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ABSTRACT: A new analytical method, pressurized capillary electrochromatography with indirect amperometric detection, has been developed for the determination of some non-electroactive organophosphorus pesticides (OPPs). When 0.1 mmol L(-1) of 3,4-dihydroxybenzylamine (DHBA) was added to the mobile phase containing 50% v/v of ACN and 50% v/v of MES buffer (10 mmol L(-1), pH 5.5), and +0.9 V (vs. Ag/AgCl) of working potential were used, maximal signal levels of analytes could be achieved. A separation voltage of +10 kV, a column pressure of 7.0 MPa and a pump flow rate of 0.05 mL min(-1) were selected as the other optimal conditions for separation of six OPPs, namely, dimethoate, methyl parathion, ethyl parathion, chlorpyrifos, chlorpyrifos-methyl, trichlorfon. The OPPs could be separated within 15 min and determined with the detection limits ranging from 0.008 to 0.2 mg/kg. Combining with a solid phase extraction procedure, mean recoveries between 78.9 and 87.2% for vegetable samples and from 81.4 to 98.6% for fruit samples were obtained.
The Analyst 08/2010; 135(8):2150-6. · 4.23 Impact Factor
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ABSTRACT: A new method, pressurized CEC with end-column amperometric detection using carbon paste electrode, has been developed for the separation and determination of five phenolic xenoestrogens in chicken eggs and milk powder samples. Efficient separation of five analytes was performed by pressurized CEC using a mobile phase consisting of 60% v/v ACN and 40% v/v Tris buffer (5 mmol/L, pH 8.0), +6 kV of applied voltage and 7.0 MPa of supplementary pressure. Detection limits of 50, 5, 2, 10 and 20 ng/mL for pentachlorophenol, bisphenol-A, 2,4-dichlorophenol, 4-tert-octylphenol and 4-nonylphenol, respectively, were achieved using carbon paste electrode as working electrode and +0.8 V as detection potential. Matrix solid phase dispersion extraction method had been employed during sample preparation procedure, and mean recoveries ranged from 79.2 to 102.6% at different concentrations of phenolic xenoestrogens for spiked egg and milk powder samples were obtained.
Electrophoresis 02/2010; 31(6):1011-8. · 3.30 Impact Factor
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ABSTRACT: A method was developed to quantify domoic acid (DA), the chemical responsible for amnesic shellfish poisoning (ASP), by pressurized CEC (pCEC). The effect of different experimental conditions on the separation of DA and matrix solutes, such as the content of ACN in mobile phase, pH and concentration of buffer, supplementary pressure and applied voltage, were investigated. Under the optimal conditions, the pCEC method separated DA from shellfish matrices within 6 min. By using supplementary pressure, bubble formation in the capillary column was completely suppressed. The method was repeatable, sufficient accurate and sensitive for rapid screening of DA in shell seafood.
Journal of Separation Science 07/2009; 32(12):2117-22. · 2.73 Impact Factor
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ABSTRACT: MEKC was used in conjunction with end-column amperometric detection (AD) at a carbon disc electrode (0.3 mm diameter) for the selective and sensitive determination of melatonin and its five related indoleamines including its precursors and metabolites in the pineal gland. The introduction of a sample stacking technique in injection and the buffer additive SDS in the buffer solution system provided the rapid and sensitive analysis. Optimal buffer conditions (10 mmol/L phosphate containing 20 mmol/L SDS, pH 7.2), detection potential (+1.0 V vs. Ag/AgCl), and electrokinetic injection 10 s with the separation voltage of 24 kV were employed to achieve the baseline separation of six pineal hormones within 15 min. The peak currents and the analyte concentrations have a good linear relationship over the range of 6.0 x 10(-8) 6.0 x 10(-5 )mol/L. The detection limits for six pineal hormones by AD are 9.7 to 41.8 nmol/L (equal to 2.0 to 9.7 ng/mL) (S/N = 3), respectively. It is proved to provide about 30- to 250-fold improvement over UV, and be comparable with the sensitive fluorescence detection, which needs pre-column derivatization. The proposed method has been applied for analysis of melatonin and related indoleamines in rat pineal glands. A very simple sample pretreatment procedure, merely involving the homogenization step in perchloric acid, was enough to achieve recoveries in the range of 71 to 127% for all the analytes in the pineal gland.
Electrophoresis 12/2006; 27(21):4230-9. · 3.30 Impact Factor
