well 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 one
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 this 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 a 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
warm up 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 okay 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 some nickel sulfate I'm
going to put it in here spectrometer and
all I have to do to look at the entire
absorption factor of nickel sulfate is
click this little collect button and
that's a nice absorption spectra so you
can see right here we have we have a
really high absorbance in the purple to
blue and then very little absorbance in
the blue to green and that 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
that you can minimize the rainbow
background on the labquest and that's by
just 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 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 it red food
coloring now red food coloring it's
probably going to absorb mostly in the
green
there we go so if you look here at this
absorbance peak from red food coloring
you can see that it absorbs a little bit
in this 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
the solution that's why the solution is
actually red so let me show you one
other activity and this is the reason
why this but kilometer 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 that this
takes about 12 2 minutes so I'm going to
go back here to the meter screen I'm
going to select File new 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 warm up I'm going to finish the
calibration
select okay and now I'm going to take my
chlorophyll extraction place it in
spectrometer hit the collect button and
voila there we have it so actually let's
take a look at 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
why I really love this device is that
this lab now can be done in about two
minutes and then you can 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
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
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 two LEDs that
can be used for fluorescence in the
spectrometer one is a purple LED which
is at 405 nanometers and another one
which is it's like an aqua green LED
which is at 500 nanometers
now the 405 nanometer 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 actually 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're 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 height here it's at
about 0.6 to really look at a good shape
or a good for us at peak it'd be nice if
this peak was a little bit taller a
little bit closer to about 1.8 or point
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 that
you've put in here is overloaded the
detector now you would never want to
change the sample time if you are 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're
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 wavelengths
moving samples to average I'm just going
to change this number right here that's
a 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 that 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 okay
and then now let's 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
height on this one is right at about
0.75 eighth fluorescence and these are
in relative units they're they're
basically unitless but I can actually
look at both by tapping here looking at
all runs and you can see there are two
peaks I actually increase 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
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