Chromatographic analysis

Apparatus comprising:

• a first sample valve means having first, second, third, fourth, fifth and sixth ports, said first port being in fluid communication with said second port, said third port being in fluid communication with said fourth port, and said fifth port being in fluid communication with said sixth port when said frst sample valve means is in a first position, said first port being in fluid communication with said sixth port, said second port being in fluid communication with said third port and said forth port being in fluid communication with said fifth port when said first sample valve means is in a second position, a sample loop extending between said second port and said fifth port;
• a column valve means having first, second, third, fourth, fifth and sixth ports, said first port being in fluid communication with said second port, said third port being in fluid communication with said fourth port, and said fifth port being in fluid communication with said sixth port when said second sample valve means is in a first position, said first port being in fluid communication with said sixth port, said second port being in fluid communication with said third port and said fourth port being in fluid communication with said fifth port when said second sample valve means is in a second position;
• a first conduit means for supplying a first stream of carrier fluid to the third port of said first sample valve means;
• a second conduit means for supplying a sample fluid to the first port of said first sample valve means, said sample fluid flowing from said first port to said second port and thus through said sample loop of said first sample valve means when said first sample valve means is in the first position;
• a third conduit means extending from the fourth port of said first sample valve means to the second port of said column valve means, said first stream of carrier fluid flowing through the sample loop of said first sample valve means to force the sample fluid contained in the sample loop of said first sample valve means from said first sample valve means to the second port of said column valve means when said first sample valve means is in the second position;
• a first chromatographic separation column means;
• fourth conduit means extending from the first port of said column valve means to the inlet of said chromatographic separation column means, the fluid flowing through said third conduit means being provided to the inlet of said chromatographic separation column means when said column valve means is in the first position;
• fifth conduit means extending from the outlet of said chromatographic separation column means to the third port of said column valve means;
• a detector means;
• sixth conduit means extending from the fourth port of said column valve means to the inlet of said detector means, at least one component of said sample fluid, which has a low value of concentration and/or detector sensitivity, being provided from the outlet of said first chromatographic separation column means to the inlet of said detector means when said column valve means is in the first position, said detector means providing at least one first response representative of the concentration of the at least one component in said sample fluid, which has said low value, provided from said first chromatographic separation column means, said column valve means being actuated to the second position when the at least one component of said sample fluid, which has a low value, has eluted from said first chromatographic separation column means;
• a dilution means;
• seventh conduit means extending from the sixth port of said column valve means to said dilution means, at least one component of said sample fluid, which has a high value of concentration and/or detector sensitivity, being backflushed from said chromatographic separation column means and provided to said dilution means when said column valve means is in the second position;
• eighth conduit means for supplying a second stream of carrier fluid to said dilution means;
• a second sample valve means having first, second, third, fourth, fifth and sixth ports, said first port being in fluid communication with said second port, said third port being in fluid communication with said fourth port, and said fifth port being in fluid communication with said sixth port when said second sample valve means is in a first position, said first port being in fluid communication with said sixth port, said second port being in fluid communication with said third port and said fourth port being in fluid communication with said fifth port when said second sample valve means is in a second position, a sample loop extending between said second port and said fifth port;
• ninth conduit means extending from said dilution means to the third port of said second sample valve means;
• tenth conduit means for supplying a third stream of carrier fluid to the first port of said second sample valve means;
• a second chromatographic separation column means;
• eleventh conduit means extending from the sixth port of said second sample valve means to the inlet of said second chromatographic separation column means, the diluted at least one backflushed component of said sample fluid flowing through the sample loop of said second sample valve means when said second sample valve means is in the second position, the diluted at least one backflushed component of said sample fluid being provided to the inlet of said second chromatographic separation column means when said second sample valve means is in the first position;
• and
• twelfth conduit means extending from the outlet of said second chromatographic separation column means to the fifth port of said column valve means, the diluted at least one backflushed component of said sample fluid being provided from the outlet of said second chromatographic separation column means to the inlet of said detector means when said column valve means is in the second position, said detector means providing at least one second response representative of the concentration of the diluted at least one backflushed component in said sample fluid.

A method for determining the concentration of at least two components in a sample fluid wherein at least one of said components has a low value of concentration and/or detector sensitivity and at least one of said components has a high value of concentration and/or detector sensitivity, said method comprising the steps of:

• passing a first stream of carrier fluid to a first chromatographic separation column means;
• injecting said sample fluid into the first stream of carrier fluid flowing to said first chromatographic separation column means;
• withdrawing a first effluent stream containing at least one component of said sample fluid, having said low value, from said first chromatographic separation column means and passing the thus withdrawn first effluent stream to a detector which provides at least one first response representative of the concentration of the at least one component of said sample fluid, having said low value, provided from said first chromatographic separation column means;
• withdrawing a second effluent stream containing at least one component of said sample fluid, having said high value, from said first chromatographic separation column means;
• diluting at least a portion of the thus withdrawn second effluent stream containing at least one component of said sample fluid having said high value;
• passing a second stream of carrier fluid to a second chromatographic separation column means;
• injecting the thus diluted portion into the second stream of carrier fluid flowing to said second chromatographic separation column means;
• and
• passing the second stream of carrier fluid containing the diluted at least one component of said sample fluid, having said high value, from said second chromatographic separation column means to a detector means which provides at least one second response representative of the concentration of the diluted at least one component of said sample fluid having said high value.