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Moisture content determination is an important quality control test in pharmaceutical manufacturing, from the checking of incoming raw materials and in-process control of tablets and capsules to undertaking quality checks of finished drugs as part of pharmacopeial testing procedures. Moisture testing is also one of the critical quality parameters in the stability testing of drugs.
METTLER TOLEDO halogen moisture analyzers improve quality control throughout the entire pharmaceutical drug manufacturing process with fast and accurate moisture measurements. The halogen moisture analyzers are in line with regulations as a viable alternative method for determining moisture content and deliver fast and accurate moisture content measurements in pharmaceutical applications.
Moisture in pharmaceuticals
Moisture content in raw materials such as Active Pharmaceutical Ingredients (APIs) and excipients is an important factor during blending and granulation in the production of drugs. Moisture content affects overall flow properties and the consistency of blended powders. For finished tablets and capsules, moisture content is one of the quality parameters that accounts for mechanical strength, solubility and overall shelf-life stability.
In-process quality control
Granulation is an important step in tablet and capsule manufacturing. After wet granulation, the powders are dried. At this critical point in the process, the residual moisture content is measured.
In tablet manufacturing, the amount of moisture in the composite materials must be carefully controlled to ensure the overall shape, strength, solubility and shelf life of the tablets. As an important quality factor, moisture content is measured prior to tablet pressing; if the mixture is too dry, the tablets will be unstable and if too wet, the pressing machine may clog.
![]() ![]()  Fig. 1. Measurement points for moisture content during the tablet manufacturing process
In the manufacture of gelatin-based capsules, moisture is an important quality parameter for holding strength and solubility of the capsule. Moisture is typically measured in the raw gelatin powder and the empty gelatin capsule.
Final quality control
Testing moisture content in tablets and capsules is governed by pharmacopeial regulations, which specify the “Loss on Drying“ (LoD) test using a conventional drying oven. However, moisture content testing using a drying oven typically takes at least two to three hours, presenting a dilemma for pharmaceutical manufacturers as the results are important to the production process and for batch release. Fortunately, this challenge can be overcome using an alternative method as long as the method is demonstrated to be fit for purpose and provides comparable results to the official method.
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Halogen moisture analyzers for fast, accurate and comparable results
METTLER TOLEDO halogen moisture analyzers are based on the principle of thermo-gravimetry (similar to LoD), but results are provided in minutes instead of hours. This allows pharmaceutical companies to optimize processes and assists with the faster release of batches of finished products. They are a viable alternative method for LoD testing, and may be validated as per individual pharmacopoeia guidelines. The white paper, “Drying Oven vs Halogen Moisture Analyzers” 3) provides stepwise guidance on producing and validating comparable results to the reference method.
Comparison of moisture content results using an HX204 and a drying oven
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HX204 – Fit for regulatory demands
The HX204 halogen moisture analyzer from METTLER TOLEDO complies with regulatory aspects of quality testing in a pharmaceutical environment. Features such as user management, method assignment, control limits and performance testing at point of use make it the best-fit choice for working within a highly regulated environment. Additionally, the HX204 assists companies to achieve data integrity based on ALCOA+ principles by supporting paper and PDF processes.
(Author is PhD in Chemistry, Manager, Mettler Toledo, Moisture Solution Delivery)
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