Introduction

This pH meter, based on colorimetric measures, surpasses the current limits of the use of Colorimetric sensor arrays (CSA) for the measurement of pH values. Thanks to a special preparation of the matrix and specific settings in the optical sensor, the analytic performance is comparable to instruments based on potentiometric measurements with a glass electrode.

Technical features

The patent describes a device formed by a matrix of colorimetric sensors for the measurement of pH. Measures are based on the Hue (H) coordinate in the colour space HSV from the acquisition of images with a CCD camera. The position of sigmoidal H profiles (pH) can change by varying the concentration of a cationic surfactant: this allows an extension of the range within which a single indicator is stable, therefore creating a measuring system comparable to glass electrode meters:

• Even precision of the entire measurement range (pH 1.0-12.0);
• Error inferior to 02 pH units;
• Response time around 10-20 seconds.

The instrument is reversible and can operate within a 10-30°C range. It is especially useful for in-line measurements (including turbid samples) since it does not require continuous calibration.

Possible Applications

• pH measurement;
• pH measurement in salt water;
• pH measurement of sewage;
• in-line pH measurement;
• pH measurement of soil;
• pH measurement;
• clinical pH measurement.

Advantages

• Requires only one initial calibration;
• Ideal for in-line measures;
• Precise measurement of saline water;
• No leaching;
• No acidic or alkaline error;
• Fast and simple measurement;
• Low cost.