⚗️ Heavy metals in food (ICP-MS)
In short
Determination of heavy metals (Pb, Cd, Hg, As) and trace elements in food by microwave mineralization + ICP-MS. The test is performed according to PN-EN 13805:2014 / AOAC 2015.01; Linear range: 0.001–1000 µg/L (5–6 orders of magnitude). The procedure comprises 10 steps (about 2 h 28 min–2 h 45 min in total); it is used for: Official control of Pb, Cd, Hg, As in food (EU Reg. 2023/915), Heavy metal monitoring in fish and seafood, Food control for infants and young children.
At a glance
- Standard: PN-EN 13805:2014 / AOAC 2015.01
- Category: Food Chemistry
- Procedure steps: 10
- Total time of stages: 2 h 28 min–2 h 45 min
- Main elements: Pb, Cd, Hg, As (+ Se, Sn, Ni, Cr, etc.)
- Limit of quantification (LOQ): 0.001–0.01 mg/kg (depending on element)
- Linear range: 0.001–1000 µg/L (5–6 orders of magnitude)
Overview
Heavy metal determination in food is a key element of food safety control. Lead (Pb), cadmium (Cd), mercury (Hg), and arsenic (As) are toxic even at very low concentrations and are subject to strict EU regulations (EC Reg. 1881/2006, EU Reg. 2023/915). Standard PN-EN 13805 describes pressure digestion (microwave mineralization) as the sample preparation stage.
Microwave mineralization involves dissolving the food sample (0.5–1.0 g) in concentrated nitric acid (HNO₃) and hydrogen peroxide (H₂O₂) in closed PTFE/TFM vessels under elevated pressure and temperature (180–220°C). Organic matter is oxidized and metals pass into solution as soluble salts. Mineralization in a closed system prevents loss of volatile elements (Hg, As, Se).
Mineralizate analysis is performed by ICP-MS (Inductively Coupled Plasma Mass Spectrometry), which provides multi-element detection with limits of quantification at 0.001–0.01 µg/kg (sub-ppb) level. ICP-MS with collision-reaction cell (He, H₂) eliminates spectral interferences (e.g., ⁴⁰Ar³⁵Cl⁺ on ⁷⁵As⁺). The method allows simultaneous determination of 20–30 elements in one measurement.
The method is required by EFSA monitoring programs, official food control (EC Reg. 882/2004), and HACCP systems in the food industry. Typical EU limits: Pb 0.02–0.30 mg/kg, Cd 0.010–0.10 mg/kg, Hg 0.50 mg/kg (fish), inorganic As 0.10–0.30 mg/kg.
Method principle
Food sample (0.5–1.0 g) is digested in PTFE/TFM vessel with 5–8 mL conc. HNO₃ and 1–2 mL H₂O₂ in microwave mineralizer (180–220°C, 20–40 bar, 20–40 min). Organic matter is oxidized to CO₂ and H₂O, and metals pass into acid solution. After cooling and dilution (to 50–100 mL with ultrapure water), the solution is analyzed by ICP-MS. Sample is nebulized and introduced to argon plasma (6000–8000 K), where atoms are ionized. Ions are separated in mass analyzer (quadrupole) by m/z ratio and counted by detector. Concentrations are calculated from calibration curves using internal standards.
Applications
- Official control of Pb, Cd, Hg, As in food (EU Reg. 2023/915)
- Heavy metal monitoring in fish and seafood
- Food control for infants and young children
- Bottled water and beverage testing
- Dietary supplement and special food analysis
- Cereal, vegetable, and fruit control (cadmium in rice, lead in cocoa)
- Mineral component determination (Ca, Fe, Zn, Se) for nutritional declaration
- BRC/IFS/FSSC 22000 certification
Key parameters
| Parameter | Value |
|---|---|
| Main elements | Pb, Cd, Hg, As (+ Se, Sn, Ni, Cr, etc.) |
| Limit of quantification (LOQ) | 0.001–0.01 mg/kg (depending on element) |
| Linear range | 0.001–1000 µg/L (5–6 orders of magnitude) |
| Sample size | 0.5–1.0 g |
| Mineralization temperature | 180–220°C (closed system) |
| ICP-MS analysis time | 2–5 min per sample (20–30 elements) |
Standard
- Standard number
- PN-EN 13805:2014 / AOAC 2015.01
- Title (PL)
- Żywność — Oznaczanie pierwiastków śladowych — Roztwarzanie ciśnieniowe
- Title (EN)
- Foodstuffs — Determination of trace elements — Pressure digestion
Step-by-step procedure
-
Sample preparation
Homogenize sample. Weigh 0.5–1.0 g into PTFE/TFM mineralization vessel. Record mass with 0.001 g accuracy.
-
Reagent addition
Add 5–8 mL HNO₃ suprapur and 1–2 mL H₂O₂. Leave 15 min for preliminary reaction (with open vessel).
-
Microwave mineralization
Close vessels and place in mineralizer. Program: ramp to 200°C (20 min), hold 200°C (15 min), cooling.
-
Dilution
Transfer mineralizate to 50 mL flask. Fill to mark with ultrapure water (18.2 MΩ·cm). Mix.
-
Calibration preparation
Prepare calibration curves (5–7 points) from certified multi-element standards in 2% HNO₃ matrix.
-
ICP-MS tuning
Perform system tuning with tune solution. Optimize sensitivity, oxides (CeO⁺/Ce⁺ < 2%), doubly charged (Ce²⁺/Ce⁺ < 3%).
-
ICP-MS measurement
Measure samples in He mode (collision-reaction cell) for As, Se, Cr. Other elements in standard mode. Internal standards online.
-
Calculations
Concentration [mg/kg] = (c_sample − c_blank) × V_final / m_sample × dilution factor.
-
Quality control
Every series: reagent blank, CRM, spike (fortification), duplicate. CRM recovery 85–115%, RSD < 10%.
-
Comparison with limits
Compare result with EU limits (Reg. 2023/915): Pb 0.02–0.30, Cd 0.010–0.10, Hg 0.50 (fish), inorg. As 0.10–0.30 mg/kg.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Microwave mineralizer | CEM MARS 6, Milestone Ethos UP, Anton Paar Multiwave 7000 | 120 000–250 000 PLN |
| ICP-MS system | Agilent 7850, Thermo iCAP RQ, PerkinElmer NexION 2200 | 400 000–800 000 PLN |
| Ultrapure water system | Millipore Milli-Q IQ 7000, Elga Purelab Flex | 40 000–80 000 PLN |
| PTFE/TFM mineralization vessels | CEM Easy Prep vessels (set of 24 pcs.) or Milestone SK-15 | 15 000–30 000 PLN |
| Analytical balance 0.1 mg | Mettler Toledo XPE205, Sartorius Quintix 224 | 8 000–25 000 PLN |
| Clean room / laminar flow | AirClean 600 PCR, Kojair BW-130 | 15 000–50 000 PLN |
| Argon 5.0 (99.999%) | 50 L cylinder (200 bar), consumption ~15 L/min | 400–700 PLN / cylinder |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Nitric acid 67% suprapur / trace metal | 7697-37-2 | Ultra-pure for mineralization, 1 L (Merck Suprapur or Fisher Optima) |
| Hydrogen peroxide 30% suprapur | 7722-84-1 | Assisting oxidation of organic matter, 500 mL |
| Multi-element ICP-MS standards | — | Certified CRM solutions (Inorganic Ventures, Merck CertiPUR), 100 mL |
| Internal standards (Sc, Ge, In, Bi) | — | For signal drift correction and matrix effect, 10 mg/L solution |
| ICP-MS tune solution | — | Tuning solution (Li, Co, Y, Ce, Tl) for parameter optimization, 100 mL |
| Reference material CRM | — | E.g., NIST SRM 1568b (rice), ERM-BB422 (fish), for validation |
Health and safety (OHS)
- Concentrated HNO₃ — highly corrosive and oxidizing (H272, H314). Use acid-resistant gloves, goggles, apron. Work under fume hood.
- H₂O₂ 30% — oxidizing (H271, H302, H318). Risk of exothermic reaction with organic matter.
- Microwave mineralization — high pressure and temperature. Do not open vessels before cooling below 50°C.
- Heavy metal standards — toxic (Pb, Cd, Hg, As). Use gloves, work under fume hood.
- Argon — inert gas, but displaces oxygen. Room ventilation and O₂ sensor.
- Acid waste with metals — collect separately as hazardous waste.
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN 13805:2014 / AOAC 2015.01 — “Foodstuffs — Determination of trace elements — Pressure digestion”.
How does this method work?
Food sample (0.5–1.
What is the measuring range and accuracy?
Main elements: Pb, Cd, Hg, As (+ Se, Sn, Ni, Cr, etc.); Limit of quantification (LOQ): 0.001–0.01 mg/kg (depending on element); Linear range: 0.001–1000 µg/L (5–6 orders of magnitude); Sample size: 0.5–1.0 g.
How long does the test take?
The times given for the individual stages add up to approximately 2 h 28 min–2 h 45 min. The procedure comprises 10 steps.
What equipment is required?
Microwave mineralizer, ICP-MS system, Ultrapure water system, PTFE/TFM mineralization vessels, Analytical balance 0.1 mg, Clean room / laminar flow, Argon 5.0 (99.999%). Indicative cost of the core instrument (Microwave mineralizer): 120 000–250 000 PLN.
Where is this test used?
Official control of Pb, Cd, Hg, As in food (EU Reg. 2023/915); Heavy metal monitoring in fish and seafood; Food control for infants and young children; Bottled water and beverage testing; Dietary supplement and special food analysis; Cereal, vegetable, and fruit control (cadmium in rice, lead in cocoa); Mineral component determination (Ca, Fe, Zn, Se) for nutritional declaration; BRC/IFS/FSSC 22000 certification.
What safety precautions apply?
Concentrated HNO₃ — highly corrosive and oxidizing (H272, H314). Use acid-resistant gloves, goggles, apron. Work under fume hood.; H₂O₂ 30% — oxidizing (H271, H302, H318). Risk of exothermic reaction with organic matter.; Microwave mineralization — high pressure and temperature. Do not open vessels before cooling below 50°C.; Heavy metal standards — toxic (Pb, Cd, Hg, As). Use gloves, work under fume hood.; Argon — inert gas, but displaces oxygen. Room ventilation and O₂ sensor.; Acid waste with metals — collect separately as hazardous waste.
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 13805.