[Chromatography Q & A]: Connection Types of HPLC Column Wakopak®
This article was written for No. 71 (December 2013), of Analytical Circle
In the past, manufacturers of HPLC systems applied different specifications to connectors. In HPLC systems using stainless-steel pipes and connectors, the first column determined specifications of these parts (D; Dupont or W; Waters type), and a next column had to be chosen from those that had the same connection type as that of the previous column.
At present, however, connection types have been standardized, and most manufacturers have adopted inch screw thread, standardized ferrules, and resin Handy Connectors for columns. In HPLC systems using resin Handy Connectors, any column of either type D or W is available.
In HPLC system using stainless-steel ferrules, but not resin connection parts, however, the length (h) of pipe inserted into a column at the connection site is fixed, and thus the column with a connection type that suits the length (h) has to be chosen, because of pressure resistance at connection site.
If connection type of the column in use is unknown, the length (h) should be measured to find a suitable column type. (D type, h = 2.3−2.9 mm; W type, h = 3.5 mm)
To obtain analysis results by exploiting full performance of the column, the connection type must be matched.
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• Size of connection site
Shape P, h (mm) Specification Connection type h (mm) 
Inch screw thread
No. 10-32 UNF
P: 4.8 mm
Ferrule type
W 3.5 D 2.3-2.9 * Length (h) are expressed as measured values, which are for reference.
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• Screw and column connection site
Examples of column connection
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Good example
(1) h = a
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Bad example
(2) h > a
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Bad example
(3) h < a
