Espresso, Regular, and De-Caffeinated Coffee Caffeine Content

Caffeine is separated from other matrix components in three common Coffee beverages in this AppNote. A shot of Espresso (Figure A) had the highest content, followed by regular drip Coffee (Figure B) as expected. In De-Caffeinated Coffee, Caffeine is extracted from the coffee beans but even after numerous extractions, Caffeine is not completely removed. This is illustrated by the chromatogram for the De-Caffeinated Coffee sample (Figure C), where a Caffeine peak was detected.

A calibration curve was constructed in the range of 100 – 1000mg / L (Figure D), which provided estimates of caffeine content in the Beverages: Espresso: 964mg / L, Regular Coffee: 539mg / L, and Decaf Coffee: 85mg / L.

Caffeine Content ChromatogramCaffeine Content Chemical Structure
Peak:
Caffeine

Method Conditions
Column: Cogent Bidentate C18 2.o™, 2.2μm, 120Å
Catalog No.: 40218-05P-2
Dimensions: 2.1 x 50mm
Mobile Phase: 90:10 A: DI Water with 0.1% Formic Acid (v/v), / B: Acetonitrile with 0.1% Formic Acid (v/v)
Injection vol.: 0.5µL
Flow rate: 0.3mL / minute
Detection: UV @ 254nm
Sample Preparation: Espresso, Regular, and Decaf Coffee were purchased from a local coffeehouse. The samples were filtered with 0.45μm Nylon Syringe Filters (MicroSolv Tech Corp.). A 1000ppm Caffeine reference standard solution was prepared in a diluent of 50:50 Solvent A / Solvent B. Dilutions were made from this Stock Solution to obtain concentrations of 100, 200, and 500ppm.
t0: 0.8 minutes

Note: Caffeine is a xanthine alkaloid found in the coffee plant, the tea bush, the kola nut, and other plants. It is the most commonly consumed psychoactive drug in the world.

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