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AssigneeThermo Finnigan Italia S.p.A.
InventorsPaolo Magni, Thomas Porzano
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Abstract of the Disclosure This invention concerns a method and apparatus for vaporization injection of large volumes of liquid sample (substance to be analysed + solvent) introduced by means of the needle of a syringe onto a heated vaporization chamber which is part of an injector applied to a device for gas chromatographic analysis, the sample being sent in form of a liquid band travelling through said vaporization chamber at high speed until reaching stopping and vaporization means positioned adjacent to the inlet of a capillary to collect the vapours. In order to inject large volumes without modifying the vaporization chamber and without samples parts losses, in splitless mode, a drawing up of the sample vapours from the vaporization chamber into said capillary is made by means of a local action of volume contraction, caused by recondensation of at least the solvent vapours in this capillary, said capillary being in the form of a pre-column with no stationary phase, maintained at low temperature at least during the injection.
A method for vaporization injection of large volumes of liquid sample (substance to be analysed + solvent) introduced by means of the needle of a syringe onto a heated vaporization chamber which is part of an injector applied to a device for gas chromatographic analysis, the sample being sent in form of a liquid band travelling through said vaporization chamber at high speed until reaching stopping and vaporization means positioned adjacent to the inlet of a capillary to collect the vapours, characterized by a drawing up of the sample vapours from the vaporization chamber into said capillary by means of a local action of volume contraction, caused by recondensation of at least the solvent vapours in this capillary.
A method as claimed in claim 1, characterized by the choice of said capillary in the form of a pre-column with no stationary phase, maintained at low temperature at least during the injection.
A method as claimed in claim 2, in which the injector has an inlet for the carrier gas, characterized in that said pre-column is maintained at a temperature below the dew point of the sample vapours/carrier mixture, at the carrier pressure.
A method as claimed in claim 2 or 3, characterized in that said pre-column has an internal surface sufficient to retain the recondensed sample.
A method as claimed in claim 2, 3 or 4, characterized in that the increase of temperature program of the pre-column starts after evaporation of the solvent in said pre-column has terminated.
A method as claimed in one of the previous claims, characterized by feeding the carrier during injection in flow and pressure conditions substantially equal to those foreseen during the gas chromatographic analysis.
A method as claimed in one of the previous claims, characterized in that the sample is sent through the injector as a liquid band, employing conditions that substantially avoid its vaporization in the needle.
A method as claimed in at least one of the previous claims, characterized in that the injection is performed in splitless mode and the injection sample has a volume greater than 5 µl.
A method as claimed in at least one of the claims from 1 to 8, applied to gas chromatography with narrow bore columns, characterized in that the injection is performed in splitless mode.
A method as claimed in claim 10, characterized in that the injected sample has a volume greater than 0.5 µl.
A device for gas chromatographic analysis of samples (substance to be analysed + solvent), composed of an injector (11) of the vaporization type, a gas chromatographic column (13) housed in an oven (15) and a detector (17), in which the injector (11) comprises a heated chamber (6) with a septum (1), which can be penetrated by a needle (14) for fast injection of the sample in the form of a liquid band, the chamber also having a stopping and vaporization means (7) for the band adjacent to the inlet of a capillary for collecting the vapours and sending them to the separation column (13) and a duct (5) for feeding the carrier gas, characterized in that said capillary is in the form of a pre-column (9) not coated with stationary phase, positioned between the injector (11) and the separation column (13).
A device as claimed in claim 12, characterized in that the vaporization chamber (6) has means (12) to heat the same, positioned and operating so that the temperature profile on the longitudinal axis of the injector (11) is such that the part in which the needle (14) of the syringe penetrates is heated only slightly and the subsequent part is sufficiently hot to repel the liquid from the walls due to the formation of a vapour buffer.
A device as claimed in claim 12 or 13, characterized in that the stopping and vaporization means (7) is composed of a packing with a volume at least double of the injected volume.
A device as claimed in claim 14, characterized in that the packing (7) is made of glass wool, fused silica or similar deactivated materials.
A device as claimed in claim 12 or 13, characterized in that the stopping and vaporization means (7) is composed of obstacles.
A device as claimed in claim 12 or 13, with a duct (3) to purge the septum by means of the carrier, characterized in that in comprises means to close or choke said septum purging duct.
A device as claimed in claim 12, characterized in that no filter is provided between the vaporization chamber (6) and the splitting control valve (16).
A device as claimed in claim 12 or 13, characterized in that a filter is interposed between the valve for splitting closure and the valve for splitting control.
Dependencies are inferred from the claim text.