Polarized light screen technique

Polarized Light Screen (PLS). The PLS technique (23,24) was used extensively to obtain Immediate information about the macroscopic phase behavior of solutions. Diffuse light is transmitted through a polarizer and an analyzer. The sample is placed between the two polarizers, and system behavior is observed as shown in Figure 1. 

All parenterally injected solutions should be checked for particulate contamination but the above procedure is clearly impractical as a bulk screening exercise. Those products contaminated with particulate matter should be rejected. In practice, all products may be tested individually by humans against split white/black screens and/or under polarized light for obvious particulate contamination and again there is a method described in pharmacopoeias based on the split screen technique. Nowadays optical control equipment can take over this arduous and boring employment. 

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