⚗️ Trace and major elements in water (Al, As, Cd, Cr, Cu, Ni, Pb, Sb, Se, U…) — inductively coupled plasma mass spectrometry (ICP-MS)
In short
The measurement solution is introduced (by pneumatic nebulisation) into a radio-frequency argon plasma, where vaporisation, decomposition, atomisation and ionisation take place; the ions extracted through a vacuum interface are separated by a mass spectrometer (e. The test is performed according to PN-EN ISO 17294-2:2024-04 (ISO 17294-2:2023); Working range: typically from a few ng/l to mg/l, depending on the element and the matrix; linearity over more than several orders of magnitude. The procedure comprises 6 steps; it is used for: Drinking water and groundwater — simultaneous determination of several dozen trace elements at the ng/l–µg/l level, Surface water, wastewater and eluates — the reference method for metals under Dz.U. 2019 poz. 1311 (As, B, Mo, Ni and others), Digests of water and of sediments (ISO 15587-1/-2) once the interferences have been taken into account.
At a glance
- Standard: PN-EN ISO 17294-2:2024-04 (ISO 17294-2:2023)
- Category: Physicochemistry
- Procedure steps: 6
- LOQ (clean waters): 0.002–1.0 µg/l for most elements; e.g. As, Cd, Cr, Cu, Ni, Se, U 0.1 µg/l; Pb 0.1–0.2; Sb 0.2 µg/l
- Working range: typically from a few ng/l to mg/l, depending on the element and the matrix; linearity over more than several orders of magnitude
- Salinity: dissolved substances ≤ 2 g/l (conductivity < 2700 µS/cm), otherwise dilute
Overview
ISO 17294-2:2023 specifies a method for determining more than 60 elements in water (drinking water, surface water, groundwater, wastewater and eluates): among them aluminium, antimony, arsenic, barium, beryllium, bismuth, boron, cadmium, caesium, calcium, chromium, cobalt, copper, iron, lead, lithium, magnesium, manganese, mercury, molybdenum, nickel, phosphorus, potassium, selenium, silver, sodium, strontium, thallium, tin, titanium, uranium and its isotopes, vanadium, zinc, zirconium, as well as the lanthanides and the noble metals. Taking the specific interferences into account, these elements can also be determined in digests of water and of sediments (e.g. according to ISO 15587-1 or -2). The working range depends on the matrix and on the interferences: in drinking water and in waters of low pollution the limit of quantification (LOQ) of most elements lies between 0.002 µg/l and 1.0 µg/l (table 1 of the standard — for example As 0.1, Cd 0.1, Cr 0.1, Cu 0.1, Ni 0.1, Pb 0.1–0.2, Sb 0.2, Se 0.1, U 0.1 µg/l; Ca, K, Na and Fe higher), and the range typically covers concentrations from a few ng/l to mg/l. The limits of quantification depend on the contamination of the blank — the cleanliness of the laboratory air, of the reagents and of the glassware — and are higher where there are interferences or memory effects (ISO 17294-1). Other elements can be determined after validation (interferences, sensitivity, repeatability, recovery).
In Poland it is in force as PN-EN ISO 17294-2:2024-04 (English version; it replaced PN-EN ISO 17294-2:2016-11 and, before that, PN-EN ISO 17294-2:2006 "Oznaczanie 62 pierwiastków" [Determination of 62 elements]). The 2019 regulation (Dz.U. 2019 poz. 1311 [Journal of Laws 2019, item 1311]) names PN-EN ISO 17294-2 as the reference method for many metals in wastewater (among others arsenic, boron, molybdenum and nickel), and environmental laboratories run procedures under it for Tl, Ti, V, Be, Co, Sn, Cd, Pb, Ni and others. An application note for the Agilent 7850 spectrometer shows the analysis of 28 elements in natural, mineral and tap waters in accordance with ISO 17294-2: the helium collision mode in the ORS cell removes overlapping polyatomic ions, the M²⁺ correction improves the accuracy for As and Se in the presence of doubly charged ions of the rare earth elements, and efficient plasma conditions (a low CeO/Ce ratio) make it possible to analyse waters of varying matrix without matching the matrix of the standards.
Method principle
The multi-element determination of selected elements, including the isotopes of uranium, by ICP-MS comprises: the introduction of the measurement solution into a radio-frequency plasma (e.g. by pneumatic nebulisation), where the transfer of energy from the plasma causes the vaporisation, decomposition, atomisation and ionisation of the elements; the optional use of a collision or reaction cell to overcome a range of interferences; the extraction of the ions from the plasma through a differentially pumped vacuum interface with integrated ion optics and their separation according to the mass-to-charge ratio in a mass spectrometer (e.g. a quadrupole); the transmission of the ions through the separating system and their detection, usually by a continuous dynode electron multiplier, with processing of the signal by a data system; and the quantitative determination after calibration with suitable solutions. The dependence of the signal on the concentration is usually linear over a wide range (more than several orders of magnitude). The method for the isotopes of uranium is described in annex A; spectrometers with a magnetic sector give a higher mass resolution, which helps to separate the isotopes from interfering ions. Interferences: isobaric and non-isobaric — overlapping masses and physical effects of the matrix (table 2 of the standard, e.g. ⁷⁵As — ArCl, CaCl; ¹¹¹Cd — MoO, MoOH, ZrOH; ¹³⁸Ba — La⁺, Ce⁺; ⁴⁴Ca — Sr²⁺, COO); it is recommended to determine different isotopes of an element and to choose one that is free of interference, and where there is none — to apply a mathematical correction. Small drifts of intensity are corrected with an internal standard. In order to avoid physical and spectral interferences the concentration of dissolved substances (the salinity) should not exceed 2 g/l (a conductivity below 2700 µS/cm). When a collision/reaction cell is used, the user has to demonstrate that the chosen approach is suitable and achieves the required performance.
Applications
- Drinking water and groundwater — simultaneous determination of several dozen trace elements at the ng/l–µg/l level
- Surface water, wastewater and eluates — the reference method for metals under Dz.U. 2019 poz. 1311 (As, B, Mo, Ni and others)
- Digests of water and of sediments (ISO 15587-1/-2) once the interferences have been taken into account
- Isotopes of uranium (²³⁴U, ²³⁵U, ²³⁸U) — the procedure of annex A
- High-throughput laboratories — multi-sample sequences with an autosampler, the helium mode of the collision cell, M²⁺ correction for As and Se
Key parameters
| Parameter | Value |
|---|---|
| LOQ (clean waters) | 0.002–1.0 µg/l for most elements; e.g. As, Cd, Cr, Cu, Ni, Se, U 0.1 µg/l; Pb 0.1–0.2; Sb 0.2 µg/l |
| Working range | typically from a few ng/l to mg/l, depending on the element and the matrix; linearity over more than several orders of magnitude |
| Salinity | dissolved substances ≤ 2 g/l (conductivity < 2700 µS/cm), otherwise dilute |
| Interferences | isobaric (e.g. ¹³⁸Ba/La⁺, Ce⁺), polyatomic (ArCl on ⁷⁵As, MoO on ¹¹¹Cd), doubly charged (Sr²⁺ on ⁴⁴Ca); mathematical correction or a collision/reaction cell |
| Internal standard | correction of drift and of changes of intensity |
| Result | mass concentration in µg/l or mg/l after calibration |
Standard
- Standard number
- PN-EN ISO 17294-2:2024-04 (ISO 17294-2:2023)
- Title (PL)
- Jakość wody — Zastosowanie spektrometrii mas z plazmą wzbudzoną indukcyjnie (ICP-MS) — Część 2: Oznaczanie wybranych pierwiastków, w tym izotopów uranu
- Title (EN)
- Water quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) — Part 2: Determination of selected elements including uranium isotopes
Step-by-step procedure
-
Establishing the conditions
Depending on the range and the matrix, establish whether additional conditions are needed (the guidance of ISO 17294-1); check the salinity of the samples (≤ 2 g/l, < 2700 µS/cm) and dilute them if necessary; for digests take the interferences into account.
-
Preparation of the samples and the standards
Prepare acidified measurement solutions, calibration solutions and blanks from high-purity reagents; add the internal standard; work at a clean workstation in order to limit the contamination of the blank.
-
Tuning and control of interferences
Set the parameters of the plasma and of the ion optics (efficient conditions, low CeO/Ce), choose isotopes free of interference or define correction equations; if necessary switch on the collision/reaction cell and demonstrate that it is suitable.
-
Calibration
Measure the calibration solutions and establish the calibration functions (the relationship is usually linear over a wide range); for the isotopes of uranium proceed in accordance with annex A.
-
Measurement
Introduce the measurement solutions into the plasma through the nebuliser; record the intensities of the selected isotopes with the internal-standard correction; include controls (blanks, CRMs) in the sequence.
-
Calculation and test report
Calculate the mass concentrations (µg/l, mg/l) from the calibration functions after the corrections; report the LOQ, the isotopes and corrections used and any deviations.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| ICP-MS spectrometer (e.g. a quadrupole) with a pneumatic nebuliser, a spray chamber and a vacuum interface | e.g. an Agilent 7850 with an ORS4 cell (He mode) and a UHMI system | — |
| Collision/reaction cell (optional) | removal of polyatomic interferences | — |
| Detector — a continuous dynode electron multiplier; data system | ion counting, corrections, calibration | — |
| Autosampler | multi-sample sequences | — |
| Clean room / workstation with air filtration, plastic vessels cleaned with acid | limiting the contamination of the blank | — |
| High-purity argon, helium for the collision cell | plasma gas and collision gas | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| High-purity water and high-purity nitric acid | — | dilution, acidification of samples and standards, blanks |
| Single- and multi-element calibration solutions (certified) | — | calibration over the working range |
| Internal standard solution | — | correction of the drift of intensity |
| Certified reference materials of water | — | check of accuracy (e.g. As, Se in the presence of REE) |
Health and safety (OHS)
- The argon plasma (high temperature, UV radiation, RF field) — shields and extraction above the torch
- High-purity nitric acid — goggles, gloves, fume hood
- Argon and helium cylinders under pressure — secure them, use two-stage regulators
- Wastewater samples — possible pathogens; gloves
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 17294-2:2024-04 (ISO 17294-2:2023) — “Water quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) — Part 2: Determination of selected elements including uranium isotopes”.
How does this method work?
The multi-element determination of selected elements, including the isotopes of uranium, by ICP-MS comprises: the introduction of the measurement solution into a radio-frequency plasma (e.g.
What is the measuring range and accuracy?
LOQ (clean waters): 0.002–1.0 µg/l for most elements; e.g. As, Cd, Cr, Cu, Ni, Se, U 0.1 µg/l; Pb 0.1–0.2; Sb 0.2 µg/l; Working range: typically from a few ng/l to mg/l, depending on the element and the matrix; linearity over more than several orders of magnitude; Salinity: dissolved substances ≤ 2 g/l (conductivity < 2700 µS/cm), otherwise dilute; Interferences: isobaric (e.g. ¹³⁸Ba/La⁺, Ce⁺), polyatomic (ArCl on ⁷⁵As, MoO on ¹¹¹Cd), doubly charged (Sr²⁺ on ⁴⁴Ca); mathematical correction or a collision/reaction cell.
How long does the test take?
The procedure comprises 6 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
ICP-MS spectrometer (e.g. a quadrupole) with a pneumatic nebuliser, a spray chamber and a vacuum interface, Collision/reaction cell (optional), Detector — a continuous dynode electron multiplier; data system, Autosampler, Clean room / workstation with air filtration, plastic vessels cleaned with acid, High-purity argon, helium for the collision cell.
Where is this test used?
Drinking water and groundwater — simultaneous determination of several dozen trace elements at the ng/l–µg/l level; Surface water, wastewater and eluates — the reference method for metals under Dz.U. 2019 poz. 1311 (As, B, Mo, Ni and others); Digests of water and of sediments (ISO 15587-1/-2) once the interferences have been taken into account; Isotopes of uranium (²³⁴U, ²³⁵U, ²³⁸U) — the procedure of annex A; High-throughput laboratories — multi-sample sequences with an autosampler, the helium mode of the collision cell, M²⁺ correction for As and Se.
What safety precautions apply?
The argon plasma (high temperature, UV radiation, RF field) — shields and extraction above the torch; High-purity nitric acid — goggles, gloves, fume hood; Argon and helium cylinders under pressure — secure them, use two-stage regulators; Wastewater samples — possible pathogens; gloves.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 17294-2.