Arsenic content testing is a critical quality control and compliance procedure across the non-ferrous metals industry, covering copper, lead, zinc, aluminum, tin, nickel, and their alloys and concentrates. Accurate determination of arsenic—from percentage levels in ores down to trace and ultra-trace levels in high-purity metals—protects product performance, trade valuation, human health, and environmental compliance. This article explains the key sample types, testing items, analytical methods, applicable standards, and typical applications of arsenic determination in non-ferrous metals.
Technical Overview
Arsenic (As) is a harmful impurity element that enters the non-ferrous metallurgical production chain mainly through sulfide ores and concentrates of copper, lead, and zinc, and it persists throughout smelting, refining, and downstream fabrication. Even at low concentrations, arsenic can degrade the mechanical, electrical, and corrosion properties of metals and alloys, poison process catalysts and electrolytes, complicate slag handling, and create occupational and environmental exposure risks. For this reason, arsenic is classified as a penalty element in concentrate trading and as a strictly limited impurity in refined metal and alloy specifications.
Arsenic content testing provides the quantitative basis for raw material valuation, smelting process control, product grade certification, and regulatory compliance. Depending on the matrix and the concentration range, testing is performed by classical spectrophotometry, hydride generation atomic absorption spectrometry (HG-AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), or X-ray fluorescence (XRF) screening. Accredited third-party laboratories operating under ISO/IEC 17025 quality management systems routinely conduct these determinations in accordance with international (ISO, ASTM, EN, JIS) and Chinese national (GB) standards.
Testing Samples
Ores and Concentrates
Concentrates are the dominant carriers of arsenic in the non-ferrous supply chain, and their arsenic content directly affects settlement pricing and smelter acceptance.
- Copper sulfide concentrates (typical arsenic range: hundreds of ppm to several percent)
- Lead concentrates and lead–silver concentrates
- Zinc concentrates and mixed bulk concentrates
- Complex polymetallic ores and antimony-bearing materials
Refined Metals and Alloys
Finished metals and wrought or cast alloys require trace-level arsenic verification against grade specifications, for example Grade A copper cathode with an arsenic limit of 0.0005% (5 ppm).
- Copper cathode, brass, bronze, and copper–nickel alloys
- Refined lead, lead–calcium and lead–antimony battery alloys
- Zinc ingots and zinc die-casting alloys (Zamak series)
- Aluminum and aluminum alloys, tin ingots, tin solders, and nickel materials
High-Purity Metals and Electronic Materials
Semiconductor, photovoltaic, and electronic packaging applications demand ultra-trace arsenic control, often at sub-ppm to ppb levels, in high-purity copper, aluminum, tin, and solder materials.
By-products and Secondary Materials
- Smelter flue dusts, arsenic-bearing residues, and sludges
- Slags and intermediate mattes for process balance and waste classification
- Recycled and secondary raw materials, including scrap and electronic waste streams
Testing Items
The core deliverable is the total arsenic mass fraction in the submitted sample, reported with the applicable method, basis, and measurement uncertainty. Typical testing scopes include:
- Total arsenic in concentrates and ores, generally from 0.005% up to several percent, used for pricing, penalty clauses, and blending control
- Trace arsenic in refined metals and alloys, typically in the 0.0001%–0.05% (1–500 ppm) range, for grade conformity
- Ultra-trace arsenic in high-purity and electronic-grade metals at ppb levels
- Arsenic leachability in slags and dusts for hazardous waste classification and environmental compliance
- Verification of conformity against customer specifications, purchase contracts, and regulatory substance restrictions such as REACH candidate-listed arsenic compounds
Testing Methods
Sample Preparation and Digestion
Reliable arsenic data begin with representative sampling, milling, and moisture determination. Because arsenic forms volatile chlorides and hydrides, digestion protocols are designed to keep arsenic fully in solution while completely dissolving the matrix. Common approaches include:
- Aqua regia (HCl–HNO3) digestion for copper, brass, and most alloys
- Nitric–hydrofluoric acid mixtures (with boric acid complexation) for aluminum alloys and silicate-bearing matrices
- Sulfuric–nitric–perchloric fuming digestion for refractory sulfide concentrates
- Sodium peroxide fusion for highly refractory slags and dusts
- Closed-vessel microwave digestion to prevent arsenic loss and minimize blank contamination
Molybdenum Blue and DDTC-Ag Spectrophotometry
Classical wet-chemical spectrophotometry remains a robust reference approach for moderate to high arsenic contents. In the molybdenum blue method, arsenic(V) forms an arsenomolybdate heteropoly acid that is reduced to a blue complex measured near 840 nm. In the silver diethyldithiocarbamate (DDTC-Ag) method, arsine generated from the sample solution is absorbed and quantified colorimetrically. These methods offer good precision at elevated levels and low equipment cost, though they are more labor-intensive.
Hydride Generation Atomic Absorption Spectrometry (HG-AAS)
HG-AAS is the workhorse for trace arsenic in metals and concentrates. Arsenic is first pre-reduced from As(V) to As(III) using potassium iodide–ascorbic acid or thiourea, then converted to arsine (AsH3) with sodium borohydride and swept into a heated quartz cell for atomization. Hydride generation separates arsenic from the bulk matrix and provides detection limits down to approximately 0.1 µg/g in solids. Transition metals such as copper, nickel, and cobalt can suppress hydride formation and are masked with thiourea or L-cysteine. ASTM E1613 describes the hydride generation AAS determination of arsenic and is widely referenced for lead and lead alloys.
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)
ICP-OES enables rapid multi-element analysis, allowing arsenic to be determined simultaneously with other impurities such as lead, bismuth, antimony, and sulfur. The most sensitive arsenic emission lines lie in the vacuum ultraviolet region (188.979 nm and 193.696 nm), so instruments with inert-gas purged or vacuum optics are preferred. Detection limits in solution are typically 1–10 µg/L, translating to roughly 0.5–5 µg/g in digested solids. Spectral interferences must be checked and corrected using background positioning or inter-element correction.
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
ICP-MS delivers the lowest detection limits—below 0.01 µg/L in solution and down to ng/g levels in solids—making it the method of choice for high-purity metals and electronic materials. The principal spectral interference is 40Ar35Cl+ on the monoisotopic 75As+, which is effectively resolved with helium collision-mode kinetic energy discrimination, reaction cell technology, or mathematical correction. Isotope dilution and standard addition further improve accuracy in difficult matrices.
X-Ray Fluorescence (XRF) Screening
Energy-dispersive and wavelength-dispersive XRF provide fast, non-destructive screening of arsenic in concentrates, ingots, and alloys, with practical detection limits near 10–50 ppm depending on the matrix. XRF results for arsenic should be confirmed by a wet-chemical or plasma-based method when contractual decisions or regulatory compliance are at stake.
Applicable Standards
- GB/T 3884 series — methods for chemical analysis of copper concentrates, including arsenic determination
- GB/T 8151 series and GB/T 8152 series — chemical analysis of zinc concentrates and lead concentrates respectively
- GB/T 5121 series — chemical analysis of copper and copper alloys, covering arsenic and other impurity elements
- GB/T 20975 series — chemical analysis of aluminum and aluminum alloys
- ISO 10258 — copper sulfide concentrates: determination of arsenic content
- ASTM E1613 — determination of arsenic by hydride generation atomic absorption spectrometry
- ISO/IEC 17025 — general requirements for the competence of testing and calibration laboratories
Quality Assurance
Every determination batch should include reagent blanks, certified reference materials (CRMs) matched to the matrix, duplicate digestions, and spike recovery checks, with typical acceptance of 90–110% recovery and relative deviations below 5% at trace levels. Control charts and method validation data (linearity, limit of quantification, precision, accuracy) underpin the traceability of reported values.
Applications
- Concentrate trading and valuation: quantification of penalty elements for contract settlement, blending, and smelter feed management
- Smelting and refining control: arsenic mass balance across furnace feeds, mattes, slags, dusts, and electrolytes to stabilize operations and minimize volatile arsenic emissions
- Grade certification of refined copper, lead, zinc, tin, and aluminum against national and international specification limits
- Plumbing and potable water products: verification of brass and copper alloy components where arsenic leaching into drinking water is regulated
- Electronics and semiconductors: ultra-trace impurity qualification of solders, bonding wires, sputtering targets, and high-purity metals
- Battery manufacturing: impurity control in lead-based grid and active-material alloys
- Environmental and waste management: classification of arsenic-bearing slags, dusts, and residues and compliance with solid waste leaching criteria
- Research and development: alloy development, corrosion studies, and recycling process optimization in accredited third-party laboratories
FAQ
Why is arsenic strictly limited in non-ferrous metals?
Arsenic reduces ductility, conductivity, and corrosion resistance of metals and alloys, contaminates electrolytic refining circuits, accumulates in process streams, and poses serious toxicological risks to workers and the environment. Buyers therefore impose tight maximum limits and apply financial penalties on concentrates exceeding agreed arsenic thresholds.
What detection limits can be achieved?
Spectrophotometric methods typically quantify arsenic above about 0.005% (50 ppm). HG-AAS reaches roughly 0.1 µg/g, ICP-OES achieves about 0.5–5 µg/g in solids depending on the digestion dilution, and ICP-MS extends to ng/g levels for high-purity materials.
How much sample is required for testing?
For homogeneous metals and alloys, 5–20 g of millings or drillings is generally sufficient. Concentrates, ores, dusts, and slags require 50–200 g of properly sampled, dried, and pulverized material to guarantee representativeness, along with a moisture determination if results are needed on a dry basis.
Can XRF screening replace laboratory chemical analysis?
XRF is an excellent rapid screening tool for production control, but arsenic at low ppm levels in heavy-element matrices can suffer spectral overlap and matrix effects. Contractual, certification, and regulatory decisions should be based on validated wet-chemical, AAS, or ICP methods.
How are interferences handled in arsenic determination?
In hydride techniques, As(V) is pre-reduced to As(III) and interfering transition metals are masked with thiourea or L-cysteine. In ICP-OES, background and spectral overlaps at the 189 nm and 193.7 nm lines are corrected instrumentally. In ICP-MS, the ArCl+ interference at mass 75 is removed using collision/reaction cell technology or correction equations.
What is the typical turnaround time?
Standard arsenic determinations on metals and alloys are usually completed within 3–5 working days after sample receipt; complex matrices such as slags, dusts, or high-sulfide concentrates, or ultra-trace ICP-MS work, may require 5–10 working days depending on digestion and validation requirements.