Chlorophosphonazo-m-NO~2 (CPAmN) and Its Application in Spectrophotometric Determination of Rare Earths

Chlorophosphonazo-m-NO_2 is proposed as a chromogenic reagent for spectrophotometric determination of cerium sub-group rare earths, yttrium, and total rare earths under different conditions. Cerium sub-group rare earths can be determined in the presence of yttrium subgroup elements by using oxalic acid as a masking reagent. A prior PMBP-petroleumether extraction is required for complex samples. Yttrium, in the presence of cerium sub-group rare earths, should be separated before determination by the combination of masking with sodium flouride-malic acid mixture and an extraction procedure. As for the total rare earths determination, the addition of oxalic acid is omitted, but the pre-extraction with PMBP-petroleum ether is usually necessary.