Standard addition strip for quantitative electrostatic spray ionization mass spectrometry analysis: Determination of caffeine in drinks.

• We propose rapid and accurate quantitative analysis of caffeine using standard addition strip-ESTASI-MS.
• The standard addition strip-ESTASI-MS method was compared with classical standard addition methods for MS and LC.
• The standard addition strip is low cost, single use and no cross-contamination takes place during the analysis.

Standard addition strips were prepared for the quantitative determination of caffeine in different beverages by electrostatic spray ionization mass spectrometry (ESTASI-MS). The gist of this approach is to dry spots of caffeine solutions with different concentrations on a polymer strip, then to deposit a drop of sample mixed with an internal standard, here theobromine on each spot and to measure the mass spectrometry signals of caffeine and theobromine by ESTASI-MS. This strip approach is very convenient and provides quantitative analyses as accurate as the classical standard addition method by MS or liquid chromatography.

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