Group 8 – BASS Catchers

By automating the sampling process, autosamplers provide a faster and more accurate alternative to manual injection. However, they are not perfect, and many lack desirable characteristics like low cost, temperature control, compact size, short sampling times, and high precision. Our team was tasked with developing a high-speed, high-accuracy autosampler with a temperature control module that precisely delivers sample volumes between 0.5 and 500 microliters. The total production cost had to remain below $5,000. We present an autosampler design that tackles each of these concerns. It contains four subsystems: an enclosure, a movement system, a temperature control system, and a fluids system. They work together to deliver a desired sample volume from a test tube to an analytical instrument. The enclosure houses most components within a compact array of aluminum tubing connected by 3-way nylon corners. Polycarbonate lids offer a view of the sampling process, with hinges allowing entry on one side. Test tube racks are placed above the temperature control module, which uses a temperature controller, heat sink, and thermoelectric plates to vary sample temperature from 4 °C to 37° C. The movement system uses lead screws with stepper motors to move the needle to test tubes for injection and the beaker for cleanup. The fluids system uses the push-to-fill mode of injection to precisely aspirate the sample and carry it to the analytical instrument. It does so by combining a microsyringe pump, six-port injection valve, and peristaltic pump with corresponding tubing. Calculations verified that the temperature control system can successfully vary sample temperatures in the desired range; the enclosure and movement system can withstand expected loading; and the fluids system can sustain expected pressures. The design offers low sampling times, as low as 20 seconds for a 0.5-microliter sample, and comes at a price tag of $3,355.12.