Placental transfer of DDT in mother-infant pairs from Northern Thailand.

The present study objective was to investigate ratios and correlation coefficients between dichlorodiphenyltrichloroethane (DDT) compounds in cord and maternal sera of mother-infant pairs from northern Thailand. The study site was located in Chiang Dao District of Chiang Mai Province which was an agricultural and former malaria endemic area. DDT compounds were analyzed in 88 cord and maternal serum samples using gas chromatography-electron capture detection (GC-ECD). p,p'-DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene) was the major component and detected in every cord and maternal serum samples with geometric means of 1,255 and 1,793 n g(-1) lipids, respectively. p,p'-DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) was detected at 89.8 and 100% of cord and maternal serum samples, respectively. The second and third highest levels detected were p,p'-DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane) and p,p'-DDT, respectively. The ratios between cord and maternal sera for p,p'-DDE, p,p'-DDT, and p,p'-DDD that were less than 1 had high correlation coefficients (ratio = 0.70, r = 0.82 for p,p'-DDE, ratio = 0.62, r = 0.66 for p,p'-DDT, and ratio = 0.79, r = 0.78 for p,p'-DDD). The high correlation coefficients indicate that cord serum levels of DDT compounds could be accurately estimated from maternal serum levels. It can be concluded that cord serum levels of p,p'-DDE, p,p'-DDT, and p,p'-DDD were approximately 70%, 62%, and 79% of maternal serum levels, respectively. Furthermore, our findings can be applied in public health to monitor and evaluate risk among infants from high DDT exposure area.

Optimization of high-performance liquid chromatographic parameters for the determination of capsaicinoid compounds using the simplex method.

A high-performance liquid chromatographic method was developed for the analysis of capsaicinoid compounds, the pungent principles of capsicum fruits. A sequential simplex method was applied to optimize the chromatographic response function used to assess the quality of separation by varying the chromatographic parameters. The separation was achieved in 11 min using a C-8 column of 15-cm length and 4.6 mm diameter using a UV detector. A flow rate of 1.15 ml min(-1) at a column temperature of 43.5 degrees C using 63.7% methanol in water gave the most efficient separation. The method was found to be suitable for the determination of the major capsaicinoid compounds in the capsicum samples.

Design and fabrication of a low-cost flow-through cell for the determination of acetaminophen in pharmaceutical formulations by flow injection cyclic voltammetry.

A low-cost electrochemical flow-through cell is designed and fabricated to use in conjunction with a flow injection (FI) system. This detector cell used a centrosymmetric radial flow thin-layer geometry with a stainless steel auxiliary electrode and a reference electrode (Ag/AgCl) without a salt bridge. The 5H pencil lead electrode used as a working electrode in the home-made cell is an extremely inexpensive electrode which performs as well as the expensive commercial glassy carbon electrode. Optimum conditions for determining acetaminophen using the proposed FI manifold was investigated. Appropriate volume of sample and/or standard solution containing acetaminophen in pH 2.2 Mcllvaine buffer solution was injected into the proposed FI system and mixed with the flowing stream of supporting electrolyte (pH 2.2 Mcllvaine buffer solution) at an optimum flow rate of 1 mlmin(-1). The cyclic voltammograms were recorded over the potential range from -0.5 to +2.0 V with a scan rate of 40 mVs(-1). Linear calibration curve over the range of 0.1-5 mM acetaminophen was established with the regression equation Y=3.68X+1.0157 (r(2)=0.9964). The recommended method has been applied to the determination of acetaminophen in 8 commercial pharmaceutical preparations. The percentage recoveries of the spiked acetaminophen in four tablet samples were ranging from 103 to 112 with the relative standard deviation in the range of 0.1-1.3%.

Exploiting flow injection and sequential injection anodic stripping voltammetric systems for simultaneous determination of some metals.

Flow injection (FI) and sequential injection (SI) systems with anodic stripping voltammetric detection have been exploited for simultaneous determination of some metals. A pre-plated mercury film on a glassy carbon disc electrode was used as a working electrode in both systems. The same film can be repeatedly applied for at least 50 analysis cycles, thus reducing the mercury consumption and waste. A single line FI voltammetric system using an acetate buffer as a carrier and an electrolyte solution was employed. An injected standard/sample zone was mixed with the buffer in a mixing coil before entering a flow cell. Metal ions were deposited on the working electrode by applying a potential of -1.1 V vs Ag/AgCl reference electrode. The stripping was performed by anodically scanning potential of working electrode to +0.25 V, resulting a voltammogram. Effects of acetate buffer concentration, flow rate and sample volume were investigated. Under the selected condition, detection limits of 1 mug l(-1) for Cd(II), 18 mug l(-1) for Cu(II), 2 mug l(-1) for Pb(II) and 17 mug l(-1) for Zn(II) with precisions of 2-5% (n=11) were obtained. The SI voltammetric system was similar to the FI system and using an acetate buffer as a carrier solution. The SI system was operated by a PC via in-house written software and employing an autotitrator as a syringe pump. Standard/sample was aspirated and the zone was then sent to a flow cell for measurement. Detection limits for Cd(II), Cu(II), Pb(II) and Zn(II) were 6, 3, 10 and 470 mug l(-1), respectively. Applications to water samples were demonstrated. A homemade UV-digester was used for removing organic matters in the wastewater samples prior to analysis by the proposed voltammetric systems.