Determination of Trichlorfon Pesticide Residues in Milk via Gas Chromatography with µ-Electron Capture Detection and GC-MS.

The pesticide trichlorfon is readily degraded under experimental conditions to dichlorvos. A method has therefore been developed by which residues of trichlorfon in milk are determined as dichlorvos, using gas chromatography with µ-electron capture detection. The identification of dichlorvos was confirmed by mass spectrometry. Milk was extracted with acetonitrile followed by centrifugation, freezing lipid filtration, and partitioning into dichloromethane. The residue after partitioning of dichloromethane was dissolved in ethyl acetate for gas chromatography. Recovery concentration was determined at 0.5, 1.0, and 2.0 of times the maximum permitted residue limits (MRLs) for trichlorfon in milk. The average recoveries (n = 6) ranged from 92.4 to 103.6%. The repeatability of the measurements was expressed as relative standard deviations (RSDs) ranging from 3.6%, to 6.7%. Limit of detection (LOD) and limit of quantification (LOQ) were 3.7 and 11.1 µg/l, respectively. The accuracy and precision (expressed as RSD) were estimated at concentrations from 25 to 250 µg/l. The intra- and inter-day accuracy (n = 6) ranged from 89.2%to 91% and 91.3% to 96.3%, respectively. The intra- and inter-day precisions were lower than 8%. The developed method was applied to determine trichlorfon in real samples collected from the seven major cities in the Republic of Korea. No residual trichlorfon was detected in any samples.

Electroantennography in the study of two stingless bee species (Hymenoptera: meliponini)

Relatam-se aqui os resultados preliminares de estudos eletroantenográficos realizados com duas espécies de Frieseomellita brasileira. Os experimentos com F. silvestrii e F. varia mostraram que as antenas respondem aos extratos obtidos com hexano das cabeças e dos abdômens das duas espécies e da tíbia posterior de F. silvestrii (que transporta resinas coletadas de plantas). Respondem também aos compostos puros, 2-heptanol e 2-nonanol, e aos terpenos, a-cubebeno, humuleno e b-cariofileno, encontrados nas tíbias e no cerume de seus próprios ninhos.

Comparative study of the cuticular hydrocarbon composition of Melipona bicolor Lepeletier, 1836 (Hymenoptera, Meliponini) workers and queens

In social insects, cuticular hydrocarbons are involved in species, kin, caste and nestmate recognition. Gas chromatography and mass spectrometry were used to compare the cuticular hydrocarbon composition of workers, males and queens of Melipona bicolor. The cuticular hydrocarbon composition of this species was found to consist mainly of C23, C25:1, C25, C27:1, C27, C29:1 and C29, which are already present in imagoes that have not yet abandoned the brood cell. This composition varied quantitatively and qualitatively between and within the castes and sexes. The newly emerged workers and young queens (virgins) had similar cuticular hydrocarbon profiles, which were different from those of the males. When the females start executing their tasks in the colony, the cuticular hydrocarbon profile differences appear. The workers have less variety, while the queens conserve or increase the number of cuticular hydrocarbon compounds. The queens have more abdominal tegumentary glands than the workers, which apparently are the source of the new cuticular compounds

Chemical ecology of triatomine bugs: vectors of Chagas disease.

Knowledge of chemical ecology of haematophagous triatomine bugs (Hemiptera: Heteroptera: Reduviidae) could be of practical value because this polyphyletic subfamily includes species of medical importance, such as vectors of Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), the aetiological agent of Chagas disease. For particular species of Dipetalogaster, Panstrongylus, Rhodnius and Triatoma, therefore, we review information on exocrine glands and products, interpreting their apparent roles as semiochemicals in the aggregation, alarm, defence, host-finding and sexual behaviour of these Triatominae.

Effects of the neem tree compounds azadirachtin, salannin, nimbin, and 6-desacetylnimbin on ecdysone 20-monooxygenase activity.

The effects of azadirachtin, salannin, nimbin, and 6-desacetylnimbin on ecdysone 20-monooxygenase (E-20-M) activity were examined in three insect species. Homogenates of wandering stage third instar larvae of Drosophila melanogaster, or abdomens from adult female Aedes aegypti, or fat body or midgut from fifth instar larvae of Manduca sexta were incubated with radiolabeled ecdysone and increasing concentrations (from 1 x 10(-8) to 1 x 10(-3) M) of the four compounds isolated from seed kernels of the neem tree, Azadirachta indica. All four neem tree compounds were found to inhibit, in a dose-dependent fashion, the E-20-M activity in three insect species. The concentration of these compounds required to elicit a 50% inhibition of this steroid hydroxylase activity in the three insect species examined ranged from approximately 2 x 10(-5) to 1 x 10(-3).

Clinical experience with leucovorin and 5-fluorouracil.

Two trials of leucovorin (LV) and 5-fluorouracil (5-FU) in patients with metastatic colorectal cancer were done, both using a 3-day loading dose and then weekly doses to minimize toxicity. The first trial used LV administered by intravenous infusion with a constant dose of 5-FU 400 mg/m2, and the second trail used oral LV with increasing doses of 5-FU. In the first trail, 45 eligible patients (20 with and 25 without previous therapy) were treated. Toxicity usually consisted of diarrhea or weakness and was controlled by delaying or decreasing the 5-FU dose. Subjective responses occurred in 75% of patients but did not correlate with antineoplastic effect. Objective responses were seen in 36% and stabilization of disease in 31% of patients; these correlated with prolonged survival. Median survival was 8 months for patients with previous treatment and 10 for those without. Twelve-month survival was 32% and 40%, respectively. There was no correlation between the development of toxicity and response or survival. The second trial was conducted recently in cooperation with Duke University to determine toxicity and efficacy of oral LV with intravenous 5-FU before a randomized trial of this combination versus placebo with intravenous 5-FU. Eighteen patients were treated, and serum levels of folates were obtained on ten. First toxicity occurred at 5-FU doses ranging from 375 to 850 mg/m2, and consisted of diarrhea in nine, lethargy in seven, nausea/vomiting in four, dermatitis in four, conjunctivitis in two, hypersalivation in two, stomatitis in one, and profound granulocytopenia in one. Response rate was 35%, and stabilization was 35% with median survival of 14 months. Twelve-month survival was 56%.

Clinical experience with CF-FUra.

Two trials of CF-FUra in patients with metastatic colorectal cancer were performed, both using a 3 day loading dose and then weekly maintenance doses to minimize toxicity. The first trial used CF by IV infusion with constant dose of FUra 400 mg/m2, and the second trial used oral CF with escalating doses of FUra. In the first trial, 45 eligible patients (20 with and 25 without prior therapy) were treated. Toxicity usually consisted of diarrhea or weakness and was controlled by delaying or decreasing 5FU dose. Subjective responses occurred in 75% of patients but did not correlate with antineoplastic effect. Objective responses were seen in 36% and stabilization of disease in 31% of patients, and correlated with prolonged survival. Median survival was 8 months for patients with prior treatment and 10 for those without, and 12 month survival was 32% and 40%, respectively. There was no correlation between the development of toxicity and response or survival. The second trial was recently conducted in cooperation with Duke University to determine toxicity and efficacy of oral CP with IV FUra prior to a randomized trial of this combination versus placebo with IV FUra. Eighteen patients were treated and serum levels of folates were obtained on 10. First toxicity occurred at FUra doses ranging from 375 to 850 mg/m2, and consisted of diarrhea in 9, lethargy in 7, nausea/vomiting in 4, dermatitis in 4, conjunctivitis in 2, hypersalivation in 2, stomatitis in 1, and profound granulocytopenia in 1. Response rate was 35% and stabilization was 35% with median survival of 14 months and 12 month survival of 56%.

The determination of steroids with and without natural electrophores by gas chromatography and electron-capture detection.

The response of the electron-capture detector to organic compounds is poorly defined, and the steroids are no exception to this observation. For those steroids which are naturally electron-capturing, the structures of the electrophores will be defined. Other steroids can be made electron-capturing by the formation of appropriate derivatives. Some new or infrequently used reagents for this purpose (flophemesyl ethers, t-bulflophemesyl ethers, pentafluorophenylhydrazone derivatives and halogen-substituted aromatic boronic acids) are described.

Comparison of high-performance liquid chromatography and gas chromatography for the analysis of ecdysteroids.

High-performance liquid chromatography (HPLC) with ultraviolet absorption detection, and gas chromatography (GC) with an electron-capture detector have been compared for their convenience in the analysis of ecdysteroids in invertebrate tissues. Analysis by HPLC on reversed-phase materials, including C18, C22 and CN bonded phases, was explored for the separation of both polar ecdysteroids and some of their possible biosynthetic intermediates of lower polarity. The HPLC method was found to be rapid and easy to use, but less sensitive than GC with electron-capture detection. The greater sensitivity and selectivity of GC was found to be important for the more difficult analyses.

Formation of pentafluorophenyldimethylsilylethers and their use in the gas chromatographic analysis of sterols.

The pentafluorophenyldimethylsilyl group is an excellent protecting group for steroid alcohols, giving volatile ethers, detectable at picogram levels in gas chromatography with an electron capture detector. By the use of five reagents, increasingly hindered hydroxyl groups can be protected, so that structural information about unidentified sterols can be obtained. Quantitative derivative formation for a wide range of hydroxyl groups is possible by selection of the correct reagent combination, without affecting unprotected enolizable ketones.