Smelling in Chemically Complex Environments: An Optofluidic Bragg Fiber Array for Differentiation of Methanol Adulterated Beverages

Abstract

A novel optoelectronic nose for analysis of alcohols (ethanol and methanol) in chemically complex environments is reported. The crossresponsive sensing unit of the optoelectronic nose is an array of three distinct hollow-core infrared transmitting photonic band gap fibers, which transmit a specific band of IR light depending on their Bragg mirror structures. The presence of alcohol molecules in the optofluidic core quenches the fiber transmissions if there is an absorption band of the analyte overlapping with the transmission band of the fiber; otherwise they remain unchanged. The cumulative response data of the fiber array enables rapid, reversible, and accurate discrimination of alcohols in chemically complex backgrounds such as beer and fruit juice. In addition, we observed that humidity of the environment has no effect on the response matrix of the optoelectronic nose, which is rarely achieved in gas-sensing applications. Consequently, it can be reliably used in virtually any environment without precalibration for humidity or drying the analytes. Besides the discussed application in counterfeit alcoholic beverages, with its superior sensor parameters, this novel concept proves to be a promising contender for many other applications including food quality control, environmental monitoring, and breath analysis for disease diagnostics.

Detection of low molecular weight adulterants in beverages by direct analysis in real time mass spectrometry

“…11 A number of other techniques, including liquid chromatography, have been explored. 12–14 Prior work focusing on the detection of alcohols by DART-MS proved it was possible with sample derivatization. 15 This work highlights the ability of DART-MS to analyze these potential adulterants without derivatization as both neat samples, and in the complex solutions of common beverages.…”

Photonic bandgap narrowing in conical hollow core Bragg fibers

“…11 In our previous studies, we developed an artificial nose concept utilizing hollow core Bragg fibers as an infrared filter, as well as a gas chamber and a waveguide. [12][13][14] In this scheme, light from a blackbody source is coupled to the fiber, and its transmitted total intensity is measured with an infrared detector. If there is an overlap between an absorption band of the analyte and the bandgap of the fiber, the transmission is quenched, and this indicates the presence of the analyte.…”

“…[15][16][17] However, typical Bragg fibers with large bandgaps in the mid-infrared region are often responsive to multiple analytes, which may hinder the selectivity of the fiber array. 13,14 Additionally, when the bandgap of the fiber is wide, light is transmitted at the redundant parts of the bandgap, where the transmission is not quenched even after the analyte is introduced to the hollow core of the fiber. This effect weakens the response of the fiber to the analyte.…”

“…A polymer chalcogenide composite preform with alternating layers of arsenic triselenide (As 2 Se 3 ) and polyether sulphone (PES) was fabricated with conventional methods. 4,14 The preform was fed in to the fiber tower C with a constant down feed speed v d of 8 mm/min under constant load, and scaled down to a diameter of approximately 1.7 mm, where a photonic bandgap range of about 12 lm was reached. At this point, the load on the fiber was changed steeply (in the range of 0.1 to 0.6 kg) by changing the capstan speed (i.e., draw speed) v c ( Fig.…”

“…It should also be noted that wide bandgaps and higher order bands may respond to chemicals other than the intended analyte and result in non-selective detection. 13,14 Therefore, the ability to tune the width of the fundamental band and to eliminate undesired higher order bands in hollow core photonic bandgap fibers is advantageous for high-selectivity chemical sensing efforts.…”