Digital image determination of copper in food and water after preconcentration and magnetic tip separation for in-cavity desorption/color development.

A new analytical method for measuring copper in food and water was developed and validated, employing a solid-phase extraction (SPE) technique combined with digital-image-based (DIB) detection. A novel magnetic adsorbent of zinc ferrite/Citrullus colocynthis biochar (ZF@C.BC) was used to preconcentrate copper. A magnetic tip was used to separate the copper-loaded adsorbent from the extraction medium and to dispense it to the DIB plate. In-situ desorption and development of the spot color with iodide-starch reagent were carried out, and a digital image of the developed spots was captured using a smartphone and processed using ImageJ software. The copper adsorption capacity was 91.3 mg g-1. Desorption was effected using a 0.3 mol L-1 hydrochloric acid. The preconcentration factor was 300, the limit of detection was 4.8 µg L-1, the linearity was 16-600 µg L-1 and the sample throughput was 12 h-1. The developed approach was validated by analyzing food and water samples, confirming recoveries ≥ 91 % and 88 %, respectively, with RSD ≤ 8.4 %, n = 3.

Molybdenum Carbide/Ni Nanoparticles Embedded into Carbon Nanofibers as an Effective Non-Precious Catalyst for Green Hydrogen Production from Methanol Electrooxidation.

Molybdenum carbide co-catalyst and carbon nanofiber matrix are suggested to improve the nickel activity toward methanol electrooxidation process. The proposed electrocatalyst has been synthesized by calcination electrospun nanofiber mats composed of molybdenum chloride, nickel acetate, and poly (vinyl alcohol) under vacuum at elevated temperatures. The fabricated catalyst has been characterized using XRD, SEM, and TEM analysis. The electrochemical measurements demonstrated that the fabricated composite acquired specific activity for methanol electrooxidation when molybdenum content and calcination temperature were tuned. In terms of the current density, the highest performance is attributed to the nanofibers obtained from electrospun solution having 5% molybdenum precursor compared to nickel acetate as a current density of 107 mA/cm2 was generated. The process operating parameters have been optimized and expressed mathematically using the Taguchi robust design method. Experimental design has been employed in investigating the key operating parameters of methanol electrooxidation reaction to obtain the highest oxidation current density peak. The main effective operating parameters of the methanol oxidation reaction are Mo content in the electrocatalyst, methanol concentration, and reaction temperature. Employing Taguchi's robust design helped to capture the optimum conditions yielding the maximum current density. The calculations revealed that the optimum parameters are as follows: Mo content, 5 wt.%; methanol concentration, 2.65 M; and reaction temperature, 50 °C. A mathematical model has been statistically derived to describe the experimental data adequately with an R2 value of 0. 979. The optimization process indicated that the maximum current density can be identified statistically at 5% Mo, 2.0 M methanol concentration, and 45 °C operating temperature.