Voltammetric Determination of Phenylalanine Using Chemically Modified Screen-Printed Based Sensors

Abstract

This paper describes the sensitive properties of screen-printed carbon electrodes (SPCE) modified by using three different electroactive chemical compounds: Meldola’s Blue, Cobalt Phthalocyanine and Prussian Blue, respectively. It was demonstrated that the Prussian Blue (PB) modified SPCE presented electrochemical signals with the highest performances in terms of electrochemical process kinetics and sensitivity in all the solutions analyzed. PB-SPCE was demonstrated to detect Phe through the influence it exerts on the redox processes of PB. The PB-SPCE calibration have shown a linearity range of 0.33–14.5 µM, a detection limit (LOD) of 1.23 × 10−8 M and the standard deviation relative to 3%. The PB-SPCE sensor was used to determine Phe by means of calibration and standard addition techniques on pure samples, on simple pharmaceutical samples or on multicomponent pharmaceutical samples. Direct determination of the concentration of 4 × 10−6–5 × 10−5 M Phe in KCl solution showed that the analytical recovery falls in the range of 99.75–100.28%, and relative standard deviations in the range of 2.28–3.02%. The sensors were successfully applied to determine the Phe in pharmaceuticals. The validation of the method was performed by using the FTIR, and by comparing the results obtained by PB-SPCE in the analysis of three pharmaceutical products of different concentrations with those indicated by the producer.

Determination of Diosmin in Pharmaceutical Products with Chemically Modified Voltammetric Sensors

“…The values of Γ which were obtained were in agreement with those reported in literature for voltammetric sensors, being 7.14 × 10 −10 mol•cm −2 for SPCE and 2.1 × 10 −9 mol•cm −2 for PB/SPCE [44,45]. It can be noticed that the obtained value for PB/SPCE was much higher, with an order of magnitude comparative with the value obtained for SPCE, which explains the higher sensitivity of PB/SPCE to the voltammetric detection of diosmin [46].…”

“…The obtained cyclic voltammograms are shown in Figure 5. for PB/SPCE [44,45]. It can be noticed that the obtained value for PB/SPCE was much higher, with an order of magnitude comparative with the value obtained for SPCE, which explains the higher sensitivity of PB/SPCE to the voltammetric detection of diosmin [46].…”

Development of a Novel Electrochemical Biosensor Based on Carbon Nanofibers–Cobalt Phthalocyanine–Laccase for the Detection of p-Coumaric Acid in Phytoproducts

“…It shows that the process occurring at the surface of the electrodes is controlled by the adsorption of the electroactive species, the adsorption of the hydroxycinnamic acid PCA on the active surface being the determining stage of the kinetics of the electrochemical process [63]. Taking into account the equation of the linear dependence between the cathodic peak current and the scan rate, the coverage degree of the electrode surface with the electroactive species (Γ) was calculated by means of the Laviron equation (1), and the results are shown in Table 2 [75].…”

Quantification of Tyrosine in Pharmaceuticals with the New Biosensor Based on Laccase-Modified Polypyrrole Polymeric Thin Film

“…Tyr has two isomers: L-Tyr and D-Tyr, synthesized in vivo from the essential AA L-Phe [ 12 ]. The WHO stresses a recommended daily intake of Tyr and Phe of 25 mg/kg body weight [ 13 ], showing that an increased level of Tyr can lead to fits of depression [ 14 ], Parkinson’s [ 15 ], and emotional disorders, and a low level to phenylketonuria (PKU) [ 16 , 17 ], albinism [ 18 ], and alkaptonuria [ 9 ]. Tyrosinemia is a hereditary, autosomal recessive disease that consists of the incorrect metabolism of Tyr, affecting the liver, kidneys, and peripheral nerves, and for this reason Tyr is measured in all newborn screening programs [ 19 ].…”