Here's my report! :)) Number: 8
SURFACE TENSION
Surface tension is a result of the cohesive forces among the particles of a liquid. It is the tendency of the surface of a liquid to contract to the smallest possible area. The force pulling the surface particles into the liquid causes the surface to become as small as possible which is a sphere (the geometrical figure that has the least surface area for a given volume); hence, when free to do so liquids assume a spherical shape.
Beneath the surface, each molecule is attracted equally in every direction by neighboring molecules, resulting in no tendency to be pulled in any specific direction; hence there is zero net force. A molecule on the surface of a liquid, however, is not attracted equally in all directions because it is pulled only by neighboring molecules on each side and downward from below; there is no pull upward. Because there are no molecules above it to exert upward forces, the molecules are being pulled toward the interior of the liquid. The surface behaves as if it were tightened into an elastic film. This is evident when dry steel needles or razor blades seem to float on water. They don’t float in the usual sense but they are supported by the surface molecules opposing an increase in surface area.
Surface tension is the force per unit length needed to hold the surface together. The force is tangent to the liquid surface and is caused by the mutual attraction of the surface molecules to teach other and to other molecules below the surface. Note that surface tension decreases with increase in temperature, becoming zero at the critical temperature.
SURFACE TENSION à ɣ = F/l
| Surface Tension for Various Liquids | ||
| LIQUID | T(C°) | Surface Tension (N/m) |
| Mercury | 20 | 0.465 |
| Soapy water | 20 | 0.025 |
| Water | 20 | 0.0728 |
| Water | 60 | 0.0662 |
| Water | 100 | 0.0589 |
| Ethyl alcohol | 20 | 0.22 |
| Methyl alcohol | 20 | 0.0226 |
| Acetone | 20 | 0.0237 |
| Glycerol | 20 | 0.0634 |
| Benzene | 20 | 0.0289 |
Liquid surface tension is important in the fabric and cleansing industries. Disinfectants often are solutions of low surface tension. Surface tension also plays a great role in pharmaceutical liquid preparations.
STERILITY TESTING
Sterility testing is a very exacting procedure, where asepsis of the procedure must be ensured for a correct interpretation of results. The test for sterility is carried out under aseptic conditions. In order to achieve such conditions, the test environment has to be adapted to the way in which the sterility test is performed. The precautions taken to avoid contamination are such that they do not affect any microorganisms that are to be revealed in the test.
Pharmacopeial articles are to be tested by the Membrane Filtration method where the nature of the product permits; that is, for filterable aqueous preparations for alcoholic or oily preparations and for preparations miscible with, or soluble in, aqueous or oily solvents, provided these solvents do not have an antimicrobial effect in the conditions of the test. If the membrane filtration is unsuitable, Direct Inoculation of the Culture Medium method may be used.
The USP provides two basic methods for sterility testing. One involves the direct introduction of product test samples into culture media; the second involves filtering test samples through membrane filters, washing the filters with fluids to remove inhibitory properties, and transferring the membrane aseptically to appropriate culture media.
Internationally recognized experts and bodies now recommend the use of two culture media suitable for the test for sterility:
Ø Fluid Thioglycollate Medium (incubated at 20° to 25° C) is primarily intended for the culture of anaerobic bacteria but it will also detect aerobic bacteria.
Ø Soybean-Casein Digest Medium is suitable for the culture of both fungi and aerobic bacteria.
The preferred method for verifying sterility is not by testing sterilized materials but by the use of biological indicators. This is not possible, however, when products are sterilized by filtration and filled aseptically into their final containers (i.e. antibiotics, insulin or hormones)
The Use of Isolator Systems for Use in Sterility Testing of Compendial Articles
Isolators are devices that create controlled environments in which to conduct Pharmacopeial sterility tests. This is driven by the same need to minimize human intervention and thus increase dramatically the assurance of sterility. It is either sealed or supplied with air through a microbial retentive filter and is able to be reproducibly sterilized.
Isolator systems protect the test article and supplies from contamination during handling by essentially eliminating direct contact between the analyst and the test articles. Aseptic manipulations within the isolator are made with half-suits, which are flexible components of the isolator wall that allow the operator a full range of motion within the isolator, or by gloves and sleeves. The interior of the isolator is treated with sporicidal chemicals that result in the elimination of all viable burdens.
The isolator system must be validated before its use in sterility testing as a part of a batch release procedure. To verify that the isolator system and all associated equipment are suitable for sterility tests, validation studies are performed in three phase:
1. Installation Qualification
2. Operational Qualification
3. Performance Qualification
Observation and Interpretation of Results
If no evidence of microbial growth is found, the product to be examined complies with the test for sterility. If evidence of microbial growth is found, the product to be examined does not comply with the test for sterility, unless it can be clearly demonstrated that the test was invalid for causes unrelated to the product to be examined. The test may be considered invalid only if one or more of the following conditions are fulfilled:
a. The data of the microbiological monitoring of the sterility testing facility show a fault.
b. A review of the testing procedure used during the test in question reveals a fault.
c. Microbial growth is found in the negative controls.
d. After determination of the identity of the microorganisms isolated from the test, the growth of this species may be ascribed unequivocally to faults with respect to the material and or the technique used in conducting the sterility test procedures.
If the test is declared to be invalid, it is repeated with the same number of units as in the original test. If no evidence of microbial growth is found in the repeat test, the product examined complies with the test for sterility. If microbial growth is found in the repeat test, the product examined does not comply with the test for sterility.
However, government standards for Sterility Assurance Levels (SAL) basically eliminated the possibility to repeat sterility tests. This means that batches that fail for any reason cannot be released. They are only useful for investigation of potential contamination hazards.
STORAGE CONDITION
Storage condition is the prevailing specified temperature, humidity and other environmental factors within which a range will insure optimal stability based on experimental evidence of the product.
FREEZER – A place in which the temperature is maintained thermostatically between -25° and -10° (-13° and 14°F)
COLD – Any temperature not exceeding 8° (46° F).
REFRIGIRATOR is a cold place in which the temperature is maintained thermostatically between 2° and 8° (36° and 46° F)
COOL – Any temperature between 8° and 15° (46° and 59° F).
ROOM TEMPERATURE – The temperature prevailing in a working area.
CONTROLLED ROOM TEMPERATURE – A temperature maintained thermostatically that encompasses the usual and customary working environment of 20° to 25° (68° to 77° F).
WARM – Any temperature between 30° and 40° (86° to 104° F)
EXCESSIVE HEAT – Any temperature above 40° (104° F)
PROTECTION FROM FREEZING – Where freezing subjects an article to loss of strength or potency, or to destructive alteration of its characteristics, in addition to the risk of breakage of the container
DRY PLACE – a place that does not exceed 40% average relative humidity at Controlled Room Temperature or the equivalent water vapor pressure at other temperatures. Storage in a container validated to protect the article from moisture vapor, including storage in bulk, is considered a dry place.
Storage under Nonspecific Conditions - Where no specific directions or limitations are provided in the Packaging and storage section of individual monographs or in the article’s labeling, the conditions of storage shall include storage at controlled room temperatures, protection from moisture, and , where necessary, protection form light.
Note that, for those instances where, for some reason, storage information is not yet found in the Packaging and storage specification of a monograph, the section Storage under Nonspecific Conditions serve as interim guidance. The Storage under Nonspecific Conditions statement is not meant to substitute for the inclusion of proper, specific storage information in the Packaging and storage statement of any monograph.
TEMPERATURE PROFILES – are observations of temperature variations over a period of time compiled by using a suitable number of thermometers or other temperature recording instruments placed throughout the storage area in divided sections. It should record the maximum and minimum temperatures during a 24-hour period for a total of three consecutive 24-hour periods. This can be used to establish suitable areas for storing Pharmacopeial articles designated to be stored in their specific conditions.
The following factors should be considered during the process of temperature profiling:
a. size of space
b. location of space heaters
c. sun-facing walls
d. low ceilings or roofs
e. geographic location of the area
The temperature profile should provide recommendations for the use of each area and identification of any areas that are found unsuitable for storage of Pharmacopeial articles.
