Spectrum Max Plot or Equivalent

[Alexburness]

A bit of background first - We currently run all our GCs on Clarity and are trialling Clarity in demo mode for the aim of potentially switching our two HPLC-PDA systems from their existing software (Class VP and Chromquest) to Clarity.

Everything so far is looking extremely positive, but with one fairly major sticking point.

Both Class VP and Chromquest have a 'Spectrum Max Plot' which for those who haven't encountered it, gives a plot of maximum absorbance over the PDA wavelength at any given time point against time. This has been ideal for us as it enables us to assess sample purity by normalised percentage peak areas over the chosen wavelength range.

Whilst single (or even up to the 4 Clarity supports) wavelengths are great for methods utilising standards, in our case standards aren't really an option due to the significant extra workload (with associated effects on turnaround time) this would entail, coupled with the fact that a significant proportion of the impurities/products are either not commercially available at appropriate price range, are unknown or are reaction intermediates. The alternative of just assessing peak areas on a single wavelength isn't really an option either for us, as we are aware of a number of cases where the known impurities in our products either don't absorb at an appropriate wavelength for the product, or do so weakly and therefore a single wavelength gives a falsely high result for purity.

Is it possible therefore to implement either a direct equivalent to the Spectrum Max Plot in Clarity, or even better, implement an equivalent to a TIC in a GCMS system and sum all the absorbances rather than choosing the maximum for any given time point? I'm assuming that all the data is already present in the system due to the spectra being recorded so hopefully this is more simple to program than it appears?

Also, as an extra - if this is possible, would it also be possible to adjust the wavelength that this uses separately to the PDA acquisition wavelengths? For example PDA acquiring between 210nm to 370nm and the Max Plot displaying say 230nm to 300nm - I'm aware that having the Max Plot greater than the PDA acquisition isn't an option for obvious reasons.

Alex
Internal issue tracking ID: 61937

[Daniel Mentlik]

Dear Alexander,
such feature (if implemented) would be most probably an equivalent to MS BPI (Base Peak Intensity) signal. However, it would have to be programmed in the control module. May you let us know the serial number of Clarity station(s) used (can be found using Help - About... from the main Clarity window) and the instrumentation used at the stations (mainly the type of the PDA detectors)?

[Alexburness]

Daniel,

Many thanks for your (very) quick response.

The Serial number of our demo station is 011-56650, and the system is a Shimadzu LC10 (SCL-10AVP & LC-10ADvp) with a SPDM10AVP as the PDA.

Regards,
Alex

[Daniel Mentlik]

Dear Alex,
the suggestion for MaxPlot for Shimadzu LC System is already in our database, internal tracking number ISS61937. I have added a poll to the thread.

Please note that there are certain possibilities to do similar actions like you desire already for Shimadzu PDA detectors, namely:

• you can set the method so that one of the mentioned four signals is collected over wider range of wavelengths. On the Method Setup - Acquisition there is a setting for a Wavelength and Bandwidth (default is 1) that defines which wavelength(s) will be used for the signal. If you set for example the Wavelength to 250 and Bandwidth to 100, you will have an equivalent to MS TIC collected over the 200-300 nm range. However, the Bandwidth range is limited to 100 by MIMIC libraries used for controlling the Shimadzu LC System, not allowing to do the real TIC for the whole spectrum 190-800 nm.
• you can create the whole TIC signal from the already measured chromatogram manually from the PDA Chromatogram window by using the Chromatogram - Add Signal... command and specifying the Wavelength and Bandwidth there in the same manner (without any limitations on Bandwidth other than maximum spectral range). However, this must be done manually for each chromatogram (cannot be automated by method) and thus is not too suitable for calibrating on the signal.

I hope at least one of the approaches helps you at least a bit in your workflow.

[Alexburness]

Daniel,

Thanks for your assistance and suggestions.

If this does get implemented for the Shimadzu PDA module, how likely is it to get implemented for other PDA modules?

Whilst we have no plans to replace our Shimadzu, at some point in the indeterminate future this is likely to be needed and it would be useful to be able to straight away use this feature, whichever Clarity supported system we choose.

[Daniel Mentlik]

Hard to say. Once the feature is implemented in one of the control modules, implementation to other DAD modules is significantly faster/easier. However, not all of the modules were developed at DataApex (Knauer DAD modules, new Sykam DAD, ...) and for these the feature would have to be implemented by the manufacturer (that is not something we can enforce). For the other significant DAD detector controlled by Clarity, Agilent 1200/1220/1260/..., we are using ICF framework developed by Agilent which is probably not flexible enough to override the settings. New feature request specifying the needed functionality for particular DAD would be needed.