Pasco Scientific PS-2235 User manual

®
Reference Guide
013-14434A
Polarimeter
PS-2235
[phone]
[email protected]
Hardware Data Collection Software1
USB
Port
ON/OFF
Button Battery Status
LED
Bluetooth Status
LED
USB Status
LED
Lid
USB Cable
100 mm Sample Cell
Thumb-
wheel
Chamber
Holder
Quartz
Window Initial Step: Charge the Battery
Included Equipment Part Number
Polarimeter PS-2235
100 mm Sample Cell
USB Cable
Required Item
Data Collection Software (see www.pasco.com/software)
Replacement Item
Replacement Sample Cell PS-2234
PASCO Capstone SPARKvue*
• Mac OS X • Mac OS X
• Windows • Windows
•iOS
•Android
(Capstone UI-5400) (SPARKvue PS-2400)

®
Polarimeter PS-2235
2013-14434A
1See the PASCO web site at www.pasco.com for more information
about PASCO data collection software
*NOTE: SPARKvue also supports a Chromebook device it is con-
nected through USB.
Charge the Battery
The Polarimeter battery is partially charged at the factory. The
battery can be charged using the USB cable connected to a USB
port or USB charger. Leave the Polarimeter off while charging.
As the battery is charging, the Battery Status LED (light-emitting
diode) will blink red. When the battery is fully charged, the
Battery Status LED shines green. The charger circuit inside the
unit turns itself off when the unit is fully charged, so it can’t be
overcharged.
Battery Life
On a full charge, the Polarimeter will typically run for over eight
hours during data collection before it needs to be charged.
Introduction
The Polarimeter is specifically designed for measuring the angle
of rotation of plane-polarized light that is caused by optically
active substances. The Bluetooth and USB connectivity enable its
use with tablets and computers.
Theory of Operation
At one end of the chamber is a fixed polarizer disk in front of the
LED light source. At the other end of the chamber is a rotatable
polarizer disk - called the analyzer - and the photo-detector. The
analyzer can be turned using the thumb-wheel. An optical
encoder records the position of the analyzer (rotatable polarizer),
and the photo-detector measures the intensity of light transmitted
through the substance in the Sample Cell.
Plane-polarized light from the end of the chamber with the fixed
polarizer enters the Sample Cell and passes through the optically
active substance. The substance rotates the plane polarized light
clockwise or counter-clockwise by a specific amount. As the
thumb-wheel of the analyzer is turned, the encoder on the
analyzer measures the angle, and the photo-detector records light
intensity.
The data collection software produces a graph of light intensity
compared to angle, and can be used to analyze the data to
determine various properties of the optically active substance.
The Sample Cell is precisely designed so that the distance inside
the cell between the two quartz windows is 100 millimeters
(mm). Therefore, the path length of the substance inside the
Sample Cell is 100 mm (1 decimeter).
Polarimetry
Since 1812, it has been know that certain molecules are optically
active and can rotate plane-polarized light. For example, table
sugar is an optically active substance. Table sugar has a
tetrahedral carbon atom which has four different groups attached
to it. This carbon is known as a chiral center, a stereogenic
center, or an asymmetric carbon. Chiral centers can be organic or
inorganic. The geometry of the chiral center allows the formation
of mirror image molecular forms under the right conditions. One
of the molecular forms is able to rotate plane-polarized light to
the right (dextrorotary), and the other mirror image molecular
form is able to rotate plane-polarized light to the left (levorotary)
by the same angle.
Experimentation is the only way to determine which form of
molecule is which. The procedure consists of preparing a solution
of known concentration and placing it between two polarizing
filters. A polarimeter measures the amount and direction of
rotation of the plane-polarized light.
Specific angle. , is a fundamental property of chiral
substances. The expression of the specific angle to which the
substance causes plane-polarized light to rotate at a particular
temperature, wavelength,path length, and concentration, is as
follows.
where is the measured rotation in degrees (clockwise or
counterclockwise), T is the temperature (degrees Celsius), is
the wavelength of the light source (nanometers), lis the path
non-polarized
light
Polarizer
Sample Cell
Analyzer
plane-polarized
light
sample
rotated-polarized
light


T


T
lc
----
=

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Introduction PS-2235
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013-14434A
length (decimeters) of the solution in the Sample Cell, and cis
the concentration of the solution (gram/milliliter).
A compound will consistently have the same specific rotation
under identical experimental conditions. To determine the
specific rotation of the sample, use Biot’s Law:
Polarimetry makes it possible to determine the purity of solutions
of known compounds and identify unknown substances from a
short list.
Polarizer Demonstrator Accessory
The PASCO Model OS-8172 Polarizer Demonstrator Accessory
works with the Polarizer Demonstrator (OS-9477A) to show the
property of optical activity - the ability to rotate plane-polarized
light. The equipment is large enough to use in front of many peo-
ple.
The Polarizer Demonstrator Accessory includes a bottle support,
two rectangular sample bottles with lids, a diffuser screen, and
thumbscrews for attaching the bottle support and diffuser screen
to the Polarizer Demonstrator stands.
Fill a sample bottle with an optically active substance such as
corn syrup and place it on the bottle support between the two
polarizers. Shine a light through the diffuser screen, polarizer,
and the sample bottle. Adjust the second polarizer to measure the
angle of rotation.
Specifications
Encoder Resolution
The encoder wheel is a bi-directional quadrature-enabled 1,000
cycles per revolution (360°) device. The processor that monitors
the encoder generates a pulse for each edge of the quadrature
encoder that is detected, thus effectively quadrupling the number
of cycles per revolution to 4,000 cycles per revolution. The
encoder resolution is 360°/4,000 or 0.09°.
Accuracy
The analyzer polarizer, the polarizer shaft, and the encoder are
mechanically attached to each other, and the encoder is firmly
attached to the body of the Polarimeter. Since accuracy is
determined by the stability of the mechanical assembly, accuracy
should be close to the encoder resolution, or 0.09°.
Light Source
The LED light source has an output between 585 nm and 596 nm,
or an optimal output of 589 nm. The LED has a built-in lens that
directs the light output to an exit cone that is ±15° off the center
axis which increases the amount of usable light that is directed
along the optical axis. A second lens installed in front of the LED
further enhances the amount of light directed into the Sample
Cell.
Connecting the Polarimeter to a Tablet or
Computer via Bluetooth
For information about Polarimeter and Bluetooth, see the PASCO
web site page www.pasco.com/polarimeter. Check “User
Resources” for information about using Bluetooth to connect the
Polarimeter to the iOS device or an Android™ tablet, or to a
Windows or Macintosh computer.
Connecting the Polarimeter to a Computer
with a USB Cable
1. Connect the small end of the included USB cable into the
USB port on the right end of the Polarimeter
2. Connect the other end of the USB cable to a USB port on the
computer, or into a USB hub connected to the computer.
3. To turn on the Polarimeter, briefly press and hold the
ON/OFF button on the top. After all three status LEDs blink
in sequence, release the ON/OFF button.
4. The USB Status LED will shine green. (NOTE: The
Bluetooth Status LED will slowly blink blue. The Battery
Status LED may also blink to indicate that the battery is
charging through the USB cable.)
Usage
Prepare the Sample Cell
Unscrew the holder at one end of the 100 mm Sample Cell.
Remove the holder and the quartz window from the cell. Fill the
sample cell to the top with the substance to be examined.
Carefully return the quartz window and the holder to the end of
the sample cell, and screw the holder into place.
Gently tap or shake the Sample Cell so that any bubbles in the
sample move to the “bulge” section of the Sample Cell. Be
especially careful to remove any bubbles in the ends of the cell.
 
lc
----
=
Sample
Bottle
Bottle
Support
Diffuser
Screen
Polarizer
Stands

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Polarimeter PS-2235
4013-14434A
Insert the Sample Cell
Open the lid of the Polarimeter and place the Sample Cell in the
chamber. The Sample Cell is an exact fit for the length of the
space in the chamber. The direction of the Sample Cell in the
chamber does not make a difference. Close the lid.
Calibration
1. Pour distilled water into the 100 mm (1 dm) Sample Cell and
insert it in the Polarimeter’s chamber. Close the lid.
2. Start data collection and slowly rotate the analyzer with the
thumb-wheel so you have data to cover 0° to 360°. For better
analysis, you may want to take multiple passes in this data
range.
3. Stop data collection.
4. Record the first angle above 0° where the light intensity is at
a maximum.
To improve the accuracy of this selection, you may wish to apply
a Gaussian fit.
The recorded angle indicates the position where the polarizer and
analyzer are aligned without an optically active substance in the
Sample Cell.
Data Collection
1. Pour your sample into the 100 mm (1 dm) Sample Cell and
put the Sample Cell in the Polarimeter’s chamber. Close the
lid.
2. Start data collection and slowly rotate the analyzer with the
thumb-wheel so you have data to cover 0° to 360°. For better
analysis, you may want to take multiple passes in this data
range.
3. Stop data collection.
4. Record the first angle above 0° where the light intensity is at
a maximum.
To improve the accuracy of this selection, you may wish to apply
a Gaussian fit.
The recorded angle indicates the position where the polarizer and
analyzer are aligned with an optically active substance in the
sample cell.
The difference between the recorded angles represent the
observed angle of rotation for your sample
Experiment Suggestions
Explore the optical activity of inorganic, organic and biochemical
compounds.
•Chiral compound (inorganic and organic) purity by optical
rotation.
•Solution concentration by optical rotation.
•Determine enantiomeric excess in a mixture of dextro- and
levo-rotatory compounds.
•Kinetics studies where the reactants or products are optically
active.
For more resources go to www.pasco.com/polarimeter
Battery
Replacement
If the Polarimeter fails to recharge, the battery may need to be
replaced. Contact PASCO Technical Support for more
information about battery replacement. It is recommended that
the unit be returned to PASCO for battery replacement, if needed.
Troubleshooting the Polarimeter
•If the Polarimeter loses Bluetooth connection and will not
reconnect, try cycling the ON/OFF button. Press and briefly
hold the button until the status LEDs blink in sequence, and
then release the ON/OFF button to turn on the Polarimeter.
•If the Polarimeter stops communicating with the computer
software or tablet application, try restarting the software or
application. If the problem remains, try cycling the ON/OFF
button.
•As a last resort, push a pin into the Reset port on the bottom
of the Polarimeter.
Technical Support
For assistance with any PASCO product, contact PASCO at:
For more information about the product and the latest revision of
this Reference Guide, visit the PASCO web site at
www.pasco.com and enter “Polarimeter” or the product number
(PS-2235) in the Search window.
Limited Warranty
The Polarimeter has a five year warranty. For a more thorough description
of the product warranty, see the PASCO catalog.
Address: PASCO scientific
10101 Foothills Blvd.
Roseville, CA 95747-7100
Phone: [phone] (worldwide)
877-373-0300 (U.S.)
Web: www.pasco.com
Email: [email protected]

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Technical Support PS-2235
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013-14434A
Copyright
The PASCO scientific 013-14434A Polarimeter Reference Guide is
copyrighted with all rights reserved. Permission is granted to non-profit
educational institutions for reproduction of any part of this manual,
providing the reproductions are used only in their laboratories and
classrooms, and are not sold for profit. Reproduction under any other
circumstances, without the written consent of PASCO scientific, is
prohibited.
Trademarks
PASCO, PASCO scientific, PASCO Capstone, PASPORT, and SPARKvue
are trademarks or registered trademarks of PASCO scientific, in the
United States and/or in other countries. All other brands, products, or
service names are or may be trademarks or service marks of, and are
used to identify, products or services of their respective owners. For more
information visit www.pasco.com/legal.
iPod touch, iPhone and iPad
“Made for iPod”, “Made for iPhone” and “Made for iPad” means that an
electronic accessory has been designed to connect specifically to iPod,
iPhone, or iPad, respectively, and has been certified by the developer to
meet Apple performance standards. Apple is not responsible for the
operation of this device or its compliance with safety and regulatory
standards.
iPad, iPad Air, and iPad mini are trademarks of Apple, Inc, registered in
the U.S. and other countries.
FCC Statement
This Class A digital device complies with part 15 of the FCC Rules.
Operation is subject to the following two conditions: (1) This device may
not cause harmful interference, and (2) this device must accept any
interference received, including interference that may cause undesired
operation.
CE Statement
This device has been tested and found to comply with the essential
requirements and other relevant provisions of the applicable EU
Directives.
Product End of Life Disposal Instructions:
This electronic product is subject to disposal and recycling regulations that
vary by country and region. It is your responsibility to recycle your
electronic equipment per your local environmental laws and regulations to
ensure that it will be recycled in a manner that protects human health and
the environment. To find out where you can drop off your waste equipment
for recycling, please contact your local waste recycle/disposal service, or
the place where you purchased the product.
The European Union WEEE (Waste Electronic and
Electrical Equipment) symbol (to the right) and on the
product or its packaging indicates that this product
must not be disposed of in a standard waste
container.
Battery Disposal Instructions:
Batteries contain chemicals that, if released, may affect the environment
and human health. Batteries should be collected separately for recycling,
and recycled at a local hazardous material disposal location adhering to
your country and local government regulations. To find out where you can
drop off your waste battery for recycling, please contact your local waste
disposal service, or the product representative.
The Lithium Polymer (Li-Poly) rechargeable battery used in this product is
marked with the International symbols to indicate the need for the
separate collection and recycling of batteries.