Introduction

Key Points
The use of short-path-length cells allows measurements of samples with a large optical rotation.
JASCO offers cells with path lengths of 10 mm, 20 mm, 50 mm and 100 mm.

Some types of pure liquid* cannot be measured with a polarimeter and a normal 100-mm-path-length cell because their optical rotation exceeds 90 degrees. JASCO offers cells with short path lengths that enable measurements of samples with a large optical rotation. This application note describes optical rotation measurements for orange oil with a 50-mm-path-length cell.

*Pure liquid: a liquid substance composed of only one type of molecule

Fig. 1. P-4200 polarimeter

Experimental

Sample
Orange oil (research use)

System
Instrument:  P-4200 polarimeter (Fig. 1)
Cell:   RQC-451 8.5-mm rectangular quartz cell (path length: 50 mm) (Fig. 2)

Fig. 2. Rectangular cell

Parameters
Light source:  Na lamp
Wavelength:  D line
D.I.T.:  5 sec
Repetition:  1 time

Keywords

Polarimeter, short path length, pure liquid, orange oil

Results

The measurement results are shown in Table 1. The blank measurement was performed using a dry empty cell.¹⁾ The use of a 50-mm-path-length cell allowed the optical rotation for orange oil to be measured without dilution, as the measured value remained within 90 degrees.

Table 1   Results

Fig. 3. Measurement screen
Top: The current optical rotation and temperature are displayed in the monitor.
Bottom: Sample names can be added to the list for future measurement.

Conclusion

Using a short-path-length cell, samples with a large optical rotation can be measured without dilution.

References

1.United States Pharmacopeial Convention: “USP-NF 2024 Issue 3”, (2024).
2.Ministry of Health, Labour and Welfare: June 7, 2021, MHLW Ministerial Notification No. 220, “The Japanese Pharmacopoeia 18th edition”, (2021).