the sample I got was L-Rhamnose monohydrate but its reagent grade. Is just filtering enough to make it HPLC grade? Or are there other methods. I am going to use the rhamnose in order to make a standard curve. Really hope to hear your feedback.
Dear Dan,
a single filtration is not able to make a L-Rhamnose monohydrate reagent grade become a HPLC grade. HPLC grade reagents are generally controlled for high assay and low residues and water.
Usually an HPLC grade is 99% purity since even 95% can have hundreds of organic impurity peaks similar to your molecule of interest. I doubt very much simple filtration would be adequate.
TLC is generally much less capable to check sugars for impurities. The highest separation power affords anion-exchange LC in combination with electrochemical detection ("Dionex method"). Filtration (0.22 µm) removes only particulates and does not improve purity. Carbohydrate columns based on cation-exchange resins (preferable Pb-form) and those based on amino-silica (using acetonitrile/water) are more or less complementary in separation properties can be used (preferably both) to asses the purity of the rhamnose. What are the specifications of the supplier? Determination of water content by Karl-Fisher should complete the information.
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