Fluorescent Lamp Chambers

As just presented, Lachman et al. were among the first to promote the use fluorescent lamps for pharmaceutical photostability testing. Throughout the past approximately 50 years, this lamp type has been the most used. Its ready availability, low price, and ready recognition in the normal environment made for easy acceptance. Cabinets utilizing this lamp were easy to fabricate and relatively inexpensive. 

Because these lamps were available in many sizes and wattages, environmental chamber manufacturers, responding to the ICH QIB efforts, were quick to add this feature to their products. This produced a number of different lamps and configuration claims unfortunately little data is available to support the claims. 

A review of many of the chambers currently available and advertised for pharmaceutical photostability follows. Some presentations are lacking because such information was not available at the time of this writing. Readers are advised to check with the individual manufacturers for the latest information. Many of the chambers presented are available with and without certain features such as temperature and humidity control, programmable lighting systems, built in recording devices, etc. For the purpose of this review, only the distinguishing photostability characteristics are noted. 

No recommendation is made but the reader is referred to Chapters 2, 3,4, 6, 7,10 of this book, and the second half of this chapter on mapping for reference data to aid in their selection. 

Binder (23) offers their KBF Series of test chambers, with ICH compliant lighting, for photostability testing. Their lamps are mounted vertically, in the door, behind a protective panel. All units also have an inner glass door(s). The cabinets have proprietary spherical UV and VIS detectors. 

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Donohoue et al. [31] has reported two other kinetic data sets for Cl and Br reactions using a pulsed laser photolysis-pulsed laser induced fluorescence spectroscopy. These data sets are obtained using pseudo-first order conditions with respect to halogens or mercury and experiments were performed at a broad range of temperatures. The authors of these studies indicate an uncertainty estimation of 50% in the rate coefficients due to the determination of absolute concentrations of chlorine and bromine atoms [31]. Sumner et al. [20] reinvestigated both reactions using a 17.3 m environmental chambers equipped with fluorescent lamps and sun lamps to mimic environmental reactions, and evaluated the rate constants... 

Figure 5 Illuminance (upper) and irradiance (lower) photostability chamber mapping of a single photostability chamber configured with both cool white fluorescent lamps and UVA lamps. (Chamber configured with six cool white fluorescent and two UVA fluorescent bulbs, symmetrically arranged—2 cool white, 1 UVA, 2 cool white, 1 UVA, 2 cool white.

The system of Wall et al. (17) consisted of a large Norlake walk-in temperature and humidity-controlled chamber containing fluorescent lamps and a large number of individual sensors to monitor the chambers 160 shelves. This system was computerized to measure all-important parameters including illumination levels, automatically, continuously. 

Figure 43 is a picture of the insides of the chamber finally selected by Brumfield and his associates for their work. This unit has three shelves, each individually configurable. This chamber uses up to seven 40 W, T-5 fluorescent lamps per shelf. The inside is made of polished aluminum to yield spectral, not diffuse reflectance. The following figures are the maps he obtained for different configurations of this unit. 

The irradiation pattern for all chambers using fluorescent lamps will be similar. Slight variation in the patterns will exist due to lamp shapes, i.e., linear versus bi-axial (U-shaped), but essential they will all be very similar. 

Radiation simulating solar radiation was given by a bank of four G.E. 40-watt cool white fluorescent lamps and two Westinghouse 400-watt EHl mercury vapor lamps mounted on one wall of the chamber. The walls of the chamber were covered with aluminized Mylar which provided a reflecting surface. (j>ka for NO2 was 2.8 hr ... 

FIGURE I6 HPLC-UV chromatograms of LY297802 after 3 days and 7 days in a photostability chamber (cool white fluorescent lamps, I7,000 lux). Conditions Zorbax RX-C8 column, 25 cm X 4.6 mm id, 5 mm A = buffer/acetonitrile 95/5, B = buffer/acetonitrile, 25/75 buffer = 25 mM potassium phosphate with pH adjusted to 6.5 with NaOH,UVdetection using photodiode array with Waters Maxplot 200-400 nm gradient elution from 0% A to 100% B in 30 min, I mL/min flow rate. 

Irradiation conditions Two lamps were used for photostress testing a UV fluorescent lamp, 15 W, emitting radiation at 254 nm, and a medium-pressure metal halide lamp. The temperature inside the chamber was below 30°C. The distance of the samples from the radiation source was 5 cm. 

In the lamp industry, the three gases serve as fill gas in specialty lamps, neon glow lamps, 100-watt fluorescent lamps, ultraviolet sterilizing lamps, and very high-output lamps. The three gases have additional applications in the atomic energy field as fill gas for ionization chambers, bubble chambers, gaseous scintillation counters, and other detection and measurement devices. 

Chlamydomonas segnis Ettl. was obtained from Dr. M. Czuba and Dr. D. Mortimer of the National Research Council, Ottawa, Ontario, Canada. The algae were cultivated in Kuhl s liquid medium, (Kuhl and Lorenzen 1964) which was autoclaved prior to use (final pH 6.8). The algal cells were induced to divide synchronously and were incubated in a growth chamber at 25° C with a photoperiod of 12 hr dark/12 hr light at 5.5 Klux from Sylvania cool white fluorescent lamps. The cultures were stirred constantly and bubbled with air... 

Materials and Techniques. The tanks and chambers for treatments 1, 3 and 4 were constructed of 3/16-inch-thick OP-4 Plexiglas those for treatment 2 were constructed of iM-inch-thick OP-2 Plexiglas. Mylar D (thickness 4 mils) was placed over the top of treatment tank 3 to reduce levels of ambient UV-B. Transmission spectra of these materials are shown in Fig. 3. Enhancement of UV-A and UV-B was achieved by placing four FS-20 Westinghouse fluorescent sunlamps underneath treatment tank 4. In order to exclude most of the radiation less than 290 nm wavelength emitted by the lamps, a sheet of 4 mils thick Kodacel (TA 401), which had been preconditioned by exposure to a sunlamp for approximately 100 hours, was placed between the sunlamps and the bottom of the enhanced UV tank. 

P 86] A solution with a commercial fluorescent dye (1.2 mM) and deionized water were fed by syringe pumps into the micro mixer [54], A mercury lamp illuminated the mixing chamber. Filters were used to select between the emission light and the reflected light A microscope with a digital camera was used for flow monitoring. 

Aqueous Flow. Changes in the concentration of fluorescein in the anterior chamber after intravenous injection were measured as early as 1950. Using a slit lamp or objective fluorophotometer, the time course of the fluorescence in the circulating blood and the anterior chamber can be determined in humans. The rate of aqueous flow is approximately 1.5% to 2.0% of the volume of the anterior chamber per minute. Following the early woik other methods were devised to measure aqueous turnover, and all have given comparable results. Anterior chamber fluorometry is also useful in monitoring inflammation after oral or injected fluorescein. 

Fig. 13. Cross sectional perspective schematic of the suspended payload showing a cutaway of the detection nacelles with impeller driven flow through chambers, detection head and lamp modules used in the resonance fluorescence detection of radicals.

How is one to proceed if the sample shows no change after exposure to the 200Wh/m UV dose but is decomposed after the 1.2 million lux hours in a test chamber designed according to Option 1 (e.g., xenon lamp) One possibility is to rerun the test using a filter to eliminate the UV irradiation in excess. Another possibility is to rerun the exposure to 1.2 million lux hours using a cool white fluorescent tube. If the sample is stable to this VIS exposure, it meets the ICH guideline. 

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