In this work, the effect of extraction time was studied between 5 and 10 min, and static cycles in one, two and three. Figure 1B shows the effect of static time on the extraction efficiency of ASE. As can be seen, no significant differences were observed in the recoveries, as has been demonstrated by comparison of the results using Students t test for paired data at 95% significance. Figure 1C shows the average recoveries of diverse number of cycles. As can be seen, the number of static cycles had minor effects on the extraction efficiency. No significant difference was observed between the recoveries obtained with the two and three cycles. However, one cycle provided a little lower recovery, especially for metolachlor and pretiachlor, the recoveries obtained were only 75. 09 and 69.

10%, respectively. There fore, 5 min static time and two static extraction cycles p53 Signaling Pathway were chosen because they provide a short analysis time and lower consumption of solvents. The optimization of the ASE parameters has not only to be taken into account to obtain the highest analyte recov eries but also to avoid or minimize the co extraction of lipids, which depends highly on the physical chemical properties of selected solvent, such as boiling point, polarity and density. Solvents of different polarities: acetone, acetonitrile and n hexane/acetone were tested for the ASE extraction analytes from cereal samples, because the solvents have been used in the extraction of acetanilide herbicides from other matrixes. ASE was carried out under general conditions described above.

When employing different solvents in the optimization of ASE conditions, average recoveries for analytes were shown p53 Signaling Pathway in Figure 1D. As can be clearly seen, acetone gave satisfactory recoveries for all the pesticides, whereas acetonitrile and n hexane/acetone fail to extract most of the targets. The recoveries using acetone for most of the acetanilide herbi cides were from 87 to 111%, and the RSDs were 2 13%. With n hexane/acetone and acetonitrile, the recoveries varied from 25 to 88% and with acetonitrile from 9 to 144%. The RSDs were in the range of 4 20 and 4 25%, respec tively. An additional comparison of the three extraction solvents was performed based on the chromatograms. Figure 2 shows the GC ECD chromatograms obtained from extracting acetanilide herbicides from spiked samples using acetone, n hexane/acetone and acetonitrile.

As can be seen in Figure 2, the more PP-121 clean chromatogram was acquired from acetone, but dirtier chromatograms were obtained from n hexane/acetone and acetonitrile. With n hexane/acetone and acetonitrile, more extraneous compounds were co extracted from the matrix. There were many interfering chromatographic peaks for most analytes and may result in unstable baseline and cover the sign of analytes, which were the significant causes of lower recov eries. The different chromatograms for the same cereal matrix may be due to different polarities of the solvents. From these comparison results, acetone was selected as the solvent. To summarize the results obtained, the extraction conditions selected were as follows: temperature, 501C, static time, 5 min, number of cycles, 2, and acetone was the solvent.

3. 2 Study PP-121 of cleanup step ASE was chosen as the extraction method because this technique offers advantages such as amenable to automa tion, require short extraction times, reduce organic solvent consumption and reduce cost of analysis. However, lipid compounds as well as other molecules present in the samples are co extracted with the analyzed pesticides so a cleanup procedure is recommended to diminish the presence of interference in the final extract, which can affect chromatographic performance, resulting in analytical inaccuracies and decreased instrumental precision. Cleanup assays were carried out in order to find the best sorbent for the SPE. For this purpose, GCB/PSA, carbon GCB, Florisil and alumina N commercial tubes were assayed to carry out the purification of cereal crops extracts obtained by ASE.

After ASE extraction, the efficiency and the precision of the SPE were carried out by spiking the extraction with 1. 00 mL of the standard solution containing 0. 1 mg/mL. The recoveries of eight acetanilide herbicides acquired from GCB/PSA SPE tube, carbon GCB SPE tube, Florisil SPE tube. cartridge and Florisil SPE tube were satisfied. However, worst recoveries were obtained from HSP the carbon GCB SPE tube and alumina N SPE tube. Very low cleanup recoveries for metolachlor, pretiachlor and very high recoveries for butachlor were obtained when carbon GCB SPE tube was employed. The alumina N catridge for cleanup procedures gave the lower cleanup recoveries of pretiachlor. Figure 3 presents the GC ECD chromatograms corre sponding to wheat our purified with the sorbents consid ered. As can be seen, the chromatograms showed important differences, depending on the different sorbents employed.