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Abstract
Using high purity Type B silica, Tosoh has introduced two new columns
with differing surface treatment procedures and carbon content levels
to provide unique selectivities for a wide range of sample types.
Introduction
In recent years, many new octadecylsilane (ODS) chemistries have been
made commercially available that offer optimized properties for select
subsets of compound types. The overriding trends in the release of new
stationary phases has shifted toward 1) high purity, metal free silica
2) base-deactivated surfaces 3) stronger retention of polar compounds
and 4) improved reproducibilities from column to column and silica lot
to silica lot. Rarely, have new ODS column types provided a universal
solution to the multitude of applications being performed. Further, column
selection to match the best column with the application has been difficult.
With the introduction of TSKgel ODS-100V and TSKgel ODS-100Z, excellent chromatography and selectivity can be achieved with a wide range of sample types. Due to the fact that both stationary phases use the same ultra-pure base silica with 5m particle size and 100 pores, the same chromatographic properties are achievable for columns of different lots. Different selectivities result by varying the carbon content and surface optimization. Table 1 summarizes these differences.
TSKgel ODS-100V columns are optimized for polar compounds while the TSKgel ODS-100Z are the better choice for more hydrophobic compounds. Both column types provide symmetrical peak shapes for strongly basic and acidic compounds, demonstrating the absence of accessible residual silanol groups and metal-ion impurities on the silica surface, respectively.
Results
Basic and Acidic Compounds:
The tricyclic antidepressant desipramine, containing a secondary amine
group, was analyzed at pH 7.0 to illustrate column performance under conditions
where accessible residual silanol groups would be negatively charged.
It is apparent from Figure 1 that tailing is minimized on new
TSK-GEL ODS columns relative to other commercially available C18 column
brands. Similarly, at pH 2.2, formic acid used as the test probe to judge
the chromatographic behavior of charged acidic compounds, reveals good
peak shape as indicated in Figure 2 .
Hydrophobic and Polar Compounds:
The hydrophobicity and surface polarity of both stationary phases are
represented in Figure 3 . The TSKgel ODS-100V has more polar properties
than most recently released AQ-type phases. Retention of hydrophobic test
probes differing in one or more methylene groups, indicated that TSKgel
ODS-100Z has more hydrophobic character than TSKgel ODS-100V and is comparable
to the majority of commercially available phases. Thus, scientists can
use standard mobile phases when testing the performance of the new TSK-GEL
ODS columns in comparison to brands they currently use.
Reproducibility:
Lot-to-lot reproducibility of the TSKgel ODS-100Z is shown in Figure
4 . A total of six different stationary phases lots were examined.
The six lots included 3 different base silica lots, thus representing
columns from different silica and bonding lots, a
nd columns that differ
only in the bonding lot. Consistent chromatographic results were obtained
regardless of base silica or bonding lot.
Conclusions:
The recently commercialized TSKgel ODS-100V and TSKgel ODS-100Z column
set provides a universal solution for most reverse phase separations.
More Infomation
TSKgel
ODS-100V
TSKgel
ODS-100Z
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Source:
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