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2004 vol. 3

Pinnacle

™

DB Base-Deactivated HPLC

Columns

Effective Replacements for Hypersil

BDS Columns

by Rebecca Wittrig, Ph.D., HPLC Product Marketing Manager,

and Vernon Bartlett, HPLC Innovations Team Manager

•Sharp, symmetric peaks for basic analytes.

• Excellent reproducibility, column-to-column and lot-to-lot.

•Chromatography equivalent to Hypersil

BDS material.

With Pinnacle

™

DB base-deactivated silica, we

have created an exceptional material for analy-

ses of basic compounds, matching or exceeding

the chromatographic performance of Hypersil

BDS material. Pinnacle

™

DB silica and bonded

phase packings are made through efficient

processes that ensure reproducible perform-

ance and reliable stock levels—we ship 90% of

all analytical columns ordered within 24 hours.

In Figure 1, peak symmetry for the basic com-

pound pyridine is noticeably better on the

Pinnacle

™

DB C18 column than on a typical Type

B C18 column, and the analysis time is shorter

by more than 30%. You can expect similar

results if you make your own comparisons.

Figure 2 shows how closely matched the impor-

tant physical characteristics of particle size and

pore size distribution are for Pinnacle

™

DB and

Hypersil

BDS materials. Physical/chemical

characteristics of Pinnacle

™

DB packings are

listed in Table I.

For certain physical parameters - most notably,

metals content - we intentionally deviate from

Hypersil

BDS material, as Figure 3 shows. The

major difference in sodium content is especially

important, as metal ions on the surface of silica

particles negatively affect peak symmetry and

otherwise interfere with chromatography, partic-

ularly for basic analytes. But, there is another

important problem with silicas that have a high

metal content, especially sodium—they are

structurally inferior to silicas containing lesser

amounts of metals. To strengthen silica particles

containing high concentrations of sodium, some

manufacturers use an annealing process to

embed the sodium into the framework of the

particles. Although annealing imparts strength to

the particles, it destroys some of their useable

surface area. And, as the particles age or crack,

embedded ions are re-exposed. Deactivation for

bases is lost, and stability in highly aqueous

mobile phases erodes.

Our manufacturing process strips metals and

other impurities from the silica surface. By

removing metals, rather than covering them, we

make a more rugged silica that does not need

annealing to impart strength. Peak shapes for

bases are more consistent as the column ages,

and the potential lifetime for a Pinnacle

™

DB col-

umn is longer. Also, large pores (140Å) make

Pinnacle

™

DB material an excellent choice when

you want to shorten analysis time.

But - how do separations on Pinnacle

™

columns and Hypersil

BDS columns compare?

The chromatograms in Figures 4 and 5 are

analyses of a base/neutral test mix and an

acid/base test mix, respectively. Behavior of

each of these analytes will vary, based on differ-

ences in carbon load, ligand density, degree of

base deactivation, endcapping, and exposed

metals. Columns that are similar for these char-

acteristics should provide similar chromatogra-

phy, and Figures 4 and 5 show Pinnacle

™

DB C18

columns and Hypersil

BDS columns perform

nearly identically.

If you are looking for rugged, high-quality

columns for analyzing basic compounds, or as

replacements for Hypersil

BDS columns, and

you want them supplied quickly and reliably,

Pinnacle

™

DB columns are the ideal answer. In

addition to the product quality you expect, you'll

receive Plus 1

™

service and prompt, expert tech-

nical help when you deal with Restek.

Figure 1

Superior peak symmetry for pyridine, and a

faster analysis, on a Pinnacle™ DB column.

LC_0245

Sample:

Inj.:

5.0µL

Solvent:

mobile phase

Conditions:

Mobile phase: 20mM potassium phosphate, pH 7.0: acetonitrile

(80:20 v/v)

Flow:

1.0mL/min.

Temp.:

ambient

Det.:

UV @ 254nm

LC_0248

Peak List:

Conc.

1. uracil

5.0µg/mL

2. pyridine

0.1µL/mL

3. phenol

1.86mg/mL

Column:

Pinnacle

™

DB C18

Conventional C18

Cat. #:

9414565

n/a

Dimensions:

150 x 4.6mm

Particle size:

5µm

Pore size:

140Å

100Å

Figure 2

Physical characteristics of Pinnacle™ DB silica and Hypersil® BDS silica are remarkably similar.

Table I

Physical/chemical characteristics of Pinnacle™

DB packings.

Particle:

5µm, spherical

Pore size:

140Å

Pore volume:

0.65mL/g

Carbon load:

C18—11%

C8—6%

Cyano—4%

Particle Size analysis

Pinnacle DB Hypersil BDS

Geometric Mean (µm):

4.81±1.20

4.89±1.70

Arithmetic Mean (µm):

4.89±0.94

4.95±0.82

Median (µm):

4.69

4.81

Mode:

4.69

4.79

Max Diff. (%):

6.04

7.11

Pinnacle DB

Hypersil BDS

Particle Size Distribution

Pore Size Distribution