| Column | Purospher® STAR RP-18 endcapped (5μm) LiChroCART® 150-4,6 HPLC column |
|---|---|
| Mobile Phase | Methanol / Water 80:20 |
| Flow rate | 1.0 mL/min |
| Detection | UV 254 nm |
| Temperature | 30° C |
| Inj. Volume |
10 μl |
| Sample | 1. Uracil 2. Butylbenzene 3. o-Terphenyl 4. Pentylbenzene 5. Triphenylene |
 |
Tanaka Test |
Chromatographic Characterization of Column Properties
Controlling the physical and chemical properties of stationary phases is important. However, only comprehensive chromatographic characterization ensures a consistently high level of reproducibility. Therefore, various approaches have been applied by leading HPLC scientists to characterize selectivity.
The Tanaka* Test is established worldwide as the industry standard for evaluating the selectivity and performance of different HPLC columns. These parameters not only simplify column comparison, but also facilitate the selection of the most suitable HPLC column for a particular separation.
A set of seven selected substances are used to describe capacity, hydrophobicity, steric selectivity, and silanophilic properties. The values of these parameters are outlined on the six axes of a hexagon, illustrating the quality of a sorbent at a glance.
The more symmetrical the hexagon appears and the larger its area, the more balanced the stationary phase is in the sum of its chromatographic properties.
* Prof. Tanaka, Kyoto Institute of Technology, J. of Chrom. Sci. 27, 725, 1989
Parameters According to Tanaka for the Characterization of Purospher® HPLC Sorbents
| Parameters | Property of stationary phase | Factors in preparation of the stationary phase | |
|---|---|---|---|
| k (Pentylbenzene) 80% Methanol |
Retention capacity (A) |
Amount of alkyl chains | Silica surface Silica coverage |
| k (Pentylbenzene) / k (Butylbenzene) 80% Methanol |
Hydrophobicity (B) | Hydrophobic capacity (CH2-group selectivity) |
Surface coverage |
| k (Triphenylene) / k (o-Terphenyl) 80% Methanol |
Steric selectivity (C) | Steric (shape) selectivity | Silane functionality Surface coverage |
| k (Caffeine) / k (Phenol) 30% Methanol |
Silanol capacity (D) | Silanol capacity (content and type of silanols) | Residual silanols Endcapping Surface coverage |
| k (Benzylamine) / k (Phenol) 30% Methanol / 70% Phosphate buffer pH 7.6 |
Ion exchange capacity (E) | Ion exchange capacity at pH 7 |
Residual silanols Active sites at pH 7 |
| k (Benzylamine) / k (Phenol) 30% Methanol / 70% Phosphate buffer pH 2.7 |
Ion exchange capacity (F) | Ion exchange capacity at pH 3 |
Active sites at pH 3 Treatment of basic silica (metal impurities |
Tanaka Tests for Purospher® STAR RP-18 Endcapped
Tanaka 1: Retention Capacity, Hydrophobicity, Steric Selectivity
The Tanaka 1 Test describes the retention capacity, the hydrophobicity, and the steric selectivity of RP-phases.
Tanaka 2: Silanol Capacity
The Tanaka 2 Test (Chromatogram A) illustrates the silanophilic properties of stationary phases. Chromatogram B is not part of the Tanaka 2 Test. The Phenol/Pyridine test measures silanol activities.
Tanaka 3 and 4: Ion Exchange Capacities
The results obtained from the Tanaka 3 Test (at low pH) demonstrate whether the deactivation of the residual silanol groups is complete. The Tanaka 4 Test (at high pH) indicates the complete absence of metal in the base sorbent.
Tanaka Test Results for Purospher® STAR RP-18 Endcapped
When compared with other brands of "high purity" RP-18 endcapped columns, Purospher® STAR RP-18 endcapped demonstrates the best overall selectivity, making it the column of choice for successful HPLC separations.
| A. | K (Pentylbenzene) | 9.59 |
| B. | α (Pentyl-/ Butylbenzene) | 1.51 |
| C. | α (Triphenylene/ o-Terphenyl) | 1.63 |
| D. | α (Caffeine/ Phenol) | 0.44 |
| E. | α (Benzylamine/ Phenol; pH 7.6) | 0.23 |
| F. | α (Benzylamine/ Phenol; pH 2.7) | 0.02 |
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