Estimation of Standards for Gold and Silver Sampling

Abstract

U protetskoj se terapiji upotrebljava vrlo mnogo plemenitih slitina različita sastava. Plemeniti metali su sinonim za biokompatibilnost. Zlato je jedna od najinertnijih plementih kovina, a srebro jedna od najreaktivnijih. Cilj rada bio je razvijanje i raščlamba kromatografskih mrlja čistoga zlata i srebra (Aurodent, Celje, Slovenija). Kovine su uzorkovane na sobnoj temperaturi otopinom voda-HCl(conc.) (v/v 10:1) tijekom 10 s pri stalnom naponu struje od 4,5 V. Otopine kationa iz čistih kovina i 10 µl standardnih otopina soli nanesene su na HPTLC kromatografske ploče (Merck, Darmstadt, Njemačka) 10 x 10 cm presvučene celulozom. Ploče su razvijene u staklenoj kromatografskoj komori zasićenoj mobilnom fazom izo-amilni alkohol: HCl(conc.) : acetonitril u omjeru 5,4 : 4,3 : 0,3 do visine od približno 8 cm. Kada su razvijene sušene su u struji vrućega zraka, a kationi su vizualizirani prskanjem zasićenim etanolnim otopinama difenilkarbazida, alizarina, kvercetina te 0,1% otopinom ditizona u kloroformu. Nakon prskanja i sušenja ploče su izložene parama amonijaka i učinjena je vizualizacija. Uzorkovano zlato i srebro međusobno se razlikuje bojom kromatografskih mrlja i utvrđenim Rf vrijednostima. Metodom anodnoga uzorkovanja slitina i identifikacijom kationa tankoslojnom kromatogafijom moguće je dokazati postojanje određenih kationa s udjelom mase većim od 1%, ne oštećujući pritom sam uzorak. Metoda se pokazala prikladnom za uzorkovanje kovina zlata i srebra, što je nastavak dosadašnih istraživanja u identifikaciji određenih sastavnica u pojedinim slitinama ili u inkorporiranome protetskom radu.Different precious dental alloys are used in prosthodontic therapy. Precious metals are the synonym for biocompatibility. Gold is one of the most inert and silver the most active presious metals. The purpose of this study was to develop an analyze the chromatographic spots of pure gold and silver (Aurodent, Celje, Slovenia). The sampling was performed in a water-HCl(conc.) solution in a 10 : 1 volume ratio at room temperature using a 4,5 V battery. Dissoluted cations and solutions of standard elements (salts of gold and silver) were applied to HPTLC plates (Mareck, Darmstadt, Germany) 10 x 10 cm precoated with cellulose. Plates were developed in a vertical separating chamber to a height of approximately 8 cm saturated with iso-amyl (3.methyl-1-butanol) - HCl (36,5%) - acetonitrile in a volume ratio 5,4 : 4,3 : 0,3. After development, plates were dried in (a steam of) hot air and the cations were visualized by spraying with the saturated ethanolic solutions of alizarin, diphenylcarbazide, quercetin and 0,1% chlorophorm solution of dithizone. After drying, plates were exposed to NH3 vapor. According to the Rf value and the color of the spots, the difference between gold and silver were obtained. Anodic sampling with thin-layer chromatography is a suitable, nondestructive method for identification of cations presents in different dental alloys. It is possible to identify the cations with their mass ratio W > 1%. The results have shown that the described method is suitable for analysis of gold and silver and it can be used in future work to identify those cations in dental alloys of unknown composition