Cloud point extraction–atomic absorption spectrometry for pre-concentration and determination of cadmium in cigarette samples

A new complexing agent, 2-((2-((1H-benzo[d]imidazole-2yl)methoxy)phenoxy)methyl)-1H-benzo[d]imidazole (BIMPI), was used in cloud point extraction and applied for selective pre-concentration of trace amounts of cadmium in cigarette samples. Cadmium was complexed with BIMPI in a buffer solution (pH?=?10) using Triton X-114 as surfactant and quantitatively extracted into a small volume of the surfactant-rich phase after centrifugation. Under optimized conditions (pH?=?10.0, 0.8?×?10^?4?mol?L^?1 BIMPI and 0.08 % (w/v) Triton X-114), calibration graph was linear in the range of 34.0–1,670.0 μg?L^?1. The proposed method was applied to the determination of Cd in various cigarette (tobacco) samples which gave satisfactory results.     

Community air monitoring for pesticides—part 2: multiresidue determination of pesticides in air by gas chromatography,gas chromatography–mass spectrometry,and liquid chromatography–mass spectrometry

Two multiresidue methods were developed to determine pesticides in air collected in California. Pesticides were trapped using XAD-4 resin and extracted with ethyl acetate. Based on an analytical method from the University of California Davis Trace Analytical Laboratory, pesticides were detected by analyzing the extract by gas chromatography–mass spectrometry (GC-MS) to determine chlorothalonil, chlorthal-dimethyl, cycloate, dicloran, dicofol, EPTC, ethalfluralin, iprodione, mefenoxam, metolachlor, PCNB, permethrin, pronamide, simazine, trifluralin, and vinclozolin. A GC with a flame photometric detector was used to determine chlorpyrifos, chlorpyrifos oxon, diazinon, diazinon oxon, dimethoate, dimethoate oxon, fonophos, fonophos oxon, malathion, malathion oxon, naled, and oxydemeton. Trapping efficiencies ranged from 78 to 92 % for low level (0.5 μg) and 37–104 % for high level (50 and 100 μg) recoveries. Little to no degradation of compounds occurred over 31 days; recoveries ranged from 78 to 113 %. In the California Department of Food and Agriculture (CDFA) method, pesticides were detected by analyzing the extract by GC-MS to determine chlorothalonil, chlorpyrifos, cypermethrin, dichlorvos, dicofol, endosulfan 1, endosulfan sulfate, oxyfluorfen, permethrin, propargite, and trifluralin. A liquid chromatograph coupled to a MS was used to determine azinphos-methyl, chloropyrifos oxon, DEF, diazinon, diazinon oxon, dimethoate, dimethoate oxon, diuron, EPTC, malathion, malathion oxon, metolachlor, molinate, norflurazon, oryzalin, phosmet, propanil, simazine and thiobencarb. Trapping efficiencies for compounds determined by the CDFA method ranged from 10 to 113, 22 to 114, and 56 to 132 % for 10, 5, and 2 μg spikes, respectively. Storage tests yielded 70–170 % recovery for up to 28 days. These multiresidue methods represent flexible, sensitive, accurate, and cost-effective ways to determine residues of various pesticides in ambient air.     

Single drop microextraction and gas chromatography–mass spectrometry for the determination of diflufenican, mepanipyrim, fipronil, and pretilachlor in water samples

An analytical method for the determination of diflufenican, mepanipyrim, pretilachlor, and fipronil in water samples was developed using single drop microextraction in the direct immersion mode and gas chromatography–mass spectrometry. A factorial fractionated design of type 2^6–1 at two levels was performed, to study the influence of experimental variables such as ionic strength, pH, agitation speed, extraction time, drop volume, and sample volume. To establish the optimal conditions for the variables that were significant, a Doehlert design was performed. The optimum conditions of extraction were 1 μL of heptane immersed in 4.0 mL of sample with continuous agitation at 500 rpm for 30 min at room temperature. The developed method proved to have good linearity for the range studied. The detection limits were 0.07 μg L^?1 for diflufenican, 0.03 μg L^?1 for mepanipyrim, 0.08 μg L^?1 for pretilachlor, and 1.39 μg L^?1 for fipronil. The method was validated on river water samples, showing the absence of matrix effect and recoveries ranged from 90.1 to 107.8 %. The results show that the method developed is accurate, sensitive, rapid, simple, and low cost, so it is recommended for application in the analysis of these different classes of pesticides in water samples.