Measure. Analyze. Learn.
Hello, I'm John Melville from Vernier Software and Technology.
I'm here to talk to you about our little spectrometer,
the SpectroVis Plus.
And, this is one of my favorite devices
that we have here at Vernier.
It's what we call an array spectrometer.
So, unlike older spectrometers that
only looked at 1 wavelength at a time.
This device can actually look at an entire array of wavelengths.
All the way from the violet, up into the red.
And it can do that simultaneously.
So, you can use the device to actually look at
the complete absorption spectra of a compound.
Be that, nickel sulfate, or chlorophyll, or red food coloring.
How this device actually works is
there's a little light source right here,
and the light travels through the cuvette,
it goes through a little diffraction grating,
and, after it goes through the diffraction grating,
that light, that little rainbow of color is spread
across a little detector, which is in the back of the device.
And, that little detector is what can show us
all of these wavelengths simultaneously.
Now, to calibrate it,
I'm actually just going to use a sample of water.
Now, you need to remember that,
when I'm looking at absorbance;
absorbance is a unitless measure.
So, we actually have, we're actually looking at
the amount of light that travels through
some type of solution relative to our blank.
And, in this case, my blank is water.
So, we'll calibrate the device.
I can just tap on the meter screen.
I just select "Calibrate…".
Wait a few seconds for it to be identified.
Now, normally, most spectrometers take
10 to 15 minutes to warm up.
This spectrometer only needs 90 seconds to warm up, and
it's from when the spectrometer is plugged into the device.
So, I've been talking for over 90 seconds,
so I can actually even 'Skip' this 'Warmup' if I wanted to.
And now, I'm going to calibrate the device.
And, most importantly, I'm leaving my blank in here.
Then I hit the "OK" button.
And now, I'm ready to look at a sample.
So here, let's take a look at some nickel sulfate.
So, this is just nickel sulfate.
I'm going to put it in here,
and all I have to do to look at the entire absorption spectra
of nickel sulfate is click this little 'collect' button.
And, that's a nice absorption spectra.
So, you can see right here,
we have a really high absorbance in the purple to blue;
and then, very little absorbance in the blue to green;
and then, it increases in the red.
Now, this may be a little bit difficult to see,
so I'm going to show you a little trick to make it so you can
actually minimize the rainbow background.
I actually really like the rainbow background,
but there's a really neat way you can minimize the
rainbow background on a LabQuest,
and that's by just by double clicking near the top of the graph.
Just like that.
So, now you can see peak absorbance in the blue-violet;
very little absorbance here, in the blue to green;
and then, an increase in the absorbance here in the red.
If I wanted to store this run,
I could just hit this little 'store' button right here.
And then I could look at, oh I don't know, red food coloring.
Now, red food coloring,
it's probably going to absorb mostly in the green.
And, there we go.
So, if you look here at this absorbance peak from
red food coloring, you can see it absorbs a little bit in the area
in the blue, and then it increases as we get into the green,
and then it begins to decrease across the green,
but there's very little absorbance here in the red.
That means all of these wavelengths are
allowed to pass through this solution.
That's why the solution is actually red.
So, let me show you one other activity.
And this is the reason why this spectrometer is
actually one of my favorite tools to use,
is because there's an activity that most biologists do,
called looking at the action spectra of chlorophyll.
Now, this lab is done at colleges and high schools.
And, instead of taking 45 minutes,
you'll see this takes about, well, 2 minutes.
So, I'm going to go back here to the meter screen.
I'm going to select "File" -"New"
You can discard this data.
Now, the chlorophyll extraction that I've done,
I've used some spinach and I've extracted
the chlorophyll out of it using isopropyl alcohol.
So, this is my blank, isopropyl alcohol.
I'm going to put that in the spectrometer.
I'm going to recalibrate again.
Now, remember, the device is already warm,
so once the screen comes up, I can 'Skip' the 'Warmup'.
I'm going to 'Finish' the 'Calibration'.
Select "OK".
And now, I'm going to take my chlorophyll extraction,
place it in spectrometer.
Hit the 'collect' button.
And, voilà, there we have it.
So, actually let's take a look at it.
I'm going to double click on the screen again.
And, you can see right here, this is really nice,
this is exactly what most teachers want to see,
is that chlorophyll absorbs a lot in the blue,
and a little teeny bit in the red.
Like I said, this is one of the reasons I really love this device,
is that this lab now can be done in about 2 minutes.
And then, you could go on to do some
very interesting inquiry based activities.
Now, the other really interesting thing about this device,
is that it also is a fluorometer.
What a fluorometer is, is there are some compounds,
like chlorophyll, that can absorb different wavelengths
of light, and then they will re-emit them,
they'll like actually glow.
And this is actually a really important concept
in the biomedical field.
And, it's one of the reasons why plants are able to
absorb energy from the sun, and actually use it.
So, I can show you how to demonstrate fluorescence very easily.
I'm going to go back here to the meter screen.
What I need to do is,
I need to change how this instrument actually works.
So, I'm going to tap on the meter screen,
and I'm going to 'Change' the 'Units' to "Fluorescence".
There are 2 LEDs that can be used for fluorescence
in this spectrometer.
One is a purple LED which is at 405 nm.
And, another one, which is, it's like an aqua-green LED,
which is at 500 nm.
Now, the 405 nm LED is designed for really chlorophyll
and for GFP, which is referred to as Green Fluorescent Protein.
So, I'm going to select '405'.
I'm going to discard all of this data.
And now, what I'm going to do, is I'm just going to,
if you could just look inside this little cuvette,
you would see that it's kind of glowing a reddish color.
So, what I'm going to do, is I'm going to hit 'collect'.
And there we go.
So, here we can see the fluorescent spectra of chlorophyll.
And, this actually includes chlorophyll a, and chlorophyll b.
And, you can see that they emit this peak right here in the red.
Now, what you may have noticed,
is that I didn't have to calibrate the spectrometer
when I was using it in the fluorescence mode.
And this is true, if you your using it in the fluorescence mode
you don't have to calibrate it.
And, that's actually really nice, because if you see the
peak heighth here, it's at about 0.6.
To really look at a good shape, or a good fluorescence peak,
it'd be nice if this peak was a little bit taller,
a little bit closer to about 1, 0.8 or 0.9 would be good.
So, what I'm going to do, is I'm going to show you how to
change what we call the sample time to allow the little
detector in this device to collect more light,
to make this peak bigger.
You can also use that to make the peak smaller, in case
the sample you've put in here has overloaded the detector.
Now, you would never want to change the sample time
if you're using it in absorbance mode.
In absorbance mode, it needs to be calibrated,
and you do not want to change the sample time.
In fluorescence mode, you can change the sample time,
to make the peak that you are seeing bigger or smaller.
So, to change the sample time,
I need to go back to the meter screen,
and I need to touch right where it says "Mode".
And, you can see these data collection parameters.
There's some things called 'Sampling Time',
"Wavelength Smoothing", "Samples to Average".
I'm just going to change this number right here,
that says "Sample Time"
I'm going to make it a little bit bigger.
I'm going to make it "100".
And, I like to think of this, kind of like the shutter speed
on a camera when cameras actually had shutters.
You're actually allowing it to collect more light,
and so the peak will get bigger.
If I decrease the sample time, then I'm decreasing the
amount of time the detector is looking at the sample,
and the peak will get smaller.
I'm just going to tap "OK".
And now, lets just compare these two peaks.
I'm going to store this run.
And now, I will look at the next peak.
There we go.
And, you'll see the peak heighth on this one
is right at about 0.758 fluorescence.
And, these are in relative units. There're basically unitless.
But I can actually look at both by tapping here,
and looking at "All Runs".
And you can see there are 2 peaks.
I actually increased the size of this peak.
So, I hope you enjoyed this little introduction to our
spectrometer, the SpectroVis Plus,
which is one of my favorite devices
that we have here at Vernier.
If you have more questions about spectroscopy,
or about other sensors, just visit our web site:
www.vernier.com