Shodex Column Selection for Vitamin D Analysis in Oil-Based Matrices

Record: 564

Category: Column Selection
Product: KF-801
Sample: Vitamin D

Question

A customer is analyzing vitamin D in an oral solution formulated in a peanut oil vehicle. They have tested multiple reversed phase columns (L1 and L7, 4–5 µm, 250 mm) and various mobile phases including methanol, THF, isopropanol, and hexane/THF mixtures.

The sample is diluted to 8–10 ppm. The main issue is poor separation and lack of reproducibility, with interference from the oily matrix (peanut oil), making it difficult to clearly detect and quantify the vitamin D peak.

What Shodex column and approach are recommended?

Answer

For analysis of vitamins in oil-based matrices, size exclusion chromatography (SEC/GPC) is typically more effective than reversed phase methods. In this approach, separation is based on molecular size rather than polarity, allowing large oil components to be separated from smaller target analytes such as vitamin D.

Shodex KF series columns are designed for organic SEC applications and are suitable for separating low molecular weight compounds from high molecular weight matrix components such as triglycerides and oils.

Shodex KF-801 is a recommended starting point for this type of analysis. This column has dimensions of 8.0 mm I.D. × 300 mm with a 6 µm particle size and a pore size of approximately 50 Å, making it suitable for separating low molecular weight compounds from larger oil-based matrix components. It enables separation of the bulk oil fraction from the vitamin, which can improve baseline stability, peak visibility, and reproducibility.

This approach is particularly useful when oily excipients co-elute or interfere under reversed phase conditions. By separating based on size, the bulk oil fraction elutes separately from the vitamin, reducing matrix interference.

Method conditions such as solvent selection (e.g., THF) and sample preparation should be optimized to ensure complete solubility of the sample and compatibility with the column.

Recommended Applications:

• Fat-Soluble Vitamins (3) (KF-801)
• Margarine

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