Direct liquid injection inlet to a laser photoionization apparatus
AssigneeSRI International
InventorsHarald Oser, Michael J. Coggiola, Steven E. Young, David R. Crosley
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Abstract
A method and apparatus are provided for analyzing an analyte at low concentration in a liquid sample by photoionization and mass spectrometry. An inlet system is provided for direct injection of the liquid sample using a capillary tube. The method and apparatus allow for 20 to 2000-fold improvement of the lower detection limit of an analyte in a liquid sample compared to a conventional liquid chromatography/mass spectrometer apparatus.
Claims14
A method for analyzing an analyte at low concentration in a liquid sample by mass spectrometry comprising the steps of:
- (a) introducing a liquid sample containing said analyte into a capillary tube having a proximal end for receiving a liquid sample and a distal end for exit of said sample;
- (b) forming the liquid sample exiting said distal end into a directed stream of droplets along a path toward a zone of photoionization under a gradient of successively lower pressure such that substantial condensation of said analyte along said path is avoided;
- (c) directing said stream into said zone of photoionization to ionize said analyte to form analyte ions;
- and
- (d) passing said analyte ions into a mass analyzer of a mass spectrometer for mass analysis of said ions.
An apparatus for irradiation of a liquid sample containing an analyte to be ionized, comprising:
- (a) a capillary tube for introducing said liquid sample as droplets into said apparatus;
- (b) a zone of photoionization for irradiating evaporated droplets of said liquid sample at subatmospheric pressure to form ionizable species;
- (c) a region of subatmospheric pressure characterized by a gradient of successively lower pressure along a path toward said zone of photoionization;
- (d) a collimator for directing a collimated stream of evaporated droplets of said sample along said path directly into said zone of photoionization;
- and
- (e) a mass spectrometer for determining the m/e ratio of ions found by irradiating said sample.
Dependencies are inferred from the claim text.