US 4,935,624 A · Thermal-assisted electrospray interface (TAESI) for LC/MS

Abstract

A Thermal-Assisted Electrospray Interface (TAESI) used in series between a liquid chromatograph and a mass analyzer gives increased sensitivity for detection of components in a liquid stream at high flow rates up to 2 milliliters per minute. Liquid exiting the liquid chromatograph is sprayed through a stainless steel capillary tube while being heated externally and under an applied voltage of about 3 KV. The combination of thermal energy and electric field potential disperses the liquid into a fine mist which is then directed at atmospheric pressure into the ionization chamber of a mass spectrometer. Such a system, optionally may additionally contain a high velocity gas flow neubulization means. The TAESI interface may be used without the electric field; however at flow rates of from 500 to 1000 .mu.L/min the use of both electric field and thermal energy increases the sensitivity by two orders of magnitude over the interface used without the electric field.

Claims24

Dependent claims

Apparatus for forming ions at atmospheric pressure from trace sample molecules in a liquid and for introducing said ions into a mass analyzer, comprising:

(a) a chamber,
(b) a conductive capillary tube to receive said liquid and having a first free end within said chamber,
(c) a thermal energy means for heating the liquid in the tube said thermal energy means extending substantially the length of the tube within the chamber,
(d) an orifice plate having an orifice therein, said tube being located on one side of said orifice plate in said chamber with said free end spaced therefrom said orifice defining an outlet from said chamber,
(e) a mass analyzer on the other side of said orifice plate, outside said chamber for receiving ions passing through said orifice plate,
(f) and means for generating an electronic field between said first free end and said orifice plate,
(g) the pressure in said chamber being substantially atmospheric pressure,
wherein the combination of said thermal energy and said electric field applied to liquid merging from the free end of said conductive tube produces a mist of finely charged droplets of said liquid so that said charged droplets evaporate in said chamber and release ions therefrom;
said droplets having a predominance of singly charged ions relative to multiply charged ions and having a single polarity, either positive or negative, the same as the polarity of the applied electric field.

6 more elements

Apparatus for forming ions at atmospheric pressure from trace sample molecules in a liquid and for introducing said ions into a mass analyzer, comprising:

(a) a chamber;
(b) a conductive capillary tube to receive said liquid and having a first free end within said chamber;
(c) a thermal energy means for heating the liquid in the tube;
(d) a gas flow nebulization means which comprises:
(1) an outer tube encircling said conductive capillary and defining therewith a narrow annular space therebetween, said outer tube having a second free end located substantially at said first free end, said second free end also being in said chamber, and
(b 2) means for directing a flow of gas through said annular space in the direction of the liquid flow for said gas to flow over said first free end into said chamber at a velocity sufficient to nebulize said liquid;
(e) an orifice plate having an orifice therein, said capillary tube being located on one side of said orifice plate with said free end spaced therefrom, said orifice defining an outlet from said chamber;
(f) a mass analyzer on the other side of said orifice plate outside said chamber for receiving ions passing through said orifice plate, and
(g) means for generating an electric field between said first free end and said orifice plate;
wherein the pressure in said chamber is substantially atmospheric pressure and wherein the combination of said thermal energy, said electric field and said nebulization produces a mist of finely charged droplets of said liquid so that said charged droplets evaporate in said chamber and release ions therefrom;
said droplets having a predominance of singly charged ions relative to multiply charged ions and having a single polarity.

8 more elements

A method of forming in a chamber at atmospheric pressure ions from trace sample molecules in a liquid and for introducing said ions into a mass analyzer, comprising:

(a) directing said liquid through a conductive capillary tube having a free end to produce an aerosol jet of droplets emerging at said free end in said chamber;
(b) heating the capillary tube within the chamber at a temperature sufficient to maintain the temperature of said aerosol jet of droplets at a temperature from about 20.degree. C. to 150.degree. C. when the flow rate of the liquid entering the capillary tube is from about 100 .mu.L/minute to 2000 .mu.L/minute;
(c) directing an annular jet of gas past said free end of said capillary tube in said chamber in the direction of flow of said liquid to nebulize said liquid;
(d) maintaining the pressure in said chamber at substantially atmospheric pressure;
(e) applying an electric field in said chamber between said free end and an orifice plate for said ions, the combination of said heating, said electric field and said nebulization acting to produce a mist of charged droplets and to produce ions from said droplets;
said charged droplets having a predominance of singly charged ions relative to multiply-charged ions and having a single polarity, either positive or negative, the same as the polarity of the applied electric field;
and
(f) guiding said ions through said orifice into a mass analyzer located beyond said orifice.

5 more elements

Dependencies are inferred from the claim text.

Thermal-assisted electrospray interface (TAESI) for LC/MS

Life of this patent

Thermal-assisted electrospray interface (TAESI) for LC/MS

Life of this patent

Abstract

Claims24