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The Inertpak family of LC columns from Capital Analytical is based on a completely new type of Silica Gel which exhibits a remarkable degree of chemical inertness and stability. The Inertpak range is therefore particularly effective in the analysis of amines, basic pharmaceuticals and other chemical species where hydrogen bonding may occur. This also makes Inertpak columns generally suitable for the vast range of non-basic applications currently performed on older technology stationary phases.
In the reversed phase analysis of basic/amine compounds, severe peak tailing can occur. This is due to the presence of surface silanol groups which remain after the derivatisation procedure. End capping with trimethyl siloxane groups helps to eliminate surface silanols, but is never completely successful. The material used for the Capital Analytical Inertpak column family represents an innovative solution to the problem of residual silanol interactions.
Specifications
Shape: Spherical
Particle Diameter: 5 micron
Carbon Loading: C8(10.5%), ODS2(18%),ODS-80Å(17.5%)
Pore Diameter: ODS2 (150Å or 80Å), Ph,C8,C4(150Å)
Surface Area: 320-350m2/g, 450m2/g (ODS-80Å)
Typical Efficiency: 75,000 plates/m
Surface silanols are known to undergo self-ionisation leading to fixed negative charges on the surface of the material. This leads to strong electrostatic interactions with the protonated regions of ionised basic molecules and results in severe peak tailing.
Figure 1
Free silanol (moderately acid)
Figure 2
Metal activated silanol (strongly acidic)
The tendency for a silanol group to undergo self ionisation depends on its electronic environment and is exceptionally strong when the adjacent silicon atom is substituted by a metallic impurity. Figures 1 and 2 above illustrate the stabilising effect of metal impurities on ionised silanols.
Existing silica technology produces LC packing materials which contain substantial amounts of metallic impurities, notably sodium and iron which lead to the presence of highly activated silanols which contribute to peak tailing.
The inert silica used in Inertpak columns uses a synthesis route producing a high purity material with a very low metal content. Consequently residual silanols following the end capping process are inactive and thererfore do not create the interactions which cause peak tailing.
In addition to the inertness towards basic compounds, Inertpak columns can also be operated over a wider pH range than conventional materials. The above tests illustrate the good stabilitly of Inertpak in contact with agressive mobile phases at high and low pH values.
New packing materials create more stringent requirements when it comes to packing procedures. The proprietary packing protocol, designed by our development laboratory, allows us to supply columns in all formats from capillaries to preparative scale columns, exclusive to Capital Analytical. This packing procedure, in concert with Capital Analytical's stringent quality control assures you of reproducible cost effective analysis.
Figure 3 shows the elution of the strongly basic anti-depressive drug, Amytriptyline on a standard ODS material, a leading base deactivated ODS material and Inertpak. In the case of the standard ODS, only the unretained marker elutes. With the base deactivated material the Amytriptyline elutes but it is strongly tailed. With Inertpak, the Amytriptyline elutes with an excellent peak symmetry.
Figure 3
Sample and Run Conditions: 1. Uracil, 2. Amytriptyline, All columns 15cm x 4.6mm i.d., mobile phase 60:40 20mM KH2PO4:Acetonitrile, Flow Rate: 1.0ml/min.
Prices listed in the tables below and refer to 4.6mm i.d. and 3.2mm i.d. columns of various lengths. For dimensions not listed, please contact sales office. Please note, high performance narrow bore (2.1mm and 1.0mm i.d.) columns are also available. To find the appropriate part number, choose the bonded phase and look along the table for the length of column required.
Length |
Phase |
Cat. No. |
Price (£) |
|
2cm (Guard) |
Silica |
5MA102 |
|
5cm |
Silica |
5MA105 |
|
10cm |
Silica |
5MA110 |
|
15cm |
Silica |
5MA115 |
|
20cm |
Silica |
5MA120 |
|
25cm |
Silica |
5MA125 |
|
2cm (Guard) |
C4 |
5MD102 |
|
5cm |
C4 |
5MD105 |
|
10cm |
C4 |
5MD110 |
|
15cm |
C4 |
5MD115 |
|
20cm |
C4 |
5MD120 |
|
25cm |
C4 |
5MD125 |
|
2cm (Guard) |
C8 |
5MF102 |
|
5cm |
C8 |
5MF105 |
|
10cm |
C8 |
5MF110 |
|
15cm |
C8 |
5MF115 |
|
20cm |
C8 |
5MF120 |
|
25cm |
C8 |
5MF125 |
|
2cm (Guard) |
ODS-2 |
5MG102 |
|
5cm |
ODS-2 |
5MG105 |
|
10cm |
ODS-2 |
5MG110 |
|
15cm |
ODS-2 |
5MG115 |
|
20cm |
ODS-2 |
5MG120 |
|
25cm |
ODS-2 |
5MG125 |
|
2cm (Guard) |
Phenyl(Ph |
5MK102 |
|
5cm |
Phenyl(Ph |
5MK105 |
|
10cm |
Phenyl(Ph |
5MK110 |
|
15cm |
Phenyl(Ph |
5MK115 |
|
20cm |
Phenyl(Ph |
5MK120 |
|
25cm |
Phenyl(Ph |
5MK125 |
|
2cm (Guard) |
ODS(80Å) |
5ML102 |
|
5cm |
ODS(80Å) |
5ML105 |
|
10cm |
ODS(80Å) |
5ML110 |
|
15cm |
ODS(80Å) |
5ML115 |
|
20cm |
ODS(80Å) |
5ML120 |
|
25cm |
ODS(80Å) |
5ML125 |
|
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