3/31/09
Tunable thermal emission at infrared frequencies via tungsten gratings
The author investigates the manipulation of thermal emission by using one-dimensional tungsten gratings with different groove depths. It is found that, by systematically increasing the depth of the groove, the linearly polarized emission at particular frequencies can be substantially enhanced to achieve that of the blackbody radiation limit, whereas the emission in other frequency ranges shows no noticeable changes. The results can provide useful insights into the design of thermovoltaic applications.
3/30/09
Potential used of near infrared reflectance spectroscopy to predict meat physico-chemical composition of guinea fowl (Numida meleagris) reared under
Potential used of near infrarednext term reflectance spectroscopy to predict meat physico-chemical composition of guinea fowl (Numida meleagris) reared under different production systems
previous termNear infrarednext term reflectance spectroscopy (NIRS) was evaluated as a tool to predict the physico-chemical composition of samples of Guinea fowl (Numida meleagris) breast and thigh meat. Two different production systems were studied (confinement versus free-range) using 60 animals. The breast and thigh pieces were extracted from the carcass of each animal and analysed according to the official reference methods to determine the content in ash, fat, protein, WHC (water holding capacity), and DM (dry matter). All the samples were scanned to obtain their previous termnear infrarednext term reflectance spectrum, using a 19-filter device that reads in the wavelength range of 1445–2348 nm. Multiple linear correlation (MLR) was used as a statistical model to predict the physico-chemical composition. The best prediction equations were obtained for the fat and protein calibrations, with SEc = 0.310 and View the MathML source for fat, and SEc = 0.640 and View the MathML source for protein. The validation of the equations was also good for fat and protein (SEvc = 0.2179 and 1-variance ratio (VR) = 0.8342, SEvc = 1.9609 and 1-VR = 0.7609, respectively). The worst prediction equations were for the WHC and ash content, with SEc = 1.49, View the MathML source, SEvc = 4.1711, 1-VR = 0.392, and SEc = 0.030, View the MathML source, SEvc = 0.3421, 1-VR = 0.4631, respectively.
previous termNear infrarednext term reflectance spectroscopy (NIRS) was evaluated as a tool to predict the physico-chemical composition of samples of Guinea fowl (Numida meleagris) breast and thigh meat. Two different production systems were studied (confinement versus free-range) using 60 animals. The breast and thigh pieces were extracted from the carcass of each animal and analysed according to the official reference methods to determine the content in ash, fat, protein, WHC (water holding capacity), and DM (dry matter). All the samples were scanned to obtain their previous termnear infrarednext term reflectance spectrum, using a 19-filter device that reads in the wavelength range of 1445–2348 nm. Multiple linear correlation (MLR) was used as a statistical model to predict the physico-chemical composition. The best prediction equations were obtained for the fat and protein calibrations, with SEc = 0.310 and View the MathML source for fat, and SEc = 0.640 and View the MathML source for protein. The validation of the equations was also good for fat and protein (SEvc = 0.2179 and 1-variance ratio (VR) = 0.8342, SEvc = 1.9609 and 1-VR = 0.7609, respectively). The worst prediction equations were for the WHC and ash content, with SEc = 1.49, View the MathML source, SEvc = 4.1711, 1-VR = 0.392, and SEc = 0.030, View the MathML source, SEvc = 0.3421, 1-VR = 0.4631, respectively.
3/29/09
Innovative surface characterization techniques applied to immunosensor elaboration and test: Comparing the efficiency of Fourier transform–surface
Innovative surface characterization techniques applied to immunosensor elaboration and test: Comparing the efficiency of Fourier transform–surface plasmon resonance, quartz crystal microbalance with dissipation measurements, and polarization modulation–reflection absorption infrarednext term spectroscopy
Three sensitive and original transduction techniques have been used to monitor the immobilization of anti-rabbit immunoglobulins (anti-rIgGs) and the detection of rIgGs on gold transducers. Polarization modulation–reflection absorption previous terminfrarednext term spectroscopy (PM–RAIRS), quartz crystal microbalance with dissipation measurements (QCM–D), and Fourier transform–surface plasmon resonance (FT–SPR) were combined to achieve the best sensitivity and a large dynamic range in the target detection step. Their performances were compared after having checked that the layers adsorbed on the three different gold substrates were identical. The studied immunosensors were elaborated by building a thiolamine layer on gold surface, followed by its derivatization by glutaraldehyde and covalent binding of a monoclonal secondary IgG. The antibody attachment step was monitored in a wide range of concentrations (1–50 μg/ml). Then the built immunosensors were used to detect the rIgG recognition. PM–RAIRS analyses, performed under air, supplied ex situ data, whereas FT–SPR and QCM techniques were used in situ, enabling on-line detection of recognition processes. Interestingly, the three techniques suggested that the antibody coverage gets saturated for approximately 20 μg/ml in solution. In the very low concentration range (1 μg/ml), antibody binding was detected by the three techniques, but FT–SPR leads to an intense signal with a wavenumber shift of approximately 30 cm−1; one may expect, by FT–SPR, a detection limit of the order of a few tenths of μg/ml. Ongoing experiments aim at determining the limit of detection and dynamic range of the very promising FT–SPR technique.
Three sensitive and original transduction techniques have been used to monitor the immobilization of anti-rabbit immunoglobulins (anti-rIgGs) and the detection of rIgGs on gold transducers. Polarization modulation–reflection absorption previous terminfrarednext term spectroscopy (PM–RAIRS), quartz crystal microbalance with dissipation measurements (QCM–D), and Fourier transform–surface plasmon resonance (FT–SPR) were combined to achieve the best sensitivity and a large dynamic range in the target detection step. Their performances were compared after having checked that the layers adsorbed on the three different gold substrates were identical. The studied immunosensors were elaborated by building a thiolamine layer on gold surface, followed by its derivatization by glutaraldehyde and covalent binding of a monoclonal secondary IgG. The antibody attachment step was monitored in a wide range of concentrations (1–50 μg/ml). Then the built immunosensors were used to detect the rIgG recognition. PM–RAIRS analyses, performed under air, supplied ex situ data, whereas FT–SPR and QCM techniques were used in situ, enabling on-line detection of recognition processes. Interestingly, the three techniques suggested that the antibody coverage gets saturated for approximately 20 μg/ml in solution. In the very low concentration range (1 μg/ml), antibody binding was detected by the three techniques, but FT–SPR leads to an intense signal with a wavenumber shift of approximately 30 cm−1; one may expect, by FT–SPR, a detection limit of the order of a few tenths of μg/ml. Ongoing experiments aim at determining the limit of detection and dynamic range of the very promising FT–SPR technique.
3/28/09
Temperature dependence of infrared emissivity properties of (La0.8Sr0.2)1−xMnO3
Non-stoichiometric compounds of (La0.8Sr0.2)1−xMnO3 (0.1 ≤ x ≤ 0.4) were prepared by standard solid-state reaction method. The structure, 
infrared
absorption and normal emissivity (
N) properties of the compounds were systematically investigated. The X-ray powder diffraction (XRD) results indicate that the structure of the samples is distorted rhombohedral but not cubic. The mechanism of new infrared absorption occurring around 719–922 cm−1 is proposed. The N of the samples in the 8–14 μm waveband increases with increasing temperature and changes significantly in the temperature range 288–313 K due to the metal-insulator transition. Moreover, the N value for x = 0.2 is higher than that for the other samples, owing to two strong infrared absorption peaks at 719 cm−1 and 856 cm−1. The N has no drastic change with increasing temperature in the 3–5 μm waveband.
infrared absorption and normal emissivity (N) properties of the compounds were systematically investigated. The X-ray powder diffraction (XRD) results indicate that the structure of the samples is distorted rhombohedral but not cubic. The mechanism of new infrared absorption occurring around 719–922 cm−1 is proposed. The N of the samples in the 8–14 μm waveband increases with increasing temperature and changes significantly in the temperature range 288–313 K due to the metal-insulator transition. Moreover, the N value for x = 0.2 is higher than that for the other samples, owing to two strong infrared absorption peaks at 719 cm−1 and 856 cm−1. The N has no drastic change with increasing temperature in the 3–5 μm waveband.
3/27/09
Fluorinated squaraine as near-IR label with improved properties for the labeling of oligonucleotides
A new squaraine dye with fluorinated benzothiazole rings was synthesized. This new label possesses improved photophysical properties and chemical stability as compared to the corresponding non-fluorinated and the dicyanosquaraines. These squaraines were used for the labeling of a series of oligonucleotides with various sequences, lengths, and chemistries. The conjugates involving the fluorinated squaraine possess the best properties: emission wavelength >670 nm, high quantum yields (0.27–0.39).
3/26/09
Influence of surface groups of proteins on water studied by freezing/thawing hysteresis and infrared spectroscopy
The influence of proteins and solutes on hysteresis of freezing and melting of water was measured by infrared (IR) spectroscopy. Of the solutes examined, poly-l-arginine and flounder antifreeze protein produced the largest freezing point depression of water, with little effect on the melting temperature. Poly-l-lysine, poly-l-glutamate, cytochrome c and bovine serum albumin had less effect on the freezing of water. Small compounds used to mimic non-polar (trimethylamine N-oxide, methanol), positively charged (guanidinium chloride, NH4Cl, urea) and negatively charged (Na acetate) groups on protein surfaces were also examined. These molecules and ions depress water's freezing point and the melting profiles became broad. Since infrared absorption measures both bulk solvent and solvent bound to the solutes, this result is consistent with solutes interacting with liquid water. The amide I absorption bands of antifreeze protein and poly-l-arginine do not detectably change with the phase transition of water. An interpretation is that the antifreeze protein and poly-l-arginine order liquid water such that the water around the group is ice-like.
infrared (IR) spectroscopy. Of the solutes examined, poly-l-arginine and flounder antifreeze protein produced the largest freezing point depression of water, with little effect on the melting temperature. Poly-l-lysine, poly-l-glutamate, cytochrome c and bovine serum albumin had less effect on the freezing of water. Small compounds used to mimic non-polar (trimethylamine N-oxide, methanol), positively charged (guanidinium chloride, NH4Cl, urea) and negatively charged (Na acetate) groups on protein surfaces were also examined. These molecules and ions depress water's freezing point and the melting profiles became broad. Since infrared absorption measures both bulk solvent and solvent bound to the solutes, this result is consistent with solutes interacting with liquid water. The amide I absorption bands of antifreeze protein and poly-l-arginine do not detectably change with the phase transition of water. An interpretation is that the antifreeze protein and poly-l-arginine order liquid water such that the water around the group is ice-like.
3/25/09
Novel measurements of refractive index, density and mid-infrared integrated band strengths for solid O2, N2O and NO2:N2O4 mixtures
We present novel measurements of the refractive index, density and integrated band strengths of mid-infrared features of solid N2O at 16 K and of NO2 and N2O4 in two frozen NO2:N2O4 mixtures deposited at 16 and 60 K. The refractive index and density measurements were performed also for frozen O2 deposited at 16 K. In this case, the integrated band strength values could not be determined since O2 is a homonuclear molecule and therefore its fundamental mode is not infrared active. The solid samples were analysed by infrared spectroscopy in the 8000÷800 cm−1 range. The sample thickness was measured by the interference curve obtained using a He–Ne laser operating at 543 nm. The refractive index at this laser wavelength was obtained, by numerical methods, from the measured amplitude of the interference curve. The density values were obtained using the Lorentz–Lorenz relation. Integrated band strength values were then obtained by a linear fit of the integrated band intensities plotted versus column density values. The astrophysical relevance of these novel measurements is briefly discussed.
infrared features of solid N2O at 16 K and of NO2 and N2O4 in two frozen NO2:N2O4 mixtures deposited at 16 and 60 K. The refractive index and density measurements were performed also for frozen O2 deposited at 16 K. In this case, the integrated band strength values could not be determined since O2 is a homonuclear molecule and therefore its fundamental mode is not infrared active. The solid samples were analysed by infrared spectroscopy in the 8000÷800 cm−1 range. The sample thickness was measured by the interference curve obtained using a He–Ne laser operating at 543 nm. The refractive index at this laser wavelength was obtained, by numerical methods, from the measured amplitude of the interference curve. The density values were obtained using the Lorentz–Lorenz relation. Integrated band strength values were then obtained by a linear fit of the integrated band intensities plotted versus column density values. The astrophysical relevance of these novel measurements is briefly discussed.
3/24/09
Infrared and near-infrared spectroscopic study of synthetic hydrotalcites with variable divalent/trivalent cationic ratios
Near-infrared (NIR), X-ray diffraction (XRD) and infrared (IR) spectroscopy have been applied to hydrotalcites of the formula Mg6 (Fe,Al)2(OH)16(CO3)·4H2O formed by intercalation with the carbonate anion as a function of divalent/trivalent cationic ratio. Such hydrotalcites were found to show variation in the d-spacing attributed to the size of the cation. In the IR (1750–4000 cm−1), the position of all bands except those at approximately 3060 cm−1 shift to higher wavenumbers as the cation ratio increases. Conversely, at wavenumbers below 1000 cm−1, the bands shift to lower wavenumbers as the cation ratio increases. A water bending mode at higher wavenumbers was also observed which indicates that the water is strongly hydrogen bonded. In the NIR spectrum between 8000 and 12,000 cm−1, there is a broad feature which is attributed to electronic bands of the ferrous ion and low intensity sharp bands due to overtones of the OH stretching vibrations. It is also apparent from this region that Fe2+ substitutes for Mg2+. The intensity of bands at 7750 and 5200 cm−1 increases as the cation ratio increases in the NIR spectrum. Hydrotalcites with a magnesium amount 3 and 4 times greater than that of aluminium and iron combined, in the lower wavenumber region of the NIR spectrum, have very similar spectral profiles. This work has shown that hydrotalcites with different divalent/trivalent ratios can be synthesised and characterised by infrared spectroscopy.
3/23/09
Pulsed infrared radiation transmission through hollow silica waveguides
Transmission measurements of Q-switched and free-running Er:YAG laser radiation, at 2.94 μm and free-running Ho:YAG laser radiation, at 2.06 μm, through hollow silica waveguides of 750 and 1000 μm core diameter were performed. Attenuation measurements were obtained as a function of the laser energy input and as a function of the bending curvature. The output beam quality was also studied as a function of the focal length of the coupling lens and the overall launching conditions for straight waveguides using the appropriate beam profiler.
3/22/09
The application of near infrared spectroscopy technology and a remote reflectance fibre-optic probe for the determination of peptides in cheeses (cow’
The use of near infrared spectroscopy (NIRS) technology employing a remote reflectance fibre-optic probe (with a 5 cm × 5 cm quartz window) for the analysis of the hydrophilic (HI) and hydrophobic (HO) peptides and the ratio HO/HI was assayed. To do so, cheeses with known and varying percentages of cow’s, ewe’s and goat’s milk were elaborated (112 samples). Ripening controls were performed over 6 months, and the chemical data obtained by reversed-phase high performance liquid chromatography used as reference. The regression method employed was modified partial least squares (MPLS). The multiple correlation coefficients (RSQ) and prediction corrected standard errors (SEP (C)) obtained 0.879 and 1.83% for hydrophilic (HI) and 0.879 and 1.83% for hydrophobic (HO) peptides, respectively, and 0.890 and 0.03% for the ratio HO/HI. The method allows immediate control by direct application of the fibre-optic probe to the cheese without prior sample treatment or destruction.
near infrared spectroscopy (NIRS) technology employing a remote reflectance fibre-optic probe (with a 5 cm × 5 cm quartz window) for the analysis of the hydrophilic (HI) and hydrophobic (HO) peptides and the ratio HO/HI was assayed. To do so, cheeses with known and varying percentages of cow’s, ewe’s and goat’s milk were elaborated (112 samples). Ripening controls were performed over 6 months, and the chemical data obtained by reversed-phase high performance liquid chromatography used as reference. The regression method employed was modified partial least squares (MPLS). The multiple correlation coefficients (RSQ) and prediction corrected standard errors (SEP (C)) obtained 0.879 and 1.83% for hydrophilic (HI) and 0.879 and 1.83% for hydrophobic (HO) peptides, respectively, and 0.890 and 0.03% for the ratio HO/HI. The method allows immediate control by direct application of the fibre-optic probe to the cheese without prior sample treatment or destruction.
3/21/09
Non-destructive assessment of apricot fruit quality by portable visible-near infrarednext term spectroscopy
The ability of portable Near Infrared Spectroscopy to determine apricot fruit quality has been studied. Calibration models allowing the determination of soluble solids content (SSC), total acidity (TA) and firmness (Fi) of apricots were carried out with variable precisions. Models were built for each variety and global models combining different varieties were attempted. SSC was determined with a root mean square error of cross-validation (RMSECV) comprised between 0.67 and 1.1 °Brix and R-values between 0.88 and 0.96. Concerning Fi, the accuracy of the prediction was variety dependant. These predictions were correct for the varieties Kioto and Harostar with RMSECV-values between 6.2% and 13% (R-values between 0.85 and 0.92) and unsatisfactory for Bergarouge (RMSECV = 24%). TA was predicted with RMSECV-values between 0.79 and 2.61 g 100 ml−1 and R-values between 0.73 and 0.97. In a second application, near infrared spectra were used to classify apricot fruits according to their variety and colour intensity with correct efficiency. The results obtained in the present study showed that NIRS technology could be applicable to apricot quality and that such portable devices could help to obtain a complete follow-up of the fruits in orchards and during post-harvest.
Near Infrared Spectroscopy to determine apricot fruit quality has been studied. Calibration models allowing the determination of soluble solids content (SSC), total acidity (TA) and firmness (Fi) of apricots were carried out with variable precisions. Models were built for each variety and global models combining different varieties were attempted. SSC was determined with a root mean square error of cross-validation (RMSECV) comprised between 0.67 and 1.1 °Brix and R-values between 0.88 and 0.96. Concerning Fi, the accuracy of the prediction was variety dependant. These predictions were correct for the varieties Kioto and Harostar with RMSECV-values between 6.2% and 13% (R-values between 0.85 and 0.92) and unsatisfactory for Bergarouge (RMSECV = 24%). TA was predicted with RMSECV-values between 0.79 and 2.61 g 100 ml−1 and R-values between 0.73 and 0.97. In a second application, near infrared spectra were used to classify apricot fruits according to their variety and colour intensity with correct efficiency. The results obtained in the present study showed that NIRS technology could be applicable to apricot quality and that such portable devices could help to obtain a complete follow-up of the fruits in orchards and during post-harvest.
3/20/09
Near-infrarednext term absorbing delocalized cationic azo dyes
Novel, delocalized, cationic azo dyes derived from benzothiazole, benzoselenazole, indole and quinoline, displaying strong absorption around 700–800 nm, have been prepared in moderate to good yields. The synthesis involved the Knoevenagel condensation of an intermediate azo compound, possessing a 4-chloro-5-formylthiazole moiety, with methylenic bases generated in situ from benzoazolium and quinolinium salts.
3/19/09
Rapid identification of dolomite using a Fourier Transform Infrarednext term Spectrophotometer (FTIR): A fast method for identifying Heinrich events i
This study demonstrates that Fourier Transform Infrared Spectrophotometry (FTIR) provides a quick and relatively inexpensive method for identifying and quantifying dolomite in deep marine sediments. FTIR is used to determine concentrations of dolomite in the top 29 m of sediments recovered at IODP Site U1308. Some of these dolomite peaks can be reliably correlated with Heinrich Events H1 through H6, thus FTIR appears to provide a fast and reliable method for identifying Heinrich Events in deep-sea sediments.
Infrared Spectrophotometry (FTIR) provides a quick and relatively inexpensive method for identifying and quantifying dolomite in deep marine sediments. FTIR is used to determine concentrations of dolomite in the top 29 m of sediments recovered at IODP Site U1308. Some of these dolomite peaks can be reliably correlated with Heinrich Events H1 through H6, thus FTIR appears to provide a fast and reliable method for identifying Heinrich Events in deep-sea sediments.
3/18/09
Application of near infrarednext term spectroscopy for rapid detection of aflatoxin B1 in maize and barley as analytical quality assessment
The establishment of fast and non-destructive methods for the evaluation of quality and safety of raw grains is being demanded nowadays to avoid toxic substance presence. Aflatoxin B1 (AFB1) has been recognised by the International Agency of Research on Cancer as a group 1 carcinogen for animals and humans and the EU Official Journal has established action levels for AFB1 presence in all feed materials between 5 and 20 ppb. Near infrared spectroscopy (NIRS) is an excellent candidate for a rapid and low-cost method for the detection of aflatoxins in cereals. This study assesses the utility of NIRS for rapid detection of mycotoxigenic fungi as AFB1. A total of 152 samples were involved and analysed for aflatoxin content. The results of spectroscopic models developed have demonstrated that NIRS technology is an excellent alternative for fast AFB1 detection in cereals. The best predictive model to detect AFB1 in maize was obtained using standard normal variate and detrending (SNVD) as scatter correction (r2 = 0.80 and 0.82; SECV = 0.211 and 0.200 for grating and FT-NIRS instruments, respectively). In the case of barley, the best predictive model was developed using SNVD on the dispersive NIRS instrument (r2 = 0.85 and SECV = 0.176) and using spectral data as log 1/R for FT-NIRS (r2 = 0.84 and SECV = 0.183).
Near infrared spectroscopy (NIRS) is an excellent candidate for a rapid and low-cost method for the detection of aflatoxins in cereals. This study assesses the utility of NIRS for rapid detection of mycotoxigenic fungi as AFB1. A total of 152 samples were involved and analysed for aflatoxin content. The results of spectroscopic models developed have demonstrated that NIRS technology is an excellent alternative for fast AFB1 detection in cereals. The best predictive model to detect AFB1 in maize was obtained using standard normal variate and detrending (SNVD) as scatter correction (r2 = 0.80 and 0.82; SECV = 0.211 and 0.200 for grating and FT-NIRS instruments, respectively). In the case of barley, the best predictive model was developed using SNVD on the dispersive NIRS instrument (r2 = 0.85 and SECV = 0.176) and using spectral data as log 1/R for FT-NIRS (r2 = 0.84 and SECV = 0.183).
3/17/09
A support vector machine-based analysis method with wavelet denoised near-infrarednext term spectroscopy
This paper is concerned with the rapid and non-destructive quantitative analysis of cimetidine in single intact tablets by diffuse reflectance spectroscopy. Support vector machines (SVM) are introduced to model multivariate, non-linear systems of calibration samples by radical basis functions. Short-wave near-infrared spectra ranging 760–1100 nm are processed by SVM. Wavelet method has been employed to minimize the influence of noise. Measurement errors of independent testing set by SVM compared to partial least squares (PLS) give relatively reasonable results. Experiments show that SVM with wavelet denoising pretreatment is an effective method and requires less number of calibration samples.
near-infrared spectra ranging 760–1100 nm are processed by SVM. Wavelet method has been employed to minimize the influence of noise. Measurement errors of independent testing set by SVM compared to partial least squares (PLS) give relatively reasonable results. Experiments show that SVM with wavelet denoising pretreatment is an effective method and requires less number of calibration samples.
3/16/09
Near-infrarednext term spectroscopy: A powerful tool in studies of acid-treated clay minerals
The benefit of near-infrared (NIR) spectroscopy in studies of acid-treated clay minerals is demonstrated. The effects of mineral type, composition and content of non-swelling interlayers on the dissolution rate are investigated. Detailed analysis of the NIR region is performed by comparing the first overtone (2νOH) and combination (ν + δ)OH bands with the fundamental stretching (ν) and bending (ν) vibrations. Spectra of acid-treated samples show a gradual decrease in the intensities of the structural OH overtone (near 7100 cm−1) and combination (4600–4300 cm−1) bands reflecting a fewer number of octahedral atoms. The appearance of the 2νSiOH vibration for terminal (isolated) SiOH groups near 7315 cm−1 indicates the formation of a protonated silica phase. The band near 7130 cm−1 remaining in the spectra of acid-treated samples is assigned to 2νHOSiOH of geminal silanol groups. Thus the creation of geminal silanols, previously detected by 29Si MAS-NMR spectroscopy in acid-treated hectorite, is confirmed also by NIR spectroscopy. The assignment of the 4555 cm−1 band to the (ν + δ)SiOH combination enabled calculation of the wavenumber for the SiO–H bending vibration (
810 cm−1) that is not observable in the mid-IR region due to overlapping with the Si–O band of amorphous silica (800 cm−1). The NIR spectra confirm that trioctahedral hectorite is much more susceptible to dissolution in HCl than dioctahedral nontronite. The dissolution rate of kaolinite present in the Badin clay as an admixture is lower than that of the main mineral nontronite. The accessibility of the interlayers for protons significantly influences the stability of clay minerals in HCl. Mixed-layered mineral illite/smectite with only 30% of swelling interlayers dissolves more slowly than smectite of similar chemical composition containing mainly swelling interlayers.
near-infrared (NIR) spectroscopy in studies of acid-treated clay minerals is demonstrated. The effects of mineral type, composition and content of non-swelling interlayers on the dissolution rate are investigated. Detailed analysis of the NIR region is performed by comparing the first overtone (2νOH) and combination (ν + δ)OH bands with the fundamental stretching (ν) and bending (ν) vibrations. Spectra of acid-treated samples show a gradual decrease in the intensities of the structural OH overtone (near 7100 cm−1) and combination (4600–4300 cm−1) bands reflecting a fewer number of octahedral atoms. The appearance of the 2νSiOH vibration for terminal (isolated) SiOH groups near 7315 cm−1 indicates the formation of a protonated silica phase. The band near 7130 cm−1 remaining in the spectra of acid-treated samples is assigned to 2νHOSiOH of geminal silanol groups. Thus the creation of geminal silanols, previously detected by 29Si MAS-NMR spectroscopy in acid-treated hectorite, is confirmed also by NIR spectroscopy. The assignment of the 4555 cm−1 band to the (ν + δ)SiOH combination enabled calculation of the wavenumber for the SiO–H bending vibration (810 cm−1) that is not observable in the mid-IR region due to overlapping with the Si–O band of amorphous silica (800 cm−1). The NIR spectra confirm that trioctahedral hectorite is much more susceptible to dissolution in HCl than dioctahedral nontronite. The dissolution rate of kaolinite present in the Badin clay as an admixture is lower than that of the main mineral nontronite. The accessibility of the interlayers for protons significantly influences the stability of clay minerals in HCl. Mixed-layered mineral illite/smectite with only 30% of swelling interlayers dissolves more slowly than smectite of similar chemical composition containing mainly swelling interlayers.
3/15/09
Construction of a universal model for non-invasive identification of cephalosporins for injection using near-infrarednext term diffuse reflectance spe
A universal classification model has been developed for identification of 26 different products of cephalosporins for injection using near-infrared (NIR) spectroscopy. A total of 324 batches of the 26 products, from 166 manufacturers in China, were used in the study. The classification model was a principle component analysis (PCA)-based method consisting of a primary identification library with four sub-libraries. The accuracy and specificity of the model were tested and were both found to be approximately 95%. The transfer of the classification model between different instruments of the same brand and the same instrument model has been investigated in this study. This study has shown that it is feasible to build a universal classification model to quickly screen for counterfeit drugs in the open market and distribution channels.
near-infrared (NIR) spectroscopy. A total of 324 batches of the 26 products, from 166 manufacturers in China, were used in the study. The classification model was a principle component analysis (PCA)-based method consisting of a primary identification library with four sub-libraries. The accuracy and specificity of the model were tested and were both found to be approximately 95%. The transfer of the classification model between different instruments of the same brand and the same instrument model has been investigated in this study. This study has shown that it is feasible to build a universal classification model to quickly screen for counterfeit drugs in the open market and distribution channels.