Part IV draft information sheets sampling Information – handling requirements and preservation Information Sheet 1




НазваниеPart IV draft information sheets sampling Information – handling requirements and preservation Information Sheet 1
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PART IV DRAFT INFORMATION SHEETS






Sampling Information – handling requirements and preservation
Information Sheet 2.1


This sheet gives information on general handling requirements in sampling for heavy metals, filterable metals, organic compounds and pesticides and microbial characteristics; and it summarises the special handling requirements in sampling for physical, chemical and radiological characteristics.

Sampling for heavy metals


Treating the sample with acid at the time of collection places the metals in solution and prevents adsorption or deposition on the container walls. 1.5 mL of concentrated nitric acid per litre of sample is usually sufficient for short-term preservation. The sample should be stored at approximately 4ºC. It will be stable for up to 28 days.

Some laboratories will supply acid-washed bottles with the acid preservative. When such bottles are not available, samples should be collected in acid-washed bottles, and preserved immediately by acidifying with concentrated nitric acid to pH <2. The advice of the analyst should be sought before taking a sample.

Mercury and chromium have special requirements. An analyst should be consulted before collection of samples.

The procedure for acid washing is as follows:

1. Wash bottle and cap with a metal-free, non-ionic detergent and tap water.

2. Rinse thoroughly with tap water.

3. Rinse with one part distilled water, one part concentrated nitric acid.

4. Drain and fill with one part concentrated nitric acid, fourteen parts water.

5. Cap and store until required, but for at least a week.

6. Empty before use, rinse with metal-free water such as distilled water.

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

  • Filterable metals (soluble or dissolved metals) – those constituents of an unacidified sample that pass a 0.45 μm membrane filter;

  • Suspended metals – those constituents of an unacidified sample that are retained on a 0.45 μm 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 – 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.

Preliminary filtration for filterable metals



The membrane filter and filter device should be preconditioned by rinsing with deionised or distilled water, or soaking the membrane filter and filter device in approximately one part distilled water, one part nitric acid, and rinsing with deionised or distilled water before use.

  • Before use, a blank consisting of deionised or distilled water should be filtered to ensure freedom from contamination.

  • The sample should be filtered as soon as possible after collection, discarding the first 50 mL of filtrate, and the filtrate should be acidified with nitric acid to pH <2.

  • If suspended metals are to be determined, the filter should be retained for digestion.

Care must be taken to avoid introducing contaminating metals from containers, lids, distilled or deionised water, acid preservative, or membrane filters; or from airborne contaminants in the form of smoke, dust, soot or aerosols.

Sampling for organic compounds and pesticides


Because organic compounds and pesticides, if present at all, are likely to occur only in very low concentrations, considerable care is needed in choosing and preparing sample containers. Bottles supplied by the analyst should be used, and the analyst’s instructions for sample handling and preservation followed. These instructions will vary with the compound being analysed and the methods of analysis used by the laboratory.

Sampling for microbial characteristics


  • Sufficient sodium thiosulfate should be added to the sample bottle to neutralise all residual chlorine (AS/NZS 2031:2001).

  • A chelating agent should be used in bottles receiving water containing copper, zinc or other heavy metals.

  • Drinking-water samples should be taken directly from a service pipe, not from an intermediate tank or cistern.

  • The bottle should not be filled to the top – leave an air space of at least 2.5 cm.

  • An ice-filled cooler should be used to transport samples to the laboratory.

The sample should, ideally, be analysed within 6 hours. Under exceptional circumstances the elapsed time may exceed 6 hours, but should not exceed 24 hours. If 6 hours is exceeded, the time interval should be reported with the results.1

Further advice on appropriate sampling technique can be found in Australian Standard AS/NZS 5567.5:1998 Water Quality – Sampling Part 5: Guidance on sampling of drinking water and water used for food and beverage processing.

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 HNO3 to pH <2

28 days




Arsenic

P(A), G(A)

500

Add HNO3 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 HNO3 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 HNO3 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 HNO3 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 and refrigerate

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 HNO3 to pH <2

28 days




Lead

P(A), G(A)

100

Add HNO3 to pH <2

28 days




Manganese

P(A), G(A)

100

Add HNO3 to pH <2

28 days




Mercury

G(A)

500

Add HNO3 to unfiltered sample to pH <1.

Add K2Cr2O3

28 days

Consult analyst for further instruction


Metals (general)

P(A), G(A)

100

Add HNO3 to pH <2

28 days




Metals (filterable)

P(A), G(A)

100

Filter immediately, add HNO3 to pH <2

28 days

0.45 μm filter

Nitrate

P, G

500

Refrigerate

24 hours

Unfiltered samples

Filter on site (0.45 μm 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

Refrigerate1.

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 dark2

7 days

Extract on site where practical. Consult with analyst

Radioactivity gross alpha and beta activity

P, G

1000

Add HNO3 to pH <2

28 days

Fill container completely to exclude air. Consult with analyst

Selenium

P(A), G(A)

100

Add HNO3 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 HNO3 to pH <2

28 days





Container P = Plastic (polyethylene or equivalent)

G = Glass

G(B) = Glass, borosilicate

P(A), G(A) = Rinsed with 50% HNO3

G(S) = Glass, rinsed with organic solvent, PTFE cap liner

PTFE = Polytetrafluoroethylene

Preservation Refrigerate = Store between 1º and 4ºC in the dark, do not freeze

HNO3 = Nitric acid (hydrochloric acid may be used in this context but nitric

acid is preferred)

NaOH = Sodium hydroxide solution (40% w/v)

K2Cr2O3 = Potassium dichromate
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