Silky dating

The dating of silk textiles can be problematic for experts but a team of researchers at the Smithsonian Institute has developed a new method with this as their main objective.1

They have introduced a new capillary electrophoresis–mass spectrometry (CE–MS) technique based on amino acid racemization rates. As the amino acids making up proteins are chiral, being either left- or right-handed, or L or D, Moini and her team utilized aspartic acid, which has one of the fastest switching rates, a half-life of 2500 years, and separated the two enantiomers in a CE buffer containing a chiral molecule. They then determined their proportions using MS. Analysis required only 100 µg of silk fibre, which was digested with hydrochloric acid at 110 °C. This non-destructive method took only 20 minutes, consumed only nanolitres of the amino acid mixture and provided both amino acid composition profiles and D/L ratios for 11 amino acids.

Moini and her team were able to test this method on several silk fabric selections and found that the measured ratio of left- and right-handed aspartic acids reflected the historical ages of the selected fabrics.

1. Mehdi Moini et al., Anal. Chem., 83(19), 7577–7581 (2011)

This story originally appeared in The Column. Click here to view that issue.