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.
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.
In this study, how prospective chemistry teachers (PCTs) perceive precipitation and conceptualize precipitation reactions at the symbolic level was explored. Further, it was of interest to identify PCTs’ visualization of the sub-microscopic level of precipitation reactions. The sample was drawn from the Chemistry Education Department at the Education Faculty of a Turkish Public University. A total of 46 PCTs (10 in the 4th semester, 15 in the 6th semester, and 21 in the 8th semester) participated in the study. The data were collected using an instrument with three open-ended questions developed by the authors and with interviews. It was revealed that the PCTs thought about precipitation in qualitatively different ways depending on their practices of phenomena. The PCTs’ perceptions of precipitation were grouped into three issues coded as (1) reacting two salt solutions, (2) undissolved solid and (3) residue. It was found that half of the PCTs (24 of the 46 PCTs) did not use state symbols when writing the precipitation equations and more than half of them included the molecular dissolution features in their drawings. It was suggested that instruction should be to address incorporating a relation between the sub-microscopic, symbolic and macroscopic levels by using the animations.
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