Co-crystallization with 1-(2-pyridylazo)-2-naphthol, and X-ray fluorescence, for trace metal analysis of water

• Published in: Talanta (Oxford) 1978-01, Vol.25 (11), p.653-658
• Main Authors: Vanderstappen, Michel G., Van Grieken, Rene E.
• Format: Article
• Language: English
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/0039-9140(78)80166-0

Adding 20mg of 1-(2-pyridylazo)-2-naphthol (PAN) to a water sample at 70°, and filtering off the precipitate after cooling, gives efficient preconcentration prior to X-ray fluorescence analysis of water. Up to the capacity of about 100 μeq of PAN used, the trace metal recoveries are around 90% or higher for Cr 3+, Mn 2+, Ni 2+, Cu 2+, Zn 2+, Hg 2+ and Eu 3+, and above 70% for many other ions. The recovery yields usually do not vary critically with pH in the neutral pH-range, and are practically independent of the sample salinity, sample volume and trace-metal concentration. Enrichment factors as high as 2 × 10 5 can be achieved. Counting statistics would then allow detection limits of 0.03 ppM. The blank levels in commercial PAN, however, lead to typical detection limits of about 1 ppm. The coefficient of variation is typically in the 5–10% range at the 10-ppM level. The accuracy and applicability of the procedure are illustrated by comparative analyses on samples of synthetic solutions, river and drinking water.