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Switching from Coated to non-Coated Pulled Emitters

Switching from Coated to non-Coated Pulled Emitters
Coated to non-coated emitters

Many Thermo Scientific customers have been trained to use the magnetic coupler on the end of the DirectJunction™ column rail (nanoSpray Flex™ ion source) to connect a fused silica emitter with a coated tip, in order to apply voltage to enable electrospray. Others use distal-coated tips in which the coating is used to apply voltage at the entry of the emitter.

With a global shortage in the supply of coated emitters, our customers have no choice than to change their emitter set-up slightly. We have found that there are basically three ways forward (which we will elaborate on in this blogpost):

  1. Use metal emitters
  2. Implement non-coated emitters supported by a Liquid Junction
  3. Switch to a novel Adapter, that integrates emitter and liquid junction.

1. Use Metal Emitters

To start with the most obvious one, coated emitters can just change to metal emitters. The DirectJunction was originally designed for use with metal emitters and therefore these emitters are an easy one-to-one replacement. Metal emitters can also replace the distal-coated versions.

Mounted in a suitable sleeve the emitter can be fitted into the IDEX P771 union on the source. Metal emitters are available in various lengths, but only one internal diameter of 30µm.

Figure 1. Example set-up with Metal Emitter.

2. Implement non-coated emitters (supported by a Liquid Junction)

If you wish to stay with very similar emitter dimensions, like a OD: 360µm; ID: 20µm; Tip 10µm, then an alternative way to apply voltage to the liquid in the tubing is needed. The way to organize this is by using a liquid junction on a suitable location.

Liquid Junctions are often metal ZDV unions to which a voltage is applied and depending on your set-up, they are placed:

  • either before the column or
  • between a transfer line and the emitter.
Figure 2. Example set-up with implementation of non-coated emitter supported by a Liquid Junction.

In this first case, your column is often mounted on the ion source, avoiding any post column dead volume. In the latter case, the column is mounted in the column oven of your LC system, hence the use of a transfer line.

3. Switch to a novel Adapter (that integrates emitter and liquid junction)

When you have chosen to use the column oven supplied in your LC system, then you likely use a 20µm ID transfer line mounted with a Viper™ (or compatible) connector. In this case using a novel spray Adapter that replaces the DirectJunction on the ion source is a great upgrade to your system.

This novel Adapter will allow you to just connect a Viper connector to the adapter. Inside the adapter you will use an emitter which is fitted with a Liquid Junction. This way all connections are made by simply fitting the Viper connector to the adapter or use a ready made transfer line with a NanoConnect fitting, which is the fitting the Adapter was designed for.

PSS1: Spray Adapter for Nanospray Flex™ Ion Source (drawing)
PSS1: Sprayer for Nanospray Flex™ Ion Source
Fused Silica Emitter with Liquid Junction (PSFSELJ10)
Figure 3. Novel Spray Adapter design (PSS1).

In case you have mounted your column on the ion source (which is the preferred location to avoid post column dead volume) the switch between coated and non-coated emitters involves adding a liquid junction. In the past a liquid junction was often a cross or T-connector with a fairly large internal volume, in which a platinum wire was mounted. These days a new VICI union with a bore of 50µm is a better choice, especially because the union uses fittings that make a sleeveless connection for 360µm OD tubing. The power is applied directly on the stainless steel union.

In order to safely make use of this union a mounting kit is available for mounting the union on the DirectJunction. The mounting kit is based on an isolating mount that slides onto the column rail on one side and holds the union in place on the other side. A magnetic coupler is used to connect the power to the union. The HV cable attached to the coupler is fitted with a LEMO-plug to be able to connect to the nanoSpray Flex ion source and take the power from this outlet.

A set-up with a column mounted on the ion source, using separate emitters, will need two unions to make the set-up function. The most logical place to add the union is prior to the column, however with this very narrow bore connection emitter post column is also an option.

When placing the union before the column a reducing union from 1/16” to 360µm is preferred.

VICI Union 360µm
Reducing Union 1/16″-360µm
Liquid Junction Mount
HV Connections Cable

Product Numbers & Specifications:

SupplierProduct Nr.Specifications
Bruker1893527Fused Silica PepSep Emitter with Integrated Liquid Junction: 10µm ID, 150µm OD, 2,6cm Length.
1893528Fused Silica PepSep Emitter with Integrated Liquid Junction: 20µm ID, 150µm OD, 2,6cm Length.
1893525Stainless Steel PepSep Emitter with Integrated Liquid Junction: 30µm ID, 150µm OD, 2,6cm Length.
1893489Transfer Line with fittings: 10cm, 20µm Fused Silica with nanoConnect coupling
1893515Transfer Line with fittings: 20cm, 20µm Fused Silica with nanoConnect coupling
CoAnn TechnologiesTIP36002010-7-5Pulled ESI Fused Silica Emitter: 20µm ID, 365µm OD, 7cm Length, 10µm Orifice ID.
Phoenix S&TPST-HV-NFULiquid Junction for Nanoflex Source. Includes: lowest dead volume liquid junction, HV cable with magnetic coupler, insulation block, no-sleeve PEEK nut/ferrules, and the tightening tool.
MS WilPSS1nESI Sprayer used to connect any nanoConnect column to the emitter with the integrated liquid junction in a zero dead volume connection. Designed for Thermo Flex nano Source.
MSWHVCABLEHigh-voltage cable for connection of liquid junctions and PSS1.
* These emitters come with a 1/32″ PEEK sleeve for easy connection to any 1/32″ Union.

Left with any further questions or comments? Please don’t hesitate to contact us by mail (sales@mswil.com).

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