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General Information
Commonly Asked GC Questions
Answered bytheRestek Chromatography InformationServices Group
How do I know which guard column would be best for my application?
Restek offers guard columns and transfer lines ranging from 0.025mm ID to 0.53mm 10 , from 1 to 10 meters long, in fused silica or
Silcosteel'" treated stainless steel. Guard columns are available with nonpolar, intermediate polarity, or polar deactivation, and with
several specialty deactivations.
• In most applications in which nonpolar to moderately polar solvents are used; we reco mmend an intermediate-polarity
OP) deactivated guard column.
• For most polar solvents excep t water, we generally suggest a polar deactivated guard column.
• For water -based samples, we recommend our water-resistant Hydroguard" guard columns. Th is deactivation is
designed to withstand th e harsh "steam -clea ning" th at occurs when water is rapidly vaporized in the column.
• For applications that req uire a hig hly inert surface to minimize analyte breakdown, such as pesticides analysis, we rec­
ommend a Siltekw deactivated guard column.
• For amines or ot her basic compounds, we offer base-deactivated guard columns.
Also, note that for many of our popular statio nary phases, we offer Integra-Guard" columns - an analytical column with an inte­
gral guard colum n. This eliminates the connection between the guard column and the analytical column. Much information about
guard columns is presented in our free publication #59319.
What are all those different capillary column temperatures listed in your catalog?
The first temperature listed is the minimum operating tempe rat ure for the column. The two temperatures separated by a slash sym­
bol ( / ) are the maximum isothermal operating temperature and the maximum temperature program temperature, respectively. The
maximum temperature program temperature is the maximum temp erature to which the column may be exposed briefly without
causing damage. For most stationary phases, the maximum temperature program temperature is approximately 20°C above the max­
imum isothermal temperature. In addition to these temperatures, the polymer stability temperature sometimes is listed. This is the
maximum temperature to which the polymer phase can be exposed before degradation.
I see ghost peaks when I inject a sample or standard, and my mass spectrometer
identifies these peaks as a siloxane material. Is there a problem with my column?
Capillary columns can prod uce a varying amo unt of baseline noise (siloxane bleed), usually contai ning fragment ions at mlz 73, 207,
and 281, but they will not prod uce any distinct peaks in an analytical run. The most common sources of distinct siloxane peaks are
septum bleed and the chemicals used to deactivate the injection port liner and the glass wool packing material.
Sometimes I experience problems when using a 1701 -type column for my pesticides analysis. Are there other column choices?
On-column breakdown of chlorina ted pesticides, such as endrin, methoxychlor, and DDT, are common with cyano-contain ing
phases, such as l701- type phases. Fortunately, there are other column choices. These include a few standard phases, such as our
Rtx®-35, Rtx®-35MS, and Rtx®-50 phases. In addition, Restek has developed several specialized columns for pesticides, including
Rtx®-CLPesticides & Rtx®-CLPesticides2, and Stx®-CLPesticides & Stx®-CLPesticides2 columns. These columns eliminate on-col ­
umn breakdown prob lems, imp rove separation, and reduce analysis time . Information about these columns, and example chro­
matography, can be found on our website:
Can I order a fused silica column in a
column cage to fit my small GCoven?
Yes. We offer several special cage options for
non-standa rd and portable GC ovens. Please
contact our informations services group at
800-356-1688, ext. 4, for specifics, or
customer service (ext. 3) for prices Please
note that we canno t cage or recage columns
from other manufacturers .
the Restek Chromatography Information Services Group
2006.03 800-356-1688· • 30 •
Website : E-mail : TelNo : 03 9762 2034 . . . in AUSTRALIA