DRIFTS sampling

The goal of spray drift sampling is to obtain representative samples of the application being investigated while minimizing any bias introduced by the methods employed to collect those samples. Collected samples are used to investigate whether pesticide products are present in the environment and, if present, at what rates relative to the amount of product(s) applied to the spray area (the field, forest or other spray area). 

Huntley, D., Mills, A., Paulen, R.C. 2008. Surficial deposits, landforms, glacial history, and reconnaissance drift sampling in the Trout Lake map area, Northwest Territories Geological Survey of Canada, Current Research 2008-14, 14 p. 

Cation exchange capacity. Note that CEC is not equal to the sum of the exchangeable cations for most of the drift samples because of contribution from calcite and dolomite to the exchangeable Ca". ... 

The reason for this high error is the automatic correction of the results using wash and drift samples, the absolute error of the drift samples (usually 5 to 10 mg L ) is too large for the small samples to be calculated correctly. This was improved significantly by calibrating the instrument in the low level range. Results were excellent. 

Figure 3.15 Schematic diagram of DRIFTS sample holder with specular reflection blocker...

FIG U RE 4.40 Left An agate mortar and pestle used to grind powders for infrared analysis. Right A filled DRIFTS sample cup. 

When enough material is available, grinding and diluting DRIFTS samples in KBr gives the best results. However, the drawback of this method is that it is destructive. Also, if you don t have much sample, or if the sample is valuable, you may not want to destroy it to take its spectrum. In these cases a small amount of sample can be placed in the bottom of a DRIFTS sample cup. The focused infrared beam is reflected directly off the sample, is collected, and is focused onto the detector like in any other DRIFTS experiment. The background spectrum is taken of the empty sample cup is taken. This technique is sometimes called micro-DRlFTS because it works on small amounts of sample. A pair of DRIFTS sample cups specially made to hold small amounts of sample are shown in Figure 4.43. 

FIGURE 4.43 A picture of two different micro-DRIFTS sample cups. 

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