Many scientists consider hydrochloric acid in anhydrous methanol a mild and useful derivatization reagent [59]. An almost quantitative yield was reported by Stoffel et al. [248] for the transesterification from glycerides, phosphatides, and cholesterol, to FAMEs. Concentrated sulfuric acid in anhydrous MeOH can be used instead of MeOH–HCl for the methylation of FFAs [297], and the transesterification of BFAs from triglycerides [298] and fats [299]. Low recoveries of hydroxy FAs can be expected when sulfuric acid-MeOH is used [300]. Methyl methoxyisomers have been reported to result from rigorous esterification with MeOH–sulfuric acid. Hydroxy fatty acids represent a significant fraction of FAs in bacterial LPS, so methylation with MeOH–sulfuric acid should be avoided.