Development of a liquid chromatography-tandem mass spectrometric method for the simultaneous determination of tropane alkaloids and glycoalkaloids in crops.

A new, rapid and sensitive multiresidue method is reported for the simultaneous determination of tropane alkaloids (tropine, atropine, scopolamine, homatropine, anisodamine) and glycoalkaloids (α-solanine, α-chaconine) in grains and seeds (wheat, rye, maize, soybean, linseed). Dispersive solid phase extraction (DSPE) was performed with 0.5% formic acid in acetonitrile/water and a mixture of magnesium sulphate, sodium chloride and sodium citrate. For a fast and effective clean-up procedure for oily matrices such as soybean and linseed, matrix solid phase dispersion (MSPD) C(18) material was used to remove co-extracted non-polar components. No clean-up was necessary for less oily matrices following extraction. The analytes were separated by isocratic HPLC on a Chirobiotic V column and detected using a triple quadrupole mass spectrometer with electrospray ionization (ESI). All analytes were monitored in the positive ion mode. The method performance is presented in terms of linearity in the range 5-80 ng/g (r(2)=0.998), specifity, selectivity, accuracy (recoveries from 61-111%), precision (CV<5%) and ruggedness. The limits of quantitation (LOQ) were in the range 2.2-4.9 ng/g.

Analysis of DDT residues in soil by ELISA: an international interlaboratory study.

An international interlaboratory study was conducted to determine the performance of a group of laboratories from developing and developed countries. The study used a commercial microwell ELISA on unknown samples spiked with different levels of DDT. The study design was based on Youden pairs and balanced replicates. Two soils, differing in particle size distributions, organic matter content, and cation-exchange capacities and thought to be DDT-free, were spiked at 5 DDT levels between 0.025 and 2 mg/kg. Nineteen laboratories in 17 countries took part in the collaborative trial; of these, the majority were modestly equipped laboratories in developing countries. Samples were analyzed without filtration or cleanup and using standards of pure DDT in methanol. Data were analyzed for repeatability and reproducibility, and average recoveries at the spike levels were calculated. Mean real recoveries for both soils were similar (103% for soil A and 100% for soil B), with values between 0.1 and 2 mg/kg DDT. Precision estimates were best in the linear working range of the assay (0.1-0.5 mg/kg DDT), with reproducibility relative standard deviations (RSDR) typically averaging about 38 and 46% near the upper and lower detection limits, respectively. Corresponding repeatability relative standard deviation (RSDr) values were 20-36% and 36-57%. Thus, even though much of the trial was performed under developing country conditions, performance statistics were similar to other reported results obtained with ELISAs on small molecules of agricultural importance, such as mycotoxins and pesticide and antibiotic residues.