Hewlett-packard Company

Other

Leonid M Blumberg

Bruce Douglas Quimby

Matthew Spangler Klee

Robert P Rhodes

Philip Leigh Wylie

Alan D Broske

Joseph Bush

Warren D Snyder

A method is provided for translating from a first method for performing gas chromatographic analysis to a second method for performing gas chromatographic analysis in a gas chromatography system without changing a peak elution pattern. Unlike the known method translation techniques that work only with the constant pressure gas chromatographic analyses, the invention can translate the gas chromatographic methods where column pressure and/or carrier gas flow rate change during the analysis by an arbitrary program.

Method translation in gas chromatography

A method for identifying analytes of interest by referencing to a retention factor database corresponding to a plurality of identified analytes that is independent of column dimensions and carrier gas type while dependent upon stationary phase type ratio and a relative temperature program. The retention factor database is generated on a reference GC system in which the column head pressure is adjusted to ensure high reproducibility of retention times by locking the column void time and/or the retention time of an identified analyte to a specific value such that accurate retention factors (k) can be calculated in accordance with the formula: ##EQU1## where VT is the void time of the column having a specified stationary phase and phase coating installed in a GC system operating in accordance to a specified temperature program (where time is expressed in units of column void time).

Retention factor database

The present invention provides an improved method for calculating and adjusting the column head pressure of a GC instrument based on the column's plate capacity, N.sub.c, and film thickness, d.sub.s, measured ideally during the manufacturing process and identified with the column such that software associated with the GC instrument can calculate a new column head pressure based on the relationship between the plate capacity and film thickness of the existing column to the plate capacity and film thickness of the new or shortened column. The column head pressure of the GC is adjusted to the new column head pressure to provide a reduction in the column-to-column non-reproducibility error in retention times of all peaks.

Column specific parameters for retention time locking in chromatography

The invention provides a method for automated matching of retention times obtained using a known chromatographic method having a defined set of column parameters and operating parameters to the retention times obtained using a new chromatographic method having a new set of column parameters, wherein the retention times of components separated in accordance with the new chromatographic method are matched to the retention times set forth in the known chromatographic methods. A procedure is described to adjust head pressure to compensate for differences in a new versus the original column, carrier gas, and column outlet pressure of the known method.

Automated retention time locking

The invention provides a method for developing a retention time database of identified analytes and their respective retention times in a reference Gas Chromatograph (GC) system under locked conditions for identification of unknown analytes of interest eluting from any GC system locked to the retention time database and may also be employed in combination with selective detection and or method translation for enhanced certainty of identification.

Method for sample identification using a locked retention time database

Analog-to-Digital Converter (A/D converter) consisting of several continuously integrating charge balancing (CB) conversion stages. During each conversion interval, all CB capacitors are discharged by a reference current. In each stage, the end of the discharge of the CB capacitor is detected by a zero crossing detector. Time intervals between the zero crossing events and corresponding discharge termination events represent time equivalents of quantization errors. Each stage, other than the first, converts the time equivalents of quantization errors of the previous stage. Output of the entire multistage A/D converter is combined from the outputs of all stages in a way which provides compensation of a quantization error of any stage by the output of the next stage. Quantization noise (sequence of quantization errors) of the entire A/D converter becomes the same as the N-time differenced (N-number of stages) quantization noise of the last stage. The differencing shapes spectral density of quantization noise in such a way that the largest portion of the noise energy becomes shifted outside of the signal bandwidth. The larger the number of stages, the smaller the in-band portion of the quantization noise. The out-of-band portion of quantization noise can be filtered out in the post-conversion digital signal processing.

Analog-to-digital converter

The invention is a method for modifying a known chromatographic method without changing peak elution order and with little or no change in resolution. Column and operational parameters of a known method are systematically translated to ensure that a new chromatographic method having possibly different column and operational parameters has a chromatographic output with similar separation.

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Hockessin, DE, United States of America

Leonid M Blumberg