Injection systems small bore capillary columns

The split-flow injector is very similar to the packed column injector except that only part of the carrier flow passes to the column, the rest exits to waste. By varying the exit flow-impedance, the split-ratio can be adjusted over a wide range. Without this type of split injection system, the small bore capillary columns would be virtually impossible to use. However, because of the waste of sample and the relatively small mass range obtainable from small bore columns, the large bore capillary column was introduced. 

Inlet systems for packed columns can often be used with capillary columns as well. However, the much smaller injection volumes and slower gas flow rates used with capillary columns, especially small-bore... 

Bayliss and co-workers [10] combined ultra-high flow rates, parallel LC columns, a multiplex electrospray source, and mass spectrometric detection for the rapid determination of pharmaceuticals in plasma using four narrow bore (50 mm x 1 mm, 30 pm Oasis HLB) or capillary (50 mm x 0.18 mm, 25 pm Oasis HLB) HPLC columns with large particle sizes (to avoid high system back-pressure) in parallel with a multiple probe injector and a MUX MS interface. Small sample aliquots were injected directly into the system without sample pre-treatment procedure, obtaining very low limits of quantification (from 1 to 5 ng/mL). 

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