Comparative Study of Sample Carriers for the Identification of Volatile Compounds in Biological Fluids Using Raman Spectroscopy

Abstract

Vibrational spectroscopic techniques and especially Raman spectroscopy are gaining ground in substituting the officially established chromatographic methods in the identification of ethanol and other volatile substances in body fluids, such as blood, urine, saliva, semen, and vaginal fluids. Although a couple of different carriers and substrates have been employed for the biochemical analysis of these samples, most of them are suffering from important weaknesses as far as the analysis of volatile compounds is concerned. For this reason, in this study three carriers are proposed, and the respective sample preparation methods are described for the determination of ethanol in human urine samples. More specifically, a droplet of the sample on a highly reflective carrier of gold layer, a commercially available cuvette with a mirror to enhance backscattered radiation sealed with a lid, and a home designed microscope slide with a cavity coated with gold layer and covered with transparent cling film have been evaluated. Among the three proposed carriers, the last one achieved a quick, simple, and inexpensive identification of ethanol, which was used as a case study for the volatile compound, in the biological samples. The limit of detection (LoD) was found to be 1.00 μL/mL, while at the same time evaporation of ethanol was prevented.

Development of Analytical Method for the Quantitation of Monoclonal Antibodies Solutions via Raman Spectroscopy: The Case of Bevacizumab

“…This sample carrier was a classic microscope slide consisting of two layers; one external bare gold layer (1000 Å) and a second layer of titanium (Ti) (50 Å) binding the external gold layer to the glass of the microscope slide. The slides’ dimensions were 2.6 cm × 7.6 cm and their thickness was 1.0 mm [ 49 ]. For the developed quantitative method, each slide was cut into three pieces, so that each slide would be rectangular with a size of approximately 2.6 cm.…”

Formation and Characterisation of Posaconazole Hydrate Form

“…The gold slide dimensions were 2.5 cm × 7.5 cm with 1.0 mm thickness. A binding layer of titanium (50 Å) was deposited under the gold layer (1000 Å), which serves as a reflectance surface [ 44 ]. For the acquisition of the micro-Raman spectrum of posaconazole Form-S isolated after filtration, the precipitate was placed on the 1-well cavity of a glass slide coated with gold substrate and it was covered with the 6 μm LDPE cling film for the delay of the polymorphic transition.…”

μ-Raman Determination of Essential Oils’ Constituents from Distillates and Leaf Glands of Origanum Plants

“…The experimentation with different kinds of sample carriers encountered in the literature also outlines the research efforts to minimize the evaporation rate of the volatile analytes. In a study of ethanol determination in urine samples [ 15 ], a highly reflective gold layer carrier, a cuvette with a lid and a gold coated slide with a cavity and covered with cling film were tested, in order to find the appropriate carrier regarding the minimum required sample volume and the prevention of evaporation. Similarly, different fluid sample carriers were screened for Raman measurements of human serum, initially tested with ethanol, including glass slides with a hole to trap the liquid under a coverslip, coverslip-covered O-rings on glass or quartz slides and the eventually proposed, mirror-finished stainless-steel plate with holes [ 16 ].…”