Quality Control

Vol. 2, No. 6
Functionalized SILICA GELS for Organic Synthesis

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Introduction / Quality Control / Organic Synthesis / Scavengers
Supported Reagents / Linker Resins / References

Quality Control

In order to assure the highest quality products, each batch of UltraPure Silica Gel undergoes a four-point verification procedure:

  1. Elemental analysis for organic and inorganic compounds
  2. BET analysis (surface area determination)
  3. pH
  4. Particle size determination

Our Four-Point Quality Control Procedure

Elemental Analysis of Organic and Inorganic Compounds
These silica gels have very low organic compound levels. The gels are subjected to Carbon-Nitrogen-Sulfur analysis to determine organic content.

Most silica gel available on today’s market likely contains up to 0.5% of different metal oxides. Iron is usually the most abundant oxide, but copper, cadmium, zinc and aluminum, to name a few, may also be present and act as Lewis acids. Such acids can affect or even destroy some products. Peak tailing, occasionally observed in polar compound separation, is another major problem associated with high metal content in silica.

This silica gel is analyzed by ICP-MS for over 40 metals, to ensure that every batch has a very low metal content to prevent the above-mentioned problems .

BET Analysis
The efficiency and reliability of silica gel depends on surface conditions. BET analysis determines the surface area, pore diameter, pore size distribution and volume. All these parameters are closely linked to silica gel performance in separating compounds.

A larger surface area results in greater contact or interactions with the analyte, thereby increasing the separation of different products. Pore diameter, distribution and volume permit semi size-exclusion chromatography, where smaller molecules fit into pores more easily than larger ones (e.g. in peptide separations). This justifies the use of several types of silica gels to achieve better discrimination in chromatographic processes.

The silica gel pH can affect the retention time of some ionizable compounds. However,some products become hydrolyzed or are rearranged on contact with acidic silica. A neutral pH with a range between 6.5 and 7.0 is the most important factor in determining the reliability and inert behavior of silica gels.

Particle Size
Silica gel with a narrow particle size distribution will ensure easily packed columns. We verify that 90% of the particle size fits in the range provided.

We also test our functionalized silica gels by performing test reactions and by following these reactions by GC-MS and in situ FTIR, thus ensuring that our functionalized silica gels perform as well as we claim.