Guide to Moisture Analysis - With Halogen Moisture Analyzers

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Technical Terms

Thermogravimetric Moisture Determination

Moisture (moisture content) In thermogravimetric processes the moisture of a material includes all substances which volatilize during warming and therefore contribute to the material's loss of mass. Alongside water this may also include alcohol or decomposition products. When using thermogravimetric measurement methods (drying using infrared, halogen, microwaves or ovens) no distinction is made between water and highly volatile components.	Page Content Moisture (moisture content) Dry content Thermogravimetry Reference procedure Drying oven procedure Level of dryness Method Infrared (radiation) Correctness Precision Repeatability Accuracy Reproducibility Qualification (EQ) Validation Calibration Adjustment Precision with Highspeed The Halogen Moisture Analyzers offer both precision and speed. You save time and costs and increase efficiency. Request more information Industry Solutions Plastics industry Sugar industry Food industry Wastewater industry Method Database Find the method for your sample Guide to Moisture Analysis Request brochure
Dry content Solid proportion of a mixture made up of solid and liquid substances in relation to the mixture's total mass.
Thermogravimetry / thermogravimetric moisture determination Thermogravimetric processes are weighing-drying methods in which the samples are dried until a constant mass (or defined time) is reached. The change in mass is interpreted as released moisture. Note: If the substances contain other volatile components in addition to water, the measurement result must not be described as water content. However, if you know the water content of such a sample (e.g. using water-selective Karl Fischer titration), you can determine this value using a thermogravimetric process (e.g. halogen drying) by selecting appropriate drying parameters.
Reference procedure Measurement process for determining the moisture content which allows for traceability to (statutory) standards. Different components (water, other volatile substances) can be measured depending on the reference procedure used.
Drying oven procedure Thermogravimetric method for determining the moisture content of a sample. This sample is dried in the oven for a defined period of time at constant temperature. The moisture content percentage is determined from the difference in weight before and after drying. For historical reasons this procedure often forms part of legislation (Food regulations, USP¹⁾ etc.) ¹⁾ USP United States Pharmacopeia: Loss on drying [USP<731>]
Level of dryness A sample's level of dryness is the defined decrease in weight (Δ g) during a defined time unit (switch-off criteria) assuming the start weight is always the same.
Method A method describes how the correct result is achieved. This includes all the steps required, such as device settings, selection of measurement parameters, preparation and processing of samples.
Infrared (radiation) Infrared rays are electromagnetic waves (780 nm to 1mm) which come after visible light (380-780 nm) in the electromagnetic spectrum. People cannot see these rays but they are perceived as warmth.
Correctness Qualitative term, describing a judgement of the systematic deviation of measurements. The extent to which the expected value (mean value) of a series of measured values matches the true value of the object being measured ([ISO²⁾ 5725] 3.7). Note: The correctness can be evaluated only when there are several measured values, as well as a recognized correct reference value. ²⁾ ISO International Standards Organization
Precision Qualitative term, describing a judgement of the mean variation of measurements. The extend to which independent measured values obtained under stipulated coniditions match one another ([ISO 5725] 3.1.2). Precision depends only on the distribution of random deviations and does not relate to the true value of the measurement variable (accuracy). Example: The ability of a measuring instrument to supply measured values that seldom deviate. Note: Precision can be evaluated only when there are several measured values.
Repeatability Extent to which results from a series of measurements of the same measured quantity, carried out under the same measurement conditions, match one another. The series of measurements must be carried out by the same operator, using the same method, in the same position on the support (sample pan), in the same installation location, under constant ambient conditions and without interruption. The standard deviation of the measurement series is a suitable measurement for expressing the value of the repeatability. The degree of repeatability is not only a characteristic determined by the Moisture Analyzer. Repeatability is also affected by the ambient conditions (drafts, temperature fluctuations, vibrations), by the sample and by the consistent preparation of the samples. Mean value: x_i = i-th result of the series n: number of measurements, usually 10 The standard deviation s is used as a measure of the repeatability.
Accuracy Qualitative name for the degree to which test results approximate to the reference value, which can be the correct or expected value, depending on the definition or agreement [DIN³⁾ 55350-13]. Accuracy in repeated measurements requires correctness and precision. This does not necessarily apply to an individual measurement. ³⁾ DIN German Institute for Standardization
Reproducibility The degree of approximation between the measured values of the same measured variable, even though the individual measurements are carried out under different conditions (which are specified) with regard to the measurement process the observer the measuring device the measuring location the conditions of use the time
Qualification (Equipment Qualification) Check and documentation of whether the equipment and the technology used are suitable for the intended task. The following stages are combined under Equipment Qualification (EQ): Design Qualification (DQ), Installation Qualification (IQ), Operational Qualification (OQ), Performance Qualification (PQ) and Maintenance Qualification (MQ). DQ: Definition of the requirements of equipment specifications and documentation of the decision-making process. IQ: Assurance and documentation that the equipment supplied corresponds to the ordered specifications and that the equipment is installed correctly and the surroundings are suitable for operation. OQ: Documentation of the equipment's functionality according to the defined specifications. PQ: Documentation that the equipment satisfies the requirements and specifications of routine operation. MQ: Description and documentation of all the measures needed for the planned maintenance, periodic calibration, care of the instrument and user training.
Validation The provision of evidence and its documentation to show that a device (or a method) delivers the result expected.
Calibration (testing) Determining the deviation between the measured value and the true value of the measurement variable under specified measuring conditions without making any changes (adjustment).
Adjustment Adjustment of the measuring device such that the measurement is correct: First the deviation is noted between the measured value and true value (calibration), then the corresponding correction is undertaken.