Before the measurement, the instrument and sample should be placed in a constant temperature room at 20 ° C ± 0.5 ° C or a constant temperature room at a specified temperature. A constant temperature water bath can also be used to keep the sample room or sample test tube constant temperature for more than 1h, especially some optical rotations that have a large effect on temperature Matter is especially important.
a. Before turning on the power, you should check whether there are foreign objects in the sample room, whether the sodium light source switch is in the specified position, whether the indicator switch is in the off position, and whether the instrument is placed in a suitable position. .
b. After the sodium light lamp is turned on, the normal lighting time is at least 20min before the light can be stabilized. When measuring, the sodium light lamp uses DC power as much as possible to make the light stable. If there is a polarity switch, the polarity should always be changed after shutdown to extend the life of the sodium lamp.
c. Before the measurement, when the instrument is zeroed, you must repeatedly press the retest switch to make the analyzer deviate from the optical zero position to the left or right, respectively. You can check the repeatability and stability of the instrument by observing the stopping points of the left and right retests. If the error exceeds the specifications, the instrument should be repaired before use.
d. Put the measuring tube containing distilled water or blank solvent into the sample chamber. If there are air bubbles in the measuring tube, the air bubbles should be floated on the convex neck. The glass at both ends of the light-transmitting surface should be dried with a soft cloth. During the measurement, the position and direction of the measuring tube should be fixed as much as possible and marked to reduce the error of the stress on the measuring tube and the cover glass.
e. When the same optically active substance is measured with different solvents or at different pH values, the specific rotation is changed or even the direction of optical rotation is changed due to the different conditions of association, solvation and dissociation. Therefore, the prescribed solvent must be used.
f. Cloudy or small particle-containing solutions cannot be measured. The solution must be centrifuged or filtered first. Discard the initial filtrate for measurement. Some solutions that have a large change in optical rotation after seeing light must be protected from light. Some of the storage time has a greater impact on the optical rotation, and the reading must be measured within the specified time.
g. When measuring the blank zero point or the test liquid stopping point, the reading should be taken three times and the average value should be taken. For strict measurement, the zero point should be corrected with a blank solvent before each measurement. After the measurement, check the zero point for any changes with reagents. If the zero point is found to be greatly changed, the measurement should be repeated.
h. At the end of the measurement, the measurement tube should be washed, dried and returned to its original location. The instrument should be kept away from dust in a dry place. A small amount of desiccant can be placed in the sample room to prevent moisture.