AS 4276.23:2016 pdf free download – Water microbiology Method 23: Soils, sediments, sludges, slurries and bio-solids-Procedures for sample preparation

AS 4276.23:2016 pdf free download – Water microbiology Method 23: Soils, sediments, sludges, slurries and bio-solids-Procedures for sample preparation.
3.11 Slum
A thin mixture of an insoluble substance with a liquid. Generally free flowing.
3.12 Soil
The top layer of the earth’s surface, consisting of rock and mineral particles mixed with
organic matter, with a range of water content up to saturated. This includes subsoils.
3.13 Subsample
A portion of the original sample that is representative of the original sample, thereby assuring equivalency in analytical measurements. This may be created by trimming, subdividing, splitting of, or discrete collection from, the original sample.
4 PRINCIPLE
Solid, semi-solid and viscous liquid (i.e. high moisture content sludge) samples are mixed as much as practicable. Subsamples as necessary are quantitatively suspended in a homogenization buffer or an enrichment medium. Sample homogenization procedures are based on whether the sample is liquid or solid. The suspension is subjected to vigorous mixing to produce a uniform homogenate by any of several methods (shaking, blending, stomaching) and pH adjusted to 7.0—7.5 or the pH of the applicable growth medium. The homogenate may then be used directly as sample material for MPN-based determinations and serially-diluted for both MPN, spread-plate and membrane filtration methods. Liquid enrichment media are the starting point for both MPN and presence/absence analyses.
For reporting of results on a dry weight basis, a subsample is dried at l03°C—105°C to constant weight for gravimetric determination of percent total solids, with the result being used to calculate the MPN or cfu (colony forming units)/g dry weight.
NOTES:
1 A 10-fold wlv dilution results from the solids homogenization process. Such dilution can reduce interference by matrix materials on growth media, including matrix-associated potentially toxic materials such as metals and antimicrohials. The impact of such interferences should be considered if homogenized sample is analysed directly without dilution; such as for liquid samples, or homogenates produced with a <10-fold concomitant dilution. 2 Sample must he homogenized in order to etkctively adjust pH. 5 REAGENTS (Sec Appendix C) 5.1 Soil extraction buffer (SEB) 5.2 I)lluents As specified in AS/NZS 4276.1. 5.3 1 N and 10 N HCI solution, as required For homogenate pH adjustment. 5.4 I N NaOH solution For homogenate pH adjustment. An adequate degree of homogenization of liquid samples should have been achieved in the initial mixing step. If not, a subsample is homogenized using stomaching or blending. The minimum subsample volume required for a liquid sample is 300 mL. Check the pH of homogenized liquid samples. Sample p1-1 shall be adjusted to 7.0—7.5 by addition of 1.0 N HCI or NaOH prior to removal of further subsamples. 8.2.3 Solid saniples (approx. 7% solids) The procedure for solid samples shall be as follows: weigh out 30 ±0.1 g of well-mixed sample into a receptacle to be used for homogenization (blender jar, stomacher bag, sample container) and add 270 mL SER. Cover or otherwise seal the sample in the container and homogenize. It may be beneficial, especially if the sample is particularly hard or dry, to allow it to soak in the SEB prior to homogenization (0.5—l.Oh). Check pH and adjust to 7.0—7.5 by addition of I N HCI or NaOH. This homogenate represents 0.1 gram wet weight sample per millilitre. 8.2.4 Direct addition to enrichment broths When well mixed sample is directly added to enrichment broths, the sample is in effect being homogenized in the broth rather than extraction buffer. The same procedural details apply except that the weight of sample added to an enrichment broth is according to the applicable method, with pro rata adjustments as necessary. The tolerance on any respective masses and volumes is ±5%. Liquid samples will have been pH adjusted prior to addition and require no pH adjustment unless a different pH is specified in the applicable method. For solid samples, adjust the pH only after the subsample is added to the enrichment broth. 8.3 p11 neutralization For non-alkaline stabilized liquid and solid samples. I N HCI or NaOH is used for pH neutralization. The procedure shall be as follows: actively mix or stir samples during pH adjustment. A sterile magnetic stir bar and a magnetic stir plate combination can be used for this activity. Add the HCI or NaOH while stirring to adjust pH to 7.0—7.5. Ensure pH is stable at 7.0—7.5 by observing for several minutes after final acid or alkali addition. Either remove a small aliquot of the sample or ethanol sterilize the pH probe (for direct sample application) before pit measurements. Calibrate p11 meter with p11 4, 7 and 10 buffers.