Automatic Polarimeter is an instrument for measuring the optical rotation of a substance.By measuring the optical rotation of the sample, the concentration, content and purity of the substance can be analyzed and determined.It is widely used in pharmaceutical, drug testing, sugar refining, food, spices, monosodium glutamate, chemical industry, petroleum and other industrial production, scientific research and teaching departments for laboratory analysis or process quality control.

Principle

Based on the phenomenon of optical rotation, that is, in some compounds, the molecular structure causes them to distort the polarization direction of incident light, causing the light to rotate after passing through the sample. When using a polarimeter to measure glucose concentration, a standard solution of a certain concentration needs to be prepared first. Then add the sample to be tested and the standard solution into the polarimeter sample cell in sequence, and measure their optical rotation values. By comparing it with a standard solution of known concentration, the concentration value of the sample to be tested can be obtained.

It should be noted that the appropriate wavelength and temperature should be selected during measurement to ensure the accuracy of the results. At the same time, factors such as air oxidation and light must also be prevented from interfering with the measurement results during the operation.

Instruments and reagents

Polarimeter, washing bottle, plastic tip dropper, filter paper;

Distilled water, 5% glucose solution, glucose solution of unknown concentration.

Experiment content

(1) Preparation of sample solution

Accurately weigh a certain amount of sample and prepare a solution in a 50ml volumetric flask. Usually water, ethanol, and chloroform can be used as solvents. If a pure liquid sample is used for direct testing, only its relative density needs to be determined before measurement.

Since the glucose solution has a variable optical rotation, the glucose solution to be measured should be prepared 24 hours in advance to eliminate the phenomenon of variable optical rotation. Otherwise, unstable readings will occur during the measurement process.

(2) Preheating

Turn on the power switch of the polarimeter and preheat it for 5 to 10 minutes. It can be observed and used only after the sodium yellow light is completely emitted.

(3) Zero adjustment

Before measuring the sample, the zero point of the polarimeter must be adjusted with distilled water. After cleaning the sample tube, fill it with distilled water so that the liquid surface protrudes from the tube opening. Gently push the glass cover along the edge of the tube opening to cover it. Do not bring in air bubbles. Tighten it tightly (tighten it by hand until no water leaks. If it is tightened too tightly, the glass will easily produce stress, which will cause the brightness of the field of view to change, affecting the accuracy of the measurement. degree) screw on the cover. Dry the sample tube, place it in the polarimeter, and close the lid. Turn on the sodium light lamp and adjust the dial to around zero. There will be a situation where the field of view is larger or smaller than zero. As shown in a and b in the figure below. Turn the coarse and fine handwheels to make the brightness of the three parts of the field of view consistent, which is the zero point field of view, as shown in c in the figure below. Write down the dial reading and repeat the zero adjustment 4 to 5 times to take the average. If the average is not zero and there is a deviation, it should be subtracted or added to the measurement reading.

(4) Determination

The sample measurement and zeroing methods are the same. Before each measurement, the sample tube must be cleaned 1 to 2 times with distilled water, and then rinsed 2 to 3 times with a small amount of the liquid to be measured to avoid being affected by dirt, and then loaded with the sample for measurement. Turn the dial to find a zero-degree field of view with consistent brightness under darker illumination. If the reading is positive, it is right-handed; if the reading is negative, it is left-handed. The difference between the reading and the zero value is the optical rotation of the sample when the temperature is measured. Note down the temperature of the sample and the length of the sample tube during the measurement. After the measurement, pour out the solution in the sample tube, wash the tube with distilled water, dry it and put it away.

Measure the optical rotation of the 5% glucose solution 4 to 5 times according to the above method, and fill in the measured values

in the corresponding positions in the table below. Then measure the optical rotation of the glucose solution of unknown concentration 4 to 5 times, and fill in the measured values in the corresponding positions in the table below.

(5) Data recording and processing

Carry out corresponding processing according to the items designed in the table, and finally find the concentration of the unknown concentration glucose solution.

*Difference = Optical rotation average - Zero point average

We can provide

INNOVA Automatic Polarimeter has built-in Peltier precisetemperature control system, which can meet users requirements for detection at constant temperature.The built-inautomatic calibraion program is optional, and the standard automatic calibration tool can be automatically calibratedfrom -45 degrees to +45 degrees, which fully meets the user's demand for controllable measurement accuracy indailyoperation.The multi-level authority management ofINNOVA automatic polaromeler can meet the audit tracking.