Mills, soil sample homogenization

Wheat samples should be sampled and prepared for analysis according to the general instructions provided in the Pesticide Analytical Manual , Vol. 1. Soil samples should be prepared for analysis by homogenization with a hammer mill or knife mill. Water samples are used without sample preparation. 

Plant material should be added to a disk mill (grain or seed matrices) or a vertical batch processor (all other matrices). Add an equal portion of pelletized dry-ice to the sample (vertical processor only). Macerate the plant sample (or sample -I- dry-ice) until a homogeneous mixture is obtained. Soil samples should be well mixed or... 

All crop samples should be prepared with a food chopper or Wiley mill to achieve a finely divided material. Soil and water samples should be well mixed to ensure a homogeneous sample. 

Care must also be taken to ensure that particle size distributions are adequate as selected particle size distributions will achieve greater homogeneity in reference materials especially when very low sample intakes are used for measurements. This is extremely important for environmental reference materials such as soils, sediments, etc., and is optimally achieved by jet-milling with ultra-fine classification of particles. With this technique, which is non-contaminating, fast and well-controlled, the sieved fraction below 2 mm of the material is ground by... 

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