Customers frequently ask us questions about the use and operation of their Moisture Balances. We would like to use address the most common questions and answers in this post. If after reading through this, you still have questions please feel free to contact us.
Can LAW Calibration give me a method to use for my moisture balance?
There is no one-size-fits-all method for moisture analysis, as samples vary greatly and have a great deal of variance in both chemical and physical properties. However, we provide the OHAUS Moisture Guide that you can use as a starting point for your method development. After that we are here to assist you to ensure that the unit is the correct unit for your particular application. Ultimately it is up to you as the user to understand your particular substance you wish to test and develop a method that best fits your sample.
How do I develop a method for my sample?
As a starting point, we are pleased to offer the OHAUS Moisture Guide. This guide is free to download that gives you a wealth of information on the topic of moisture analysis, including a list of sample methods for various substances you can use as a reference and starting point for your method development.
In general, there are 2 ways to use a moisture analyzer. First, if you already have a reference value (likely from a drying oven or other LOD process) you can orient your method development to target this value. As a starting point, we recommend using the default values (A60 shut off, and standard drying profile) and manipulating the temperature to find your optimal setting. If your moisture content result is too low, try raising the temperature, and if it is too high, lower the temperature. Always inspect your sample once drying is complete to ensure that it has not burned or decomposed; if it has, lower your drying temperature.
If no reference value exists, then you may attempt to find a method that consistently dries your sample in the shortest amount of time (without burning or decomposing it). In this case, we again recommend using the default values (A60 shut off, and standard drying profile) and manipulating the temperature to find your optimal setting. We recommend starting with a relatively low temperature (e.g., 120°C) and raising in small increments (e.g., 10°C, as necessary), to ensure your sample is thoroughly and efficiently dried, but does not show signs of burning or decomposing.
Method development can be time consuming, so you should be prepared to spend potentially several hours, and have enough substance on hand, to make several measurements. In general, this is a process of trial and error.
Why do I see a slighly higher or lower result when moving from one OHAUS moisture analyzer to another?
When comparing results of 2 different moisture analyzers, always check that both units are properly maintained and adjusted prior to testing. Make several measurements to get a baseline of results on each unit, as sample preparation, etc. can have an impact on the end result.
In general, OHAUS moisture analyzers should yield approximately the same value when using the same method. However, variations in design may affect temperature sensitive samples, and cause variances in the end value from device to device (model to model). In these cases, it is reasonable to alter the method (to some degree) to achieve the reference value (i.e. raise the temperature a few degrees to realize a higher %MC value, or lower the temperature a few degrees to realize a lower value). In most cases, changing the temperature by a few degrees (e.g., ±5°) should account for the differences in heating.
The design (geometry) of the heating chamber is different (on different models) and affects how the sample is heated. The MB90 and MB120 were designed to ensure that the surface of the sample is heated evenly, avoiding any cold or hot spots, and providing a high degree of repeatability (low variance / standard deviation) across multiple measurements.
If you are experiencing any issues with your Moisture Balance we are here to assist. Please feel free to give us a call at 207-494-7538 or email us at firstname.lastname@example.org with any questions that you may have and one of our Factory Trained technicians will be more than happy to assist you.