Moisture loss during sampling

Place sample (5 to 10 ml) in a disposable sample cup, completely covering the bottom of the cup, if possible. Place sample into sample cup in a timely manner to minimize moisture loss or gain during handling. If sample is not to be tested immediately, place a sample cup lid on the cup to prevent moisture transfer with the room atmosphere. 

Fill a sample cup half full ( 7 ml) with selected salt standard. Place sample into sample cup in a timely manner to minimize moisture loss or gain during handling. 

Usually, the first moisture value to be obtained on a coal sample is the air-dry loss moisture. This moisture loss occurs during an attempt to bring the coal sample into equilibrium with the atmosphere in the sample preparation room. The practice of using temperatures above room temperature may accelerate oxidation but shortens the time needed for air drying hence, temperatures above 40 to 50°C (104 to 122°F) are not recommended for air drying. 

Variations in the data that fall outside the experimental allowable limits may be due to factors that originate during sample preparation and handling, such as (1) the sample moisture may not have been in equilibrium with the laboratory atmosphere (2) the sample may have been overdried or under-air-dried (3) excessive dust loss may have occurred during screening due to a loose-fitting... 

Invalid sampling, loss of sample during weighing or dissolution, contamination by impurities in reagents, and changes in composition due to varying moisture content. 

Many studies of the losses of thiamine have been reported. Depending on the moisture content of the product and the exposure temperatures and time, losses up to 89% have been reported. At 63°C, 20 h are required for a 50% loss of thiamine in dried pork. It has also been shown that for samples held at 49°C at moisture contents of 0%, 2%, 4%, 6%, and 9%, the losses of thiamine were 9%, 40%, 80%, 90%, and 89%, respectively. Thiamine losses during drying from different sources have been summarized in Table 24.6. 

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