The ongoing coronavirus disease 2019 (COVID-19) pandemic continues to threaten public health systems all around the world. In controlling the viral outbreak, early diagnosis of COVID-19 is pivotal. This article describes a novel method of voltammetrically determining severe acute respiratory syndrome coronavirus 2019 (SARS-CoV-2) with a newly designed sensor involving bovine serum albumin, SARS-CoV-2 spike antibody and a functionalised graphene oxide modified glassy carbon electrode (BSA/AB/ f -GO/GCE) or screen-printed electrode (BSA/AB/ f -GO/SPE). The oxidation reaction based on the antibody–antigen interaction was evaluated as a response to SARS-CoV-2 spike antigen at -200 mV and 1430 mV with the BSA/AB/ f -GO/SPE and BSA/AB/ f -GO/GCE, respectively. The developed sensors, BSA/AB/ f -GO/SPE and BSA/AB/ f -GO/GCE, could detect 1 ag/mL of virus spike protein in synthetic, saliva and oropharyngeal swab samples in 5 min and 35 min, and both sensors demonstrated a dynamic response to the SARS-CoV-2 spike antigen between 1 ag/mL and 10 fg/mL. Real-time polymerase chain reaction (RT-PCR), rapid antigen test and the proposed method were applied to saliva samples. When compared to RT-PCR, it was observed that the developed method had a 92.5% specificity and 93.3% sensitivity. Moreover, BSA/AB/ f -GO/SPE sensor achieved 91.7% accuracy compared to 66.7% accuracy of rapid antigen test kit in positive samples. In view of these findings, the developed sensor provides great potential for the diagnosing of COVID-19 in real samples.

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This paper presents a simple, rapid, and accurate voltammetric method for determination of boron in water and steel samples using a disposable pencil graphite electrode. The oxidation of Tiron in the boron-Tiron complex in phosphate buffer at pH 7.5 was measured as a response. Type and concentration of supporting electrolyte, pH, ionic strength, Tiron concentration, scan rate, step amplitude, pulse amplitude, and pencil grade were investigated as the parameters affecting the peak current. The limit of detection (3s) was estimated as 84 µ g/L. The relative standard deviation of the method was 4.6 for 1 mg B/L (N = 7). The recovery results varied between 90% and 103% for water samples and between 94% and 108% for steel samples. The results were compared with those obtained from the ICP-OES method and no statistically significant difference between the methods was found.

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