Qualitative and Quantitative Analysis of Stimulants and Antibiotics by MALDI-TOF Mass Spectrometry through Charge Derivatization

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Peter J. Lee, Weibin Chen, John C. Gebler [Waters]
Fall ACS 2003, 226th ACS National Meeting; New York September 7-11
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Norfloxacin, Ciprofloxacin, lomefloxacin, Antibiotics
Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) is a powerful tool to analyze large biomolecules and synthetic polymers. However, qualitative and quantitative MALDI-MS analysis of small analytes (m/z < 500 Da) remains a challenge. Our strategy to analyze small targeted molecules was to use a simple and efficient coupling reaction to derivatize analytes with a large charged tag. A pair of isotopically coded light and heavy tag reagents of tris(2,4,6-trimethoxyphenyl)phosphonium acetic acid N-hydroxysuccinimide ester (TMPP-Ac-OSu) were developed, adding 573 and 600 Da respectively to each analyte with a fixed positive charge. A variety of primary and secondary amines, amino acids, peptides, drugs, antibiotics, and stimulants were derivatized and analyzed by MALDI-MS in the low femtomole range successfully. Quantitative analysis of mixture of antibiotics such as norfloxacin, ciprofloxacin, lomefloxacin by MALDI using isotopically coded light and heavy tag labeling method was demonstrated. Linear calibration curves of antibiotics from 0.3 to 30 pmol/µL with r-squared values greater than 0.9995 were achieved. In this presentation, a systematic evaluation of analyzing small molecules by MALDI-MS through charge derivatization is described.

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