Recent technological advancements in the photonics industry have led to a resurgence of interest in optical glucose sensing and to realistic progress toward the development of an optical glucose sensor Such a sensor has the potential to significantly improve the quality of life for the estimated 16 million diabetics in this country by making routine glucose measurements more convenient Currently over 100 small companies and universities are working to develop noninvasive or minimally invasive glucose sensing technologies, and optical methods play a large role in these efforts This article reviews many of the recent advances in optical glucose sensing including optical absorption spectroscopy, polarimetry, Raman spectroscopy, and fluorescent glucose sensing In addition a review of calibration and data processing methods useful for optical techniques is presented

https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics/volume-5/issue-01/0000/Optical-glucose-sensing-in-biological-fluids-an-overview/10.1117/1.429962.pdf

Optical glucose sensing in biological fluids: an overview.

Partial discharge (PD) is usually aroused before the failure of gas insulated switchgear (GIS) caused by defects, which results in the decomposition of the SF6 used as insulating gas. Analyzing SF6 decomposition products can aid in PD detection. Before recognizing PD types by analyzing SF6 decomposition products, the decomposition characteristics of SF6 under different types of PD should be investigated first. In this paper, a gas chamber and four typical types of artificial defects were designed to simulate the SF6 decomposition phenomenon under PD in GIS. A gas chromatography system was established to detect SF6 decomposition products. By selecting the chromatographic column, SF6 decomposition products were successfully separated and their concentrations were measured. Numerous SF6 decomposition experiments under four kinds of PD generated by four kinds of artificial defects were carried out and the SF6 decomposition products produced by each experiment were detected. The decomposition characteristics of SF6 under the four defects were different in terms of decomposition amount, generation rate, and concentration ratio, among others. It is feasible to recognize the type of PD by analyzing SF6 decomposition products.

Partial discharge recognition through an analysis of SF 6 decomposition products part 1: decomposition characteristics of SF 6 under four different partial discharges

Gases for electrical insulation are essential for the operation of electric power equipment. This Review gives a brief history of gaseous insulation that involved the emergence of the most potent industrial greenhouse gas known today, namely sulfur hexafluoride. SF6 paved the way to space-saving equipment for the transmission and distribution of electrical energy. Its ever-rising usage in the electrical grid also played a decisive role in the continuous increase of atmospheric SF6 abundance over the last decades. This Review broadly covers the environmental concerns related to SF6 emissions and assesses the latest generation of eco-friendly replacement gases. They offer great potential for reducing greenhouse gas emissions from electrical equipment but at the same time involve technical trade-offs. The rumors of one or the other being superior seem premature, in particular because of the lack of dielectric, environmental, and chemical information for these relatively novel compounds and their dissociation...

Assessment of Eco-friendly Gases for Electrical Insulation to Replace the Most Potent Industrial Greenhouse Gas SF6

Background: Practical improvements are needed to allow measurement of glucose concentrations by Fourier- transform infrared (FT-IR) spectroscopy. We developed a new method that allows determination of the glucose concentration in dried sera.

Methods: We studied 32 serum samples after fourfold dilution and desiccation before FT-IR analyses on a spectrometer operated at a resolution of 2.0 cm−1. We integrated all spectral windows at the surface of the spectrum in the C—O region. For comparison, glucose was measured in the sera by a glucose oxidase method.

Results: One peak within the spectrum was most specific for glucose (997–1062 cm−1). Its surface integration showed a strong relationship with reference data ( r = 0.998; P <0.001). FT-IR analyses of five glucose solutions were performed to determine its specific absorption at the same peak. In this way, glucose concentrations in serum spectra could be measured. For the first time while using FT-IR spectroscopy, no manipulation of spectra nor use of internal standard was necessary to obtain results in high accordance with glucose concentration measured by a conventional (glucose-oxidase) method ( S y|x = 0.25 mmol/L; r = 0.998).

Conclusions: FT-IR spectroscopy appears to be an easy and accurate method to determine glucose concentration and could be widely used to simultaneously identify and quantify several metabolites in biological fluids or tissues.

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Determination of Glucose in Dried Serum Samples by Fourier-Transform Infrared Spectroscopy

There remains a need for objective and cost-effective approaches capable of diagnosing early-stage disease in point-of-care clinical settings. Given an increasingly ageing population resulting in a rising prevalence of chronic diseases, the need for screening to facilitate the personalising of therapies to prevent or slow down pathology development will increase. Such a tool needs to be robust but simple enough to be implemented into clinical practice. There is interest in extracting biomarkers from biofluids (e.g., plasma or serum); techniques based on vibrational spectroscopy provide an option. Sample preparation is minimal, techniques involved are relatively low-cost, and data frameworks are available. This review explores the evidence supporting the applicability of vibrational spectroscopy to generate spectral biomarkers of disease in biofluids. We extend the inter-disciplinary nature of this approach to hypothesise a microfluidic platform that could allow such measurements. With an appropriate lightsource, such engineering could revolutionize screening in the 21st century.

Vibrational spectroscopy of biofluids for disease screening or diagnosis: translation from the laboratory to a clinical setting.

Infrared spectroscopy shows an enormous potential for the analysis of by-products generated from electrical discharges in sulfur-hexafluoride (SF6) insulated equipment. Since by-product composition can be related to the fault genesis (arc, partial discharge or corona), the analysis of contaminated SF6 provides a valuable diagnostic tool. The IR-spectrometric results from discharge experiments are presented, carried out with the application of SF6 pressures around 300 kPa and an alternating voltage up to 30 kV. Under the discharge conditions used, the main by-products found are the sulfuroxyfluorides SOF4 and SO2F2 with concentrations correlated to the discharge time. Due to its toxicity, special attention is also paid to S2F10. The experimental conditions and practical aspects for reliable quantitative analysis of reactive species are discussed.

Gas analysis by infrared spectroscopy as a tool for electrical fault diagnostics in SF6 insulated equipment

A multicomponent assay for the blood substrates of total protein, glucose, total cholesterol, triglycerides and urea in human EDTA-plasma by FT-IR spectroscopy is described based on near-infrared spectra of human plasma recorded in a 1 mm quartz transmission cell. Partial least-squares was applied for multivariate calibration taking into account absorbance or logarithmized single beam spectra. Further data reduction was applied using the pairwise selection of spectral variables suggested by the weights of the optimum full spectrum PLS-regression vector. The standard errors of prediction for protein, cholesterol, triglycerides, glucose and urea are calculated by cross-validation for the population of 124 plasma samples of different patients. These values are compared for full spectrum and reduced spectral variable set regression.

Multivariate calibration for near-infrared spectroscopic assays of blood substrates in human plasma based on variable selection using PLS-regression vector choices

The optimum number of spectral variables necessary for analytical spectroscopy is still a subject of debate. For sensor applications using miniaturized instrumentation, a small set of significant wavelengths with robust predictive performance is especially appreciated. A fast procedure is proposed, based on pairwise selection of spectral variables suggested by the weights of the optimum PLS-regression vector. The performance of multiple linear regression models based on such choices was similar to, and sometimes improved on full spectrum based modeling. Several examples from clinical studies of blood substrate assays using attenuated total reflection infrared spectroscopy of biofluids are presented.

Rapid and reliable spectral variable selection for statistical calibrations based on PLS-regression vector choices

Several biosensors have been developed for continuous monitoring of human blood glucose, which is desirable for insulin-dependent diabetic patients. Developments in the field of quantitative assays using infrared attenuated total reflection spectroscopy allow the determination of metabolites at low concentrations. The microdialysis technique can provide a continuous sampling of extracellular body fluids. As only compounds of low molecular weight are passed on, infrared spectrometric quantitation is eased considerably. Samples were obtained by microdialysis of human blood plasma and aqueous glucose solutions. Multivariate calibration by partial least-squares was evaluated for its analytical performance in ex-vivo blood glucose monitoring. Mean squared prediction errors obtained by cross validation were 5.4 mg/dL for dialysate samples from different patients and 1.3 mg/ dL for dialysates from glucose solutions. Further investigations were carried out to achieve miniaturization of the measuring and detection device.

Ex-vivo determination of blood glucose by microdialysis in combination with infrared attenuated total reflection spectroscopy

Compressed gaseous sulphur hexafluoride is commonly used as an insulating medium in high-voltage equipment. In the presence of traces of oxygen and moisture, SF6 can undergo decomposition under electrical stress. FT-IR-spectroscopic methods provide the possibility for a multicomponent trace gas analysis in the SF6-matrix with the option of on-line measurements. Decomposition compounds, produced by partial discharges, can be determined by multivariate spectral data analysis. Time-dependent concentration changes of the SF6 impurities in different infrared gas cells have been evaluated.

H. M. Heise

Papers

Gas analysis by infrared spectroscopy as a tool for electrical fault diagnostics in SF6 insulated equipment

Multivariate calibration for near-infrared spectroscopic assays of blood substrates in human plasma based on variable selection using PLS-regression vector choices

Rapid and reliable spectral variable selection for statistical calibrations based on PLS-regression vector choices

Ex-vivo determination of blood glucose by microdialysis in combination with infrared attenuated total reflection spectroscopy

Investigation of Electrically Stressed SF6 Gas by Using FT-IR Spectroscopy