ABSTRACT
Quantitative non-destructive analysis of individual constituents of historic rag paper is crucial for its effective preservation. In this work, we examine the potentials of mid- and near-infrared spectroscopy, however, in order to fully utilise the selectivity inherent to spectroscopic multivariate measurements, genetic algorithms were used to select spectral data derived from information-rich FT-IR or UV-vis-NIR measurements to build multivariate calibration models based on partial least squares regression, relating spectra to gelatine content in paper. A selective but laborious chromatographic method for the quantification of hydroxyproline (HYP) has been developed to provide the reference data on gelatine content. We used 9-fluorenylmethyl chloroformate (FMOC) to derivatise HYP, which was subsequently determined using reverse-phase liquid chromatographic separation and fluorimetric detection. In this process, the sample is consumed, which is why the method can only be used as a reference method. The sampling flexibility afforded by small-size field-portable spectroscopic instrumentation combined with chemometric data analysis, represents an attractive addition to existing analytical techniques for cultural heritage materials.
Subject(s)
Gelatin , Hydroxyproline , Paper/standards , Spectroscopy, Fourier Transform Infrared/methods , Spectroscopy, Near-Infrared/methods , Algorithms , Calibration , Cellulose/analysis , Cellulose/chemistry , Chromatography, High Pressure Liquid , Gelatin/analysis , Gelatin/chemistry , Gelatin/genetics , History, 17th Century , History, 18th Century , History, 19th Century , Hydrolysis , Hydroxyproline/analysis , Hydroxyproline/chemistry , Multivariate Analysis , Paper/history , Principal Component Analysis , Regression Analysis , Time FactorsABSTRACT
A new chromatographic method for determination of hydroperoxides in cellulose is described, whereby the sample is dispersed in phosphate buffer solution (pH 7) of FeCl(3), EDTA and the hydroxyl radical scavenger, N,N'-(5-nitro,1,3-phenylene)bisglutaramide. The reaction time, concentration of reagents and chromatographic conditions for subsequent separation and quantification of hydroxylated products are optimised. The limit of detection is 0.14 micro mol L(-1) H(2)O(2) which corresponds to 2.1 micro mol hydroperoxides per kg of cellulose (mass of sample: 0.4 g). It was shown that in the concentration range of H(2)O(2) up to 15 micro mol L(-1) the method gives linear response and that adsorption of reaction products on fibres is negligible. For cellulose samples, this corresponds to a linear range of 2.1-225 micro mol of hydroperoxides per kg. Due to possible side reactions of hydroxyl radicals in the suspension of analyte, it is recommended that the standard addition technique is used. In purified cotton cellulose, the steady state concentration of hydroperoxides at room conditions was found to be 15.1+/-1.5 micro mol kg(-1).
