A reverse-phase liquid chromatography/mass spectrometry (LC/MS) method, incorporating gradient elution, is described for the characterization of residual erythromycin A and its metabolites in salmon tissue. The method uses ion-spray, a mild atmospheric pressure ionization technique which provides an abundant protonated molecule well suited for selected ion monitoring experiments. Tandem mass spectrometry (MS/MS) using collision-induced dissociation was used to provide structural information. The LC/MS method was tested for the analysis of salmon tissue spiked with erythromycin A at levels between 0.01 and 1 p.p.m. A simple extraction and clean-up procedure, slightly modified from that described by Takatsuki et al. (J. Assoc. Off. Anal. Chem. 70, 708 (1987)), was used in this work. Using selected ion and selected reaction monitoring techniques, the LC/MS and LC/MS/MS methods provided detection limits of < 10 and 50 ng g-1, respectively. Confirmatory full-scan LC/MS and LC/MS/MS spectra were obtained at the 0.5 and 1 microgram g-1 levels, respectively. Using a combination of these techniques, the presence of residual erythromycin A was confirmed in the tissue of fish administered medicated feed containing the antibiotic. In addition, several metabolites and degradation products of erythromycin A, including anhydro-erythromycin and N-demethyl-erythromycin, were detected and where possible confirmed by comparison with authentic compounds. Although this analytical method has been shown to afford the necessary sensitivity and precision, application of these techniques to high-throughput quantitative analyses will require development of an improved clean-up procedure and preferably also of a suitable surrogate internal standard.

No abstract

Pesticides can remain in the environment for decades and contaminate surface water that is used for irrigation of produce. This study examined pesticide residues in some surface waters and foods in Louisiana. Samples of 8 foods (tomato, corn, rice, blueberry, cucumber, cabbage, wheat and melon) and 35 surface waters were studied using a QuEChERS extraction method for food samples and liquid-liquid extraction method for the water samples. Gas chromatography-mass spectrometry was used to analyze water and food samples. Nine pesticides were detected in the surface water samples and 5 in the food samples. Pesticides detected in foods were below FDA tolerance limit but 0.18 ppm cypermethrin found in tomato was within 90% of the FDA limit (0.2 ppm). Four water samples had atrazine levels that were above the FDA limit for potable water. This study suggests the need to intermittently monitor pesticide contamination in our food and water.

No abstract

Reduction of environmental pollution incurred from pesticide use is very important. Zeolite is a natural mineral capable of removing certain chemical contaminants from water. This study was carried out to test the effect of zeolite treatment on pesticide residue alleviation in surface water. Ten surface water samples were treated with natural zeolite by filtering through. An EPA method was used to extract pesticide residue from the water samples and the surfactant used to modify the net charge on the zeolite was hexadecyltrimethylammonium chloride (HDTMA-Cl). Gas chromatography-mass spectrometry was used to analyze water samples. Alleviation was achieved in all the 10 water samples that were filtered through zeolite. The highest removal of pesticides from water with zeolite included 100% of bifenthrin in sample CLC, atrazine in BPH, CDG and LBT; metolachlor in CLC, LBT, BCH, TRH2 and BPI; acetolachlor in BBH and BCH; azoxystrobin in BBH; desethylatrazine in BCH and BPI; metribuzin in BCH, TRH2 and BPI; and both clomazone and bromacil in sample BDC. A minimum reduction of 10.9% was found for metolachlor in sample BRH. Further reduction of pesticide residues up to 50% was recorded in the SMZ treatment as the concentrations of 4 out of 8 pesticide residues were reduced. This study confirms the potential of both the natural zeolite-Clinoptilolite, and SMZ of alleviating pesticide residues in water.