Infrared Spectra in the 1000-100 cm-1 Region Combined with 4000-3000 cm-1 Region to Evaluate the States of Water.

In this study, we evaluated the state of water by performing infrared (IR) spectroscopic analysis in the 4000-100 cm-1 region. The effects of ions on the structure of water molecules were investigated by analyzing specific IR bands of salt solutions in the 1000-100 cm-1 region. Chloride solutions of Li, Na, K, Cs, Ba, and Ca were prepared at different concentrations, and their IR spectra were recorded by the attenuated total reflection method. The isosbestic point was observed in the 1000-100 cm-1 region, and the position was related to the ratio of the Stokes radius and effective ionic radius of each ion. Two bands were identified at around 660 and 400 cm-1 by curve fitting, and the intensity ratio increased linearly with a decrease in water activity. Thus, this demonstrates the potential of the 1000-100 cm-1 region as a marker for the evaluation of water structure subjected to ions. Moreover, it is possible to evaluate different states of water simultaneously by combining this with the band in the 4000-3000 cm-1 region. These results successfully demonstrate the effectiveness of the spectra in the 1000-100 cm-1 region to evaluate the state of water in ionic solutions.

Quantification of Starch Order in Physically Modified Rice Flours Using Small-Angle X-ray Scattering (SAXS) and Fourier Transform Infrared (FT-IR) Spectroscopy.

The purpose of this study was to understand the ordered structure of starch in rice flour based on a physical modification with non-heating, milling, and water sorption through the structural evaluation of rice flour using small-angle X-ray scattering (SAXS) and infrared spectroscopy within the 4000-100 cm-1 region. The SAXS pattern of the samples with low moisture contents subjected to milling yield a band within the 0.4-0.9 nm-1 of the q range owing to a lamellar repeat of starch with an ordered structure in rice flour. We proposed an order parameter using the intensity of the SAXS band to quantify the order structure of starch in rice flour, and the true density was negatively correlated with the order parameter. Infrared band at 990 cm-1 in COH bending mode applied to the hydroxyl group of C6 shifted to a low wavenumber corresponding to the order parameter. A linear correlation was found between the order parameter and the 990 cm-1 and band at 861 cm-1 owing to COC symmetrical stretching of glycoside bond and CH2 deformation of the glucose unit of starch, 572, 472, and 436 cm-1, owing to the pyranose ring in the glucose unit of starch. The identified infrared bands are effective for quantifying the ordered structure of starch at the lamellar level. When subjected to water sorption, the band position at 990 cm-1 shifted to a higher wavenumber above a water activity of 0.7. This result revealed that the water-induced transition of glass to rubber of starch in rice flour can be clearly evaluated through infrared spectroscopy using the band at 990 cm-1. In addition, the band at 861 cm-1 also shifted to a higher wavenumber, whereas those at 572 and 436 cm-1 did not show a significant shift. These results indicate that water sorption slightly affects the internal structure and may mainly affect the surface of starch.

Evaluation of solid state of rice flours produced by different milling processes using ATR-FTIR spectroscopy.

This study evaluated the influence of the milling process on solid state of rice flours according to water activity using ATR-FTIR. A band at 1740 cm-1 attributed to the C=O stretching of lipids was detected for crystalline samples, and it disappeared at a high aw range. The CH band at 2930 cm-1 of crystalline samples gradually shifted to a higher wavenumber with aw. This band of the α-formed and wet-milled samples shifted to higher wavenumbers above 0.8aw. A band due to OH stretching mode in the 3500-3000 cm-1 region did not shift with aw. The result obtained from IR spectra suggests that the parameter K calculated by Guggenheim-Anderson-de Boar model reflected not only the interaction between water molecules but also the changes of state in solids. Consequently, the results from this study provide insights about the adsorption properties of nonideal solids such as rice flour.

Phenomenological analysis on whipping behavior of rice flour batter.

In this study, the bubbles in rice flour batter were investigated under a constant temperature, because the bubble size distribution is important for the control of food texture. We obtained experimental data using a hand mixer and compared the properties of doughs prepared using six rice flours; each flour was prepared through a different milling process. We also added the size effect of the rice flour particles as the Bond number. Furthermore, we performed a dynamic wettability test to estimate the wettability of the rice flour surface. The results of this test were described well by the Washburn equation, and dc cosθ/dp was calculated as a wettability parameter (where, dc = effective diameter of a capillary in a powder bed, cosθ = the contact angle, dp = mean particle diameter of rice flour). If bubble sizes depend mainly on the inertial force, viscous force, surface tension, and gravity, then the normalized mean bubble diameter should be a function of the Reynolds number, Weber number, and Froude number. The mean bubble diameter (dbm ) generated by whipping was expected to be affected by the thickness (d) of the rod of the mixer, its movement speed, and physical properties of the material. Therefore, dimensionless mean diameter (dbm /d) was expressed based on a dimensionless equation. In the three-phase dispersion, different empirical equations were obtained depending on the amount of rice flour added, and the bubble diameter could be predicted using dimensionless parameters. In addition, the equations were generally applicable to the various materials selected for this study. PRACTICAL APPLICATION: The powder properties of rice flour were investigated, and dimensionless parameters were analyzed to construct an appropriate process control system for rice flour-based food products. Although the process method optimized for flour products is also used for rice flour products in practical situations, the comprehensive evaluation based on dimensionless parameters leads to optimization of the process for rice-flour based products. Moreover, this optimization might strongly support the creation of a new texture, and thus, the potential for market expansion of rice-flour based products is considerable.

Low-Frequency Vibrational Modes of Nylon 6 Studied by Using Infrared and Raman Spectroscopies and Density Functional Theory Calculations.

Far-infrared (FIR) and low-frequency Raman bands in the 90?400 cm?1 region of crystalline nylon 6 in ? form were assigned based on comparisons of experimental spectra and quantum mechanical calculations. A fragment methodology was applied in the calculations for explicit consideration of interchain interactions and crystal symmetry. The main features in both Raman and FIR spectra were reproduced well, which enabled the band assignments based on density functional theory and the significant improvement of the conventional assignments for which there had been a big dispute. Temperature dependence of the experimental FIR spectra has revealed that both bands at 222 and 111 cm?1 are characteristic of the ?-form structure. Their intensities linearly decreased with increasing temperature with marked two transition points, which correspond to glass and Brill transitions. Both bands can be indicators of the lattice length of ?-form nylon 6. On the basis of the calculations, the FIR and Raman bands at ?100 cm?1 were successfully assigned to methylene torsion and transverse motion of amide groups in which NH and O atoms move out of the amide plane. Decomposition of the calculated spectra revealed that the intensities at ?100 cm?1 in both spectra mainly originate from the amide groups and only secondarily from the methylene groups. Moreover, the FIR intensities at ?100 cm?1 were nearly perfectly governed by the amide groups, which could be a reason why this FIR band is particularly sensitive to hydrogen bonds among the low-frequency bands. The FIR band at 222 cm?1 was assigned to methylene torsion and transverse motion of NH groups. Both FIR bands at 222 and 111 cm?1 contain perpendicular motions of methylene and amide groups. This will be a reason for their sensitivity to interchain interactions in ?-form nylon 6. Contrarily, the FIR band at 294 cm?1 is in parallel polarization to the chain direction and assigned to a deformation of C?CH2?CH2 and bending motion of C?O in the amide plane. This is the reason why this band is not sensitive to the structural transitions of nylon 6. Our previous works revealed that in regions of 125 and 70 cm?1, there are specific vibrational peaks of crystalline polyesters primarily arising from out-of-plane motion of ester groups. We can find a similarity in 125 and 70 cm?1 regions between crystalline polyesters and nylon 6 that both polymers show specific out-of-plane vibrational peaks around 100 cm?1, which are sensitive to the lattice length among polymer chains.

An Application for the Quantitative Analysis of Pharmaceutical Tablets Using a Rapid Switching System Between a Near-Infrared Spectrometer and a Portable Near-Infrared Imaging System Equipped with Fiber Optics.

We present a rapid switching system between a newly developed near-infrared (NIR) spectrometer and its imaging system to select the spot size of a diffuse reflectance (DR) probe. In a previous study, we developed a portable NIR imaging system, known as D-NIRs, which has significant advantages over other systems. Its high speed, high spectral resolution, and portability are particularly useful in the process of monitoring pharmaceutical tablets. However, the spectral accuracies relating to the changes in the formulation of the pharmaceutical tablets have not been fully discussed. Therefore, we improved the rapid optical switching system and present a new model of D-NIRs (ND-NIRs) here. This system can automatically switch the optical paths of the DR and NIR imaging probes, greatly contributing to the simultaneous measurement of both the imaging and spot. The NIR spectra of the model tablets, including 0-10% ascorbic acid, were measured and simultaneous NIR images of the tablets were obtained. The predicted results using spot sizes for the DR probe of 1 and 5 mm diameter, resulted in concentrations of R2 = 0.79 and 0.94, with root mean square errors (RMSE) of 1.78 and 0.89, respectively. For tablets with a high concentration of ascorbic acid, the NIR imaging results showed inhomogeneity in concentration. However, the predicted values for the low concentration samples appeared higher than the known concentration of the tablets, although the homogeneity of the concentration was confirmed. In addition, the optimal spot size using NIR imaging data was estimated to be 5-7 mm. The results obtained in this study show that the spot size of the fiber probe, attached to a spectrometer, is important in developing a highly reliable model to determine the component concentration of a tablet.

Study on the Change in Powder Properties of Rice Flour by Different Milling Processes.

The aim of this study was to clarify the change in the powder properties of rice flour depending on the milling process. Rice flour samples, which have gradual mechanical shock properties, were prepared using different milling methods. Furthermore, the correlation between the starch damage, owing to mechanical shock, and powder properties of rice flour was investigated. The particle size was changed gradually through each milling process; however, the change did not clearly correlate with starch damage. The results of the X-ray diffraction (XRD) pattern of nongelatinized samples showed the typical A-type structure of starch. The crystal structure of starch in rice flour may change to a disorder state with the progress of milling; thus, in this study, instead of crystallinity, we considered the disorder index (DI) calculated from the XRD intensity of samples. Relationship between DI and starch damage was confirmed with R 2 = 0.923. Therefore, the mechanical shock caused by the milling process contributes to the crystal state of starch. The parameter q m calculated from the Guggenheim-Anderson-de Boer (GAB) equation of each sample corresponded to the DI. This result suggested that the sorption site of rice flour decreased, and a positive correlation was observed between the parameter K and DI. Thus, the interaction between the rice flour and water molecules weakened because of the mechanical shock. In addition, the use of a SEM image supports the insight that the change in parameter K may reflect the structural change in the solid phase. These results demonstrated that the change in powder properties of rice flour caused by mechanical shock of the milling could evaluate quantitatively.

Engineering analysis of the high-density heterotrophic cultivation of mung bean sprouts.

This study investigated the heterotrophic growth behavior of mung beans cultivated in an individual bed under water supply. The fresh weight of mung beans in the bed was estimated, and changes in temperature, and oxygen and carbon dioxide concentrations were recorded during the cultivation period. The specific growth rate, oxygen uptake rate, and carbon dioxide evolution rate, based on the fresh weight in the bed, were calculated. Growth under heterotrophic cultivation can be classified into the following three stages. Reductions in specific oxygen uptake rate, specific carbon dioxide evolution rate, and specific energy production rate corresponded to that of specific growth rate. Indicators of biological activity related to oxygen and carbon dioxide were evaluated quantitatively for beds under high-density heterotrophic cultivation. Moreover, the results obtained from this study successfully demonstrate that there is a relationship between the growth of mung beans and indicators of biological activity.

Near-Infrared Spectroscopy and Imaging Studies of Fertilized Fish Eggs: In Vivo Monitoring of Egg Growth at the Molecular Level.

In this work, the growth of fertilized Japanese medaka (Oryzias latipes) eggs was monitored in vivo at the molecular level using near-infrared (NIR) spectroscopy and NIR imaging. NIR spectra were recorded noninvasively for three major parts of a fertilized medaka egg, the embryonic body, the oil droplets, and the yolk, from the first day after fertilization to the day before hatching. Principal component analysis (PCA) revealed that water, protein, and lipid contents in the egg yolk and oil droplets changed significantly just before hatching. The ratio of the characteristic peaks due to proteins and lipids in the second derivative spectra suggested that the relative concentration of proteins to lipids was constant in the egg yolk, while it dramatically increased just before hatching in the oil droplets. Furthermore, linear discriminant analysis (LDA) predicted the hatching possibility on the next day with 100% and 99.3% accuracy for yolk and oil droplets data, respectively. Two types of NIR images were developed in situ using the band intensities of the lipids and proteins in the second derivative spectra. The egg's protein and lipid content was successfully visualized noninvasively. This technique should enable noninvasive quality testing of fertilized eggs in the future.

Imaging of Hydrophilicity and its Inhomogeneity on a Titanium Dioxide Film Exposed to Ultraviolet Irradiation Using a Newly Developed Near-Infrared Camera.

This study has investigated hydrophilicity changes and their inhomogeneity of TiO2 films on Pyrex glasses by near-infrared (NIR) spectral imaging. Near-infrared spectra of TiO2 films in the 9000-4000 cm(-1) region were measured using a newly developed NIR camera named Compovision. A band in the 5400-4800 cm(-1) region, which is assigned to a combination (ν2 + ν3) mode of bending (ν2) and antisymmetric stretching (ν3) modes of the H2O molecule, was clearly identified and its intensity increased with time in the air. It is interesting that the increased rate rose with ultraviolet (UV) light irradiation (300-400 nm, 1 mW cm(-2)) compared to without UV light irradiation. This result suggested that the hydrophilicity of TiO2 was enhanced about twice upon the UV light irradiation. Moreover, the NIR images clarified spatial distributions of the hydrophilicity on the TiO2 surface with a significantly wide area (20 × 40 mm) and a high speed (within 5 s for one image). This rapid imaging system enabled us to detect the hydrophilicity change during only 1 min. The potential of this camera is quite superior, not only for basic research, but also for diverse industrial applications.

Baseline Correction of Diffuse Reflection Near-Infrared Spectra Using Searching Region Standard Normal Variate (SRSNV).

An alternative baseline correction method for diffuse reflection near-infrared (NIR) spectra, searching region standard normal variate (SRSNV), was proposed. Standard normal variate (SNV) is an effective pretreatment method for baseline correction of diffuse reflection NIR spectra of powder and granular samples; however, its baseline correction performance depends on the NIR region used for SNV calculation. To search for an optimal NIR region for baseline correction using SNV, SRSNV employs moving window partial least squares regression (MWPLSR), and an optimal NIR region is identified based on the root mean square error (RMSE) of cross-validation of the partial least squares regression (PLSR) models with the first latent variable (LV). The performance of SRSNV was evaluated using diffuse reflection NIR spectra of mixture samples consisting of wheat flour and granular glucose (0-100% glucose at 5% intervals). From the obtained NIR spectra of the mixture in the 10 000-4000 cm(-1) region at 4 cm intervals (1501 spectral channels), a series of spectral windows consisting of 80 spectral channels was constructed, and then SNV spectra were calculated for each spectral window. Using these SNV spectra, a series of PLSR models with the first LV for glucose concentration was built. A plot of RMSE versus the spectral window position obtained using the PLSR models revealed that the 8680­8364 cm(-1) region was optimal for baseline correction using SNV. In the SNV spectra calculated using the 8680­8364 cm(-1) region (SRSNV spectra), a remarkable relative intensity change between a band due to wheat flour at 8500 cm(-1) and that due to glucose at 8364 cm(-1) was observed owing to successful baseline correction using SNV. A PLSR model with the first LV based on the SRSNV spectra yielded a determination coefficient (R2) of 0.999 and an RMSE of 0.70%, while a PLSR model with three LVs based on SNV spectra calculated in the full spectral region gave an R2 of 0.995 and an RMSE of 2.29%. Additional evaluation of SRSNV was carried out using diffuse reflection NIR spectra of marzipan and corn samples, and PLSR models based on SRSNV spectra showed good prediction results. These evaluation results indicate that SRSNV is effective in baseline correction of diffuse reflection NIR spectra and provides regression models with good prediction accuracy.

Near-Infrared Imaging Using a High-Speed Monitoring Near Infrared Hyperspectral Camera (Compovision).

This review paper reports near-infrared (NIR) imaging studies using a newly-developed NIR camera, Compovision. Compovision can measure a significantly wide area of 150 mmX 250 mm at high speed of between 2 and 5 s. It enables a wide spectral region measurement in the 1,000-2,350 nm range at 6 nm intervals. We investigated the potential of Compovision in the applications to industrial problems such as the evaluation of pharmaceutical tablets and polymers. Our studies have demonstrated that NIR imaging based on Compovision can solve several issues such as long acquisition times and relatively low sensitivity of detection. NIR imaging with Compovision is strongly expected to be applied not only to pharmaceutical tablet monitoring and polymer characterization but also to various applications such as those to food products, biomedical substances and organic and inorganic materials.

Moving-window two-dimensional heterospectral (MW2DHetero) correlation analysis and its application for the process monitoring of alcoholic fermentation.

The technique of moving-window two-dimensional heterospectral (MW2DHetero) correlation spectroscopy is proposed. This computational method is based on the ideas of perturbation-correlation moving-window two-dimensional (PCMW2D) correlation spectroscopy and two-dimensional heterospectral correlation analysis. Not only small spectral variations, but also detailed bands assignments were captured using the analysis. This method was applied to near-infrared (NIR) spectra in the 10 000-4000 cm(-1) region and mid-infrared (mid-IR) spectra in the 5000-1200 cm(-1) region, which were simultaneously detected using a dual-region spectrometer. Near-infrared and mid-IR spectra collected during an alcoholic fermentation process using a solution containing glucose and fructose were reported. Slight time differences for the consumption of sugars compared with the production of ethanol were found between 50 and 150 min. It was concluded that these slight time differences are evidence for different consumption times between glucose and fructose during the fermentation process. The result proved a possibility of the selective monitoring of the simultaneous reaction processes between productive and consumptive components.

Image monitoring of pharmaceutical blending processes and the determination of an end point by using a portable near-infrared imaging device based on a polychromator-type near-infrared spectrometer with a high-speed and high-resolution photo diode array detector.

In the present study we have developed a new version (ND-NIRs) of a polychromator-type near-infrared (NIR) spectrometer with a high-resolution photo diode array detector, which we built before (D-NIRs). The new version has four 5 W halogen lamps compared with the three lamps for the older version. The new version also has a condenser lens with a shorter focal point length. The increase in the number of the lamps and the shortening of the focal point of the condenser lens realize high signal-to-noise ratio and high-speed NIR imaging measurement. By using the ND-NIRs we carried out the in-line monitoring of pharmaceutical blending and determined an end point of the blending process. Moreover, to determinate a more accurate end point, a NIR image of the blending sample was acquired by means of a portable NIR imaging device based on ND-NIRs. The imaging result has demonstrated that the mixing time of 8 min is enough for homogeneous mixing. In this way the present study has demonstrated that ND-NIRs and the imaging system based on a ND-NIRs hold considerable promise for process analysis.

High-speed monitoring of the crystallinity change in poly(lactic acid) during photodegradation by using a newly developed wide area NIR imaging system (Compovision).

We aimed to achieve wide area rapid monitoring of the crystallinity change in poly(lactic acid) (PLA) during photodegradation caused by ultraviolet (UV) light by using a newly developed near-infrared (NIR) camera (Compovison). Several kinds of PLA samples with different crystallinities and their blends with poly[(3)-(R)-hydroxybutyrate] were prepared. Their two-dimensional NIR spectra in the 1,000-2,350-nm region were measured by Compovision at a 5-min interval during photolysis. An intensity decrease of the band in the 1,900-1,925-nm region due to the second overtone of the C = O stretching vibration of PLA was observed during photolysis. This suggests that an anhydride carbonyl is produced during photolysis. The NIR image of the crystallinity change monitored by the band at 1,917 nm in the standard normal variate spectra clearly shows the inhomogeneity of crystal evolution. A logarithmic increase was observed for all identified areas in the PLA film; however, the time to reach the maximum crystallinity was slightly different according to the initial crystallinity of the sample. It is likely that the initial crystallinity of the sample influences the degradation speed more than the degradation amount. These imaging results have provided fundamental chemical insights into the photolytic process for PLA, and at the same time they have demonstrated that the two-dimensional spectral data obtained by Compovision are useful for process monitoring of polymers.

Thermal behavior of poly(lactic acid)-nanocomposite studied by near-infrared imaging based on roundtrip temperature scan.

The thermal behavior of poly(lactic acid) (PLA) was studied by near-infrared imaging to provide a molecular-level understanding of the physical improvement caused by nanoclay dispersion. A set of PLA samples, each having different nanoclay dispersion, was prepared under varying sonication time. Crystallinity variation of the polymer interacting with the nanoclay particles was analyzed by a roundtrip temperature scan below the melting temperature. Namely, the samples underwent heating and then cooling in the opposite way during the spectral measurement. The discrepancy of the spectral feature between the heating and the cooling indicated the development of the hysteresis associated with the cold crystallization of the PLA lamellae. The generation of the spectral residuals revealed the inner working mechanism of how the polymer structure undergoes variation depending on the presence of the clay particles and their dispersions. The sonication brings substantial dispersion of the nanoclay over the polymer matrix. The nanoclay particles then induce the additional development of the crystalline structure due to the molecular interaction between the PLA and nanoclay arising from the presence of enormous surface area, which in turn induces variation of mechanical strength to the polymer.

Recent progress of near-infrared (NIR) imaging--development of novel instruments and their applicability for practical situations--.

The purpose of this review article is to outline the recent progress in near-infrared (NIR) imaging technology with particular emphasis on new instrumentation. Superior features of NIR imaging such as suitability for nondestructive and in-situ analysis, transmission ability, availability of optical fibers, high-speed monitoring and stability are very attractive not only for laboratory-based studies but also for diverse practical applications. In this review, introduction to chemical imaging is described, and then, a comparison among NIR, infrared (IR) and Raman imaging are made. Furthermore, the features of new NIR imaging instruments developed by our research group in collaboration with Yokogawa Electric Corporation and Sumitomo Electric Industries, Ltd. are discussed. Finally, some examples of applications of NIR imaging are introduced. Particularly, the performance and usefulness of the newly-developed imaging devices are demonstrated through their applications to pharmaceutical tablets and polymers.

Potential of a newly developed high-speed near-infrared (NIR) camera (Compovision) in polymer industrial analyses: monitoring crystallinity and crystal evolution of polylactic acid (PLA) and concentration of PLA in PLA/Poly-(R)-3-hydroxybutyrate (PHB) blends.

This study was carried out to evaluate a new high-speed hyperspectral near-infrared (NIR) camera named Compovision. Quantitative analyses of the crystallinity and crystal evolution of biodegradable polymer, polylactic acid (PLA), and its concentration in PLA/poly-(R)-3-hydroxybutyrate (PHB) blends were investigated using near-infrared (NIR) imaging. This NIR camera can measure two-dimensional NIR spectral data in the 1000-2350 nm region obtaining images with wide field of view of 150 × 250 mm(2) (approximately 100 000 pixels) at high speeds (in less than 5 s). PLA with differing crystallinities between 0 and 50% blended samples with PHB in ratios of 80/20, 60/40, 40/60, 20/80, and pure films of 100% PLA and PHB were prepared. Compovision was used to collect respective NIR spectra in the 1000-2350 nm region and investigate the crystallinity of PLA and its concentration in the blends. The partial least squares (PLS) regression models for the crystallinity of PLA were developed using absorbance, second derivative, and standard normal variate (SNV) spectra from the most informative region of the spectra, between 1600 and 2000 nm. The predicted results of PLS models achieved using the absorbance and second derivative spectra were fairly good with a root mean square error (RMSE) of less than 6.1% and a determination of coefficient (R(2)) of more than 0.88 for PLS factor 1. The results obtained using the SNV spectra yielded the best prediction with the smallest RMSE of 2.93% and the highest R(2) of 0.976. Moreover, PLS models developed for estimating the concentration of PLA in the blend polymers using SNV spectra gave good predicted results where the RMSE was 4.94% and R(2) was 0.98. The SNV-based models provided the best-predicted results, since it can reduce the effects of the spectral changes induced by the inhomogeneity and the thickness of the samples. Wide area crystal evolution of PLA on a plate where a temperature slope of 70-105 °C had occurred was also monitored using NIR imaging. An SNV-based image gave an obvious contrast of the crystallinity around the crystal growth area according to slight temperature change. Moreover, it clarified the inhomogeneity of crystal evolution over the significant wide area. These results have proved that the newly developed hyperspectral NIR camera, Compovision, can be successfully used to study polymers for industrial processes, such as monitoring the crystallinity of PLA and the different composition of PLA/PHB blends.

Application of a newly developed portable NIR imaging device to monitor the dissolution process of tablets.

We have recently developed a novel portable NIR imaging device (D-NIRs), which has a high speed and high wavelength resolution. This NIR imaging approach has been developed by utilizing D-NIRs for studying the dissolution of a model tablet containing 20 % ascorbic acid (AsA) as an active pharmaceutical ingredient and 80 % hydroxypropyl methylcellulose, where the tablet is sealed by a special cell. Diffuse reflectance NIR spectra in the 1,000 to 1,600 nm region were measured during the dissolution of the tablet. A unique band at around 1,361 nm of AsA was identified by the second derivative spectra of tablet and used for AsA distribution NIR imaging. Two-dimensional change of AsA concentration of the tablet due to water penetration is clearly shown by using the band-based image at 1,361 nm in NIR spectra obtained with high speed. Moreover, it is significantly enhanced by using the intensity ratio of two bands at 1,361 and 1,354 nm corresponding to AsA and water absorption, respectively, showing the dissolution process. The imaging results suggest that the amount of AsA in the imaged area decreases with increasing water penetration. The proposed NIR imaging approach using the intensity of a specific band or the ratio of two bands combined with the developed portable NIR imaging instrument, is a potentially useful practical way to evaluate the tablet at every moment during dissolution and to monitor the concentration distribution of each drug component in the tablet.

A polychromator-type near-infrared spectrometer with a high-sensitivity and high-resolution photodiode array detector for pharmaceutical process monitoring on the millisecond time scale.

In the fine chemicals industry, particularly in the pharmaceutical industry, advanced sensing technologies have recently begun being incorporated into the process line in order to improve safety and quality in accordance with process analytical technology. For estimating the quality of powders without preparation during drug formulation, near-infrared (NIR) spectroscopy has been considered the most promising sensing approach. In this study, we have developed a compact polychromator-type NIR spectrometer equipped with a photodiode (PD) array detector. This detector is consisting of 640 InGaAs-PD elements with 20-µm pitch. Some high-specification spectrometers, which use InGaAs-PD with 512 elements, have a wavelength resolution of about 1.56 nm when covering 900-1700 nm range. On the other hand, the newly developed detector, having the PD with one of the world's highest density, enables wavelength resolution of below 1.25 nm. Moreover, thanks to the combination with a highly integrated charge amplifier array circuit, measurement speed of the detector is higher by two orders than that of existing PD array detectors. The developed spectrometer is small (120 mm × 220 mm × 200 mm) and light (6 kg), and it contains various key devices including the high-density and high-sensitivity PD array detector, NIR technology, and spectroscopy technology for a spectroscopic analyzer that has the required detection mechanism and high sensitivity for powder measurement, as well as a high-speed measuring function for blenders. Moreover, we have evaluated the characteristics of the developed NIR spectrometer, and the measurement of powder samples confirmed that it has high functionality.