Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) is a critical analytical technique employed to determine the moisture content of various materials. This method involves the use of a laser to desorb and ionize molecules from a sample, enabling the analysis of their mass-to-charge ratios.

Principle of MALDI-MS

• A small sample is placed on a metal plate and covered with a matrix, a light-absorbing compound that facilitates ionization.
• A pulsed laser beam is directed onto the sample, causing the matrix to absorb energy and vaporize rapidly.
• During vaporization, molecules from the sample are desorbed and ionized.
• The ionized molecules are then accelerated into a mass spectrometer, where they are separated based on their mass-to-charge ratios.

Advantages of MALDI-MS for Moisture Content Determination

• High Sensitivity: MALDI-MS can detect very small amounts of moisture in samples.
• Wide Applicability: This method can be used to determine the moisture content of a wide range of materials, including pharmaceuticals, food products, and polymers.
• Non-Destructive: MALDI-MS does not damage the sample, allowing for further analysis.
• Rapid and Automated: The automated process of MALDI-MS enables efficient and high-throughput analysis.

Official Methods of Moisture Content Determination Using MALDI-MS

• ASTM D6989: Standard Test Method for Determination of Moisture Content of Pharmaceuticals by Loss on Drying
• USP<633>: Moisture Determination
• AOAC 950.46: Moisture in Spices (Direct Reading Moisture Analyzer)

Summary

MALDI-MS is a valuable technique for determining the moisture content of materials due to its high sensitivity, wide applicability, non-destructive nature, and rapid and automated process. The official methods mentioned above provide standardized guidelines for using MALDI-MS for moisture content determination, ensuring accuracy and reliability.