JPH11201960A - Gas chromatograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a gas chromatograph in which mutual reference of a holding time between analyzed results of a plurality of devices is performed easily, by displaying the corrected holding time which is calculated on the basis of the value of the holding time in every analysis of one or a plurality of identical reference substances. SOLUTION: A gas chromatograph is provided with a computing part 8 which measures and computes a holding time of every peak as qualitative information and which contains an A/D converter and a computer. Then, by using a device to be used as a reference, e.g. a reference substance N, a component X to be measured, and a sample which contains methane M as a substance hardly interacting with a measuring column are analyzed. The relative holding time Tx =(tx -tm )/(tn -tm ) of the component X is found on the basis of a holding time tx , a holding time tn and a holding time tm . Regarding other devices under the same condition, the relative holding time is found in the same manner. When the difference between the respective devices is within a prescribed range, the holding time of all components X to be measured is multiplied by a prescribed identical correction factor, and the holding time is corrected between the devices. When the difference is outside the prescribed range, a correction factor which is different for every component X to be measured is used. In addition, when the difference is large, the holding time is judged to be abnormal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In gas chromatography, component peaks are usually identified based on retention times.
However, the retention time in gas chromatography, unlike the wavelength in mass spectrometry or the mass number in mass spectrometry, is not a value that is uniquely determined based on the physical properties of the component substances. It depends on a number of factors, such as the type, pressure and flow rate, and even the differences in equipment. Therefore, even if the same analysis conditions are set, it is naturally considered that the retention time of each component peak differs to some extent depending on the device and the column, but at present, this is the case in gas chromatography. This makes identification of the components difficult. In addition, even if the same analysis is performed by unifying the analysis conditions with multiple gas chromatographs, the results will not be the same, that is, there is no cross-sectional data,
In a routine analysis, when a column is replaced with a new one or an instrument is updated, various problems occur such that continuity with previous data cannot be obtained.

[0003] Therefore, in order to eliminate these fluctuation factors as much as possible, the relative retention time has been used for component identification. This represents the retention time of each component peak as a ratio to the retention time of a predetermined reference substance, and is actually obtained by the following procedure.

First, a substance M having little interaction with the column (methane gas is often used) is introduced as a sample, and its retention time t _m is measured. Next, a standard sample containing a reference substance N (this is a substance similar to the component substance to be measured and which can obtain a stable peak without being affected by adsorption or the like by the column) is introduced. , Its retention time t _n is measured. Subsequently, the sample to be measured is introduced, and the retention time t _x of the measurement component X (there are generally a plurality of measurement components, but only one for simplicity in this case) is measured. The relative holding time _Tx is calculated.

T _x = (t _x −t _m ) / (t _n −t _m ) (1) If the relative retention time is used, for example, the column changes over time and the component X Even when the retention time changes, the value of the relative retention time represented by these ratios hardly changes since the reference substance N also changes almost proportionally, so that there is no significant problem in peak identification. become.

[0006]

As described above, when the same analysis is carried out by a plurality of apparatuses, the retention time is different for each apparatus even if the analysis conditions are set to be as identical as possible using the same type of column. Therefore, identification based solely on the retention time has a high possibility of error. It is necessary to identify individual peaks in comparison with standard data, taking into account the sequence of the peaks and the pattern of the entire chromatogram, which is a difficult task for an inexperienced operator. This is also a problem when identification is performed automatically.

[0007] Even if an attempt is made to solve this problem by using the relative retention time, the relative retention time is a relative value, and the value changes when the reference material is changed. That is, the lack of universality is a disadvantage. In fact, most of the standard analytical data published by column manufacturers or the analytical data published in research presentations etc. are displayed in real time on the time axis. I can't compare. After all, there is a strong demand to display the holding time in real time.

The present invention has been made in view of the above-described problems, and has been made in view of the analysis results of a plurality of gas chromatographs set under the same conditions, or the cross-reference of the retention time among the analysis results at different times even in the same apparatus. The purpose is to make it easier.

[0009]

In order to achieve the above object, in the gas chromatograph of the present invention, a correction calculation is performed on a value on a time axis, such as a retention time on analysis data, and a plurality of data are calculated. The difference in apparent holding time is minimized. Specifically, in each gas chromatographic analysis, the retention time of the same reference material or a plurality of reference materials is measured, and the ratio between the analysis is set as a first correction coefficient. The relative value of the retention time is obtained, and the ratio between the analyzes is used as a second correction coefficient, and the value of the retention time recalculated using these values is displayed instead of the original retention time. .

By doing so, there is almost no apparent difference in retention time between the apparatuses, so that a complicated process such as taking into account the pattern of the entire chromatogram is omitted, and each peak is determined based on the retention time alone. Can be identified, and mechanical identification using a computer or the like, and identification by an inexperienced operator can be easily performed.

[0011]

FIG. 1 shows the configuration of a gas chromatograph according to one embodiment of the present invention.

In FIG. 1, a carrier gas flowing from a cylinder 1 has a predetermined flow rate by a carrier gas flow rate control unit 2.
Alternatively, the pressure is adjusted to the pressure, and the column 4
And emitted through the detector 5. The column 4 is placed in an oven 6 and maintained at a predetermined temperature. The sample to be analyzed is injected from the sample introduction unit 3, carried by the carrier gas, separated into components while passing through the column 4, converted into an electric signal by the detector 5, and further converted by the amplifier 7.
And is output as an analysis result to the recording unit 9 via the arithmetic unit 8.

The arithmetic unit 8 is a part that characterizes the present invention, and includes an A / D converter and a computer. The arithmetic unit 8 not only processes an analysis signal to measure the height and area of a peak, which is quantitative information, but also The retention time of each peak is measured as qualitative information, and the calculation is performed using the measured time in the following procedure.

First, a standard sample containing methane, a standard substance, and a sample to be measured are analyzed by a gas chromatograph apparatus serving as a standard. These three points are usually introduced separately (ie, analyzed three times), but if possible, three points may be taken in the same syringe and analyzed at once. As a result, it is assumed that a chromatogram as shown in FIG. 2 was obtained. From this result, methane M, reference substance N, and measurement component X, and respective retention times t _m , t _n, and t _x were measured. Is used to calculate the relative holding time Tx of _X from the above equation (1).

In this equation, t _x is called a gas hold-up time, and is a value that is physically determined by the volume of the flow path in the portion of the analyzer through which the sample passes, and is almost meaningless in terms of chromatography. It is more meaningful to express this value as the space correction holding time obtained by subtracting this value from the holding time. Therefore, hereinafter, all the holding times are represented by a space-corrected holding time (the holding time after the correction is represented by t again), and a suffix 1 indicating that the measurement is performed by the reference device is added. , T _x1 = t _x1 / t _n1 ………………………………… (2)

With the second apparatus set to the same analysis conditions, the same methane, the reference substance, and the measurement sample are analyzed, the respective retention times are obtained, and the relative retention time T _{x2 is} calculated in the same manner as in equation (2).
Ask for.

T _x2 = t _x2 / t _n2 …………………………………………………… (3) The retention time t _x2 of component x in the second device is In order to newly calculate [t _x2 ] by multiplying by the coefficient K and make it coincide with the holding time t _x1 of the component x in the reference device, [t _x2 ] = Kt _x2 = t _x1 ... _{................................. (4) K = t x1} / t x2 ...................................................... (4 ') (2) (3) equation By transforming equation (4 ′) using the following equation, K = (t _n1 / t _n2 ) · (T _x1 / T _x2 ) ·············· (5) If the retention times match within a certain limit (for example, the difference is within 3%), then in equation (5), T _x1 = T _x2 ……………………………………. ............... (6) as K = t _n1 / t _n2 .......................................... ............... and since (7), (4) expression _{[t x2] = (t n1} / t n2) t x2 ....................................... (8) next, which 6 is a correction calculation formula for making the retention times of the two apparatuses seemingly identical. In other words, the retention time of each component of the second device may be recalculated using the ratio of the retention time of the reference substance in both devices as the correction coefficient, and the calculation result may be output and displayed as a new retention time. In this case, since the correction coefficient is determined only by the retention time of the reference substance, the calculation is simple because it is sufficient to multiply all the measured components by the same coefficient.

When the condition of the expression (6) is not satisfied, for example, when the difference between the relative holding times of the two devices exceeds 3%, the expression (5) is applied as the correction coefficient. In this case, since the value of the correction coefficient differs for each component, the calculation becomes complicated.

If the difference in the relative holding time between the apparatuses set under the same conditions becomes too large, for example, 10%
If the value exceeds the limit, it is assumed that some sort of device abnormality has occurred, such as column deterioration, gas leakage, gas pressure or temperature setting error, etc. Or readjustment. That is, calculating the ratio of the relative holding time between the devices is
It can be said that it is useful not only for correction calculation but also for operation management of the analyzer.

As can be seen from equation (5), the correction coefficient in the correction calculation consists of two parts, and the first correction coefficient is the first term on the right side of equation (5), that is, the ratio of the retention time of the reference material. The second correction coefficient is the second term on the right side of the equation, that is, the ratio of the relative retention time of the measurement component to the reference substance.
The value of the second correction coefficient is also a criterion for applying these correction coefficients. As described above, for example, if the second correction coefficient is in the range of 0.97 to 1.03, Apply only the correction coefficient of 1 and exceed it by 0.90 to 1.10
Within the range, the first and second correction coefficients are multiplied, and when the range exceeds this range, a warning for prompting readjustment of the apparatus is issued without performing the correction calculation.
The above numerical values that define the application limit of the correction coefficient are shown as examples, and can actually be set arbitrarily in system operation.
It is also possible to determine and operate so as to apply the second correction coefficient together.

Even when the same analysis conditions are set for three or more analyzers and used for the same analysis, the respective devices may be set in the same manner as described above to perform the correction calculation. Even when only one device is used for the same analysis purpose for a long period of time, the initial (past) analysis result and the current analysis result are regarded as being the analysis results of different devices. By performing the same correction calculation as described above, a change in the retention time due to a change over time in the column or the like is corrected, and continuity of data over a long period can be secured.

In calculating the relative holding time, etc.,
It is not always necessary to actually perform the reference analysis every time. The retention time of the peak of the reference substance or each measurement component may be read on a chromatogram of standard data published by a column manufacturer or the like, and the above calculation may be performed based on this value. In this way, the subsequent retention time on the analysis data substantially matches that of the standard data.

Although the correction calculations in the above description are all automatically performed by a computer built in the arithmetic unit 8, further, the introduction of methane gas and a standard sample is automatically performed by an autosampler. Thus, a fully automated system can be configured.

In the above description, the correction is performed by paying attention to the relative holding time. In addition, a holding index (retention index) is used as a method for making the holding time relative.
Is often used. This is an index that can be applied to a wider range including a series of a plurality of reference substances and includes a temperature rise analysis, and other methods for making the retention time relative can be considered. The present invention can be applied to a case where this retention index or another relative retention value is used instead of the relative retention time.

[0025]

As described in detail above, the present invention provides
The retention time of the same reference material or reference materials is measured by an apparatus or by a plurality of gas chromatographic analyzes at different times, and the ratio between the analyzes is used as a first correction factor. The relative value of the retention time of each measurement component is determined, and the ratio between the analyzes is used as a second correction coefficient, and the value of the retention time recalculated using these is displayed instead of the original retention time. As a result of this correction calculation, the values of the retention times on each analytical data almost match, so that it is easy to identify each component peak by mutually referencing the data,
In addition, traversability and continuity of data can be secured. Moreover,
Since the retention time is displayed in real time rather than a relative value, cross-reference with generally published data is also easily possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 An example of a chromatogram

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carrier gas cylinder 2 Carrier gas flow control part 3 Sample introduction part 4 Column 5 Detector 6 Oven 7 Amplifier 8 Operation part 9 Recording part

Claims (1)

[Claims] An apparatus or a plurality of gas chromatographic analyzes at different times, each measuring a retention time of the same one or a plurality of reference substances, a ratio between the analyzes as a first correction coefficient, The relative value of the retention time of each measurement component with respect to these reference substances was determined, and the ratio between the analyzes was used as a second correction coefficient, and the retention time was recalculated by appropriately applying these correction coefficients according to a certain standard. A gas chromatograph in which the value of is displayed instead of the original retention time.