Clarity discussion forum

Dear all,

I want to use a Valco Multiposition valve as a fractioning device. Port 1 should be used as waste port.
Port 1 is also declared as home position.

When I build a event table with input run > 100mV Detector response output type fraction next. The valve switches to position 2 when the solvent peak elutes. The command input run < 100mV Detector response output type fraction next will switch to position 3. But when a new peak elutes my first event will change the valve to position 4.

When I set input run < 100mV Detector response output type fraction position 1 and input run > 100mV Detector response output type fraction next, then every peak will be collected into my vial at port 2.

Is it possible to use a kind of delay time for the events in the event table to exclude the first peak from beeing collected?

When I inject a solution of 2 compounds dissolved in solvent. Every compound gives a detector response, but I don`t want to collect the solvent peak.

I am searching for a possibility to start the run and let the event table "sleep" a defined time and start after the delay time. In other words: a solvent delay.

Maybe I am a little "blind" at the moment.

Is it possible to get the GP Fraction Collector working for GC use with a Valco valve?

Best regards

Stephan

Dear Stephan,
a fraction collector solution based on the Valco Valve will be introduced in Clarity version 4.0, which is scheduled for the beginning of Year 2012 (release version should be available before Pittcon, beta version in January).

As for now, I have to say Clarity does not have straight solution for combining event triggers in the Event table - applying both time of the analysis and level of the signal in this case. However, a workaround may be used, which could suit your needs for now:

• In the configuration, add a Virtual Digital Input Output Loop device to the Instrument. This is virtual control module which provides a source of digital input, which is the same as value of its digital output. Normally it can serve for starting analyses, over-instrument synchronization etc.
• Create a row in the event table which sets the Virtual Digital Input Output Loop to High during a pre-run (Type should be Time Idle >)
• Create another row in the event table which sets the Virtual Digital Input Output Loop to High during a run if the signal goes over a certain level, the same as you now have for the VICI valve.
• Create another row in the event table which sets the Virtual Digital Input Output Loop to Low during a run if the signal goes under a certain level, the same as you now have for the VICI valve.
• Redesign your VICI valve to react not on the level of the signal, but on the Digital Input Output Loop levels instead.
• Add some Idle time to your analyses to cover the switching of the valve. This may be done in the Sequence options.

Now, this should work - while the event reacts on the transition from Low to High or vice versa, the valve should not switch at the beginning of the first peak (because the level is already HIGH, so no switching is performed). At the end of the first peak, it should change to low and from then on it should follow the signal as you want, thus effectively cancelling the first peak from the equation.

Keep in mind I haven't tested this solution, but according to my knowledge, it should work the desired way.