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We recommend the following preservation procedures, holding times and conditions when submitting aqueous samples for testing by the National Measurement Institute (NMI). Please treat these recommendations as a guide only.

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

  • dissolved metals (such as groundwaters) samples should be 0.45 μm filtered into a HNO3 preserved bottle. If you have not field filtered and acidified samples, we will filter any unpreserved sample container then acidify when we receive them.
  • total recoverable metals (such as surface waters) samples should be placed unfiltered into a HNO3 preserved bottle. If you have not field preserved samples, we will sub-sample from the unpreserved bottle on receipt and acidify with HNO3)

In the sample size column below, * indicates that larger volumes are required for lower limiting of reporting analyses.

TestContainerSample size (low levels of organics require 1 L or 2 L)Preservation procedure (treatment after collection until arrival at NMI) Holding time (maximum time from collection until analysis)Reference
Alkalinity/acidityplastic50 mLcool to <4 °C14 daysAPHA
BODplastic500 mLcool to <4 °C2 daysAPHA
Bromideplastic50 mLcool to <4 °C, dark28 daysAPHA
Carbon – TOCglass40 mLpH <2 (H2SO4 ), cool to <4 °C28 daysAPHA
Carbon – Dissolved Organic Carbonglass40 mLfilter onsite, pH <2 (H2SO4), cool to <4 °C28 daysAPHA
Chlorophyll-aplastic1000 mLcool to <4 °C, dark2 daysAPHA
plastic1000 mLfilter, freeze residue28 daysAPHA
Chlorineplastic50 mLnil, field test only30 minAPHA
Chlorine (for sealed bottled water)plastic50 mLsealed bottled water only30 min after openingAPHA
Chlorideplastic50 mLnil28 daysAPHA
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
Cyanides†plastic200 mLpH >12 (NaOH), cool to <4 °C, dark14 daysAPHA
Dioxins†amber glass2 x 1000 mLcool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL)1 year until (1 after) extractionUS EPA 1613
Ferrous ironglass40 mLpH <2 (HCl), no headspace3 daysNMI 2010
Fluorideplastic50 mLnone required28 daysAPHA
Haloacetic acidsvial2 x 40 mL4 mg NH4Cl per vial, zero headspace and cool to <4 °C14 daysUS EPA 552.3
Hardnessplastic50 mLcool to <4 °C or pH <2 (HNO3)7 days or 6 monthsAS/NZS 5667.1:1998 and APHA
Herbicides (includes glyphosate)glass200 mL*cool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Iodideplastic50 mLcool to <4 °C28 daysAS/NZS 5667.1:1998
MBASglass200 mLcool to <4 °C2 daysAPHA
Mercuryplastic100 mLpH <2 (HNO3)28 daysAPHA
glass100 mLpH <2 (HNO3), 0.05% potassium dichromate1 monthAS/NZS 5667.1:1998
Metals – totalplastic100 mLpH <2 (HNO3)6 monthsAPHA
Metals – filteredplastic100 mLfilter onsite, pH <2 (HNO3)6 monthsAPHA
Microbiology (in natural)plastic (sterile)200 mLcool to <4 °C1 dayAS/NZS 5667.1:1998
Microbiology (in tap, i.e. chlorinated)plastic (sterile)200 mLcool to <4 °C, Na2S2O31 dayAS/NZS 5667.1:1998
N (ammonia)plastic50 mLpH <2 (H2SO4), cool to <4 °C28 daysAPHA
N (nitrate)plastic50 mLcool to <4 °C2 daysAPHA
N (nitrate)plastic50 mLfilter on site, freeze28 daysAS/NZS 5667.1:1998
N (nitrite)plastic50 mLcool to <4 °C2 daysAPHA
N (TKN)plastic50 mLpH <2 (H2SO4), cool to <4 °C28 daysAPHA
N (total)plastic50 mLpH <2 (H2SO4), cool to <4 °C28 daysAPHA
Oil and greaseglass1000 mLpH <2 (H2SO4), cool to <4 °C28 daysAPHA
Organochlorine pesticidesglass200 mL*cool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Organophosphorus pesticidesglass200 mL*cool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Organotins (tributyl tin – TBT)glass1000 mLcool to <4 °C7 days until (40 after) extractionUS EPA SW-846
PAHs†glass200 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) extractionUS EPA SW-846
PBDEs†amber glass2 x 1000 mLcool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 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 Na2S2O3 per 1000 mL)1 year until (1 after) extractionUS EPA 1668
PCBs†glass200 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) extractionUS EPA SW-846
PFAS† (including PFOS and PFOA)HDPE2 x 60 mLcool to <4 °C14 days until (28 after) extractionUS EPA 537 ISO 5667-3
pHplastic50 mLcool to <4 °C3 daysNMI 2010
Phenols (speciated)glass200 mL*cool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Phenols (total)plastic or glass100 mLpH <2 (H2SO4), cool to <4 °C28 daysAPHA
Phenoxy acid herbicidesglass200 mL*cool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Phosphorus – totalplastic100 mLpH <2 (HNO3)28 daysAPHA
Phosphateplastic50 mLcool to <4 °C2 daysAPHA
Phosphateplastic50 mLfilter onsite, freeze28 daysAS/NZS 5667.1:1998
Phthalatesglass200 mL*cool to <4 °C7 days until (40 after) extractionUS EPA SW-846
Sulphateplastic50 mLcool to <4 °C28 daysAPHA
Sulphide (dissolved)plastic100 mLfilter, add 10 mL Cu 2,4 DMP (per 100 mL sample), cool to <4 °C7 daysAS 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)glass200 mL*cool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL)7 days until (40 after) extractionUS EPA SW-846
TDSplastic50 mLcool to <4 °C7 daysAPHA
Thiocyanateplastic100 mLadd HNO3 or H2SO4 to pH<2, cool to <4 °C28 daysAPHA
TRH (C6–C10)/BTEXvial2 x 40 mLpH <2 (H2SO4 or HCl), cool to <4 °C, zero headspace (if residual chlorine is present add 80 mg Na 2S2O3 per 1000 mL of sample before adding acid — use NaHSO4 if dangerous goods restrictions apply)14 daysUS EPA SW-846
TRH (C10–C40)glass200 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) extractionUS EPA SW-846
Trihalomethanesvial2 x 40 mLpH <2 (H2SO4 or HCl), cool to <4 °C, zero headspace (if residual chlorine is present add 80 mg Na 2S2O3 per 1000 mL before adding acid)14 daysUS EPA SW-846
TSSplastic500 mLcool to <4 °C7 daysAPHA
Turbidityplastic100 mLcool to <4 °C, store in dark2 daysAPHA
VOCs (includes C1–C5, halogenated aliphatics, halogenated aromatics, monocyclic aromatics and alcohols)vial2 x 40 mLpH <2 (H2SO4 or HCl), cool to <4 °C, zero headspace (if residual chlorine is present add 80 mg Na 2S2O3 per 1000 mL of sample before adding acid — use NaHSO4 if dangerous goods restrictions apply)14 daysUS EPA SW-846

References 

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Last updated: 21 June 2019

Content ID: 64626