ISO 11348-3 Water Quality - Luminescent Bacteria Testing - Part 3: Test Method Using Freeze-Dried Bacteria

Chemical Tests

ISO 11348-3 Water Quality - Luminescent Bacteria Testing - Part 3: Test Method Using Freeze-Dried Bacteria

This part of the ISO 11348 standard developed by the International Standards Organization (ISO) describes three methods for determining the inhibition of luminescence emitted by the marine bacterium Vibrio fischeri (NRRL B‑11177). ISO 11348-3 specifies a method using freeze-dried bacteria.

ISO 11348-3 Water Quality - Luminescent Bacteria Testing - Part 3: Test Method Using Freeze-Dried Bacteria

This method applies to:

  • Waste water;
  • Aqueous extracts and leachates;
  • Fresh water (surface and groundwater);
  • Sea and brackish water;
  • Sediment eluates (fresh water, brackish water and sea water);
  • pore water;
  • Single substances diluted in water.

Persons using this part of ISO 11348 should be familiar with normal laboratory practices. This standard does not purport to address all safety issues, if any, associated with its use. It is the user's responsibility to establish appropriate safety and health practices and to ensure compliance with any national regulatory requirements.

Measurements specified in ISO 11348 can be performed using freshly prepared bacteria as well as freeze-dried or liquid-dried bacterial preparations. Standardized studies by DIN Normenausschuss Wasserwesen and ISO/TC 147/SC 5/WG 1 show that in special cases these different techniques may yield different results, especially in the presence of heavy metals.
has shown.

Such varying sensitivity is due to differences in the composition of the media used in the preparation of freeze-dried or liquid-dried bacteria. These protective environments may affect the bioavailability of toxic substances and/or
affect the light emission of luminescent bacteria. This means that the origin and type of preparation must be considered when interpreting the results. Freeze-dried and liquid-dried bacteria from different suppliers
This can be difficult at times. This may mean that the composition is not known in detail and therefore cannot be interpreted by the user.

Therefore, in addition to the toxicity measurements with liquid dried bacteria (ISO 11348-2) and freshly prepared bacteria (ISO 11348-1), this section of ISO 11348 describes a procedure with freeze-dried bacteria. It can be interpreted in every detail by the user. The laboratories responsible for the results have the opportunity to choose the most appropriate technique based on their expert opinion and knowledge of the water sample to be tested.

Inhibition of light emission by Vibrio fischeri cultures is determined by a batch test. This is accomplished by combining certain volumes of the test sample or diluted sample with a luminescent bacterial suspension in a test tube.

The test criterion is luminescence, measured after a contact time of 15 minutes or 30 minutes and optionally 5 minutes, taking into account a correction factor (fkt), which is a measure of the intensity changes of control samples over the exposure time. The inhibitory effect of the water sample can be determined by means of a dilution series as LID (see Annex B) or EC20- and/or EC50-values.

Insoluble, poorly soluble or volatile substances or substances that react with dilution water or suspension or change their state during the test period may affect the result or impair the reproducibility of test results.

In strongly colored or turbid waters, luminescence losses from light absorption or light scattering may occur. This interference can be compensated for by a sample treatment for turbidity or, for example, by using a dual chamber absorption correction test tube.

Since oxygen is required for bioluminescence, samples with a high oxygen demand (and/or low oxygen concentration) can cause oxygen deficiency and be inhibitory. Easily biodegradable nutrients in the sample can cause a contaminant-independent reduction in bioluminescence.

Among the services provided by our organization within the framework of material testing services, there are also ISO 11348-3 standard tests. Do not hesitate to contact our laboratory EUROLAB for your testing and certification requests.

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