Mathematical processing of RGB data in microfluidic paper-based analytical devices

Abstract Microfluidic paper-based analytical devices often are combined with scanners as detectors. In this work, different scanning options offered by scanners: resolution, scanning mode, exposure to radiation, colour restoration, and saving format were tested. Moreover, different attempts to mathematical data treatment based on intensities of three channels—Red, Green and Blue, were studied. All measurements presented in this article were conducted for a model dye—bromothymol blue and a model analyte—zinc(II) ion (complexed with xylenol orange in a paper matrix). The article summarizes the scanning options and possibilities of mathematical calculations. Nevertheless, it is suggested that the best option is to use the prior prepared calculation file to paste obtained intensities and compare all presented in this article (and the most frequently used) equations to process intensities and decide which one should be used in the particular analysis

Flow-through optoelectronic detectors for phosphate ions determination and their analytical applications

Oznaczanie jonów fosforanowych przeprowadzane jest rutynowo w wielu laboratoriach, a wyniki tych oznaczeń odgrywają istotną rolę w diagnostyce medycznej, analityce środowiska oraz analizie żywności. W rozprawie doktorskiej opisane zostały opracowane w trakcie badań detektory optoelektroniczne typu PEDD (ang. Paired Emitter Detector Diode) dedykowane do fotometrycznego oraz fluorymetrycznego oznaczania jonów fosforanowych. Detektory te zostały zaadaptowane do pracy w warunkach analizy przepływowej. Połączenie systemów przepływowych z detektorami optoelektronicznymi zapewnia nie tylko większą przepustowość, ale również znacząco zmniejsza wielkość układów pomiarowych, jednocześnie zwiększając ich mobilność. Dodatkowo w pracy przedstawiony został mikrofluidyczny system przygotowany w matrycy papierowej połączony z detektorem optoelektronicznym do oznaczania m.in. jonów fosforanowych. Nowatorskie podejście bazujące na koncepcji Lab-on-Paper pozwala znacząco zmniejszyć koszt analiz, zużycie reagentów, jak również ilość produkowanych odpadów. Wszystkie miniaturowe detektory optoelektroniczne przedstawione w tej pracy w połączeniu z różnymi systemami przepływowymi zostały zastosowane do analizy wielu próbek rzeczywistych: napojów typu cola, soków, płynu podializacyjnego, surowicy krwi, a także ekstraktów glebowych.Phosphate ions determination is routinely performed in many laboratories, and the results of these determinations play an important role in medical diagnostics, environmental analysis and food analysis. The dissertation describes, developed in the course of the research, PEDD (Paired-Emitter-Detector-Diode)-based optoelectronic detectors dedicated to photometric and fluorometric determination of phosphate ions. These detectors have been adapted for operation under flow analysis conditions. The combination of flow systems with optoelectronic detectors provides not only higher throughput, but also significantly reduces the size of measurement systems and this way increases their mobility. In addition, the work presents a microfluidic system prepared in a paper matrix combined with an optoelectronic detector for determination, among others, phosphate ions. An innovative approach based on the Lab-on-Paper concept allows to significantly reduce the cost of analyses, consumption of reagents as well as the amount of waste. All miniature optoelectronic detectors reported in this work combined with various flow systems were used for the analysis of many real samples: cola-type drinks, juices, postdialysis fluid, blood serum as well as soil extracts

Solid reference electrode integrated with paper-based microfluidics for potentiometric ion sensing

A new concept of a solid reference electrode integrated with microfluidic paper-based sampling was introduced and applied in potentiometric ion sensing. The new reference electrode consisted of an Ag/AgCl reference element (reusable) that is in contact with a disposable paper substrate (DPS) containing solid KCl. Thus, no KCl reference solution was applied during the analysis step, but the applied sample solution dissolved the solid KCl in the paper providing the electrolyte for the Ag/AgCl reference element. Such reference electrode was found to give a relatively constant potential after less than ca 1 min of equilibration. Moreover, the response of the reference electrode was not affected by concentrations of background electrolytes in the sample. Thus the proposed reference electrode was integrated with a paper-based microfluidic device and solid-contact ion-selective electrodes (ISEs) sensitive to K+, Na+ and Cl−. The optimized systems were characterized with near-Nernstian sensitivities (59.1 ± 1.5, 57.5 ± 0.5 and –56.4 ± 0.6 mV dec−1) and detection limits (10−4.1 ± 0.1, 10−3.3 ± 0.1 and 10−4.1 ± 0.1 mol dm−3) for K+, Na+ and Cl− ions, respectively. The paper-based measurement setup was favourably used for potentiometric determination of ions in environmental (wastewater sludge) and clinically relevant (sweat) samples