Surface Modified Thread-Based Microfluidic Analytical Device for Selective Potassium Analysis

Abstract

This paper presents a thread-based microfluidic device (μTAD) that includes ionophore extraction chemistry for the optical recognition of potassium. The device is 1.5 cm × 1.0 cm and includes a cotton thread to transport the aqueous sample via capillary wicking to a 5 mm-long detection area, where the recognition chemistry is deposited that reaches equilibrium in 60 s, changing its color between blue and magenta. A complete characterization of the cotton thread used as well as the sensing element has been carried out. The imaging of the μTAD with a digital camera and the extraction of the H coordinate of the HSV color space used as the analytical parameter make it possible to determine K(I) between 2.4 × 10(-5) and 0.95 M with a precision better than 1.3%.

Thread based microfluidic platform for urinary creatinine analysis

“…When using this recognition chemistry in single-use devices or disposable sensors, working with normalized signals is a cumbersome or even impossible task, because they require the acquisition of different measurements with the same device. To solve this problem, we propose using the chromatic coordinate H from the hue-oriented HSV colour space as the analytical parameter, [6] carrying out the analyte measurements with no need to activate the membrane or normalize the signal. [29,30] To use the tonal coordinate H as the analytical parameter, a tone change must occur due to deprotonate the indicator, not a simple change of intensity.…”

“…To reduce the response time, different strategies have been devised, typically based on increasing the contact surface and reducing the molecular diffusion distance. [6] One interesting option to achieve a short response time as well as an efficient interaction is the inclusion of ionophore-based chemistry in a microfluidic analytical device, which miniaturizes the laboratory process aimed at detecting a specific target by converting a recognition event into a detectable quantitative signal. Some examples have appeared in the literature about the use of microfluidic platforms combined with ionophore-based optical sensors: a) a centrifugal platform for K + determination; [7,8] b) a pressure-driven platform for alkaline ions, [9] Cd 2+ , or Hg 2+ ; [10] c) a segmented flow microfluidic platform for K + , Na + , Cland protamine; [11] and d) a capillary microfluidic platform for K + .…”

“…Some examples have appeared in the literature about the use of microfluidic platforms combined with ionophore-based optical sensors: a) a centrifugal platform for K + determination; [7,8] b) a pressure-driven platform for alkaline ions, [9] Cd 2+ , or Hg 2+ ; [10] c) a segmented flow microfluidic platform for K + , Na + , Cland protamine; [11] and d) a capillary microfluidic platform for K + . [6,12] However, not all microfluidic platforms based on ionophore extraction recognition are suitable for reducing the response time. The droplet microfluidicsbased sensing scheme reduces the reaction time from 10 min to about 1 s. [11] Other examples include the pressure-driven laminar flow platform for alkaline ions with 8 s response time [9] and the thread-based capillary platform for K + , with requires 15 s instead of the usual 5 min in membrane format.…”

“…The droplet microfluidicsbased sensing scheme reduces the reaction time from 10 min to about 1 s. [11] Other examples include the pressure-driven laminar flow platform for alkaline ions with 8 s response time [9] and the thread-based capillary platform for K + , with requires 15 s instead of the usual 5 min in membrane format. [6] This paper describes the use of an ionophore for creatinine in a microfluidic analytical device. The ionophore is an aryl-substituted monophosphonatebridged calix [4]pyrrole (CalixPyr), previously reported by some of us, [3] and applied in an ion-selective potentiometric sensor, [13] as well as in an optical disposable sensor to monitor creatinine levels in urine.…”

“…The recognition strategy used is combined with colour measurement with a consumer electronics imaging device, such as a digital camera or a smartphone, which makes it possible to use chromatic coordinates as an analytical parameter and avoids the need to work with normalized signals, which considerably simplifies the use of the device. [6] On the other hand, the lack of experimental information with respect to the binding mechanism of these compounds (ionophore• • • creatininium ion) requires the use of computational chemistry tools to provide further insight into the structure and formation of different complexes on both sides of the ionophore, as well as the role of the interference with other analytes such as urea, uric acid and simple cations (Na + , K + , NH + 4 ) (see Figure 1). The formation of trimers at the two binding sites of the ionophore merits special attention, as it provides the most basic information about the binding mechanism.…”