Organic Chemistry SOP: PE-POL-1

User manual Perkin Elmer Polarimeter Model 241 MCEdition: 1.1 Date: 2009-02-17 Page: 1 van 3Previous Edition: 1.0 Date: 2008-09-06 Number of copies: 3Written by: H.I.V. Amatdjais-Groenen.

1 Responsibilities.

First person responsible: Helene I.V. Amatdjais-Groenen.Second person responsible: Dr. Dennis W.P.M. Löwik

2 Definitions.

The specific rotation can be calculated using the formula:

o= g /v∗l

Where α is the observed rotation, g is the weight of the material in grams, v is the volume the solution in is made up to and l is the length of the cell in 100 mm units.

3 Description.

This polarimeter can perform automated measurements of the optical rotation of optical active substances with high accuracy. It operates according to the optical null principle; monochromatic light passes trough the polarizer, the sample compartment and then the analyzer to the photo multiplier. The polarizer and the analyzer are orientated to each other in the optical null position. When the (optical active) sample is introduced, the servomotor rotates the analyzer until the optical null is reached and the angle of the rotation is measured. The rotary range is ± 80º. Samples with high optical rotations exceeding 85º the opposite direction of the rotation will be indicated. The displayed value will be the difference between the actual value and 180º.

4 Measurement.

4.1 Init procedure.

• Turn on the instrument by pressing the (red) POWER button.

• Switch on the required lamp: Hg or Na .

Important: Allow 30 minutes warm-up time for the Polarimeter and source lamps to reach equilibrium

Organic Chemistry SOP: PE-POL-1

User manual Perkin Elmer Polarimeter Model 241 MCEdition: 1.1 Date: 2009-02-17 Page: 2 van 3Previous Edition: 1.0 Date: 2008-09-06 Number of copies: 3Written by: H.I.V. Amatdjais-Groenen.

temperature.

• Select the desired spectral line with the filter wheel:o Filter 589 nm for Na

o For Hg the following filters are selectable: 365 nm, 436 nm, 546 nm and 578 nm.

Note: When the mercury lamp is switched on it must cool down for 4 to 5 minutes before re-ignition is possible.

• Select the aperture; ο for 100 mm (10.0 mL) cell, • for 10 mm (1.0 mL) cell

• Allow the instrument to come to the optical null position (with the sample compartment closed).

• Press the ZERO button to reset the display to zero.

• Install the cell (with or without solvent) and allow the instrument to come to the optical null position.

• Press the ZERO button to reset the display to zero.

4.2 Filling the cell.

I mportant: For highly accurate results it is important that the cell windows are clean, finger marks and dust deposits due to static charges can lead to erroneous results.

• Fill the cell with a syringe until liquid is about halfway up the filling port.

• Stopper the filling ports gently.

• Remove bubbles from the cell walls and windows by tilting the cell.

• Wait several minutes to allow temperature equilibration between sample and cell.

• Check for birefringent strikes and inhomogeneity.

• Install the cell and note the value on the display.

Organic Chemistry SOP: PE-POL-1

User manual Perkin Elmer Polarimeter Model 241 MCEdition: 1.1 Date: 2009-02-17 Page: 3 van 3Previous Edition: 1.0 Date: 2008-09-06 Number of copies: 3Written by: H.I.V. Amatdjais-Groenen.

4.3 Calibration.

High purity Sucrose and Dextrose with rotation value specified to five significant figures by the Standard Reference Materials Program of the NIST are available from Rudolph Instruments. Any material whose specific rotation is known to a comparable accuracy can be used as a standard.

Normal white powder sugar (sucrose) can be used for a rough check. This sugar is normally 99.9% pure sucrose and the specific rotation would be around + 66.5°.

• Make solution of 26 g in 100 mL solvent; this should provide about 17.30° ± 0.05° of rotation in a 100 mm tube.

4.4 Test deflection.

With highly absorbing samples (energy meter reading approaching zero) this is a simple check of the instrument performance to decide whether the analyzer is correctly reaching the optical null. By introducing a momentary deflection the correct performance can be positively checked, as follows:

1. For positive rotations.• Briefly push the LEFT button.

• Note the value to which the display returns.

• Briefly push the RIGHT button.

• Note the value to which the display returns (press again if display remains stationary).

2. For negative rotations.• As for 1 except that the RIGHT button is pressed first.

Interpretation:

A) When the digital display returns within noise levels to the same level in both directions the energy is sufficient and the correct optical null is reached.

B) When the digital display does not return to the same value, the energy is to low and the correct optical null is not reached. If possible repeat the measurement with reduced concentration or a shorter path length.