Shim-pack MAqC-ODS I reversed-phase columns are packed with a silica gel containing metal and added octadecylsilyl group. In

addition to the hydrophobic characteristics of the ODS, the metal content also provides cation-exchange effects. This increases the retention of basic compounds. Therefore, this allows use with only a buffer solution as the mobile phase for analyses that previously required using an ion pair reagent and enables using gradient elution.
These characteristics are especially beneficial for analyzing water soluble vitamins and pharmaceuticals that contain a large amount of basic compounds.
Example of Simultaneous Analysis of Water Soluble Vitamins
Water soluble vitamins contain many highly polar basic components, which are known to exhibit weak retention in the reverse-phase mode. Consequently, with typical ODS columns, such as the Shim-pack VP-ODS, an ion pair reagent is added to the mobile phase for analysis. However, using an ion pair reagent makes gradient elution difficult, resulting in peak broadening for components that take longer to elute and making it difficult to improve sensitivity. In addition, the effort required to prepare the mobile phases and condition the column is also an issue.
However, because the Shim-pack MAqC-ODS I enables using gradient elution, it can shorten analysis times and result in sharp peaks even for components that elute slowly.
For example, riboflavin, which elutes as the final peak with a typical ODS column, is detected with approx. 2.3 times higher sensitivity by the Shim-pack MAqC-ODS I.
Shim-pack MAqC-ODS I
Column size |
150 mmL. x 4.6 mmI.D., 5 μm |
Mobile
phase |
A) 10 mmol/L phosphate (Na) buffer
solution (pH 2.6)
B) Acetonitrile
|
Time program |
B Conc. 1% (0 min) → 1% (2.5 min) →
50% (10 min) → 1% (10.01 min → 15
min) |
Detection |
UV 210 nm |
Flow rate |
1.2 mL/min |
Injection
volume |
10 μL |
Column temperature |
40 °C |
Shim-pack VP-ODS
Column size |
150 mmL. x 4.6 mmI.D., 5 μm |
Mobile
phase |
A) 100 mmol/L phosphate (Na) buffer
solution (pH 2.1) containing
0.8 mmol/L sodium 1-octanesulfonate
B) Acetonitrile A/B = 10/1 (v/v)
|
Detection |
UV 210 nm |
Flow rate |
1.2 mL/min |
Injection
volume |
10 μL |
Column temperature |
40 °C |
Example of Analyzing a Cold Remedy
Gradient elution with a Shim-pack MAqC-ODS I column was used for simultaneous analysis of components contained in an over-the-counter commercial cold remedy. The ability to use gradient elution enables the acquisition of sharp peaks, even for components that eluted slowly, similar to the water soluble vitamin and drug impurity examples above.
To use this column efficiently: 1) To increase the retention of basic compounds, please use a buffer solution within the pH 2 to 4 range. 2) In the case of a basic substance tailing, it may be possible to improve the peak shape by increasing the salt concentration of a buffer solution. 3) The elution of basic compounds is faster by increasing the salt concentration, and it is possible to adjust retention by salt concentration.