Method for preparing samples for mass analysis by desorption from a frozen solution

A method useful for processing large molecules for mass spectral analysis which comprises:

• (a) providing a solution containing one or more molecules to be analyzed having a molecular weight of at least about 500 amu dissolved in a low molecular weight solvent capable of absorbing a sufficient amount of the energy subsequently used to desorb said molecules from said solution so that from 70 to 100 % of the energy is absorbed within about 10 micrometers of the surface of the solution when frozen;
• (b) freezing said solution of dissolved molecules to form a frozen solution;
• (c) maintaining said frozen solution in a vacuum chamber at a temperature sufficiently low to provide a vapor pressure of less than 10.sup.-5 torr;
• (d) exposing said frozen solution in said vacuum chamber to a source of laser radiation energy sufficient to desorb from 1 to 100 layers of molecules to be analyzed from the surface of said frozen solution.

A method useful for processing large molecules for mass spectral analysis which comprises:

• (a) providing a solution containing one or more molecules to be analyzed having a molecular weight of at least about 500 amu dissolved in a low molecular weight solvent to form said solution, said solvent being capable of absorbing a sufficient amount of the energy subsequently used to desorb said molecules from said solution so that from 70 to 100% of the energy is absorbed within about 10 micrometers of the surface of the solution when frozen;
• (b) freezing said solution of dissolved molecules to form a frozen solution;
• (c) maintaining said frozen solution in a vacuum chamber at a temperature sufficiently low to provide a vapor pressure of less than 10.sup.-5 torr;
• (d) exposing said frozen solution in said vacuum chamber to a source of energy sufficient to desorb from 1 to 100 layers of molecules to be analyzed from the surface of said frozen solution and selected from the class consisting of laser radiation, ion beam bombardment, electron beam bombardment, and fast atom beam bombardment.

A method useful for preparing a sample of nonvolatile molecules for mass spectral analysis which comprises:

• (a) providing a solution comprising one or more types of molecules having a mass of at least about 500 AMU to be analyzed dissolved in a low molecular weight solvent selected from the class consisting of water, 1-5 carbon organic solvents, and mixtures thereof, which solvent strongly absorbs the energy used to desorb said large molecules to permit desorption of said molecules on the surface of a frozen solution without substantial absorption of said energy below the surface of said frozen solution to thereby inhibit heating of the entire solution;
• (b) freezing said solution of dissolved molecules to form a frozen solution;
• and
• (c) exposing said frozen solution to a source of laser radiation energy to desorb molecules to be analyzed from the surface of said frozen solution.

A method useful for preparing a sample of thermally labile molecules for mass spectral analysis while minimizing the risk of fragmentation of such molecules during desorption which comprises:

• (a) forming a solution by dissolving one or more types of such thermally labile molecules to be analyzed in a solvent capable of absorbing from 70 to 100% of the energy from a desorbing energy source within about 10 micrometers of the surface of the solution when frozen;
• (b) freezing said solution of dissolved molecules to form a frozen solution;
• and
• (c) exposing said frozen solution to a source of laser radiation energy to desorb molecules to be analyzed from the surface of said frozen solution.