pH in Coffee

Smartphone-based determination of pH after reaction with a chemically bound pH indicator

Introduction

Analyze your MQuant^® test strips with your smartphone for fast, convenient, and precise results. Test the simplest way to determine pH in aqueous solutions. This low-priced and easy-to-use analytical detection system provides reliable quantification of water, food & beverage samples for customers from research, industry, environment, and diagnostics.

The following application note describes the determination of coffee pH value using the MQuant^® pH test strips in combination with the MQuant^® StripScan App.

Reagents, Instruments and Materials

Reagents

• MQuant^® pH-indicator strips 0-14 Universal indicator (1.09535)

Accessories

• MQuant^® Card (provided with the test strip box)
• MQuant^® StripScan App (can be downloaded via the Apple App Store or Google Play Store)

Experimental

Method

Special indicator dyes are covalently bound to the reagent papers, which changes the color depending on the pH value of the sample.

Measuring range

• pH 0–14

Sample material

• Coffee

Sample Preparation

• Brew the coffee according to the user specific procedure. For pH measurement, the coffee must be used undiluted.

Measurement— pH of Coffee

For analysis, follow this procedure:

• Start the App.
• Get your MQuant^® test strip and the MQuant^® Card ready.
• Dip the test strip into the undiluted sample (15–25 °C) for ca. 2 seconds, ensuring that the reaction zone is completely immersed.
• Shake off excess liquid from the strip and dry the backside of the strip using a paper towel.
• Select the parameter pH (1.09535) in the app. Wait 15 seconds until the color of the pH strip has completely developed (a countdown is displayed on the screen, which begins immediately after selecting the parameter pH).
• Just before the end of the countdown, place the test strip on the MQuant^® Card.
• After the waiting time has elapsed, place the MQuant^® Card with the test strip within the viewfinder on your phone screen, and align the camera along the reference points.
• The picture is captured automatically by the camera of the smartphone.
• The result is displayed on the screen.

Results

Comparison with visual evaluation, Reflectoquant^® pH test (1.16996), and pH electrode:

*Results are based on the average of a 5-fold determination

	pH value
Sample	StripScan*	Visual readout*	Reflectoquant®*	pH electrode
Filter coffee	5.0	5	5.1	5.28
Coffee prepared in coffee machine	5.0	5	5.2	5.39
Coffee prepared from coffee concentrate	5.0	5	5.0	5.12

Note: Result graduation provided by MQuant^® StripScan is identical to graduation on the test strip package. (The results above were obtained using the previous app version with its graduations of 0.5 pH units)

Conclusion

The MQuant^® pH strip in combination with the MQuant^® StripScan app is a quick and easy way to analyze the pH value of coffee. The measured values are comparable to those measured with the Reflectoquant^® pH test (reflectometry) and the pH electrode.

For more information

• MQuant^® StripScan see SigmaAldrich.com/mquant-stripscan
• MQuant^® pH Indicator Test strips see SigmaAldrich.com/phtests
• Applications see SigmaAldrich.com/wfa-applications