Sugar and sugar alcohol analysis

Record: 83

Category: Column Selection
Product:
Sample: lactulose, rhamnose, 3-methylglucose and mannitol

Question
Here, study subjects are given lactulose, rhamnose, 3-methylglucose and mannitol in a drink. I must detect these nonmetabolizable sugars and sugar analogs in blood plasma and urine. I tried derivatizing them variously and detecting them by GC-MS and LC-fluorescence. I also tried detecting them by LC-MS on a weak cation exchange silica-bead column loaded with silver ions. In all cases, I detected them, but in all cases, the peaks, particularly lactulose, were not sufficiently separated from peaks from the plasma or urine. For the silver column, I clean up samples first with mixed-bed ion exchange resin.

Why are Shodex SUGAR columns all so wide? The HPLC devices connected to my best MS equipment operate at lower flows (<100 uL/min). Can Shodex pack an 0.5 or 1mm i.d. column? 2.1 mm?     Answer
Unfortunately, we do not make smaller i.d. SUGAR columns.
However, I am thinking that you might be interested in using our amino column, NH2P-50. It is available in 2.0 mm i.d. x 150 mm length , or even smaller sizes (please see pg64 on the catalog).
NH2P-50 column is suitable for sugar separations. The attached link explains more details.
http://shodex.net/data/downloads/Shodex_Technical_Notebook_2_NH2P50.pdf

It indicates the elution volume of lactulose, rhamnose, and mannitol as 10.72, 5.52, and 7.39 mL respectively.
The elution volume of glucose is 8.61 mL but we do not have a data for methylglucose separation. In general alkyl group will shorten the retention.
Since we do not have a data available, I’m afraid but we cannot guarantee the baseline separation of mannitol/rhamnose and methylglucose as of now. However, you may be able to optimize their resolutions by using gradient elution.

Do you have any idea what is the interfering peak from urine/plasma? With the limited information I cannot say for clear that those peaks will co-elute with lactulose or not. As a pretreatment for NH2P column, it will require anion removal (cation removal is not required) and at the same time, it should remove the protein from the sample.

 
 
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