A method based on a ReproSil 100 C18 column without any ion pairs or buffer additives is proposed for the determination of polar aminoglycosides.

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 mg kg À1 ) 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 mg kg À1 , and 29 LOQs were above 1 mg kg À1 . Moreover, four relationships between signal suppression and injection volume were observed ranging from 0.5 mL to 15 mL. 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 mL injection volume was needed and for several weak MEs, injection volume # 5 mL can reduce the matrix effect to a negligible level.