Basic Filtration Items

Posted by: Dat

WHEATEN or PYREX Glass Media Bottles

Sterilize them with dry heat in the oven using established guidelines w/ tinfoil covering the opening. (NOTE: See next post for Dry Heat Sterilization of glassware)

NOTE: The media bottles Wheaton versus Pyrex will vary by neck size (33mm or 45mm). The neck size needs to be matched up with the proper size caps (either 33mm or a reusable combo of 45mm and disposable septa insert). These two items need to be matched up w/ a sterile filter which will fit the neck size. So glass media bottle, cap and filter need to be matched by the neck size.

Dry Heat Sterlization

Steam sterilization uses pressurized steam at 121-132° C (250-270° F) for 30 or 40 minutes. This type of heat kills all microbial cells including spores, which are normally heat resistant. In order to accomplish the same effect with dry heat in an oven, the temperature needs to be increased to 160-170° C (320-338° F) for periods of 2 to 4 hours. 5

A table of most studies conducted up to 1961 indicates that they are in enough of an agreement to support the above statements from the Berkley Lab Manual indicating that 170° C (338° F) for at least 2 hours is sufficient to sterilize objects.6 (See table below)

Using more current references such as the Dental Technician Manual, Volume 1 form the U.S. Navy we find that for sterilization of metal instruments "a typical dry heat cycle is 90 minutes at 320-345°F, plus the time required to preheat the chamber." A current microbiology text book states that "the standard settings for a hot air oven sterilization are the preheat time plus 1.5 to 2 hours at 160 °C (320 °F)."7

Based on the conformity in scientific research and medical statements we should feel comfortable relying on the following information from EngenderHealth (a leading international health organization working in third world countries).
* Sterilizing by dry heat (i.e. oven). From: EngenderHealth

The temps and times to sterilize:

Place instruments and other items in the oven, and heat to the designated temperature. The oven must have a thermometer or temperature gauge to make sure the designated temperature is reached.

Use the list here to determine the appropriate amount of time to sterilize instruments and other items for different temperatures. (do not begin timing until the oven reaches the desired temperature, and do not open the oven door or add or remove any items). The times shown here represent the amount of time that items must be kept at the desired temperature to ensure that sterilization is achieved. Keep in mind that the total cycle time--including heating the oven to the correct temperature, sterilization, and cooling--is usually twice as long as the time noted here.

Temperature
170 degrees C (340 degrees F) - 1 hour
160 degrees C (320 degrees F) - 2 hours
150 degrees C (300 degrees F) - 2.5 hours
140 degrees C (285 degrees F) - 3 hour

I suggest that as long as your glassware is capable, that the highest temperature (170 degrees C (340 degrees F) ) be used for twice the stated time... making the safe time 2 hours.
REFERENCES

1 - Development of a Multidose Formulation for a Humanized Monoclonal Antibody Using Experimental Design Techniques, Supriya Gupta, AAPS PharmSci 2003; 5 (2) Article 8
2 - A Contribution to our Knowledge of Disinfectant Action. III. Unsaturated Compounds as Germicides, H. D. Cheeseworth, E. A. Cooper, J. Phys. Chem., 1929, 33 (5), pp 720–728
3 - The veterinary formulary By Yolande M. Bishop, British Veterinary Association Pharmaceutical Press; 6 edition (October 30, 2004) page 359
4 - Disinfection, sterilization, and preservation By Seymour Stanton Block, Lippincott Williams & Wilkins; Fifth Edition edition (December 15, 2000)
5 - Biosafety Manual, Berkley National Laboratory http://www.lbl.gov/ehs/biosafety/Bio...lization.shtml
6 - Sterilization by dry heat, E. M. Darmady, K. E. A. Hughes, J. D. Jones, D. Prince, and Winifred Tuke, J Clin Pathol 1961; 14: 38-44
7 - Textbook of Microbiology by Ananthanarayan and Panikar, Orient Longman; 7Rev Ed edition (December 6, 2006)

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Benzyl alcohol (BA) as a disinfectant

Implements of sanitation for home brewing injectables

Benzyl alcohol (BA)

Benzyl alcohol (BA) is used as a bacteriostatic preservative at low concentration in intravenous medications. It exhibits low toxicity in low concentrations. The FDA has approved a medication with 5% Benzyl alcohol so a 5% concentration is our standard for the term "low concentration".

As a bacteriostatic preservative BA prevents bacteria from multiplying. However its preservative activity is pH specific and is only effective in solutions with a pH range of 4 - 7. 1

In addition, due to its polarity BA is an adequate solvent (capable of dissolving another solid).

Although it is not widely known BA is a disinfectant. 2 This means it is capable of destroy microorganisms. It is not a perfect disinfectant. However it is listed in the British Veterinary Association's veterinary formulary as being a capable disinfectant, with an indicated useage "Cleaning and disinfection of teats" with the further usage defined as "Post milking teat dip 4% Benzyl Alcohol for cattle, use undiluted." 3

Because of BA's antibacterial and weak local anesthetic properties the British Pharmacopoeia recommends that a 1% concentration be used in injectable medicines.4

At higher concentrations BA may contribute to the degradation of proteins in the form of aggregation (increasing the clinging of the protein chain to surfaces making them susceptible to breakage or change in 3-dimensional structure).1 This happens frequently in the reconstitution of IGF-1 LR3 and in the Supriya Gupta study occurred at concentrations greater than 1%.

In the same Supriya Gupta study BA was tested against other preservatives for effectiveness at killing mircrobes.
Preservative Screening Test (Bactericidal/Fungicidal Activity) 1

The efficacy of the preservative against various microorganisms was measured using a modified USP/EP PET (referred to as preservative screening test in this document)... In the procedure, formulations were tested against the following microorganisms: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger. The 3 bacterial strains were inoculated together at a total concentration of ~105 cfu/mL, as were the 2 fungi. Samples were incubated for 7 days at room temperature (25°C), and the total bacterial and fungal counts were measured using a colony counter. The log reduction (LR) values for the bacterial and fungal counts were calculated as log (initial count/final count).
...

Results of the preservative screening tests showed that the formulations containing 0.75% and 0.5% benzyl alcohol are potential candidates to meet the USP/EP criteria (Table 4). Both formulations demonstrated a complete kill of the tested bacterial and fungal species after 7 days.

...
Benzyl alcohol caused significant aggregation at high concentrations (>=1.0%); however, it was the most effective preservative in maintaining antimicrobial efficacy against bacteria and fungi.

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