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

Claim 2

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.

Claim 3

Apparatus according to claim 1 wherein said capillary tube is formed from an electrically conductive material and is positioned accept a liquid flow rate of liquid passing the tube at a flow rate of from about 100 μL/min to about 2000 μL/minute; said electric field generating means sufficient to provide an electric field of up to about 3 kV; and a thermal energy means sufficient to generate a temperature at the first free end of said capillary tube of from about 20° C. to 150° C.

Claim 4

Apparatus according to claim 2 wherein said capillary tube is a stainless steel tube and said means for generating said electrical field includes means for applying a potential to said stainless steel tube.

Claim 5

Apparatus according to claim 2 wherein the inner diameter of said capillary tube is between from about 0.025 to 0.20 millimeters.

Claim 6

Apparatus according to claim 4 wherein the inner diameter of said capillary tube is of the order of 0.1 millimeters.

Claim 7

Apparatus according to claim 4 wherein said thermal energy means applied to the liquid is selected from the group consisting of (1) electrically resistive heating (2) piezoelectric heating (3) ultrasonic heating (4) infrared heating and conductive from gas heating.

Claim 8

Apparatus according to claim 6 wherein said thermal energy means is electrical resistant heating.

Claim 9

The apparatus according to claim 7 wherein the temperature of the liquid at the first free end of said capillary tube is less than about 100° C.

Claim 10

Apparatus according to claim 2 and including a liquid chromatograph for supplying said liquid, said liquid chromatograph having an outlet tube for said liquid flowing therefrom, said outlet tube being of an insulating material and being connected to said inner tube for said inner tube to receive the entire flow from said liquid chromatograph.

Claim 13

The method according to claim 10 wherein the temperature of the aerosol jet is from about 20° C. to 150° C. and the flow rate of the liquid entering the capillary tube is from about 100 μL/minute to 2000 μL/minute.

Claim 14

The method of claim 11 wherein the temperature of the aerosol jet is less than 100° C. and the liquid flow rate is from about 500 to 1000 μ/L minute.

Claim 15

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.

Claim 16

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.

Claim 17

Apparatus according to claim 13 wherein the thickness of said annular space is of the order of 0.075 millimeters.

Claim 18

Apparatus according to claim 13 wherein said means for directing said flow of gas includes a source of pressurized gas, the pressure of said gas being between 2 and 3 bar.

Claim 19

Apparatus according to claim 15 and including a liquid chromatograph for supplying said liquid, said liquid chromatograph having an outlet tube for said liquid flowing therefrom, said outlet tube being of an insulating material and being connected to said tube for said capillary tube to receive the entire flow from said liquid chromatograph.

Claim 20

Apparatus according to claim 16 wherein said gas is nitrogen.

Claim 21

Apparatus according to claim 13 wherein said first free end of the capillary tube extends slightly beyond said second free end.

Claim 22

Apparatus according to claim 13 wherein said nebulization means includes means for producing a gas velocity of between about 140 and 250 meters per second through said annular space.

Claim 23

Apparatus according to claim 13 wherein said capillary tube is formed from an electrically conductive material and is adapted to accept a liquid flow rate of liquid passing the tube at a flow rate of from about 100 μL/min to about 2000 μL/minute; said electric field generating means sufficient to provide an electric field of up to about 3 kV; and a thermal energy means sufficient to generate a temperature at the first free end of said capillary tube of from about 20° C. to 150° C.

Claim 26

The method according to claim 21 wherein the velocity of said jet of gas is in the range between about 140 and 250 meters per second.

Claim 27

The method according to claim 21 and including the step of pre-separating components of said liquid in a liquid chromatograph prior to directing said liquid through said capillary tube.

Claim 28

The method of claim 21 wherein the capillary tube is heated at a temperature from about 150° C. to about 170° C., the temperature of the aerosol jet is less than about 100° C. and the liquid flow rate is from about 500 to 1000 μL/minute.