Water Chemistry
pH Value of Waters
SOP: 1010
UKAS accredited
Measurement of pH using a pH meter
Electrical Conductivity of Waters
SOP: 1020
UKAS accredited
Measurement of the electrical conductivity using a conductivity meter.
Total Suspended Solids
SOP: 1030
UKAS accredited
Filtration of a mixed sample through a GF/C 1.2µm glass fibre filter and determination of the mass of residue retained dried at 105°C.
Total Dissolved Solids (TDS)
SOP: 1040
Calculated from conductivity utilising an electrical conductivity meter reading directly in mg/l TDS.
Biochemical Oxygen Demand (ATU BOD5)
SOP: 1090
Electrometric determination of dissolved oxygen in a seeded sample initially and after 5 days incubation at 20°C.
Chemical Oxygen Demand (COD)
SOP: 1100
UKAS accredited
Dichromate oxidation of organic matter in sample followed by colorimetric determination of residual Cr[VI].
Dissolved Oxygen (DO)
SOP: 1150
Electrometric determination (on site preferred), using an oxygen sensitive membrane electrode.
Anions, Alkalinity & Ammonium in Waters
SOP: 1220
UKAS accredited
Fluoride; chloride; nitrite; nitrate; total oxidisable nitrogen (TON); sulphate; phosphate; alkalinity; ammonium.
Automated colorimetric analysis using a discrete analyser.
Alkalinity of Waters
SOP: 1260
Titration of the sample with a standard solution of acid using instrumental detection to end points at pH 8.3 and pH 4.5.
Total Hardness of Waters
SOP: 1270
UKAS accredited
Calculated from calcium and magnesium concentrations:
Total Hardness (mg/l CaCO3 equivalent) = (2.5 x Ca (mg/l)) + (4.12 x Mg (mg/l)) where 2.5 is derived from the molecular weight of CaCO3 (100) / Ca (40) and 4.12 is derived from the molecular weight of CaCO3 (100) / Mg (24.3)
Cyanides & Thiocyanate in Waters
SOP: 1300
UKAS accredited
Free [or easy liberatable] cyanide, total cyanide, complex cyanide, thiocyanate.
Free cyanide: Automated acid distillation followed by colorimetric development with chloramine-T and pyridine/barbituric acid. Intensity of colour at 610nm is measured.
Total cyanide by UV decomposition of complex bound cyanides with measurement of resulting free cyanide as above.
Complex cyanide determined by difference.
Thiocyanate is converted to cyanogen chloride which reacts with chloramine-T and 1.3-dimethylbarbituric acid/isonicotinic acid. Intensity of colour measured at 600nm.
Sulphide in Waters
SOP: 1325
UKAS accredited
Sulphide is analysed by automated colorimetric analysis on an Aquakem 600 discrete analyser using N,N–dimethyl-p-phenylenediamine.
Total Nitrogen in Waters
SOP: 1340
Total nitrogen, organic nitrogen and Kjeldahl nitrogen.
An alkaline persulphate digestion converts all forms of nitrogen to nitrate. The nitrate then reacts with chromotropic acid under strongly acidic conditions to form a yellow complex. Its absorbance is measured at 420nm.
Cations in Waters by ICP-MS
SOP: 1415
UKAS accredited
Sodium; potassium; calcium; magnesium.
Direct determination by inductively coupled plasma – mass spectrometry (ICP-MS).
Metals in Waters by ICP-MS
SOP: 1450
UKAS accredited
UKAS accredited: antimony; arsenic; barium; beryllium; boron; cadmium; chromium; cobalt; copper; lead; manganese; mercury; molybdenum; nickel; selenium; tin; vanadium; zinc
Not accredited: iron; aluminium
Filtration of samples followed by direct determination by inductively coupled plasma – mass spectrometry (ICP-MS).
Mercury low-level in Waters by Atomic Fluorescence Spectroscopy
SOP: 1460
UKAS accredited
Mercury is determined by atomic fluorescence spectroscopy (AFS), with a collimated UV source, wavelength 253.7 nm.
Hexavalent Chromium in Waters
SOP: 1490
UKAS accredited
Automated colorimetric analysis by a discrete analyser using 1,5-diphenylcarbazide.
Total Organic Carbon in Waters
SOP: 1610
UKAS accredited
Instrumental catalytic oxidation of organic (and inorganic) carbon and subsequent measurement of the carbon dioxide liberated by infra-red (IR) detection. Inorganic carbon is determined separately and the total organic carbon is derived by difference.
Total Petroleum Hydrocarbons (TPH) in Waters by GC-FID
SOP: 1670
UKAS accredited
Total petroleum hydrocarbons in the range C6–C40 with optional carbon banding and/or Gasoline Range Organics (GRO), Diesel Range Organics (DRO) and Lubricating oil Range Organics LRO.
Liquid/liquid solvent extraction of a water sample into pentane followed by determination of total petroleum hydrocarbons by gas chromatography using flame ionisation detection (GC-FID).
Aliphatic/Aromatic Petroleum Hydrocarbons in Waters by GCxGC-FID
SOP: 1680
aliphatic banding: >C5–C6, >C6–C8, >C8–C10, >C10–C12, >C12–C16, >C16–C21, >C21– C35, >C35– C44
aromatic banding: >C5–C7, >C7–C8, >C8–C10, >C10–C12, >C12–C16, >C16– C21, >C21– C35, >C35– C44
Liquid/liquid solvent extraction of a water sample into pentane followed by determination of total petroleum hydrocarbons by two dimensional gas chromatography using flame ionisation detection (GCxGC-FID).
Speciated Polynuclear Aromatic Hydrocarbons (PAH) in Waters by GC-FID
SOP: 1700
UKAS accredited
Acenaphthene; acenaphthylene; anthracene; benzo[a]anthracene; benzo[a]pyrene; benzo[b]fluoranthene; benzo[ghi]perylene; benzo[k]fluoranthene; chrysene; dibenz[ah]anthracene; fluoranthene; fluorene; indeno[123cd]pyrene; naphthalene; phenanthrene; pyrene
Liquid/liquid solvent extraction of a water sample into pentane followed by the determination of polynuclear aromatic hydrocarbons by gas chromatography with flame ionisation detection (GC-FID).
Volatile Organic Compounds (VOCs) in Waters by Headspace GC-MS
SOP: 1760
UKAS accredited
UKAS accredited: please refer to UKAS schedule for individually accredited compounds.
Analysis of a water sample for volatile organic compounds by automated headspace gas chromatography with mass spectrometric detection (HS-GC-MS).
Based upon USEPA Method 8260.
Semi-Volatile Organic Compounds (SVOCs) in Waters by GC-MS
SOP: 1790
Liquid/liquid solvent extraction of a water sample followed by determination of semi-volatile organic compounds by gas chromatography with mass spectrometric detection (GC-MS).
Speciated Polynuclear Aromatic Hydrocarbons (PAHs) in Waters by GC-MS
SOP: 1800
UKAS accredited
Acenaphthene; acenaphthylene; anthracene; benzo[a]anthracene; benzo[a]pyrene; benzo[b]fluoranthene; benzo[ghi]perylene; benzo[k]fluoranthene; chrysene; dibenz[ah]anthracene; fluoranthene; fluorene; indeno[123cd]pyrene; naphthalene; phenanthrene; pyrene.
Liquid/liquid solvent extraction of a water sample followed by determination of PAH by gas chromatography (GC) with mass spectrometric detection (MS).
Polychlorinated Biphenyls (PCB) as Aroclors in Waters by GC-MS / GC-ECD
SOP: 1810
Results are normally expressed as Aroclor 1242.
Liquid/liquid solvent extraction of a water sample followed by the determination of PCBs by gas chromatography using mass spectrometric (GC-MS) detection for identification and electron capture detection (GC-ECD) for quantitation if present.
Polychlorinated Biphenyls (PCB) ICES7 Congeners in Waters by GC-MS
SOP: 1815
ICES (International Council for the Exploration of the Sea) PCB congeners:
PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, PCB180
Liquid/liquid solvent extraction of a water sample followed by the determination of PCBs by gas chromatography using mass spectrometric detection (GC-MS).
Organophosphorus (O-P) Pesticides in Waters by GC-MS
SOP: 1820
The method includes parathion, malathion, chlorpyrifos, diazinon plus any organophosphorus pesticides specified by the client.
Liquid/liquid solvent extraction of a water sample followed by the determination of organophosphorus pesticides by gas chromatography using mass spectrometric detection (GC-MS).
Organonitrogen (O-N) Pesticides in Waters by GC-MS
SOP: 1830
The method includes triazines plus any organonitrogen pesticides specified by the client.
Liquid/liquid solvent extraction of a water sample followed by the determination of organonitrogen pesticides by gas chromatography using mass spectrometric detection (GC-MS).
Organochlorine (O-Cl) Pesticides in Waters by GC-MS
SOP: 1840
The method includes DDT and its metabolites, the so-called ‘drins’ and Lindane, plus any determinands specified by the client.
Liquid/liquid solvent extraction of a water sample followed by the determination of organochlorine pesticides by gas chromatography using mass spectrometric detection (GC-MS).
Phenols in Waters by GC-MS
SOP: 1900
The method includes 24 substituted phenols, including chlorophenols.
Liquid/liquid solvent extraction of a water sample followed by the determination of phenols by gas chromatography using mass spectrometric detection (GC-MS).
Phenols in Waters by HPLC
SOP: 1920
UKAS accredited
The method includes resorcinol, phenol, methylphenols, dimethylphenols, 1-naphthol and trimethylphenols.
Chlorophenols are not detected by this method.
Determination by high performance liquid chromatography (HPLC) using electrochemical detection.
