The museum has a long history of using CHNS analyzers of this type for the study of rock samples and was one of the first labs to start performing this type of analysis. Since being installed by the team, the vario EL cube has been used for the analysis of a variety of samples - including rocks, soils, leaves, wood, minerals and termite mounds - to identify their structural volatile element content.
When assessing rocks, Dr Humphreys-Williams’ researchers were mainly interested in the hydrogen and carbon contents of the rock samples, but they have also used the IR detector to analyze low concentrations of sulfur in rocks. The instrument has ably complemented the analysis of the elemental composition of rocks they already perform via digestion and analysis using ICP-OES and ICP-MS instruments.
However, the applications of the vario EL cube have gone beyond the analysis of these natural samples and have also been used in the study of photographic film. For this work, Dr Humphreys-Williams worked closely with Konstantina Konstantinidou, the museum’s paper conservator, who is responsible for conserving and advising on the preservation of paper-based collections, such as artworks, manuscripts, historic labels, etc. as well as advising on the preservation of photographic material like film, photographs, slides and X-ray film collections.
The team was able to use the vario EL cube for organic elemental analysis of its archival X-radiography materials, to determine which film sheets were made of cellulose nitrate, and therefore needed to be separated from the cellulose acetate or polyester-based materials for safety and conservation purposes.
The findings of this innovative study were published in the journal Studies in Conservation, and demonstrated that organic elemental analysis using the vario EL cube was an extremely useful method for identifying cellulose nitrate, as it proved to be more straightforward, quicker, accurate and reliable than other recommended tests, such as the float test or FTIR analysis. This method was also found to have the potential to provide an insight into the degradation of the cellulose nitrate film base.
Organic elemental analysis may also have potential to evaluate degradation of cellulose nitrate film. Since a healthy film is expected to have approximately 11% nitrate according to the literature and the percentage of nitrate reduces as the film deteriorates, organic elemental analysis may be useful in identifying and thus protecting vulnerable collections.
Commenting on the performance of the vario EL cube, Dr Humphreys-Williams said:
“The vario EL cube gives precise and accurate results on a range of sample materials, and has proved particularly useful in the analysis of rocks, plants and soils. We have also found it to be useful in the conservation of some specimens in the collections, identifying their chemical composition.
“The flexibility of the setup and trap and purge system allow for a large variation in sample types. From single minerals weighing a few milligrams to bulk rock samples, the instrument can be configured to give reliable data.”