PRECISA UK MOISTURE ANALYSERS
Precisa Ltd. is the leading manufacturer of thermogravimetric analytical measuring equipment. For the most accurate measurements and results, Precisa Ltd. excels with a wide variety of moisture analysers, which meet the highest requirements in research, production and quality control.
Moisture and water content play an important role in the processing and quality of products as well as on the pricing of these products in many industries including pharma products, the food industry, agricultural sector, construction materials etc.
Precisa’s moisture analysers are compact and robust, their use in the lab leads to significant improvements in production and means savings in time and cost. This increase in productivity is brought about by fully automatic moisture analysis’ and corresponding generation of measurement documentation records.
Series 330 XM models all provide high quality, fast, error-free moisture analysis,using highest degrees of precision and measurement performance. Precisa’s Series 330 XM are easy to use, maintain and service friendly. Our moisture analysers are the result of Swiss precision in production and engineering, which guarantees robustness, reliability and an extensive life of error-free operation at highest levels of precision.
When carrying a bucket of water, it is very clear to you, that moisture has weight. You may have noticed that clothes coming out of a washing machine are heavier than when they went in. However, when weighing samples, especially samples that are seemingly dry, it can be less obvious that moisture has weight. Especially as moisture does not just come in the form of water. Water is specifically the H2O molecule whereas moisture is everything that evaporates upon heating including organics, flavorings, fats, alcohol, solvents and other substances. Unfortunately, ignoring this fact can give you incorrect readings. Moisture comes in 3 forms in samples;
- Surface Moisture – If moisture is adhered to the sample surface, it can be called hygroscopic, adhesive or free water. This is the easiest moisture to remove. Although this moisture may not be visible, it is attached to the surface of the sample.
- Absorbed Moisture – This can also be called equilibrium moisture and can be trickier and more time consuming to measure than surface moisture, This moisture has travelled into the pores and capillaries of the sample which are often roughly shaped for example wet soil.
- Chemically Bonded Moisture – This can also be called water of crystallization or hydrated water and it is the most difficult of all to measure. The moisture molecules are bonded at a molecular level and may also have surface and absorbed moisture present. To correctly measure it, Surface moisture, absorbed moisture and chemically bonded moisture must all be accounted for.
Note – Volatile reactions can occur during moisture analysis if explosive or flammable upon heating materials are tested.
Moisture Analyser Defined
A moisture analyser (can also be know as a moisture balance or moisture meter) measures the amount of moisture in a sample. When choosing a moisture analyser, precision, measurement method, capacity and speed should be assessed.
Moisture Analyser Measurement
The most common way to ascertain the amount of moisture in a sample is to weigh the sample before and after removing moisture, the difference between the two giving you the weight of moisture in the sample. This is known as the LOD (loss on drying) method and it is the most commonly used method.
Moisture Analyser Process
There are 3 steps involved in the process. The first is parameters for the drying process are set using the keypad. Then the sample is placed in the drying chamber. Heat removes moisture from the sample, the weight ceases to change when all the moisture is removed and finally the instruments shuts off the heat and uses the final weight to calculate the LOD. The LOD (also known as the gravimetric loss) is then found by comparing the initial weight to the final sample weight.
Moisture Analyser Components
This means moisture analysers are made up of two critical components, a balance to capture the initial and end weight and a heat source to heat the sample. The heater is mounted on the balance along with a control panel and display.
Moisture Analysers are highly programmable to facilitate new QC procedures and to conduct analysis according to set standards. Parameters must be set such as drying time, sample weight and temperatures. Moisture Analysers are highly beneficial because once the analysis method has been configured, minimal training and expertise is required when using the analyser. Moisture Analysers have memory storage which means users can build a library of frequently used analysis programs.
The display shows the user if the process is active or complete, the current moisture content, current weight, drying mode and switch off mode. Switch off criteria will be set as a parameter will vary depending on the experiment being run. The most common criterions for shutoff are when the drying and analysis is complete, after a specific period of time or if the moisture analyser is manually switched off.
Importance of Moisture Analysis
Moisture content of a product affects the vast majority of industries including the pharma, food, plastics, wood, paper, textiles and agricultural industry. Moisture is a quality control criterion which affects weight, shelf life, pricing and quality. Consumers will not want to buy products with excessive amounts of water as they will not feel they are getting value for money. Products with a high moisture content will have a shorter shelf life due in increased opportunity for microbial activity. Laws and regulations set the correct moisture content for industry products.For highly regulated products such as pharmaceuticals, moisture content must be strictly controlled.
Moisture Analysers are in high demand as they offer an extremely quick way to analyze moisture. The standard alternative is using a drying oven which is very time consuming and can take 6 hours to find the moisture content. Moisture Analysers are an acceptable alternative to drying ovens as long as it can be shown the results from the drying ovens and the moisture analysers are the same. Often customers use both methods in order to verify a result.
Moisture Analyser Methods
A moisture Analyser method outlines the exact procedure to be followed when determining moisture content. This includes setting parameters such as temperature, drying program, sample weight, criteria for switching off and start and display mode. Sample preparation and sample application should also be set.
These methods are needed to accurately obtain reliable moisture content results that are repeatable from the moisture analyser (known as a reference method) or else match the drying oven results (known as a reference result).
- Correct sample preparation is integral to fast, repeatable and reliable results. Sample preparation involves taking a sample which is representative of the full batch of what is being tested.
- The sample should be tested straight after being obtained from the batch as the could gain or lose moisture from the environment in the meantime. There should be an granulation of the sample to ensure even distribution and sample surface of the sample.
- Small particles will analyze quicker due to the increased surface area.
- Optimum sample weight is found through trial and error and varies depending on the product. In general, sample sizes should evenly cover the bottom of the pan and usually weigh between 3-5g. Large sample sizes will not lead to more accurate readings, in fact it may inhibit an accurate reading. Weight should be increased if samples are expected to have a very low moisture content. Samples ideally should not be less than 1g as repeatability and distribution are difficult to accurately measure from such a small sample.
- If a sample has high moisture content (e.g. liquids), they should be placed between fiberglass filters in order to prevent splattering and increase surface area.
Testing the Moisture Analyser
As with all precision measurement devices, Moisture Analysers should be tested regularly for accuracy, especially during installation or if the analyser has been moved to a new location. When a moisture analyser is bought, the effect of gravity where it was made will likely be different to where it has been shipped to so even though the analyser is brand new, it will need to be calibrated. When a moisture analyser is moved to a new location, changing environmental factors can affect results. Air conditioning, heating and noise vibrations mean that even moving a moisture analyser from one table means the device should be calibrated.
Two components of a moisture analyser must be calibrated. The scales which records weight must be calibrated and temperature calibration must be carried out on the heaters. Frequency of testing depends on the temperature sensitivity of the product, the regulation surrounding the product being tested and the criticality of the process.
Moisture Analyser Maintenance
- Moisture analysers should be kept away from drafts, temperature discrepancies, vibrations and dusty conditions.
- A soft brush should be used to clean up samples that fall off during the analysis
- Accessories such as the dish, the dish container and holder should be washed gently using a cloth and washing up liquid (no other solvents should be used).
- After cleaning the components should be wiped with a clean wet cloth and dried with another cloth.
- Extreme care should be used when cleaning the temperature sensor. Simply wipe and dry with cloths and avoid touching the lamp.