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Single Drop Electroanalysis and Interfacial Interactions: Sensitivity versus Limit of Detection †
Author(s) -
Walgama Charuksha,
Gallman Matthew,
Krishnan Sadagopan
Publication year - 2016
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.201600271
Subject(s) - analyte , detection limit , ascorbic acid , drop (telecommunication) , chemistry , biosensor , electrochemistry , carbon nanotube , analytical chemistry (journal) , electrode , chromatography , materials science , nanotechnology , food science , telecommunications , computer science , biochemistry
We report single drop electroanalytical measurements of pharmaceutically and biologically relevant compounds using screen printed electrodes (SPEs) modified with carboxylated multiwalled carbon nanotubes (MWCNT‐COOH) as the sensor surface. Acetaminophen, nicotine, ascorbic acid, and nicotinamide adenine dinucleotide reduced form (NADH) were detected in a single drop of solution. We show that combined polar and nonpolar interactions of analytes with ‐COOH functional groups and large surface area of MWCNT, respectively, allow highly sensitive analyte detection with wide dynamic range. Smaller analytes can bind to a significantly greater number of sensor sites than the bulkier analytes and offer better detection sensitivity. Results suggest that sensitivity is controlled by predominant nonpolar interactions that an analyte can undergo with the MWCNT‐COOH SPE sensor surface, whereas limit of detection is controlled by the extent of polar interactions between an analyte and the sensor surface, facilitating interfacial charge transport and an electrochemical signal output. Furthermore, a combination of polar and nonpolar analyte interactions with the sensor surface shows a synergistic effect on sensitivity and detection limit. This could be a likely reason for why sensitivity does not need to always correlate with lower detection limits as variations in the interfacial interactions are critical. Application of the designed single drop method to real samples was validated by estimating the amounts of acetaminophen, nicotine, ascorbic acid, and NADH in commercially available pharmaceuticals with excellent recovery.