Special Samples

Certain samples need a special procedure for quickly and correctly determining moisture. This section contains information about how you can work with such samples to optimize moisture determination.

Paste-like, greasy and melting samples

  • Use the glass-fiber filter to increase the surface area of the samples.
  • Tare the filter with the sample pan and then place the sample on it.

The liquid contained in the substance is evenly spread over the whole area of the filter in the filter's capillaries. This increases the sample's surface area and the moisture can then evaporate quickly, easily and fully.
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Guide to Moisture Analysis

Liquid and very moist samples

  • Schublade-u-Tropfen.jpgUse the glass-fiber filter.
  • Tare the filter with the sample pan and then place the sample on it.
  • Rapid drying is suited to samples with a very high moisture content (> 30%). In this process, the target temperature is exceeded by 40% for 3 minutes to accelerate the measuring process.
  • Step drying (HR83 only) can be used as an alternative to fast drying. Here the duration of the temperature increase and the temperature are freely selectable.

Because of surface tension, liquid samples often form drops on the sample pan. This prevents a fast drying process because evaporation takes place over a limited liquid surface area. Using the glass-fiber filter spreads the sample over a large area. This often more than halves the duration of the measurement and better repeatability is also achieved.

Samples with very low moisture content (MC < 1%)

  • Use a sufficiently high sample weight (e.g. 20-30 g).
  • If the moisture only escapes very slowly, use switch-off criterion 5 (1mg/140s).
  • Use a high resolution (0.1mg) (HR83 only).
  • Use standby temperature (HR83 only).
  • Preheat sample pan for 1 minute at standby temperature and then tare. This improves the repeatability of the results.

Substances which form a skin and are sensitive to temperature

  • kruste2b.jpgSelect the gentle drying program.
  • Use the glass-fiber filter (tare the filter along with the sample pan and then cover the sample with the filter from above).

This means that the sample is covered by the glass-fiber filter and therefore shielded from IR radiation to prevent burning. This results in the sample being warmed more gently. Using gentle drying (slow heating to target temperature) increases this effect. We would also recommend this process for substances that form skins or crusts because the skin or crust impairs moisture evaporation. The formation of crusts is prevented by covering the sample with the glass-fiber filter and gentle drying.

Samples containing sugar

  • Select moderate temperature. Samples containing high levels of sugar will caramelize on the surface (above around 110°C) and thereby prevent moisture from escaping.
  • Use gentle drying.
  • Apply thin coat of sample.

Samples with highly volatile components

  • Work with manual start.
  • Use gentle drying if necessary.
  • If the vapors are toxic, run a risk analysis and work under a fume cupboard.
  • If samples or vapors are highly flammable, run a risk analysis and, if necessary, do not use the Halogen Moisture Analyzer for drying.
  • Standardize the processing of the samples (the weighing-in period before the start of the measurement should always be the same) to improve repeatability.
Highly volatile samples which contain solvents (note Safety Information) may lose weight before you start the drying process. This will distort the result. The sample should therefore always be processed in the same way (e.g. speed) so that any deviation is as low as possible.

Rapid heating and therefore rapid evaporation of the sample may also result in condensation forming under the sample pan. Using the manual start or gentle drying may reduce condensation levels as well as prevent a high concentration of highly volatile vapors.

Bulky or intumescent samples

  • Probenkaefig leer.jpgUse the sample pan for bulky samples (HA-CAGE)

Intumescent samples or those which are bulky, such as textiles, may produce incorrect measurement results as they but up against surrounding parts of the Halogen Moisture Analyzer. We recommend that you use the HA-CAGE to dry such samples.

Unevenly colored samples

  • shirt-mitschirm.jpgCover the sample with the glass-fiber filter.
Because of the different absorption characteristics, the sample heats up to different levels in different areas. The glass-fiber filter ensures even warming.

Plastic granules

  • High resolution (0.1 mg, HR83 only)
  • Standby temperature (100 °C)
  • Step drying (1st step: 5 min, 2nd step: 0 min)
  • Switch-off criterion 5
  • 30 g sample weight
  • Heat the aluminum sample pan for 1 minute at standby temperature, and then tare it.
Plastic granules usually require a very low moisture content (e.g. 0.1%) for processing (e.g. injection molding). A high sample weight of 30 g is therefore needed to obtain good repeatability. Step drying is used because plastic loses moisture very slowly. The sample is heated for the 5 minutes of the first step without the switch-off criterion becoming active. The second step is not needed and is therefore set to 0 minutes. The switch-off criterion is only active once these first two steps have been completed. Using step drying therefore prevents
the measurement being aborted prematurely.