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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.

Test Container Sample 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/acidity plastic 50 mL cool to <4 °C 14 days APHA
BOD plastic 500 mL cool to <4 °C 2 days APHA
Bromide plastic 50 mL cool to <4 °C, dark 28 days APHA
Carbon – TOC glass 40 mL pH <2 (H2SO4 ), cool to <4 °C 28 days APHA
Carbon – Dissolved Organic Carbon glass 40 mL filter onsite, pH <2 (H2SO4), cool to <4 °C 28 days APHA
Chlorophyll-a plastic 1000 mL cool to <4 °C, dark 2 days APHA
plastic 1000 mL filter, freeze residue 28 days APHA
Chlorine plastic 50 mL nil, field test only 30 min APHA
Chlorine (for sealed bottled water) plastic 50 mL sealed bottled water only 30 min after opening APHA
Chloride plastic 50 mL nil 28 days APHA
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
Ferrous iron glass 40 mL pH <2 (HCl), no headspace 3 days NMI 2010
Fluoride plastic 50 mL none required 28 days APHA
Haloacetic acids vial 2 x 40 mL 4 mg NH4Cl per vial, zero headspace and cool to <4 °C 14 days US EPA 552.3
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 200 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
MBAS glass 200 mL cool to <4 °C 2 days APHA
Mercury plastic 100 mL pH <2 (HNO3) 28 days APHA
glass 100 mL pH <2 (HNO3), 0.05% potassium dichromate 1 month AS/NZS 5667.1:1998
Metals – total plastic 100 mL pH <2 (HNO3) 6 months APHA
Metals – filtered plastic 100 mL filter onsite, pH <2 (HNO3) 6 months APHA
Microbiology (in natural) plastic (sterile) 200 mL cool to <4 °C 1 day AS/NZS 5667.1:1998
Microbiology (in tap, i.e. chlorinated) plastic (sterile) 200 mL cool to <4 °C, Na2S2O3 1 day AS/NZS 5667.1:1998
N (ammonia) plastic 50 mL pH <2 (H2SO4), cool to <4 °C 28 days APHA
N (nitrate) plastic 50 mL cool to <4 °C 2 days APHA
N (nitrate) plastic 50 mL filter on site, freeze 28 days AS/NZS 5667.1:1998
N (nitrite) plastic 50 mL cool to <4 °C 2 days APHA
N (TKN) plastic 50 mL pH <2 (H2SO4), cool to <4 °C 28 days APHA
N (total) plastic 50 mL pH <2 (H2SO4), cool to <4 °C 28 days APHA
Oil and grease glass 1000 mL pH <2 (H2SO4), cool to <4 °C 28 days APHA
Organochlorine pesticides glass 200 mL* cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
Organophosphorus pesticides glass 200 mL* cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
Organotins (tributyl tin – TBT) glass 1000 mL cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
PAHs† glass 200 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 200 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
PFAS† (including PFOS and PFOA) HDPE 2 x 60 mL cool to <4 °C 14 days until (28 after) extraction US EPA 537 ISO 5667-3
pH plastic 50 mL cool to <4 °C 3 days NMI 2010
Phenols (speciated) glass 200 mL* cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
Phenols (total) plastic or glass 100 mL pH <2 (H2SO4), cool to <4 °C 28 days APHA
Phenoxy acid herbicides glass 200 mL* cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
Phosphorus – total plastic 100 mL pH <2 (HNO3) 28 days APHA
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 200 mL* cool to <4 °C 7 days until (40 after) extraction US EPA SW-846
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 7 days 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 200 mL* cool to <4 °C (if residual chlorine is present add 80 mg Na2S2O3 per 1000 mL) 7 days until (40 after) extraction US EPA SW-846
TDS 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
TRH (C6–C10)/BTEX vial 2 x 40 mL pH <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 days US EPA SW-846
TRH (C10–C40) glass 200 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
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 Na 2S2O3 per 1000 mL before adding acid) 14 days US EPA SW-846
TSS plastic 500 mL cool to <4 °C 7 days APHA
Turbidity plastic 100 mL cool to <4 °C, store in dark 2 days APHA
VOCs (includes C1–C5, halogenated aliphatics, halogenated aromatics, monocyclic aromatics and 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 Na 2S2O3 per 1000 mL of sample before adding acid — use NaHSO4 if dangerous goods restrictions apply) 14 days US EPA SW-846

References 

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Last updated: 13 November 2020

Content ID: 64626