Precision constant current sources for microiontophoresis
During an experiment the resistance of an iontophoresis pipette may fluctuate for a variety of reasons (mostly biological). This requires a precision constant current source (or iontophoresis pump as it is popularly called) which automatically maintains a constant current flow through the barrel, independently of the electrode resistance. An iontophoresis pump, in compensation to fluctuations in tip resistance, automatically changes the voltage applied to the iontophoresis pipette. Microiontophoresis pumps come in two basic varieties:
- (1) Pumps which deliver currents in the 1-10 microampere range for extracellular deposition of dyes and tracers and
- (2) Pumps which deliver currents in the nanoampere range for intracellular dye or tracer deposition or to determine the effects of extracellularly applied substances upon firing parameters of neurons. In the latter case, extremely small amounts of neuroactive substances (transmitters, modulators, hormones, drugs) ejected into the near vicinity of neurons to study the pharmacological responses of single nerve cells.
Our BAB-501 iontophoresis pump was designed specifically for iontophoretic deposition of neural dyes and transport tracer substances such as Pontamine Sky Blue, Horseradish peroxidase (HRP) or Phaseolus vulgaris leucoagglutinin. It provides constant currents up to 20 microampere with either polarity, its maximum compliance voltage is 500 V.
The Union-40 iontophoresis pump is for intracellular deposition of tracer substances as well as for extracellular ejection of neuroactive substances to test their effects on cell firing. It is capable of driving 100 nanoampere current through pipettes having resistance as high as 400 MegOhm.
The BAB-501 microampere iontophoresis pump for extracellular tracer deposition
The maximum output current is 20 microampere set by a ten-turn ("Current") dial with an accuracy of 0.01 microampere. Three modes of operation can be selected. In continuous mode, iontophoresis current is continuously generated when the polarity switch is in "Positive" or "Negative" position. In external mode, the BAB-501 can be gated through its "Ext.In" BNC jack by any logic pulse generator or computer. The output current is on whenever the gating input is logic high, off when it is logic low. In pulse mode, an internal timer turns on the output current for 7 s in every 14 s generating 7 s on/7 s off cycles. Polarity of the output current is switch selected. A built-in 10 Mohm resistor can be selected for termination to preset required current. The current sensing resistor is in series with the current source providing a true measurement of the output current. Please, find the BAB-501 manual here.
Specifications
| Output current range: | 0±20 microampere |
| Compliance voltage: | ±500 V, maximum |
| Polarity: | +/Off/-, switch selectable |
| Termination: | Electrode (micropipette) or 10 MOhm internal dummy load |
| Load configuration: | Floating |
| Mode of operation: | Continuous/Externally timed/Pulsed (internal timer) |
| External timing: | Through Input BNC jack. Optical isolation |
| Pulse duration: | 5 seconds, factory set |
| Duty cycle: | 50% (7 s on/7 s off) |
| Dimensions: | 6.67" x 2.19" x 6.45" (169.5 x 55.6 x 164 mm) (WxHxD) |
| Weight: | 1.7 lb (770 grams) |
| Power source: | 12 V DC external power supply, purchase separately |
To place an order see Kation Scientific's Order and Price list page.
The Union-40 nanoampere iontophoresis pump for intra- and extracellular studies
This model is an upgraded version of our previous Union-36 iontophoresis pump. This precision constant current source may be operated in two switch-selectable current ranges. The 0-20 nA range is for intracellular dye or tracer deposition. The 0-200 nA range permits extracellular delivery of various substances to test their effects on neuronal firing. The retention and ejection currents can be set by the respective front panel knobs with an accuracy of 0.1 nA. Switching between the retention and ejection currents can be done manually using the 'Mode' selector switch or can be automated through the back panel 'Remote' BNC jack using a computer or timer. The ejection current is activated whenever the remote input is logic high, retention current is on when it is logic low. The polarity of the ejection current is switch selected, while the polarity of the retention current is automatically set. The current sensing resistor is in series with the current source providing a true measurement of the output current. The output current can be monitored by computer or chart recorder using the back panel 'I monitor' BNC jack. Requires an external 12 VDC power supply. Shipped complete with user guide. Please, find the Union-40 manual here
Specifications
| Ejection current range: | 0- ±200 nA or 0- ±20 nA, switch selectable |
| Retention current range: | 0- ±20 nA or 0- ±2 nA |
| Compliance voltage: | ±40 V, maximum |
| Max. pipette impedance: | 400 MegOhm at 100 nA output, 200 MegOhm at 200 nA output. |
| Load configuration: | Floating |
| Mode of operation: | Manual 'Retain' or 'Eject' by toggle switch, 'Remote' by external timer or computer |
| Remote control: | Through back panel 'Remote' BNC jack by TTL or CMOS signals. Optical isolation is up to 5000 V. |
| Current monitor: | Through back panel 'I Monitor' BNC jack; 10 mV/nA |
| Dimensions: | 6.67" x 2.19" x 6.45" (169.5 x 55.6 x 164 mm) (WxHxD) |
| Weight: | 1.7 lbs (770 grams) |
| Power source: | 12 V DC external power supply, purchase separately |
| Power consumption: | 350 mA, maximum |
To place an order see Kation Scientific's Order and Price list page.
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