Standardization of chromatographic systems

A method of standardizing a target chromatographic system with a primary chromatographic system, each system including a gas chromatographic column with associated column dimensions and a column inlet, carrier means for passing a gas carrier through the column, injection means for injecting a pulse of sample into the carrier to effect a mixture passing through the column subject to characteristic retention times for constituents of the sample, detector means receptive of the mixture for effecting signals representative of the retention times, and processing means receptive of the signals for presenting corresponding retention indicators, wherein the systems have operating parameters comprising temperature programs for column temperature and at least one pressure program of carrier pressure at the column inlet, each program being with respect to time, and the retention times being related to the operating parameters by a mathematical function having function parameters including column dimensions and thermodynamic constants associated with interactions of the constituents with the column;

• the method comprising steps of:
• establishing primary column dimensions for the column of the primary chromatographic system;
• operating the primary chromatographic system with a standard sample, a selected primary pressure program, and a plurality of selected primary temperature programs, so as to generate corresponding primary retention indicators;
• fitting the primary retention indicators and the primary temperature programs to the function, with the primary pressure program, so as to determine thermodynamic constants whereby the function is representative of a virtual chromatographic system;
• and
• storing the thermodynamic constants for future application with a target chromatographic system.

A method of calibrating column temperature of a target chromatographic system relative to that of a primary chromatographic system, each system including a gas chromatographic column, carrier means for passing a gas carrier through the column, injection means for injecting a pulse of sample into the carrier to effect a mixture passing through the column subject to characteristic retention times for constituents of the sample, detector means receptive of the mixture for effecting signals representative of the retention times, and processing means receptive of the signals for processing corresponding retention times;

• the method comprising steps of:
• providing a temperature standard comprising a calibration compound having temperature dependent retention time, and a plurality of homolog standards having a homolog relationship between corresponding retention indicators and retention times;
• operating the primary chromatographic system with the temperature standard, a selected primary pressure program and a plurality of selected calibration temperatures for the column so as to generate a primary set of retention times for each calibration temperature, each primary set comprising homolog retention times for the homolog standards and a compound retention time for the calibration compound;
• first utilizing the homolog relationship and the primary set of retention times for each calibration temperature to determine calibration constants for a temperature relationship relating retention indicator for the calibration compound to column temperature for the primary system;
• operating the target chromatographic system with the temperature standard and a measured column temperature so as to generate a test set of retention times, the test set comprising test retention times for the homolog standards, and a test retention time for the calibration compound;
• second utilizing the homolog relationship and the test set of retention times to determine a secondary retention indicator for the calibration compound;
• and
• applying the temperature relationship with the calibration constants and the secondary retention indicator to determine a calibrated temperature corresponding to the measured temperature.

A method of validating a target chromatographic system by utilization of a primary chromatographic system, each system including a gas chromatographic column, carrier means for passing a gas carrier through the column, injection means for injecting a pulse of sample into the carrier to effect a mixture passing through the column subject to characteristic retention times for constituents of the sample, detector means receptive of the mixture for effecting signals representative of the retention times, and processing means receptive of the signals for processing the retention times, the target chromatographic system having a calibrated temperature relationship between its column temperature and column temperature for the primary chromatographic system;

• the method comprising steps of:
• providing a validation standard comprising selected validation constituents, and a plurality of homolog standards having a homolog relationship between corresponding retention indicators and retention times;
• operating the primary chromatographic system with the validation standard, a selected primary pressure program, and a primary validation temperature for the column, so as to generate primary validation retention times for the validation constituents and homolog retention times for the homolog standards;
• operating the target chromatographic system with the validation standard, substantially the primary pressure program, and the measured column temperature so as to generate secondary validation retention times for the validation constituents and test retention times for the homolog standards;
• utilizing the homolog retention times to determine primary homolog parameters for the homolog relationship, and the test retention times to determine secondary homolog parameters for the homolog relationship;
• utilizing the homolog relationship, the primary homolog parameters and the primary validation retention times to effect preliminary retention indicators;
• utilizing the homolog relationship, the secondary homolog parameters and the secondary validation retention times to effect secondary validation retention indicators;
• adjusting the preliminary retention indicators with the temperature relationship to a calibrated temperature corresponding to the secondary validation temperature so as to effect primary validation retention indicators;
• calculating differences between corresponding primary validation retention indicators and secondary validation retention indicators;
• and
• determining whether the differences are less than a predetermined limit corresponding to whether the target chromatographic system is valid.

A method of determining values for one or more specified parameters for a chromatographic system, the system including carrier means for passing a fluid carrier through the column, injection means for injecting a pulse of sample into the carrier to effect a mixture passing through the column subject to characteristic retention times for constituents of the sample, detector means receptive of the mixture for effecting signals representative of the retention times, and processing means receptive of the signals for presenting corresponding retention indicators, the system having system parameters and operating parameters related to retention times by a mathematical function having function parameters including the system and operating parameters, and the function parameters having predetermined or assumed values except for the specified parameters;

• the method comprising steps of:
• operating the system so as to generate retention indicators, providing an initial data base defining ranges of potential values of the specified parameters, computing theoretical retention indicators with the function for the potential values and the predetermined or assumed values, computing differences between the theoretical retention indicators and the secondary retention indicators, and searching the differences for a minimum therein, such that the minimum establishes an effective value for each specified parameter.