The results showed that ethyl acetate led to a low recovery for MQCA, which was in accordance with the previous studies [1, 27].
The equations were y = 365.31x + 1329.4 for 1-DMEQ, y = 621.55x + 335.41 for BDMEQ, and y = 547.98x + 157.67 for MQCA. The correlation coefficients ([r.sup.2]) for each analyte were over 0.99.
Totally, 14 positive samples were detected positive with concentrations of 1-DMEQ, BDMEQ, and MQCA ranged from 2.27 to 6.44 [micro]g/kg, 3.69 to 6.88 [micro]g/kg, and 3.57 to 9.22 [micro]g/kg, respectively (Table 5).
This research describes a novel ultrasound-assisted acidolysis-based UPLC-MS/MS method for the determination of three major metabolites of mequindox (1-DMEQ, BDMEQ, and MQCA) in holothurian samples.
The parameters of the m/z and collision energy of parent ions and quantitative product ions of DCBX, DOLQ, QCA, MQCA, QCA-glycine, and MQCA-glycine are shown in Table 1.
Linearity was evaluated from the calibration curves by triplicate analysis of blank tissue samples fortified with the analytes at five concentration levels (DCBX, DOLQ, QCA-glycine, and MQCA-glycine at 0.05, 0.10, 0.2, 0.5, and 5 [micro]g*[kg.sup.-1]; QCA and MQCA at 0.50, 1.0, 2.5, 5.0, and 10.0 [micro]g*[kg.sup.-1]).
In previous studies on quantitative determination of carbadox and olaquindox residues in the porcine muscle or liver, the samples were subjected either to alkaline hydrolysis at 105[degrees]C for 1h or protease digestion overnight to release the QCA and MQCA [11, 12].
The MS/MS of QCA and MQCA exhibits a similar MS/MS fragmentation pattern which has been described previously [15,16].