Leaves, dislodging residues

Extracts of gloves, extracts of foliar dislodgeable residue and absolute foliar residues, and filters containing thiophanate-methyl were analyzed by reversed-phase HPLC and ultraviolet detection at 254 nm (Engel, 1988). The LOD was 50 mg/L for extracts of filters and gloves, and 10 mg/L for leaf samples. Recovery was > 90%, and the "between days" CV of the analytical chemical method was < 5%. 

Cloth patches were attached to the clothing in four areas to collect dislodgeable residues. Blood and urine samples were collected at the end of each work day. Leaf samples were taken daily to determine dislodgeable residues of phosalone and its... 

The HDE s to the hands of the thinners versus the total residue found on the leaves is shown in Figure 2. The regression equation is Y = 690X-45 where Y is the HDE in (Jg/h and X is the leaf residue in pg/cm2, and the correlation coefficient was 0.99. Since the regression line does not go through zero, the value of the X intercept corresponds to non-dislodgeable residues which is only 4% when the initial value was 1.71 pg/cm2 and 9% when the initial value was 0.70 pg/cm2. 

Reentry intervals are now established on the basis of (1) data on dermal absorption or dermal dose response (2) inhalation, dermal, and oral acute toxicity studies in animal models (3) foliar and soil residue dissipation data and, (4) available human exposure data. CDFA recommends several sources as useful guides for determining residues of pesticides on soil and leaf surfaces (dislodgeable residue) and conducting field reentry studies involving human volunteers (1-5). Human exposure studies may not be required if adequate animal data from (1) through (3) above are... 

Step 5. Cake Discharge - At this point the air pressure is released, the cake outlet is opened and the leaf stack is vibrated to discharge the cake. The cake outlet opening must be interlocked with a pressure sensor to avoid opening under pressure. On some filters the cloth or mesh screen may be backwashed with water after cake discharge to dislodge and remove any cake residue that adhered to the medium. 

After the foliar samples have been collected they are placed on wet ice and brought back to a facility for dislodging. The goal of the dislodging procedure is to extract the residue present on the leaf surface that is available for transfer from the leaf. Residues that have been absorbed into the plant matrix would not be available for transfer. The best practice is to dislodge the residue within 4 h of collecting the sample. 

There are several suggested sources which are useful guidelines for determining residues of pesticides on soil and leaf surfaces (dislodgeable) and conducting field reentry studies involving human volunteers (3), (4), and (5.). Human... 

Gunther, F.A., W.E. Westlake, J.H. Barkley, W. Winterlin and L. Langbehn (1973). Establishing dislodgeable pesticide residues on leaf surfaces. Bull Environ. Contam. 

Dislodgeable foliar residues from strawberry plants were obtained by collecting 48 circular leaf punches on a random basis, starting with the first day post-application of carbaryl, finishing on the last day of the study (Day-17 post-application). A description of the mechanical leaf punch and the collection technique may be found elsewhere (jj. 

Dislodgeable foliar pesticide residues and leaf dust were isolated by methods described in the published literature (5.6.7.8). Basically the method for the extraction of dislodgeable carbaryl... 

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