Point-of-use devices represent currently a key field in
quantitative analytical sciences. These platforms are low-cost, fast, portable,
and simple to use eliminating the necessity for qualified operators. Rapid
tests enable in-situ measurements presenting substantial social and economic
implications at industry, environment, and medicine. One potential output to
perform point-of-use analyses is the accomplishment of the tests in solution
with naked eye detection using disposable systems. It allows the determination
of different analytes from the use of modified nanomaterial. Naked eye methods
bypasses the use of instrumental readers, an essential feature for in-situ
technologies. Furthermore, the analyses in solution surpass precisionrelated
downsides when making the tests on substrates such as paper.
In this case, the
diverse paper substrates that are employed to fabricate the devices affect the
flow rates and interactions with analytes.This paper reports further
investigations and application of the microemulsification-based method (MEC), a
point-of-use platform that was recently proposed by these authors. It relies on
solutionbased- detection with naked eyes. In contrast with colorimetric tools,
MEC response depends on colloid thermodynamics by relying on effect of analyte
on the entropy of emulsions or Winsor systems. It changes the formation ofthermodynamically stable dispersions, the microemulsions (MEs). The minimum
volume fraction of amphiphile (AP) needed to get MEs (ΦME) for a fixed
water-oil ratio expressed the analytical signal of the method.
The generation of nanodroplets in MEs
(transparent) allows the naked eye detection of ΦME by monitoring the change of
turbidity from the emulsions or Winsor systems (cloudy). This
cloudy-to-transparent conversion acts like a turning point in titrations,
ensuring the visual measurement of ME and, therefore, not only screening
analyses (positive/negative data) as the most of naked eye colorimetry
platforms as well as precise quantitative analyses. The response in colorimetry
changes with the intensity of colour or tonality. Herein, subjective
uncertainties by personal and surrounding conditions are observed.
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