By Anonymous on Tuesday, June 15, 1999 - 06:25 am:
Internal standard are common in CZE analyses to
improve the system precision. However, the use
of an internal standard may be rather complicated
when using indirect UV detection (usually a simple
buffer system is preferred). Does anyone have
experience using internal standards for the analysis of oligosaccharides?
By Tim Wehr on Monday, August 9, 1999 - 05:17 pm:
Can you use a mono- or oligosaccharide not present in your sample? Many CE systems (HP, Beckman, Bio-Rad) have the capability of performing a second injection before or after the sample injection to introduce an internal standard; this avoids the necessity of adding the internal standard to the sample solution. I have used this technique to add pI markers as internal standards in capillary isoelectric focusing.
Can you describe the indirect method you are using for oligosaccharides? I have analyzed monosaccharides in wine using sorbate as the background electrolyte with indirect detection at 250 nm. An electrolyte pH of above 10 is necessary to ionize the sugars, and migration time variability is a problem under these conditions. Use of an internal standard would be very desirable in this system. Fortunately, wine contains mostly glucose and fructose, and selection of an internal standard is simplifed.
Tim Wehr
Bay Bioanalytical Laboratories