Preparation of metal standard solution for chemical analysis of Fe, Cu, Cd, Hg and Pb

In an effort to establish traceability of chemical measurements in environmental analysis in Indonesia to national standard, metal standard solutions were prepared as certified reference materials (CRM). The reference materials are needed by environmental analysis laboratories, for instrument calibration in heavy metal pollutants analysis in water. This will provide traceability of the measurement to national standard. The metal standard solutions were prepared by weighing accurately and dissolving of high purity metals for Pb, Cd, Fe, Cu and mercuric chloride salt for Hg in acidic (nitric acid) solutions diluted to volume in a calibrated volumetric flask. The solutions were analyzed by complexometric-(EDTA)titrimetric methods using autotitrator with photometric endpoint detection. Metal standard solution, i.e. Standard Reference Material (SRM)from NIST, were used as primary standards for measurement traceability. EDTA solution was used as a titrant and it was standardized using the SRMs. Validation of the titrimetric method was carried out for the suitability of the method for the certification of the reference material candidates. The method was verified by validating its relevant performance characteristics. By comparing values from titrimetric method with those from gravimetric preparation, certified values of the prepared reference mateials were found.