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A sensitive, rapid and inexpensive method to assess aluminium(III) ions in technetium eluates

Buroni, Federica E.; Lodola, Lorenzo; Persico, Marco G.; Aprile, Carlo

Nuclear Medicine Communications: July 2014 - Volume 35 - Issue 7 - p 777–780
doi: 10.1097/MNM.0000000000000108
Technical Note

The aim of the study was to validate a semiquantitative analytical method to identify the aluminium(III) [Al(III)] concentration in 99Mo/99mTc generator eluates to check the European Pharmacopoeia (Ph. Eur.) requirement (<5 μg/ml). Three different solutions measuring 20 ml – 0.2% 1,10-phenanthroline, 0.05% chrome azurol S and 20% hexamethylenetetramine – were prepared. A cellulose filter paper was subsequently immersed in them, dried overnight at room temperature and cut into rectangles. A volume of 5 μl of first eluates of various 99Mo/99mTc generators was placed onto a reagent paper and the spot colour was compared with a standard aluminium solutions scale (0–100 μg/ml). A cyan/magenta/yellow/key (CMYK) model analysis was adapted to quantify the intensity of colour on the paper, and the presence of aluminium in the eluates was detected by a spectrophotometer. Small changes in standard solution pH (4.1–5.2) and chrome azurol S concentration did not affect the analysis. The cyan channel image analysis was proportional to the Al3+ solution concentration (y=25 019x+1489, R2=0.9554 within 2.5–8 μg/ml). The detection limit for aluminium by the visual test method is about 1 μg/ml, and fading is absent. The cyan channel image analysis method is independent of the observer and is applicable for the evaluation of the chemical purity of 99Mo/99mTc generator eluates. Our colorimetric ‘spot test’ is advantageous for the visual evaluation of Al3+ pertechnetate concentrations as required by Ph. Eur. showing a sensitivity and a limit of detection superior to that of commercially available spot systems.

Nuclear Medicine Unit, IRCCS San Matteo Hospital Foundation, Pavia, Italy

Correspondence to Lorenzo Lodola, PhD, Nuclear Medicine Unit, IRCCS San Matteo Hospital Foundation, viale Golgi, 19-27100 Pavia, Italy Tel: +39 0382 501639; fax: +39 0382 501661; e-mail: l.lodola@smatteo.pv.it

Received February 21, 2014

Accepted February 24, 2014

© 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins