Interactive numerical educational resources for the analysis of complex media
Calibration Preparation of the calibration range
So, we have to make a standard range
from a stock solution of copper
We need to check to avoid mistakes
we need to make a blank
the stock solution is at 1 g/L
and we have to prepare solutions at 500 mg/L
250, 100, 50 and 10
So, with the blank
it means that we need 6 flasks
We only have 5 flasks of 25 ml
and one of 50
Ok, so we need to get another flask of 25
we won’t make a standard in the 50 ml flask
It doesn’t matter
it is still possible to make 50 ml
it won’t change the concentration
Alright
First
let’s check if there are pipettes and pro-pipettes available
That’s alright
I think it is better to prepare them with an increasing concentration
That way, we don’t need to mark the flasks because if we mark them
it’s a bit annoying
So, let’s start with the blank
and then we go from the less concentrate to the most concentrate
Ok
Therefore, maybe we can use the 50 ml flask
for the highest dilution
it’s seem logical
In that way, we’ll use a lower volume
Ok?
So, first I’ll go grab the stock solution
I will first make the blank
it is simpler
ok do it
at least, it’ll be done
Wait
don’t use water
We need to make the standard range into nitric acid
Because if you use water
it could change the HNO3 concentration
and it could change the dilution of the solutions
You are right
I won’t sample directly from the tank
I will use a big beaker
because if the pipette is contaminated
it will contaminate all the tank
and we won’t be able to make our standard range
So I’ll put some of it in here
Do we mark it?
Uff it is not necessary, we know what is in there
It is better to mark it because it is uncoloured
we could think it’s water... just to be sure
ok, let’s note it
So, I will start by taking 10 ml
and I will repeat the process several times
That’s it, it is marked
Ok, I am doing the blank
it will be fast
For the stock solution
do you want me to begin now? Where is it by the way?
The stock solution is in the fridge
you can go grab it
Concerning the blank, it is not necessary to fill it until 25 ml
I am grabbing the stock solution
but I am doing it anyway, as the others
and I am starting by making the 0.5 solution ok?
we’ve said that
this is 1 g/L
What we can do
because I have started with the nitric acid
you add the stock solution in each flask
and I put the diluent
alright?
Sure
First
I am finishing the blank
and then I am putting
a small amount of diluent in each flask
to do it well
I won’t put too much
it is not necessary
Personally
I am doing the first dilution
we agree
this is the blank
and then from the most diluted
to the most concentrate
to be sure
So, 500
we have 1g/L
so we need to divide by 2
I have a flask of 25 ml
so I need 12.5 ml
I am waiting, I need the pro-pipette
I am almost done
In that way we don’t need to write the calculation
it is just a cross product
it’s not really complicated
But
you cannot sample right now
because the stock solution just came from the fridge
it is still cold
You won’t get the good volumes
if you sample it at 5-6 degrees
So, what do we do?
Well, we can go for a coffee
and come back later
ok for me
waiting for it to get warmer
First, let’s put the gloves back
Ok, after a good coffee
we are ready for the standard range
The stock solution is not cold anymore
we can start
I prefer if I sit
while I am doing my samples
I am grabbing a stool
and I will sit over here
That way, you will start by adding the stock solution
and I will finish by adding the acid
Can you give me the 500 flasks?
Which one is it?
This one?
is it the 500 flask?
Yes, it is
So, you need to dilute twice
so you need to sample …
12.5
exactly
Here we go 12.5 ml
I will need the pro-pipette
Yes, you can use it
I’ll use the other one
Yes, you can take this one
it is too big for my pipette
I am doing the second one?
Which one is it?
It’s the 250
Yes, it is also easy
Wait, how much is it?
I am a bit lost …
I think it would be great to write the calculation
because I am starting to be lost
No that’s easy
I finish this one
and we dilute it twice
don’t we?
Well, it is not ideal...
it is better to use the stock solution
because if I did a mistake on this one
the mistake will be repeated on the next flask
So, the best thing to do is to use the stock solution
Alright
And I think that we need to write the calculations
because I won’t be able to make them in my head
Yes, since if we make a mistake
we’ll have to start all over again
Let’s write the calculations
So, we have a 1 g/L solution
and we want one at 250 mg/L
for 25ml
finally finished
Did you find it?
For the 250 one I got 6.25 ml
for the 100 one I got 2.5
for the 50 one I got 1.25
for the 10 one I got 0.25 ml
Yes, I got the same
So, let’s go
Too easy for the rule of 3 ?!
Wait Mathieu!
I think you made a mistake for this dilution…
What? What did I do?
Look the colour
This is not normal, it is supposed to be less intense
I did what you said…
Oh wait …
I put 12ml again
I forgot that we’ve already done the first one
That’s it. It is twice less, so it is 6.25
Alright. What do we do now?
Well …
we cannot divide it by two
We take a new flask and we redo it
So, this time I won’t make any mistake
I’ll take 6.25 ml
You know what
to avoid any more mistakes
I’ll write the concentrations on each flask.
Yes, it’s better
It would be silly to be wrong again
So, this one is 500 mg/L
So, which one is the 250 mg/L?
Well, you can take this one
Thank you
So, here I need 6.25 ml
The troubles continue...
I have a problem for the 10
because I need to sample 0.25 ml
and I don’t have anything to do that
Oh, but we forgot that we use a 50 ml flask!
So, it means that I need to sample 0.5
That’s right
But I don’t have enough
Well in that case, we don’t make it
We have to do it
we need a point to draw the calibration line
Otherwise
I could use the solution of 100 mg/L
As the stock solution is too concentrate
we could use the 100 solution and dilute it 10 times
Smart! And also, the taken volume will be bigger
So, I have a flask of 50 ml
so I need to take 5 ml
You should write the calculation to avoid any mistakes
So, I have a solution of 100 mg/L …
Is the solution of 100 ready?
No! You want the solution of 100, right?
Yes
Wait, I have to mix it first
Because if you sample it without mixing it
the concentration will be wrong
ok
It is almost ready
Are you sure you need this one?
Did you write the calculation?
Yes, I did
I need to take 5 ml of the solution of 100
in order to get 10 mg/L
This is the well mixed solution of 100
Thank you
Wait, don’t do that
What?
If your pipette is not well rinse
you will contaminate it
Put some of it in the small beaker
and sample it from the beaker
alright
everything is good?
Yes
Nice, we got a beautiful degraded blue
Perfect
we can start the analysis
Calibration Preparation of the calibration range
Interactivenumerical educational resources for the analysis of complex media