Quantitative determination of compounds in mixtures by B²E=constant linked scans

Abstract

The @E= constant linked scan is shown to be an excellent tool for quantifications with reversed geometry mass spectrometers. Deuterium-labelled analogues may be used as internal standards, thus providing very simple clean-up procedures. The principle is demonstrated with the example of chloro-substituted benzoic acid methyl esters. Possible interferences arising from isotope peaks are discussed. The method is applied to the quantification of caffeine in beverages.

Nucleophilic Catalysis with 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) for the Esterification of Carboxylic Acids with Dimethyl Carbonate

“…All reagents were purchased from commercial suppliers and used without further purification. Methyl esters 2 , 7 , 8 , 9 , 10 , 11 , and 12 are known compounds. The identity of the methylated products was confirmed by 1 H and 13 C NMR and MS spectra.…”

“…We are in debt to Dr. Song Xue for helpful suggestions. We thank Dr. Grazyna Ciszewski for preparing 18 O-labeled benzoic acid. We are grateful to Ms. Noela Reel, Mr. Leonard Hargiss and Mr. Richard Beveridge for their assistance in obtaining chiral HPLC, MS, and NMR spectra, respectively.…”