INVESTIGATION OF VARNISHES WITH DIFFERENT ANALYTICAL METHODS
Autor:
Anu Teearu, Signe Vahur, Ivo Leito
Year:
Anno 2015
Category:
Research
Varnish has an important role in the composition of an art object. It adds decorative value to
the object and helps to protect it from light, humidity, dust particles, etc., all of which
accelerate the changes in the chemical composition of the varnish. In order to identify the
varnish used on an art object different analytical methods can be used. However, the
requirements for the methods are high. Varnish samples are usually a complex mixture of
different components, small in size and amount and difficult to dissolve. IR and Raman
spectroscopy are simple and fast methods that allow distinguishing between different
material classes, but the identification of the various components in multi-component sample
spectra is difficult due to overlapping of peaks in IR analysis and the interference of
fluorescence in Raman spectroscopy. GC-MS, LC-MS and different mass spectrometers (e.g.
FT-ICR-MS and ToF) coupled with soft ionization techniques such as MALDI, ESI, APCI
are very efficient in identifying the chemical composition of the sample. At the same time the
different chromatographic and mass spectrometric methods mentioned above are more labour
intensive (requiring sample preparation) and demanding (solvent suitability must be taken
into account etc.) compared to convenient ATR-FT-IR spectroscopy. Combining IR or Raman
methods with different mass spectrometric and chromatographic methods enables to obtain a
fairly comprehensive picture of the varnish composition.
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