Moisture Analyzer

What is a moisture analyzer and how does it work?

Select your Question

1. What is a moisture analyzer?
2. How does a moisture analyzer work?
3. What is the 'Loss on Drying' (LOD) principle?
4. How is the sample heated?
5. What is the difference between halogen technology and infrared technology?
6. Who uses moisture analyzers?
7. What is moisture?
8. Is moisture the same as water?
9. What is the official method to determine the moisture content?
10. We have to follow the standard method. Can we still use a moisture analyzer?
11. How do the results on the moisture analyzer compare to the standard method?
12. What is a method for a moisture analyzer?
13. Why do I need to do method development?
14. How do I develop a method on my moisture analyzer for my substance?
15. What is sample preparation and why is it important?
16. Which sample size do you recommend?
17. Can I determine the moisture content of plastics?
18. How to measure moisture content in food?
19. How do I need to test a moisture analyzer and which parts?
20. What is the difference between testing and adjustment? What is calibration?
21. How often should I test my moisture analyzer?

2. How does a moisture analyzer work?

The Halogen Moisture Analyzer works according to the thermo-gravimetric principle, also often referred to as 'Loss on Drying' (LOD) principle. The moisture analyzer consists of two components, a balance unit and a heating unit. In order to measure the moisture content the sample's start weight is recorded, afterwards a halogen radiator heats and dries the sample while the integrated balance continually records the sample weight. When the sample no longer loses weight the instrument shuts off and the moisture content is calculated. The total loss in weight is used to calculate the moisture content.

3. What is the 'Loss on Drying' (LOD) principle?

LOD stands for loss on drying. Most standard methods are LOD methods. LOD is a method that determines the moisture content of a sample by analyzing the weight loss of a sample upon heating. The loss of weight is interpreted as loss of moisture of the sample. When all of the moisture is out of the sample the weight of the sample no longer changes. The moisture content of a sample is then calculated by comparing the initial sample weight to the dried or final sample weight.

6. Who uses moisture analyzers?

The official method for moisture content determination is the drying oven. Today many customers use a moisture analyzer because they want to analyze the moisture content using a much faster method. Moisture analyzers are used in many industries such as food, chemical, pharmaceutical and plastics. Moisture content determination in food is of particular importance as the moisture content influences the quality and shelf life of a product.

7. What is moisture?

Moisture is everything that evaporates upon heating ("loss on drying"). In addition to water, the analyzed moisture content includes fats, alcohol and solvents.

8. Is moisture the same as water?

No, and that often gets mixed up. Moisture is everything that evaporates upon heating. Water is specifically the water molecule (H₂0). To determine the water content it is best to use a Karl Fischer titrator.

10. We have to follow the standard method. Can we still use a moisture analyzer?

Many industries regulations required to follow a standard method. However it is accepted if you can prove that the results of the drying oven and moisture analyzer are the same. Many customers in that situation on a regular basis determine the moisture content of a sample in parallel by using both the standard method and their moisture analyzer in order to verify the result.

11. How do the results on the moisture analyzer compare to the standard method?

You need to develop a moisture analyzer method that will give you the same moisture content result as the official method. METTLER TOLEDO has developed methods for their moisture analyzers for a vast variety of samples from different industries. Those methods compare and match the result of the official drying oven method.

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12. What is a method for a moisture analyzer?

A moisture method describes how the moisture content of a specific substance is analyzed using a moisture analyzer. This includes method parameters (drying program, drying temperature, switch-off criterion, sample weight, start mode, display mode) and also sample preparation (e.g. grinding) and sample application (e.g. use of a glass-fiber filter).

13. Why do I need to do method development?

Every substance requires a suitable method in order to accurately and reliably determine the moisture content. Either you want to obtain the same result with the moisture analyzer as with the reference method (typically the drying oven) or, if you don't have a reference method, your goal is getting repeatable results.

14. How do I develop a method on my moisture analyzer for my substance?

There are two possibilities for method development. First, if you have a reference method and reference value, then the goal is to obtain the same moisture content result with the moisture analyzer. Second, if you don't have a reference method, you need to find a method which is giving repeatable results and does not burn the sample. For both possibilities, you need to modify the method parameters to get the desired result. Typically, the most important parameter to adjust is the drying temperature.

16. Which sample size do you recommend?

Typically 3 to 5 g is a good sample size which allows covering the complete pan with a thin and even layer and which is giving repeatable and fast results. For samples with very low moisture content (<1%), we recommend using more sample weight to reduce the relative error (e.g. 30 g for plastic pellets), however this requires a longer measurement time. We do not recommend to use less than 1 g of sample as this does not allow even distribution and does not give good repeatability. To ensure best repeatability, we advise always using the same sample weight (± 0.1 g).

20. What is the difference between testing and adjustment? What is calibration?

Testing is the determination of a deviation between the measured value and the true value without making any changes. Adjustment is testing plus making the changes (corrective action) so that the measuring device is correct. Calibration is often used to describe either testing or adjustment but it is unclear what action the user actually means. That's why we distinguish between testing and adjusting to be clear about the action. In case of the moisture analyzer it is for example important to regularly calibrate (test) and adjust the heating unit.

21. How often should I test my moisture analyzer?

The moisture analyzer should be tested whenever it is installed or relocated and in regular intervals. This regular test frequency depends on the individual process risk. The risk is determined by factors such as criticality of the process, the temperature sensitivity of the sample and the customer's level of regulation.