OMB First to Final Action Recommendation Checklist 11-12-18

C HANG ET AL .: J OURNAL OF AOAC I NTERNATIONAL V OL . 99, N O . 4, 2016 1053

with degradation trend E at a concn, and among them, 9 and 21 pesticides were also in accordance with degradation trends A and B, respectively, at b concn, accounting for 45.5 of the 66 pesticides. Meanwhile, there were 40 pesticides in accordance with degradation trend E at b concn, but only 3 and 5 of these pesticides corresponded with degradation trends A and B, respectively, at a concn. At the same time, there were 24 pesticides in accordance with degradation trend E at both concentrations, accounting for 36.4 and 60.0 of the pesticides that were in accordance with degradation trend E at a and b concns, respectively. Degradation trend F.— Taking kresoxim-methyl as an example, the pro¿les of degradation trend F are shown in Figure 7. The concentrations of the degraded pesticides presented as scatter points, and no degradation trend can be found by any of the above-mentioned ¿tting curves with R 2 values •0.4. The unsteadiness properties of these pesticides in aged Oolong tea during storage might be the reason. There were 16 pesticides at a concn and 24 pesticides at b concn in accordance with degradation trend F, accounting for 5.9 and 8.9 of 271 pesticides, respectively. In addition, nine pesticides were in accordance with degradation trend F at both concentrations. This discussion of degradation trends A–F indicates that the 271 pesticides studied here have relatively complex degradation trends in aged Oolong tea, with various ¿tting curves at different concentrations. Among the degradation trends A–F, degradation trends A, B, and F had higher ratios than the others. All the pesticides in accordance with degradation trends A, B, and E decreased exponentially over 40 days and decreased mainly exponentially or logarithmically over 120 days. In addition, although no degradation trend was seen for the pesticides of degradation trend D over 40 days, they decreased mainly exponentially over 120 days. The conclusion is that pesticides in tea degrade slowly, with concentrations of pesticides decreasing within 4 months: at concentration a , the deviation for each pesticide from day 1 to day 120 falls within the range 0.2–85.6 (mean, 36.4 ), whereas at concentration b , the deviation for each pesticide from day 1 to day 120 falls within the range 4.0–92.7 (mean, 50.8 ). )LJXUH 'HJUDGDWLRQ SUR¿OHV RI GHJUDGDWLRQ WUHQG ( H J ƍ GLEURPREHQ]RSKHQRQH RYHU D GD\V DQG E GD\V Determination days were plotted as horizontal ordinates; residue concentrations of pesticide were plotted as vertical ordinates.

Figure 8. Distributions of pesticides according to different classes within A–F aspects at a concn. For each degradation trend ( x -axis), percentages ( y -axis) were calculated as the number of pesticides in each class in accordance with the degradation trend multiplied by 100 and divided by the total number of pesticides in the class.

Pesticides in Different Classes

To further investigate the degradation trends, pesticides in A–F aspects were divided into different classes according to organonitrogen, organophosphorus, organochlorine, organosulfur, carbamates, and pyrethroids, and “others.” Their distributions can be found in Figures 8 and 9. It is clear that most of the 271 pesticides are in the organonitrogen, organophosphorus, and organochlorine classes; therefore, the pesticides are discussed according to these three classes. For the pesticides in degradation trend A, most were organonitrogen and organophosphorus. For degradation trend B, the number of organophosphorus and organochlorine pesticides was equal but far below the number of organonitrogen pesticides. The number of organochlorine pesticides for degradation trend E was far higher than for organonitrogen and organophosphorus pesticides, and the number of organophosphorus pesticides was 5 and 3 at a and b concns, respectively. The organophosphorus and organochlorine pesticides can be further discussed for degradation trends A and B combined (A/B) and E. At a concn, 37.9 and 71.4 pesticides were organochlorine and organophosphorus, respectively, for degradation trend A/B. At the same time, 43.1 and 11.9 pesticides were organochlorine and organophosphorus, respectively, for degradation trend E. At b concn, the respective percentages of organochlorine and organophosphorus pesticides for degradation trend A/B were 41.8 and 71.8 . For degradation trend E, the respective percentages for organochlorine and organophosphorus pesticides were 34.5 and 7.7 . These results suggest that most of the organophosphorus pesticides degraded in accordance with degradation trends A and B in aged Oolong tea. In contrast, most of the organochlorine pesticides decreased according to degradation trend E in aged Oolong tea.

Figure 9. Distributions of pesticides according to different classes within A–F aspects at b concn. For each degradation trend ( x -axis), percentages ( y -axis) were calculated as the number of pesticides in each class in accordance with the degradation trend multiplied by 100 and divided by the total number of pesticides in the class.

)LJXUH 'HJUDGDWLRQ SUR¿OHV RI GHJUDGDWLRQ WUHQG ) H J kresoxim-methyl) over (a) 40 days and (b) 120 days. Determination days were plotted as horizontal ordinates; residue concentrations of pesticide were plotted as vertical ordinates.