Potentiometric multisensory system based on perfluorosulfonic acid membranes and carbon nanotubes for sulfacetamide determination in pharmaceuticals

Potentiometric Sensor Arrays Based on Hybrid PFSA/CNTs Membranes for the Analysis of UV-Degraded Drugs

The degradation of drugs is a substantial problem since it affects the safety and effectiveness of pharmaceutical products, as well as their influence on the environment. A novel system of three potentiometric cross-sensitive sensors (using the Donnan potential (DP) as an analytical signal) and a reference electrode was developed for the analysis of UV-degraded sulfacetamide drugs. The membranes for DP-sensors were prepared by a casting procedure from a dispersion of perfluorosulfonic acid (PFSA) polymer, containing carbon nanotubes (CNTs), whose surface was preliminarily modified with carboxyl, sulfonic acid, or (3-aminopropyl)trimethoxysilanol groups. A correlation between the sorption and transport properties of the hybrid membranes and cross-sensitivity of the DP-sensor to sulfacetamide, its degradation product, and inorganic ions was revealed. The analysis of the UV-degraded sulfacetamide drugs using the multisensory system based on hybrid membranes with optimized properties did not require a pre-separation of the components. The limits of detection of sulfacetamide, sulfanilamide, and sodium were 1.8 × 10^-7, 5.8 × 10^-7, and 1.8 × 10^-7 M. The relative errors of the determination of the components of the UV-degraded sulfacetamide drugs were 2-3% (at 6-8% relative standard deviation). PFSA/CNT hybrid materials provided the stable work of the sensors for at least one year.

Perfluorosulfonic Acid Membranes Modified with Polyaniline and Hydrothermally Treated for Potentiometric Sensor Arrays for the Analysis of Combination Drugs

A novel potentiometric multisensory system for the analysis of sulfamethoxazole and trimethoprim combination drugs was developed. The potentiometric sensors (Donnan potential (DP) was used as an analytical signal) with an inner reference solution were based on perfluorosulfonic acid (PFSA) membranes modified with polyaniline (PANI) by in situ oxidative polymerization. The order of the membrane treatment with precursor solutions and their concentrations was varied. Additionally, the PFSA/PANI composite membranes were hydrothermally treated at 120 °C. The influence of the preparation conditions and the composition of membranes on their sorption and transport properties was studied. We estimated the factors affecting the sensitivity of DP-sensors based on the PFSA/PANI composite membranes to ions of sulfamethoxazole and trimethoprim simultaneously presented in solutions. A developed multisensory system provided a simultaneous determination of two analytes in aqueous solutions without preliminary separation, derivatization, or probe treatment. The re-estimation of the calibration characteristics of the multisensory system did not show a statistically significant difference after a year of its use. The limits of detection of sulfamethoxazole and trimethoprim were 1.4 × 10^-6 and 8.5 × 10^-8 M, while the relative errors of their determination in the combination drug were 4 and 5% (at 5 and 6% relative standard deviation), respectively.

Multisensory Systems Based on Perfluorosulfonic Acid Membranes Modified with Functionalized CNTs for Determination of Sulfamethoxazole and Trimethoprim in Pharmaceuticals

Sulfamethoxazole and trimethoprim are synthetic bacteriostatic drugs. A potentiometric multisensory system for the analysis of sulfamethoxazole and trimethoprim combination drugs was developed. Perfluorosulfonic acid membranes containing functionalized CNTs were used as the sensor materials. The CNTs' surface was modified by carboxyl, sulfonic acid, or (3-aminopropyl)trimethoxysilanol groups. The influence of the CNT concentration and the properties of their surface, as well as preliminary ultrasonic treatment of the polymer and CNT solution before the casting of hybrid membranes, on their ion-exchange capacity, water uptake, and transport properties was revealed. Cross-sensitivity of the sensors to the analytes was achieved due to ion exchange and hydrophobic interactions with hybrid membranes. An array of cross-sensitive sensors based on the membranes containing 1.0 wt% of CNTs with sulfonic acid or (3-aminopropyl)trimethoxysilanol groups enabled us to provide the simultaneous determination of sulfamethoxazole and trimethoprim in aqueous solutions with a concentration ranging from 1.0 × 10^-5 to 1.0 × 10^-3 M (pH 4.53-8.31). The detection limits of sulfamethoxazole and trimethoprim were 3.5 × 10^-7 and 1.3 × 10^-7 М. The relative errors of sulfamethoxazole and trimethoprim determination in the combination drug as compared with the content declared by the manufacturer were 4% (at 6% RSD) and 5% (at 7% RSD).

Multisensory Systems Based on Perfluorosulfonic Acid Membranes Modified with Polyaniline and PEDOT for Multicomponent Analysis of Sulfacetamide Pharmaceuticals

The degradation of sulfacetamide with the formation of sulfanilamide leads to a deterioration in the quality of pharmaceuticals. In this work, potentiometric sensors for the simultaneous determination of sulfanilamide, sulfacetamide and inorganic ions, and for assessing the degradation of pharmaceuticals were developed. A multisensory approach was used for this purpose. The sensor cross-sensitivity to related analytes was achieved using perfluorosulfonic acid membranes with poly(3,4-ethylenedioxythiophene) or polyaniline as dopants. The composite membranes were prepared by oxidative polymerization and characterized using FTIR and UV-Vis spectroscopy, and SEM. The influence of the preparation procedure and the dopant concentration on the membrane hydrophilicity, ion-exchange capacity, water uptake, and transport properties was investigated. The characteristics of the potentiometric sensors in aqueous solutions containing sulfanilamide, sulfacetamide and alkali metals ions in a wide pH range were established. The introduction of proton-acceptor groups and π-conjugated moieties into the perfluorosulfonic acid membranes increased the sensor sensitivity to organic analytes. The relative errors of sulfacetamide and sulfanilamide determination in the UV-degraded eye drops were 1.2 to 1.4 and 1.7 to 4%, respectively, at relative standard deviation of 6 to 9%.