Photo courtesy of Miele ProfessionalBecause your tests need to produce accurate, reliable results, you probably use pipettes to measure and dispense the liquid reagents. The more exacting your experiments, the more likely you are to put reusable glass pipettes to work. After all, their disposable cousins, plastic pipettes, are not calibrated as precisely.
Despite your good intentions, you could unknowingly be opening the door to a whole new arena for inaccuracies. That’s because glass pipettes, by nature skinny and fragile, are difficult to clean. And while ensuring accurate liquid volumes is essential for correct results, it’s also essential to have residue-free pipettes.
If you are not 100 percent confident that your laboratory tools are clean, you will never know for sure whether chemicals from previous experiments interfered with your test results.
The Cleaning Equation
Given the necessity to employ contaminant-free pipettes, it helps to understand the four variables of the cleaning equation that you need to balance to produce them—water action, temperature, detergent and time.
If you add more of one variable, you may be able to use less of another. To understand this, imagine the smooth, clean stones at the bottom of a rushing stream. Because water has rushed over them for decades, they are unsoiled. Having basked in the luxury of time, they needed no detergent or increase in water temperature to shine their surfaces. When meeting testing deadlines, however, you cannot afford to wait. So, to reduce time, you need to optimize the use of detergent, heat and water circulation.
Spray and Pray: The Plastic Siphon Tank
Despite today’s understanding of what “clean” glassware means, many labs cling to washing techniques scientists have been using for 60 to 70 years. Like other labs, you may still be using a plastic siphon tank washer to clean 75 to 100 pipettes at a time. You connect it to your water tap, turn on the water and let it run. The tank fills, drains and refills. This water-guzzling process keeps going until you turn off the water. Perhaps somewhere along the line you toss in a detergent tablet to power up your cleaning process.
Using a siphon tank is wasteful, ineffective and time-consuming. It:
- Squanders Resources
You use a lot of water and, if it’s hot, you needlessly burn up energy.
- Produces Poor Results
There are a few contributors to the siphon tank’s lack of effectiveness. First, there’s no DI rinsing to remove tap water residues. Second, pipettes are not dried, so lab techs have to place them in the oven to dry them. Inevitably, in handling the wet pipettes, they end up breaking some of their delicate tips, rendering them useless. Finally, it’s unlikely you will be able to balance the cleaning equation. That’s because the amount of time you turn on the tap may vary, perhaps from one to four hours, and the amount of detergent you add can be just as arbitrary. If you opt for a one-hour cleaning time, as many do to save time, you deprive the pipettes of the required cleaning duration.
- Time Consuming
The pipette cleaning process takes time and can distract the lab tech from being as productive as possible.
While clean pipettes are essential for testing accuracy, many labs are not putting enough emphasis on hygiene. They are mostly using plastic siphon tanks which result in a wasteful, ineffective and laborious cleaning process. To learn how to solve this problem, read Part 2 of the Pipette Cleaning Series: Getting the Pipette Cleaning Equation Right Every Time.