CCD Spectrometer Research Articles

Comparison of detection modes in terms of the necessity of visible region (VIS) and influence of the peel on soluble solids content (SSC) determination of navel orange using VIS–SWNIR spectroscopy

Comparison of three detection modes (interactance, reflectance and transmittance) was performed in terms of the necessity of visible (VIS) region and the interference caused by peel in SSC assessment of navel oranges. Spectra of 88 oranges with peel and peeled were collected using a commercial available CCD spectrometer. Partial least squares (PLS) regression was used to develop calibration models. Results showed that the participation of VIS region degraded the performances of PLS models in transmittance mode, while for the other two modes VIS–SWNIR models turned out to be the best. The peel of oranges did not bring about significant negative influence on SSC determination in any detection mode. The best calibration models were achieved with transmittance mode regardless of sample status. Future research should be focused on specific reasons such as the composition of orange peel and the influence of different sizes of fruits.

Trace detection of perchlorate in industrial-grade emulsion explosive with portable surface-enhanced Raman spectroscopy

Recent analyses by ion-exchange chromatography (IC) showed that, beside nitrate, the majority of the industrial-grade emulsion explosives, extensively used by most separatists in the southern Thailand insurgency, contained small traces of perchlorate anions. In demand for the faster, reliable, and simple detection methods, the portable detection of nitrate and perchlorate became the great interest for the forensic and field-investigators. This work proposed a unique method to detect the trace amount of perchlorate in seven industrial-grade emulsion explosives under the field tests. We utilized the combination of the portable Raman spectroscope, the developed surfaced-enhanced Raman substrates, and the sample preparation procedures. The portable Raman spectroscope with a laser diode of 785nm for excitation and a thermoelectric-cooled CCD spectrometer for detection was commercially available. The SERS substrates, with uniformly distributed nanostructured silver nanorods, were fabricated by the DC magnetron sputtering system, based on the oblique-angle deposition technique. The sample preparation procedures were proposed based on (1) pentane extraction technique and (2) combustion technique, prior to being dissolved in the purified water. In comparison to the ion chromatography and the conventional Raman measurements, our proposed methods successfully demonstrated the highly sensitive detectability of the minimal trace amount of perchlorate from five of the explosives with minimal operating time. This work was therefore highly practical to the development for the forensic analyses of the post-blast explosive residues under the field-investigations.

Simulation of spectroscopic patterns obtained in W/C test-limiter sputtering experiment at TEXTOR

On the TEXTOR tokamak various experiments aimed at investigation of tungsten erosion and transport are performed. In one experiment a spherical W/C twin limiter positioned close to the last-closed flux surface in the near scrape-off layer was exposed to a number of comparable plasma discharges with stepwise variations of edge plasma parameters. Spatial distribution of tungsten and carbon light emission was recorded with two dimensional CCD cameras and spectrometer systems with high spectral and spatial resolution. Penetration depths, tungsten sputtering fluxes and erosion yields were measured. Comparison between experimental data and the results of modelling with the 3D Monte-Carlo code ERO is performed. The main objective of this study was to test the adequacy of the existing atomic data for neutral tungsten. The modelled penetration depths of the light emission of tungsten are a factor of 2–3 smaller than in experiment, which may indicate the overestimation of ionization rates.

Improvement of selenium analysis during laser-induced breakdown spectroscopy measurement of CuIn1−xGaxSe2 solar cell films by self-absorption corrected normalization

The analysis of Se emission lines (196.089 nm and 203.984 nm) of CuIn1−xGaxSe2 (CIGS) thin solar cell films by laser-induced breakdown spectroscopy (LIBS) is reported. With CIGS thin films fabricated by co-evaporation or sputtering methods, LIBS measurement was carried out using a nanosecond laser (λ = 532 nm, τ = 5 ns, top-hat profile) and a CCD spectrometer (gate width = 1.05 ms, gate delay = 0.2 μs) in a flowing Ar gas environment (20 L min−1). From the comparison of calibration curves, it was found that the correlation between the Se/Cu LIBS intensity ratio and the Se/Cu concentration ratio could be improved significantly by applying the self-absorption correction procedure introduced in this study, demonstrating the significance of self-absorption in those Se emission lines. It was shown that normalization alone could reduce the relative standard deviation but was insufficient for accurate LIBS analysis of Se in CIGS thin films.

Determining the Composition of Proteins in Milk Using a Portable near Infrared Spectrometer

The content ratio of whey proteins to casein can serve as an indicator of milk quality as well as criterion for the presence of milk proteins adulteration, if it exceeds 0.25. The actual task is to produce an effective and portable sensor for the named ratio. The applicability of an inexpensive portable near infrared spectrometer for the specified task was tested in this work. The streams of backscattering and transmission light in the samples of the restored milk were acquired in the form of optical density spectra for a wavelength range of 800–1065 nm using a new two-channel CCD spectrometer. It was calibrated on the content of fat, casein and whey proteins using partial least squares regression. Another objective was to develop a cost-effective way to obtain a set of reference samples with various concentrations of three components that are needed to create the calibration models or to test them. Testing the calibration designed for the measurement of fat, casein and whey proteins in drinking milk showed root mean squared errors of prediction of 0.09% wt, 0.12% wt and 0.06%wt, and correlation coefficients of 0.90, 0.82 and 0.89, respectively. The value of the 95th percentile for the ratio of whey proteins to casein was found to be±0.06, which is sufficiently low for practical use of the method. A comparison of models, one of which was built using the proposed “custom” set of 35 samples and the other which was based on a random set of 81 samples, showed similar acceptable results. Thus, the proposed method is suitable for cost reduction without loss of calibration quality.

Total viable bacterial count using a real time all-fibre spectroscopic system

Rapid, accurate and sensitive enumeration of bacterial populations in the natural environment is an essential task for many research fields. Widely used standard methods for counting bacteria such as heterotrophic plate count require 1 to 8 days of incubation time for limited accuracy, while more accurate and rapid techniques are often expensive and may require bulky equipment. In the present study, we have developed a computerized optical prototype for bacterial detection. The goal of this research was to estimate the potential of this optical system for Total Viable Bacterial Count in water. For this purpose, we tested water batches with different microbiological content. Bacterial detection was based on fluorescence enhanced by nucleic acid staining. High sensitivity was achieved by a stable diode pumped solid state laser, sensitive CCD spectrometer and in situ excitation and signal collection. The results have shown that the bacterial count from different water origins using our optical setup along with multivariate analysis presents a higher accuracy and a shorter detection time compared to standard methods. For example, in a case where the fluorescence signal is calibrated to the water batch regression line, the relative standard deviation of the optical system enumeration varies between 21 and 36%, while that of the heterotropic plate count counterpart varies between 41 and 59%. In summary, we conclude that the all-fibre optical system may offer the following advantages over conventional methods: near real time examinations, portability, sensitivity, accuracy and ability to detect 10(2) to 10(8) CFU per ml bacterial concentrations.

Single-shot spectra of temporally selected micropulses from a mid-infrared free-electron laser by upconversion

We demonstrate the measurement of single-shot spectra of temporally selected micropulses from a mid-infrared free-electron laser (FEL) by upconversion. We achieve the upconversion of FEL pulses at 11μm using externally synchronized Nd:YAG or microchip laser pulses at 1064nm to produce sum-frequency mixing signals at 970nm, which are detected by a compact CCD spectrometer without an intensifier. Our experimental system is very cost-effective, and allows us to obtain the laser spectra of selected micropulses at any temporal position within a single macropulse from an oscillator-type FEL.

Performance of the NIST goniocolorimeter with a broad-band source and multichannel charged coupled device based spectrometer

The authors describe the NIST high-efficiency instrument for measurements of bidirectional reflectance distribution function of colored materials, including gonioapparent materials such as metallic and pearlescent coatings. The five-axis goniospectrometer measures the spectral reflectance of samples over a wide range of illumination and viewing angles. The implementation of a broad-band source and a multichannel CCD spectrometer corrected for stray light significantly increased the efficiency of the goniometer. In the extended range of 380 nm to 1050 nm, a reduction of measurement time from a few hours to a few minutes was obtained. Shorter measurement time reduces the load on the precise mechanical assembly ensuring high angular accuracy over time. We describe the application of matrix-based correction of stray light and the extension of effective dynamic range of measured fluxes to the values of 10(6) to 10(7) needed for the absolute characterization of samples. The measurement uncertainty was determined to be 0.7% (k = 2), which is comparable with similar instruments operating in a single channel configuration. Several examples of reflectance data obtained with the improved instrument indicate a 0.3% agreement compared to data collected with the single channel configuration.

Recent improvements of the JET lithium beam diagnostic

A 60 kV neutral lithium diagnostic beam probes the edge plasma of JET for the measurement of electron density profiles. This paper describes recent enhancements of the diagnostic setup, new procedures for calibration and protection measures for the lithium ion gun during massive gas puffs for disruption mitigation. New light splitting optics allow in parallel beam emission measurements with a new double entrance slit CCD spectrometer (spectrally resolved) and a new interference filter avalanche photodiode camera (fast density and fluctuation studies).

Laser induced breakdown spectroscopy for fast elemental analysis and sorting of metallic scrap pieces using certified reference materials

A setup utilizing laser induced breakdown spectroscopy (LIBS) for performing elemental analysis in order to classify metallic samples is currently under construction. The setup uses short laser pulses to locally ablate the sample and create luminous plasmas. The emitted light is analyzed spectroscopically for instantaneous determination of the elemental composition. A table-top system based on a compact CCD spectrometer has been constructed and combined with fast software in order to test the concept of remote, single shot material classification with LIBS. Certified reference materials with known elemental compositions were used in the laboratory tests. We report on successful laboratory tests in which samples were classified using an analysis based on optical emission following a single laser pulse and with an operating distance of approximately 1m. Details regarding field tests of this versatile and promising technique are discussed.

Flash heating in the diamond cell: Melting curve of rhenium

A new method for measuring melting temperatures in the laser-heated diamond cell is described. This method circumvents previous problems associated with the sample instability, thermal runaway, and chemical reactions. Samples were heated with a single, 20 milliseconds rectangular pulse from a fiber laser, monitoring their thermal response with a fast photomultiplier while measuring the steady state temperature with a CCD spectrometer. The samples were recovered and analyzed using scanning electron microscopy. Focused ion beam milling allowed to examine both the lateral and the vertical solid-liquid boundaries. Ambient pressure tests reproducibly yielded the known melting temperatures of rhenium and molybdenum. Melting of Re was measured to 50 GPa, a 5-fold extension of previous data. The refractory character of Re is drastically enhanced by pressure, in contrast to Mo.

Laser welding of copper with stellite 6 powder and investigation using LIBS technique

This paper reports a process by which two copper plates are welded together by using a millisecond pulse Nd:YAG laser with the addition of stellite 6 powder which increases the absorption of laser energy. It also reports an interesting application of Laser Induced Breakdown Spectroscopy (LIBS) in order to determine the elemental composition and diffusion of stellite 6 powder into the copper plates. The effects of laser peak power and pulse duration are examined to optimize the welding. The amount of stellite 6 powder is also optimized for a high quality welding. The tensile strength and hardness values are measured for different laser parameters. The EDX and SEM results show that the stellite 6 powder particles penetrate into the copper plates and increase the hardness. The elements in laser weld joints of copper plates were analyzed with LIBS, utilizing a high resolution multi-channel CCD spectrometer and a nanosecond pulse Nd:YAG laser, providing a depth profile of elemental composition of the penetrated region.

Spectral excitation of dielectric matrix trace atomic and molecular species by atmospheric pressure sliding spark plasma

The goal of this work was to investigate the potential of sliding spark plasma to excite from dielectrics emission spectra that have utility in direct trace quantitative analysis of non-conducting materials in air at atmospheric pressure. The sliding spark is a special variety of pulsed plasma specularly discharging across a dielectric surface enforced between a pair of electrodes. Analysis of the emission spectra measured between 212 ≤ λ ≤ 511 nm using CCD spectrometer showed that the sliding spark is accompanied by prompt atomic and molecular emission over a broad wavelength range. Each dielectric is characterized by unique spectral features composed of mostly overlapping atomic, ionic and molecular lines and a complex background that results from the plasma species, cathode material, operating environment and the major components of the sample matrix including their reaction products. Among the measured lines a number (depending on the oxidation state of the element in the matrix) of atomic and ionic lines were found to be free from spectral interference and with good signal-to-noise ratio, which indicates their potential for direct trace quantitative analysis utilizing a new technique: sliding spark spectroscopy. Mostly ionic lines are optically thin. In the UV range the lines are especially not broadened and are identifiable against a weak continuum.

Study on the Spectral Data Processing Method Based on the Transfer Function

Transfer function is a very important parameter to evaluate the system performance, and it is one of the key methods to process and analyze information. First, the feasibility of this method is analyzed by the theory simulation in this paper. Second, the median is selected to filter the noise in the spectral data by comparing median filtering and Db3 wavelet filtering results. And then, the transfer function method is used on the data processing that captured by a linear CCD spectrometer. The experimental results show that the spectral data processing method base on the transfer function given in this paper is reasonable. This method can further improve the accuracy and the resolution of the instrument, and can make it possible to get a wide application of the CCD spectrometer.

Evaluation of Sonochemiluminescence in a Phantom in the Presence of Protoporphyrin IX Conjugated to Nanoparticles

Introduction When a liquid is irradiated with high-intensity and low-frequency ultrasound, acoustic cavitation occurs and there are some methods to determine and quantify this phenomenon. The existing methods for performing these experiments include sonochemiluminescence (SCL) and chemical dosimetric methods. The particles in a liquid decrease the ultrasonic intensity threshold needed for cavitation onset. In this study, a new nanoconjugate made up of Protoporphyrin IX (PpIX) and gold nanoparticles (GNP), i.e., Au-PpIX was used to provide nucleation sites for cavitation. The nonradiative relaxation time of PpIX in the presence of GNPs is longer than the similar time for PpIX without GNPs. This effect can be used in medical diagnostic and therapeutic applications. Materials and Methods The acoustic cavitation activity was investigated studying integrated SCL signal in the wavelength range of 400-500 nm in polyacrylamide gel phantom containing luminol using a cooled CCD spectrometer at different intensities of 1 MHz ultrasound. In order to confirm these results, a chemical dosimetric method was utilized, too. Results SCL signal level in gel phantom containing Au-PpIX was higher than the other phantoms. These results have been confirmed by the chemical dosimetric data. Conclusion This finding can be related to the existence of PpIX as a sensitizer and GNPs as cavitation nuclei. In other words, nanoparticles have acted as the sites for cavitation and have increased the cavitation rate. Another theory is that activation of PpIX has produced more free radicals and has enhanced the SCL signal level.

A compact multi-channel fluorescence sensor with ambient light suppression

A multi-channel fluorescence sensor has been developed for process monitoring and fluorescence diagnostics. It comprises a fiber-optic set-up with an immersion probe and an intensity-modulated high power ultraviolet light-emitting diode as a light source for fluorescence excitation. By applying an electronic lock-in procedure, fluorescence signals are selectively detectable at ambient light levels of 1000 000 times higher intensity. The sensor was designed to be compact, low cost and easily adaptable to a wide field of application. The set-up was used to simultaneously monitor three important metabolic fluorophores: NAD(P)H, flavins and porphyrins during the cultivation of a baker's yeast. Moreover, the accumulation and degradation kinetics of protoporphyrin IX induced by 5-aminolevulinic acid on the skin could be recorded by the sensor. The detection limit for protoporphyrin IX was determined to be 4 × 10−11 mol L−1. The linear signal amplification of the sensor and time courses of fluorescence signals monitored during yeast fermentations were validated using a commercial CCD spectrometer. The robust and flexible set-up of the fiber-optic measurement system promises easy implementation of this non-invasive analytical tool to fluorescence monitoring and diagnostics in R&D and production.

Spectrophotometric high-precision seawater pH determination for use in underway measuring systems

Abstract. Autonomous sensors are required for a comprehensive documentation of the changes in the marine carbon system and thus to differentiate between its natural variability and anthropogenic impacts. Spectrophotometric determination of pH – a key variable of the seawater carbon system – is particularly suited to achieve precise and drift-free measurements. However, available spectrophotometric instruments are not suitable for integration into automated measurement systems (e.g. FerryBox) since they do not meet the major requirements of reliability, stability, robustness and moderate cost. Here we report on the development and testing of a~new indicator-based pH sensor that meets all of these requirements. This sensor can withstand the rough conditions during long-term deployments on ships of opportunity and is applicable to the open ocean as well as to coastal waters with a complex matrix and highly variable conditions. The sensor uses a high resolution CCD spectrometer as detector connected via optical fibers to a custom-made cuvette designed to reduce the impact of air bubbles. The sample temperature can be precisely adjusted (25 °C ± 0.006 °C) using computer-controlled power supplies and Peltier elements thus avoiding the widely used water bath. The overall setup achieves a measurement frequency of 1 min−1 with a precision of ±0.0007 pH units, an average offset of +0.0005 pH units to a reference system, and an offset of +0.0081 pH units to a certified standard buffer. Application of this sensor allows monitoring of seawater pH in autonomous underway systems, providing a key variable for characterization and understanding of the marine carbon system.

Incorporating Basic Optical Microscopy in the Instrumental Analysis Laboratory

A simple and versatile approach to incorporating basic optical microscopy in the undergraduate instrumental analysis laboratory is described. Attaching a miniature CCD spectrometer to the video port of a standard compound microscope yields a visible microspectrophotometer suitable for student investigations of fundamental spectrometry concepts, basic principles of optical microscopy, and some interesting phenomena unique to spectral measurements performed at the microscale. Results from several such investigations and ideas for additional applications are presented.

The development of the Space Environment Viability of Organics (SEVO) experiment aboard the Organism/Organic Exposure to Orbital Stresses (O/OREOS) satellite

The Space Environment Viability of Organics (SEVO) experiment is one of two scientific payloads aboard the triple-cube satellite Organism/ORganic Exposure to Orbital Stresses (O/OREOS). O/OREOS is the first technology demonstration mission of the NASA Astrobiology Small Payloads Program. The 1-kg, 1000-cm3 SEVO cube is investigating the chemical evolution of organic materials in interstellar space and planetary environments by exposing organic molecules under controlled conditions directly to the low-Earth orbit (LEO) particle and electromagnetic radiation environment. O/OREOS was launched on November 19, 2010 into a 650-km, 72°-inclination orbit and has a nominal operational lifetime of six months. Four classes of organic compounds, namely an amino acid, a quinone, a polycyclic aromatic hydrocarbon (PAH), and a metallo-porphyrin are being studied. Initial reaction conditions were established by hermetically sealing the thin-film organic samples in self-contained micro-environments. Chemical changes in the samples caused by direct exposure to LEO radiation and by interactions with the irradiated microenvironments are monitored in situ by ultraviolet/visible/near-infrared (UV/VIS/NIR) absorption spectroscopy using a novel compact fixed-grating CCD spectrometer with the Sun as its light source. The goals of the O/OREOS mission include: (1) demonstrating key small satellite technologies that can enable future low-cost astrobiology experiments, (2) deploying a miniature UV/VIS/NIR spectrometer suitable for in-situ astrobiology and other scientific investigations, (3) testing the capability to establish a variety of experimental reaction conditions to enable the study of astrobiological processes on small satellites, and (4) measuring the chemical evolution of organic molecules in LEO under conditions that can be extrapolated to interstellar and planetary environments. In this paper, the science and technology development of the SEVO instrument payload and its measurements are described.

携帯型 CCD 分光器を用いたアルカリ長石の蛍光スペクトル

A portable CCD spectrometer was applied for the measurement of photoluminescence (PL) spectra of alkali feldspars. A calibration was carried out for the spectral sensibility of the system. PL spectra with different patterns were measured for the red and white PL of zoned alkali feldspars from the Tanakami granite pegmatites, Shiga Pref. The PL spectra of alkali feldspars principally consist of an intense emission band in red region and a weak emission band in blue-green region.