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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.

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

TestContainerSample 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)
Absorbanceplastic50 mLcool to <4 °C14 daysAPHA
Alkalinityplastic50 mLcool to <4 °C14 daysAPHA
Ammonia – Nplastic50 mLpH <2 (H2SO4), cool to <4 °C28 daysAPHA
Bromate (BrO3)plastic or glass40 mL50 mg/L EDA, cool to <4 °C28 daysUS EPA Method 302.0
Bromideplastic50 mLcool to <4 °C, dark28 daysAPHA
Chlorate (ClO3)plastic or glass40 mL50 mg/L EDA, cool to <4 °C28 daysUS EPA Method 302.0
Chlorideplastic50 mLnil28 daysAPHA
Chlorineplastic50 mLnil, field test only30 minAPHA
Chlorine, chloramineplastic50 mLsealed bottled water only30 min after openedAPHA
Chlorite (ClO2)plastic or glass (opaque)40 mL50 mg/L EDA, cool to <4 °C14 daysUS EPA Method 302.0
Chloroacetic acidsVial2 x 40 mL4 mg NH4Cl per vial, zero headspace, cool to <4 °C14 daysUS EPA 552.3
Chromium hexavalentplastic50 mLcool to <4 °C1 dayAPHA
plastic50 mLpH >12 (NaOH), cool to <4 °C28 daysUS EPA 1669
CODplastic50 mLpH <2 (H2SO4), cool to <4 °C28 daysAPHA
Colourplastic50 mLcool to <4 °C, dark2 daysAPHA
Conductivityplastic50 mLcool to <4 °C28 daysAPHA
Cyanidesplastic200 mLpH >12 (NaOH), cool to <4 °C, dark14 daysAPHA
Dioxinsamber glass2 x 1000 mLcool to <4 °C (if residual chlorine is present add 80 mg Na2S2Oper 1000 mL)1 year until (1 after) extractionUS EPA 1613
Fluorideplastic50 mLnone required28 daysAPHA
Formaldehydeglass40 mLNone required7 dayssubcontracted
Gross alpha/betaplastic1000 mLcool to <4 °C28 dayssubcontracted
Hardnessplastic50 mLcool to <4 °C or pH <2 (HNO3)7 days or 6 monthsAS/NZS 5667.1:1998 and APHA
Herbicides (includes glyphosate)glass500 mLcool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Iodideplastic50 mLcool to <4 °C28 daysAS/NZS 5667.1:1998
Iodineplastic50 mLnone required28 daysAPHA
Iron – ferrousglass40 mLpH <2 (HCl), no headspace3 daysNMI 2010
Mercuryplastic100 mLpH <2 (HNO3)28 daysAPHA
glass100 mLpH <2 (HNO3), 0.05% K2Cr2O71 monthAS/NZS 5667.1:1998
Metals – totalplastic100 mLpH <2 (HNO3)6 monthsAPHA
Micro (in natural)plastic (sterile)200 mLcool to <4 °C1 dayAS/NZS 5667.1:1998
Micro (in tap, plastic (sterile)200 mLcool to <4 °C, Na2S2O31 dayAS/NZS 5667.1:1998
i.e. chlorinated)
N (nitrate)plastic50 mLcool to <4 °C2 daysAPHA
N (nitrite)plastic50 mLcool to <4 °C2 daysAPHA
Organotins glass1000 mLcool to <4 °C7 days until (40 after) extractionUS EPA SW-846
(tributyl tin – TBT)
PAHsglass1 x 500 mLcool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL before adding acid)7 days until (40 after) extractionUS EPA SW-846
PBDEsamber glass2 x 1000 mLcool to <4 °C (if residual chlorine is present add 80 mg Na2S2Oper 1000 mL)1 year until (1 after) extractionUS EPA 1614
PCBs (dioxin-like)amber glass2 x 1000 mLcool to <4 °C (if residual chlorine is present add 80 mg Na2S2Oper 1000 mL)1 year until (1 after) extractionUS EPA 1668
PCBsglass500 mLcool to <4 °C*7 days until (40 after) extractionUS EPA SW-846
Pesticidesglass1 x 500 mLcool to <4 °C7 days until (40 after) extractionUS EPA SW-846
pHplastic50 mLcool to <4 °C3 daysNMI 2010
Phenols (speciated)glass1 x 500 mLcool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Phosphateplastic50 mLcool to <4 °C2 daysAPHA
Phosphateplastic50 mLfilter onsite, freeze28 daysAS/NZS 5667.1:1998
Phthalatesglass500 mLcool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Radium 226/228plastic2 x 1000 mLcool to <4 °C28 dayssubcontracted
Sulphateplastic50 mLcool to <4 °C28 daysAPHA
Sulphide (dissolved)plastic100 mLfilter, add 10 mL Cu 2,4 DMP (per 100 mL sample), cool to <4 °C12 hoursAS 3550.1
Sulphide (total)plastic100 mLcool, add 0.5 mL 2N zinc acetate and 1 mL 6N NaOH (per 100 mL sample), cool to <4 °C7 daysAPHA
SVOCs (includes ethers, amines, nitroaromatics, nitrosamines)glass500 mLcool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL before adding acid)7 days until (40 after) extractionUS EPA SW-846
Total dissolved solidsplastic50 mLcool to <4 °C7 daysAPHA
Thiocyanateplastic100 mLadd HNO3 or H2SO4 to pH<2, cool to <4 °C28 daysAPHA
Trihalomethanesvial2 x 40 mLpH <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 daysUS EPA SW-846
Turbidityplastic100 mLcool to <4 °C, store in dark2 daysAPHA
VOCs(includes C1–C5, halogenated aliphatics and aromatics, monocyclic aromatics, alcohols)vial2 x 40 mLpH <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 daysUS EPA SW-846

References 

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Last updated: 5 June 2019

Content ID: 64628