Polish Archaeology in the Mediterranean (15.2003(2004))

OLD DONGOLA

SUDAN

APPENDIX 3
ANALYSES OF BINDERS IN THE PAINTING LAYER
FROM THE CRUCIFORM BUILDING (B.III)
IN DONGOLA
Irmina Zadrozna
Warsaw University of Technology

The analysis of binders used in the
painting layer was carried out on samples
taken from different places in the object
under conservation-laboratory conditions.
Two independent spectroscopic techniques
were employed to obtain information on
the different ingredients of the binders:
Gas Chromatography-Mass Spectrometry
(GC-MS) and for a few samples the Fourier
Transformation Infrared Spectroscopy
(FTIR).
GC-MS is the best method for
analyzing complex mixtures as up to
hundreds of individual elements making
up a mixture can be separated out in the
capillary columns and then identified
explicitly by the spectrometer. The
technique also permits a quantitative
estimate of particular ingredients. It
requires, however, suitable sample
preparation, as the compounds used as
binders belong to different classes and are
frequently used concurrently in the
painting technique. The FTIR technique
complements gas chromatography-mass
spectrometry, identifying the binders as
belonging to specific classes of compounds.
In this case, the FTIR results served to
confirm GC-MS data.
For chromatographic analysis acidolysis
of the samples had to be carried out. The
product of acid hydrolysis was subjected to
derivatization (silylation) using BSA (N, O-
bistri-methylsilyloamide acetic acid) and

analyzed chromatographically. The GC-MS
analysis was carried out using an Ultra 2
capillary column and a Hewlett-Packard
HP-589011 gas chromatograph coupled
with HP-5971 A mass spectrometer.
Chromatography conditions: carrier gas —
helium 1 ml/min, dosing temperature
270°C for the samples, initial temperature
50°C for 5 min, 5°C/min up to 300°C for
5 min. Samples containing a minimum of
a few dozen micrograms of the organic
material dosed out by the splitless
technique. Identification of simple
compounds was carried out most frequently
through comparison of recorded spectrum
with the NIST Library computer spectra.
Model analyses of binders of known
composition were also carried out to provide
comparative material. Estimation of relative
quantity of selected compounds was made
by measuring the area of the signals in the
chromatogram.
The FTIR spectra were achieved on
a Perkin-Elmer spectrophotometer in a KBr
medium.
Sample no. 9 (first layer of plaster)
Sample was subjected to acidolysis. The
chromatogram contains insignificant
amounts of amino acids: glycine, alanine,
proline, glutamic acid and aspartic acid,
characteristic of a protein binder — egg
yolk. Insignificant amounts of mono- and
dicarboxyl acids also occur, including

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