ADV06-15_1-412

332 / 413

2007.01
General Information
Using Micropacked Columns
By Alan Sensue, Technical Service Specialist
Most analysts are familiar with capillary gas chromatography columns and packed GC columns, but
many are not familiar with micropacked columns. Here, we briefly discuss these useful columns, instru-
ment requirements, and applications.
What Are Micropacked Columns?
Micropacked columns are short, narrow bore stainless steel columns packed with diatomaceous earth solid
support, porous polymer, molecular sieve, or other particles. Standard Restek micropacked columns are 1
meter or 2 meters long and 0.75mm ID x 0.95mmOD or 1mm ID x 1/16 inch OD. Like most micropacked
columns, ours have a larger internal diameter than mega-bore (wide-bore) capillary columns (0.53mm ID)
and a smaller outside diameter than traditional packed columns (1/8 inch or 3/16 inch).
As you might suspect from this description, performance characteristics of micropacked columns are
intermediate between those of packed columns and those of capillary columns: they offer higher effi-
ciency than traditional packed columns, and higher capacity than wall coated open tubular (WCOT) cap-
illary columns or porous layer open tubular (PLOT) columns. They are inexpensive, very durable, and
easy to install and operate.
Instrument Requirements
To use micropacked columns, a high carrier gas head pressure is needed to overcome the large pressure
drop created in the narrow, densely packed bore. For helium, typical column head pressures for 1-2 meter
micropacked columns range from 30-45psi for 1mm ID columns to 50-65psi for 0.75mm ID columns.
Installation of micropacked columns will vary according to instrument make and model. The injection
port nuts in many capillary column injection ports will accommodate 0.95mm OD micropacked
columns, but not 1/16 inch OD columns. If the injection port nut will not accommodate the column, you
can attach a short piece of 0.53mm ID fused silica tubing to each end of the column, using 1/16 inch com-
pression fitting unions and appropriate ferrules. Alternatively, Restek sells inlet conversion kits which
contain appropriate selections of injection port accessories.
For GCs with packed column injection ports, a reducing ferrule or a tube-end reducer fitting, and appro-
priate ferrules, usually are all that are needed for installing a micropacked column.
Applications
Micropacked columns have a wide range of applications, from analyses of the lightest gases (permanent
gases) to simulated column distillation (Sim-Dist). They are especially useful for analyses of gas mixes,
including sulfur compounds or light hydrocarbons, in which the use of a packed column is necessary to
obtain baseline separations of the gaseous components.
Typically, chromatogram peaks are sharper than from traditional packed columns, and micropacked
columns are less likely to be overloaded by concentrated samples than are capillary columns. Micropacked
columns do have limitations, however: like packed columns, they do not have the efficiency of capillary
columns. Therefore, they typically are not adequate for baseline separations of complex multi-compo-
nent mixtures. Also like packed columns, they require a carrier gas flow rate that is higher than most mass
spectrometer pumping systems can accept.
When choosing a micropacked column, consider that, as with any column, internal diameter affects col-
umn capacity. If you intend to use a sensitive detector, such as a helium ionization detector (HID), flame
ionization detector (FID), nitrogen-phosphorus detector (NPD), or flame photometric detector (FPD),
typically you can use a smaller ID column – either a conventional capillary column or a
micropacked column. If you intend to use a thermal conductivity detector (TCD), however,
consider using a 1/8 inch OD packed column, rather than either a capillary column or a
micropacked column.
For a complete listing of micropacked columns and installation kits offered by
Restek, please visit our website, and enter “micropacked
columns” in the search feature. For typical applications, see web page:
You also will find these items in the Restek Chromatography Products Catalog. For
additional information concerning micropacked columns, please contact Restek
Technical Service at 800-356-1688, ext 4.
Custom
Micropacked
Columns
To Order:
Contact your Restek represen-
tative and specify the following:
1) dimensions (length, OD, ID,
and tubing material)
2) packing description (percent
coating and phase, support
mesh size, and treatment)
3) installation kit
Ordering Example:
(2m x 1/16 " OD x 1.00mm ID)
(Silcosteel® tubing) (5%)
(Carbowax® 20M)
(CarboBlack™ B) (80/120)
(installation kit for valve
applications, cat. #21065)
To Obtain a Quote:
See our catalog or website, or
contact technical service at
800-356-1688, ext. 4.
Maximum length for custom
micropacked columns is
25ft./8m.