In addition, it has been noted that the residues of the carcinogenic and mutagenic metabolites (i.e., DCBX and DOLQ) must be monitored for the regulation of these AGPs in food animal production.
DOLQ showed a molecular ion at m/z 232 amu and two prominent product ions at m/z 143 and m/z 145.
Figure 2 shows the representative MRM chromatograms of blank liver samples spiked with the analytes at 0.5, 0.5, 0.05, 0.02, 0.05, and 0.05 [micro]g*[kg.sup.-1] for QCA, MQCA, DCBX, DOLQ, QCA-glycine, and MQCA-glycine, respectively.
In this method, the occurrence of MQCA, QCA, DCBX, DOLQ, QCA-glycine, and MQCA-glycine in real samples was confirmed by comparing the ion ratios of the two MRM transitions with those obtained from the matrix-matched calibration curve standards.
The matrix spike curve showed good linearity within the tested range 0.02-50 [micro]g x [kg.sup.-1] for DOLQ, 0.05-50 [micro]g x [kg.sup.-1] for DCBX, QCA-glycine, and MQCA-glycine, and 0.5-50 [micro]g x [kg.sup.-1] for QCA and MQCA, respectively, and the matrix effects were found to be in a range of 11.5-23.8%.
All the samples were analyzed for QCA, MQCA, DCBX, DOLQ, QCA-glycine, and MQCA-glycine residues to determine whether there exists misuse/or illegal use of the AGPs in the locality.
Since there existed a doubt whether QCA and MQCA are suitable residue markers for the regulation of these two AGPs in food animal production, the residues of the carcinogenic and mutagenic metabolites (i.e., DCBX and DOLQ) should also be monitored for regulatory control.
Caption: FIGURE 1: Mass spectra of (a) QCA, (b) MQCA, (c) DCBX, (d) DOLQ, (e) QCA-glycine, and (f) MQCA-glycine.