11/8/2023 0 Comments Download chca final formsFor a quantification of 1 fmol of the peptide using an internal standard the coefficient of variation is reduced to 3.5 % from 8 %. The relative standard deviation in peak area of angiotensin II for sample amounts between 1 and 50 fmol is reduced to about 15 % compared with 45 % for untreated sample holders. Compared with untreated targets, the signal intensities of standard peptides are up to eight times higher when using the graphite supported crystallization. This surface modification considerably improves analysis of peptides and proteins for MALDI MS using conventional dried-droplet preparation. Commercially available graphite powder of 1–2 μm particle size is gently wiped over the target using a cotton Q-tip, leading to an ultra-thin, not-visible film. A conventional dried-droplet preparation of matrix and analyte solution on a graphite-coated metal target leads to a thin, uniform layer of cubic crystals with about 1 μm edge length. Here, we demonstrate that graphite can be used as target coating supporting the crystallization of the α-cyano-4-hydroxycinnamic acid matrix. Graphite as MALDI matrix or in combination with other substances has been reported in recent years.
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