JPH0484758A - Peak identification method for chromatography - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] ) Industrial applications This invention relates to analysis using chromatography.

More specifically, it relates to quantitative analysis using 46M 8-body chromatography (hereinafter referred to as HPLC), gas chromatography (hereinafter referred to as GC), ion chromatography (hereinafter referred to as 1c), and the like.

(b)) Conventional technology In HPLC, GC, IC, etc., it is possible to automatically integrate the output signal from the device and perform quantitative calculations by comparing it with a calibration curve prepared in advance. Data processing equipment has become widespread, contributing to labor savings and higher precision in analysis. At this time, peak components are identified by comparing them with the retention time input based on the data of the standard sample injected when creating the calibration curve.1 Usually, peak components elute within a certain allowable time relative to the standard retention time. The detected peak is identified as the target component.

(c) Problems to be solved by the invention However, if the loading amount of the target component in the contaminated sample differs from the loading amount at the time of analysis of the standard sample used to create the calibration curve,
It often happens that the retention time of the component peak changes with the loading amount. These changes can be roughly divided into two cases: a case where the holding time becomes shorter as the load increases, and a case where the holding time becomes longer. In the former case, a so-called tilling peak is given, and in the case of VK, a rising peak is given, but the retention time of these peaks is limited.

Since the holding time is significantly different from the holding time when no peak deformation occurs, depending on the degree of deformation, the permissible time may be exceeded.

Peaks will no longer be correctly identified.

(b) Means for Solving the Problem The inventor of this invention quantitatively grasped the change in retention time accompanying the change in sample load.

It has been found that the predicted retention time can be calculated as a function of the peak area obtained as the integral value of the output signal from the chromatograph.

According to the present invention, in a chromatography system in which the retention time changes as the sample load changes, the predicted retention time calculated based on the peak area can be used as an identification index. In order to predict the retention time, the retention time is expressed as a function of peak area from the analysis results of at least two standard samples with different concentrations.

When converting into a function, it is assumed that the retention time can be expressed linearly as the square root of the peak area.

Namely.

In the equation of retention time = ax (peak area)'' + b - (]), determine the coefficients a and b, and calculate the arbitrary peak area (
That is, the predicted holding time under load t) is calculated. The reason for assuming that the retention time can be expressed linearly by the square root of the peak area is that tilling peaks and idling peaks generally exhibit a shape close to a triangle. Additionally, if the relationship between retention time and peak area is known due to reasons such as the chromatography thread being fixed, illegality can be used automatically by inputting the functional formula into the data processing device in advance. .

(e) Last month, according to this invention, a chromatography system in which retention time changes with changes in sample load was introduced.

From the retention time obtained at a constant load, the retention time for any given load can be predicted.

It is possible to prevent identification errors due to changes in retention time when the load amount is changed.

(f) In Example IC, due to the specificity of the detection method, the separation of component ions is achieved by the combination K of an ion exchange resin column with extremely low exchange capacity and a low concentration electrolyte aqueous solution. For this reason, even within the dynamic range of the detector, when the amount of sample loaded is large, an overload condition a easily occurs, and changes in peak shape and accompanying changes in retention time are often observed. For this reason, the single method is replaced by γμ by IC.
An example applied to the analysis of potassium metal ions will be given as an example. Figure 1 shows Na ions at 200 ppm and ions at 40 ppm.
This is a superimposition of chromatograms obtained when a standard sample containing 0 ppmt was analyzed by changing the injection amount. Especially regarding ion peaks.

Tilling is noticeable. FIG. 2 is a calibration curve for both ions prepared based on the ridge results. both.

Good linearity is shown in this range. In Figure 3, tilling was noticeable. Graph f is drawn based on the relationship between peak area and retention time for ions. The horizontal axis is the square root of the peak area, and the vertical axis is the retention time, and it can be seen that an approximately linear relationship is obtained.

Let us now assume a case in which the conventional method is followed. If the retention time at a load of 2 μg is taken as the standard, the retention time for the ion will be approximately 6.5 minutes. Assuming that the allowable range for peak identification is 8% of the retention time (the setting value is generally about 3 to 5%, but set to a wide range), it is 5.98 minutes to 7.
．． The peak eluting at 02 minutes is identified as crab ion. However, from the ridge results, if the load amount is 10 μg or more.

It can be seen that if it is a K ion, it cannot be identified. Particularly in this case, since NH44 ion elutes immediately before ion, it will be identified as NH4 ion, and there is a high risk of misjudging the 0 analysis result.

However, it can be seen that if the present invention is converted into a function according to equation (1), ions can be stably identified regardless of the load amount. For example, the coefficient a in equation (1) was determined from the retention times at loads of 2 μg and 8 μg.

The bFi was 6.32 x 10"' and 7.03, respectively, and the predicted retention time at 16 μg calculated from these values was 5.6] minutes, which is better than the 5.69 minutes measured in the dormitory test. showed agreement.

(G) Effects of the Invention According to this invention, when performing quantitative analysis by chromatography such as HPLC, GC, IC, etc., even if the peak shape is deformed due to overload or other causes, the retention due to the peak hair shape can be achieved. The ITr function is capable of automatically correcting changes in time, and as a result, peak identification can be performed stably, which greatly contributes to improving analysis precision and saving time in analysis work.

[Brief explanation of drawings]

Claims (1)

[Claims] (1) From the analysis results of at least two standard samples with different concentrations, the retention time is expressed as a function of the peak area (formula (1) below), and retention time = a x (peak area) ^1^/^2 + b ...
(1) A peak identification method for chromatography, which comprises determining a predicted retention time at an arbitrary peak area based on the function and identifying a chromatographic peak.