JP3075178B2 - Gas chromatograph - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a gas chromatograph.

[0002]

2. Description of the Related Art Conventionally, in order to set a split ratio to a predetermined value when performing a gas chromatographic analysis by a split method, it is necessary to set a column flow rate, a split flow rate, and a purge flow rate.

[0003]

Conventionally, the column flow rate is directly measured by using a flow meter, or calculated by measuring the retention time of methane, and the split flow rate and the purge flow rate are directly measured by the flow meter. . Since such a flow rate measurement is complicated, it takes a long time to set the split ratio.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a gas chromatograph apparatus capable of easily setting a split ratio to an arbitrary value. It is in.

[0005]

According to the present invention, there is provided a gas chromatograph apparatus comprising: a) a carrier gas flow rate adjusting means for adjusting a flow rate of a carrier gas flowing into a sample injection section; b) split flow rate adjusting means for adjusting the flow rate of the gas split out from the sample injection section; c) a pressure sensor for detecting the pressure at the column inlet; d) column length and column inner diameter corresponding to the type of column E) means for inputting the type of column; f) means for inputting the set column temperature and the set column inlet pressure; g) the input set column temperature and the set column inlet pressure are stored in advance. Means for calculating the column flow rate from the data of the column length and the column inner diameter, and h) a split so that the value detected by the pressure sensor becomes the set column inlet pressure. Thereby adjusting the flow rate, it is characterized in that a control means for adjusting the carrier gas flow rate as a split ratio is the ratio of the column flow and split flow is set split ratio.

The flow rate of the gas flowing through the column can be derived hydrodynamically from the column length / inner diameter, the gas temperature and the gas pressure at the column inlet (of course, experimentally corrected values may be added to further increase the accuracy). May be). Therefore, by providing the column temperature (which is considered to be equal to the gas temperature) set at the time of gas chromatographic analysis, data on the column inlet pressure, and data on the length and inner diameter of the column to be used, the column flow rate calculation means g can calculate the column flow rate Uc.

[0007] The column flow rate Uc is determined and the split ratio S
Is set, the total flow U of the carrier gas becomes [(1+
S) · Uc]. Accordingly, the control means h uses the split flow rate adjusting means b so that the split flow rate becomes S · Uc so that the detection value of the pressure sensor c becomes the set column inlet pressure.
By controlling the total flow rate of the carrier gas to U using the carrier gas flow rate adjusting means a, the column flow rate becomes constant at Uc, and the split ratio is maintained at the set value S. Is done.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas chromatograph apparatus according to one embodiment of the present invention will be described with reference to FIG. The gas piping system of the gas chromatograph apparatus of the present embodiment includes a sample injection section 1 provided at an inlet of a column 15 and a sample injection section 1.
A carrier gas piping system for introducing a carrier gas into the column 1 and a part of the sample injected into the sample injection section 11
5 and a purge piping system for discharging components released by the rubber of the sample injection unit 11 for discharging without discharging to the sample injection unit 11.

The carrier gas piping system is provided with a mass flow controller 10 for controlling the flow rate U (total flow rate) of the carrier gas to an arbitrary value. Note that the mass flow controller 10 includes a laminar flow element 20 and a differential pressure sensor 21 for detecting the carrier gas flow rate U, and a flow rate control valve 22 for adjusting the carrier gas flow rate U. Split flow rate U for split piping system
A control valve 14 for controlling s is provided, and a pressure sensor 12 is provided in the purge piping system. Since there is almost no gas resistance between the pressure sensor 12 and the sample injection unit 11, the pressure detected by the pressure sensor 12 can be identified with the pressure in the sample injection unit 11, that is, the column inlet pressure.

The gas chromatograph of this embodiment further includes a control unit 16. The control unit 16 controls the above-described units of the gas chromatograph device so that the split ratio becomes a set value using various parameters described later input from the ghee board 17 or an external storage device (not shown). . Control unit 1 for performing such control
Before explaining the operation of No. 6, the basic principle for split ratio control in a gas chromatograph will be described.

The gas flow rate of the column 15 depends on the length L, the inner diameter D, the gas temperature T and the gas pressure P of the column 15.
Here, the gas pressure P can be represented by the pressure at the column inlet. Given these values,
The gas flow rate Uc of the column 15 is calculated as follows based on the fluid dynamics theory.

Uc = f (T, D, L, P) (1) Here, the function f (T, D, L, P) can be theoretically obtained from the fluid dynamics and the physical properties of the gas used. Can be determined by a method of experimentally determining various coefficients of a basic expression derived from fluid dynamics.

Since the specifications (length, inner diameter, etc.) and temperature of the purge piping system are not changed, the flow rate (purge flow rate) Up
Depends only on the gas pressure P, and is calculated as Up = g (P) (2). This function is also the function f (T, D, L,
P) can be determined in the same manner.

The split flow Us can be calculated from the column flow Uc and the split ratio S as follows: Us = S · Uc (3)

Since the flow rate U of the carrier gas is the sum of the column flow rate Uc, the purge flow rate Up, and the split flow rate Us, U = Uc + Up + Us = Uc + Up + S.Uc = (1 + S) .f (T, D, L, P) + g (P)... (4)

Accordingly, the length L0 of the column 15 and the inner diameter D
In order to set the split ratio S of the gas chromatograph device to an arbitrary value S0 when given the temperature 0, the temperature T0, and the column inlet pressure P0, from the equation (4), U0 = (1 + S0) · f (T0, D0, L0, P0) + g (P0) (5) In order to satisfy the relational expression
Should be set.

For this reason, the control section 16 controls the split ratio to an arbitrary set value S0 in the following procedure. First, the operator inputs the column temperature T from the keyboard 17.
Data of 0, the set column inlet pressure P0 and the set split ratio S0 are input, and the type of the column 15 to be used is input. The control unit 16 reads the column length L0 and the column inner diameter D0 stored in advance from the input column type, and reads these data and the previously input column temperature T0,
Based on the set column inlet pressure P0, the column flow rate Uc0 = f (T0, D0, L0, P0) is calculated by equation (1), and the total flow rate U0 of the carrier gas is calculated by (5). First, the detection value P of the pressure sensor 12 is set to the set value P
The opening of the control valve 14 is adjusted so as to be constant at zero. Thereby, the purge flow rate Up0 = g (P0) becomes constant, and the column flow rate Uc0 = f (T0, D0, L0, P
0) is also constant (when the temperature is constant). Therefore, by controlling the mass flow controller 10 so that the carrier gas flow rate becomes U0, the split flow rate Us also becomes constant, and the split ratio of the gas chromatograph device is kept constant at the set value S0.

In this embodiment, even when the column temperature T changes gradually, the above calculation is performed sequentially based on the temperature value at each time point, and the target pressure value P0 and the carrier gas flow rate U0 are updated. Then, by performing the same control, the split ratio can always be kept constant.

Here, since the column inlet pressure P can be derived from the column average linear velocity vm, the keyboard 17
May be set as the average linear velocity vm0 and the split ratio S0. More generally, the average linear velocity vm,
If any one parameter of the column inlet pressure P and the purge flow rate Up and any one parameter of the total flow rate U and the split ratio S are determined, the other parameters can be derived from them. Can be any combination of the above.

In the above-described embodiment, the values of the column inlet pressure P0 and the split ratio S0 are input from the keyboard 17, but the standard values are stored in the control unit 16 in advance, and You may make it select from. Regarding the column temperature T0, it is preferable to automatically supply temperature data to the control unit 16 from an analysis control device or the like according to the analysis mode.

An application example of the gas chromatograph of the above embodiment will be described below. One is that this gas chromatograph device performs total analysis in addition to split analysis. Conventionally, an apparatus for split analysis and an apparatus for total amount analysis were separately prepared. However, in the gas chromatograph apparatus of the present embodiment, the control valve 14 was completely closed and the value detected by the pressure sensor 12 was changed. By adjusting the flow control valve 22 of the mass flow controller 10 so that P becomes the set value P0, the total amount analysis can be performed. Therefore, when 0 (zero) is input as the value of the set split ratio S0 from the keyboard 17, or when an instruction for the full volume analysis is given, the program of the control unit 16 is set in advance to perform such control. By doing so, it is possible to switch between the split analysis and the total analysis only by simple key input.

Another application is to appropriately change the split ratio during a single analysis to save carrier gas. That is, since the purpose of the split is to split the sample injected into the carrier gas, only the carrier gas is split out before injecting the sample or after the sample is sent to the column, It is a waste of carrier gas. In particular, when most parts are split out, such as when the split ratio is 1: 100, this waste is large. When the gas chromatograph device of the present embodiment is used, the control unit 1
6 changes the split ratio S during one analysis as follows. First, the split ratio is set to the input set value S0.
The mass flow controller 10 and the control valve 14 are controlled so as to be (for example, 100), and the sample is injected when the flow rate is stabilized. After the sample is injected, the set split ratio S0 is maintained for a predetermined time (for example, about 1 minute) set as a value larger than the time required for the sample to be sent to the column 15, but when the predetermined time elapses By setting the split ratio to a small value S1 (for example, 5), the amount of the carrier gas split out is greatly reduced.

[0023]

According to the gas chromatograph apparatus of the present invention, the split analysis can be performed at an arbitrarily set split ratio without a troublesome operation of actually measuring the column flow rate and the split flow rate.
In addition, as an application, split analysis and total analysis
It can be easily used by two different instruments, and by appropriately changing the split ratio during one analysis,
Waste of carrier gas can be prevented.

[Brief description of the drawings]

FIG. 1 is a piping diagram of a gas chromatograph apparatus according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Mass flow controller 11 ... Sample injection part 12 ... Pressure sensor 14 ... Control valve 15 ... Column 16 ... Control part 20 ... Laminar flow element 21 ... Differential pressure sensor 22 ... Flow control valve

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-262964 (JP, A) JP-A-2-242150 (JP, A) JP-A-3-18756 (JP, A) JP-A-3-262 115972 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 30/10 G01N 30/32 G01N 30/86

Claims (1)

(57) [Claims] 1. A split type gas chromatograph apparatus comprising: a) carrier gas flow rate adjusting means for adjusting a flow rate of a carrier gas flowing into a sample injection section; and b) adjusting a flow rate of a gas split out from the sample injection section. Split flow rate adjusting means; c) a pressure sensor for detecting the pressure at the column inlet; d) means for storing a column length and a column inner diameter corresponding to the type of the column; e) means for inputting the type of the column F) means for inputting a set column temperature and a set column inlet pressure; and g) calculating a column flow rate from the input set column temperature and set column inlet pressure and data of a column length and a column inner diameter stored in advance. H) adjusting the split flow rate so that the value detected by the pressure sensor is equal to the set column inlet pressure; Gas chromatography apparatus, characterized in that it comprises a control means for adjusting the carrier gas flow rate as a split ratio is set split ratio is the ratio of the Tsu bets flow.