Analytical Chemistry Research最新文献

The electrochemical determination of aqueous paraquat PQ(II) by differential pulse voltammetry at a solid rotating silver electrode (RSE) is described. The aim of this work is to optimize all factors that can influence this determination. Potential wave forms, potential scan parameters and deposition time were examined for their effect on the paraquat peak shape and intensity. The best responses were obtained with differential pulse voltammetry in 0.1 mol L⁻¹ Na₂SO₄ as supporting electrolyte using amplitude 50 mV, scan increment 5 mV, deposition time 120 s, frequency 50 s⁻¹ and step amplitude 0.05 V. Electrochemical and mechanical surface cleaning, aimed at removing the amount of paraquat deposited onto the silver surface, were necessary for obtaining a good performance of the electrode. Response linearity, repeatability, accuracy and detection limit were also evaluated. The obtained detection limits were 7.1 × 10⁻⁹ mol L⁻¹ and 2.8 × 10⁻⁹ mol L⁻¹ for peak 1 and peak 2 respectively. The relative standard deviation (RSD) was found to be 1.19% in 1.0 × 10⁻⁴ mol L⁻¹ paraquat. The applicability of the RSE for PQ(II) determination in milk samples, without any sample pretreatment, was successfully demonstrated.

Benign prostatic hyperplasia (BPH) is one of the most common chronic diseases affecting men and it increases in both incidence and prevalence with age. This work presents a simple, sensitive and fast generic high performance thin layer chromatographic (HPTLC) method for the simultaneous determination of five drugs prescribed for the treatment of BPH. These drugs include the α₁-adrenergic blockers; alfuzosin hydrochloride (ALF), terazosin hydrochloride (TER), prazosin hydrochloride (PRZ) and doxazosin mesylate (DOX) in addition to the 5α-reductase inhibitor; finasteride (FIN). The cited drugs were separated on TLC-silica plates using a mobile phase composed of methylene chloride:n-hexane:methanol (8.8:0.3:0.9, by volume). Densitometric analysis was carried out at 254 nm for the α-blockers while FIN was measured at 220 nm. The five drugs were detected at R_f values of 0.26, 0.36, 0.45, 0.59 and 0.69 for ALF, TER, PRZ, DOX and FIN, respectively. The developed method was validated according to the International Conference on Harmonization (ICH) guidelines regarding; linearity, ranges, accuracy, precision, selectivity, robustness and limits of detection and quantification. The proposed method showed good linearity (r > 0.9990) in the ranges; 30–350, 30–350, 20–200, 30–350, 200–2000 ng/spot for the cited drugs, respectively. The applicability of the proposed method was verified through the analysis of laboratory-prepared mixtures and percentage recoveries between 98.27% and 101.97% were obtained. Commercial tablets were also analyzed by the developed methodology with no interference detected from the co-formulated excipients. The high sensitivity, simplicity and selectivity of the proposed method suggest its applicability for routine quality-control analysis purposes of any of the titled drugs in their pharmaceutical preparations.

Bisphenol A found in plastic vessels used for children feeding is an endocrine disrupting compound. Therefore it can also induce the obesity at a very early stage in the life of children, and its presence in children saliva should be checked. We proposed eight microsensors: four stochastic microsensors, one amperometric microsensor and three multimode microsensors for the screening of children saliva for bisphenol A in a concentration range from 10⁻¹⁵ to 10⁻⁴ mol/L. Qualitative assessment of bisphenol A in saliva samples was done using stochastic sensing, while its quantitative assessment was done using differential pulse voltammetry and stochastic sensing. The results correlated well, and also compared with those obtained using the standard method, although the standard method did not cover all the time the ranges on which bisphenol A is present in children saliva, and therefore the standard method cannot be reliable used for it analysis in children saliva.