Sugar quantification with IC - conc. range and ECD queries

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Hi everyone,

I currently use a Dionex IC with Electrochemical detector for sugar quantification. I use a CarbonPac PA20 column and 200mM NaOH. For years, we have used a standard concentration range of 5 - 20 mg/L for the standard peak. For this, we have had to dilute our samples 100 - 200 dilution factor. Sometimes, we have had to go up to DF 400! As you know, this is a difficult task and leads to pipetting errors.

(1) Can I use a higher concentration range for this? Even going up to 100 - 200 mg/L can reduce the amount of dilution.

(2) I am new to using an ECD. How often should I change the electrode? How will I know it is time to change it?

Thank you for your help in advance.
Hi,


I work whith a PA10 and 400mM NaOH,my standard concentration range is to
1-100 ppm and my LOQ 0.05%, my dilution factor is 1000 its ok and R 0.9999

I recommend you change every 6 months to reference electrode ph P/N 061879 and that you work whith disposable electrodes P/N 066480


Regards
Hi anahita.b,

You may want to review Technical Note 186: The Effect of Working Electrode Gasket Thickness on the Sensitivity and Linearity of Carbohydrate Response by Pulsed Amperometric Detection and consider a thicker gasket and/or use of a 0.4 µL internal injection loop to reduce dilutions.
Best regards,

John Guajardo
Product Manager, IC Columns
Thermo Fisher Scientific
Hello Anahita,


1 A full calibration curve, over a wide concentration range, may look like this:-

Image


Parts of these curves are not linear. It may be that the originators of your method were aware of this and therefore created a routine method where your standard concentration range is 5 - 20 mg/L and your samples should fall within this range.

The most accurate dilutions are serial dilutions. You should consider this type of dilution for your samples.

As a hypothetical example, to go from a 1,000 ppm concentration to a 0.1 ppm concentration of a liquid sample:-

Accurately take 1 mL of the 1,000 ppm sample, add to a 100 mL grade A volumetric flask, and make up to 100 mL in HPLC grade deionised water. Stopper and mix well (this is the 10 ppm sample).

Then accurately take 1 mL of the 10 ppm sample add to a 100 mL grade A volumetric flask, and make up to 100 mL in HPLC grade deionised water. Stopper and mix well (this is the 0.1 ppm sample).

For the ultimate in accuracy, you can dilute samples more slowly with more, but larger volume sample aliquots.


2 If you observe an unexplained increase in background current, noise or drift, then the electrodes may be passivated and/or polished. If passivation does not solve the problem, then consideration may be given to replacement. Please refer to the manufacturer’s user manual.
Kind regards,
Ade Kujore
Marketing
Cecil Instruments
Cambridge
United Kingdom

email:- ade.kujore@cecilinstruments.com
telephone:- +44 (0) 1223 420821
web site:- www.cecilinstruments.com
Registered Number 909536
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