Concentrates: unpreserved

Aqueous products that are at greatest risk from microbial spoilage include solutions, suspensions, and emulsions for repeated oral, parenteral, or external use and include critical products such as multidose injections and eye drops. Unpreserved products without adequate antimicrobial efficacy should not be presented in containers intended for use on more than one occasion unless justified. When antimicrobial preservatives are used, their efficacy has to be demonstrated using the Ph Eur test for antimicrobial preservative efficacy. Factors to be taken into account in designing a preserved product include the nature of the preservative, its concentration in the product, the... 

Each 5-mL ampule of oral concentrate contains 100 mg cromolyn sodium, in purified water. It is an unpreserved,... 

The milk lipase system is reported to be activated by mercuric chloride. Raw milk preserved with corrosive sublimate sometimes contains a much larger concentration of free fatty acids that do unpreserved samples. Pasteurized milk preserved in a similar fashion does not show an increase in free fatty acids (Manus and Bendixen 1956). 

Some manufacturers do produce unpreserved concentrates, but such products are invariably pasteurised in the bottle and carry a warning that the contents should be refrigerated after opening and consumed within a short time-span (typically 2 weeks). 

Unfiltered and unpreserved groundwater water samples collected for total and dissolved metal analyses arrived to the laboratory in a cooler with ice three days after collection. On the fourth day after collection the laboratory filtered the samples for dissolved metal analysis and preserved all samples with nitric acid. The violation of the preservation requirements (no acid ice instead of ambient storage temperature) had a marginal effect on the concentrations of total metals as the addition of acid dissolved most of the metals that may have precipitated in the sample container. That is why the chemist accepts the total metal results, but qualifies them as estimated data. However, because improper preservation and storage have grossly compromised dissolved metal concentrations, the chemist rejects the dissolved metal results and requests that the water be resampled and reanalyzed. 

It may be necessary to differentiate between antemortem and postmortem production of alcohol in a decomposed body. Little information can be obtained from the analysis of only a single sample of blood. Samples should be taken from several different sites, as well as from the right and left chambers of the heart. These samples should each be divided into two parts, one portion being stored without a preservative and the other preserved with 1% sodium fluoride. If the unpreserved and preserved samples contain different concentrations of alcohol, this is due to the continued destruction or production of alcohol by micro-organisms in the blood. If the results of the analyses are the same, then the decomposition or production of alcohol has either not occurred or has ceased. 

It is unfortunate that standard forensic pathology textbooks still speak of the fact that glucose is converted to alcohol after death. In reality the glucose content of an unpreserved sample of blood disappears within a few hours, whereas alcohol production after death requires a minimum of several days and some bacterial presence. Samples of blood for the determination of glucose should not be stored in the normal hospital containers for blood glucose as they only provide a final concentration of 0.1% sodium fiuoride in a full tube. The use of 1% is recommended as a universal preservative. 

For the determination of suspended metals a representative volume of unpreserved sample must be filtered through a 0.45 p cellulose membrane filter. The filter containing the insoluble material is transferred to a beaker and cautiously digested with concentrated nitric acid until complete. The solution is evaporated to near dryness and either dilute hydrochloric acid or nitric acid is added depending on the instrumental technique used and/or the metal determined. The solution should be filtered and diluted to a specified volume. 

THF is available unstabilized, or stabilized with 25 ppm (typical for GC use) to 250 ppm (typical for HPLC use) butylated hydroxytoluene (BHT 2,6-di-r-butyl-p-cresol), which is added to scavenge the peroxide breakdown products of THF. Ethyl ether can be purchased unstabilized or stabilized with ethanol ( 2-3%), BHT (1-10 ppm), or a blend of ethanol, water, and BHT (1.5-3.5%, 0.2-0.5%, and 5-10 ppm, respectively). Isopropyl ether is available unstabilized or stabilized widi 0.01% hydroquinone or 5-100 ppm BHT. Dioxane is available unpreserved or with 25-1500 ppm BHT as preservative. From the above, it is important that the correct solvent be chosen for use, since most are available unstabilized or stabilized and with a range of stabilizers and stabilizer concentrations. 

Non-sterile but preserved vaginal solutions may have a shelf life of 3 years after preparatiOTi, if prepared according to a standard formula and chemically and physically stable. Once opened by the patient, such vaginal solutions can be assigned an in-use period of 6 months. A concentrate diluted by the patient should be kept only 24 h after dilution. A non-standardised preserved preparatirai should not be stored in the pharmacy because the maximal shelf Ufe of say 1 month, may be reasonably needed by the patient. A diluted concentrate may be kept for 24 h after dilution. Unpreserved n(Mi-sterile vaginal solutions may have a shelf life of maximal 2 weeks and they have to be stored in a refrigerator. 

Principle In different test preparations, different concentrations of the preservative to be tested are added to the unpreserved samples. A constant microorganism load is achieved by periodic inoculation of the test preparations. During the inoculation period, just before inoculation, samples from the individual preparations... 

Method In each case, 100 ml of the water-diluted coolant to be preserved is mixed with different concentrations of the preservative to be tested in separate preparations. An unpreserved sample serves as the growth control in each case. 

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