US-20260126419-A1 - GAS CHROMATOGRAPHY INSTRUMENT FOR DETERMINING A CONCENTRATION OF A VOLATILE MARKER

US20260126419A1US 20260126419 A1US20260126419 A1US 20260126419A1US-20260126419-A1

Abstract

The invention relates to a gas chromatography instrument ( 2 ) for determining a concentration of a volatile marker. The instrument ( 2 ) comprises a first chromatographic column ( 8 ) and a first detector ( 12 ). It has been found that retention times and peak heights of all compounds in a chromatogram are not universal constants of nature, but depend strongly on many parameters, like thecolumn dimensions, materials and operating conditions. By utilizing an additional detector ( 22 ) or an additional chromatographic column ( 24 ), wherein the additional detector ( 22 ) differs from the first detector ( 12 ) by a detector property and/or the additional chromatographic column ( 24 ) differs from the first chromatographic column ( 8 ) by a column property, these redundancies can be exploited to determine a reliable consensus concentration value for the marker and allows for determining a confidence level thereof.

Inventors

Alwin Rogier Martijn Verschueren

Assignees

KONINKLIJKE PHILIPS N.V..

Dates

Publication Date: 20260507
Application Date: 20221017
Priority Date: 20211025

Claims (15)

1 . Gas chromatography instrument for determining a concentration of a volatile marker, the instrument comprising: a sampling device, a first chromatographic column, a process flow path connecting the sampling device to the chromatographic column, and a first detector connected to the first chromatographic column wherein the chromatography instrument further comprises at least one of the following: an additional detector, an additional chromatographic column, wherein the additional detector differs from the first detector by a detector property and/or the additional chromatographic column differs from the first chromatographic column by a column property.
2 . The gas chromatography instrument as defined by claim 1 , further comprising: a sample flow path configured to guide a fluid to be sampled to the sampling device, a valve arrangement for connecting either of the sample flow path or the process flow path to the sampling device, wherein in a sampling mode, the sampling device is connected to the sample flow path, and in an analysis mode, the process flow path and the chromatographic column are connected to the sampling device.
3 . The gas chromatography instrument as defined by claim 1 , wherein the sampling device is configured as one of the following: sample loop, thermal desorber.
4 . The gas chromatography instrument as defined by claim 1 , wherein the column property is at least one of the following: column dimension, column material, column operating condition.
5 . The gas chromatography instrument as defined by claim 1 , wherein the detector property is at least one of the following: detector principle, sensing material, sensor operating conditions.
6 . Method for determining a concentration of a volatile marker using gas chromatography, the method comprising: providing a first chromatogram under a first chromatographic condition, providing a second chromatogram under a second chromatographic condition, wherein the second chromatographic condition differs from the first chromatographic condition, identifying a peak corresponding to the marker within each chromatogram, determining a peak area and/or peak height of the peak corresponding to the marker for each chromatogram, determining an estimate of the marker concentration based on a peak area and/or peak height for a known marker concentration using predetermined calibration information for each chromatogram, determining a consensus value for the marker concentration from the two estimates of the marker concentrations from the two chromatograms.
7 . The method as defined by claim 6 , wherein the first and second different chromatographic conditions are established by utilizing a single sample and multiple sequential injections, wherein for each sequential injection a chromatogram is determined.
8 . The method as defined by claim 6 , wherein the first and second different chromatographic conditions are established by utilizing multiple sequential samples and different operating conditions.
9 . The method as defined by claim 8 , wherein the different operating conditions are characterized by at least one of the following: injection condition, column flow rate, column pressure rate, column temperature, detector temperature.
10 . The method as defined by claim 6 , wherein the identification of the peak corresponding to a marker is based upon pre-determined calibration information.
11 . The method as defined by claim 6 , wherein the pre-determined calibration information comprises: peak retention time, and peak conversion factor.
12 . The method as defined by claim 11 , wherein the pre-determined calibration information further comprises at least one of the following: peak width of a Gaussian standard deviation, time constant of the exponential peak broadening.
13 . The method as defined by claim 6 , comprising: determining a confidence level for the consensus value of the marker concentration.
14 . Gas chromatography instrument, the instrument comprising: a providing unit configured for providing a first chromatogram under a first chromatographic condition, and for providing a second chromatogram under a second chromatographic condition, wherein the second chromatographic condition differs from the first chromatographic condition a processor configured to carry out the steps of the method as defined in claim 6 .
15 . A computer program for determining a concentration of a marker in a sample, the computer program comprising program code means for causing a computer to carry out the steps of the method as defined in claim 6 .

Description

FIELD OF THE INVENTION The invention relates to a gas chromatography instrument, method and computer program for determining a concentration of a volatile marker. BACKGROUND OF THE INVENTION A gas chromatography instrument is a well-known instrument for detecting and determining a concentration of gas compounds. It consists of a chromatographic column that has the ability to separate a mixture of gasses into individual components, and a detector that outputs a signal depending on the concentration and/or type of gas that passes through it. A chromatographic column is limited in the number of gas compounds it can separate. Typically, this scales with the square root of the length of the column. That means that for the shorter length columns, which are beneficial for so-called process gas chromatographs, and even more for micro gas chromatographs, the recorded chromatogram will not merely consist of isolated peaks, but rather a superposition of partially or fully overlapping peaks. This means that it may become difficult to identify the actual peak corresponding the marker of interest, and determine the peak area of the marker of interest, corrected for the overlapping contributions of the neighboring peaks. This results in inaccuracies and even errors in the determination of the marker concentration. SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas chromatography instrument, method and computer program for determining a concentration of a volatile marker more accurately. In a first aspect, a gas chromatography instrument for determining a concentration of a volatile marker is presented. The instrument comprises a sampling device, a first chromatographic column, a process flow path connecting the sampling device to the chromatographic column, and a first detector connected to the first chromatographic column, wherein the chromatography instrument comprises at least one of the following: an additional detector, an additional chromatographic column, wherein the additional detector differs from the first detector by a detector property and/or the additional chromatographic column differs from the first chromatographic column by a column property. It has been found that retention times and peak heights of all compounds in a chromatogram are not universal constants of nature, but depend strongly on many parameters, like the column dimensions, materials and operating conditions. By combining the concentration determinations from multiple non-identical chromatographic conditions, their redundancies can be exploited to determine a reliable consensus concentration value for the marker and allows for determining a confidence level thereof. In a preferred embodiment, the gas chromatography instrument further comprises a sample flow path configured to guide a fluid to be sampled to the sampling device, and a valve arrangement for connecting either of the sample flow path or the process flow path to the sampling device, wherein in a sampling mode, the sampling device is connected to the sample flow path, and in an analysis mode, the process flow path and the chromatographic column are connected to the sampling device. The fluid may either be gas or a liquid which is converted into gas. The gas sampling device is preferentially configured as one of the following: sample loop, thermal desorber. Sample loops are widely available with commercial gas chromatography instruments. It has been realized that a thermal desorber allows splitting the absorbed sample into multiple fractions injected into the column during consecutive chromatographic runs. In this way, the thermal desorber allows to generate multiple, in particular sequential, chromatographic conditions, even when using a single sample, single column and single detector. The column property can be at least one of the following: column dimension, in particular any of or a combination of column length, column diameter, column film thickness, column material, column operating condition, in particular any of or a combination of column temperature, column pressure, column flow-rate. The underlying principle of this multiple column embodiment is that it allows the creation of multiple chromatographic conditions with different peak patterns, such that the marker concentration can be determined independently from each condition. This allows more robustness and confidence in the final concentration estimate. The detector property can be at least one of the following: detector principle, sensing material, sensor-operating conditions. Preferably, the first detector is connected to the additional detector in parallel or in series. In this regard, it has been realized that no detector exists that has a universal sensitivity for all gas compounds, in the sense of a universal conversion factor of peak area to ppb concentration independent of the gas compound. Therefore, two non-identical detectors will give a different information, different peak heig