National Measurement Institute

Drinking water (not bottled) samples

We recommend the following preservation procedures, holding times and conditions when submitting non-bottled drinking water samples for testing. Please treat these recommendations as a guide only.

During sampling, do not to rinse out or spill preservatives.

Avoid cross-contaminating bottles (e.g. nitric acid used for metals can contaminate nitrate analysis).

Some tests must minimise exposure to air to avoid analyte losses.

If tests require the addition of preservatives prior to sampling, contact us beforehand to facilitate supply of appropriate containers.

Many of the preservatives are hazardous chemicals (e.g. strong acids, alkaline solutions). They must be handled with care and we recommend you wear safety glasses and gloves.

For product water, please supply (as would be delivered to the consumer) at least 15 L in sealed containers all with the same packing date or use by date. If pack size is greater than 15 L, please supply one unit as a sealed package. Do not split or sub-sample bulk containers.

Test Container Sample size  Preservation procedure  Holding time  Reference
(low levels of organics require 1 L or 2 L) (treatment after collection until arrival at NMI) (maximum time from collection until analysis)
Absorbance plastic 50 mL cool to <4 °C 14 days APHA
Alkalinity plastic 50 mL cool to <4 °C 14 days APHA
Ammonia – N plastic 50 mL pH <2 (H2SO4), cool to <4 °C 28 days APHA
Bromate (BrO3–) plastic or glass 40 mL 50 mg/L EDA, cool to <4 °C 28 days US EPA Method 302.0
Bromide plastic 50 mL cool to <4 °C, dark 28 days APHA
Chlorate (ClO3–) plastic or glass 40 mL 50 mg/L EDA, cool to <4 °C 28 days US EPA Method 302.0
Chloride plastic 50 mL nil 28 days APHA
Chlorine plastic 50 mL nil, field test only 30 min APHA
Chlorine, chloramine plastic 50 mL sealed bottled water only 30 min after opened APHA
Chlorite (ClO2–) plastic or glass (opaque) 40 mL 50 mg/L EDA, cool to <4 °C 14 days US EPA Method 302.0
Chloroacetic acids Vial 2 x 40 mL 4 mg NH4Cl per vial, zero headspace, cool to <4 °C 14 days US EPA 552.3
Chromium hexavalent plastic 50 mL cool to <4 °C 1 day APHA
plastic 50 mL pH >12 (NaOH), cool to <4 °C 28 days US EPA 1669
COD plastic 50 mL pH <2 (H2SO4), cool to <4 °C 28 days APHA
Colour plastic 50 mL cool to <4 °C, dark 2 days APHA
Conductivity plastic 50 mL cool to <4 °C 28 days APHA
Cyanides plastic 200 mL pH >12 (NaOH), cool to <4 °C, dark 14 days APHA
Dioxins amber glass 2 x 1000 mL cool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL) 1 year until (1 after) extraction US EPA 1613
Fluoride plastic 50 mL none required 28 days APHA
Formaldehyde glass 40 mL None required 7 days subcontracted
Gross alpha/beta plastic 1000 mL cool to <4 °C 28 days subcontracted
Hardness plastic 50 mL cool to <4 °C or pH <2 (HNO3) 7 days or 6 months AS/NZS 5667.1:1998 and APHA
Herbicides (includes glyphosate) glass 500 mL cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
Iodide plastic 50 mL cool to <4 °C 28 days AS/NZS 5667.1:1998
Iodine plastic 50 mL none required 28 days APHA
Iron – ferrous glass 40 mL pH <2 (HCl), no headspace 3 days NMI 2010
Mercury plastic 100 mL pH <2 (HNO3) 28 days APHA
glass 100 mL pH <2 (HNO3), 0.05% K2Cr2O7 1 month AS/NZS 5667.1:1998
Metals – total plastic 100 mL pH <2 (HNO3) 6 months APHA
Micro (in natural) plastic (sterile) 200 mL cool to <4 °C 1 day AS/NZS 5667.1:1998
Micro (in tap,  plastic (sterile) 200 mL cool to <4 °C, Na2S2O3 1 day AS/NZS 5667.1:1998
i.e. chlorinated)
N (nitrate) plastic 50 mL cool to <4 °C 2 days APHA
N (nitrite) plastic 50 mL cool to <4 °C 2 days APHA
Organotins  glass 1000 mL cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
(tributyl tin – TBT)
PAHs glass 1 x 500 mL cool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL before adding acid) 7 days until (40 after) extraction US EPA SW-846
PBDEs amber glass 2 x 1000 mL cool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL) 1 year until (1 after) extraction US EPA 1614
PCBs (dioxin-like) amber glass 2 x 1000 mL cool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL) 1 year until (1 after) extraction US EPA 1668
PCBs glass 500 mL cool to <4 °C* 7 days until (40 after) extraction US EPA SW-846
Pesticides glass 1 x 500 mL cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
pH plastic 50 mL cool to <4 °C 3 days NMI 2010
Phenols (speciated) glass 1 x 500 mL cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
Phosphate plastic 50 mL cool to <4 °C 2 days APHA
Phosphate plastic 50 mL filter onsite, freeze 28 days AS/NZS 5667.1:1998
Phthalates glass 500 mL cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
Radium 226/228 plastic 2 x 1000 mL cool to <4 °C 28 days subcontracted
Sulphate plastic 50 mL cool to <4 °C 28 days APHA
Sulphide (dissolved) plastic 100 mL filter, add 10 mL Cu 2,4 DMP (per 100 mL sample), cool to <4 °C 12 hours AS 3550.1
Sulphide (total) plastic 100 mL cool, add 0.5 mL 2N zinc acetate and 1 mL 6N NaOH (per 100 mL sample), cool to <4 °C 7 days APHA
SVOCs (includes ethers, amines, nitroaromatics, nitrosamines) glass 500 mL cool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL before adding acid) 7 days until (40 after) extraction US EPA SW-846
Total dissolved solids plastic 50 mL cool to <4 °C 7 days APHA
Thiocyanate plastic 100 mL add HNO3 or H2SO4 to pH<2, cool to <4 °C 28 days APHA
Trihalomethanes vial 2 x 40 mL pH <2 (H2SO4 or HCl), cool to <4 °C, zero headspace (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL before adding acid) 14 days US EPA SW-846
Turbidity plastic 100 mL cool to <4 °C, store in dark 2 days APHA
VOCs(includes C1–C5, halogenated aliphatics and aromatics, monocyclic aromatics, alcohols) vial 2 x 40 mL pH <2 (H2SO4 or HCl), cool to <4 °C, zero headspace (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL before adding acid) 14 days US EPA SW-846

References