Cobalt tetrasulphonated phthalocyanine immobilized on poly-L-lysine film onto glassy carbon electrode as amperometric sensor for cysteine.
The present work describes the development of a simple and efficient method for the amperometric determination of cysteine (CySH) in wild medium at an applied potential of 0.150 V versus Ag/AgCl. In this sense, the electrocatalytic oxidation of cysteine (CySH) was carried out on a glassy carbon electrode modified with cobalt tetrasulphonated phthalocyanine (CoTSPc) and poly-L-lysine (PLL) film. The immobilization of CoTSPc in PLL film was performed by a simple evaporation of the solvent. The CoTSPc/PLL film, formed on the GC electrode showed an electrocatalytic activity to the CySH oxidation. The sensor presented its best performance in 0.1 mol l(-1) Pipes at pH 7.5. Under optimized operational conditions, the sensor provided a wide linear response range for CySH from 0.50 up to 216.0 micromol l(-1) with a sensitivity and detection limit of 157 nA cm(-2) l micromol(-1) and 150 nmol l(-1), respectively. The proposed sensor presented higher sensitivity when compared to the other modified electrodes described in the literature and showed a stable response for at least 200 successive determinations. The repeatability of the measurements with the same sensor and different sensors, evaluated in term of relative standard deviation, were 4.1 and 5.2%, respectively, for n=10. The developed sensor was applied for the CySH determination in food supplement samples and the results were statistically the same to those obtained by a comparative method described in the literature at a confidence level of 95%.
Luz
Rita de Cássia Silva
Rde C
Institute of Chemistry, UNICAMP, P.O. Box 6154, 13084-971 Campinas, SP, Brazil.
Moreira
Adriano Benedito
AB
Damos
Flavio Santos
FS
Tanaka
Auro Atsushi
AA
Kubota
Lauro Tatsuo
LT
D002244:Carbon; D003545:Cysteine / Q000032:analysis*; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D007211:Indoles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011107:Polylysine / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D007211:Indoles; D009942:Organometallic Compounds; D011107:Polylysine; C052738:cobalt tetrasulfophthalocyanine; D002244:Carbon; D003545:Cysteine