Author:
Michael McGinley, Lawrence Loo,
Jeff Layne, et al.
Phenomenex, Inc., 411 Madrid Avenue, Torrance, CA 90501 USA
With the introduction of two new bonded phases, further research and product development of Kinetex core-shell fillers reached a culmination: Kinetex XB-C18 and Kinetex C8. These two new stationary phases provide complementary selectivity for the existing Kinetex phases (Kinetex XB-C18 and Kinetex C8), and provide additional solutions for ultra-efficient separations by chromatographers. Especially useful.
Introduction
The geometric design of the Kinetex core-shell particles allows it to provide ultra-high performance, approaching and in some cases exceeding 300K plates per meter, but it can be run on a standard HPLC system with a 400 bar back pressure limit. The key to using this product is to introduce three different bonding phases to provide options for method developers. C18 and PFP provide complementary reversed-phase selectivity: C18 separation is mainly based on the difference in analyte hydrophobicity; while PFP is based on aromaticity, hydrophobicity, and polar selectivity. The silica gel HILIC phase provides orthogonal separation modes based on the difference in analyte polarity. Although these stationary phases provide solutions for most method development, we have also developed other complementary stationary phases to meet the needs of chromatographers. XB-C18, bonded with cross-butyl, provides different retention characteristics, especially the retention of alkali at low pH. C8 provides lower hydrophobicity than Kinetex C18, reducing secondary interactions (due to higher bonding density), thereby improving peak shape, especially for those with severe tailing analytes such as metabolites of basic drugs Say. This technical note will perform some general studies on the selectivity of new Kinetex stationary phases and how they complement the selectivity of Kinetex products.
Materials and Methods
Except for the USP test standard purchased from USP (Rockville, MD), all chemicals were purchased from Sigma Chemical (St. Louis, MO). The solvent was purchased from EMD (San Diego, CA). The Kinetex different stationary phases (C18, XB-C18, C8, PFP and HILIC) have a column size of 50 x 2.1 mm or 100 x 4.6 mm (Phenomenex, Torrance, CA). All analyses were run on an Agilent 1100 or 1200 HPLC system (Palo Alto, CA), equipped with an autosampler, column oven, and multi-wavelength detector. Specific methods are listed in each application.
Results and discussion
Kinetex XB-C18 is better than Kinetex C18
Kinetex XB-C18 is a cross-butyl C18 bond instead of the traditional C18 bond, so it provides a unique selectivity over the Kinetex C18 phase. Although the hydrophobicity of XB-C18 is only slightly stronger than that of Kinetex C18, the selectivity for acidic and basic compounds is significantly different, especially under non-ionic to acidic mobile phase conditions, such as 0.1% formic acid. Kinetex XB-C18's retention of basic compounds is reduced, while the retention of acidic compounds is slightly increased.
Figure 1 depicts the different selectivity for mixtures of acids, bases and neutral compounds under gradient conditions. When Kinetex C18 (Figure 1A) was compared with Kinetex XB-C18 (Figure 1B), it was observed that the elution order of these mixtures changed significantly. On XB-C18, basic compounds are clearly eluted earlier, while acidic compounds are slightly later. It can be considered that this is because of the difference in interaction between the sterically hindered cross-butyl C18 and the traditionally bonded C18 and silanol groups. Kinetex C18 increases the retention based on silanol groups, indicating that this relatively basic compound has higher selectivity, especially when using TFA buffer. For those applications that use formic acid (such as LC / MS conditions), Kinetex XB-C18 will be the first choice to improve peak shape and reduce the retention of basic compounds. However, these rules are not so simple. Analyze the steroid mixture as shown in Figures 2A and 2B. There are no basic compounds in this example, but their elution order on Kinetex C18 and Kinetex XB-C18 columns is not the same. The possible explanation is that the elution order of 21-cortisone acetate on the two stationary phases is different because it belongs to esters, and the different elution order of 21-hydroxyprogesterone and estrone indicates that another mechanism affects these Selectivity differences between these stationary phases. Finally, both stationary phases have unique and complementary selectivity, which is very useful for method development column screening.
Kinetex C8
Although most people think that the C8 phase is slightly less hydrophobic than the C18 phase, this is not the case in the study of the selectivity difference between Kinetex C18 and Kinetex C8. The Kinetex C8 phase provides users with the opportunity to enhance the USP method, using core-shell packing to replace the fully porous C8 column for high throughput and high performance. In addition, from the graph of Kinetex C8 analysis of certain drug mixtures (Figure 3), it can be seen that the selectivity of this stationary phase is not only a decrease in hydrophobicity compared to Kinetex C18. Relative to neutral and acid analytes, the retention of basic components has changed, but it is not obvious when comparing XB-C18 and C18. This change makes Kinetex C8 "selective" compared to other phases. This unique selectivity makes Kinetex C8 another option for method development column screening, especially for chromatographers who want to update existing USP methods using L7. When looking for a "real" method, the C8 phase can be a very good choice. The veterinary drugs in horse urine were analyzed as shown in FIGS. 4A and 4B. In these applications, Kinetex C18 and XB-C18 were also used. In the figure (Figure 4A), certain contaminants in horse urine eluted together with the analyte, and the peaks overlapped. However, when using Kinetex C8, all analytes can be separated from matrix contaminants. Such results further indicate that Kinetex C8 phase as a unique selectivity should be considered for use in method development.
Full text reading
Mini Car Vacuum Cleaner,Cordless Car Vacuum Cleaner,Car Cordless Vacuum Cleaner,Rechargeable Car Vacuum Cleaner
Ningbo ATAP Electric Appliance Co.,Ltd , https://www.atap-airfryer.com