How to Develop Moisture Analysis Methods
Many of our posts on using a moisture analyzer to check on moisture content provide examples of conducting a moisture analysis for a specific product. The importance of proper moisture content is described in our post on why moisture content matters. But how is a moisture analysis method developed?
Several analyses may be made by researchers in order to identify the parameters to apply for a specific product such as plastic pellets, sugar, body lotion and bread crumbs. Among the testing parameters to be identified are included:
• Sample size. Usually in grams, but how much should be used for the analysis?
• Sample protection. Certain products may require being placed on and/or covered by fiberglass filters.
• Drying temperature. Too hot or not hot enough may skew results.
• Drying profile. This relates to how heat is applied to the sample. Options include standard, auto, quick, timer and manual.
• Shutoff criteria. That is, when the test is concluded. Three methods of shutoff are automatic or when drying is complete and the dry weight is stable, or after a specified time, or manual.
Also to be identified are sample preparation procedures that guide quality control personnel in charge of conducting tests using moisture balances. Samples should be representative of the batch being tested and have minimum/no exposure to ambient conditions that may cause them to either absorb or give up moisture.
Developing Moisture Analysis Methods
An ideal tool allowing researchers and QC personnel to develop moisture analysis methods is the 400-watt halogen MS-70 moisture analyzer available from Tovatech with its accompanying methods development software and ability to store up to 20 programs in memory. This moisture balance has resolution to 0.0001g (0.001% moisture) and a drying temperature range of 30⁰ to 200⁰C.
The key to developing moisture analysis methods is the WinCT software for real time graphic display of the drying profile on a PC. This is useful for determining measurement conditions include temperature and helps to reduce the time needed for measurement and for improving accuracy.
The software displays changes in the sample moisture rate in real time. It heats the sample at the highest practical temperature – that is, without changing the sample’s physical properties, and provides measurements with good repeatability.
It automatically determines the most suitable heating conditions in a short time. This is accomplished by increasing the temperature by 20°C increments every 5 minutes, from about 100⁰ to 200⁰C. The software evaluates the stability of the moisture content at each temperature and the first derivative of this data. The results establish the most suitable heating temperature in a one-time measurement that takes about 30 minutes.
A data summary for each sample processed shows the results of the moisture rate change during the measurement. Data indicating the optimum heating time and temperature for each sample are recorded and stored as a CSV file.
While the software determines the optimum heating temperature based on measured and calculated results, it is important to take into account sample behavior (e.g. burning or other evidence of sample decomposition) when selecting the analysis temperature.
Other MS-70 Moisture Analyzer Features
The large vacuum fluorescent display on the moisture balance control panel is easy on the eyes and indicates the measurement, setting value, change in moisture content, the status of the analysis and other important information during the analysis. The unit is shipped with 30 grams of Sodium Tartrate Dihydrate, a substance with a stable moisture content to be used as an accuracy check for the moisture analyzer. A translucent window enables operators to check the heating action.
For more on the MS-70 check our post on its use in quality control tests for plastics.
Questions? Contact our moisture analyzer professionals.
