US 5,345,079 A · Apparatus and method for liquid sample introduction

Abstract

A liquid sample to be analyzed is fed to a micro pump. The pump directs the solution, as a stream of uniformly sized and spaced droplets, into a laminarly flowing stream of hot carrier gas. The carrier gas evaporates the solvents (e.g. water) in the droplets to form a stream of dried particles. The particles are vaporized by a plasma, laser or other heat source. The vapour can be ionized and the ions analyzed by a mass spectrometer, or the vapour can be analyzed by optical spectroscopy. The method reduces oxide and other interference effects, increases sample utilization, and reduces waste, signal noise, and memory effects, increasing instrument productivity. Multiple nozzles can be used to change samples or to shoot calibrating droplets, further increasing productivity. Signal detection can be synchronized with droplet firing, or the signal, which is intrinsically modulated at the drop frequency, can be band pass filtered and synchronously detected, to increase the signal to noise ratio. The dried particles can also be directed into a vacuum chamber and deposited in a desired pattern on a surface in the vacuum, thus delivering controlled microdosages of material onto the surface.

Claims58

Dependent claims

A method of sampling a liquid solution containing dissolved solids, comprising:

(a) producing a stream of laminarly flowing carrier gas travelling in a predetermined direction at a selected speed,
(b) producing a linear stream of spaced small droplets from said solution, said droplets being of substantially equal size and being uniformly spaced apart in single file on a common axis and travelling in said predetermined direction at a speed which does not differ substantially from said selected speed,
(c) introducing said stream of droplets in said predetermined direction into said stream of carrier gas and transporting said droplets with said carrier gas, the substantial equality of the speed and direction of said droplets with the speed and direction of said laminarly flowing carrier gas minimizing production of wakes by said droplets in said carrier gas,
(d) heating said carrier gas and thereby heating said droplets therein, to evaporate water from said droplets into said carrier gas,
(e) transporting said droplets in said carrier gas until said droplets have substantially dried to form a stream of uniformly spaced, equal size dried particles arranged in single file on an axis, said particles containing solids from said solution,
(f) vaporizing said dried particles to produce vapor therefrom,
(g) and analyzing said vapor.

4 more elements

Apparatus for analyzing solids dissolved in a liquid solution, comprising:

(a) a chamber for said solution, said chamber having an outlet nozzle, and means for applying a pressure pulse to solution in said chamber to shoot a droplet of said solution from said nozzle at a selected speed,
(b) tube means coupled to said nozzle for receiving said droplet,
(c) means for introducing a stream of carrier gas into said tube means for said carrier gas to flow in said tube means at a selected velocity and to carry said droplet along said tube,
(d) means for heating said droplet in said carrier gas,
(e) said tube means being sufficiently long for substantially all of the water in said droplet to evaporate into said carrier gas leaving a substantially dried particle of said solids,
(f) means connected to said tube means for vaporizing said dried particle,
(g) and analyzer means coupled to said tube means for analyzing the vapour from said dried particle.

4 more elements

A method of analyzing solids dissolved in a liquid sample solution, comprising:

(a) producing small droplets from said solution,
(b) producing a single laminar stream of flowing carrier gas having a central portion and an outer portion, said central and outer portions flowing in the same direction at substantially the same speed,
(c) directing said droplets into said central portion of said stream and conveying said droplets in said central portion of said stream,
(d) heating said carrier gas and said droplets to evaporate water from said droplets into said carrier gas,
(e) transporting said droplets in said carrier gas until said droplets are substantially dried to form dried particles containing said solids,
(f) allowing water vapor removed from said particles to disperse away from said particles,
(g) the diameter of said outer portion being substantially larger than that of said central portion, to allow said water vapor to disperse out of said central portion into said outer portion thus to reduce the concentration of water vapor in the immediate vicinity of said particles,
(h) and directing said stream of carrier gas into a torch having a plasma formed therein, and causing said central portion to penetrate into said plasma and causing said outer portion to supply at least a portion of the gas used to form said plasma.

5 more elements

Apparatus for analyzing solids dissolved in a liquid solution, comprising:

(a) tube means,
(b) means for introducing a stream of carrier gas into said tube means for said carrier gas to fill said tube means and to flow laminarly in said tube means, said stream having a central portion and an outer portion both flowing in the same direction at substantially the same speed as a single stream,
(c) droplet means for producing droplets from said liquid solution,
(d) means coupling said droplet means to said tube means for introducing said droplets into said central portion of said stream for said droplets to be conveyed in said central portion,
(e) means for heating said droplets and said carrier gas in said tube means,
(f) said tube means being sufficiently long for substantially all of the water in said droplets to evaporate into said carrier gas and to disperse therein, leaving substantially dried particles of said solids,
(g) torch means connected to said tube means for receiving said inner and outer portions of said carrier gas stream and said dried particles, and means for producing a plasma in said torch means to vaporize said particles for analysis,
(h) said tube means being of inner diameter substantially larger than said central portion, for allowing water vapor removed from said particles to disperse away from said particles into said outer portion of said stream, to reduce the concentration of water vapor in the immediate vicinity of said particles.

5 more elements

Dependencies are inferred from the claim text.

Apparatus and method for liquid sample introduction

Life of this patent

Apparatus and method for liquid sample introduction

Life of this patent

Abstract

Claims58