Found in labs across a range of industries, moisture balances provide accurate measurements of moisture content in samples. However, the accuracy and reliability of the data received is dependent on the correct preparation of samples, so it is essential that this step is taken with due diligence. Read on to learn more about moisture balances and how the proper preparation of your sample can lead to more accurate results in the lab.
What is a moisture balance?
A moisture balance, or moisture analyser, is used to measure the moisture content in samples. It does this using the gravimetric moisture measurement principle, also known as thermogravimetry or loss of drying (LOD). It is used across a broad spectrum of industries that require controlling the condition of moisture content in the products they manufacture.
The food industry
The food industry relies heavily on the use of moisture balances throughout its manufacturing processes, from goods-in inspection, through quality control, production and storage, to the development of new products. The finished product you may see in stores will have gone through a meticulous process to find its ideal moisture content, ensuring the most desirable and consistent taste, appearance, texture, and shelf life of products.
The pharmaceutical industry
Another mass industry which leans on moisture content determination is pharmaceuticals. The role of moisture balances is significant in pharmaceutical quality control tests, assessing incoming raw materials, in-process quality control and the final pharmacopeial testing procedures.
The plastics industry
To ensure high-quality plastic parts are being produced, the moisture content of plastic pellets must be regulated. Moisture balances are used to control the moisture content of polymer resins, preventing issues during compounding and injection molding, as well as smoothing surfaces and helping facilitate optimum mechanical properties of the injection-molded parts.
What’s the difference between halogen and convection moisture balances?
In comparison to other moisture determination methods available, moisture balances are among the most meticulous. As the method relies on gravimetric measurement, it is independent of the sample material and therefore provides a relative amount of flexibility.
There are two ways in which thermogravimetric moisture balances efficiently withdraw moisture content from a sample:
Convection - the transfer of heat via mass motion. An example of an instrument that might be used to dry a sample would be a conventional drying oven.
Radiation – the transmission of energy in the form of waves/particles through the sample. Metal and halogen heating elements radiate energy within the infrared spectrum.
Convection moisture balances contain a low-resistance metal heating element that works by converting electricity into heat. These types of moisture balances are often used for processing food, where glass components are forbidden due to health and safety regulations. However, moisture balances which use metal components have a considerably large thermal mass and take longer to heat than moisture balances that carry halogen. This makes them more difficult to control and decreases the possibility of reproducibility in a moisture balance.
Halogen moisture balances, on the other hand, contain halogen radiators that consist of a tungsten heating element encased in a compact glass vial filled with protective halogen gas. Infrared radiation is then emitted by the halogen radiator in the short wavelength range of 0.75-1.5 micrometers. The heating/cooling response time benefits from the compactness of the halogen, which shortens the time for the moisture heating unit to reach optimum power, resulting in a faster drying process.The compact nature also allows for more precise controls during the heating process.
Take a look at the halogen carrying moisture balances that Delta Scientific has to offer.
How to prepare your moisture balance sample
The preparation of your samples is crucial for ensuring the most accurate results. Weigh the sample before, during and after the drying process using a precision scale. When processing any sample, it is important to not jeopardize the integrity of the sample to ensure consistent results and reduce the probability of invalid results due to errors.
The temperature tolerance of the sample is calculated before the drying process so that the temperature is warm enough to draw out moisture but not so hot as to burn the sample. It is imperative to wait before using the moisture balance to find the water content of the sample, as moisture balances only supply a reading after approximately five to ninety minutes. Read on for step-by-step instructions for properly preparing your sample for a moisture balance.
List of equipment:
- Beaker
- Spatula
- Pipette
- Fiberglass pads
- PMB moisture analyser
- Disinfectant wipes
Step one:
Samples must be stored in airtight containers in a temperature-controlled room before they are weighed. This is because samples can become unstable or alter when subjected to humidity, heat, cold and light.
Step two:
Ensure all instruments and apparatus have been sterilized before coming into contact with the sample so as not to contaminate it and produce invalid results.
Step three:
Calculate the tare weight, or empty weight, of the container you will use to hold the sample. The weight recorded will then be subtracted from the gross/laden weight of the sample. Some moisture balances may have a tare setting to help you with this.
Step four:
Using precision scales, weigh the sample. Some industries require a specific methodology for sample weight testing - for example, a type of bread might be required to be tested 3 times with 30g pieces for standardized testing in the food industry.
Step five:
Some samples are required to be ground into a powder or paste before being placed in the moisture balance. If this is the case, ensure the sample is neither heated nor cooled during the process and always use sterilized instruments. Powders and pastes must be of a fine and even consistency and liquids must not contain gas during the measurements.
If the sample is solid, distribute it directly on to the moisture balance pan, as evenly as possible, using a spatula. If the sample is liquid or a paste, spread the sample on a fiberglass pad using a pipette. Uneven samples can splatter during the heating process, whereas even samples dry more rapidly when placed in the moisture balance.
Step six:
Place the sample in the moisture balance and set the temperature to the appropriate level. Close the heat cover of the moisture balance to begin the drying process.
Step seven:
You can easily check the sample status during measurements. Record the weight of the sample throughout the moisture balancing process until the weight no longer fluctuates. If the moisture balance is in automatic mode, it will automatically stop when it no longer senses weight loss.
For further enquiries and expert help from Delta Scientific, get in contact with our reliable team today.