Overview
ISO 4744:1984 specifies a standardized flame atomic absorption spectrometric (flame AAS) method for determining chromium in copper and copper alloys. The procedure covers sample dissolution, preparation of calibration standards, instrumental measurement, result calculation and reporting. The method is applicable to chromium contents between 0.003 and 2.0 % (m/m) and includes provisions for matrix matching and blank correction to ensure reliable results.
Key topics and technical requirements
- Scope and range: Applicable for chromium concentrations from 0.003% to 2.0% (m/m) in copper and copper alloys.
- Principle: Nebulisation of a dissolved sample into an air–acetylene flame and measurement of Cr atomic absorption using a chromium hollow‑cathode lamp; the standard specifies the analytical line used for measurement.
- Sample form and sampling: Preferably fine chips or turnings (thickness ≤ 0.5 mm) and a nominal analytical sample mass of about 1 g.
- Reagents: Analytical-grade reagents including nitric acid (~34% w/w), sulfuric acid (density 1.84 g/ml), hydrogen peroxide (30% w/w) and potassium bichromate for preparation of chromium standards.
- Matrix matching: Use of a 20 g/L copper base solution in calibration standards to compensate for matrix effects from the copper matrix.
- Calibration and measurement: Series of calibrated standards prepared from K2Cr2O7, construction of a calibration curve (multi‑point) and option to use bracketing measurements between similar matrix standards; routine blank determinations are required.
- Apparatus: Standard flame AAS instrument with air–acetylene burner, Cr hollow‑cathode lamp, compressed air and acetylene supply.
- Results and reporting: Results expressed as mg Cr per 100 ml of test solution and converted to % (m/m) of the original sample; the test report must identify the sample, method reference, results and any deviations or special operations.
Practical applications and users
ISO 4744 is intended for:
- Quality control laboratories in copper smelting, refining and alloy manufacturing
- Metallurgical testing and certification labs verifying chromium additives in copper‑chromium alloys
- Materials research groups and regulatory or compliance laboratories needing traceable chromium determinations in copper matrices
Benefits include standardized sample preparation, reduced matrix interference through matrix matching, and reproducible flame AAS measurement protocols.
Related standards
- Developed by ISO/TC 26 (Copper and copper alloys).
- The standard notes that a separate ISO document on sampling of copper and copper alloys is in preparation; laboratories should consult that sampling standard when available to ensure representative sampling.
Keywords: ISO 4744:1984, copper alloys chromium determination, flame atomic absorption spectrometry, flame AAS chromium, chromium in copper 0.003–2.0%, matrix matching, calibration curve.