N. Dupuy

Comparison between NIR, MIR, concatenated NIR and MIR analysis and hierarchical PLS model. Application to virgin olive oil analysis

This work investigates the potential use of simultaneously near-infrared (NIR) and mid-infrared (MIR) spectroscopies for the quantitative analysis of fatty acids and triacylglycerols and for identifying the Registered Designation of Origin (RDO) of extra virgin olive oils. The two spectral ranges were used separately using PLS and PLS-DA regressions. To combine both information, concatenated matrix was used at the first time, multiblock method using H-PLS models were constructed at the second time. The models were compared in terms of prediction errors. The results obtained with MIR spectroscopy are better than the ones obtained with NIR spectroscopy. The H-PLS methodology seems to be very interesting for quantitative analysis with the use of additional information in the NIR range, which is not present in the MIR one. For RDO identification by discriminant analysis, the use of multiblock method was less efficient.

Comparative chemometric analyses of geographic origins and compositions of lavandin var. Grosso essential oils by mid infrared spectroscopy and gas chromatography

Lavandin, a sterile hybrid of Lavandula angustifolia P. Mill. x Lavandula latifolia (L.f.) Medikus (Lamiaceae) is a plant widely cultivated for essential oil production in the South of France. Chemometric treatment by mid-infrared (MID-IR) spectroscopy data was assessed for the differentiation of Grosso Lavandin Essential Oils of Controlled Area (GLEOCA) and results were compared to those obtained by gas chromatography for MID-IR short time technique validation. The quantification of the main 13 hydrocarbons and oxygenated compounds generally controlled by industrial perfumers in GLEOCA samples (n=83) of three geographic origins: Simiane, Puimoisson (with two producers) and Richerenches and their classification were successfully obtained by partial least square discriminant analysis (PLS-DA) by comparison with gas chromatography. The best prediction results were obtained using first derivate spectral data in the 1800-700 cm(-1) range. The spectroscopic interpretation of regression vectors showed that each geographic origin was correlated to components of GLEOCA. Chemometric MID-IR spectra treatments allowed us to obtain similar results than those obtained by time consuming analytical techniques such as GC and therefore constitute a robust and help fast method for authentication of GLEOCA and should be extended to other essential oils for authentication of geographic origin.

Study of jojoba oil aging by FTIR

As the jojoba oil was used in cosmetic, pharmaceutical, dietetic food, animal feeding, lubrication, polishing and bio-diesel fields, it was important to study its aging at high temperature by oxidative process. In this work a FT-MIR methodology was developed for monitoring accelerate oxidative degradation of jojoba oils. Principal component analysis (PCA) was used to differentiate various samples according to their origin and obtaining process, and to differentiate oxidative conditions applied on oils. Two spectroscopic indices were calculated to report simply the oxidation phenomenon. Results were confirmed and deepened by multivariate curve resolution-alternative least square method (MCR-ALS). It allowed identifying chemical species produced or degraded during the thermal treatment according to a SIMPLISMA pretreatment.

Lipid compositions and French registered designations of origins of virgin olive oils predicted by chemometric analysis of mid-infrared spectra.

The combination of mid-infrared (MIR) spectroscopy with multivariate analysis provides an original approach to study the profile of virgin olive oils (VOOs) in relation to composition and geographical origin. Chemometric treatment of mid-infrared spectra (n = 402) is assessed for quantification of fatty acids (14 components) and triacylglycerols (19 components) in VOO samples and for classification into six very geographically closed registered designations of origin (RDOs) of French VOO (“Aix-en-Provence”, “Haute-Provence”, “Vallée des Baux de Provence”, “Nice”, “Nîmes”, and “Nyons”). Spectroscopic interpretation of regression vectors has shown that each RDO is correlated to one specific component of VOO according to their cultivar compositions. The results are satisfactory, in spite of the similarity of cultivar compositions between two denominations of origin (“Aix-en-Provence” and “Vallée des Baux de Provence”). Chemometric treatment of MIR spectra makes it possible to obtain similar results to those obtained by time-consuming analytical techniques such as gas chromatography (GC) and high-performance liquid chromatography (HPLC) and constitutes a fast and robust tool for authentication of these French VOOs.

Quantitative analysis of water-soluble vitamins by ATR-FTIR spectroscopy

HPLC and microbiology are the methods traditionally employed to control the vitamin content in food mixtures. However, considerations of cost, time of analysis per sample and complexities involved in the technique have hampered the acceptance of those methods for raw materials analysis. Fourier Transform Infrared (FTIR) spectroscopy has substantial potential as a quantitative quality control tool for the food industry. FTIR analysis methods are convenient, rapid, accurate, and in conjunction with Attenuated Total Reflectance (ATR) technology, simplify sample handling. The advantage of choosing FTIR as a quantitative technique lies in its ability to readily carry out multicomponent analysis in association with software such as Partial Least Squares (PLS) regression. Results presented here were obtained from water-soluble vitamins (B1, B2, B6 and Niacin) mixtures diluted into a glucose matrix without any chemical extraction.

Mid-infrared spectroscopy and chemometrics in corn starch classification

Abstract The authentication of food is a very important issue for both the consumer and the food industry at all levels of the food chain from raw materials to finished products. Corn starch can be used in a wide variety of food preparations such as bakery cream fillings, sauces, salad dressings, frozen foods etc. Many modifications are made to corn starch in connection with its use in agrofood. The value of the product increases with the degree of modification. Some chemical and physical tests have been devised to solve the problem of identifying these modifications but all the methods are time consuming and require skilled operators. We separate corn starches into groups related to their modification on the basis of the infrared spectra.

Investigation of gamma radiation effect on the anion exchange resin Amberlite IRA-400 in hydroxide form by Fourier transformed infrared and 13C nuclear magnetic resonance spectroscopies.

Radiation-induced decomposition of the anion exchange resin Amberlite IRA-400 in hydroxide form by gamma radiolysis has been studied under different irradiation doses and irradiation atmospheres. In this work, we focused on the degradation of the solid part of the resin by Fourier transformed infrared (FTIR) and (13)C nuclear magnetic resonance (NMR) spectroscopies associated with chemometric treatments. FTIR and (13)C NMR techniques showed that only -CH(2)N(+)(CH(3))(3) groups were detached from the resin whereas the polystyrene divinylbenzene backbone remains intact. The quaternary ammonium groups were replaced by amine or carbonyl groups according to the irradiation atmosphere (with or without water or oxygen). Principal components analysis (PCA) was used to classify the degraded resins according to their irradiation conditions by separating the effect of the dose or the environment. The PCA loadings have shown spectral regions which discriminate the irradiated resins whereas SIMPLe-to-use Interactive Self-modeling Mixture Analysis (SIMPLISMA) allows to identify families of component characterizing the chemical structure of resins and estimate their relative contributions according to the irradiation atmospheres.

Contribution of external parameter orthogonalisation for calibration transfer in short waves—Near infrared spectroscopy application to gasoline quality

The octane number rating of a gasoline gives an indication of the gasoline performances, under various engine conditions. Two different ratings are included: Research Octane Number (RON) and Motor Octane Number (MON). The standard laboratory method for octane number determination is the knock engine method in which a gasoline is burned and its combustion characteristics compared to known standards. This method is time consuming and labor intensive, and provides no ability for real time control of production. NIR can be applied in real time directly in process monitoring or as a laboratory procedure. Near infrared spectra of gasoline samples were collected thanks to four different short wavelengths near infrared analysers, built with strictly the same technology. The aim of this study was to transfer the calibration built on one spectrometer to the other ones. We applied the external parameter orthogonalisation (EPO) correction to get rid of the apparatus influence on information contained in spectra. By this method, we managed to improve prediction values of two major gasolines properties, i.e. Research and Motor Octane Number.

Quantitative determination of polymer and mineral content in paper coatings by infrared spectroscopy. Improvements by non-linear treatments

Abstract The quality of a printed image on coated papers, to a great extent, depends on the coating surface properties (nature of the components, relative abundance and so on). The potential of infrared spectroscopy as a rapid analytical technique for the quantitative analysis of the coating is demonstrated. Experimentally, spectra are recorded by Attenuated total reflectance (ATR) with Fourier transform infrared spectroscopy. Partial least squares (PLS) regression is used as the multivariate linear calibration method for predicting calcium carbonate, styrene and butadiene in the coatings. The effect of non-linear treatments is established by the improvements which occurred after the multiplicative scatter correction or the application of an artificial neural network on the PLS scores, especially near the concentration limits of each compound.

In situ characterisation of peroxybenzimidic acid by FT-Raman and ATR/FTIR spectroscopy

Abstract To elucidate the mechanism of the reaction of benzonitrile and hydrogen peroxide in alkaline medium, an experimental study was carried out by FT-Raman and ATR/FTIR. We were able to identify the intermediate peroxycarboximidic acid by assigning number of characteristic vibrations like νCue5fbN or νOue5f8O.