Micropipette Holders and Half Cells: World Precision Instruments

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 andCaCl₂. 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

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.
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.
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.
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.
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.
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.
Finally, remember to specify the O.D. of the glass you will be using when you place your order.

Keep in mind these general principles when considering the micropipettes:

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.

Order code	Custom Order	Electric Connection Angle	Connector	Half-Cell	Pressure Port	Screw Cap	Designed for WPI Products
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
MBMPH5-7		----	None	None	Female Luer	w/Cap
MEH145	Yes	45°	Male	Pellet	No Port	No Cap
MEH1F45	Yes	45°	Female	Pellet	No Port	No Cap	705, 773, 767, 721, FD223
MEH1R		Right	Male	Pellet	No Port	No Cap
MEH1RF	Yes	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	Yes	Right	Male	Pellet	Male Luer	w/Cap
MEH2RF	Yes	Right	Female	Pellet	Male Luer	w/Cap	705, 773, 767, 721, FD223
MEH2RFW	Yes	Right	Female	Wire	Male Luer	w/Cap	705, 773, 767, 721, FD223
MEH2RW	Yes	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	Yes	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	Yes	45°	Female	Pellet	No Port	w/Cap	705, 773, 767, 721, FD223
MEH3FW45	Yes	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	Yes	Right	Female	Wire	No Port	w/Cap	705, 773, 767, 721, FD223
MEH3RW	Yes	Right	Male	Wire	No Port	w/Cap
MEH3S		Straight	Male	Pellet	No Port	w/Cap
MEH3SBW	Yes	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	Yes	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	Yes	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	Yes	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	Yes	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	Yes	Right	Male	Pellet	Female Luer	w/Cap	Piconozzle Kit (5430-XX)
MPH6R	Yes	Right	Male	Wire	Female Luer	w/Cap	Piconozzle Kit (5430-XX)
MPH6S		—	None	None	Female Luer	w/Cap	Piconozzle Kit (5430-XX)