Dating silk by capillary electrophoresis mass spectrometry
Now, for the first time, scientists at the Smithsonian's Museum Conservation Institute have developed a fast and reliable method to date silk.
The new method uses the natural deterioration of the silk's amino acids--a process known as racemization--to determine its age.
The Smithsonian Museum Conservation Institute team used fiber samples taken from a series of well-dated silk artifacts to create a chart of left-hand and right-handed amino-acid calibration ratios against which other silks fabrics can be dated.
Those items included new silk fibers; a silk textile from the Warring States Period, China (475-221 B.
They used a technique that made popular the silk from Murcia in the 19th century.
The performance of this interface is demonstrated by analyses of a peptide standard and a protein digest using a variety of capillary dimensions....
Proteins are made of amino acids," explains Smithsonian research scientist Mehdi Moini, chief author of a recent paper in the journal Analytical Chemistry announcing the new dating method.
Moreover, bubble formation due to redox reactions of water at the electrode does not effect CE/ESI-MS performance, because the actual metal/liquid contact occurs outside of the CE capillary.
Previously, the scientists write, dating silk has been largely been a speculative endeavor that has mostly relied on the historical knowledge of a silk piece, as well as its physical and chemical characteristics.
The new technique takes about 20 minutes, and requires the destruction of about 100 microgram of silk fiber, making it preferable over C14 (carbon 14) dating, which requires the destruction of so much material that it is prohibitive for most fine silk items.
In addition, because the liquid is flowing through the opening and out of the capillary, there is no dead volume associated with this interface.
MALDI-TOF Mass Spectrometry of Synthetic Polymers By Harald Pasch (Deutsches Kunststoff-Institut, Darmstadt, Germany) and Wolfgang Schrepp (BASF AG, Ludwigshafen, Germany). As a result of the concentration-sensitive nature of ESI, splitting a small percentage of the CE flow has minimal effect on the sensitivity of detection.
The sensitivity associated with a sheathless CE/MS interface, the ease of fabrication, universality, and lack of any dead volume make this design a superior CE/ESI-MS interface.