A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for simultaneous determination of two hydrophilic aminoglycosides, kasugamycin and validamycin-A, in a variety of matrices (apples, cabbage, cucumbers, lettuce, tomatoes, and eggplant) has been developed. The proposed method provides sufficient sensitivity and excellent chromatographic performance using a special ReproSil 100 C18 column with 0.1% formic acid as the mobile phase additive. Accurate mass information for both analytes was obtained based on time-of-flight (TOF) mass spectrometry. The methanol/water (70 : 30, v/v) with pH adjusted to 5.5 was selected as the extraction solvent. The combination of hydrophilic–hydrophobic-balanced (HLB) cartridges with strong cation exchange SCX cartridges was used to purify the extracts with strongly polar compounds and satisfactory results were obtained. The consecutive solid-phase extraction minimized signal suppression/enhancement which led to matrix effects in the range of −12.6 to 6.11% only. Recovery experiments were performed for both compounds at three levels (50, 100, and 500 μg kg−1) in six different matrices and yielded good recoveries ranging from 81.7% to 108% with relative standard deviation values below 13%. The limits of quantification (LOQs) for kasugamycin and validamycin-A were 4.1 μg kg−1 and 1.0 μg kg−1, respectively.

A simplified QuEChERS method coupled with a small injection volume was developed for the simultaneous determination of 28 pesticides in 6 matrices (apples, cucumbers, tomatoes, luffa, cabbages, and eggplants) using LC-MS/MS. In the sample procedure, acetonitrile with 0.1% (v/v) formic acid was used to extract and no depurative powder was used. Three fortified levels (10, 50, and 100 μg kg−1) were determined and the recoveries of 168 analyte/matrix combinations were in the range of 60–120% except for cyromazin, pendimethalin, and fenpropathrin. Half of the 168 LOQs were below 0.1 μg kg−1, and 29 LOQs were above 1 μg kg−1. Moreover, four relationships between signal suppression and injection volume were observed ranging from 0.5 μL to 15 μL. For many analyte/matrix combinations, the matrix effects could be reduced to less than 20% if the injection volume was less than a critical value (named critical volume). The critical volume depending on the initial extent of matrix effects was explored and the conclusion was: for weak or medium MEs, usually ≤2 μL injection volume was needed and for several weak MEs, injection volume ≤ 5 μL can reduce the matrix effect to a negligible level.

A series of 15 organic phosphonate esters enatiomers containing a carbon atom as a chiral center have been separated on the cellulose tris(3,5-dimethylphenyl carbamate) chiral stationary phase (CSP) in the normal phase by high performance liquid chromatography (HPLC). Both the capacity factor (k) and separation factor (α) of all solutes are presented. The influence of the substitutional group on the benzene ring attached to the chiral carbon atom and the steric hindrance of alkoxyl of the phosphonate ester on the chiral separation are discussed. Based on α and different structure parameters, good agreement between the predicted values and the experimental ones is obtained. The most characteristic parameter influencing the chromatographic separation is chosen from many structure parameters by linear regression method of QSAR software. The probable mechanism of the chiral recognition is proposed.