Determination of Caffeine in Coffee Products According to DIN 20481

Significance of the Topic

Coffee ranks among the most traded commodities worldwide and caffeine is the principal alkaloid responsible for its stimulating properties. Accurate determination of caffeine content is critical for quality control in coffee production, compliance with labeling regulations and ensuring consumer safety, especially in decaffeinated products that must contain less than 0.1 percent caffeine according to industry standards.

Objectives and Study Overview

This study presents a high performance liquid chromatography method developed in accordance with DIN ISO 20481 for quantifying caffeine in both regular and decaffeinated coffee products. Key goals include evaluation of linearity, precision, accuracy, carryover and overall performance of standard and solvent saver columns with reduced internal diameter.

Methodology

Sample preparation consisted of extracting caffeine from instant coffee granules by stirring with water and magnesium oxide at elevated temperature followed by filtration. Calibration curves were constructed using a caffeine stock solution diluted to cover concentration ranges of 1.25 to 20 milligrams per liter for regular coffee and 0.125 to 4 milligrams per liter for decaffeinated samples. The chromatographic separation employed an isocratic mobile phase of 75 percent water and 25 percent methanol at 25 degrees Celsius with ultraviolet detection at 272 nanometers.

Instrumentation Used

• Agilent 1260 Infinity binary pump with external degasser
• Agilent 1260 Infinity autosampler with thermostat
• Agilent 1260 Infinity thermostatted column compartment
• Agilent 1260 Infinity diode array detector with 10 millimeter flow cell
• Agilent ZORBAX Eclipse Plus C18 column 4.6 by 150 millimeters
• Agilent Poroshell 120 EC C18 columns 3.0 by 150 millimeters and 3.0 by 50 millimeters

Main Results and Discussion

Calibration curves demonstrated excellent linearity with correlation coefficients of 1.0000 and 0.9999 for the high and low concentration ranges, respectively. Limits of detection and quantification were 0.034 and 0.113 milligrams per liter with the standard column and improved to 0.015 and 0.051 milligrams per liter using the solvent saver column. Retention time precision was below 0.2 percent RSD and area precision below 0.4 percent RSD. No carryover was observed after injection of the highest calibration standard. Analysis of real samples yielded caffeine levels of approximately 2 percent in regular coffee granules and below 0.1 percent in decaffeinated products, meeting regulatory criteria. Shortening the core shell column to 50 millimeters reduced run time from twelve to two minutes while maintaining performance.

Benefits and Practical Applications

• Reliable quantification of caffeine for quality control and regulatory compliance
• High throughput analysis through rapid separations and reduced solvent consumption
• Adaptable method suitable for routine testing in industrial and research laboratories
• Capability to distinguish between regular and decaffeinated products with precision

Future Trends and Applications

Advancements may include further reduction of analysis time using ultrahigh performance liquid chromatography and implementation of green solvents to minimize environmental impact. Integration of mass spectrometric detection could expand the method to simultaneous analysis of additional coffee constituents and contaminants. Automated sample preparation and data processing will support higher throughput in quality control settings.

Conclusion

The described HPLC method offers a robust and efficient approach for caffeine determination in coffee products in line with DIN ISO 20481. Use of solvent saver columns enhances sensitivity and reduces solvent usage. The method is well suited for routine analysis and regulatory testing of both regular and decaffeinated coffee.

References

1. Wikipedia contributors Coffee page
2. European Commission Guidelines on labeling of quinine and caffeine containing beverages July 18 2002
3. DIN ISO 20481 Coffee and coffee products Determination of caffeine by HPLC January 2011
4. DIN 10767 Coffee and coffee products Determination of chlorogenic acids by HPLC 1992
5. Agilent Application Note Publication number 5991-2852EN Determination of chlorogenic acids
6. DIN 10779 Coffee and coffee products Determination of 16 O methyl cafestol content by HPLC March 2011
7. Agilent Application Note Publication number 5991-2853EN
8. DIN EN 14132 Determination of ochratoxin A in roasted coffee HPLC method with immunoaffinity clean up September 2009
9. Agilent Application Note Publication number 5991-2854EN