Search results for "insecticide"

Determination of carbamate residues in fruits and vegetables by matrix solid-phase dispersion and liquid chromatography-mass spectrometry.

2000

Abstract Thirteen carbamates were analysed in orange, grape, onion and tomatoes by matrix solid-phase dispersion (MSPD) followed by liquid chromatography–mass spectrometry (LC–MS). Electrospray (ES) and atmospheric pressure chemical ionisation (APCI) were compared and both gave similar results in terms of sensitivity and structural information because at 20 V fragmentor voltages the fragmentation is minimal. The efficiency of different solid-phases (C18, C8, cyano, amine and phenyl) for the MSPD was compared. Mean recoveries using C8 varied from 64 to 106% with relative standard deviations of 5–15% in the concentration range of 0.01–10 mg kg−1. Matrix constituents did not interfere signific…

Analysis of organophosphorus pesticides in honeybee by liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry.

2001

Pesticides applied in extended agricultural fields may be controlled by means of bioindicators, such as honeybees, in which are the pesticides bioaccumulate. Liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) experiments with positive (PI) and negative (NI) ion modes were optimized for the analysis of 22 organophosphorus pesticides in honeybee samples. The extraction required 3 g of sample, which was extracted with acetone. The extract was purified with coagulating solution and reextracted with Cl(2)CH(2). Pesticides studied could be detected by both ionization modes except for parathion, parathion-methyl, and bromophos, which did not give signals …

Determination of organophosphorus pesticides in honeybees after solid-phase microextraction.

2001

A method based on solid-phase microextraction (SPME) followed by gas chromatography with nitrogen-phosphorus detection was developed for the purpose of determining 18 organophosphorus pesticide residues in honeybee samples (Apis mellifera). The extraction capacities of polyacrylate and poly(dimethylsiloxane) fibers were compared. The main factors affecting the SPME process, such as the absorption time profile, salt, and temperature, were optimized. The method involved honeybee sample homogenization, elution with an acetone:water solution (1:1) and dilution in water prior to fiber extraction. Moreover, the matrix effect on the extraction was evaluated. In samples spiked at the 0.2 mg kg(-1) …

Determination of abamectin in citrus fruits by liquid chromatography-electrospray ionization mass spectrometry.

2000

Liquid chromatography coupled to electrospray mass spectrometry (LC-ES-MS) with positive ion detection was used to determine abamectin in oranges. MS conditions were optimized to achieve maximum sensitivity. The main ion for abamectin was [M+Na]+ at a fragmentor voltage of 180 V. Abundant structural information can be obtained at different fragmentor voltages. The detection limit for the standard solution was 12 pg injected, and good linearity and reproducibility were observed. Abamectin residues were extracted using matrix solid-phase dispersion. Orange samples were homogenized with C18 bonded silica placed onto a glass column and eluted with dichloromethane. Recoveries of the abamectin fr…

Organochlorinated pesticides in sediments from the Lake Albufera of Valencia (Spain).

2005

Bottom sediment samples from 121 sites of the Lake Albufera of Valencia were analyzed. Dieldrin, endrin, heptachlor and op'-DDT were not detected (0.01 ng g(-1)) in 88-93% of the sites. Aldrin and HCB concentration ranges were between0.01 and 0.1 ng g(-1) in 86% and 94% of the sites, respectively. Heptachlor-epoxide and lindane 95% confidence intervals were 0.2-0.5 and 0.06-0.12, respectively. The greatest average concentration corresponds to pp'-DDE, pp'-DDD and pp'-DDT. The sum of six isomers and derivatives of the DDT average concentration reaches 2.1 ng g(-1), as opposed to 2.7 ng g(-1) for the sum of 13 pesticides considered. In the site with a major contamination, 27.0 ng g(-1) of pp'…

Simultaneous clean up of fish fat containing low levels of residues and separation of PCB from chlorinated pesticides by thin-layer chromatography

1974

Phytochemical profile and insecticidal activity of Drimia pancration (Asparagaceae) against adults of Stegobium paniceum (Anobiidae)

2020

Chemical and spectroscopic investigation of the bulbs of Drimia pancration resulted in the isolation of one known flavonol (1), never isolated from this plant species, and of three previously described steroidal saponins (2–4), but whose configuration at their stereogenic centres was not clearly determined. By mean of 1H NMR, 13C NMR, nuclear overhauser effects (NOE) and two-dimensional NMR spectra the full stereochemical structures of compounds 2–4 were proved and all the 1H and 13C signals were assigned. Furthermore, the methanol and butanol extracts of D. pancration were tested against adults of Stegobium paniceum beetles. Despite the non-significant results regarding the repellent activ…

Sequence variation and regulatory variation in acetylcholinesterase genes contribute to insecticide resistance in different populations of Leptinotar…

2021

Abstract Although insect herbivores are known to evolve resistance to insecticides through multiple genetic mechanisms, resistance in individual species has been assumed to follow the same mechanism. While both mutations in the target site insensitivity and increased amplification are known to contribute to insecticide resistance, little is known about the degree to which geographic populations of the same species differ at the target site in a response to insecticides. We tested structural (e.g., mutation profiles) and regulatory (e.g., the gene expression of Ldace1 and Ldace2, AChE activity) differences between two populations (Vermont, USA and Belchow, Poland) of the Colorado potato beet…

Micropropagation and in vitro culture of Pyrethrum [Chrysanthemum cinerariifolium (Trev.) Vis.]

2014

Pyrethrum (Chrysanthemum cinerariifolium (Trev.) Vis. = Tanacetum cineariaefolium (Trev.) Schultz-Bip.) is a perennial herbaceous plant belonging to the family Asteraceae, native to Albania and the area of former Yugoslavia. It is the only species in the genus Tanacetum having an agronomic importance, although the genus consists of several species producing similar types of bioactive metabolites. The species is grown in order to obtain the insecticidal compounds collectively termed pyrethrins, which are found primarily in the flower heads. In this work we discuss the results found from a worldwide literature review about the micropropagation techniques followed on Pyrethrum, the in vitro cu…

Structural and functional role of Domain I for the insecticidal activity of the Vip3Aa protein from Bacillus thuringiensis

2022

12 p.-4 fig.-2 tab.