Dual Microiontophoresis
Current Generator
The Dual Microiontophoresis Current Generator (Model 260) is an electrically isolated, battery-operated instrument designed for the electroiontophoresis of dyes, drugs and charged substances from micropipettes. And so...
Two identical battery operated current generators are available. In ordinary use, the two current generators are operated in parallel providing two distinct currents; one for preventing substances in the micropipette from outward diffusion (the retain or hold current) and the second for actively ejecting charged material. For pipettes with submicron tips, a hold current may not be necessary if there is little outward diffusion of pipette material. Model 260 is powered by two 9-volt alkaline batteries per side (four, in total); unique circuitry converts the ±9 V to ±100 V without a transformer, yielding an exceedingly quiet output.
Single Channel Operation
Model 260 contains two completely independent, battery operated current generators which may be operated independently or in parallel connection. The user need only connect his external electrode pair to the red and black output terminals of channel 1 (HOLD) or 2 (EJECT). For currents below 100 nanoamperes the 100 nanoampere range is recommended because one may adjust these low current values with better resolution in the lower current range.
Two Channel Operation, Hold-Eject
The electrophoretic release of charged substances from micropipettes often requires a second current to counter outward diffusion of material from the delivery pipette. This current has been referred to in the literature as "backing, holding or retaining" current. Operation causes a small current to flow in a direction that will offset the spontaneous leakage of the active agent from the pipette until it is required.
AUTO Operation
The timing of current flow from each channel of the model 260 can be externally controlled by a pulse generator or computer that can supply a logic level of at least +5 volts to the AUTO INPUT terminal. Upon application of the +5 volt command potential to the AUTO INPUT terminal, the preset current will flow from the output terminals for as long as the command potential is maintained. Note: If the instrument is in the MANUAL mode, the application of the AUTO INPUT signal will halt the current for as long as this command is maintained. This is the complement of normal AUTO operation.
Compliance Alarms
Each current generator channel contains an audible and visual alarm circuit that warns when the current amplitude is large enough to exceed the compliance voltage; in other words, the load resistance is too high for the amount of current flowing. The user is thus informed that the instrument cannot deliver the amount of current indicated on the panel ammeter. The alarm will also be triggered if the output path is open-circuited by a loose connection, air bubble or a blocked micropipette. The initial compliance voltage exceeds 100 volts but will decrease proportionately as the battery voltage falls with age.
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| OUTPUT | Constant current, floating |
| OUTPUT RANGES | 0 to ±100 nA 0 to ±1000 nA |
| OUTPUT POLARITY | Switch selected |
| COMPLIANCE VOLTAGE | 100 V |
| METER | Analog meters, ±2% accuracy |
| OUTPUT RESISTANCE | >100 M Ohms |
| NOISE | Less than 20 µV typical DC to 10 kHz through 1 M Ohms independent of current delivery |
| LEAKAGE CURRENT TO GROUND | Less than 0.5 nA |
| OVERVOLTAGE ALARM | Front panel light |
| HOLD & EJECT SWITCH | Manual or by remote logic |
| POWER | Four 9 V alkaline batteries, included |
| DIMENSIONS | 17 x 5.25 x 10 in. (43 x 13 x 25 cm) |
| SHIPPING WEIGHT | 13 lb (5.9 kg) |
| Order Numbers | |
| 260 | Dual Microiontophoresis Current Generator |
OPTIONAL ACCESSORIES |
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| 2933 | Rack Mount Kit, 51/4-in. high |