This white paper provides practical guidance on how to provide evidence that the results of the moisture analyzer are comparable to the drying oven and that the instrument is fit for purpose.
USP <731> ("Loss on Drying"), AOAC and ISO describe the thermogravimetric method using a drying oven as a standard procedure for determining moisture content.
A Valid Alternative to the Drying Oven
An alternative thermogravimetric procedure that provides comparable results to the drying oven in a considerably faster time is conducting loss on drying (LOD) with a moisture analyzer. Results are delivered in 5-15 minutes, in contrast to the drying oven, which typically takes 2-3 hours. The procedure is also far simpler and doesn't require specialist skills. By validating the results of halogen moisture analysis against those from the drying oven, companies can benefit from a convenient and compliant alternative loss on drying solution. The European Pharmacopeia has recently updated Chapter 2.2.32, "Loss on Drying", to include halogen moisture analyzers as an acceptable alternative to the drying oven reference method.
Want to Develop a Robust LOD Moisture Method?
Our reference paper will guide you through the setup of a robust moisture method for your sample including the right sample preparation and sample application.
How to Ensure Reliable Moisture Analysis Results
As with the drying oven, the key to achieving accurate results lies in the development of the drying method. Different samples require different drying methods according to the individual sample properties. A robust drying method includes sample preparation, a suitable drying temperature, the appropriate drying program, and the right switch-off criterion.
Take advantage of METTLER TOLEDO's moisture analysis expertise to improve your moisture analysis processes. Explore the links below to see our wide range of tools and our application method library. Take a look at our range of moisture analysis instruments to discover which one best suits your company's needs.
Navigation:
- WhitePaper – Drying oven versus moisture analyzer
- Method Development Support & Application Search
- Moisture Technology Comparison
- Industry Solutions
- FAQ
Need to Switch from the Drying Oven to a Moisture Analyzer?
Moisture Method Development
To find a suitable LOD moisture method you need to understand the characteristics of your sample and choose suitable method parameters such as the drying program, drying temperature and switch-off criterion. In addition it is important to understand the best sample preparation method for fast and reliable measurements.
The Method Wizard, a feature included in the HX204, HS153 and HC103 Moisture Analzers, helps you find the right method for your sample in three simple steps:
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Step 1: Questionnaire
The Method Wizard proposes moisture method parameters such as drying program, drying temperature and sample handling accessories based on information regarding the consistency and behaviour of the sample. Other attributes and requirements are also covered.
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Step 2: Temperature assistant
Based on the target moisture content and a measurement using the proposed method from step 1, the temperature assistant refines the method and proposes an optimized drying temperature for the sample.
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Step 3: Test Measurement
A test measurement is run to verify the optimized method, and to determine a suitable switch-off criterion (SOC). If none of the pre-set SOC are suited, some instruments offer a customizable option to fine-tune the method further.
How to Use the Search Function
To find your application use the filters for 'Sample', 'Industry' or use full text search. Any combination of filter and full text search is possible. Note that the full text search yields only matches that include the exact word sequence of your query.
Moisture Method Application Search
Check our proven and well-tested moisture methods in our application library to get a suitable starting point for your own method development. The moisture method datasheets describe method parameters, including sample preparation, for both the moisture analyzer and the reference method (e.g. drying oven procedure).
Reliable and Fast Moisture Analysis
METTLER TOLEDO is an expert in moisture analysis and offers a wide range of reliable and easy to use moisture analyzers to suit the needs of quality control, production and in-process control of many industries, such as pharma, plastics and the food industry.
Moisture Technology Comparison
Drying Oven
Principle:
Thermogravimetry
Measuring Method
Heating of sample by convection. Sample is dried in the oven for a defined period of time at constant temperature. Mass is determined before and after drying. The moisture content percentage is determined from the difference in weight before and after drying.
Advantages
● Often reference procedure (for historical reasons this procedure often forms part of legislation)
● Several samples can be determined at the same time
● Large sample volumes possible
Disadvantages
● Very long determination period (hours)
● Substances other than water may evaporate
● Prone to errors because of the high level of manual handling and calculations involved
● Unsuitable for at-line use - requires analytical balance and dessicator
Halogen Moisture Analyzer
Principle:
Thermogravimetry
Measuring Method
Heating of sample through absorption of IR radiation from a halogen radiator. Continual determination of mass during drying process. The moisture content percentage is determined from the difference in weight before and after drying.
Advantages
● Quick measurement (typically 5-15 min.)
● Simple handling, no manual calculations
● Compact instrument. No balance or desiccator required
● Suitable for at-Iine use
Disadvantages
● Substances other than water may evaporate
Principle:
Chemical Oxdiation Reaction
Measuring Method
The chemical reaction of water with a Karl Fischer reagent (containing Iodine and Sulphur Dioxide) is monitored with a polarized sensor to determine the water content. This is either performed volumetrically, with the addition of the reagent measured, or coulometrically, where the reaction is driven in-situ and is proportional to electrical current applied.
Advantages
● Water specific, no other solvent or "moisture" determined
● Fast, typically 0.5 to 3 mins per sample
● Measure from 2ppm to 100% water
● Compact instruments, automatic calculations, connect Mettler Toledo balances for complete result calculations
Disadvantages
● Requires dedicated chemicals and chemical know-how
● Sample preparation can be critical for complete water extraction (homogenizer, long extraction times)
Industry Solutions
Moisture Analysis in Pharmaceuticals
See how easy it is to measure the moisture content of pharmaceuticals in the lab or directly on the production floor with a halogen moisture analyzer.
Moisture Analysis in Chemicals
Learn how moisture analyzer is used to reliably measure the dry content in chemical industry. Free moisture method with comparison to reference method
Moisture Analysis in Food
In our collection of moisture methods for the food industry, you'll find over 20 moisture determination methods for samples in the food and bakery industry.
Moisture Analysis in Waste Water
Precise determination of Total Solids in wastewater is a key driver for the operational efficiency of wastewater treatment facilities. Read our application note to learn more.
Moisture Analysis in Plastic Pellets
Our plastics method collection provides moisture methods for the most common plastic resins and compares them to the Karl Fischer titration method.
Moisture Analysis in Wood Pellets
Learn where and how moisture content is measured in the wood pellets production process and benefit from our methods and tools for measuring moisture content in wood.
FAQ - How to Develop a Moisture Method
Frequently Asked Questions on Moisture Method Development
Select your Question
- We have to use the standard method with the drying oven but using a moisture analyzer would really speed up our processes. Is it possible to switch to a moisture analyzer?
- How do the results on the moisture analyzer compare to the standard method?
- Why do I need to do method development?
- How do I develop a loss on drying method on my moisture analyzer for my substance?
- What is the drying oven method?
- How are samples heated in the drying oven and in the moisture analyzer?
- I have many different samples (liquid, paste-like, solid, powder). Which technique should I use for moisture content determination?
1. We have to use the standard method with the drying oven but using a moisture analyzer would really speed up our processes. Is it possible to switch to a moisture analyzer?
Many industry regulations require manufacturers to follow a standard method. However, it is acceptable to use a moisture analyzer if you can show its results are similar (accuracy and repeatability) to those from the drying oven procedure. This requires developing a drying method for the moisture analyzer and cross-validating it against the drying oven through a series of analyses.
2. How do the results on the moisture analyzer compare to the standard method?
In most cases, the moisture analyzer can deliver an equivalent loss on drying moisture result, and typically better repeatability, in much less time, making it a fast alternative to USP <731> ("Loss on Drying") and ASTM D6980 – Standard Test Method for Determination of Moisture in Plastics by Loss in Weight – and other industry standards. METTLER TOLEDO's application database contains over 150 free ready-to-use cross-validated drying methods. Contact us if you don't find what you need.
3. Why do I need to do method development?
A good moisture result heavily depends on a good and robust moisture method. There is no one-size-fits-all method for moisture content determination as the samples vary greatly in properties. To develop a reliable moisture method the sample at hand therefore should be understood and a loss on drying method, including sample preparation and presentation, that fits the sample should be developed.
4. How do I develop a loss on drying method on my moisture analyzer for my substance?
In general there are two ways to find a suitable LOD method for your sample. If you already have a reference value (e.g. from the drying oven or other moisture/water determination procedure) you can orient your method development to target this reference value. If no reference value exists, try finding a method that dries your sample in a repeatable and fast manner. Consult our reference paper, which guides you through the setup of a robust moisture method for your sample, including the right sample preparation and sample application. If you own a METTLER TOLEDO moisture analyzer (HX204, HS153 or HC103) use the integrated Method Wizard functionality that guides you step-by-step to a reliable moisture method with minimum effort.
5. What is the drying oven method?
The drying oven method is a thermogravimetric method (loss on drying) in which the sample is dried for a defined period of time at constant temperature. The moisture content is determined by weighing the sample before and after drying and determining the difference.
6. How are samples heated in the drying oven and in the moisture analyzer?
In the drying oven, samples are heated by convection. This means the samples are at the same temperature as the drying oven. When using a moisture analyzer, the sample heats up and dries by absorbing infrared radiation from the heating element. The sample's temperature and drying time depends on its absorption characteristics.
7. I have many different samples (liquid, paste-like, solid, powder). Which technique should I use for moisture content determination?
In general, all kinds of samples are suitable for both the drying oven and the halogen moisture analyzer. Which method is best for you depends on how fast you need the result or if you need the result using an official method. Sometimes, for example, at goods-in or during final product quality control, moisture analyzers are used in parallel with a drying oven. Fast analysis with the moisture analyzer is done to optimize processes and the drying oven is used for official documentation purposes.