Calculating Dilutions in the Lab

Summary

Highlights

• Learn to calculate dilutions with ease 🧮!
• Understand metric prefixes: milli, micro, nano 📊.
• Conservation of mass helps in finding the correct volume 📏.
• Start with a concentrated solution and dilute wisely 🔍.
• Aim for a 1 to 200 dilution using the right math 🧩.
• Ensure your experiment accuracy with paper calculations ➕.
• A minor volume error is often acceptable in biology 🌡️.

Key Takeaways

• Dilutions are an everyday task in labs 🧪.
• Metric prefixes like milli, micro, and nano are crucial 📏.
• Use conservation of mass to calculate dilutions efficiently ⚖️.
• Remember: Starting concentration x Starting volume = Final concentration x Final volume 🔄.
• 1 to 200 dilution means you'll need less concentrated solution 🎯.
• Practical tip: do calculations on paper to avoid mistakes ✍️.
• Acceptable errors in biology are generally under 1% ✅.

Overview

Calculating Dilutions in the Lab Transcription

• 00:00 - 00:30 do [Music] hi everybody welcome back to synthetic biology one today we're going to talk about a very practical skill that you'll use every day in the lab calculating dilutions so what volume of a given 10 millimolar
• 00:30 - 01:00 stock solution is required to make 20 mils of a 50 micromolar solution are you bored yet me too but when you're working in the lab this kind of problem comes up every day somehow nothing is ever at the concentration you need before we begin let's remember our metric prefixes in biology there's three that we use all the time milli indicates division by 1 000 or 10 to the
• 01:00 - 01:30 third micro indicates division by 1 million or 10 to the sixth that greek letter is called mu by the way and nano indicates division by 1 billion or 10 to the ninth once you use these enough they'll start to become second nature okay now let's do some math and we'll figure this one out
• 01:30 - 02:00 the official method for doing this calculation makes use of the conservation of mass we're starting with a small amount of solution at a high concentration and we end up with a large amount of solution at a low concentration but the total amount of diluted stuff stays equal this fact allows us to write the following equation the starting concentration times the starting volume
• 02:00 - 02:30 equals the final concentration times the final volume so to calculate the starting volume we divide both sides by the starting concentration it turns out we mean we need 0.1 mils or 100 microliters in a total volume of 20 mils another way to think about this calculation is to focus on the dilution factor i start with 10 millimolars and i want to go to 50 micromolar
• 02:30 - 03:00 so that means i want a 1 to 200 dilution the final volume i want is 20 mils so 20 divided by 200 is 0.1 mils for some people breaking the calculation into two steps like this it just makes the arithmetic easier when you start out in the lab you should probably do these calculations on paper even if you're a super cool math dude like me it's easy to make a mistake and screw up your experiment
• 03:00 - 03:30 now after i finish this calculation i would measure out my my 20 ml of water and add my 0.1 mil of concentrated solution but remember that this is wrong bad but in this problem we wanted the total volume to be 20 mils if we do it my way we'll end up with a volume of 20.1 mils but i'm lazy it's hot usually it's just easier to measure the added volume rather than the total volume besides
• 03:30 - 04:00 uh the total volume error in this case is less than one percent biology is not rocket science there are very few experiments that will be hurt by one percent error so i won't tell if you won't okay until next time happy diluting [Music]
• 04:00 - 04:30 you