Comparison of metal oxide catalysts for pyrolytic MOLI-MS bacterial identification

Six metal oxide catalysts were investigated for effective cleavage and laser ionization of bacterial cell wall phospholipid extracts. Calcium oxide has been utilized in the past for this application, but suffered from degradation of catalytic activity. Following evaluation of the six catalysts, CeO2 was found to be the most stable over time and produced fatty acid profiles of bacterial pathogens similar to freshly activated CaO. A suite of ten bacteria previously studied using CaO catalysis provided cross validation results of analysis of 97% correct correlation for negative-ion data. Cerium oxide catalysis studies yielded cross validation results of 100%. Using analysis of variance-principal component analysis (ANOVA-PCA), four sample sets collected with stored catalyst at 0, 8, 24, and 504 h showed no effect based on long-term catalyst degradation. Supervised learning by a fuzzy rule-building expert system (FuRES) that was validated with training and prediction set partitions independent of CeO2 age and unsupervised data analysis using a dendrogram of Euclidean distance confirmed that the CeO2 catalyst age had no effect on the fatty acid mass spectral profiles.