Method, composition and device for sampling natriuretic peptides in a biological fluid

A device useful for sampling a protein profile in a biological fluid of interest, comprising:

• a component for receiving a fluid fraction of the biological fluid, the component containing an effective amount of a first protease inhibitor selected from the group consisting of leupeptin and benzamidine;
• and an effective amount of a second protease inhibitor, based on sulfonyl fluoride, suitable for inactivating serine proteases, wherein the effective amount of the second protease inhibitor results in the formation of protein adducts in the absence of the first protease inhibitor;
• and
• wherein the sampled protein profile is not substantially modified by the formation of adducts by the first protease inhibitor and the second protease inhibitor in combination.

A method of sampling a protein profile in a biological fluid of interest, comprising:

• adding an effective amount of chelator to a sample of the biological fluid;
• adding an effective amount of a first protease inhibitor selected from the group consisting of leupeptin and benzamidine;
• and
• adding an effective amount of a second protease inhibitor, based on sulfonyl fluoride, suitable for inactivating serine proteases, wherein the effective amount of the second protease inhibitor results in the formation of protein adducts in the absence of the first protease inhibitor;
• and wherein the sampled protein profile is essentially unmodified by the formation of adducts by a combination of the effective amount of the first protease inhibitor and the effective amount of the second protease inhibitor in combination.