Autocalibration technique based on SIA and integrated multisensor chip

An analytical system based on a multisensor ISFET array monolithically integrated in one chip, sequential injection analysis (SIA) and Partial Least Squares (PLS) method for data processing is presented. Along with these the system carried a custom made flow cell with inner volume of 10 μl for the sensor array and a 400 μl of mixing cell for automatic preparation of liquid samples. The system was tested analyzing mineral water samples with very similar ion contents (sodium, potassium, chloride). SIA technique was applied for automatic preparation of calibration solutions by mixing four stock solutions. Ion concentrations of calibration solutions were calculated using the PLS model. Results obtained on each step of the measuring cycle were used as a feedback to update the model and recalculate ion concentrations. The precision of the developed system was typical for potentiometric method with standard deviation of determined ion concentrations of about 3–5%. Proposed approach may be applied for automatic analysis of complex samples that require a large number of multicomponent calibration solutions.