2.1: Sampling Information – handling requirements and preservation

This information sheet gives information on general handling requirements in sampling for chemical, physical, radiological and microbial characteristics.

Sampling for chemical, physical and radiological characteristics

Table IS2.1.1 provides general advice on the handling requirements for chemical, physical and radiological characteristics, based on Australia Standard AS/NZS 5667.1:1998 Water Quality – Sampling Part 1: Guidance on the design of sampling programs, sampling techniques and the preservation and handling of samples. To ensure that samples are collected and transported in an appropriate manner, advice of an analyst should be sought before taking a sample.

Metal Fractions

Metals can be divided into various fractions as determined by the analytical information:

• filterable metals (soluble or dissolved, macromolecular and colloidal metals) – those constituents of an unacidified sample that pass a 0.45μm membrane filter;

• suspended metals – those constituents of an unacidified sample that are retained on a 0.45μm membrane filter;

• total metals – the concentration of metals determined on an unfiltered sample after vigorous digestion, or the sum of the concentrations of metals in both the filterable and suspended fractions. Total metals include all metals inorganically and organically bound, both filterable and particulate;

• acid-extractable metals – the concentration of metals in solution after treatment of an unfiltered sample with hot mineral acid;

• readily acid-soluble aluminium – see Fact Sheet on Aluminium.

The fraction(s) to be analysed will determine the requirements for sample handling and preservation. It is generally advisable to collect two samples, one for total metals and one for dissolved metals.

Sampling for microbial characteristics

As per Australian Standard AS/NZS 2031:2012 – Selection of containers and preservation of water samples for microbiological analysis, when sampling for microbial characteristics the following dot points must be taken into consideration:

• The sample container used to collect the sample must be sterile.

• Sufficient sodium thiosulfate should be added to the sterile sample container to neutralise all residual chlorine.

• When collecting water samples that may contain concentrations of heavy metals that may be toxic to bacteria, addition of EDTA to the sample containers is recommended.

• The size of the container used depends upon the number and type of tests to be carried out, but the containers must be of sufficient volume for the all the tests required, with adequate head space to allow for sample mixing.

• All samples should be refrigerated or chilled in ice coolers during transport.

Drinking water samples should be taken directly from a service pipe, or a dedicated sampling point, not from an intermediate tank or cistern. As described in AS/NZS 5667.5:1998 Water Quality – Sampling Part 5: Guidance on sampling of drinking water and water used for food and beverage processing, sampling taps should be sterilised by flame or alternative methods of equivalent efficacy, for example soaking in chlorine solution, and should be maintained in good order. The water discharged by flushing should be able to run off freely.

On days of total fire ban, where sterilisation by flame is not possible, an alternative method of equivalent efficacy should be used.

Samples should be analysed within six hours of collection. If this is not possible, then the samples must be transported and stored at between 2°C and 10°C. Samples must not be frozen.

Where logistics do not allow examination within six hours, storage may be prolonged and samples may be examined up to 24 hours after collection, provided that they are kept cool (between 2°C and 10°C) and in the dark.

As noted in AS/NZS 2031:2012, if samples are to be analysed for free-living protozoans, including amoebae, the samples should not be refrigerated during transport and storage, but should be held at ambient temperature, preferably near 20°C, but the sample temperature should not exceed 30°C.

Further advice on appropriate sampling technique can be found in Australian Standards AS/NZS 5667.1:1998 and AS/NZS 5667.5:1998.

Table IS2.1.1 Special handling requirements in sampling for chemical, physical and radiological characteristics (data compiled from AS/NZS 5667.1:1998)

Characteristic	Container	Minimum sample size (mL)	Preservation procedure	Maximum holding period	Comments
Aluminium	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Arsenic	P(A), G(A)	500	Add $\text{HNO}_3$ to pH <2	28 days
Boron	P	100	None required	28 days	Fill container completely to exclude air
Cadmium	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Chloride	P, G	100	None required	28 days
Chlorine residual	P, G	500	Analyse immediately	5 minutes	Keep sample out of direct sunlight
Chromium (total)	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Chromium (VI)	P(A), G(A)	100	Refrigerate	24 hours	Sample container should be thoroughly rinsed. Avoid adding reagents
Colour	P, G	500	Refrigerate and store in the dark	2 days
Copper	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Cyanide	P, G	500	Add NaOH to pH >12. Refrigerate in the dark	24 hours	Remove sulfide
Fluoride	P	200	None required	28 days	PTFE containers are not suitable
Hardness	P	100	None required	7 days	Fill container completely to exclude air
			Add HNO₃ to pH <2	28 days	Fill container completely to exclude air. Acidification permits the determination of calcium and other metals from the same sample
Iron	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Lead	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Manganese	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Mercury	G(A)	500	Add $\text{HNO}_3$ to unfiltered sample to pH <1. Add $\text{K}_2\text{Cr}_2\text{O}_3$	28 days	Consult analyst for further instruction
Metals (general)	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Metals (filterable)	P(A), G(A)	100	Filter immediately, add $\text{HNO}_3$ to pH <2	28 days	0.45 m filter
Nitrate	P, G	500	Refrigerate	24 hours	Unfiltered samples
			Filter on site (0.45 m cellulose acetate membrane filter) and freeze	1 month	Consult analyst – depends on analytical method
Odour	P, G	500	Refrigerate	6 hours	Analyse as soon as possible
Oxygen, dissolved	P or G	300	None required	Determine in the field	Avoid excessive turbulence, to minimise oxygen entrainment
	G		Winkler acidification	24 hours	Store in dark
Pesticides (organochlorine, organophosphorous, and nitrogen-containing)	G(S)	1000 to 3000	Refrigerate [1]	7 days	Extract on site where practical. Consult with analyst
pH	P, G	100	Refrigerate	6 hours
Poly aromatic hydrocarbons (PAHs)	G(S)	1000	Refrigerate and store in dark [1]	7 days	Extract on site where practical. Consult with analyst
Radioactivity gross alpha and beta activity	P, G	1000	Add $\text{HNO}_3$ to pH <2	28 days	Fill container completely to exclude air. Consult with analyst
Selenium	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days
Sodium	P	100	None required	28 days
Sulfate	P, G	200	Refrigerate	7 days
Taste	G	500	None required	24 hours	Analyse as soon as possible
Temperature	-	-	None required	Analyse immediately	Determine in situ
Total dissolved solids	P, G	500	Refrigerate	24 hours	Fill container completely to exclude air
Trihalomethanes	G, vials with PTFE-faced septum	100	Add 2 mL of 5% ascorbic acid solution	14 days	Fill container completely to exclude air
Turbidity	P, G	100	None required	24 hours	Preferably determine on site or in situ
Zinc	P(A), G(A)	100	Add $\text{HNO}_3$ to pH <2	28 days

\begin{array}{lll} \text{Container} & \text{P} & \text{= Plastic (polyethylene or equivalent)} \\ & \text{G} & \text{= Glass} \\ & \text{G(B)} & \text{= Glass, borosilicate} \\ & \text{P(A), G(A)} & \text{= Rinsed with 50% HNO}_3 \\ & \text{G(S)} & \text{= Glass, rinsed with organic solvent, PTFE cap liner} \\ & \text{PTFE} & \text{= Polytetrafluoroethylene} \\ \text{Preservation} & \text{Refrigerate} & \text{= Store between 1° and 4°C in the dark, do not freeze} \\ & \text{HNO}_3 & \text{= Nitric acid (hydrochloric acid may be used in this context but nitric acid is preferred)} \\ & \text{NaOH} & \text{= Sodium hydroxide solution (40% w/v)} \\ & \text{K}_2\text{Cr}_2\text{O}_3 & \text{= Potassium dichromate} \\ \end{array}

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Footnotes

1. If a sample is chlorinated, for each 1000 mL of sample add 80 mg of sodium thiosulfate to container prior to sample collection.