Overview
ISO/DTS 4188 specifies an ICP‑OES (inductively coupled plasma optical emission spectrometric) method for the determination of arsenic (As) in magnesium and magnesium alloys. Drafted by ISO/TC 79/SC 5 (Secretariat: SAC) in 2023, the document defines the analytical principle, required reagents and apparatus, sample preparation, calibration and result expression for arsenic mass fractions in the range 0.001% to 0.050% (mass fraction). The method is intended for alloys with limited rare‑earth and zirconium contents (e.g., Ce, Gd, Nd, Zr limits given in the standard).
Key topics and technical requirements
- Analytical principle: Dissolution of a prepared test sample in nitric and hydrochloric acids followed by nebulization into an ICP‑OES; measurement of arsenic emission intensity and quantification via a magnesium‑based calibration curve.
- Scope limits: Applicable for arsenic between 0.001% and 0.050% mass fraction; restricted to alloys with specified maximum contents of Ce, Gd, Nd and Zr.
- Reagents and standards: Use of analytical‑grade reagents and Grade 2 water (ISO 3696). The draft lists primary materials including pure magnesium and pure arsenic (purity > 99.99%), hydrochloric and nitric acids, and prepared arsenic standard solutions (examples given: 1 g/L, 0.1 g/L, 0.01 g/L).
- Apparatus requirements: An ICP‑OES instrument with specification of measurement wavelength(s), limit of detection, and calibration linearity criteria (sections dedicated to wavelength selection, LOD, and calibration curve performance).
- Quality and reporting: Sections cover sampling and sample preparation, calibration procedure, measurement steps, method of calculation, precision information, limit of detection (Annex A) and test report requirements. Informative annexes provide precision test details and graphical representation of precision data.
- Normative references: Includes ISO 648, ISO 1042 (laboratory glassware) and ISO 3696 (water for analytical use); related material safety and lab practice references implied.
Practical applications and users
- Who uses it: Analytical chemistry laboratories, metallurgical QC labs, material certification bodies, and manufacturers of magnesium products who require robust arsenic quantification.
- Why it matters: Arsenic is a hazardous impurity that affects health and the environment. This method supports compliance and material safety assessments-particularly for magnesium components intended for food, medical, or other safety‑sensitive applications.
- Use cases: Routine quality control of raw magnesium and alloys, acceptance testing of incoming batches, regulatory testing tied to impurity limits (e.g., the combined Cd/Hg/As/Cr threshold in ISO 8287), and investigative analysis when impurity sources are suspected.
Related standards
Keywords: ISO/DTS 4188, magnesium alloys, arsenic determination, ICP‑OES, inductively coupled plasma optical emission spectrometry, limit of detection, calibration curve, sample preparation, magnesium‑based calibration.