BASi
Bioanalytical System Inc.
BASi is a drug development firm providing contract research services and unique products for the pharmaceutical, biotechnology and medical device industries.
BASi UniSwitch Syringe Selector
![[Picture of Uniswitch™ Syringe Selector]](images/unisw-1.jpg)
Syringe pumps deliver fluid from a mounted syringe at low (µL/mL) constant flow rate by controlling the forward movement of the plunger. They can be programmed to deliver small volumes of fluid at predetermined intervals or in varying sequences. Consistent flow is required for microdialysis sampling experiments. Analytes diffuse across the dialysis membrane when a concentration gradient is formed between the fluid flowing inside a probe and the fluid on the exterior of the probe membrane. The rate of diffusion tracks the flow rate from the syringe pump. If flow is erratic, so is the rate of diffusion. This can result in variations in concentration of the analyte collected in the dialysate,preventing establishment of basal levels of a targeted analyte.
With these concepts in mind, it is clear that a syringe changeover during a microdialysis experiment is a serious event. If the pump is stopped while tubing from one syringe is moved to another syringe, the flow will also stop, causing a major disturbance in the dialysis gradient. Analyte recovery will be affected. When tubing is reattached, air will be introduced into the fluid stream. Air bubbles may become trapped against the interior of the dialysis membrane and impede recovery along the covered region of the membrane.
The UniSwitch was developed to allow a syringe change during microdialysis or other perfusion experiments without breaking connections, interrupting flow, or introducing air bubbles into the system. It accomplishes this task for up to three independent syringes mounted on the same or independent syringe pumps. This manually actuated liquid switch selects which syringe will be connected to the desired destination. Fluid from the other syringes is routed to waste cannulae.
A UniSwitch can also be used to extend the duration of a perfusion experiment. While one syringe is emptying, another filled syringe can be mounted on a second pump and connected to the UniSwitch. Before the first syringe is completely empty, the second syringe is started and then selected. The operation takes place without interrupting flow, introducing bubbles or breaking a connection.
![[Uniswitch in Action]](images/unisw-2.gif)
This setup delivers perfusion fluid to a single microdialysis probe or sensor. Three syringes are filled with different solutions but only one is connected to the probe at any given time. The other two are routed to a waste vessel. The lever has three positions, which match the relative positions of the three syringes. To change to the fluid in another syringe, pull the lever to realign the cannulae.
Applications
- Perfuse with one solution and change to another solution without stopping flow.
- Extend perfusion beyond the limit imposed by the syringe volume. Begin perfusion in one syringe and switch over to another as the first syringe empties (requires independent pumps at same flow, i.e. the BASi Bee with Hive or Queen controller). Use smaller syringes for better flow performance without sacrificing available perfusion time due to smaller volume.
- Perfuse with smaller, more accurate syringe then switch to larger volume syringe to flush system.
Specifications
| Cannulae | 316 Stainless Steel |
| Inlet Cannula | 2.92 µL |
| Outlet Cannula | 1.58 µL |
| Dead Volume | 0 µL (The UniSwitch is a zero-crossover device with no unswept volume.) |
| Action | Hand-turned stainless steel lever. |
| Positions | 3 positions: 1 per syringe |
| Accessories | Includes 2 meters of FEP tubing and 12 flanged tubing connectors |
| Dimensions | 9.4 x 5.1 x 8.7 cm (L x W x H) |