CHEM ELECTIVE 1 (CHEM 71) ELECTROCHEMISTRY A simple method to detect the stimulant modafinil in authentic saliva using a carbon-nanotube screen-printed electrode with adsorptive stripping voltammetry by dos Santos, W.T.P. & Compton, R.G. (2019) In a recent publication in Sensors & Actuators, B: Chemical by Elsevier, Dos Santos, W.T.P., and Compton, R.G. (2019) presented a research article titled "A Simple Method to Detect the Stimulant Modafinil in Authentic Saliva Using a Carbon-Nanotube Screen-Printed Electrode with Adsorptive Stripping Voltammetry". Their study outlines an electrochemical approach to detect levels of modafinil in human saliva, utilizing a carbon-nanotube screen-printed electrode with adsorptive stripping squarewave voltammetry (SPE-CNT with AdSWV). The primary goal of this study is to provide a practical and efficient way to detect modafinil in human saliva.1 Modafinil is a drug usually prescribed for excessive daytime sleepiness and to limit sleep disturbances. However, due to its stimulant effects and addictive properties, it has been regulated in sports competitions and is subjected to anti-doping analysis.2 There have been existing analytical methods in the determination of modafinil such as HPLC, LC-MS, GC-MS, CE, HPTLC, and spectrophotometric methods.3 However, in this paper, a novel approach of using SPE-CNT combined with AdSWV in analyzing modafinil concentrations in undiluted saliva was tested. It has been demonstrated that electrochemical methods combined with SPEs are effective sensors for accelerating the transition from traditional benchtop methods and equipment to affordable, reliable, and fast sensing devices.4 Adsorptive stripping voltammetry is a versatile and powerful electroanalytical technique that has become widely used recently. It involves adsorption of electroactive species onto an electrode surface and a stripping step to release them. This approach is universal and can detect trace amounts of various analytes in different sample matrices.5 Furthermore, it also enhances the sensitivity of the electrochemical method and helps in reaching a lower limit of detection. 5,6 The research article's introduction is meticulously crafted and comprehensive, particularly in presenting the background of the analysis that will be employed and its associated benefits. The details presented are adequate to provide a thorough understanding of why and how the study is conducted. When preparing a research article, it is crucial to ensure that the title, abstract, and introduction are straightforward, precise, coherent, and devoid of any misleading information. It is imperative to adhere to these guidelines to effectively communicate the significance of the research and its potential impact on the respective field of study.7 On the contrary, the title, abstract, and introduction of the article seem to have some inconsistencies. While the title uses the term "Adsorptive Stripping Voltammetry", the abstract refers to it as "Adsorptive Stripping Wave Voltammetry". Later in the paper, "Adsorptive Squarewave Voltammetry" is used. This inconsistency could be confusing for readers who are not familiar with electrochemistry terminologies, especially for first-time readers. These may be small errors in a research article, but they can have a significant impact on its overall quality. The article's methodology is well-written in a way that it can be easily followed by first-time readers. Compared to other research articles such as the paper on adsorptive stripping voltammetry determination of methyldopa on the surface of a carboxylated multiwall carbon nanotubes modified glassy carbon electrode in biological and pharmaceutical samples,7 it is much more complex and structured considering that both used carbon nanotubes as their electrode and used AdSWV in determining a drug in biological samples. The use of diagrams, especially the well-made systematic diagram of Scheme 1 was very helpful in outlining the most important part of the analysis. It is good that it was explained step-by-step in the instrumental and apparatus section, but it is even better with the help of the diagram for visual learners. There is a study on how creating visual explanations improves learning, and in there, it is stated that creating visual explanations is likely to enhance students’ spatial thinking skills, skills that are increasingly needed in the contemporary and future world.9 Thus, including diagrams in the methodology section is an excellent choice to showcase the study in the best possible way. This section of the paper is a testament to the hard work of the researchers in answering the research problems addressed at the beginning of the study. In the results and discussion, all findings are presented and discussed with sufficient evidence showcased in the following voltammograms and schemes in the article. The authors utilized the space well, the labels for each diagram are concise and rich, and the text compliments the voltammograms presented. Studies showed that the modafinil oxidation process is adsorption-controlled at carbon electrodes and the AdSWV technique can be usually used to detect this analyte in undiluted human saliva. In comparison to the previously published approach that used gas chromatography with mass spectrometry detection for modafinil measurement in saliva, the current work offers advantages for modafinil determination in saliva, most notably ease of application and low cost for application in screening tests for doping control. Other research work was cited in the discussion and there are no discrepancies observed at all. The authors' conclusion does not recommend any further directions for future studies, and this is a testament to the study's comprehensiveness and thoroughness. In summary, the study's efforts to support the use of AdSWV in SPE-CNT modafinil determination are praiseworthy, and the scientific and sporting communities will greatly benefit from its conclusions, particularly concerning doping control. The study's procedures and conclusions are simply and effectively presented in this article. Moreover, the information gathered from the investigation offers solid backing for the conclusions drawn. Considering all of this, it is natural that the Journal of Sensors and Actuators, B: Chemical, would publish this research study because its purpose and topic are covered there. This is the first time that I encountered a study having graphite rods as the counter electrode used in voltammetry. Most of the other journals I have read used platinum wire due to its excellent electrocatalytic activity, high electrical conductivity, and mechanical robustness.10 However, as I proceeded to understand the study, graphite can also be a good counter electrode as it is priced lower than platinum, it offers good stability, high electrical conductivity, and is abundant. Despite the disparity in their features, each material has its advantages and limitations that are contingent on various factors. Therefore, to eliminate uncertainties and maximize the use of resources, the procedures and substances used in the study must be carefully examined. The activity, overall, provides an extensive understanding of the usage and application of Adsorptive Stripping Squarewave Voltammetry in the different aspects of our society. Learning the skill of research critique, or critical thinking in general, is crucial for future chemists to assess methods and findings and distinguish between small and large research errors fairly and appropriately. References (1) dos Santos, W. T. P.; Compton, R. G. A Simple Method to Detect the Stimulant Modafinil in Authentic Saliva Using a Carbon-Nanotube Screen-Printed Electrode with Adsorptive Stripping Voltammetry. Sensors & Actuators, B: Chemical 2019, 285 (285), 137–144. https://doi.org/10.1016/j.snb.2019.01.047. (2) Murillo-Rodríguez, E.; Barciela Veras, A.; Barbosa Rocha, N.; Budde, H.; Machado, S. An Overview of the Clinical Uses, Pharmacology, and Safety of Modafinil. ACS chemical neuroscience 2018, 9 (2), 151–158. https://doi.org/10.1021/acschemneuro.7b00374. (3) Ramachandra, B. A Critical Review of Properties of Modafinil and Analytical, Bioanalytical Methods for Its Determination. Critical Reviews in Analytical Chemistry 2016, 46 (6), 482–489. https://doi.org/10.1080/10408347.2016.1153948. (4) García-Miranda Ferrari, A.; Rowley-Neale, S. J.; Banks, C. E. Screen-Printed Electrodes: Transitioning the Laboratory In-To-the Field. Talanta Open 2021, 3, 100032. https://doi.org/10.1016/j.talo.2021.100032. (5) Wlazłowska, E.; Grabarczyk, M. Adsorptive Stripping Voltammetry for Determination of Vanadium: A Review. Materials 2023, 16 (10), 3646. https://doi.org/10.3390/ma16103646. (6) Wang, Y.; Selva, K.; Compton, R. G. Optimising Adsorptive Stripping Voltammetry: Strategies and Limitations. ChemElectroChem 2021, 8 (12), 2343–2352. https://doi.org/10.1002/celc.202100679. (7) Tullu, M. S. Writing the Title and Abstract for a Research Paper: Being Concise, Precise, and Meticulous Is the Key. Saudi Journal of Anaesthesia 2019, 13 (5), 12–17. https://doi.org/10.4103/sja.sja_685_18. (8) Rezaei, B.; Askarpour, N.; Ensafi, A. A. Adsorptive Stripping Voltammetry Determination of Methyldopa on the Surface of a Carboxylated Multiwall Carbon Nanotubes Modified Glassy Carbon Electrode in Biological and Pharmaceutical Samples. Colloids and surfaces. B, Biointerfaces 2013, 109, 253– 258. https://doi.org/10.1016/j.colsurfb.2013.04.004. (9) Bobek, E.; Tversky, B. Creating Visual Explanations Improves Learning. Cognitive Research: Principles and Implications 2016, 1 (1). https://doi.org/10.1186/s41235-016-0031-6. (10) Lee, J.; Bang, J. H. Reliable Counter Electrodes for the Hydrogen Evolution Reaction in Acidic Media. ACS Energy Letters 2020, 5 (8), 2706–2710. https://doi.org/10.1021/acsenergylett.0c01537.
