In Vitro Testing Protocol
ALZET pumps are supplied with a specified volume pumping rate determined in isotonic saline at 37°C (± 0.5°C). In the event that the user finds it necessary to test the pumping rate, DURECT recommends that the following steps be taken:
Step 1. Prepare a solution of known concentration of an indicator dissolved in isotonic saline. The amount of indicator pumped out of the pump will be the basis for the pumping rate calculation. Therefore, the indicator solution should be compatible with the pump and be easy to analyze in isotonic saline. One such indicator is FD&C blue #1 dye at 10 mg/ml for all 100 µl and 200 µl sized pumps (except Model 2001D), and 1.0 mg/ml for Model 2001D and all 2 ml sized pumps.*
Step 2. Fill the ALZET pump with the indicator solution. ( Filling procedure )
Step 3. Place the ALZET pump into a 20 ml test tube pre-filled with 15 ml of isotonic saline and pre-incubated at 37°C (± 0.5°C). Cap the tube to prevent evaporation.
Step 4. Record the starting time of the incubation.
Step 5. Transfer the ALZET pump to a new test tube filled with 15 ml of isotonic saline approximately every 12 hours. Record the precise time of the transfer and/or the time interval between transfers.
Step 6. Repeat Step 5 daily for the duration of the pump. (For example, 7 days for Model 2001)
Step 7. Analyze for the concentration of indicator in each test tube against a standard of known concentration to determine the amount of indicator pumped during each time interval. From this amount and the concentration of the indicator in the solution initially loaded into the ALZET pump, calculate the volume pumped during each interval. Divide by the time interval in hours to obtain the average hourly volume pumping rate.
*Note: When FD&C blue #1 dye is used, the recommended wavelength for spectrophotometric analysis is 630 nm.