WPI’s microelectrode holder-half-cells couple fluid-filled glass micropipettes to high input impedance amplifiers. A Ag/AgCl pellet (or a silver wire) molded into the holder body provides stable potential. Electrical connection is made via male 2mm pins or female 2mm sockets. The pipette may be mounted axially or at right angles to the holder. Pipettes are held with screw-caps or rubber gaskets (without caps). Filling WPI microelectrode holders with electrolytes containing chloride results in stable electrode potential. Suitable electrolytes include KCl, NaCl and CaCl2. Holders are supplied for standard WPI single capillary tubing of 1.0, 1.2, 1.5 and 2.0mm outside diameters. (Call WPI regarding custom designs for other glass diameters.) The holder style you select will depend on your experimental application, space, and instrumentation.

Hints for selecting and ordering micropipette holders

1. Determine the required electrical connection on the holder. For example, if you wish to connect the holder to a 2mm pin, you should select a holder equipped with a 2mm jack. Most WPI probes require a holder equipped with a 2mm jack.
2. Decide on the required alignment of the electrical connection (in-line with the glass pipette or at a right angle to it). Space considerations in your experimental setup and requirements imposed by other pieces of equipment typically determine which alignment is appropriate.
3. Determine if you want to hold the glass pipette with a rubber gasket (MEH1S) or a screw-cap (MEH3S). Rubber gaskets offer easier insertion and removal of glass pipettes whereas screw-caps provide more secure mounts for micropipetters.
4. Choose a holder with either a silver wire or a silver/silver chloride pellet for the metal/liquid coupling. Silver/silver chloride pellets provide a more stable, low-noise baseline which is important for low-noise DC recording. Pellets require the glass pipette and holder to be free of air bubbles to achieve a good connection. Silver wire holders are durable and are easier to use when the holder is equipped with a pressure port because the fluid in the pipette does not have to be filled to the top of the pipette to achieve a good electrical connection.
5. Choose a holder equipped with a pressure port only when you want to pressure inject liquid from the pipette. Two types of ports are available: 2.0mm O.D. and standard “syringe-style” luer. The luer port is often recommended because it makes assembly and disassembly much easier. Quick-connect luer fittings for four common sizes of tubing (1/16", 3/32", 1/8", 5/32" I.D.) are included with each luer-equipped holder.
6. Some non-WPI preamplifiers or headstages cannot be mounted on micromanipulators. In such cases, a holder equipped with a rod (MEH8) permits the holder to be conveniently mounted on a micromanipulator.
7. Finally, remember to specify the O.D. of the glass you will be using when you place your order.

• MEH6RF/SF is designed primarily for use with the Model 900A Micropressure System.
• EHB1 is for use in electrode beveling.
• MEH3SW is for microtitration of chloride with a silver wire as the electrode and a solution of silver nitrate filling the holder.
• MPH models do not contain Ag/AgCl half-cells and are used for pressure injection of substances through microelectrodes.
• PicoNozzle, used for pressure injection with PV800 Series PicoPumps, includes an MPH6S holder — which may also be used to couple a micropipette to a syringe.
• APEH models are also designed for use in pressurized injection procedures.

	Electric Connection Angle	Connector	Half-Cell	Pressure Port	Screw Cap	Designed for WPI Products
APEH1	Right	Male	Pellet	No Port	2 Caps
APEH2	Right	Male	Wire	No Port	2 Caps
EHB1	Straight	Male	Wire	No Port	N/A	MBS, 48000
EHBF	Straight	Female	Wire	No Port	N/A	MBS, 48000
FOIMPH	Straight	Fiber Optic	None	No Port	w/Cap	MBS, 48000
FOIMPH-LF	Straight	Fiber Optic	None	Male Luer	w/Cap	MBS, 48000
MBMPH5-7	----	None	None	Female Luer	w/Cap
MEH145	45°	Male	Pellet	No Port	No Cap
MEH1F45	45°	Female	Pellet	No Port	No Cap	705, 773, 767, 721, FD223
MEH1R	Right	Male	Pellet	No Port	No Cap
MEH1RF	Right	Female	Pellet	No Port	No Cap	705, 773, 767, 721, FD223
MEH1S	Straight	Male	Pellet	No Port	No Cap
MEH1SF	Straight	Female	Pellet	No Port	No Cap	705, 773, 767, 721, FD223
MEH2R	Right	Male	Pellet	Male Luer	w/Cap
MEH2RF	Right	Female	Pellet	Male Luer	w/Cap	705, 773, 767, 721, FD223
MEH2RFW	Right	Female	Wire	Male Luer	w/Cap	705, 773, 767, 721, FD223
MEH2RW	Right	Male	Wire	Male Luer	w/Cap
MEH2S	Straight	Male	Pellet	Male Luer	w/Cap
MEH2SF	Straight	Female	Pellet	Male Luer	w/Cap	705, 773, 767, 721, FD223
MEH2SFW	Straight	Female	Wire	Male Luer	w/Cap	705, 773, 767, 721, FD223
MEH2SW	Straight	Male	Wire	Male Luer	w/Cap
MEH345	45°	Male	Pellet	No Port	w/Cap
MEH3F45	45°	Female	Pellet	No Port	w/Cap	705, 773, 767, 721, FD223
MEH3FW45	45°	Female	Wire	Port	w/Cap
MEH3R	Right	Male	Pellet	No Port	w/Cap
MEH3RF	Right	Female	Pellet	No Port	w/Cap	705, 773, 767, 721, FD223
MEH3RFW	Right	Female	Wire	No Port	w/Cap	705, 773, 767, 721, FD223
MEH3RW	Right	Male	Wire	No Port	w/Cap
MEH3S	Straight	Male	Pellet	No Port	w/Cap
MEH3SB	Straight	Banana	Pellet	No Port	w/Cap	ISO-80, ISO-DAM8A
MEH3SBW	Straight	Banana	Wire	No Port	w/Cap	ISO-80, ISO-DAM8A
MEH3SF	Straight	Female	Pellet	No Port	w/Cap	705, 773, 767, 721, FD223
MEH3SFW	Straight	Female	Wire	No Port	w/Cap	705, 773, 767, 721, FD223
MEH3SW	Straight	Male	Wire	No Port	w/Cap
MEH3W45	45°	Male	Wire	No Port	w/Cap	705, 773, 767, 721, FD223
MEH6RF	Right	Female	Pellet	2.0-mm Port	w/Cap	705, 773, 767, 721, FD223
MEH6RFW	Right	Female	Wire	2.0-mm Port	w/Cap	705, 773, 767, 721, FD223
MEH6SF	Straight	Female	Pellet	2.0-mm Port	w/Cap	705, 773, 767, 721, FD223
MEH6SFW	Straight	Female	Wire	2.0-mm Port	w/Cap	705, 773, 767, 721, FD223
MEH7	Right	Male	Pellet	2.0-mm Port	w/Cap
MEH7W	Right	Male	Wire	2.0-mm Port	w/Cap
MEH8	Right	Male	Pellet	No Port	w/Cap
MEH900R	Right	Male	Pellet	2.0-mm Port	w/Cap	900A
MEH900S	Straight	Male	Pellet	2.0-mm Port	w/Cap	900A
MPH1	—	None	None	Female Luer	w/Cap
MPH3	—	None	None	Male Luer	w/Cap
MPH4	—	None	None	2.0-mm Port	w/Cap
MPH6P	Right	Male	Pellet	Female Luer	w/Cap	Piconozzle Kit (5430-XX)
MPH6R	Right	Male	Wire	Female Luer	w/Cap	Piconozzle Kit (5430-XX)
MPH6S	—	None	None	Female Luer	w/Cap	Piconozzle Kit (5430-XX)

SPECIFY O.D. OF GLASS (-1.0, 1.2, 1.5 OR 2.0 mm-) WHEN ORDERING.