Drying Recommendations
After collection, plant material should be washed to remove any residual soil or dust.
For phenols: Dry samples at 50 - 52°C for 24 hours using a forced air oven. Avoid drying higher than 55°C as it could affect phenolic quantification. Best practice is to immediately freeze samples with liquid nitrogen and then freeze-dry the samples without thawing. Store the freeze-dried material in a dark, dry location (e.g., a desiccator).
Fresh samples or those suspected to be moist: Place samples into paper bags (with adequate room for air movement within the bag) and dry in a forced air oven at 55-60°C. In general, adequate drying time is approximately 12 hours or until the material snaps or breaks easily. All samples, except freeze drying material, should be turned every 24 hours.
Drying Exceptions:
- Range samples take 24 hours or more to dry
- Power plant ash samples take three days to dry
- Solid pieces of wood take 24 hours to dry
- Any material larger than gallon size will take one or more days to dry
- Fruits and vegetables should be freeze dried and pureed (weigh the samples before and after the freeze-drying process)
Note: These time frames are based on use of a large, forced-air oven. Times need to be adjusted accordingly for other types/sizes of ovens.
Grinding Recommendations
Most plant and feed samples should be ground to pass through a 40-mesh screen. HOWEVER, for methods 635, 640, and 650, the grind must be larger and pass through an 18-mesh screen. Large wood samples must be splintered into smaller pieces before grinding. The maximum unground sample size is one (1) large #56 grocery bag.
Grinding Exceptions:
- Grape blades – use a 20-mesh screen due to tricomb separation from leaf
- Sugar beet petioles – use a 20-mesh screen due to high sugar content
- Corn stalks – use a 10-mesh screen due to high sugar content
- Freeze dried samples – do not need to be ground as they are easily crushed manually