and exposure time, a very consistent (5.2% at 5.0×10(-7) M) fraction of the analyte can be extracted during a predetermined time. The oxidation peak current at 0.8 V depended linearly on the phenol concentration over a wide range (3 orders of magnitude). The detection limit was estimated as 7.0×10(-8) M at 60 °C (S/N=3) which is well below the limit set by the European Community for phenols in wastewaters (ca. 5×10(-6) M). The effect of other phenolic compounds was also examined and it was shown that head space preconcentration eliminated the interference of non-volatile phenolic acids studied. For volatile phenolic compounds, the selectivity can be maintained in cases when isolated peaks are obtained for each component. The proposed method has been applied successfully for the determination of phenol in artificial wastewater and recovery percentage was calculated as 93%.
Talanta 08/2012; 98:34-9. · 3.79 Impact Factor
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ABSTRACT: A reliable method has been developed for the determination of Chlorpyrifos (CP) and its metabolite Chlorpyrifos-oxon (CPO) in wine sample using pulsed splitless technique coupled with gas chromatography by using electron capture detector. In this study, a quick, easy and cheap sample preparation method (QuEChERS) based on liquid extraction with acetonitrile, followed by dispersive solid phase extraction using primary secondary amine was tested for the separation and quantification of CP and CPO in wine samples. The accuracy of the developed method was tested upon recovery studies and it was calculated as (92.3 ± 18.2)% for CP and (96.6 ± 16.1)% for CPO. LOD and LOQ values of CP were found as 0.04 and 0.15 ng/mL and 0.49 and 1.62 ng/mL for CPO respectively. By using the pulsed splitless injection mode, the sensitivity of the determination of CP and its metabolite CPO in wine samples was improved compared to splitless technique. CP content of analyzed wine sample was found as 2.05 ± 0.15 ng/mL with a RSD of 7.6% and CPO content was found as 4.99 ± 0.15 ng/mL with a RSD of 3.0% (n=3). The expanded measurement uncertainties were calculated as 17% and 6% for CP and CPO, respectively.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 07/2012; 904:35-41. · 2.78 Impact Factor
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ABSTRACT: The effect of centrifugation on the voltammetric behavior of mercury on a gold film electrode was investigated. Mercuric ion
was reduced with borohydride to form metallic mercury droplets which were collected on a gold film electrode with the aid
of centrifugal force without a carrier material. A special cell was constructed for this purpose. The effect of the amounts
of reducing agent, stripping solution, time and speed of centrifugation on the anodic stripping peaks resulting from the re-oxidation
of mercury were investigated. The calibration graph for mercury(II) has a regression coefficient of 0.9941; its linear range
is from 3.0pM to 10.0nM. Due to the effect of accumulation, the detection limit of mercury(II) is as low as 3pM.
Microchimica Acta 04/2012; 167(3):225-230. · 3.03 Impact Factor
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ABSTRACT: A new method for the determination of traces of total mercury by using a gold film electrode in salt samples was developed. Table salts are known to contain mercury at ultra-trace level as well as a high quantity of chloride ions that cause severe disturbance during the stripping step when gold is used as the electrode material in voltammetric measurements. The interference of high chloride content in the determination of mercury was eliminated by reducing its concentration down to 3 x 10(-3) mol L(-1) level which is optimum for the determination by using on-line medium exchange procedure immediately after the deposition step. The deposition potential applied to the electrode was maintained at 0.2 V (vs. Ag/AgCl double junction electrode) while the cell content was sucked by a pump and replaced with fresh electrolyte simultaneously. The analyte loss resulted from the air contact of the electrode was prevented by this means. The mercury ions present in the salt samples were collected at +0.2 V for 60 s, the electrolyte was replaced by 0.1 mol L(-1) HClO4 and the potential was scanned, attaining a detection limit of 0.17 microg L(-1), with R.S.D. of 1.2% (S/N=3). The recovery of the method was 94.6%. The performance and accuracy of the method was compared with that of atomic fluorescence spectrometry (AFS). Consequently, this developed method can offer a wide range of application in saline samples.
Talanta 05/2008; 75(2):442-6. · 3.79 Impact Factor
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ABSTRACT: Centri-voltammetry is a novel method, which allows combining the advantages of centrifugation and voltammetry. The method offers a practical way for application of coprecipitation in trace analysis allowing direct voltammetric scan hence prevents the loss of the analyte, which usually is the case for other preconcentration techniques. The performance of the method was successfully tested using trace amounts of Pb(2+) ions in aqueous solution in a vessel specially designed to be compatible to both centrifugation and voltammetry. XAD-7 resin was used as the carrier material and the parameters related to the carrier material and medium characteristics as well as the centrifugation settings were investigated. The sensitivity of the method was found comparable to that of stripping techniques and the detection limit for lead ions was calculated as 5.2 x 10(-9)M with mercury coated gold sphere electrode. The precision of the method depends on the configuration of the working electrode and better reproducibility was obtained with mercury coated plate electrodes (R.S.D. 3.3%, n = 6).
Talanta 02/2005; 65(1):48-53. · 3.79 Impact Factor
