Rosario Brunetto

Levels of DDT residues in human milk of Venezuelan women from various rural populations

The levels of DDT residues were studied in 145 breast milk samples 25 days postpartum from women living in various rural populations where DDT has been used in farming activities and to interrupt malaria transmission. All participants showed quantifiable milk levels of DDT residues in the range from 5.1 to 68.3 micrograms/l and their levels significantly increased (P < 0.05) with maternal age. The determination of DDT residues (as DDE) in human milk was performed after a saponification process by gas chromatography with electron-capture detection. Confirmatory analysis was achieved using high-performance liquid chromatography with a diode array detection.

Time-based device used for the determination of tin by hydride generation flow injection atomic absorption techniques

Abstract A time-based device used in conjunction with flow injection hydride generation atomic absorption spectrometry for the determination of tin in biological materials is described. Its configuration was designed for minimal manipulation of the samples with the great advantage of using large volumes of diluted digests. In order to ensure the determination of the analyte directly in the sample digest, several acids were tested for their effect on stannane generation. A mixture of nitric acid and perchloric acid was found to be suitable in an acidity range of 0.5–2.0 mol l−1; addition of hydrogen peroxide has no effect on the results. Other experimental parameters such as sample and reagent concentrations and volumes, carrier gas flow rate as well as atomizer conditions were optimized by both the simplex and univariate optimization methods. The results were in good agreement. A linear calibration graph was obtained in the range 5–250 μg l−1 with a 3σ detection limit of 2.5 μg l−1. The relative standard deviations were 4.8 and 2.6% for 5 and 50 μg l−1 tin, respectively. The method was applicable with good accuracy to the determination of tin in some biological tissues.

Flow analysis–hydride generation–Fourier transform infrared spectrometry. A new analytical technique for the simultaneous determination of antimony, arsenic and tin

The combination of flow analysis (FA), hydride generation (HG) and Fourier transform infrared (FTIR) spectrometry is proposed as a novel and powerful analytical technique for the individual and simultaneous determination of antimony, arsenic and tin in aqueous samples. The analytes were transformed into the volatile hydride form by on-line reaction with sodium tetrahydroborate in acidic medium. The gaseous analyte hydrides [M(n)H(m), (g)] generated, were transported by means of a carrier gas stream inside the IR gas cell and the corresponding FTIR spectrum was acquired in a continuous mode. The 1893, 1904 and 2115 cm(-1) bands of the SbH3, SnH4, and AsH3 were selected for the determination of antimony, tin and arsenic, respectively. The limit of detection (3sigma) obtained by using a short-path (10 cm) IR gas cell were 0.25, 0.30 and 1.2 mg l(-1) for the determination of antimony, tin and arsenic, respectively; while the precision (relative standard deviation, RSD, n 5) found from a standard solution containing 50 mg l(-1) of each element was, in all cases, less than 0.3%. However, the use of a long-path (7.25 m) IR gas cell improved the figures of merit (sensitivity, limits of detection and quantification) nearly 60-fold. The effect of the main experimental and instrumental variables, such as acidic media, sodium tetraborohydrate concentration, nitrogen flow rate, nominal resolution and the scan accumulation on the analytical signals of the antimony, tin and arsenic hydrides, were studied. Further, the potential of the proposed technique for the simultaneous determination of these elements was tested, analyzing synthetic samples containing different amounts of Sb, Sn and As.

Organophosphorus pesticide residues in some watercourses from Mérida, Venezuela

The concentration of organophosphorus residues were determined in some Andean Highland watercourses from the Merida Provide of Venezuela. Level from < 0.3 to 16.5, < 0.1 to 12.2, <0.2 to 4.1 and <0.1 to 0.9 μg 1−1 ofdimethoate, diazinon, methyl parathion and methamidophos were found. The pesticides most frequently detected were dimethoate and diazinon (89% of samples), followed by methamidophos (39%) and methyl parathion (33%). In general, waters contained pesticide concentrations reflecting local usage derived from agricultural activities.