Classical Detectors Parallel to the Mass Spectrometer

In principle, there are two possibilities for operating another detector parallel to the mass spectrometer. The sample can be already divided in the injector and passed through two identical columns. The second more difficult but controllable solution is the split of the eluate at the end of the column. 

The division of the sample on to two identical columns can be realized easily and carried out very reliably, but different retention times need to be considered due to the vacuum impact on the MS side. Since the capacities of the two columns are additive, the quantity of sample injected can be adjusted in order to make use of the operating range of the mass spectrometer. Two standard columns can be installed for most injectors without further adaptation being necessary. In the simplest case, the connection can be made using ferrules with two holes in them. It must be ensured that there is a good seal. A better connection involves an adaptor piece with a separate screw-in joint for each column. With this construction the independent positioning of the columns in the injector is possible. Suitable adaptors can be obtained for all common injectors. 

One of the obvious, limitations to this calculation is the critical nature of the radius measurement. Since this is a fourth power term, small errors in the ID measurement can result in relatively large errors in the flow rate. This becomes more critical with smaller diameter tubes (i.e., less than 100 pm). A lOOx microscope (if available) is a convenient tool for determining the exact ID of a particular length of restriction tubing. 

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