COMMENT - REPRODUCIBILITY OF SPECTRA AND THRESHOLD FLUENCE IN MATRIX-ASSISTED LASER DESORPTION IONISATION (MALDI) OF POLYMERS/

We represent that roughing of the stainless steel substratum by sandbl asting (SB) and ''fast evaporation'' deposition of 2,5-dihydroxybenzoi c acid (2,5-DHB) leads to more consistent and repeatable results. It w as shown that sandblasting (SB) gave representative results, which had higher precision than the non-sandblasted (NSB) substrate on the stai nless steel slide. The SE samples were more reproducible, as seen by t he (i) over bar/a(higher value) as compared to the NSB (lower (i) over bar/sigma vales). The values range from 13.46 (SE) to 1.34 (NSB). It was also shown, that the SE samples were more reproducible shot per sh ot. This was due to the sandblasted roughing of the slide, which gave more surface area over which the matrix could distributes itself more evenly. This treatment also gave lower thresholds. The threshold of th e PEG was lower on the SE region (P 100) compared to that of the NSB r egion (P 120) for the 2,5-DHB-PEG-NaCl system.