Determination of lanthanides and yttrium in rocks and minerals by atomic-absorption and flame-emission spectrometry

The sensitivity of atomic-absorption and flame-emission determination of lanthanides and yttrium is improved by a factor of 2-5 when an absolute ethanol solution of the perchlorate of the metal (instead of an aqueous solution) is aspirated into a nitrous oxide-acetylene flame. Based on this, a method has been developed for accurate determination of small amounts of certain rare earths and yttrium. Lanthanum (1%) is used as a spectroscopic buffer to eliminate interferences and to enhance the sensitivities in certain determinations. Where the use of lanthanum is not practicable because of interferences (such as in the determination of praseodymium and samarium by flame emission), sodium (2000 ppm) is used as the spectroscopic buffer. Studies with synthetic solutions indicate that yttrium and most lanthanides can be directly determined in minerals without any chemical separation. With rock samples it is necessary to preconcentrate the traces of the rare earths by fluoride or oxalate precipitation with calcium as the carrier, followed by removal of calcium by hydroxide precipitation using mg amounts of iron as the carrier. The method developed has been applied to the determination of certain lanthanides and yttrium in a variety of rocks, including the Canadian reference rocks, syenites SY-1, SY-2 and SY-3, and some minerals such as britholite, cenosite, chevkinite, allanite, apatite and sphene.