Instrumental Requirements for Non-Invasive Blood Glucose Measurement Using NIR Spectroscopy

The magnitude of spectral change in blood glucose measurements with diffuse reflectance spectroscopy is investigated. Spectral change is estimated by simulation of light propagation in skin tissue and measurements of absorbance spectra of aqueous glucose solution. Required sensitivity of spectrophotometers for monitoring change in the blood glucose concentration as small as 10 mg/dL has been obtained using the estimated change in the absorbance spectrum and mean pathlength of light in tissue.     

Diode Laser‐Excited Optogalvanic and Absorption Measurements of Uranium in a Hollow Cathode Discharge

Optogalvanic spectra for fifty two transition lines of uranium in the wavelength ranges of 662–683, 774–792, and 834–862 nm were measured by using external‐cavity diode lasers. Among these transitions, 860.795 nm and 682.691 nm were chosen for a detailed investigation of the detection limit for uranium by wavelength modulation spectroscopy due to its stronger signal magnitudes. A detection limit of about 2 × 10^? 5 absorbance achieved at 860.795 nm is more sensitive than that obtained at 682.691 nm, but the absorption spectrum at 682.691 nm is preferable to determine the isotope ratio due to the narrower hyperfine structure as well as the larger isotope shift. A preliminary result for an isotope ratio determination in a depleted sample is presented.     

Optical pathlength saturation signatures in wavelength modulation spectroscopy signals of atmospheric molecular oxygen

We discuss experimental and theoretical results of absorption features of the oxygen A-band transitions in the optically thick regime when synchronous detection at higher harmonics (N≥2), using wavelength modulation spectroscopy (WMS), is performed. We show that the absorption saturation effects demonstrate a distinctive feature which results in suppression of the line-center lobes of the harmonic signals. These effects depend on the optical pathlength as well as on the modulation index. The rich structure of WMS signals, especially at higher detection orders, is central to the technique’s advantages in resolving spectra congested with highly disparate oscillator-strength lines. The effect of pathlength saturation on this structure is investigated.     

一种紫外-可见光谱法检测水质COD的浊度影响实验研究

消除浊度影响是直接光谱法检测水质COD的关键技术问题。此源于紫外-可见光谱法检测水质参数的关键依赖于化学计量法所建立的准确的水质参数分析模型,而浊度是影响其建模的一个重要参数。为此,选取福尔马肼浊度液和邻苯二甲酸氢钾标准溶液,开展了紫外-可见吸收光谱法检测水质COD的浊度影响实验研究,获得了选定溶液在245,300,360和560 nm几个特征波长点的吸光度随浊度变化的最小二乘法拟合曲线,分析了吸光度随浊度的变化规律。研究结果表明,在240～380 nm的紫外光谱段,由于引起浊度的颗粒物对有机物产生了吸附,致使浊度对水样的紫外光谱影响较为复杂;在380～780 nm的可见光谱区域,浊度对光谱的影响则是随着波长的增大而减弱。基于此,开展了多元散射校正法对受浊度影响的水样光谱进行校正试验。对某溪水水样的紫外-可见吸收光谱进行多元散射校正,通过处理前后光谱对比表明,浊度引起各个波长点的基线偏移都得到了有效的校正,而在紫外区域特征并未减弱。接着对选取的三种液体的紫外-可见吸收光谱进行多元散射校正,实验结果表明：该方法可在不影响水样紫外-可见吸收光谱特征的前提下对其吸收曲线进行有效的校正,这不仅提高了光谱法检测水质COD的信噪比,而且还为化学计量法建立准确、有效的水质检测COD分析模型进行数据预处理提供了一种新途径。     

Laser spectroscopic oxygen sensor using diffuse reflector based optical cell and advanced signal processing

In this paper, an improved signal processing method is given, aiming at a sensitivity improvement of the tunable diode laser spectroscopy based gas concentration measurement. The gas absorption spectrum is probed with an optimum wavelength scanning function which enables a more efficient curve fit than for traditional linear wavelength scanning. The wavelength scanning function is determined to be optimum, in the sense that the variance of the estimated concentration noise is minimized. This optimum scanning function depends on the signal model used in curve fitting. Several models including interfering gas spectra and etalon fringes are examined. Compared to the gas absorption spectrum recorded by ramping the wavelength linearly, the optimum spectrum waveforms have a cascade structure, which means that the optimum scanning preferably samples important points of the spectrum. The new method theoretically enables a factor of ∼2 improvement on detection sensitivity of the estimated concentration. Furthermore, direct spectroscopy is superior to second harmonic detection, because the concentration noise can be an additional factor of ∼2 lower.     

Comparison of band model and integrated line-by-line synthetic spectra for methane in the 2.3 μm region

The 2.3 μm spectral region of methane can be used to retrieve cloud properties of planetary spectra, provided parameters for the methane spectrum are known. Two standard techniques for calculating absorption spectra in this region are compared here. A Voigt profile Mayer-Goody random band model is applied, using coefficients empirically fitted by Fink et al. to CH₄ spectra recorded with high absorping amounts at 10 cm^?1 resolution. Calculation of the absorption is also done with a line-by-line direct integration method for the same gas conditions using molecular parameters obtained by combining an older unpublished list of observed positions and estimated line strengths (derived from 0.04 cm^?1 resolution data) with quantum assignments from the literature. The molecular parameters have been evaluated for the 4180–4590 cm^?1 region by comparing new laboratory spectra with 0.01 cm^?1 resolution recorded at 296 and 153K with synthetic spectra calculated at the same conditions. The deficiencies of the molecular parameters and random band coefficients for this spectral region of CH₄ are then discussed qualitatively and demonstrated by comparing 10 cm^?1 resolution synthetic spectra calculated by both methods for the same gas conditions at 296, 153, and 55 K.Curves of growth of the total equivalent width are calculated at 296 and 55K for a pathlength of 50 cm and pressures up to 10 atm. Changing the mean line spacing in the band model gives better agreement between the spectra calculated by the two techniques at low gas temperatures. The required multiplier has been determined for the mean line spacing for pressures from 10^?6 to 10^?1 atm at 55, 100, and 150 K.     

Tunable diode laser spectroscopy with optimum wavelength scanning

In this paper, an improved signal processing method is given, aiming at a sensitivity improvement of the tunable diode laser spectroscopy based gas concentration measurement. The gas absorption spectrum is probed with an optimum wavelength scanning function which enables a more efficient curve fit than for traditional linear wavelength scanning. The wavelength scanning function is determined to be optimum, in the sense that the variance of the estimated concentration noise is minimized. This optimum scanning function depends on the signal model used in curve fitting. Several models including interfering gas spectra and etalon fringes are examined. Compared to the gas absorption spectrum recorded by ramping the wavelength linearly, the optimum spectrum waveforms have a cascade structure, which means that the optimum scanning preferably samples important points of the spectrum. The new method theoretically enables a factor of ～2 improvement on detection sensitivity of the estimated concentration. Furthermore, direct spectroscopy is superior to second harmonic detection, because the concentration noise can be an additional factor of ～2 lower.     

Chemical and isotopic analysis using diode laser spectroscopy: applications to volcanic gas monitoring

We report on a diode-laser-based spectrometer, operating at a wavelength of 2 μm, which enables for simultaneous measurements of CO₂ and H₂O concentrations in gaseous mixtures with high precision and accuracy. We implemented the very simple approach of a direct measurement of absorption in a multiple reflection cell with a pathlength of 50 m. Gas concentration is simply retrieved from the integrated absorbance, without using calibration cells. The spectrometer is equipped with single-mode optical fibers in order to probe remote environments. The possible application in volcanic areas will be discussed. We also investigated the possibility to measure the isotopic ratio ¹³CO₂/¹²CO₂, which is another relevant parameter for monitoring volcanic activity.     

温度干扰下的葡萄糖水溶液近红外光谱修正方法与比较

水的近红外吸收光谱受温度影响较大,采用近红外光谱法对水溶液样本进行成分测量时,温度的影响不能忽视。特别对于葡萄糖这种弱吸收成分,温度的微小变化会对其测量精度造成较大影响。实验发现葡萄糖水溶液在30 ℃附近时,温度每变化1摄氏度,在1 160 nm处溶液的吸光度变异系数约0.344 7%,这个变化约相当于500～600 mg·dL-1葡萄糖浓度引起的溶液吸光度变化量。将近年来发展的几种化学计量学方法用于温度扰动下葡萄糖水溶液的光谱修正,以提高葡萄糖测量精度,具体包括广义最小二乘加权法(GLSW)和外部参数正交化方法(EPO)。对不同温度的葡萄糖水溶液样品在900～1 350 nm的光谱进行采集,测试了两种方法对温度变化后光谱的修正效果,考察了修正后光谱的葡萄糖预测误差,并与传统的考虑温度变量的多变量回归方法-偏最小二乘(PLS)回归法进行了比较。结果表明,GLSW和EPO方法对不同温度下的溶液光谱有好的校正效果,不同温度下溶液光谱的变异系数得到显著改善,同时两种方法在模型复杂性、温度修正效果等方面都优于传统方法。研究可推广到其他水份含量较大的样品测试场合,也对人体组织中的葡萄糖测量有借鉴价值。     

Photoluminescence Spectra in Polycrystals of Chirally Pure and Racemic Phases of Tryptophan

The photoluminescence spectra of three crystalline phase modifications of aromatic amino acid tryptophan are compared: the left phase of L-tryptophan, the right phase of D-tryptophan, and the racemic phase of DL-tryptophan. The photoluminescence spectra were recorded using a fiber-optic procedure, a small-size FSD-8 spectrometer, and a data processing system that enables comparison of the analyzed spectrum with the spectrum of a reference substance. Photoluminescence was excited by a pulsed-periodic ultraviolet laser at a wavelength of 266 nm.

     

金纳米粒子自组装薄膜的光谱学研究

采用柠檬酸钠还原氯金酸制备了金胶体，通过静电自组装制备了金纳米粒子薄膜，利用紫外-可见光吸收光谱等对金纳米粒子薄膜进行了光谱学研究，紫外-可见光吸收光谱表明所制备的金溶胶为单分散体系，根据自组装薄膜的X-射线衍射谱，由谢乐公式估算金纳米粒子的粒径约为21nm；X-射线光电子能谱显示氯金酸的还原反应比较完全，金主要以Au^0的价态存在，金胶体粒子通过静电吸引机制组装到PDDA改性的衬底表面；紫外-可见光吸收光谱和表面增强拉曼光谱显示，由于粒子间的电磁耦合，自组装金纳米粒子薄膜表现出协同等离子体共振吸收行为和表面增强拉曼散射效应。     

Silica luminescence induced by fast light ions

Silica luminescence induced by hydrogen and helium ions of 200 keV–2.4 MeV was experimentally studied in the near ultraviolet and visible wavelength ranges. The luminescence spectrum consists of three asymmetric wide bands with maxima at wavelengths of 282, 456 and 644–648 nm. For nonirradiated silica, it was shown that the spectral shape depends on observation angle, ion species and energy. The changes in the spectra and relations between light intensity of luminescence and both absorption dose and observation angle were determined. Differences in ionoluminescence spectra measured for molecular and atomic hydrogen ions were observed, i.e. the so-called “molecular effect” was found. The influence of different beam parameters (incidence angle, ion species and energy) on indicatrix at a wavelength of 456 nm was found for nonirradiated silica. The applications of ionoluminescence measurements for distant monitoring of silica irradiation processes are discussed.     

Probing nonparabolic conduction subbands in nanoscale InGaAs/InAlAs quantum wells with cyclotron resonance in very high magnetic fields

Nonparabolicity of conduction subbands in nanoscale potential wells has been probed using InGaAs/InAlAs multi-quantum well structures. From cyclotron resonance absorption at a wavelength of 119 μm, the apparent mass ratio was found to be 0.061 near the bottom of the ground subband. From cyclotron resonance absorption at a wavelength of 10.6 μm, the apparent mass ratio of high-energy electrons was found to be 0.066–0.067, which was higher than the bulk bandedge mass ratio, 0.041. Evidence of the two-dimensional conduction subbands was examined by an interband absorbance spectrum.     

Quantitative Analysis by Derivative Electronic Spectroscopy

Abstract

Absorption and emission spectroscopy in the ultraviolet and visible regions, apart from being the earliest physical techniques of analysis, have great utility in solving a variety of structural and analytical problems [l-41. However, in many cases the quantitative determination of individual components in a mixture by UV-VIS spectroscopy becomes very difficult owing to the spectral similarities and overlapping of weak absorption bands of one component by strong absorption bands of other components. It was recently recognized that derivative spectrophotometry, introduced about three decades ago [5-81 and originally proposed by Rutherford [9], can be a very useful analytical tool for characterizing an analyte band that is overlapped by other absorption bands with different halfwidths. On differentiation, the intensity of the absorption band with a small halfwidth increases more than that of a band with a large halfwidth [10]. The central idea behind the development of the science of derivatized spectra rests upon the measurement of the first or the higher derivatives of the absorbance A or the luminescence intensity I with respect to the wavelength λ, e.g., dI/dλ, dA/dλ, d²I/dλ², etc. These derivatives, when plotted or scanned against wavelength, yield an array of derivative spectra.     

Excited state absorption of 1,3,3,1′,3′,3′-hexamethylindotricarbocyanine Iodide: A quantitative study by ultrafast absorption spectroscopy

A quantitative investigation of HITC dissolved in methanol has been made using the method of ultrafast absorption spectroscopy with a streak camera. Samples were excited by picosecond pulses of a mode-locked ruby laser. Analysis of time-resolved spectra yielded non-exponential decay kinetics consisting of a fast (τ variable) and a slow (τ=1.13±0.08 ns) component. The excited state absorption spectrum has its maximum at 493 nm and shoulders at 415 and 540 nm. The excited state absorption cross section was determined by simulataneous measurement of the bleaching of ground state absorption taking polarization of excitation and probe light and excited state absorption at the laser wavelength into account. A value of σ₁ (493 nm)=1.0·10^?16 cm² was found.     

Direct determination of glucose, lactate and triglycerides in blood serum by a tunable quantum cascade laser-based mid-IR sensor

This work reports on a compact sensor for fast and reagent-free point-of-care determination of glucose, lactate and triglycerides in blood serum based on a tunable (1030–1230 cm^?1) external-cavity quantum cascade laser (EC-QCL). For simple and robust operation a single beam set-up was designed and only thermoelectric cooling was used for the employed laser and detector. Full computer control of analysis including liquid handling and data analysis facilitated routine measurements. A high optical pathlength (>100 μm) is a prerequisite for robust measurements in clinical practice. Hence, the optimum optical pathlength for transmission measurements in aqueous solution was considered in theory and experiment. The experimentally determined maximum signal-to-noise ratio (SNR) was around 140 μm for the QCL blood sensor and around 50 μm for a standard FT-IR spectrometer employing a liquid nitrogen cooled mercury cadmium telluride (MCT) detector. A single absorption spectrum was used to calculate the analyte concentrations simultaneously by using a partial-least-squares (PLS) regression analysis. Glucose was determined in blood serum with a prediction error (RMSEP) of 6.9 mg/dl and triglycerides with an error of cross-validation (RMSECV) of 17.5 mg/dl in a set of 42 different patients. In spiked serum samples the lactate concentration could be determined with an RMSECV of 8.9 mg/dl.     

Investigation of Rhodamine 6G in oleic acid solution fluorescence under high pressure

Interesting behavior has been observed in the absorption spectra of the solution of Rhodamine 6G [C₂₈H₃₁N₂O₃Cl] in oleic acid [C₁₈H₃₄O₂] [K. Wieja et al., Pressure-induced changes in electronic absorption spectrum in oleic acid, High Press. Res. 30 (2010), pp. 130–134]. Application of high pressures to the solution has caused the reshaping of the absorption spectra curve, and the maximum of absorption has been shifted towards the longer wavelength. One of the most possible explanations of the changes in the absorption spectra is the formation of charge-transfer complexes in the solution. Pressure-induced changes of the VIS absorption spectrum in the mixture of Rhodamine 6G and oleic acid have been observed in comparison with the absorption spectrum of the mixture of Rhodamine 6G in ethanol. Moreover, changes have been observed in the fluorescence spectrum of the examined mixture, which indicated a fluorescent electronic band of a CT complex.     

Magnetic Circular Dichroism Spectra of p-Disubstituted Benzenes Possessing Both Electron-Donating and Accepting Groups

Abstract

The magnetic circular dichroism (MCD) and absorption spectra of some p-disubstituted benzenes possessing both electron-donating and accepting groups were measured. The electronic spectra of the above compounds are characterized by the appearance of two absorption bands, one of which appears at 25000–40000 cm^?1 region with large intensity, and another at 40000–50000 cm^?1 region with rather small intensity. These absorption bands, especially the latter one, have been investigated by means of the MCD spectra and molecular orbital calculations based on the Pariser-Parr-Pople method.     

Photoluminescence of polycrystalline cadmium sulfide films at 77 °K

The absorption, reflection, emission, and luminescence spectra of polycrystalline cadmium sulfide films have been studied at 77 deg K at 4500–5500 A. The films were prepared by sublimination of the powder in argon, hydrogen sulfide, or vacuum, followed by crystallization on a heated or unheated substrate.Specimens deposited on substrates below 350 deg C had simple absorption and emission spectra no matter which medium was used, but ones coated on substrates above 350 deg C had absorption, reflection, luminescence, and emission spectra with fine structure, which was due to transitions between the 5s²¹S₀ ground state and 5s5p³P₁, 5s5p³P₂, and 5s5p³P₀ excited states of atomic excess cadmium.Four maxima were found in the excitation spectrum of the blue luminescence (4545, 4605, 4670, and4740 A). The spectrum of the luminescence is independent of exciting wavelength in the range 2200–4900 A.This structure was observed only for films with hexagonal lattice symmetry.     

Study on the Fluorescence Quenching Reaction of Amitriptyline and Clomipramine Hydrochlorides with Eosin Y and its Analytical Application

Amitriptyline.HCl (AMI) and clomipramine.HCl (CMI) react with eosin Y (EY) in pH 3.8 NaAc-AcH buffer solution to form ion association complex which results in quenching of fluorescence of EY and appearance of a new resonance Rayleigh scattering (RSS) spectrum at 620 nm. The spectral characteristics of absorption, fluorescence and RSS spectra have been investigated. The factors influencing the reaction were studied and optimum conditions for the reaction have been determined. Based on fluorescence quenching, a simple and sensitive spectrofluorimetric method for determination of AMI and CMI has been developed. The fluorescence quenching intensity was measured at 550 nm using an excitation wavelength of 310 nm. The calibration graph was found to be rectilinear in the range 0.08–2.0 μg?mL^?1 with detection limit of 0.017 μg?mL^?1 for AMI and 0.06–2.0 μg?mL^?1 with detection limit of 0.015 μg?mL^?1 for CMI. The method can be satisfactorily applied to the determination of AMI and CMI in tablets without interference from commonly occurring exicipients. The recovery and RSD values obtained indicate good accuracy and precision of the method. The mechanism of the reaction and fluorescence quenching has also been discussed.