Calibrant-Free Analyte Quantitation via a Variable Velocity Flow Cell

Abstract

In this paper, we describe a novel method for analyte quantitation that does not rely on calibrants, internal standards, or calibration curves but, rather, leverages the relationship between disparate and predictable surface-directed analyte flux to an array of sensing addresses and a measured resultant signal. To reduce this concept to practice, we fabricated two flow cells such that the mean linear fluid velocity, U, was varied systematically over an array of electrodes positioned along the flow axis. This resulted in a predictable variation of the address-directed flux of a redox analyte, ferrocenedimethanol (FDM). The resultant limiting currents measured at a series of these electrodes, and accurately described by a convective-diffusive transport model, provided a means to calculate an “unknown” concentration without the use of calibrants, internal standards, or a calibration curve. Furthermore, the experiment and concentration calculation only takes minutes to perform. Deviation in calculated FDM concentrations from true values was minimized to less than 0.5% when empirically derived values of U were employed.

A Laser-Activated Membrane Introduction Mass Spectrometry Study of Proton Spillover Promoted Alkane Dehydrogenation

“…The term “operando” was introduced by Weckhuysen , as a form of in situ spectroscopy . Broadly applicable detection systems providing the high-speed dynamics needed for operando screening include electrochemical, − optical, and mass spectrometric methods. − …”

Adaptable Detection Strategies in Membrane-Based Immunoassays: Calibration-Free Quantitation with Surface-Enhanced Raman Scattering Readout

“…We recently reported on the development and concept assessment of a calibration-free electrochemical detection method that exploits the predictable fluxes of an analyte under steady-state hydrodynamics as a means for analyte quantitation. 26 In that work, the exact concentration of an analyte was determined using a variable width flow cell to control sample fluid velocities above an array of gold electrodes. In looking to devise concepts aimed at PON heterogeneous immunoassays, we have begun to explore a strategy in which the assay substrate (i.e., membrane) may be rationally designed so that the analyte concentration is determined from known and measurable variables.…”

“…As an extension of our past work on heterogeneous immunoassays − and colorimetric solid-phase extrac­tion, , we and other researchers − have been investigating calibration-free approaches to quantitation in biological assays. We recently reported on the development and concept assessment of a calibration-free electrochemical detection method that exploits the predictable fluxes of an analyte under steady-state hydrodynamics as a means for analyte quantitation . In that work, the exact concentration of an analyte was determined using a variable width flow cell to control sample fluid velocities above an array of gold electrodes.…”