Nanoparticles based solid contact potentiometric sensor for the determination of theophylline in different types of tea extract

Carbon nanomaterials as electrochemical sensors for theophylline: a review

Theophylline (TP) is a methylxanthine derivative, which serves as a valuable compound in treating respiratory disorders and acts as a bronchodilator agent. However, TP has a limited therapeutic range (20-100 μmol L-1), demanding precise monitoring to prevent potential drug toxicity even with slight level fluctuations during treatment. Thus, to overcome this limitation, electrochemical methods have been extensively used due to their efficacy in achieving sensitivity, selectivity, and accuracy. In the context of electrochemical sensors, nanocarbon-based materials have gained widespread recognition for their extensive applications. Therefore, this review aims to explore the latest advancements in carbon-based electrodes particularly used for the precise determination of TP through electrochemical methods. The results are expected to provide insights into the profound significance of the methods in enhancing the accuracy and sensitivity for the detection of TP.

Utilization of a TiO2-CuO Bimetallic/Polyaniline Nanocomposite as a Transducer in a Solid Contact Potentiometric Sensor for the Determination of Vildagliptin

Current fundamental electrochemical research shows the potential of utilizing polymeric nanostructured materials as ion-to-electron transducers. In this paper, aniline was polymerized in the presence of TiO2 and CuO nanoparticles to yield a bimetallic/PANI nanocomposite. It was applied as a transducer in a carbon paste electrode for the potentiometric determination of vildagliptin in the presence of 18-crown-6-ether as a recognition element. The electrode's potentiometric performance was studied according to the IUPAC guidelines. It exhibited a wide linearity range of 1 × 10-2 M to 1 × 10-8 M, remarkable sensitivity (LOD of 4.5 × 10-9 M), and a fast response time of 10 s ± 1.3. The sensor did not show any potential drift due to the absence of the water layer between the carbon paste and the metallic conductor. This endowed the sensor with high stability and a long lifetime, as 137 days passed without the need to change the carbon paste surface. The electrode was utilized for the determination of the concentration of vildagliptin in bulk, pharmaceutical tablets, and human plasma, with average recovery ranging from 97.65% to 100.03%.

Determination of 4 psychoactive substances in tea using ultra high performance liquid chromatography combined with the quadrupole time-of-flight mass spectrometry

In this study, a method for the qualification and quantification of 4 psychoactive substances in tea using ultra high performance liquid chromatography coupled with the quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) has been developed. Tea samples were extracted by a 50% (v/v) methanol-water solution, and then separated by an ACQUITY UPLC BEH Shield RP18 column using a binary solvent system by gradient elution. The analytes were determined by Q-TOF/MS in TOFMS and information-dependent acquisition (IDA)-MS/MS mode. The results showed that the mass accuracy error of the 4 psychoactive substances were lower than 5.0 × 10-6, and a good linear relationship was observed in the range of 0.5-500 μg L-1 and correlation coefficient was higher than 0.9990. The LOD was in the range of 0.005-0.020 mg kg-1 and the LOQ was in the range of 0.010-0.040 mg kg-1. The recovery of the method was in range of 80.14-93.25% with spike levels of 0.010-0.400 mg kg-1, and relative standard deviations were lower than 10%. The method was simple, specific and reliable. It has been successfully used for the detection of 4 psychoactive substances in tea samples.