Graphite Based Microsensors Developed for the Electrochemical Determination of L‐Tyrosine from Pharmaceutical Samples

Two electrochemical sensors were proposed for the determination of L‐tyrosine from pharmaceutical capsules. The electrochemical sensors were based on plain graphite paste and chitosan modified graphite paste. Working conditions, e. g. pH, supporting electrolytes have been optimized. The results revealed for both electrodes very low limits of quantification (LOQ) (0.18 mg L−1 and 0.0018 mg L−1) for plain graphite paste based sensors and for chitosan modified paste sensors respectively. A higher sensitivity of 7.95×10−10 A mg L−1 was obtained for the sensor based on plain graphite paste (G). The uniformity content test showed that L‐Tyrosine can be recovered in pharmaceutical capsules with an average value higher than 98.00 % and a relative standard deviation (RSD%) value less than 1.00 % (N=5).