Membrane-filter Rinse Fluid (USP)

Membrane Filter Rinse Fluid

EMD Cat. No. 1.05286.0500

500 g

The broth is used as a rinsing fluid in the membrane filtration procedure.

This medium largely complies with the formulation prescribed in the recommendations of the United States Pharmacopeia XXIII (1995).

Mode of Action	Preparation
Experimental Procedure and Evaluation	Quality Control
Typical Composition (g/liter)	Literature

Mode of Action
After filtration it is often necessary to rinse the membrane filter in order to remove residues of liquid sample materials. If the sample contains higher hydrocarbons such as vaseline, paraffin, etc. or fats, the use of rinse fluid is recommended.
This fluid contains balanced concentrations of nutrients which prevent the microorganisms, retained by the filter, from being exposed to physiological shock, thus being capable to grow further rapidly. The detergent polysorbate 80 ensures emulsification of carbohydrates and fats without seriously affecting the microorganisms. If the sample contains large quantities of these compounds, additional up to 9.0 g/liter of polysorbate 80 (Tween^® 80) can be added in accordance with the USP recommendations before the broth is filtered.

Typical Composition (g/liter)
Peptone from meat 5.0; meat extract 3.0; polysorbate 80 1.0.

Preparation
Suspend 9 g in 1 liter of purified water, if desired together with up to 9 g/liter of polysorbate 80 (Tween^® 80), filter until clear, autoclave (15 min at 121 °C).
pH: 6.9 ± 0.2 at 25°C.
The broth is clear and yellow.

Experimental Procedure and Evaluation
After filtering the liquid sample, rinse the filter 3 times with 100 ml portions of the membrane-filter rinse fluid, then complete the test in the usual way.
Incubation for 24 hours at 35°C aerobically.

Quality control (streaked on Standard I Nutrient Agar 1.07881.)

Test strains	Growth
Staphylococcus aureus ATCC 25923	good
Streptococcus pyogenes ATCC 12344	good
Enterococcus faecalis ATCC 11700	good
Escherichia coli ATCC 25922	good
Citrobacter freundii ATCC 8090	good
Pseudomonas aeruginosa ATCC 27853	good

Additives

EMD Cat. No.	Product	Pack Size
PX1291-1	Tween^® 80	500 ml

Literature

United States Pharmacopeia XXIII, Chapter "Microbial Limit Tests", 1995.