Often our customers ask us: “How do I make my connections work in my nanoLC-MS set-up” or a variant of this phrase. On this page we will provide our insight into this misty territory, with many options and pitfalls.
The first question for you to answer is: “What do I want to connect and with what purpose”. Is it “just” a coupling between a transfer line and a column or emitter, or do you want to turn the connection into a Liquid Junction at the same time. In latter case, you may wish to look into some electrical safety features at the same time.
Frequently made connections
Some connections are made more than others, most connections are straight through and some make use of a t-piece or cross. T’s and Crosses are used to make Liquid Junctions , using gold or platinum electrodes/wires, but T’s may also be used to facilitate vented trap-LC set-up’s. At the end of the day the fittings used are of limited specification, but whatever you combine, things do have to fit!
Here are some examples you may find being used:
Frequently used and Novel connectors
Over the years a lot has stayed the same in nanoLC-land, mainly due to the resistance to change in the realms of the larger vendors. Connections offered today have been stable over a 10 year plus period. Even though they say “never to change a winning team”, developments do not stop and often may improve the finicky way nanoLC connections are made. In making tight connections it’s all about dimensions.
Let’s start with some well used Outer Diameter (OD) dimensions:
Fused Silica tubing:
1/16″ of 1/32″
360-365µm (widely used) or 280µm (UltiMate™ 3000 RSLCnano System)
150µm or 360µm
2) Nuts and bolds
Secondly there are a number of different connectors that ensure a zero dead volume connection. Some examples are:
|Viper™ Fingertight Fittings||1/16” 10-32||Pre-connected to tubing/column|
|NanoConnect Fingertight Fittings||1/16” 10-32||Pre-connected to tubing/column|
|VICI 360 Nuts for 360µm FS tubing||Proprietary||Self-Assembly|
|IDEX MicroTight for 360µm FS tubing||Proprietary||Self-Assembly|
|VALCO Steel Nut and Ferrule||1/16” – 1/32”||Self or Pre-assembled|
|Zircofit||1/16” 10-32||Make your own fixed connection|
nanoViper™ Fingertight; Thermo Scientific™
Valco 1/16” Stainless Steel Nut& Ferrule
Valco 1/32” Stainless Steel Nut& Ferrule
ZircoFit™ UHPLC Fittings; Prolab
IDEX MicroTight® Fitting
NanoConnect Fitting – PEEK
VICI 360µm FS Connector – PEEK
VICI 360µm FS Connector – STEEL
NanoConnect Fitting – PEEK
As you can see there is a wide range of products available to make connections work, however some work better that others. 10 years ago one had no choice but to use sleeves, today there are a number of options that will allow for easy leak tight connections on 360µm OD Fused Silica lines.
The unions and crosses themselves also come in different variants:
|ZDV Union||VICI||C360UFS2||Steel||360µm FS lines direct with 360 nut|
|IDEX||P771||Polymer||360µm FS lines with sleeve 1/32″ nut|
|Tee||VICI||C360TS62||Steel||360µm connections; 50µm bore|
|IDEX||MicroTee P-88||Peek||360µm connections; 150µm bore|
|IDEX||VHP MicroTee UH-750||Steel||360µm connections; 250µm bore|
|Cross||VICI||C360XS62||Steel||360µm connections; 50µm bore|
|IDEX||MicroCross||Peek||360µm connections; 150µm bore|
|IDEX||VHP MicroCross||Steel||360µm connections; 250µm bore|
IDEX VHP MicroTee
IDEX MicroCross PEEK
IDEX VHP MicroCross STEEL
Unions are made to ensure a “Zero Dead Volume” connection. One note here, to clarify, “zero dead volume” does not mean that there is no volume between the two ends you are connecting. It means that there is no void volume between the ends, many ZDV-connectors have a bore in the metal divider between the lines, if the hole in the divider is similar to the inner diameter of the tubing you are connecting, then the volume in the divider is not considered “dead volume”.
The rational is that as the inner diameter of the continuous line (tube 1 – union – tube 2) is not expanded, and therefore doesn’t affect the flow, the hole is counted as part of the flow line. Dead volume, that causes your chromatography peaks to broaden, is a larger volume in which the laminar flow is disturbed. An extreme example of this is the UV-detector cells that used to be placed in-line with a Mass Spectrometer. Having said that also poorly made fittings cause dead volume and they are the main cause for dead volume in a nanoLC system, so be careful when making your own.
For more information on VICI, click here.