Nickel Content Analysis and Determination in Water Quality Testing

Nickel content analysis and determination in water is a critical component of environmental monitoring, drinking water safety assessment, and industrial wastewater compliance testing. This technical article provides a comprehensive overview of nickel testing in water, covering applicable sample types, testing parameters, internationally recognized analytical methods such as atomic absorption spectrometry (AAS), ICP-OES, and ICP-MS, as well as relevant ISO, ASTM, and GB standards. Whether you are evaluating electroplating effluent, groundwater, or municipal drinking water, this guide explains how accurate nickel quantification is achieved in accredited third-party laboratories.

Technical Overview

Nickel (Ni) is a transition metal widely used in stainless steel production, electroplating, battery manufacturing, alloy fabrication, and chemical catalysis. Although nickel is an essential trace element for some organisms at very low concentrations, elevated exposure through drinking water or contaminated water bodies can cause skin dermatitis, allergic reactions, and potential long-term health risks. Nickel enters aquatic environments through industrial discharges, mining runoff, atmospheric deposition, and the corrosion of nickel-containing plumbing materials.

Because nickel concentrations of regulatory concern are typically in the microgram-per-liter (µg/L) to low milligram-per-liter (mg/L) range, accurate determination requires sensitive instrumental techniques, rigorous sample pretreatment, and strict quality control procedures. Regulatory frameworks around the world, including the Chinese national drinking water standard (GB 5749), the WHO Guidelines for Drinking-water Quality, and the EU Drinking Water Directive, have established strict limits for nickel, making reliable nickel analysis essential for water suppliers, industrial dischargers, and environmental authorities.

Testing Samples

Drinking Water and Source Water

Treated tap water, distributed drinking water, and raw source water from reservoirs, rivers, and lakes are analyzed to verify compliance with drinking water quality standards. Nickel monitoring in distribution networks is particularly important where nickel-plated fixtures or certain stainless steel components may leach nickel into the water.

Groundwater

Groundwater from monitoring wells, production wells, and remediation sites is tested to evaluate nickel contamination from landfill leachate, mining activities, or industrial spills. Low detection limits are often required because background nickel levels in groundwater are typically very low.

Surface Water

Rivers, lakes, estuaries, and coastal waters are monitored to assess the environmental quality of receiving water bodies and to support environmental impact assessments and pollution source tracing investigations.

Industrial Wastewater and Effluent

Effluent from electroplating plants, metal finishing facilities, stainless steel mills, smelters, battery manufacturing plants, and chemical refineries frequently contains elevated nickel levels. Discharge compliance testing determines whether total nickel concentrations meet permitted discharge limits before release into public sewers or natural water bodies.

Seawater and High-Salinity Water

Marine water samples near coastal industrial zones, harbors, and offshore platforms require matrix-tolerant analytical methods due to the high dissolved salt content, which can interfere with conventional spectroscopic measurement.

Testing Items

Depending on the regulatory requirement and the purpose of the assessment, the following nickel-related parameters are commonly measured:

• Dissolved nickel: the nickel fraction passing through a 0.45 µm membrane filter, reflecting the bioavailable and mobile portion of nickel in the water column.
• Total nickel: the entire nickel content including particulate-bound nickel, determined after acid digestion of the unfiltered sample.
• Total recoverable nickel: nickel recovered after mild acid digestion with nitric acid at low temperature, as specified in some standard methods.
• Nickel speciation screening: optional partitioning between soluble ionic nickel, complexed nickel, and particulate nickel for environmental fate studies and toxicity evaluation.
• Supporting parameters: pH, conductivity, total suspended solids (TSS), and hardness, which are frequently measured alongside nickel for regulatory interpretation and data validation.

Testing Methods

Spectrophotometry (Dimethylglyoxime Method)

The classical dimethylglyoxime spectrophotometric method, standardized in GB 11910-89, relies on the formation of a red nickel-dimethylglyoxime complex under oxidizing alkaline conditions, measured at approximately 530 nm. This method is suitable for nickel concentrations from roughly 0.1 to 4 mg/L and remains a cost-effective option for highly contaminated wastewater samples.

Flame Atomic Absorption Spectrometry (FAAS)

Flame AAS, specified in GB 11912-89, ISO 8288, and ASTM D1886 (Test Method A), aspirates the acidified sample into an air-acetylene flame where nickel atoms absorb radiation from a nickel hollow cathode lamp at 232.0 nm. FAAS offers good precision and a practical working range from approximately 0.05 to 5 mg/L, making it ideal for industrial effluent monitoring.

Graphite Furnace Atomic Absorption Spectrometry (GFAAS)

GFAAS, covered by ISO 15586 and ASTM D1886 (Test Method B), electrothermally atomizes a small sample aliquot in a graphite tube, achieving detection limits in the range of 1 to 5 µg/L. This high-sensitivity technique is widely used for drinking water, groundwater, and trace-level environmental samples.

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)

ICP-OES, standardized in ISO 11885, HJ 776-2015, and ASTM D1976, simultaneously excites atoms in an argon plasma and measures characteristic emission lines, commonly the 231.604 nm nickel line. With multi-element capability, robustness against high dissolved solids, and detection limits of a few µg/L, ICP-OES is the preferred method for comprehensive water quality screening.

Inductively Coupled Plasma Mass Spectrometry (ICP-MS)

ICP-MS, specified in ISO 17294-2, HJ 700-2014, ASTM D5673, and GB/T 5750 series methods, offers the highest sensitivity with instrumental detection limits below 0.1 µg/L for nickel (isotopes 58Ni, 60Ni, and 62Ni). ICP-MS is the method of choice for ultra-trace analysis of drinking water, pristine groundwater, and research applications, and it enables full multi-element characterization in a single run.

Sample Collection, Preservation, and Pretreatment

Proper handling is critical to data quality. Samples for dissolved nickel are field-filtered through 0.45 µm membranes; samples for total nickel are collected unfiltered and digested with nitric acid (or nitric-hydrochloric acid mixtures) on a hot plate or in a microwave digestion system. Key preservation requirements include:

• Collection in acid-washed HDPE or PTFE bottles to minimize adsorption losses.
• Acidification with high-purity nitric acid to pH below 2 immediately after collection.
• Storage at approximately 4 °C and analysis within six months for preserved metal samples.
• Use of ultrapure reagents and Class 100 clean-air handling for trace-level ICP-MS work to avoid contamination.

Quality Assurance and Quality Control

Accredited third-party laboratories validate every batch of nickel determinations through a structured QA/QC regime, which typically includes method blanks, laboratory control samples, matrix spikes with acceptance recovery criteria (commonly 80–120 percent), duplicate analysis, multi-point calibration curves with correlation coefficients above 0.995, interference checks, and certified reference materials (CRMs) traceable to national metrology institutes. Method detection limits (MDLs) are empirically established according to recognized protocols, and results are reported with measurement uncertainty where required.

Applications

Nickel content analysis in water supports a wide spectrum of regulatory, industrial, and scientific applications, including:

• Drinking water compliance monitoring: verifying that treated and distributed water meets the nickel limit of 0.02 mg/L specified in GB 5749-2022 and comparable international guidelines.
• Industrial discharge supervision: demonstrating compliance of electroplating, metal finishing, and smelting effluent with total nickel discharge limits under standards such as GB 8978 and sector-specific emission standards.
• Environmental impact assessment: establishing baseline nickel levels and predicting receptor water quality for new construction projects and discharge permit applications.
• Groundwater pollution investigation and remediation: delineing plumes, tracking remediation performance, and confirming site closure criteria.
• Surface water quality classification: supporting evaluation against environmental quality standards such as GB 3838 for rivers, lakes, and reservoirs.
• Process water and utility management: controlling nickel contamination in boiler feedwater, cooling circuits, and ultrapure water systems in power, electronics, and pharmaceutical facilities.
• Product and material certification: supplying leachate and extractables data for water-contact materials, plumbing components, and consumer products under regulations such as the EU Drinking Water Directive and national plumbing codes.
• Scientific research: supporting geochemical studies, ecotoxicology experiments, and corrosion research involving nickel release kinetics.

FAQ

What is the regulatory limit for nickel in drinking water?

The Chinese national drinking water standard GB 5749-2022 sets a limit of 0.02 mg/L (20 µg/L) for nickel. The EU Drinking Water Directive similarly specifies 20 µg/L, while the WHO guideline value is 0.07 mg/L. Always confirm the applicable limit for your jurisdiction and sample type before selecting an analytical method.

What is the difference between dissolved nickel and total nickel?

Dissolved nickel is measured in the filtrate after the sample passes through a 0.45 µm membrane filter, whereas total nickel is measured in the whole unfiltered sample after complete acid digestion. Total nickel is normally equal to or higher than dissolved nickel, and discharge permits typically regulate the total nickel fraction.

Which method should be chosen for nickel determination?

Method selection depends on the expected concentration and matrix. For contaminated industrial wastewater above 0.05 mg/L, FAAS or the dimethylglyoxime spectrophotometric method is usually adequate. For drinking water, groundwater, and trace-level monitoring, GFAAS, ICP-OES, or ICP-MS is recommended, with ICP-MS providing the lowest detection limits and the greatest multi-element efficiency.

How should water samples for nickel analysis be collected and preserved?

Samples should be collected in acid-washed polyethylene bottles, filtered in the field if dissolved nickel is required, and acidified with nitric acid to pH below 2. Preserved samples should be transported cool and analyzed within six months. Chain-of-custody documentation should accompany all samples to guarantee traceability.

What detection limits can be achieved?

Typical method detection limits are approximately 0.1 mg/L for the dimethylglyoxime spectrophotometric method, 0.02–0.05 mg/L for FAAS, 1–5 µg/L for GFAAS, 1–10 µg/L for ICP-OES, and below 0.1–0.5 µg/L for ICP-MS, depending on instrument conditions, sample matrix, and pretreatment.

How is data quality ensured in nickel testing?

Reliable results depend on method blanks, matrix spike recoveries, calibration verification standards, duplicate analyses, certified reference materials, and participation in interlaboratory proficiency testing. Selecting an accredited third-party laboratory with ISO/IEC 17025 accreditation ensures that these controls are systematically applied and that reported data are defensible for regulatory purposes.