Characterization of blood in an encrustation on an African mask: spectroscopic and direct analysis in real time mass spectrometric identification of haem.

Prior to exhibiting an African Komo mask from the collections of the Detroit Institute of Arts, a multianalytical approach was undertaken to characterize the flaking encrusted coating on the surface of the mask. Preliminary XRF and FTIR examination of the coating on the Komo mask revealed the presence of significant quantities of iron and protein, possibly indicating the presence of blood. Raman spectroscopy showed evidence for the porphyrin structure of haem as well. To confirm that blood was indeed present in the coating, we developed a novel method for identifying the haem moiety from blood by use of in situ methylation and direct analysis in real time mass spectrometry (DART-MS). Following a denaturing step with formic acid, the resulting solution was combined with an excess of phenyltrimethylammonium hydroxide to promote desorption, applied to a melting point tube, and placed into the direct analysis in real time ion source gas stream at 550 °C. The permethylated haem ion (m/z 644.208) from myoglobin, haemoglobin, fresh blood, and blood aged in the laboratory for 10 years was readily observed above the background. By the described DART-TOF-MS method, permethylated haem was positively identified in the mask coating, confirming the presence of blood. This method has obvious utility in forensic science beyond that for identifying blood incorporated in cultural heritage materials.

Direct identification of dyes in textiles by direct analysis in real time-time of flight mass spectrometry.

We present here a method requiring no sample preparation for direct identification of the organic dye compounds quercetin, indigotin, and alizarin in reference materials, in solution, and also in situ in dyed fibers by use of direct analysis in real time (DART) ionization and high-resolution time-of-flight mass spectrometry. Exact mass determinations on small samples of dyed textiles were completed in less than 1 min. With the ability to identify flavonoid, indigoid, and anthraquinone classes of dyes, this technique shows early promise as an additional analytical tool in the challenging analysis of organic dyes in rare cultural heritage materials and possesses the unique advantages of sensitivity and simplicity without the preparatory procedures required by other methods.