JPH0524459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a gas chromatograph mass spectrometer, and particularly to the configuration of a sample introduction system of a gas chromatograph mass spectrometer.

B. Conventional technology In a gas chromatograph mass spectrometer, a molecular separator is inserted between the chromatograph and the mass spectrometer to remove a carrier gas from the outflow gas of the gas chromatograph, concentrate sample components, and introduce them into the mass spectrometer. It's getting old. A jet type molecular separator is used as a molecular separator.
There is an optimum gas flow rate, and when a packed column is used in a gas chromatograph, it operates efficiently; however, when a capillary column is used, it cannot operate efficiently because the flow rate of the carrier gas is small. In addition, in the case of a capillary column, there is a concept that there is no need for a special concentration process because the carrier gas is small. It was being introduced into an analyzer.

By the way, a jet-type molecular separator is a T-shaped tube when viewed from the tubular shape, and a side tube is pulled out from the middle of the tube that connects the gas chromatograph and the mass spectrometer and is connected to the exhaust pump. Most of the gas flowing out from the chromatograph is sucked in through this side pipe, and only a portion is introduced into the mass spectrometer.By adding a valve mechanism to the molecular separator, this gas flowing out from the chromatograph can be absorbed. The function of drawing out to the side channel is used to draw out the solvent (solvent for dissolving the sample) flowing out of the chromatograph into the side channel so that it does not flow into the mass spectrometer. The solvent is quantitatively larger than the sample components, and when it enters the mass spectrometer,
Solvents that flow out of the chromatograph are prevented from flowing into the mass spectrometer because this often causes undesirable effects such as accelerating the deterioration of the filament and heater of the ion source of the mass spectrometer and contaminating the internal surface of the mass spectrometer. This type of technique is called solvent cutting, but this solvent cutting is not possible if the capillary column is directly connected to a mass spectrometer.

Even when a capillary column is used, a method has been implemented in which sample components are introduced into a mass spectrometer through a jet-type molecular separator. In this method, a carrier gas is added to the column effluent gas until it reaches an appropriate flow rate for the jet-type molecular separator, and the gas is passed through the molecular separator. Originally, when using a packed column, the sample component yield of the jet-type molecular separator was 30%. %, so in the current case where the sample component concentration is diluted more than that, the yield of the sample component will be lower and the loss of the sample will be large.

C. Purpose The main object of the present invention is to enable solvent cutting when a capillary column is applied to a chromatograph and directly connected to a mass spectrometer.

D. Configuration The first stage capillary column and the flow path resistance are connected by a T-shaped tube, the flow path resistance is directly connected to the ion source of the mass spectrometer, and a branch pipe of the T-shaped tube is connected to the exhaust system. The flow path resistance described above may be a simple resistance tube, or may itself be a capillary column. The branch pipe of the T-tube is connected to the exhaust system through a variable resistance control valve such as a needle valve, a bypass is provided to this control valve, and an on-off valve is inserted into this bypass, and when the solvent flows out, this on-off valve is closed. Open and rapidly aspirate the solvent.

E. Embodiment FIG. 1 shows an embodiment of the present invention. 1 is a front column, and 2 is a rear column, both of which are capillary columns, and both are connected in series by a T-tube 3, and a sample introduction chamber 4 is connected to the front column 1.
The latter column is directly connected to the ion source 6 in the mass spectrometer 5. In this embodiment, the mass spectrometer 5 is a quadrupole type, and 7 is a quadrupole electrode rod and 8 is an ion detector. A branch pipe of the T-shaped pipe 3 is connected to an exhaust pump 10 via a solenoid valve 9. This solenoid valve is open while the solvent is flowing out from the capillary column 1, and the solvent is removed by suction by the exhaust pump 10. When the solenoid valve 9 is closed, the T-shaped pipe 3 and the branch pipe become a dead space, so a variable needle valve 11 is provided in parallel with the solenoid valve 9 to constantly exhaust the T-shaped pipe 3.

FIG. 2 is an enlarged view of the T-tube 3. The front column 1 and the rear column 2 are each inserted into a T-shaped tube.

Returning to FIG. 1, 14 is a heating tank that houses the columns 1 and 2, the sample introduction chamber, etc., and the sample introduction chamber 4 is filled with carrier gas from the carrier gas reservoir 12.
He is supplied through a pressure regulating valve 13.
In this example, a column that is slightly thicker than a normal capillary column (inner diameter of 0.3 mm or more, compared to the usual 0.25 mm or less) is used as the first column 1, and the sample solution is directly injected into the column by inserting the needle of a microsyringe into the capillary column. The sample is introduced using the column injection method, which vaporizes the sample. The carrier gas flow rate in front column 1 is approximately 2 ml/min, whereas the gas flow rate in rear column 2 is approximately 1 ml/min.
ml/min, approximately half of which, 1 ml/min, is removed by suction in the T-tube 3 through the needle valve 11. T
Since the double tube 3 does not have the function of concentrating sample components, in this example, half of the sample components are lost, but the sample concentration is better than adding a carrier gas and concentrating the sample components with a jet-type molecular separator. Good rate.

Effects According to the present invention, a T-shaped pipe is provided between the front column and the rear column and the branch pipe is connected to the exhaust system. Just open the valve. At this time, due to the resistance of the latter column, the gas flowing out of the former column is discharged through the branch pipe without flowing into the latter column. This is because when the electromagnetic valve is opened, the pressures before and after the rear column are both 0 atmospheres and are substantially equal, so the gas flow in the rear column is stopped. If you try to perform a solvent cut without a post-column, you will need to install an on-off valve in the pipe connecting the column and the mass spectrometer, install a branch pipe in front of the on-off valve, and close the on-off valve to exhaust the air from the branch pipe. Otherwise, there will be many technical difficulties such as contamination of the on-off valve by the solvent and problems with dead space caused by providing the on-off valve, so it is significant to provide a T-shaped pipe between the front column and the back column.

Furthermore, according to the present invention, the high vacuum inside the mass spectrometer can be maintained even if the front column is removed from the T-tube 3 due to the resistance of the rear column. 1 can be exchanged.

Furthermore, since gas can be removed through the branch pipe, even if a column with a large gas flow rate and a large amount of sample introduced into the front column is used, the amount of sample introduced into the mass spectrometer can be adjusted to an appropriate amount. In addition to ordinary capillary columns, thicker columns, micropacked columns, etc. can be used for this purpose, giving a great degree of freedom in column selection.

[Brief explanation of the drawing]

FIG. 1 is a pipe line diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a T-shaped pipe in the above embodiment. 1...First column, 2...Last column, 3...
T-tube, 4...sample introduction chamber, 5...mass spectrometer,
9... Solenoid valve, 10... Exhaust pump, 11... Needle valve for flow rate adjustment, 12... Carrier gas reservoir,
14... Heating tank.

Claims (1)

[Claims] 1 Connect the front column of the gas chromatograph and the flow resistance in series via a T-shaped tube, connect the flow resistance directly to the ion source of the mass spectrometer, and connect the branch pipes of the T-shaped tube through the on-off valve. A gas chromatograph mass spectrometer, characterized in that the gas chromatograph mass spectrometer is connected to an exhaust system and is provided with a flow control valve in parallel with the on-off valve.