WO2016200763A1

WO2016200763A1 - Method and apparatus for retention time update in process gas chromatography

Info

Publication number: WO2016200763A1
Application number: PCT/US2016/036137
Authority: WO
Inventors: Ray Dean Shepherd; Aosheng Wang
Original assignee: Siemens AG; Siemens Corp; Siemens Industry Inc
Current assignee: Siemens AG; Siemens Corp; Siemens Industry Inc
Priority date: 2015-06-10
Filing date: 2016-06-07
Publication date: 2016-12-15
Anticipated expiration: 2017-12-10

Abstract

A chromatograph and a process gas chromatography (PGC) method of updating a retention time of a peak in a chromatogram from the chromatograph are provided. The method includes monitoring a chemical component in a process environment to detect a peak of the chemical component in a current cycle of a process stream in process gas chromatography to identify an associated chemical component being monitored. The method further includes providing a peak retention time update from cycle to cycle for adjusting an expected retention time after each cycle of the process stream based on a priority list of reference peaks.

Description

METHOD AND APPARATUS FOR RETENTION TIME UPDATE IN PROCESS GAS CHROMATOGRAPHY

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/173,721 entitled "PRIORITY PEAK LIST FOR RETENTION TIME UPDATE IN PROCESS GAS CHROMATOGRAPHY", filed on June 10, 2015, which is incorporated herein by reference in its entirety.

BACKGROUND

1. Field

[0001] Aspects of the present invention generally relate to a chromatograph and a method of updating a Retention Time (RT) of a peak in a chromatogram from a process gas chromatograph (PGC) and more specifically relates to providing a robust retention time update in the PGC.

2. Description of the Related Art

[0002] Automation technology contributes decisively to the continuous optimization of company-wide processes. Integrated automation may be provided via automation systems in the manufacturing and process industry. For automation, a process control system provides solutions for all sectors of the production, process and automation of the entire process chain of a company. A process control system may use sensor systems which provide precise measurement results and the reliable control of all processes. Process analytics is done by process analyzers and process analysis systems. Process analyzer includes continuous gas analyzers and process gas chromatographs. [0003] Process gas analyzers are used for continuous calculation of concentration values of one or more gases in a gas mixture for controlling and monitoring process flows. Process gas analyzers use different physical or electro-chemical measuring methods depending on the task. Process gas analyzers have been used in the process industry for decades. Continuous process gas analysis with both extractive and in-situ analysis techniques is done.

[0004] Process gas chromatography is one of the most powerful measuring and analysis methods for process engineering. It is a procedure which is both discrete and extractive. This procedure is frequently used for online monitoring of processes since the sequences are easy to automate and a large number of components can be measured simultaneously. Process gas chromatography can be used to separate and quantify the components of almost all homogenous gaseous or liquid mixtures. It must be possible to vaporize the liquid components without decomposition. The individual components of a discrete sample pass through the column system at different velocities, and are recorded in succession by a detector.

[0005] The time between sample introduction and registering of a substance at the detector (the retention time) is characteristic of the substance and is used to identify it. The magnitude of the detector signal is a measure of the volume concentration of the component in the gas or liquid.

[0006] Retention time (RT) of a peak in a chromatogram is used in process gas chromatography (PGC) to identify its associated chemical component being monitored. However, due to fluctuations in carrier gas flow rate and/or in column temperature or degradations in column stationary phase, peak retention time often shifts from cycle to cycle, which can cause a misidentification of a peak if the peak retention time shifts outside of its expected retention time window defined in a PGC method. As a result, frequent analyzer maintenance and/or a manual method of calibration are often required to adjust the expected retention time of the peak, which can be expensive and inefficient.

[0007] Automatic cycle-to-cycle peak retention time update is often used for automatically adjusting expected peak retention time after each cycle, where the actual peak retention time in the current cycle is used as the expected peak retention time for the next cycle. Unfortunately, in a process environment, a chemical component being monitored may not always exist or its concentration may be too low to be detected in some cycles of the process stream, which will fail the retention time update in these cycles. The failed retention time update in these cycles can potentially fail retention time update in all subsequent cycles if the component has not been detected contiguously for too many cycles where smaller and tolerable retention time shifts after each cycle may be accumulated to become a large and intolerable shift beyond the expected retention time window that is set in the last successful retention time update.

[0008] As an alternative, a reference peak of another chemical component, instead of the peak of interested component, can be setup for automatic cycle-to-cycle retention time update and the expected retention time of the peak of interest can be calculated from that of the reference peak. However, the reference component may also not always exist or its concentration may also be too low to be detected in some cycles of the process stream, which may not reduce the probability of failure enough for a robust retention time update.

[0009] Therefore, there is a need for improvements in a robust retention time update in process gas chromatography.

SUMMARY

[0010] Briefly described, aspects of the present invention relate to a mechanism for performing a peak cycle-to-cycle retention time update. Embodiments of the present invention provide a software module for a process gas chromatograph that provides a more robust retention time update for a peak of interest by using retention time updates of multiple peaks, the peak of interest and/or one or more reference peaks, organized in a priority list that is specified for the peak of interest in a method. One of ordinary skill in the art appreciates that such a chromatograph for gas chromatographic analysis of a gas sample can be configured to be installed in different environments where updating a retention time of a peak in a chromatogram from a process gas chromatograph is needed, for example, based on a priority list of reference peaks.

[0011] In accordance with one illustrative embodiment of the present invention, a method of updating a retention time of a peak in a chromatogram from a process gas chromatograph is provided. The method comprises monitoring a chemical component in a process environment to detect a peak of the chemical component in a current cycle of a process stream in the process gas chromatograph to identify an associated chemical component being monitored and providing a peak retention time update from cycle to cycle for adjusting an expected retention time after each cycle of the process stream by: using an actual retention time of the peak of the chemical component in the current cycle as the expected retention time of a detected peak for the next cycle for a peak in a priority list of one or more peaks that is detected in the current cycle and calculating the expected retention time for the next cycle for a peak in the priority list that is not detected in the current cycle based on an expected retention time and an actual retention time of a detected peak in the priority list. A peak retention time is defined in an expected retention time window being defined in a process gas chromatography (PGC) method. The detected peak in the priority list is picked based on a priority thereof in the priority list.

[0012] In accordance with another illustrative embodiment of the present invention, a method of performing a peak cycle-to-cycle retention time update is provided. The method comprises updating a retention time of a first peak being a peak of interest in a priority list that is detected in a current cycle by a first criteria and updating the retention time of a second peak being the peak of interest in the priority list that is not detected in the current cycle by a second criteria different than the first criteria. The first peak is a peak of a chemical component in a chromatogram from a process gas chromatograph (PGC) and the second peak is the peak of a different chemical component in the same chromatogram. [0013] In accordance with yet another illustrative embodiment of the present invention, a chromatograph for gas chromatographic analysis of a gas sample is provided. The chromatograph comprises a separating device having a downstream thermal conductivity detector and an evaluation device coupled to the thermal conductivity detector. The gas sample is being conveyed by a carrier gas through the separating device and the thermal conductivity detector delivering a chromatogram of the gas sample. The evaluation device having a chromatographic software module to: update a retention time of a first peak being a peak of interest in a priority list that is detected in a current cycle by a first criteria and update the retention time of a second peak being the peak of interest in the priority list that is not detected in the current cycle by a second criteria different than the first criteria. The first peak is a peak of a chemical component in a chromatogram in a process gas chromatograph (PGC) and the second peak is the peak of the chemical component in the same chromatogram.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 illustrates a simplified schematic block diagram of an exemplary process gas chromatograph in accordance with an exemplary embodiment of the present invention.

[0015] FIG. 2 illustrates an exemplary graphical plot of a chromatogram from the process gas chromatograph of FIG. 1 in accordance with an exemplary embodiment of the present invention.

[0016] FIG. 3 illustrates a flow chart of a method of a peak cycle-to-cycle retention time update with a priority list of reference peaks in accordance with an exemplary embodiment of the present invention.

[0017] FIG. 4 illustrates a flow chart of a method of updating a retention time of a peak in the chromatogram of FIG. 2 from the process gas chromatograph of FIG. 1 in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0018] To facilitate an understanding of embodiments, principles, and features of the present invention, they are explained hereinafter with reference to implementation in illustrative embodiments. In particular, they are described in the context of a software module for a process gas chromatograph that provides a more robust retention time update for a peak of interest based on a priority list of reference peaks. Embodiments of the present invention, however, are not limited to use in the described devices or methods.

[0019] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present invention.

[0020] FIG. 1 illustrates a simplified schematic block diagram of an exemplary process gas chromatograph 10 (PGC) or a GC analyzer in accordance with an exemplary embodiment of the present invention. The process gas chromatograph 10 comprises an injector 15 coupled to a separating device 20. The separating device 20 is coupled to a thermal conductivity detector 25. The thermal conductivity detector 25 includes a measuring cell 30 having a measurement channel 35 and a detector element 40 such as an electrically heated heating filament. The thermal conductivity detector 25 further includes an evaluation device 45 where a change in the electrical resistance of a heating filament 50 is detected. To this end, the heating filament 50 may be arranged in a measurement bridge in a manner known per se (not shown). The evaluation device 45 provides an output 55 that indicates the presence and amount of the gas components. [0021] As used herein, "a GC analyzer" refers to a device used for process gas chromatography for measuring and analysis of chemical components in process engineering. The GC analyzer is capable of a procedure which is both discrete and extractive. The GC analyzer may be used for online monitoring of processes since the sequences are easy to automate and a large number of components can be measured simultaneously. The "GC analyzer," in addition to the exemplary hardware description above, refers to a system that is configured to separate and quantify the components of almost all homogenous gaseous or liquid mixtures. The GC analyzer can include multiple interacting systems, whether located together or apart, that together perform processes as described herein.

[0022] The process gas chromatograph 10 may analyze a vapour or a volatile liquid sample and then separates the various chemical components in the sample for individual detection and measurement. The discrete separation and positive identification of components and measurement of the composition enables the process gas chromatograph 10 to minimize the likelihood of cross interference during measurement. The process gas chromatograph 10 may also measure multiple chemical compounds during each analysis to levels that reach parts-per-million and even parts-per-billion levels.

[0023] In operation, in the process gas chromatograph 10, a carrier gas 60 is delivered to the injector 15, loaded there with a sample of a gas mixture 65 to be analyzed and subsequently introduced into the separating device 20 such as a single separation column or a complete system of separation columns. The separated components or substances of the gas mixture 65 emerging successively from the separating device 20 travel to the thermal conductivity detector 25. Here, the separated gas components are conveyed in the measurement channel 35 of the measuring cell 30 past the detector element 40. Depending on the thermal conductivity of the gas components respectively flowing past in comparison with that of the carrier gas 60, more or less heat is transferred from the heating filament 50 to the channel wall so that the heating filament 50 is correspondingly cooled or heated. As a result, the electrical resistance of the heating filament 50 changes, where the change is detected in the evaluation device 45 of the thermal conductivity detector 25. The evaluation device 45 provides the output 55 that indicates the presence and amount of the gas components passing the heating filament 50.

[0024] The evaluation device 45 includes a chromatographic software module 57 to update a retention time (RT) 70 of a peak 75 being a peak of interest in a priority list 80 of reference peaks. The retention time (RT) 70 is the time between sample introduction and registering of a substance at the detector which is characteristic of the substance and is used to identify it. The magnitude of a detector signal is a measure of the volume concentration of the component in the gas or liquid.

[0025] A cycle-to-cycle peak retention time update 82 is used for adjusting an expected peak retention time after each cycle of a process stream 90 in the process gas chromatograph 10 to identify an associated chemical component being monitored. The retention time (RT) 70 of the peak 75 in a chromatogram 85 is used in process gas chromatography (PGC) to identify its associated chemical component being monitored. The chromatogram 85 is a visible record (such as a series of colored bands or a graph of peaks) showing the result of separation of the components of a mixture by chromatography. A peak retention time is defined in an expected retention time window being defined in a process gas chromatography (PGC) method. However, the peak retention time may shift from cycle to cycle, which can cause a misidentification of a peak if the peak retention time shifts outside of its expected retention time window defined in the PGC method.

[0026] The process gas chromatograph 10 may monitor a chemical component in a process environment to detect the peak 75 of the chemical component in a current cycle 87 of the process stream 90 to identify an associated chemical component being monitored. To adjust an expected retention time (ERT) 92 after each cycle of the process stream 90 the peak retention time update 82 may be provided from cycle to cycle. The peak retention time update 82 may be provided by the chromatographic software module 57 by using an actual retention time (ART) 94 of the peak 75 of the chemical component in the current cycle 87 as the expected retention time (ERT) 92 of a detected peak for a next cycle 96 for a peak in the priority list 80 of one or more peaks that is detected in the current cycle 87.

[0027] The peak retention time update 82 may be provided by the chromatographic software module 57 by calculating the expected retention time (ERT) 92 for the next cycle 96 for a reference peak in the priority list 80 that is not detected in the current cycle 87 based on an expected retention time (ERT) and an actual retention time (ART) of a detected peak in the priority list 80. The detected peak in the priority list 80 may be picked based on a priority 98 thereof in the priority list 80. For example, a number of reference peaks in the priority list 80 may be assigned a priority in a descending order starting from a highest priority of a first reference peak in the priority list and so on continuing to a lowest priority of the last reference peak in the priority list.

[0028] The chromatographic software module 57 may provide the peak retention time update 82 for a peak of interest by using peak retention time updates of multiple peaks, the peak of interest and one or more reference peaks organized in the priority list 80 that is specified for the peak of interest in the process gas chromatography (PGC) method. The chromatographic software module 57 may perform the peak retention time update 82 of the peak independent of other peaks in the priority list 80.

[0029] The chromatographic software module 57 may calculate for each detected peak in the priority list 80: the expected retention time ERT(i+l) = the actual retention time ART(i) where ERT(i+l) is the expected retention time of the detected peak for the next cycle 96 and ART(i) is the actual retention time of the peak in the current cycle 87.

[0030] In the chromatographic software module 57, the priority 98 of the reference peak in the priority list 80 may be defined as described above. The chromatographic software module 57 may calculate for each undetected peak in the priority list 80: the expected retention time ERT(i+l, undetected) = (ART(i) / ERT(i)) * ERT(i, undetected) where ERT(i+l, undetected) is the expected retention time of an undetected peak for the next cycle 96, ERT(i, undetected) is the expected retention time of the undetected peak in the current cycle 87, ERT(i) is the expected retention time of the detected peak in the current cycle 87, and ART(i) is the actual retention time of the peak in the current cycle 87.

[0031] Referring to FIG. 2, it illustrates an exemplary graphical plot 200 of a chromatogram 205 from the process gas chromatograph 10 of FIG. 1 in accordance with an exemplary embodiment of the present invention. The graphical plot 200 shows a first peak of interest 210(1) (Peak-1) and a second peak of interest 210(2) (Peak-2). While two reference peaks 215(1-2) are shown for the Peak-1 210(1), three reference peaks 215 (3-5) are shown for the Peak-2 210(2).

[0032] Some of these peaks 210(1-2), 215 (1-5) can be missing in some cycles. The actual retention time (ART) of all peaks change from cycle to cycle. However, the ART differences between a peak of interest and its reference peaks change much less from cycle to cycle. The expected retention time (ERT) of all peaks are updated (using the priority list 80) at the end of a cycle to reduce the probability of failing to detect a peak of interest in a subsequent cycle where the peak is present in the cycle chromatogram 205 but its ART shifts too much from its original ERT. More reference peaks 215 (1-5) in the priority list 80 for a peak of interest reduce further the probability of failure.

[0033] The chromatographic software module 57 may be used to separate and quantify the components of almost all homogenous gaseous or liquid mixtures. It must be possible to vaporize the liquid components without decomposition. The individual components of a discrete sample pass through the column system at different velocities, and are recorded in succession by a detector. The chromatographic software module 57 with a priority list algorithm may be applied to any types of process chromatographs, such as process gas chromatographs and process liquid chromatographs.

[0034] Turning now to FIG. 3, it illustrates a flow chart of a method 300 of a peak cycle-to-cycle retention time update with the priority list 80 of reference peaks in accordance with an exemplary embodiment of the present invention. Reference is made to the elements and features described in FIGs. 1-2. It should be appreciated that some steps are not required to be performed in any particular order, and that some steps are optional. [0035] In the method 300, at a step 310, a current cycle of a process gas chromatography starts in accordance with an exemplary embodiment of the present invention. An expected retention time of a peak of interest is identified or defined and an expected retention time of a list of reference peaks ordered with descending priorities is identified or defined. At step 315, the current cycle ends.

[0036] Next, at a decision step 320, a check is made to determine whether the peak of interest was detected or not. If a yes answer to this query is detected, then at step 325 the chromatographic software module 57 may use an actual retention time (ART) of the peak of interest to update the ERT of all peaks. At step 327, a next cycle may start. If answer to the query at step 320 was no, at a decision step 330, a check is made to determine whether a first reference peak was detected or not. If a yes answer to this query is detected, then at step 335 the chromatographic software module 57 may use an actual retention time (ART) of the first reference peak to update the ERT of all peaks. At step 337, a next cycle may start. If answer to the query at step 330 was no, at a decision step 340, a check is made to determine whether a second reference peak was detected or not. If a yes answer to this query is detected, then at step 345 the chromatographic software module 57 may use an actual retention time (ART) of the second reference peak to update the ERT of all peaks. At step 347, a next cycle may start.

[0037] If answer to the query at the decision step 340 was no, at step 350 no reference peak is detected and at step 355 an alarm is issued. At step 357, a next cycle may start. In this way, even if a particular reference component may not always exist or its concentration may also be too low to be detected in some cycles of the process stream 90, a robust retention time update 82 still is provided by use of the priority list 80.

[0038] As long as there is at least one peak in the priority list 80 that is detected in each cycle, the expected retention times of all the peaks in the list for the next cycle can be updated properly. Statistically, the probability of all peaks in the priority list 80 being not detected simultaneously in a same cycle is significantly lower than that of a single peak, thereby reducing the probability of retention time update failure significantly for the peak of interest. [0039] FIG. 4 illustrates a flow chart of a method 400 of updating a retention time of a peak in the chromatogram 85 of FIG. 2 from the process gas chromatograph 10 of FIG. 1 in accordance with an exemplary embodiment of the present invention. Reference is made to the elements and features described in FIGs. 1-3. It should be appreciated that some steps are not required to be performed in any particular order, and that some steps are optional.

[0040] The method 400 of performing a peak cycle-to-cycle retention time update includes in step 405 monitoring a chemical component in a process environment to detect the peak 75 of the chemical component in the current cycle 87 of the process stream 90 in the process gas chromatography to identify an associated chemical component being monitored. In step 410, the method 400 may provide a peak retention time update from cycle to cycle for adjusting an expected retention time after each cycle of the process stream. To this end, in step 415, the method 400 may update a retention time of a first peak being a peak of interest in the priority list 80 that is detected in the current cycle 87 by a first criteria. The first peak is a peak of a chemical component in the chromatogram 85 from the process gas chromatograph (PGC) 10 of FIG. 1. In step 420, the method 400 may update the retention time of a second peak being the peak of interest in the priority list 80 that is not detected in the current cycle 87 by a second criteria different than the first criteria. The second peak is the peak of a chemical component in the chromatogram 85 from the process gas chromatograph (PGC) 10.

[0041] The first criteria may be to use an actual retention time of the first peak in the priority list 80 in the current cycle 87 as an expected retention time of the first peak for the next cycle 96. The second criteria may be to calculate the expected retention time for the next cycle 96 for the second peak based on an expected retention time and an actual retention time of a detected peak in the priority list 80. The detected peak in the priority list 80 may be picked based on a priority thereof in the priority list 80. For example, a reference peak with a highest priority may be picked first.

[0042] The method 400 may include organizing for the peak of interest at least one of retention time updates of multiple peaks, a retention time update of the peak of interest and retention time updates of one or more reference peaks in the priority list 80. The method 400 may include specifying the priority list 80 for the peak of interest in a process gas chromatography (PGC) method.

[0043] As a result, frequent analyzer maintenance and/or a manual method of calibration may not be required to adjust the expected retention time of the peak. Likewise fluctuations in carrier gas flow rate and/or in column temperature or degradations in column stationary phase may not adversely affect the chromatographic analysis.

[0044] The techniques described herein can be particularly useful for using a gas chromatograph (GC) analyzer. While particular embodiments are described in terms of a thermal conductivity detector, the techniques described herein are not limited to the thermal conductivity detector but can also use other category of detectors suitable for chromatography (e.g. Flame Ionization, Photo Multiplier, etc... ).

[0045] While embodiments of the present invention have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.

[0046] Embodiments and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known starting materials, processing techniques, components and equipment are omitted so as not to unnecessarily obscure embodiments in detail. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments, are given by way of illustration only and not by way of limitation. Various substitutions, modifications, additions and/or rearrangements within the spirit and/or scope of the underlying inventive concept will become apparent to those skilled in the art from this disclosure. [0047] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus.

[0048] Additionally, any examples or illustrations given herein are not to be regarded in any way as restrictions on, limits to, or express definitions of, any term or terms with which they are utilized. Instead, these examples or illustrations are to be regarded as being described with respect to one particular embodiment and as illustrative only. Those of ordinary skill in the art will appreciate that any term or terms with which these examples or illustrations are utilized will encompass other embodiments which may or may not be given therewith or elsewhere in the specification and all such embodiments are intended to be included within the scope of that term or terms.

[0049] In the foregoing specification, the invention has been described with reference to specific embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of invention.

[0050] Although the invention has been described with respect to specific embodiments thereof, these embodiments are merely illustrative, and not restrictive of the invention. The description herein of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein (and in particular, the inclusion of any particular embodiment, feature or function is not intended to limit the scope of the invention to such embodiment, feature or function). Rather, the description is intended to describe illustrative embodiments, features and functions in order to provide a person of ordinary skill in the art context to understand the invention without limiting the invention to any particularly described embodiment, feature or function. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the invention in light of the foregoing description of illustrated embodiments of the invention and are to be included within the spirit and scope of the invention. Thus, while the invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the invention.

[0051] Respective appearances of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" or similar terminology in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any particular embodiment may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the invention.

[0052] In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that an embodiment may be able to be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, components, systems, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the invention. While the invention may be illustrated by using a particular embodiment, this is not and does not limit the invention to any particular embodiment and a person of ordinary skill in the art will recognize that additional embodiments are readily understandable and are a part of this invention.

[0053] Although the steps, operations, or computations may be presented in a specific order, this order may be changed in different embodiments. In some embodiments, to the extent multiple steps are shown as sequential in this specification, some combination of such steps in alternative embodiments may be performed at the same time.

[0054] Embodiments described herein can be implemented in the form of control logic in software or hardware or a combination of both. The control logic may be stored in an information storage medium, such as a computer-readable medium, as a plurality of instructions adapted to direct an information processing device to perform a set of steps disclosed in the various embodiments. Based on the disclosure and teachings provided herein, a person of ordinary skill in the art will appreciate other ways and/or methods to implement the invention.

[0055] It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.

[0056] Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component.

Claims

What is claimed is:

1. A method of updating a retention time of a peak in a chromatogram from a process gas chromatograph, the method comprising:

monitoring a chemical component in a process environment to detect a peak of the chemical component in a current cycle of a process stream in the process gas chromatography to identify an associated chemical component being monitored; and providing a peak retention time update from cycle to cycle for adjusting an expected retention time after each cycle of the process stream by:

using an actual retention time of the peak of the chemical component in the current cycle as the expected retention time of a detected peak for a next cycle for a peak in a priority list of one or more peaks that is detected in the current cycle, wherein a peak retention time is defined in an expected retention time window being defined in a process gas chromatography (PGC) method, and

calculating the expected retention time for the next cycle for a peak in the priority list that is not detected in the current cycle based on an expected retention time and an actual retention time of a detected peak in the priority list, wherein the detected peak in the priority list is picked based on a priority thereof in the priority list.

2. The method of claim 1, further comprising:

providing the peak retention time update for a peak of interest by using peak retention time updates of at least one of multiple peaks, the peak of interest and one or more reference peaks organized in the priority list that is specified for the peak of interest in the process gas chromatography (PGC) method.

3. The method of claim 1, further comprising:

performing the peak retention time update of the peak independent of other peaks in the priority list.

4. The method of claim 1, wherein for each detected peak in the priority list: ERT(i+l)= ART(i) where ERT(i+l) is the expected retention time of the detected peak for the next cycle and ART(i) is the actual retention time of the peak in the current cycle.

5. The method of claim 1, further comprising:

defining the priority of the peak in the priority list: ERT(i+l, undetected) = (ART(i) / ERT(i)) * ERT(i, undetected) where ERT(i+l, undetected) is the expected retention time of an undetected peak for the next cycle, ERT(i, undetected) is the expected retention time of the undetected peak in the current cycle, ERT(i) is the expected retention time of the detected peak in the current cycle, and ART(i) is the actual retention time of the peak in the current cycle.

6. The method of claim 5, further comprising:

updating expected retention times of all the peaks in the priority list for the next cycle based on detecting at least one peak in the priority list in each cycle of the process stream in the process gas chromatograph.

7. A method of performing a peak cycle-to-cycle retention time update, the method comprising:

updating a retention time of a first peak being a peak of interest in a priority list that is detected in a current cycle by a first criteria, wherein the first peak is a peak of a chemical component in a chromatogram from a process gas chromatograph (PGC); and

updating the retention time of a second peak being the peak of interest in the priority list that is not detected in the current cycle by a second criteria different than the first criteria, wherein the second peak is the peak of a different chemical component in the chromatogram.

8. The method of claim 7, further comprising:

organizing for the peak of interest at least one of retention time updates of multiple peaks, a retention time update of the peak of interest and retention time updates of one or more reference peaks in the priority list.

9. The method of claim 8, further comprising:

specifying the priority list for the peak of interest in a process gas chromatography (PGC) method.

10. The method of claim 7, wherein updating a retention time of a first peak further comprising:

using an actual retention time of the first peak in the priority list in the current cycle as an expected retention time of the first peak for a next cycle.

11. The method of claim 10, wherein updating the retention time of a second peak further comprising:

calculating the expected retention time for the next cycle for the second peak based on an expected retention time and an actual retention time of a detected peak in the priority list, wherein the detected peak in the priority list is picked based on a priority thereof in the priority list.

12. The method of claim 7, further comprising:

performing a peak retention time update of the first peak or the second peak independent of other peaks in the priority list.

13. The method of claim 7, wherein for each detected peak in the priority list: ERT(i+l)= ART(i) where ERT(i+l) is the expected retention time of a detected peak for the next cycle and ART(i) is the actual retention time of the peak in the current cycle.

14. The method of claim 7, further comprising:

defining the priority of the detected peak in the priority list: ERT(i+l, undetected) = (ART(i) / ERT(i)) * ERT(i, undetected) where ERT(i+l, undetected) is the expected retention time of an undetected peak for the next cycle, ERT(i, undetected) is the expected retention time of the undetected peak in the current cycle, ERT(i) is the expected retention time of the detected peak in the current cycle, and ART(i) is the actual retention time of the peak in the current cycle.

15. The method of claim 14, further comprising:

16. A chromatograph for gas chromatographic analysis of a gas sample, comprising: a separating device having a downstream thermal conductivity detector, the gas sample being conveyed by a carrier gas through the separating device, the thermal conductivity detector delivering a chromatogram of the gas sample; and

an evaluation device coupled to the thermal conductivity detector, the evaluation device having a chromatographic software module to:

update a retention time of a first peak being a peak of interest in a priority list that is detected in a current cycle by a first criteria, wherein the first peak is a peak of a chemical component in a chromatogram in a process gas chromatograph

(PGC), and

update the retention time of a second peak being the peak of interest in the priority list that is not detected in the current cycle by a second criteria different than the first criteria, wherein the second peak is the peak of a different chemical component in the chromatogram.

17. The chromatograph of claim 16, wherein the chromatographic software module to:

organize for the peak of interest at least one of retention time updates of multiple peaks, a retention time update of the peak of interest and retention time updates of one or more reference peaks in the priority list; and

specify the priority list for the peak of interest in the process gas chromatograph

(PGC).

18. The chromatograph of claim 16, wherein the chromatographic software module to update a retention time of a first peak by using an actual retention time of the first peak in the current cycle as an expected retention time of a detected peak for a next cycle.

19. The chromatograph of claim 18, wherein the chromatographic software module to update the retention time of a second peak by calculating the expected retention time for the next cycle for the second peak based on an expected retention time and an actual retention time of a detected peak in the priority list, wherein the detected peak in the priority list is picked based on a priority thereof in the priority list.

20. The chromatograph of claim 16, wherein the chromatographic software module to perform a peak retention time update of the first peak or the second peak independent of other peaks in the priority list.