Matija Strlič

Evaluation of size-exclusion chromatography and viscometry for the determination of molecular masses of oxidised cellulose

The molecular masses of oxidised cellulose samples from two different sources were determined by size-exclusion chromatography (SEC) and viscometry. SEC was performed at room temperature using a cross-linked polystyrene-divinylbenzene column and 1% LiCl (w/v) in N,N-dimethylacetamide (DMAc) as the eluent. Cellulose samples were oxidised using aqueous solutions of H2O2, NaClO or KlO(4), and dissolved in the LiCl-DMAc solvent system using activation with water and a solvent exchange procedure. Viscometry in the cupriethylenediamine (CED) solvent system was performed following the standard technique. Oxidised cellulose samples are prone to degradation by alkalis, While the dissolution in LiCl-DMAc was shown not to have a degrading effect, the oxidised cellulose samples are unstable in the highly alkaline CED solvent, thus introducing a systematic error to the viscometric measurements. A stabilising reduction procedure usually recommended for such samples was tested, and shown to be advantageous, although degradation cannot be completely avoided

Size exclusion chromatography of cellulose in LiCl/N, N-dimethylacetamide

Size exclusion of cellulose in LiCl/N,N-dimethylacetamide has been used for the past 15 years, yet much of the current research is still devoted to fundamental studies, as many issues regarding column calibration, separation mechanisms and solution behavior have not been resolved yet. The paper reviews practical aspects of sample preparation and it is demonstrated that sample heating and several techniques to aid solvent exchange call for reevaluation. It is further shown that the use of internal standard may introduce minor improvements in repeatability. The commonly used column calibration procedures, chromatographic conditions and applications are also reviewed. Further research is needed to understand the mechanisms of separation, to optimize column calibration and to facilitate and optimize sample preparation.

Chemiluminescence from paper I. Kinetic analysis of thermal oxidation of cellulose

Abstract Kinetic analysis of chemiluminescence intensity—time and chemiluminescence intensity—temperature runs for oxidation of cellulose at elevated temperatures is presented showing a good coincidence of the first-order rate constants from non-isothermal chemiluminescence experiments with those obtained from polymerisation degree determinations and from the literature. Rate constants from isothermal runs are lower than those from non-isothermal runs, however, when repeating non-isothermal runs several times in so-called temperature cycling experiments, the non-isothermal rate constants approach isothermal ones. A method enabling the differentiation of faster and slower processes in oxidation of cellulose based on non-isothermal chemiluminescence runs is demonstrated.

Non-Destructive Evaluation of Historical Paper Based on pH Estimation from VOC Emissions

Volatile organic compounds (VOCs) emitted from materials during degradation can be a valuable source of information. In this work, the emissions of furfural and acetic acid from cellulose were studied using solid-phase micro-extraction (SPME) in combination with gas chromatography-mass spectrometry. Two sampling techniques were employed: static headspace sampling using SPME for 1 h at 40 °C after 18-h sample preparation at 80 °C in a closed glass vial, and contact SPME in a stack of paper (or a book). While a number of VOCs are emitted from paper under conditions of natural or accelerated degradation, two compounds were confirmed to be of particular diagnostic value: acetic acid and furfural. The emissions of furfural are shown to correlate with pH of the cellulosic environment. Since pH is one of the most important parameters regarding durability of this material, the developed method could be used for non-destructive evaluation of historical paper.

Quantitative NIR Chemical Imaging in Heritage Science

Until recently, applications of spectral imaging in heritage science mostly focused on qualitative examination of artworks. This is partly due to the complexity of artworks and partly due to the lack of appropriate standard materials. With the recent advance of NIR imaging spectrometers, the interval 1000-2500 nm became available for exploration, enabling us to extract quantitative chemical information from artworks. In this contribution, the development of 2D NIR quantitative chemical maps of heritage objects is discussed along with presentation of the first quantitative image. Further case studies include semiquantitative mapping of plasticiser distribution in a plastic object and identification of historic plastic materials. In the NIR imaging studies discussed, sets of 256 spatially registered images were collected at different wavelengths in the NIR region of 1000-2500 nm. The data was analyzed as a spectral cube, both as a stack of wavelength-resolved images and as a series of spectra, one per each sample pixel, using multivariate analysis. This approach is only possible using well-characterized reference sample collections, as quantitative imaging applications need to be developed, thus enabling spatial maps of damaged and degraded areas to be visualized to a level of chemical detail previously not possible. Such quantitative chemical mapping of vulnerable areas of heritage objects is invaluable, as it enables damage to historic objects to be quantitatively visualized.

Near-UV and visible pulsed laser interaction with paper

The applicability of excimer laser at 308 nm and Nd:YAG laser at 532 nm with fluences below 0.86 J/cm2 for cleaning of cellulose and paper materials was evaluated. The extent of degradation of purified cotton cellulose and Fabriano paper after laser treatment as well as after a period of accelerated humid oven ageing was determined by following the changes in the degree of polymerization. While irradiation of paper with the excimer laser at 308 nm results in depolymerization of cellulose accompanied by a decrease in ISO brightness, no detrimental effects of Nd:YAG laser treatments were observed.

Chemiluminescence during thermal and thermo-oxidative degradation of cellulose

The chemiluminescent phenomena during thermal and thermo-oxidative degradation of cellulosic material and model substances were found to originate in at least three relatively independent processes. The low-temperature chemiluminescent phenomenon typical of samples previously irradiated with an incandescent light source and dependent on both temperature and composition of the surrounding atmosphere during irradiation is attributed to the decay of charge-transfer complexes between oxygen and hydroxyl and/or ether groups in cellulose. A peak in chemiluminescence during dynamic experiments at 135°C typical of pre-oxidised samples can be associated with decomposition of peroxide groups present in the sample. An intense chemiluminescence at temperatures approaching 200°C was found to correlate with polymer chain scissions, resulting in the decrease in the degree of polymerisation determined by viscometry. The results show that the chemiluminescence approach may shed new light on the radical degradation mechanisms of cellulose and related polyhydroxylated polymers.

Depletion of high-abundance proteins from human plasma using a combination of an affinity and pseudo-affinity column.

Human serum albumin (HSA) and immunoglobulin G (IgG) represent over 75% of all proteins present in human plasma. These high-abundance proteins prevent the detection of low-abundance proteins which are potential markers for various diseases. The depletion of HSA and IgG is therefore essential for further proteome analysis. In this paper we describe the optimization of conditions for selective depletion of HSA and IgG using affinity and pseudo-affinity chromatography. A BIA Separations CIM (convective interaction media) Protein G disk was applied for the removal of IgG and the Mimetic Blue SA A6XL stationary phase for the removal of HSA. The binding and the elution buffer for CIM Protein G disk were chosen on the basis of the peak shape. The dynamic binding capacity was determined. It was shown to be dependent on the buffer system used and independent of the flow rate and of the concentration of IgG. Beside the binding capacity for the IgG standard, the binding capacity was also determined for IgG in human plasma. The Mimetic Blue SA A6XL column was characterized using human plasma. The selectivity of the depletion was dependent on the amount of human plasma that was loaded on the column. After the conditions on both supports had been optimized, the Mimetic Blue SA A6XL stationary phase was combined with the CIM Protein G disk in order to simultaneously deplete samples of human plasma. A centrifuge spin column that enables the removal of IgG and HSA from 20 microL of human plasma was designed. The results of the depletion were examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis.

Comparison testing of methods for gel permeation chromatography of cellulose: coming closer to a standard protocol

A round robin on GPC of a wide range of different pulp samples was conducted among leading groups in cellulose analysis. The aim was to survey the status quo of the methods available to date. The pulp samples covered not only fully-bleached dissolving pulps but also bleached paper pulps and one unbleached sample. The methods applied were current state-of-the-art GPC with RI, MALLS, and viscosimetry detectors. Different dissolution protocols were compared as well. Following from the obtained results, more standardized protocols were proposed for approaches with different equipment (RI or MALLS/RI) and solvent systems (direct dissolution or derivatization). Major influencing factors, such as derivatization compared to direct solution, calibration versus light scattering and in-between lab variation, were discussed.

Fine particulate matter in indoor cultural heritage: a literature review

Fine particulate matter is, on account of its aerodynamic properties and typical composition (especially diesel particulate matter and carbonaceous particles) the particulate pollutant potentially most harmful to cultural heritage, representing an aesthetic issue and an agent of chemical degradation simultaneously. This paper reviews the current knowledge of the life-cycle of fine particulates, focussing on diesel particulate matter from emission to deposition, including its aesthetic and chemical consequences, and draws attention to some imbalances in the current state of research. The currently available measurements are biased towards coarse dust, and information on the consequences of particle deposition is largely restricted to the outdoor environment. More evidence on the chemical effects of the most common types of fine particulate matter in typical indoor materials is needed to enable risk assessment for indoor collections.