🔬 Nickel in Water

Physicochemistry PN-EN ISO 8288

Overview

Nickel (Ni) is a heavy metal of toxicological significance — it is one of the strongest contact allergens (nickel allergy affects about 10–15% of the population), and with chronic oral exposure can cause gastrointestinal disorders, kidney damage and carcinogenicity (nickel compounds — group 1 according to IARC). The permissible nickel concentration in drinking water is 20 µg/L (according to EU Directive 2020/2184 and MH Regulation).

Sources of nickel in waters are wastewater from electroplating (nickel plating), metallurgical industry (nickel steels, alloys), Ni-Cd and Ni-MH battery production, corrosion of stainless steel fittings, fossil fuel combustion, and natural leaching from nickel-bearing minerals.

Flame AAS (FAAS) is the basic method for determining nickel in waters at concentrations of 0.1–10 mg/L. The 232.0 nm resonance line is most commonly used, although the 341.5 nm line may be an alternative at higher concentrations. The acetylene-air flame provides sufficient energy for nickel atomization. The method is simple, fast and economical.

For concentrations below 0.02 mg/L (drinking water standard level), the FAAS technique is insufficient — GF-AAS (detection limit about 0.2 µg/L) or ICP-MS must be used. In laboratory practice, nickel in drinking water is determined mainly by GF-AAS or ICP-MS technique, and FAAS is used for wastewater control.

Method principle

A water sample acidified with HNO₃ is introduced through a nebulizer into an acetylene-air flame (about 2300°C). In the flame, the sample aerosol undergoes desolvation, thermal decomposition and atomization — free nickel atoms are formed. Ni atoms in the ground state absorb radiation from an HCL lamp at a wavelength of 232.0 nm (or alternatively 341.5 nm). Absorbance, proportional to Ni concentration (Beer-Lambert law), is measured by a detector and converted to concentration using a calibration curve.

Applications

• Control of electroplating wastewater (water permit)
• Monitoring of wastewater from metallurgy and metalworking
• Testing of surface waters (Water Framework Directive)
• Drinking water quality control (Ni ≤20 µg/L — by GF-AAS technique)
• Analysis of mine waters
• Control of stainless steel corrosion in water installations
• Testing of groundwater at waste disposal sites

Key parameters

Standard

Standard number

PN-EN ISO 8288:2002

Title (PL)

Jakość wody — Oznaczanie kobaltu, niklu, miedzi, cynku, kadmu i ołowiu — Metody płomieniowej absorpcyjnej spektrometrii atomowej

Title (EN)

Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead — Flame atomic absorption spectrometric methods

Step-by-step procedure

1. Sample acidification

   Add HNO₃ 65% to pH <2 (1 mL per 100 mL sample). Store in PE/PP containers at 4°C.

   ⏱ Time: 5 min

2. Preparation of standards

   Prepare calibration series: 0 (blank), 0.1, 0.5, 1.0, 2.0, 5.0 mg/L Ni in 1% HNO₃ from 1000 mg/L solution.

   ⏱ Time: 15 min

3. Instrument setup

   Install Ni HCL lamp. Set wavelength 232.0 nm, slit 0.2 nm, lamp current 4 mA. Stabilize lamp 15 min.

   ⏱ Time: 15 min

4. Ignition and flame optimization

   Ignite acetylene-air flame (flow: air 13.5 L/min, acetylene 2.0 L/min). Set fuel-lean flame (blue).

   ⏱ Time: 5 min

5. Instrument calibration

   Aspirate blank and standards sequentially. Plot calibration curve. Correlation coefficient R² ≥0.999.

   ⏱ Time: 10 min

6. Sample measurement

   Aspirate sample (approx. 5 mL/min). Read absorbance after stabilization (5–10 s). Aspirate 1% HNO₃ between samples (10 s).

   ⏱ Time: 1 min/sample

7. Quality control

   Every 10 samples: blank (A <0.005), control standard (recovery 95–105%), duplicate (RPD <5%).

   ⏱ Time: 5 min

8. Dilution of high concentration samples

   Dilute samples with concentration >5 mg/L to calibration range. Use 1% HNO₃ as diluting medium.

9. Work closure

   Aspirate deionized water (2 min). Extinguish flame. Rinse nebulizer and spray chamber. Turn off lamp.

   ⏱ Time: 5 min

10. Calculation and result reporting

    Ni concentration from calibration curve, considering dilution. Result in mg/L with 3 significant figures.

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Nickel compounds — carcinogenic (H350i — inhalation), strongly sensitizing (H317) — gloves and goggles mandatory
• Acetylene — flammable and explosive gas, cylinder in vertical position, away from heat sources
• Nitric acid — corrosive, work under fume hood
• AAS flame — temperature ~2300°C, burner exhaust hood mandatory
• Nickel-containing waste — collect separately, do not pour into sewage

Frequently asked questions