JPH06174709A - Processing method for chromatograph data - Google Patents

Abstract

PURPOSE:To obtain necessary and sufficient number of measuring points in an entire chromatograph by sampling measuring outputs with a sampling period of chromatograph outputs inversely proportional to a square root of number of theoretical stages of using columns and proportional to an elapsed time from the time of introducing a sample. CONSTITUTION:A selector 3 selects a reference pulse of one period from an output of a frequency divider 2 according to a command from a controller 4, and inputs it to counters 5, 6. The counter 5 continuously counts the reference pulses from the time of introducing a sample to a chromatograph, and applies information of analyzing time. A counted value of the counter 6 is compared with a predetermined value to be calculated by the controller 4, and when both coincide, a sampling pulse is output, and the counter 6 is cleared. Thus, since the period of the sampling pulse is increased as the lapse time, measuring outputs are sampled with the sampling period of the chromatograph output inversely proportional to a square root of the number of theoretical stages of using columns and proportional to the elapsed time from the time of introducing the sample.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing data in a chromatograph, and more particularly to a method of sampling measurement data of a chromatograph.

[0002]

2. Description of the Related Art In order to use a computer for data processing in a chromatograph, it is necessary to temporarily store the measurement output of the chromatograph in a memory. Conventionally, the sampling cycle of the measurement output for taking in this data has been set to an appropriate constant value (about 0.01 to 1 second) by the operator before the measurement. The shorter the sampling period is, the more accurate the peak profile can be reproduced, but the larger the required memory capacity becomes. For this reason, it is desirable to set the sampling cycle as long as possible within a necessary and sufficient range for data processing, but conventionally, the setting of this sampling cycle was left to the judgment of the operator. If the operator sets the data sampling cycle on the chromatograph, the operator's skill is required, and if the operator is unfamiliar, the setting of the cycle is confusing, and the improper setting causes insufficient sampling points. There is a problem that an accurate analysis result cannot be obtained, or the sampling cycle is too short, which unnecessarily uses a large capacity memory medium. The sharpness of the chromatographic peak is a function of the retention time of the sample components, but if the sampling period is constant, the sampling period must be set according to the sharpest peak, and overall memory capacity is too large. It was unavoidable to say.

[0003]

PROBLEM TO BE SOLVED BY THE INVENTION There is provided a data sampling method which does not rely on the intuition or skill of an operator, does not require an excessive memory capacity, and can obtain a necessary and sufficient number of measurement points over the entire chromatogram. .

[0004]

[Means for Solving the Problems] The sampling cycle of the measurement output is made longer in proportion to the time from the start of measurement depending on the type of column.

[0005]

When the theoretical plate number of the column is N, the retention time of the sample component is t, and the peak width is W, there is a relation of W = 4t / √N. That is, the peak width becomes wider as the retention time of the component becomes longer. Since the theoretical plate number N of the column is determined by the type of the column, the peak width will spread in proportion to the retention time. On the other hand, it can be considered that the number of sampling points required for data processing for one peak is the same even if the peak is narrow and wide, so the sampling period becomes longer in proportion to the time from the start of measurement, that is, the time of sample injection. Thus, the proportional constant at that time may be determined according to the theoretical plate number of the column, that is, the type of column.

[0006]

EXAMPLE FIG. 1 shows the relationship between one peak of a chromatograph and the number of sampling points, and the shape of the peak reproduced from the data of a given number of sampling points, with the dotted line representing the original peak shape and the black circles. Is the sampling point, and the broken line shows the shape of the peak reproduced by connecting these sampling points. The left side of the figure shows the case where the sampling cycle is short, and the right side shows the case where it is long. When the sampling period is long on the right side, the sharpness of the peak is lost and the peak height is reduced. As a result, the apparent peak width (half-width) is wider than on the left side. Since the half-width is proportional to the square root of the theoretical plate number N as shown in the equation described in the section of action, the apparent half-width is widened by decreasing the number of sampling points for one peak shown in FIG. FIG. 2 shows how the half width is converted into the theoretical plate number. Each data point in this case is moving averaged at three points before and after each data point in order to reduce noise. In this figure, the theoretical plate number is a relative value, and is shown based on the case where the number of sampling points is 50. When the number of sampling points is halved, the apparent half-width doubles, resulting in an apparent theoretical plate number of 1
/√2=0.71. Therefore, if the permissible amount of decrease in the number of theoretical plates is set to 20% (half-width of about 1.66 times), the number of sampling points is 30 or more. The sampling period T where the peak width is W and the number of sampling points of one peak is P is T = W / P When the above-mentioned relational expression between W and the theoretical plate number N is used, T = 4t / P√N When the lower limit of the number of sampling points is set to 30, the above equation is T = t / 7.5√N. The theoretical plate number N of the column is about 10,000 plates, and FIG. 3 shows the relationship between the retention time of the sample component and the sampling period when the theoretical plate number N = 10000. As shown in FIG. 3, the sampling period linearly increases with respect to the holding time, that is, the elapsed time from the time of sample injection.

FIG. 4 is a block diagram showing the functions of essential parts of the chromatographic data processing apparatus for carrying out the method of the present invention. Reference numeral 1 is a clock pulse generator, 2 is a multi-stage frequency divider, and several reference pulse signals having different periods are output from each stage. A selector 3 is a command from the control circuit 4, which selects a reference pulse of one cycle from the output of the frequency divider,
Input to the second counters 5 and 6. The first counter 5 continuously counts reference pulses from the time when the sample is introduced into the chromatograph and gives information on the analysis time. When the count value of the counter 2 is compared with a predetermined number calculated by the control circuit 4 and they match each other, a sampling pulse is output and the second counter 6 is cleared. In this way, the cycle of the sampling pulse becomes longer with the lapse of time. When the operator inputs the theoretical stage number of the column to be used by the keyboard 7, the controller 4 accordingly instructs the selector 3 to instruct the frequency divider 3 to output a reference pulse having an appropriate period from the output of the frequency divider 2. To choose.

Assuming that the theoretical number of columns in the column is 10,000, as shown in FIG. 3, the sampling period is 0.
It takes 0.2 seconds after 1 or 2 minutes and 2 seconds after 20 minutes. At this time, when a pulse having a period of 0.001 seconds is selected as the reference pulse, the count value of the second counter 6 is 100 for comparison in order to set the sampling period to 0.1 second. When the count value reaches 100, a sampling pulse is output and the counter 6 is cleared. When the counter 6 outputs a sampling pulse here, a certain value is added to the comparison number. This certain value is determined as follows. The sampling cycle is 0.1 when the sample is introduced for 1 minute, the number of comparisons is 100, the sampling cycle after 2 minutes is 0.2, and the comparison number is 200. On the other hand, the continuous count value from the time of sample introduction by the first counter 5 is 60000 after 1 minute,
Since it is 120,000 after 1 minute, the comparison number is a value obtained by multiplying the count value of the first counter by 1/600. This relationship is the same regardless of which cycle is selected as the reference pulse, and when the number of theoretical stages becomes 40000 times 40000, the reference pulse cycle is only 0.0005 seconds, which is 1/2 of the above example.

FIG. 5 is a flowchart of the operation of the control device 4. The operator sets the theoretical number of columns used, the analysis time, etc. (a). The control unit selects (B) one of the outputs of the frequency divider 2, sets the comparison number to 600 (C), and waits for sample introduction (D). When the sample introduction is detected,
Start the counting of the second counter (e),
(F). The count of the second counter is compared with the comparison number (G), and if they match, a sampling pulse is output (H).
Then, the second counter is cleared (re), the number of comparisons is set to the count of the first counter x 1/600 (nu), and it is checked whether the count of the first counter is equal to or greater than the first predetermined number. ),
If NO, the operation immediately returns to (F), and if YES, a sampling pulse is output (E), and whether or not the count of the first counter reaches the second set number determined by the analysis time and the reference pulse period. Check (wa), return to (f) if NO, end analysis operation if YES. First
The reason why the count of the counter coincides with the first predetermined number is to check that the sampling pulse is not output for a certain time after the sample is introduced. When the one with a cycle of 0.001 second is selected, the first sampling pulse is output after 1 minute.

[0010]

EFFECTS OF THE INVENTION According to the present invention, the sampling cycle becomes longer with the passage of time and the width of the chromatographic peak becomes wider with the retention time. There is no fear that the number of sampling points will be too large overall, as in the case of adoption, and that a large amount of memory will be used, or conversely, the number of sampling points will be insufficient and accurate data processing will not be possible. An appropriate number of data can be obtained for any of the peaks in the chromatogram, the memory is not wasted, and the operator has the effect of reducing the difficult task of setting the sampling period.

[Brief description of drawings]

FIG. 1 is a graph showing the deformation of chromatographic peaks depending on the number of sampling points.

FIG. 2 is a graph showing the relationship between the theoretical plate number of columns and the sampling number for one peak.

FIG. 3 is a graph showing the relationship between the retention time of sample components and the sampling cycle.

FIG. 4 is a functional block diagram of a data processing device of one embodiment for executing the method of the present invention.

FIG. 5 is a flowchart of the operation in the above example.

[Explanation of symbols]

 1 clock generator 2 frequency divider 3 selector 4 control circuit 5 first counter 6 second counter 7 keyboard

Claims (1)

[Claims] 1. A method for processing chromatographic data, characterized in that the sampling output of the chromatographic output is inversely proportional to the square root of the theoretical plate number of the column used, and is proportional to the elapsed time from the introduction of the sample, and the measurement output is sampled. .