Sterilizers formaldehyde

Chemical disinfectants are limited in their use as air sterilants because of their irritant properties when sprayed. However, some success has been achieved with atomized propylene glycol at a concentration of 0.05-0.5 mgH and quaternary ammonium compounds (QACs) at 0.075% m be used. For areas which can be effectively sealed off for fumigation purposes, formaldehyde gas at a concentration of 1-2 mg H of air at a relative humidity of 80-90% is effective. 

Closure liners of pulpboard or cork, unless specially treated with a preservative, foil or wax coating, are often a source of mould contamination for liquid or semi-solid products. A closure with a plastic flowed-in linear is less prone to introduce or support microbial growth than one stuck in with an adhesive, particularly if the latter is based on a natural product such as casein. If required, closures can be sterilized by either formaldehyde or ethylene oxide gas. 

The British Pharmacopoeia (1993) recognizes five methods for the sterilization of pharmaceutical products. These are (i) dry heat (ii) heating in an autoclave (steam sterilization) (iii) filtration (iv) ethylene oxide gas and (v) gamma or electron radiation. In addition, other approaches involving steam and formaldehyde and ultraviolet (UV) light have evolved for use in certain situations. For each method, the possible permutations of exposure conditions are numerous, but experience and product stability... 

Formaldehyde gas for use in sterilization is produced by heating formalin (37% wA aqueous solution of formaldehyde) to a temperature of 70-75°C with steam, leading to the proeess known as LTSF. Formaldehyde has a similar toxicity to ethylene oxide and although absorption to materials appears to be lower similar desorption routines are leeommended. A major disadvantage of formaldehyde is low penetrating power and this limits the packaging materials that eanbe employed to principally paper and eotton fabrie. 

Low-temperature steam and formaldehyde Gas concentration 15-100 mgl" Steam admission to 73°C 40-180min sterilizing time depending on type of process... 

Low-temperature steam with formaldehyde is of value in the disinfection/sterilization of some heat-sensitive materials (see also Chapter 20). 

Low temperature steam and formaldehyde Reactive chemical Indicator paper impregnated with a formaldehyde-, steam- and temperature-sensitive reactive chemical which changes colour during the sterilization process Gas concentration, temperature, time (selected cycles)... 

Line S.J. Pickerell J.K. (1973) Testing a steam-formaldehyde sterilizer for gas penetration efficiency. J Clin Pathol, 26, 716-720. 

Sterilization by irradiation was introduced by mid-fifties. In about 20 years, it was fully operational. When compared with the traditional methods of sterilization such as using formaldehyde, ethylene oxide (a toxic gas), or heating in an autoclave, several advantages of irradiation may be noted (Artandi, 1977) ... 

The toxoid is then prepared by treating the active toxin produced with formaldehyde. The product is normally sold as a sterile aqueous preparation. Tetanus vaccine production follows a similar approach. Clostridium tetani is cultured in appropriate media. The toxin is recovered and inactivated by formaldehyde treatment. Again, it is usually marketed as a sterile aqueous-based product. 

Nakahari [2.11] describes, on the basis of his experience with VHP , the advantages of this process a short sterilization time at room temperature, the possibility to update existing plants, VHP does not - compared with ethylenoxide and formaldehyde - affect the health of the operators and can be decomposed to water and 02 without contaminating the atmosphere. 

Materials Required Standard chlortertracyline sterilized media (as described above) 1 L authentic and pure strain of microorganism Staphylococcus aureus (NCTC 6571) formaldehyde solution (34-37% w/v) 10 ml matched identical test tubes 20 ... 

Formaldehyde and glutaraldehyde are used for disinfection or sterilization of instruments such as fiberoptic endoscopes, respiratory therapy equipment, hemodialyzers, and dental handpieces that cannot withstand exposure to the high temperatures of steam sterilization. They are not corrosive for metal, plastic, or rubber. These agents have a broad spectrum of activity against microorganisms and viruses. They act by alkylation of chemical groups in proteins and nucleic acids. Failures of disinfection or steri... 

Alkylating agents Disrupt structures of proteins and nucleic acid Formaldehyde is used to inactivate viruses without destroying antigenic properties, glutaraldehyde is used to sterilize equipment, betapropiolactone is used to destroy hepatitis viruses, and ethylene oxide to sterilize objects that would be harmed by elevated temperatures... 

Chemical (vapor phase) Ethylene oxide Propylene oxide Formaldehyde (3 - Propiolactone Disinfection temperature Ethylene oxide also used as sterilizing agent Possible carcinogenic activity of p-propiolactone... 

Sterilization of a membrane system is also required to control bacterial growth. For cellulose acetate membranes, chlorination of the feed water is sufficient to control bacteria. Feed water to polyamide or interfacial composite membranes need not be sterile, because these membranes are usually fairly resistant to biological attack. Periodic shock disinfection using formaldehyde, peroxide or peracetic acid solutions as part of a regular cleaning schedule is usually enough to prevent biofouling. 

RNAs are denatured by formaldehyde/heat treatment. All of the stock solutions for RNA slot blots are made using sterile diethyl pyrocarbonate (DEPC)-treated water. RNAs are diluted as necessary from stock solutions with water, and 3 volumes of 6.15 Mformaldehyde in 10X standard saline citrate (SSC) is added to give a final RNA concentration of 10-100pg/ml. The RNA dilutions are heated to 65° for 15 min and quick-chilled on ice. The denatured stock is further diluted with 4.16 M formaldehyde in 7.5 X SSC such that the desired concentration of RNA may be applied to each slot in a total volume of 400 pi. The nylon membrane is piewet in water and then soaked in 10X SSC for 20 min. Slot blots are performed using a commercially available apparatus hooked to a vacuum source. After the samples are blotted through, each well is washed with 400 pi of 10 X SSC. The membrane is removed from the apparatus and baked in a vacuum oven at 80° for 2 hr. 

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