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Miniaturized magnetic-based pipette tip microextraction is presented as a sample preparation approach for microsamples. It involves quick dispersion of a diminutive amount of a magnetic sorbent material in a low-volume sample (10 μL) to entrap the target analytes. Next, the dispersion is aspirated using a (semi)automatic pipette through a pipette tip with a small cubic neodymium magnet inside, which retrieves the magnetic sorbent containing the analytes. After discarding the rest of the sample, the sorbent is properly rinsed by aspirating/dispensing deionized water, and then, the analytes are eluted by aspirating/dispensing an appropriate solvent. This approach was employed for the determination of free cortisol in serum and urine from very low birth weight preterm newborns, a vulnerable patient group who present low availability for sampling biological fluids. A magnetic immunosorbent made of a cortisol antibody was employed for the selective extraction, followed by liquid chromatography-tandem mass spectrometry. Good analytical features were obtained, such as limits of detection and quantification of 0.08 and 0.27 ng mL−1, respectively, linearity up to 50 ng mL−1 (R2 > 0.999), RSD values under 15% and relative recoveries between 91 and 111%. The cross-reactivity with other glucocorticoids (i.e., cortisone and prednisolone) was evaluated to show the selectivity of the extraction. Finally, the method applicability was demonstrated towards the determination of free cortisol in the serum and urine samples from low birth weight preterm newborns. [ABSTRACT FROM AUTHOR]

A novel on-chip electrochemical magneto-immunoassay for the determination of procalcitonin (PCT) has been proposed. The strategy involved the on-line performing of the biorecognition event and detection on the thin-film microfluidic gold electrode chamber operating at E = −0.20 V (vs. Au). The complete assay was performed in less than 15 minutes using only 25 μL of the sample, covering the entire range of clinically relevant PCT concentrations in sepsis diagnosis with a limit of detection and quantification of 0.02 ng mL−1 and 0.05 ng mL−1, respectively (the sepsis diagnosis threshold: 0.5 ng mL−1). The on-chip electrochemical magneto-immunoassay provided excellent results in the analysis of very unique samples obtained from preterm neonates admitted with suspected sepsis, in which the sample volume is hardly available. These characteristics fulfill the POCT requirements for PCT determination in the whole clinically relevant concentration range. Because of the high clinical relevance and the important role of PCT in sepsis, this approach opens new perspectives for sepsis diagnosis and therapy guidance using low volume samples. [ABSTRACT FROM AUTHOR]

This work describes for the first time the coupling of microfluidic chips (MC) to electrosynthetized silver metallic oxide clusters (AgMOCs). As an early demonstration of this novel approach, the ultrafast detection of galactose in galactosemic newborns’ urine samples is proposed. AgMOCs were in situ electrosynthetized on integrated microchip platinum electrodes using a double pulse technique and characterized in full using scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques revealing the presence of silver oxides and electrocatalysis towards galactose as a galactosemia biomarker. Galactose detection in galactosemic newborns’ urine samples proceeded in less than 30 s, differentiating between ill and healthy urine samples and requiring negligible urine sample consumption. The significance of the newborns’ urine samples confirmed the analytical potency of the MC-AgMOCs approach for future implementation of screening for rare disease diagnosis such as galactosemia. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotube press-transferred electrodes (SWPTEs) are new disposable electrodes where carbon nanotubes act as exclusive electrochemical transducers, being an excellent alternative to common approaches in the field. In the current work, these pioneering SWPTEs coupled to microfluidic chips (MCs) have been employed to develop their first real application. A class-selective electrochemical isoflavone index determination has been proposed for fast and reliable qualitative and quantitative assessment of class-isoflavones based on the co-migration of the total glycosides (TG) and total aglycones (TA) in less than 250 s with very good intra-SWPTE repeatability (RSDs ≤ 8%, n = 5) and inter-SWPTE reproducibility (RSDs ≤ 9%, n = 3). These novel SWPTEs are entering with important roles into the micro and nanotechnology scenes expanding new frontiers in the food analysis and health field. [ABSTRACT FROM AUTHOR]

Microfluidic technology has now become a novel sensing platform where different analytical steps, biological recognition materials and suitable transducers can be cleverly integrated yielding a new sensor generation. A novel “lab-on-a-chip” strategy integrating an electrokinetic magnetic bead-based electrochemical immunoassay on a microfluidic chip for reliable control of permitted levels of zearalenone in infant foods is proposed. The strategy implies the creative use of the simple channel layout of the double-T microchip to perform sequentially the immunointeraction and enzymatic reaction by applying a program of electric fields suitably connected to the reservoirs for driving the fluidics at different chambers in order to perform the different reactions. Both zones are used with the aid of a magnetic field to avoid in a very simple and elegant way the non-specific adsorption. Immunological reaction is performed under a competitive enzyme-linked immunosorbent assay (ELISA) where the mycotoxin ZEA and an enzyme-labelled derivative compete for the binding sites of the specific monoclonal antibody immobilised onto protein G modified magnetic beads. Horseradish peroxidase (HRP), in the presence of hydrogen peroxide, catalyses the oxidation of hydroquinone (HQ) to benzoquinone (BQN), whose back electrochemical reduction was detected at +0.1 V. Controlled-electrokinetic fluidic handling optimized conditions are addressed for all analytical steps cited above, and allows performing the complete immunoassay for the target ZEA analyte in less than 15 minutes with unique analytical merits: competitive immunoassay currents showed a very well-defined concentration dependence with a good precision as well as a suitable limit of detection of 0.4 µg L−1, well below the legislative requirements, and an extremely low systematic error of 2% from the analysis of a maize certified reference material revealing additionally an excellent accuracy. Also, the reliability of the approach is demonstrated by the analysis of selected infant foods yielding the strictest ZEA permitted levels and excellent recoveries of 103 and 101% for solid and liquid samples, respectively. [ABSTRACT FROM AUTHOR]

A novel analytical strategy that couples enzyme-linked immunosorbent assay (ELISA) and electrochemical microfluidic chips to determine the mycotoxin zearalenone (ZEA) in baby foods is presented. The analytical cycles for an ultra-fast analysis of the sample and its sequential fast and simplified calibration were performed in about 200 s plus to ELISA protocol. This route avoided the typical four-parameter logistic curve fit which is a highly time-consuming and laborious procedure. An extremely low concentration level of ZEA (less than 1 ppb) was detected with reliability. This level is 20 times lower than the strictest tolerable limit (20 ppb) for baby foods, making the microfluidic approach the newly anticipated analytical security tool for the future. The reliability of the proposal was demonstrated by accuracy evaluations using a certified reference material and by demonstrating its suitability during the control of the regulatory limits of ZEA in baby foods. In addition, the microfluidic approach allowed sensitivity and the incubation enzymatic reaction to be manipulated in situ. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) possess preferential ‘electrocatalytic’ properties that affect the oxidation of enediol groups, establishing a relationship between electrocatalysis and chemical structure. Since this chemical structure occurs in analytes involved in high impact areas such as the pharmaceutical, cosmetic, and food safety industries, this preferential electrochemical behaviour was demonstrated using both standard and selected real-world samples. The oxygen-containing species present on the surface of CNTs and generated during acid treatment were responsible for an enhanced electron transfer reaction for these structures using a proton-assisted electron transfer mechanism, thus confirming their crucial role during the surface preparation process of electrocatalysis. The analytical benefits were that the inherent selectivity and sensitivity from these nanomaterials could be exploited for the direct detection of analytes in complex matrices, revealing their crucial role in the simplification of analytical processes. [ABSTRACT FROM AUTHOR]

A novel strategy integrating methodological calibration and analysis on board on a planar first-generation microfluidics system for the determination of total isoflavones in soy samples is proposed. The analytical strategy is conceptually proposed and successfully demonstrated on the basis of (i) the microchip design (with the possibility to use both reservoirs), (ii) the analytical characteristics of the developed method (statically zero intercept and excellent robustness between calibration slopes, RSDs < 5%), (iii) the irreversible electrochemical behaviour of isoflavone oxidation (no significant electrode fouling effect was observed between calibration and analysis runs) and (iv) the inherent versatility of the electrochemical end-channel configurations (possibility of use different pumping and detection media).Repeatability obtained in both standard (calibration) and real soy samples (analysis) with values of RSD less than 1% for the migration times indicated the stability of electroosmotic flow (EOF) during both integrated operations. The accuracy (an error of less than 6%) is demonstrated for the first time in these microsystems using a documented secondary standard from the Drug Master File (SW/1211/03) as reference material. Ultra fast calibration and analysis of total isoflavones in soy samples was integrated successfully employing 60 s each; enhancing notably the analytical performance of these microdevices with an important decrease in overall analysis times (less than 120 s) and with an increase in accuracy by a factor of 3. [ABSTRACT FROM AUTHOR]

Correction for ‘Microchip in situ electrosynthesis of silver metallic oxide clusters for ultra-FAST detection of galactose in galactosemic newborns’ urine samples by Laura García-Carmona et al., Analyst, 2016, 141, 6002–6007. [ABSTRACT FROM AUTHOR]

Microfluidic technology has now become a novel sensing platform where different analytical steps, biological recognition materials and suitable transducers can be cleverly integrated yielding a new sensor generation. A novel "lab-on-a-chip" strategy integrating an electrokinetic magnetic bead-based electrochemical immunoassay on a microfluidic chip for reliable control of permitted levels of zearalenone in infant foods is proposed. The strategy implies the creative use of the simple channel layout of the double-T microchip to perform sequentially the immunointeraction and enzymatic reaction by applying a program of electric fields suitably connected to the reservoirs for driving the fluidics at different chambers in order to perform the different reactions. Both zones are used with the aid of a magnetic field to avoid in a very simple and elegant way the non-specific adsorption. Immunological reaction is performed under a competitive enzyme-linked immunosorbent assay (ELISA) where the mycotoxin ZEA and an enzyme-labelled derivative compete for the binding sites of the specific monoclonal antibody immobilised onto protein G modified magnetic beads. Horseradish peroxidase (HRP), in the presence of hydrogen peroxide, catalyses the oxidation of hydroquinone (HQ) to benzoquinone (BQN), whose back electrochemical reduction was detected at +0.1 V. Controlled-electrokinetic fluidic handling optimized conditions are addressed for all analytical steps cited above, and allows performing the complete immunoassay for the target ZEA analyte in less than 15 minutes with unique analytical merits: competitive immunoassay currents showed a very well-defined concentration dependence with a good precision as well as a suitable limit of detection of 0.4 µg L(-1), well below the legislative requirements, and an extremely low systematic error of 2% from the analysis of a maize certified reference material revealing additionally an excellent accuracy. Also, the reliability of the approach is demonstrated by the analysis of selected infant foods yielding the strictest ZEA permitted levels and excellent recoveries of 103 and 101% for solid and liquid samples, respectively.

Carbon nanotubes (CNTs) possess preferential 'electrocatalytic' properties that affect the oxidation of enediol groups, establishing a relationship between electrocatalysis and chemical structure. Since this chemical structure occurs in analytes involved in high impact areas such as the pharmaceutical, cosmetic, and food safety industries, this preferential electrochemical behaviour was demonstrated using both standard and selected real-world samples. The oxygen-containing species present on the surface of CNTs and generated during acid treatment were responsible for an enhanced electron transfer reaction for these structures using a proton-assisted electron transfer mechanism, thus confirming their crucial role during the surface preparation process of electrocatalysis. The analytical benefits were that the inherent selectivity and sensitivity from these nanomaterials could be exploited for the direct detection of analytes in complex matrices, revealing their crucial role in the simplification of analytical processes.

A novel strategy integrating methodological calibration and analysis on board on a planar first-generation microfluidics system for the determination of total isoflavones in soy samples is proposed. The analytical strategy is conceptually proposed and successfully demonstrated on the basis of (i) the microchip design (with the possibility to use both reservoirs), (ii) the analytical characteristics of the developed method (statically zero intercept and excellent robustness between calibration slopes, RSDs < 5%), (iii) the irreversible electrochemical behaviour of isoflavone oxidation (no significant electrode fouling effect was observed between calibration and analysis runs) and (iv) the inherent versatility of the electrochemical end-channel configurations (possibility of use different pumping and detection media). Repeatability obtained in both standard (calibration) and real soy samples (analysis) with values of RSD less than 1% for the migration times indicated the stability of electroosmotic flow (EOF) during both integrated operations. The accuracy (an error of less than 6%) is demonstrated for the first time in these microsystems using a documented secondary standard from the Drug Master File (SW/1211/03) as reference material. Ultra fast calibration and analysis of total isoflavones in soy samples was integrated successfully employing 60 s each; enhancing notably the analytical performance of these microdevices with an important decrease in overall analysis times (less than 120 s) and with an increase in accuracy by a factor of 3.