The development of a sensitive and accurate analytical method for monitoring aminoglycosides in food, environmental, and clinical samples is needed for many purposes. This study found that the responses of sodiated and protonated aminoglycosides in hydrophilic interaction chromatography with tandem mass spectrometry were enhanced upon addition of sodium acetate in methanol (5 mg L at a flow rate of 0.2 mL min) as a post-column reagent. The sensitivities of sodiated spectinomycin, kanamycin, gentamicins, neomycin, and amikacin were significantly higher than those of the protonated molecules. Streptomycin and dihydrostreptomycin only formed protonated molecules, suggesting the preferential ionisation of the guanidine moieties in these aminoglycosides. The limits of quantification of these aminoglycosides were 0.19-2.5 ng mL. Notably, this is the first quantification of aminoglycosides that uses the sodiated molecules. The enhancement technique enables us to eliminate a concentration step from the clean-up process from food samples. We also proposed a rapid analytical method for residual aminoglycosides in milk and meat samples; validation showed good accuracy and precision of this method at the Japanese maximum residual limits of aminoglycosides (40-500 µg kg). The application of this method to contaminated bovine tissues revealed remarkably high residual levels of kanamycin. This technique will be useful for the sensitive detection of aminoglycosides not only in food, but also in environmental samples and human plasma.
A validation study was carried out on a rapid method for the simultaneous determination of pesticide residues in vegetables and fruits by LC-MS/MS. Preparation of the test solution was performed by a solid-phase extraction technique with QuEChERS STQ method . Pesticide residues were extracted with acetonitrile using a homogenizer, followed by salting-out and dehydration at the same time. The acetonitrile layer was purified with C18 and PSA mini-columns. The method was assessed for 130 pesticide residues in 14 kinds of vegetables and fruits at the concentration level of 0.01 μ g/g according to the method validation guideline of the Ministry of Health, Labour and Welfare of Japan. As a result 75 to 120 pesticide residues were determined satisfactorily in the tested samples. Thus, this method could be useful for a rapid and simultaneous determination of multiclass pesticide residues in various vegetables and fruits.
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