Topcu, Cihan; Aydin, Senanur; Atasoy, Betul Hilal; Yilmaz, Rabia Rana; Coldur, Fatih; Caglar, Bulent

In this study, a novel all-solid-state electrochemical sensor based on favipiravir-tetraphenylborate (FAV-TPB) electroactive material was developed and reported for FAV's highly selective and sensitive potentiometric determination in COVID-19 antiviral drug formulations. All-solid-state FAV selective sensor was fabricated by mixing and properly pressing FAV-TPB, graphite (G), multi-walled carbon nanotube (MWCNT), and paraffin oil (PO). In order to obtain the best sensor response, the sensor component ratios were optimized. The most satisfying response characteristics was obtained with the sensor composition FAV-TPB:G:MWCNT:PO in the ratio 32.5:42.5:5:20 (w/w %). The developed sensor displayed a wide linear near-Nernstian response to FAV over the concentration of 1.0 × 10−6 − 1.0 × 10−1 molL−1 with a slope of 53.6 ± 1.4 mV (R2 = 0.9997). The detection limits of the sensor was calculated as 6.0 × 10−7 molL−1, respectively. The dynamic response time of the sensor was 7 s, and the sensor exhibited fairly reproducible potentiometric responses. In the pH range of 6.0–8.0, the sensor's potential response was not affected by the pH change of the test solutions. The improved sensor had a wide temperature tolerance, and its response remained unchanged in the 10–40 ℃ temperature range. The interference effect of some chemical and biological species was evaluated by the matched potential method and separate solution method. The sensor worked stable for 12 weeks without any considerable change in its potential response. The analytical applications of the sensor were successfully carried out with the potentiometric titration of FAV with sodium tetraphenylborate solution and also the direct determination of favipiravir in COVID-19 antiviral drug formulations.

Durdağı, Sevil Porikli

Lα, Lβ1 and Lγ emission line shapes and intensity ratio values have been measured for the elements Nd, Sm, Gd and Tb and for a large number of their compounds. The measurements were done using the EDXRF system, where special attention was given to minimizing the errors in various corrections such as self absorption and detector efficiency. All the lines were excited using a 100 mCi 241Am annular radioactive source. The energy shifts and Lα/Lβ1 and Lα/Lγ intensity ratio values of X-rays were examined for chemical effect. The measured Lα/Lβ1 and Lα/Lγ intensity ratios were compared with the experimental and theoretical data in literature.