LIGHT TRANSMISSION
Apparatus1—
Use a spectrophotometer of suitable sensitivity and accuracy, adapted for measuring the amount of light transmitted by either transparent or translucent glass or plastic materials used for pharmaceutical containers. For transparent glass or plastic pharmaceutical containers, use a spectrophotometer of suitable sensitivity and accuracy for measuring and recording the amount of light transmitted. For translucent glass or plastic pharmaceutical containers, use a spectrophotometer as described above that, in addition, is capable of measuring and recording light transmitted in diffused as well as parallel rays.
Preparation of Specimen—
Glass—
Break the container or cut it with a circular saw fitted with a wet abrasive wheel, such as a carborundum or a bonded diamond wheel. Select sections to represent the average wall thickness in the case of blown glass containers, and trim them as necessary to give segments of a size convenient for mounting in the spectrophotometer. After cutting, wash and dry each specimen, taking care to avoid scratching the surfaces. If the specimen is too small to cover the opening in the specimen holder, mask the uncovered portion of the opening with opaque paper or masking tape, provided that the length of the specimen is greater than that of the slit in the spectrophotometer. Immediately before mounting in the specimen holder, wipe the specimen with lens tissue. Mount the specimen with the aid of a tacky wax, or by other convenient means, taking care to avoid leaving fingerprints or other marks on the surfaces through which light must pass.
Plastic—
Cut circular sections from two or more areas of the container, and wash and dry them, taking care to avoid scratching the surfaces. Mount in the apparatus as described for Glass.
Procedure—
Place the section in the spectrophotometer with its cylindrical axis parallel to the plane of the slit and approximately centered with respect to the slit. When properly placed, the light beam is normal to the surface of the section and reflection losses are at a minimum.
Measure the transmittance of the section with reference to air in the spectral region of interest, continuously with a recording instrument or at intervals of about 20 nm with a manual instrument, in the region of 290 to 450 nm.
Limits—
The observed light transmission does not exceed the limits given in
Table 1 for containers intended for parenteral use.
Table 1.
Limits for Glass Types I, II, and III and Plastic Classes I–VI
|
Maximum Percentage of Light Transmission at Any Wavelength Between 290 and 450 nm |
Nominal Size
(in mL) |
Flame-sealed
Containers |
Closure-sealed
Containers |
| 1 |
50 |
25 |
| 2 |
45 |
20 |
| 5 |
40 |
15 |
| 10 |
35 |
13 |
| 20 |
30 |
12 |
| 50 |
15 |
10 |
NOTE—Any container of a size intermediate to those listed above exhibits a transmission not greater than that of the next larger size container listed in the table. For containers larger than 50 mL, the limits for 50 mL apply.
The observed light transmission for containers of Type NP glass and for plastic containers for products intended for oral or topical administration does not exceed 10% at any wavelength in the range from 290 to 450 nm.
