Photo-stability chambers

Abstract An important aspect of all stability studies is the stability chambers themselves. This chapter is intended to provide a description of the different sizes and types of chambers that are available, the chamber tolerances required, and to provide some practical information for qualification, calibration, maintenance and monitoring of the chambers. Temperature, humidity and photo-stability chambers are included. Also included are guidelines on how to handle chamber excursions. 

Refer to Figs. 14.3 and 14.4 for photographs of a photo-stability chamber using a xenon radiation source (Option I) and a photo-stability chamber using two separate radiation sources (Option II). 

Fig. 14.3 Atlas SUNTEST CPS/CPS+ photo-stability chamber, ICH option I (Courtesy of Atlas Material Testing Technology LLC)...

The capability of the photo-stability chamber. Many photo-stability chambers will be unable to achieve 2°C and 5%RH. 

The temperature and humidity tolerances within the chamber should be challenged as part of the photo-stability chamber qualification just as they are for a tempera-ture/humidity chamber. 

As with temperature and humidity chambers, the DQ/IQ/OQ/PQ stages may be handled separately or combined to some degree. There may be very little difference between the qualification of a temperature/humidity chamber and a photo-stability chamber. The following describes what might be added to the qualification guidelines, previously provided in Tables 14.1 (IQ), 14.2 (OQ), and 14.3 (PQ), that make photo-stability unique. 

Preventative maintenance (and cleaning) for photo-stability chambers will depend on the type of chamber and variables such as (1) does the chamber control temperature or humidity, (2) does it have built-in radiation monitors and (3) is it Option I or Option II. The information provided for preventative maintenance of tempera-ture/humidity chambers (refer to Section 14.6) applies here. The chamber manufacturer will provide specific procedures and frequencies for preventative maintenance and these should be transferred to an internal SOP. 

Photo-stability chambers may be incorporated into the back-up system used for the temperature and humidity chambers although back-up systems are not necessarily as critical for photo-stability as these types of studies can be fairly easily repeated if necessary. Any back-up system in place should be described and tested during qualification. 

Many photo-stability chambers have built-in monitoring systems with output to a computer system for temperature, humidity, and even radiation. These chambers may incorporate a call-out type alarm system. 

Fig. 14.1 ES 2000 74 cu ft Reach-in stability chamber Photo Courtesy of Environmental...

Fig. 14.2 ESI Walk-in stability chamber with CCS Touchscreen control (Photo Courtesy of Metrics Inc.)...

While there is not currently a temperature or relative humidity requirement for photo-stability studies, it is recommended that a specification (tolerance) be established. This requirement may not necessarily be as tight as that for a tempera-ture/humidity chamber. It should take into consideration the following ... 

Door opening, chamber failure, and chamber recovery studies are usually not necessary since photo-stability studies are relatively short in duration, require a small amount of sample, and can more easily be repeated if necessary. 

Monitoring and alarm systems also will depend on the type of chamber and what variables are being controlled. The following should be considered when planning for monitoring and alarm systems for photo-stability ... 

Mineral filler influence on the photo-oxidation of high density polyethylene. Part I Accelerated UV chamber exposure test. Polymer Degradation and Stability, 63 (1999), p. 253 -260... 

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