Frequently Asked HPLC and Ion Chromatography Questions



Below is a selection of frequently asked questions.  In addition, the answers to many queries may be found in user manuals and other Cecil documentation.  Otherwise, please contact us on info@cecilinstruments.com or

telephone +44 (0) 1223 420821, for detailed information and answers to your queries.































We would like to use Cecil HPLC/Ion Chromatography in our laboratory, but no one has any knowledge or experience of Cecil HPLC/Ion Chromatography.  Please could you advise?


We do appreciate that this may be a daunting prospect, we at Cecil Instruments have experienced chemists, biologists and engineers who should be able to help.  You or your distributor will be able to install the instrumentation.  We have documents and manuals on the installation and use, of our chromatography instrumentation and our 21 CFR part 11 compliance PowerStream software.  


We also can provide application notes for methods of analysis of specific compounds, within specific sample groups.  



The Cecil HPLC/IC systems sound good, but I do not wish to be the first in our market, to use their systems.


You probably will not be.  There are many Cecil users, throughout the world, who use Cecil instrumentation.  Some of these users have published academic papers on their research and have cited the use of Cecil instrumentation.  Page: HPLC-ion-chromatography-citations



There is a bewildering choice of instrument modules, do I need them all, which ones should I use?  Do I have to purchase all of the modules at the same time, or can I add as and when required?


The beauty of the Cecil Adept, IonQuest or Q-Adept HPLC systems, is that they are modular, so that modules, such as extra pumps, detectors, autosamplers, column heater/chillers, post column reactors, fraction collectors etc., may be added at any time after the purchase of the main system.  


Please contact us with details of your anticipated analysis/es.  We can then advise on the most appropriate modular system, which will meet your immediate needs, but will leave room for addition as/when/if you require it.  



What is the WaveQuest detector?


The WaveQuest is an ultra-fast scanning UV/Visible HPLC detector, which provides on-the-fly ultra-fast spectral scanning of chromatographic peaks and due to its ultra-low noise, up to 100 times more sensitivity than diode array detection.  So instead of needing to use a separate diode array detector to provide spectral information to check the purity of the eluted peaks, and then another separate variable wavelength detector to detect and measure tiny quantities, we offer just one single detector, the WaveQuest.


The WaveQuest detector also has ultra low drift.  This is particularly useful for use with an autosampler in overnight or weekend runs.


Consequently, the WaveQuest detector has the advantages of a diode array detector, but none of the disadvantages.  



I recently purchased a new analytical column for my HPLC system.  I have attached it to an existing system, which was working, but now my pump keeps stopping with signs of overpressure.  This is a brand new column, so it cannot be blocked.  Please may I have an engineer call-out?


Before any solvent is placed in contact with the column, check for normal/reverse phase compatibility.


The column will be supplied immersed in a storage solvent.  If the storage solvent is hexane or a non-polar solvent and reverse phase analysis is required, then the hexane/non-polar solvent must be replaced with an aqueous/polar phase.


The column manufacturer will often supply instructions for the change of phase.  In general, pass twenty times the column volume of an intermediate phase which is miscible with both hexane/non-polar solvent and the aqueous/polar phase, such as ethanol or isopropanol.  Then pass through pass twenty times the volume of the required aqueous phase.

These directions apply in reverse if the storage solvent is an aqueous/polar phase.



I have just finished a project, where the mobile phase has a large proportion of acetonitrile.  The HPLC system will now be idle for a few months.  Do I need to clean the acetonitrile from the system?


Acetonitrile is not kind to check valve seals, as it tends to makes them ‘stick’  after acetonitrile has been used.  So after an acetonitrile mobile phase has been used for a project, it is useful to purge the HPLC system with 85%/15% water/methanol.



What is an anion suppressor, and when do I need one?


In ion chromatography, the conductivity detection of anions often involves the use of a conductivity detector and an anion suppressor.  


Many mobile phases used in the conductivity detection of anions contain sodium bicarbonate and sodium carbonate.  Sodium bicarbonate and sodium carbonate themselves contain anions groups, so will interfere with a chromatogram by increasing the level of the baseline.  An anion suppressor, chemically removes sodium bicarbonate and sodium carbonate from the mobile phase, before the mobile phase enters the conductivity detector.  Hence the baseline of chromatograms remains at a relatively low level of conductivity.  


Anion suppression is necessary, when performing high sensitivity measurements, using sodium bicarbonate and sodium carbonate mobile phases.






















I am using an IonQuest conductivity detector for the first time.  I do not know what signal range to expect.  What would you suggest?


The signal range depends on the expected concentrations.  If low concentrations are expected, then a low value range such as 20 µS/cm would be a good starting point.  If high concentrations are expected, then a high value range such as 2 mS/cm would be a good starting point.  You can later modify the signal range displayed in your resulting chromatograms.



With my conductivity detector, what signal offset should I use?


The signal offset will vary depending on the type of mobile phase used and its concentration.  The offset allows the baseline to be visualised.  The offset should be a lower value than that of the range, if the offset is too high, the baseline will be high.  An offset of 0.0 µS/cm is a good starting point.



Despite making several chromatographic runs, the signal readout on my ion chromatography conductivity detector is a constant 37 µS/cm.  Should I send back the detector, as it is unresponsive?


It would appear that the ‘simulated cell’ option has been inadvertently set.  The simulated cell option allows the noise and drift performance to be evaluated without solvent.  


Switch off the simulated cell as follows:-


1. Press the MODE key. The LED on the key flashes.

2. Press the MODE key to run through the options in the menu until the ‘Configuration’ option is displayed.

3. Press the E key to select the option.

4. Press the ARROW keys until the ‘Simulated Cell’ option is displayed.

5. Press the E key to select the option. You are prompted to enter either 0 for no simulated cell

(normal operation).

6. The instrument switches off the simulated cell.



Help!  I am using a conductivity detector for the analysis of cations, but the peaks on my chromatogram are negative!


As the same conductivity detector is used for both anions and cations, the polarity of the charge of one will be the opposite of the other.  This means that the signal (y axis), normally expressed in micro Siemens per second (µS/cm), will produce negative peaks for one set of ions.  If negative analyte peaks are observed, then the polarity of either/both the offset and the range should be reversed, so for example, the reverse of the polarity of a range of 50 µS/cm, is -50 µS/cm.



With PowerStream software, I have set up my Acquisition sequence and my run has started, I see signal values displayed on the detector screen, but I cannot see any chromatogram trace.  What is happening?


Within PowerStream software, whilst your acquisition sequence is running, it is possible to alter the signal axis, in order to magnify or minimise the observed signal.


Towards the bottom left of the Sequence table, there is a pause icon.  Click on the icon.  This only pauses the on-screen view of the acquiring chromatogram.


At the bottom left of the Sequence table, there is a double arrow head icon.  Click on this on icon to change the values of the time and signal axes.


Click the pause icon to view the changed axes of the acquiring chromatogram.



I am using DataStream software, what is the maximum storage capacity of its spectral library?


Spectra, chromatograms, and time plots may be saved within the library.  The library is held on the hard drive of the computer used, hence the storage capacity of the library is dependent on the amount of the available hard drive memory.  Data may also be directly saved onto any PC removable medium.



I have lost the original user manuals, which accompanied the modules when I originally purchased them.  I cannot find a section on your site for user manuals.


Sorry, but our replacement manuals are not available electronically. This is because different versions of the same instrument model may be in use, and we wish each specific replacement manual to match the exact version of the instrument, which a person may be using.


Hence we can only supply hard copy replacement manuals.  Please contact your local distributor for ordering details.


On placing the order with the distributor, please provide the serial number/s of the  instrument module/s concerned, so that the appropriate version of the manual/s  are sent.

A chromatogram depicting picogram levels of Catecholamines by HPLC with electrochemical detection.

Chromatogram of 0.4 ppm bromide in the presence of

5 ppm chloride, by conductivity detection.

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