The priority components thus identified and their precursors are monodesmethyl isoproturon (MDIPU) from isoproturon (IPU), aminomethyl phosphonic acid (AMPA) from glyphosate (GLYP), thifensulfuron acid (TSA) from thifensulfuron methyl (TSM) and N-(1,1-dimethylacetonyl)-3,5-dichlorobenzamide, also known as RH24580, from propyzamide (PROP) (Fig.
GLYP and AMPA: Positive mode ESI LC-MS of FMOC-AMPA gave a protonated molecule at m/z 334 from which a product ion at m/z 179 (fluorenyl methylium) was formed via neutral loss of AMPA (-111 Da) during CID (Fig.
GLYP and AMPA-treated soil columns: GLYP was applied to the soil columns at the maximum recommended application rate.
The lower values for AMPA in leachates (0.9%; 3.15 ug) compared with the proportion of GLYP in the leachate from GLYP treated columns indicates the restricted mobility and lower persistence of AMPA in the soil as compared to its parent GLYP (Fig.
On release, GLYP undergoes microbial degradation to produce AMPA as the main TP (Kenneth, 1990; Franz et al., 1997).
The delayed elution of AMPA from both the GLYP-and AMPA-treated soil columns showed its stronger affinity to soil particles than GLYP. GLYP and AMPA have been found to be more mobile in soil that has a sandy loam texture even with high organic carbon content (Kenneth, 1990), hence, the organic matter content has little role in GLYP mobility in soils (Jacobsen et al., 2008).
GLYP molecule has the pKa's 0.78, 2.29, 5.96 and 10.98.
To evaluate the presence of other counter ion that could resulted in better efficiency in ion exchange, the clhoride was change by nitrate anion as exchange group when it was observed that the analytes retention decreased by 32% for AMPA in both pH values, whereas for GLYP the exchange group had no significant influence and the signal decreased of 3 and 0.3 % for pH 6.0 and 8.0, respectively.
So, the flow rate was varied in the sample cartridge containing the resin (1.0, 3.0 and 5.0 mL [min.sup.-1]) and, it was obtained the highest percentage of retention for both analytes occurred when the sample flow rate was 1.0 mL [min.sup.-1], but for the condition of 5.0 mL [min.sup.-1] it was observed that the AMPA signal remained practically constant and the GLYP signal decreased 'Ca' 15% (Figure 1).
After the establishment of the sample flow rate, the eluent flow rate was varied (0.5, 1.0 and 2.0 mL [min.sup.-1]) and, it was not observed significant differences in the percentage of analyte eluted when the eluent flow rate varied from 0.5 to 1.0 mL [min.sup.-1]; thus, 1.0 mL was selected, which results in recoveries percentage of 30% and 40%for AMPA and GLYP, respectively (Figure 2).
When the sample volume was 100 mL it was obtained better analytes retention and better recoveries values (88.42 [+ or -] 1.50 and 76.16 [+ or -] 1.30% to GLYP and AMPA, respectively) (Figure 4).
When it was used 1.0 mL of HCl 10.0 mmol [L.sup.-1] the maximum analytes recoveries were 68.86 [+ or -] 1.37% for the AMPA and 46.37 [+ or -] 2.48% for GLYP (Figure 5A), indicating that part of analytes were still attached to the resin after the elution process.