Neutral glasses

The neutral glasses are generally less resistant than the hard borosilicate type, but are more easily melted and shaped. They are formulated so that the pH of aqueous solutions is unaffected by contact with the glass, making it particularly suitable in pharmaceutical use for the storage of pH-sensitive drugs. 

Richardson NA, Gu J, Wang S, Xie Y, Schaefer HF III (2004) DNA nucleosides and their radical anions molecular structures and electron affinities. J Am Chem Soc 126 4404-4411 Riederer FI, Fluttermann J (1982) Matrix isolation of free radicals from 5-halouracils. 3. Electron spin resonance of base oxidation in aqueous acidic glasses. J Phys Chem 86 3454-3463 Riederer FI, Fluttermann J, Symons MCR (1978) cr -Electron addition to 5-halogenouracils in neutral glasses. J Chem Soc Chem Commun 313-314... 

It is important that the container is made of material that will not interact, either physically or chemically, with the essential oil. For the quantities handled by the aromatherapist, neutral glass is the best choice. Suppliers will use metal containers for larger quantities. Aluminium with an internally lacquered surface would be suitable for amounts up to 10 kg, while internally lacquered steel drums would be appropriate for amounts above... 

EP describes Type I glass as neutral glass with high hydrolytic resistance owing to the chemical composition of the glass itself. Type I is suitable for all preparations whether or not for parenteral use and for human blood and blood components. ... 

Nackrite, 33 Nepheline, 45, 370 Nepheifne-syenite, 45 Nernst mass, 340 Network former, 59, 62 Network modifier, 59, 62 Neutral glass, 60, 203 Newtonian liquid, 64, 251 Nitrides, 344—346 Non-stoichiometry, ofSi02, 17 ofTiO, 21 Nucleation,... 

BECONASE GlaxoSmithKline (U.S./UK) Beclomethasone dipropionate 0.042% (micronised) SAI, Mr = 521 BKC, MCC, NaCMC, dex, Tw80, PE-OH (0.25% w/v), HCI, (pH 4.5-70) Amber neutral glass bottle with metering atomising pump and nasal adapter... 

Attachment to Amino Group. The electron reacts with the protonated terminal amino group in aliphatic amino acids, leading to deamination (53,58). The rate constants in solution depend on pH, k decreasing as pH is increased. ESR studies on electron reaction with amino acids in neutral glasses at —196 °C indicate that dissociative attachment readily occurs producing a fatty acid radical ... 

Neutral glass is normally specified when injectable products are involved. Tubular glass neutrality may be affected by the supplier s forming conditions (too hot, too slow, etc.) and chemical testing, to pharmaceutical standards, is a prerequisite of QC acceptance. Failure must result in rejection, with possible supplier treatment (sulphating) to bring the components into specification. (Note that this is only possible with some products in some markets.)... 

In certain instances the use of neutral glass becomes essential—ordinary insulin was quoted as a prime example where pH control is critical. Neutral glass is far more resistant to chemical attack. Treated neutral glass is also available. 

Cane for tubular glassware may be made by one of two processes—Danner and Velio. Danner was the earlier process but is not detailed here, since it has been largely replaced by the faster Velio system. Both can produce cane in soda or neutral glass. 

Tubular glass containers are made in neutral type I, surface treated type I glass, soda glass, etc., and may also be siliconised as a separate process after manufacture. Surface treated type I glass is occasionally necessary in smaller containers, where now and then a sample fails the neutral glass test. 

These are employed to check the alkalinity extractives. The pharmacopoeial tests may be based upon surface extraction tests (i.e. type II surface treated glass) or crushed glass where the glass composition is checked (type I neutral glass). 

One suggested accelerated test is to place an excess of cut-up pieces of the proposed plastic, immersed in the product, in a neutral glass stoppered container which is held at, say, 4°C, 25°C, 40°C for a period of 3 months. The product (and plastic) should be analysed at intervals for change and extraction. However, even a test of this nature is not all-embracing since total immersion eliminates possible change from air to air-liquid interfaces which occur in a pratical situation. 

The temperature of the melt has to be high enough to provide first, a reasonable quartz dissolution rate in the molten bath and second, a manageable low melt viscosity. The latter also depends on the chosen silica to alkali ratio. Fusion temperatures of 1300-1400°C for alkaline glass and 1400-1500°C for neutral glass are common (see Table 22.1). Carbon dioxide is driven off by the reaction of alkali carbonate with silica. The main part of carbon dioxide is liberated at 700°C [1,5-7,11,12,14,15,18-21]. 

For candidate WHO standards, 5 ml, type I neutral glass, DIN ampoules are used for freeze-drying, fitted with a two part capillary labyrinth to reduce the rate of air/moisture ingress as the ampoules await sealing and to facilitate effective glass fusion, as previously described. 

Water for injections is prepared according to the Ph. Eur. by distillation of potable or purified water from a device of neutral glass, quartz or a suitable metal. The device must be fitted with an anti-splashing device to prevent contamination of distilled water with non-distilled water. 

Neutral glass, which in principle is suitable for reuse, is being eroded/impaired by borax containing solutions (pH around 9) [14]. This demonstrates that even neutral glass will be impaired by solutions with pH >7. Therefore neutral glass bottles should be used only once for autoclaving solutions with pH >7. Plastic containers are probably more suitable for these solutions. 

I. Neutral glass or borosilicate glass with high hydrolytic resistance due to the chemical composition of the glass itself... 

The Ph. Eur. specifies that water for injections in bulk is obtained from water that complies with the regulations for water intended for human consumption or from purified water by distillation in an apparatus of which the parts in contact with the water are of neutral glass, quartz or a suitable metal and which is fitted with an effective device to prevent the entrainment of droplets. So the quality of this water is essentially defined by the very specific way it is produced. The reason for this is that there is no reference water quality to compare. 

Fiolax , clear (blue identification line), neutral, glass tubing (chemically highly resistant) for pharmaceutical... 

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