Abstract
Raman spectroscopy has proven to be an indispensable technique for the identification of various types of analytes due to the fingerprint vibration spectrum obtained. Paper microfluidics has also emerged as a low cost, easy to fabricate and portable approach for point of care testing. However, due to inherent background fluorescence, combining Raman spectroscopy with paper microfluidics is to date an unmet challenge in the absence of using surface enhanced mechanisms. We describe the first use of wavelength modulated Raman spectroscopy (WMRS) for analysis on a paper microfluidics platform. This study demonstrates the ability to suppress the background fluorescence of the paper using WMRS and the subsequent implementation of this technique for pharmaceutical analysis. The results of this study demonstrate that it is possible to discriminate between both paracetamol and ibuprofen, whilst, also being able to detect the presence of each analyte quantitatively at nanomolar concentrations.
Highlights
Paper based sensing has emerged in the field of point of care testing with applications in the area of biosensing, environmental monitoring and food quality control.[1,2,3] Paper provides a means by which microfluidic devices can be fabricated in a very low-cost, simple and reproducible manner
The optimal conditions for wavelength modulated Raman spectroscopy (WMRS) required an optimisation of a number of factors including; the modulation amplitude, the time constant used for a single spectral acquisition, the sampling rate across one modulation cycle and the number of modulation cycles which are performed per experiment.[32]
This study demonstrates the first use of WMRS in combination with paper microfluidics for the real-time detection of multiple analytes simultaneously
Summary
Paper based sensing has emerged in the field of point of care testing with applications in the area of biosensing, environmental monitoring and food quality control.[1,2,3] Paper provides a means by which microfluidic devices can be fabricated in a very low-cost, simple and reproducible manner. Patterning of paper using techniques such as ink-jet and wax printing produce defined hydrophilic channels in the paper structure These control the flow of liquid through the sensor.[4,5] Due to the inherent wicking capability of paper, the passive transport of liquid through pre-defined channels is possible and a vast range of chemicals have been shown to be compatible with the paper substrate.[6] As a result of these key physical properties, paper microfluidics has emerged as a promising complementary technique to current microfluidic technologies with the key advantage of not requiring significant external instrumentation (e.g. microfluidic pumps) to function. Paper microfluidics has the promise to truly realise a lab on a chip (rather than a chip in a lab) device due to the approach being fast, simple to PLOS ONE | DOI:10.1371/journal.pone.0123334. Paper microfluidics has the promise to truly realise a lab on a chip (rather than a chip in a lab) device due to the approach being fast, simple to PLOS ONE | DOI:10.1371/journal.pone.0123334 May 4, 2015
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