Method for determination of xanthene dyes in guava fruits and its application in a field dissipation study.

Xanthene dyes, i.e., phloxine B and uranine or phloxine B alone, are phototoxic to tephritid fruit flies infesting guava fruits. An analytical method was developed for determination of residues of these dyes used in bait solutions for suppression of the tephritid fruit fly population in guava fruits. The procedure involved solvent extraction, anion-exchange cleanup, and determination by liquid chromatography or capillary zone electrophoresis. The dyes were extracted from 50 g guava fruit at 45 degrees degrees with 400 mL methanol-acetonitrile (1 + 1) and 5 g magnesium oxide added as an alkaline and clarifying agent. The guava extract was adjusted to pH 8.5 and subjected to an amino column cleanup. Average recoveries of xanthene dyes added to guava purees ranged from 77 to 99% for phloxine B and from 79 to 102% for uranine at spiking levels of 0.05-1.00 microg/g. The method was applied to the determination of phloxine B residues in guava fruits collected from a dye-sprayed orchard. After phloxine B was applied at a rate of 62.5 g/ha for 14 weekly sprayings, it was found on guava fruits at an average concentration of 111 +/- 18 ng/g 4 h after the llth spraying. The concentration of phloxine B was 426 +/- 94 ng/g in selected fruits with high deposits of the dye 4 h after spraying. Average concentrations of phloxine B 5 days after the 7th and 14th sprayings were 29 +/- 7 and 19 +/- 8 ng/g, respectively.

Na(4)EDTA-Assisted Sub-/Supercritical Fluid Extraction Procedure for Quantitative Recovery of Polar Analytes in Soil.

Supercritical carbon dioxide (SC-CO(2)) is effective in extracting nonpolar and slightly polar chemicals from soils. However, pure SC-CO(2) is unsatisfactory for recovering polar chemicals in soils. A simple supercritical fluid extraction (SFE) procedure was developed to quantitatively recover polar and nonpolar chemicals from soils. The polar chemicals tested were aromatic acids and phenols. The nonpolar and slightly polar chemicals used as model compounds were common pesticides and environmental pollutants such as polycyclic aromatic hydrocarbons. The procedure required pretreatment of the samples with 15% water (g/g), 5% (ethylenedinitrilo)tetraacetic acid tetrasodium salt (Na(4)EDTA) (g/g), and 50% methanol (mL/g) prior to extractions using SC-CO(2) at 60 °C and 34.5 MPa. Recoveries ranged from 90 to 106% for the aromatic acids using the Na(4)EDTA-assisted SFE compared with only 7-63% recoveries of the corresponding chemicals when no Na(4)EDTA was used. The method quantitatively extracted 2,4-D and its close analogues aged in the soil for 2-30 days. The Na(4)EDTA-assisted SFE was also adequate for extracting phenolic analytes including picric acid and pentachlorophenol with recoveries from 85 to 104%. Na(4)EDTA is a good enhancer for extraction of the 29 analytes representing a wide range of polarity from the soil using SC-CO(2). The method is valuable for the analysis of parent pollutants and transformed products, particularly oxygen-borne metabolites in the environment.

Determination of phloxine B and uranine in water by capillary zone electrophoresis.

Phloxine B and uranine are color additives in drugs and cosmetics as well as potential photoactive insecticides. A capillary zone electrophoretic (CZE) method is developed to determine phloxine B and uranine in water. A fused-silica capillary (67 cm, 75-micron i.d.) and borate buffer are used. Migration of phloxine B and uranine increases slightly as the pH of the running buffer increases between the range of 8-9. Although there are only slight effects of ionic strength on the analyte migration in the range of 0-20 mM NaCl in the running buffer, the migration of phloxine B and uranine increases as the percentage of methanol in the samples increases. Methanol shows little effect on the quantitation of phloxine B and uranine. The CZE procedure is applied to determine phloxine B and uranine fortified in tap and stream water samples. Solid-phase extraction is employed to recover the analytes spiked in the water samples. Recoveries range from 87-112% for phloxine B spiked at 10-200 ppb in the tap and stream water. Uranine recoveries are 86-91% at fortification levels of 10-50 ppb in the water samples.