Moisture balances determine the moisture concentration of a particular substance. For example, you may check the moisture content of bread to ensure adequate shelf life or that the bread is not too dry. Or, you may analyze the moisture content to ensure just the right amount of water or moisture is contained within the final food product. Moisture balances operate under the principle that the weight of a substance is measured before and after, to determine the loss of water or loss on drying (LOD).
There are four main methods of determining the moisture concentration in a solid:
This method uses direct infrared radiation instead of hot circulating air to dry the sample. The infrared rays are absorbed by the sample and the absorbed energy causes the desired heating of the substance.
This method is a further development of infrared drying. The radiator technology is based on the new halogen radiator principle.
Here, a sample is dried by means of hot circulating air. To tighten up the drying conditions or to protect thermally unstable substances, drying is frequently performed under vacuum. The moisture content is determined by a differential weighing before and after drying.
This method is based on the absorption of microwave radiation by the water molecules of the sample. This absorption generates heat and leads to vaporization of the volatile components. Measured variable is here also the total amount of volatile components. This is determined by weighing before and after drying.
Helpful hints to improve your weighing accuracy
- Before weighing ensure your balance is leveled correctly.
- Keep your balance clean at all times. Visually check for debris spillage prior to use and, if spotted, clean using a balance brush.
- Never use your hands to place tare weights or samples in the weigh chamber. Use appropriately sized and shaped tweezers or tongs to handle weighing vessels.
- Use vessels of an appropriate size and material for your samples. For moisture analyzers, use aluminum sample pans due to the heat generated from the heating elements.
- When placing objects on the balance weigh pan, aim for the same place each and every time, i.e. try to aim for the middle of the pan each time you weigh. This cancels out any effects caused by eccentricity (corner load error).
- Be aware of how your balance is affected by your working environment.
When you finish weighing, check that the weigh chamber is clean and free of any spillage.
These simple tasks will help maximize your measurement scheme and make the most of an electronic balance.