Development of a gel permeation chromatography method for analysing cellulose nitrate in museums

Abstract

This article describes the development of a suitable Gel Permeation Chromatography method for cellulose nitrate plasticised with camphor (celluloid) found in cultural heritage. Current sample preparation and dissolution methods, apart from focusing on native, nonderivatised cellulose, require long preparation times, and often employ solvents that induce degradation. This study aims to develop a systematic method for sample preparation of cellulose nitrate that uses the least sample amount possible, is nondegrading, and can be applied on differently aged samples. This is investigated through identification of a suitable solvent system and a statistically designed experiment testing the critical variables affecting the analysis, namely sample condition, sample, and salt concentration (lithium chloride) in N,N-dimethylacetamide. The use of 0.1% sample was inadequate for analysis because it did not fully dissolve in any salt concentration, while the 0.3% negatively impacted the analysis with its high molecular weight distributions. The 0.2% cellulose nitrate in a solution of 0.5% lithium chloride in N,N-dimethylacetamide offered the most consistent and repeatable molecular weight data. This method miniaturised the sample as much as possible and is suitable for museum objects in various ageing conditions.

Shedding Light on Degradation Gradients in Celluloid: An ATR-FTIR Study of Artificially and Naturally Aged Specimens

“…In particular, chromatographic techniques could be applied, following the same in-depth sampling strategy implemented in this work, to measure the molecular weight (M w ), the nitrogen and camphor contents. In detail, size exclusion chromatography (SEC) can be used for determining the M w of CN [ 27 , 51 , 52 ] and measuring the amount of camphor [ 27 ] along sample points that show distinct νC=O infrared absorptions. Ion chromatography (IC) can be applied instead to quantify N content and, in turn, to estimate the extent of denitration [ 17 ].…”

Mock-Ups in Plastic Conservation Research: Processing and Aging of 3D Celluloid Specimens Simulating Historical Objects

“…Based on the method of Kavda et al [ 24 ], 2 mg of sample was dissolved in 1 mL of N,N-dimethylacetamide (DMAc 99.5% HPLC grade, Alfa Aesar) with 0.5% w / v lithium chloride (LiCl ACS 99%, Alfa Aesar) and left to dissolve overnight. Before injection, samples were filtered through a poly(tetrafluoroethylene) filter (PTFE, pore size 0.2 μm, diameter 25 mm) to remove any insoluble material and impurities.…”

“…In this study, two collections of transparent naturally aged celluloid were considered ( Figure 3 ), which were also already part of previous investigations by the authors Kavda et al [ 24 ] and Elsässer et al [ 16 ]. These materials were in extremely poor condition and fragmented, allowing extensive sampling for research purposes.…”

“…Following the strategy proposed by [ 16 ], the extent of degradation was assessed in detail by ion chromatography (IC) and gel permeation chromatography (GPC). These destructive techniques allow the investigation of the leading chemical and physical alteration processes of celluloid, namely, the breakdown of the polymer, denitration with the emission of nitrous gases, and the loss of plasticizers, particularly camphor [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ].…”