日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) is a soft ionization method used to determine the molecular weight of an analyte. MALDI MS enables us to detect nonvolatile compounds, such biopolymer as proteins and peptides, which are difficult to detect by other ionization methods. Some organic acids such as α-cyano-4-hydroxycinnamic acid (CHCA), sinapinic acid (SA), 2,5-dihydroxybenzoic acid (DHBA), and 2,4,6-trihydroxyacetophenone (THAP) are often used as the matrix. However, these organic matrices dissociate during the desorption/ionization process, thereby limiting the application of MALDI MS to low molecular weight compounds. In addition, the peak intensity of a protonated analyte is sometimes suppressed by an alkali metal ion adducted species. In order to overcome those drawbacks, we have proposed various techniques so far. Especially, we found that zeolites work very effectively on the above problems. In this commentary, we explained how zeolite is effective for laser desorption/ionization mass spectrometry; they enhanced the peak intensity of protonated analyte and suppressed alkaline cation addition peaks. It was also found that analyte can be ionized by adducting alkali metal cations existing on the zeolite surface. Quantitative analysis of drugs and metabolites contained in urine and detecting drugs contained in fingerprints were also presented.