A Novel Carbon Nitride Nanosheets‐based Electrochemical Sensor for Determination of Hydroxychloroquine in Pharmaceutical Formulation and Synthetic Urine Samples

Abstract

This study introduces modified carbon paste electrodes with carbon nitride nanosheets (CNNS) and outlines their application for the determination of hydroxychloroquine sulfate (HCQ) in tablets and synthetic urine samples. CNNS were synthesized by hydrothermal route (200°C, 10 h) using melamine and citric acid as their precursors. The carbon nitride nanosheets-based electrode (CNNS/E) presented a linear dynamic range for HCQ (LDR), ranging from 10.0 nmol l À 1 to 6.92 μmol l À 1 , and detection (LOD) and quantification limits (LOQ) of 0.16 nmol l À 1 and 0.52 nmol l À 1 , respectively. LOD and LOQ were calculated by the equations: LOD = 3(S d /b), and LOQ = 10(S d /b). The modified sensor presented excellent relative standard deviations for parameters such as repeatability (2.39 % and 1.87 %) and reproducibility (3.22 % and 2.32 %) in HCQ oxidation peaks (1 and 2). The CNNS/E has not shown significant variations in its anodic signal intensity in the presence of some organic and inorganic substances. It is worth bearing in mind that CNNS/E can be easily manufactured and the sensor has the lowest HCQ detection limits reported so far. The proposed sensor was successfully applied for HCQ determination in tablets and synthetic urine, showing good recovery values and an error of 0.60 % about comparative method in tablet samples, assuring the quality of the method.

Development of a selective graphene quantum dots based electrochemical sensor for the determination of estrone in different water matrices and synthetic urine

“…The electronic absorption spectrum in the UV-Vis region (Figure 1b) of the GQD shows a maximum absorption region at 223 nm, attributed to electronic transitions of the π-π* orbitals of the C=C bond formed during the carbonization of citric acid. The band observed at 346 nm is related to the n-π* transitions of the C=O bond present (surface group) [14,21,22]. Thus, the results obtained corroborate those observed through the FTIR spectrum.…”

“…This implies that the nanomaterial did not exhibit an excitation‐dependent emission pattern. In addition, this effect is mainly related to the homogeneity of the size of the nanostructures [14, 21]. The TEM image (Figure 1d) indicates the presence of overlapping layers of graphene fragments, in which the transparency recorded in some regions of the material originates from the superposition of small layers of the material, and spots with high color intensity indicate an overlap of the fragments [12, 14, 23].…”

“…The preparation of the synthetic urine sample followed the method presented in the literature [21]. We dissolved 0.06 g of CaCl 2 .2H 2 O, 0.08 g of KCl, 0.07 g of KH 2 PO 4 , 0.15 g of NaCl, 0.11 g of Na 2 SO 4 , 0.05 of NH 4 Cl and 1.25 g of urea (CH 4 N 2 O) in ultrapure water.…”

“…In the spectrum of the GQD, the stretching vibration at 3450 cm À 1 is related to the OÀ H bond. The stretching vibrations at 1730 and 1228 cm À 1 correspond to the C=O and C=C bonds, respectively, indicating the presence of carbonyl groups and the formation of aromatic structures during carbonization [20,21]. The electronic absorption spectrum in the UV-Vis region (Figure 1b) of the GQD shows a maximum absorption region at 223 nm, attributed to electronic transitions of the π-π* orbitals of the C=C bond formed during the carbonization of citric acid.…”

Reduced Graphene Oxide‐based Sensor for 17α‐Ehinylestradiol Voltammetric Determination in Wastewater, Tablets and Synthetic Urine Samples

“…The determination of this compound in biological, pharmaceutical and environmental samples can be performed by several analytical techniques, such as electrophoresis [9], immunoassay [10], liquid and gas chromatography [11, 12]. However, these analyses demand exhaustive procedures, difficulties in carrying out in situ measurements, expensive reagents and equipment, the need for qualified operators, and the requirement for several samples, which are prepared through steps such as extraction, cleaning and pre‐concentration [11, 12].…”