A series
of unnatural amino acids functionalized with sterically
shielded pyrroline nitroxides were synthesized. Their reduction by
ascorbate/glutathione indicates that l-cysteine functionalized
with gem-diethylpyrroline nitroxide is reduced at
the slowest rate and is comparable to that measured for the most resistant
to reduction pyrroline and pyrrolidine nitroxides.
Demonstration of a simple melt based process to overcome the issue of poorly integrated, low activity and complicated methods of carbon electrode integration into microfluidics.
Mn concentrations were determined using square‐wave cathodic stripping voltammetry (CSV) with inexpensive, stencil‐printed carbon ink electrodes generated on polypropylene transparency films. Using an optimized pH 5 ammonium acetate buffer and addition of 1,4‐benzoquinone, a detection limit as low as 500 nM (30 ppb) was achieved. Addition of 1,4‐benzoquinone improved peak potential reproducibility and height, while addition of 3.5 % w/w sodium chloride to the background solution approximately doubled the sensitivity (μA/ppm). Tolerance tests with interfering metals were conducted and the method was found to be resilient to chromium(VI), iron(III), magnesium(II), nickel(II), and zinc(II), but susceptible to aluminum(III), copper(II), iron(II), and lead(II) at concentration ratios at or below one. This technique was successfully used to measure Mn levels in yerba mate and green tea samples as an example application.
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