Determination of Trace Gold in Geochemical Samples by Flame Atomic Fluorescence Spectrometry with PUFP Separation and Enrichment

BACKGROUNDThe detection sensitivity, stability, and linear range of Au using flame atomic fluorescence spectrometry (FAFS) is comparable to the method of inductivity coupled plasma-mass spectrometry (ICP-MS). When Au concentration is below 0.5ng/g, it is difficult to accurately determine Au if the interference elements in FAFS are not separated and eliminated.

OBJECTIVESTo optimize the conditions during determination of trace Au by FAFS method.

METHODSThe optimized conditions for trace Au detection using FAFS were provided based on the conventional Au separation and enrichment method of polyurethane foam plastics (PUFP). Using the thiourea (3.0g/L) and HCl (1%) as desorption solution can effectively eliminate the Au memory effect after separation by PUFP with low Au background value (≤ 0.25ng/g), and 5μg/mL of Fe³⁺ solution added into Au standard solutions was used to eliminate the interference during Au detection using FAFS.

RESULTSThe method was used to analyze national standard materials GBW07805, GBW07242, GBW07244a, GBW07245a and GBW07247, which yielded the relative error (RE) and relative standard deviation (RSD) of less than 4.7% and 23.2%, respectively. The Au contents for 90 primary halo samples and 4 monitor samples were analyzed simultaneously using FAFS and ICP-MS. Results showed that no significant differences existed between the two methods with F=1.23 and the correlation coefficient of 1.01, which further proved the accuracy and reliability of FAFS.

CONCLUSIONSFAFS is simple, convenient, fast and practical. Method detection limit of Au is as low as 0.08ng/g, and the linear range (0.08-500ng/g) is three orders of magnitude.