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CAPCELL PAK C18 MGIII Type
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About MGIII···
The third generation of the MG series was developed to overcome the "Column-to-column variation in retention of basic compounds under an acidic condition". We hope that the quality of MGIII will help develop improved methods in various LC-MS applications.
Hydrophobicity and surface polarity parameters of popular C18 columns
Intended to be the "standard" for LC-MS
While it is based on the identical silica used in other MG series, CAPCELL PAK C18 MGIII possesses a weaker hydropobicity and a stronger surface polarity, and is suitable for a wide variety of applications, such as analyses of metabolites and other highly polar compounds. Especially, its reproducibility in retention times of basic compounds under acidic conditions is a preferred feature for long time-span applications, such as clinical analyses with LC-MS, and applications under GLP. (MGIII's specifications include a separation performance of amitriptyline under an acidic condition.)
Features
Fig.1 : Example of lot variation under an acidic condition

Fig.2 : Optimization of pre-conditioning time

Fig.3 : Spectral difference in 29Si-NMR

An example of column-to-column variation under an acidic condition is shown in Figure 1. The compound used here was amitriptyline, a highly basic compound used for the USP evaluation method. The results were obtained under an isocratic condition (0.1% formic acid / methanol). Retention times of the three columns (Column A, anonymous) were found very different under the mobile phase that was one of the most common in LC-MS. The similar tendency was also found in many other columns.
We carried out a comprehensive study to understand the phenomenon of tR variation, including effects of metal impurities, reagent grade of mobile phase solvents, and byproducts in the process of stationary phase synthesis. After eliminating one possible cause after another, we reached a conclusion that the responsible factor was either 1) the synthetic byproducts and the residues of impurities from reagents used for the synthetic process, or 2) isolated silanol groups on the stationary phase surface1.
For the former, a special method to clean and condition columns (pre-conditioning, PC) was invented. The PC process was intensively studied, and one of the results was shown in Fig.2, where the relation of the duration time of PC and tR of amitriptyline was clearly observed. The retention time of naphthalene, a conventional indicator for overall retention of C18 columns, did not change at all, while tR of amitriptyline gradually increased with the PC time, and reached the plateau after a certain time.
Solid-state 29Si-NMR, a useful tool to directly observe different silanol groups on the surface, did not show a significant difference between before and after the PC process (Fig.3), which suggested the residues of unwanted substances were the most responsible to the tR variation of amitriptyline. Based on these results, we confidently applied the PC process to all of the MG columns, and decided to launch the columns as "MGIII" series. The followings are some of characteristic applications obtained with the MGIII series.
Therefore, the special PC process provided the stable retention to both of basic amitriptyline and neutral naphthalene.
Ref. 1) J.J.Kirkland coworkers., J.Chromatogr., 352 (1986) 275.
· Excellent reproducibility Fig. 4Fig. 5
· Comparison of column bleeding Fig. 6Fig. 7
· Separation of organic acids Fig. 8
· Also available worldwidely
· GLP/GMP-Supporting column
· Categorized as L1 in USP
Property values
Pore size
(nm)
Particle size
(μm)
Specific Surface area
(m2/g)
C% Density
(μmol/m2)
Functional group Acceptable pH USP
10 3 300 15 2.3 Octadecyl group 2-10 L1
10 5 260 15 2.7 Octadecyl group 2-10 L1
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