The Quality Control Department's objective is to provide default free products. In light of this goal, we have determined the critical points that need to be addressed for each product line. These points are based on customers and sales representatives’ recommendations as well as from the scientific knowledge of our employees.
Each product family has its own quality control procedures and every procedure is strictly followed. The QC tests results are checked and confirmed by the person in charge for them before signing off for shipping. Complete procedures for each product line are available upon request.
Thus, SiliCycle is committed to high quality standards. In doing so, every product meets the quality specifications determined. All products are shipped with a Certificate of Analysis (CofA) and a sample from every batch is kept for subsequent analysis. If you feel that the product you have received does not meet these specifications please contact us and we will make sure you are satisfied.
The backbone of most SiliCycle’s products is SiliaFlash® F60 silica gel. It provides superior performance for chromatographic applications due to its narrow particle size distribution and high purity.
Before functionalization, all silica is rigorously characterized and analyzed as follow to ensure lot-to-lot reproducibility.
|Carbon, nitrogen and sulfur analysis:||Performed by elemental analyzer.|
|Total trace metal:||Performed by ICP-OES|
|Surface area and porosity:||Performed by nitrogen adsorption analyzer|
|Particle size distribution:||Performed by laser light diffraction analyzer|
|Water content:||Performed by moisture balance|
|pH:||Performed by pH-meter|
|Tapped density analysis:||Density measurement|
Elemental analysis of organic compounds
SiliaFlash gel has a very low organic content. All lots are subjected to elemental analysis to determine the carbon, nitrogen and sulfur levels.
Total trace metal analysis
To improve the quality of the separation, SiliCycle manufactures silica gels with very low trace of metal content. All silica gels are analyzed for more than 45 metals by ICP-OES (ppm level), and reach up to 99.4 % of pure silica. This gives silica with no problem of metal oxide that may act as Lewis acids and no “tailing” of most polar compounds (frequently ionizable) caused by silica with a high metal content.
Surface area and porosity analysis
The efficiency and reliability of silica gel depend on its surface condition. We use the Brunauer Emmet and Teller analysis to determine the surface area, and the Barret-Joyner-Hatenda method to determine the pore diameter and pore volume of the silica gel. A larger surface area results in more contact or interaction with the analyte, thereby increasing the segregation of different products. Pore diameter and pore volume permit semi-exclusion chromatography where smaller molecules fit into pores more easily than larger ones. This justifies the use of several types of silica to achieve better discrimination in chromatographic separations.
Particle size distribution analysis
Particule size distribution is determined by laser diffraction. Usually, more than 90% of the silica gel is kept within the granularity range.
Water content analysis (Silica gel activity)
The amount of water on the silica’s surface affects chromatographic performance. An anhydrous silica gel will be extremely polar, while a wetted one will be considerably less so. Every batch is carefully adjusted to a specific percentage of water content.
The pH can increase the retention of some ionizable compounds. However, some products can become hydrolyzed or rearranged in contact with acidic silica. A neutral pH, with a range between 6.5 and 7.5, is the most important factor in determining the reliability and inert behavior of the silica. This pH test involves suspending the silica gel in pure water (10% w/w).
Tests on functionalized Silica
The process for functionalizing the silica is highly dependent on the group being attached. However, it is still possible to functionalize 90% of the surface, verified by silicon (Si) NMR. The remaining 10% of the surface may be end-capped to provide a completely inert support. After being functionalized, the product is submitted to further analysis and quality control as outlined below.
|Purity analysis:||Performed by GC-MS.|
|Carbon, nitrogen and sulfur analysis:||Elemental analysis of organic compounds is performed by elemental analyzer.|
|Chromatographic analysis:||Performed by LC-MS or HPLC.|
|Infrared analysis:||Organic function signature analysis is performed by Infrared spectroscopy.|
|Residual solvents content analysis:||Content is performed with moisture balance|
|Reactivity analysis:||Specific reactivity test of the organic function is performed by GC-FID, GC-MS and ICP-OES.|