What are the optimal conditions for sample concentration and volume when preparing for electrospray analysis?
Use the following guidelines for minimum sample concentration. A sample volume of at least 3 – 5 µl is desirable, more for dilute solutions. Depending on the sample, a concentration below that indicated may be sufficient. Clean, salt- and additive-free solvents are critical to obtain optimum signal. • Peptides (<5 kDa): 1 – 50 pmol/µl • Proteins (=5 kDa): 5 – 50 pmol/µl • Oligonucleotides: 10 – 100 pmol/µl • Enzyme digests: 1 – 20 pmoles—injected onto LC/MS columns If necessary, samples containing high salt may be submitted for analysis by C18 RP LC/MS trap cartridge clean up and online infusion. In this instance it would be more convenient and assay efficient if additional sample was available (10 – 20 µg) but this is not requisite.
