Controlling water content is essential in many biological and chemical applications, including food, pharmaceuticals, and hydrocarbon processing. A moisture analyzer is used to quantify water content. However, depending on the state (solid, liquid, or gas) of the samples, different methods are required. In this article, we will explore the use of moisture analyzers for various quality control applications.
Food and agriculture
Moisture control in food is critical because too much moisture may promote growth of harmful microbes, while too little moisture may affect the consistency and taste of the food.
The water content in solid or semi-solid food can be measured using moisture analyzers with the loss on drying method. In this method, the sample is weighed, dried, and weighed again. The difference in weight is the mass of water. This is achieved by moisture analyzers with a precision electronic balance and a sample tray surrounded by a heating element. The whole process can be automated and with the use of a microprocessor, heating can occur rapidly and uniformly.
Pharmaceutical companies have to ensure consistent products. Drugs in the form of pills will agglomerate or lose their bioactivity with too much moisture. With too little moisture, they may lose their shape and form. Karl Fischer coulometry is commonly used for pharmaceutical applications. It involves the conversion of solid iodine (black) into hydrogen iodide (colorless) when iodine reacts with water. The reaction finishes when no more water is left. As this reaction is water-dependent, atmospheric humidity could easily affect the results. Hence, the system is usually performed in a container with inert gases like dry nitrogen. Note that Karl Fischer coulometry can also be used for liquid and gas samples. Liquid sample can be injected directly into the analysis tube or cell while a special setup is needed for gas samples, such as in the petrochemical industry.
Moisture analyzers are used in almost all stages of hydrocarbon processing in the oil and gas industry. They are used to analyze water content before natural gas liquid extraction and to detect for trace moisture before liquified natural gas liquefaction. Furthermore, as moisture can affect the performance of refining catalysts, a moisture analyzer is used to prevent catalyst contamination during oil refining. Further downstream, moisture control is essential to petrochemical production (such as polymer and rubber) for quality control of material properties like viscosity.
Due to the precious nature of hydrocarbons, moisture analyzers with hygroscopic quartz crystal are used for more accurate measurements. Based on the differences in vibrational frequency of the quartz crystals and by comparing that to a calibration curve, the water content in the gas sample can be determined.
The water content in samples can be determined by mechanisms involving changes in color, mass, light, and even electrical signals. In addition to the applications discussed, moisture analyzers are used in many other industries such as semiconductors, paper production, and metal processing. This instrument is very helpful to provide quality control to ensure product consistency.