Glasses, Filters, and Containers

Glass plays an important role in pharmaceutics as well as everyday life. It functions as a barrier against the environment, protects us from harmful rays and preserves our foods and medicines. It is useful but can be a problem for some products. Unfortunately, a clear definition of the glass required for each of these purposes is still lacking. To date, no compendium has included a definition even though they are replete with warnings to protect from light.  

As documented in Chapter 12 of this book, glass impurities have been shown to contribute to the photolability of otherwise photostable materials/products. These same impurities can affect the results obtained during photostability testing via their alteration of the absorption curves of the glasses used. 

Filters have generally been used with much regard as to their absorption curves, stability, or reproducibility. Ill-defined terms such a window-glass filters have arisen with little attention being given to their true scientific meaning by the pharmaceutical community. As we shall see not all window-glasses are equivalent. 

This chapter will try to make users aware of the various glasses, filters, and containers (glass and plastic) encountered in normal processing, packaging, and dosing and day-to-day life of pharmaceuticals. Hopefully, this information will allow one to better design and protect materials, products and users from substances that may be photodegradable. 

There are many different types of glasses made that can have an impact of the photodegradation of pharmaceuticals and their testing results. Among these types are fused quartz, soda-lime, borosilicate (e.g., Pyrex) and a variety of colored glasses. These glasses come in a variety of different shapes such as float, sheet, plate, and cylinder blown glass. They may be chemically treated, coated or laminated with plastic, clear or tinted. 

---

One hour after addition of the tetracycline, the clear reaction solution was poured into 1,500 ml of chloroform. A yellow product separated and was collected on a coarse sintered glass filter and air dried. The tetracycline-metaphosphoric acid complex weighed about 10 grams, contained 7.34% of phosphorus and had a bioassay of 634 gammas per milligram. Solubility in water is 750 mg/ml. 

The glass filter funnel containing Celite was preheated using a heat gun to avoid precipitation of product in the funnel. After filtration, an additional preheated mixture of 120 mL of heptane and 30 mL of toluene was passed through the Celite using suction. A precipitate forms in the filtrate, which is redissolved by heating to reflux. 

Nitropyrene also formed when pyrene deposited on glass filter paper containing sodium nitrite was irradiated with UV light at room temperature (Ohe, 1984). This compound was reported to have formed from the reaction of pyrene with NOx in urban air from St. Louis, MO (Randahl et al., 1982). Behymer and Hites (1985) determined the effect of different substrates on the rate of photooxidation of pyrene using a rotary photoreactor. The photolytic half-lives of pyrene using silica gel, alumina, and fly ash were 21,31, and 46 h, respectively. 

Insoluble polystyrene crosslinked with divinylbenzene can easily be converted by sulfonation to a usable ion exchanger. For this purpose a mixture of 0.2 g of silver sulfate and 150 ml of concentrated sulfuric acid are heated to 80-90 °C in a 500 ml threenecked flask fitted with stirrer, reflux condenser, and thermometer. 20 g of a bead polymer of styrene and divinylbenzene (see Example 3-41) are then introduced with stirring the temperature climbs spontaneously to 100-105 °C.The mixture is maintained at 100 C for 3 h,then cooled to room temperature and allowed to stand for some hours. Next the contents of the flask are poured into a 11 conical flask that contains about 500 ml of 50% sulfuric acid. After cooling, the mixture is diluted with distilled water, and the gold-brown colored beads are filtered off on a sintered glass filter and washed copiously with water. 

When resuspending isoflavones in pure organic solvent, extra care should be taken to completely dissolve extracted isoflavones in the solvent. Solublization can be achieved by ultrasonification and providing sufficient time for the isoflavones to dissolve. Vortexing helps to release and recover isoflavones from precipitated proteins that may stick to the wall of glass vials and containers. All solvents must be of a high degree of purity. All extracted samples should be filtered to remove small particles. 

The gray-green precipitate is filtered on a glass filter and washed twice with a little 2 M nitric acid. The precipitate is then stirred mechanically at 20°C. with 2000 ml. of water containing 5 ml. of 15 M nitric acid until all the crystal blocks are dispersed, and the suspension is filtered. To the filtrate... 

Assay Dissolve about 1.5 g of sample, accurately weighed, in a mixture of 75 mL of water and 15 mL of 2 IV sulfuric acid in a 300-mL Erlenmeyer flask, and add 250 mg of zinc dust. Close the flask with a stopper containing a Bunsen valve, allow to stand at room temperature for 20 min, then filter through a sintered-glass filter crucible containing a thin layer of zinc dust, and wash the crucible and contents with 10 mL of 2 N sulfuric acid, followed by 10 mL of water. Add orthophenanthroline TS, and titrate the filtrate in the suction flask immediately with 0.1 A ceric sulfate. Perform a blank determination (see General Provisions), and make any necessary correction. Each milliliter of 0.1IV ceric sulfate is equivalent to 44.62 mg of C E FeO. ... 

Racemic ammine-hexol iodide tetrahydrate (8.25 g, 0.006 mol) is dissolved in 300 mL of 0.001 M hydrochloric acid. A solution containing sodium bis-(/i-d-tartrato)diantimonate(III) pentahydrate (4.2 g, 0.00625 mol) in 100 mL of water (this solution is acidic ) is added to the first solution. A white-brown precipitate appears immediately in the solution, but it is not the desired diastereomer. (This precipitate may contain other compounds, e.g., ( )-[Co (OH)2Co(NH3)4 3][Sb2(d-C4H20g)2]3). The desired diastereomer in the form of a pale brown crystalline powder is formed by stirring the solution at 20° for 30 min and is accompanied by disappearance of the whi -brown precipitates. The crystalline powder is collected by suction filtration and suspended again in 200 mL of cold 0.001 M hydrochloric acid. The suspension is stirred for 4-5 min. The powder is collected by suction filtration on a sintered-glass filter and is used as described in Section B without being dried completely. Therefore yield was not calculated. 

---