ELECTROSPRAY ION SOURCE FOR QUADRUPOLE MASS FILTERS

RECENT DEVELOPMENTS HAVE SHOWN THAT ELECTROSPRAY IONIZATION CAN PRODUCE INTACT IONS FROM LARGE, COMPLEX, AND FRAGILE SPECIES WITH GREAT EFFICIENCY AND EXTENSIVE MULTIPLE CHARGING. SUBNANOMOLE SAMPLES OF POLYPEPTIDES AND SMALL PROTEINS IN THE MASS RANGE OF 25 KILODALTONS HAVE BEEN ANALYZED. BECAUSE EACH ION CAN HAVE AS MANY AS 25 OR MORE CHARGES, THE MASS ANALYSIS COULD BE CARRIED OUT WITH A SMALLQUADRUPOLE MASS FILTER HAVING A NOMINAL UPPER MASS LIMIT OF 1,500 DALTONS. THE APPARATUS INCORPORATED RELATIVELY LARGE PUMPING SPEEDS OF APPROXIMATELY 2,000 LITERS PER SECONDS. THIS RESEARCH AIMS TO DECREASE THE PUMPING SPEED REQUIREMENTS OF ELECTROSPRAY IONIZATION SOURCES SO THAT THEYCAN BE FITTED TO QUADRUPOLE MASS SPECTROMETER SYSTEMS IN ACTUAL OR PROSPECTIVE USE. SUCH SYSTEMS TYPICALLY HAVE TOTAL PUMPING SPEEDS OF 700 LITERS PER SECOND OR LESS. A THIRD PUMPING STAGE BETWEEN THE ELECTROSPRAY IONIZATION SOURCE AND THE SPECTROMETER VACUUM SYSTEM WILL BE PROVIDED. PROJECTIONS INDICATE THAT SUCH A STAGE WILL REQUIRE ONLY A SIMPLE ROTARY MECHANICAL PUMP WITH A SPEED OF 60 LITERS/MINUTE.