Operating a moisture analyzer is a quality control process across industry and plays a critical role in processing materials for ultimate use. Moisture in this context refers not only to water but also to any volatile substance, the presence or absence of which is important in quality control. It can be reduced simply to the question: Are you paying for water or product? The amount of water, or the moisture content, in products works both ways and is often regulated as a quality control measure. As one example, manufacturers can “pad” the weight of their product by increasing moisture content. Consumers should know what they are buying and depending on the product may or may not accept moisture content as reasonable. That’s why labels may contain a notation such as “percent moisture” to let purchasers know how much of the weight of the purchase is contributed by water. For manufacturers or product packagers, a laboratory grade moisture analyzer available from Tovatech is the tool of choice for checking moisture content just prior to product packaging.
Proper Prepping for Moisture Analysis Here we are concerned with collecting, storing and identifying samples before using the moisture analyzer. Collecting and storage work together because hygroscopic products can absorb humidity and throw off subsequent analysis. At the other end, samples may give off moisture between the time they are collected and analyzed. This means you should isolate samples in a tight container if they must be stored prior to determining moisture content. Next you should document sample attributes or properties as these can impact the moisture analysis. Trade associations and government agencies may provide guidelines on particular moisture analyzer steps but in brief, properties or characteristics involve:
- The volume of the sample, which should be sufficient to cover the sample pan with a thin layer of product.
- Taking into account that dark colors absorb heat faster than light colors.
- Particle size. Smaller particles = shorter drying time. Therefore grinding or other methods of size reduction may be in order. But keep in mind that this process could affect moisture content.
- Sample density. Those with a dense consistency do not readily release moisture.
Drawing samples is the next consideration. If a moisture analysis is being conducted for quality control try to secure samples from a number of areas in the batch to obtain a representative analysis. If this proves impractical then conduct several sample tests as the material passes from processing to packaging. Some things to keep in mind:
- Liquid substances should be thoroughly mixed before analysis if they contain ingredients of non-uniform density.
- Likewise, semi fluid substances (think cottage cheese) should be mixed because they contain ingredients of differing densities.
Setting up the Moisture Analyzer
Moisture analyzers such as offered by Tovatech may be programmed based on procedures established by trade association and government organization standards for the products under analysis. If such standards are not available, it is up to the analyst to develop a method. Programming is accomplished by following instructions in the manufacturer’s operations manual. Parameters to be defined include sample size, sample preparation, and moisture analyzer settings such as the drying temperature, drying profile, and shut-off criteria. Most moisture analyzers offer a choice of drying profiles such as step, fast, ramp and standard (usually the default setting).
Shutoff criteria are influenced by the samples under analysis. Three methods of shutoff are common to most moisture analyzers: (1) automatically when drying is complete and the dry weight is stable, (2) after a specified time, or (3) manually. A stable dry weight is established when the weight loss per second falls below a specified value.
Sample Placement for Moisture Analysis
Speed in sample placement is important to avoid absorbing from or evaporating to the test environment. If you are working with solid substances take care to evenly spread the sample over the surface of the sample tray. Avoid lumps or “peaks” that will interfere with even drying across the entire sample. Avoid making the sample too thick as that will also interfere with even drying.
Certain liquids or semi-solids may call for the use of fiberglass filters to (1) increase the surface area of the sample, (2) help prevent crusts from forming in the surface during the drying cycle, and (3) prevent the liquid from splattering. When a filter is used to aid in spreading the sample it is placed on the pan and tared before the sample is added; when used to prevent crusting or splattering two filters are tared, and the second filter is placed over the sample under analysis.
In summary, moisture analysis is an exacting process using exacting equipment such as halogen heaters coupled with precision analytical balances. Procedures vary depending on what is being analyzed and the processes outlined by government and industry associations. The good thing is that if you perform analyses on a regular basis you can program your moisture analyzer and simply push the buttons to call up a method after loading samples. But don’t forget to keep records manually or by connecting the moisture analyzer to a PC or printer.
Contact the moisture analyzer experts at Tovatech for assistance in selecting and setting up the proper equipment for your requirements.
- Moisture Analyzer Display