Abstract: A method for detecting substances or mixtures of substances within a sample in an apparatus for comprehensive two-dimensional gas-chromatographic analysis according to the present invention, comprising the steps of: subjecting the sample to a first separation within a first capillary column; modulating in time the effluents from the first column by means of the subdivision into adjacent fractions of the effluents from the first column and subsequently sending each fraction into a second capillary column, the modulation of the effluents being periodic with a first modulation frequency f1 of the sample; separating each of the fractions in the aforesaid second capillary column; and detecting, at the end of the second capillary column, the effluents by means of periodic sampling by discrete time points at a second frequency f2.

Abstract: This invention relates to a modulator for use in gas chromatographic analyses, in particular for comprehensive two-dimensional gas chromatography, adapted to alternatively trap and release fractions of solutes in a length of a capillary column within a chromatographic oven, of the type comprising one nozzle placed to spray one jet in one corresponding capillary column section along said capillary column length, said nozzle being connected to a source of liquid CO2 and means for alternatively causing a jet of gaseous CO2 to impinge during a predetermined time on said capillary column section and to leave the oven atmosphere to heal said capillary column section after said predetermined time. By controlling said capillary column section cooling time by the single jet and said column section heating time by the oven atmosphere in each modulation cycle comprising a heating time and a cooling time a perfect modulation of the sample fractions can be ontained.

Abstract: This invention relates to a modulator for use in gas chromatographic analysis, adopted for alternatively trapping and releasing fractions of solutes in a length of a capillary column within a chromatographic oven, characterized in that it comprises at least one nozzle placed to spray at least one jet in at least one corresponding place along said capillary column length, said nozzle(s) being connected each to a source of liquid CO2 via a related valve, and means for alternatively opening said valve(s) for a predetermined time, to cause a jet of liquid CO2 to impinge for said predetermined time on said column place and to leave the oven atmosphere to heat said column place after said predetermined time. The modulator can be used in a conventional GC system or in a two dimensional GC system, for modulating the analytes fed to the second capillary column.

Abstract: This invention relates to a modulator for use in gas chromatographic analysis, adapted for alternatively trapping and releasing fractions of solutes in a length of a capillary column within a chromatographic oven, characterized in that it comprises at least one nozzle placed to spray at least one jet in at least one corresponding place along said capillary column length, said nozzle(s) being connected each to a source of liquid C02 via a related valve, and means for alternatively opening said valve(s) for a predetermined time, to cause a jet of liquid C02 to impinge for said predetermined time on said column place and to leave the oven atmosphere to heat said column place after said predetermined time. The modulator can be used in a conventional GC system or in a two dimensional GC system, for modulating the analytes fed to the second capillary column.

Abstract: A method for detecting substances or mixtures of substances within a sample in an apparatus for comprehensive two-dimensional gas-chromatographic analysis according to the present invention, comprising the steps of:

Abstract: This invention relates to a modulator for use in gas chromatographic analysis, adopted for alternatively trapping and releasing fractions of solutes in a length of a capillary column within a chromatographic oven, characterized in that it comprises at least one nozzle placed to spray at least one jet in at least one corresponding place along said capillary column length, said nozzle(s) being connected each to a source of liquid CO2 via a related valve, and means for alternatively opening said valve(s) for a predetermined time, to cause a jet of liquid CO2 to impinge for said predetermined time on said column place and to leave the oven atmosphere to heat said column place after said predetermined time. The modulator can be used in a conventional GC system or in a two dimensional GC system, for modulating the analytes fed to the second capillary column.