Application of Internal Standardization to Rapid Coprecipitation Technique Using Lanthanum Phosphate for Flame Atomic Absorption Spectrometric Determination of Iron and Lead

Abstract

Experimental ApparatusA Hitachi 170-50 atomic absorption spectrometer with an iron, lead, or indium hollow-cathode lamp (Hitachi or By applying an internal standardization, we could use a rapid coprecipitation technique using lanthanum phosphate as a coprecipitant for preconcentration of iron(III) and lead in their flame atomic absorption spectrometric determination. Indium as an internal standard was added to the initial sample solution together with lanthanum and phosphoric acid; the coprecipitation of iron(III) and lead was then carried out at pH about 3. After measuring the atomic absorbances of iron, lead, and indium in the final sample solution, we determined the contents of iron(III) and lead in the original sample solution by using the internal standardization with indium. In this method, complete collection of the precipitate was not required after the coprecipitation of iron(III), lead, and indium, because the ratio of the recovery of iron(III) or lead to that of indium was almost constant regardless of the recovery of the precipitate. This method was simple and rapid, and was available for the determination of 2 -300 µg L -1 of iron(III) and 5 -400 µg L -1 of lead in some water samples.

Determination of Cadmium in River Water by Electrothermal Atomic Absorption Spectrometry after Internal Standardization-Assisted Rapid Coprecipitation with Lanthanum Phosphate

“…For dissolution of the precipitate, nitric acid was chosen because of the small influence on the atomic absorbance of cadmium; 2 almost a constant atomic absorbance was obtained over a wide acid-concentration range of 0.8 -3.2 mol L -1 in the final solution. A centrifugation using a 50 mL centrifuge tube or a Nalgene 175 mL polystyrene conical centrifuge bottle at 3500 rpm for 10 min was conveniently utilized for collecting the precipitate 17,18 after the supernatant solution was discarded by decantation.…”

“…Although the lanthanum used as the carrier element in this method was difficult to determine by electrothermal atomic absorption spectrometry, the amount of lanthanum in the final solution could be estimated by measuring the indium used as the internal standard. 18 The collected precipitate could be readily dissolved by using 1 mL of more than 2.4 mol L -1 nitric acid. The volume of the final solution dissolving the precipitate was varied around slightly exceeding 1 mL, since the supernatant solution could not be completely discarded after centrifugation.…”

“…We have proposed a rapid coprecipitation technique [15][16][17][18] to simplify the operation in coprecipitation. In this technique, a known amount of the carrier element is used for the coprecipitation of the desired metal; the amounts of the coprecipitated metal and the carrier element in the final solution are then determined.…”

“…Although the requirements, especially 1) and 4), restricted the carrier element used in the rapid coprecipitation technique, this problem could be solved by applying internal standardization. 18 When the internal standard, which can fill requirements 1) -4) instead of the carrier element, was used, the coprecipitant did not need to satisfy the requirements.…”

“…In this work, we found that the rapid coprecipitation technique with lanthanum phosphate using the internal standardization 18 was useful for the preconcentration of cadmium in an electrothermal atomic absorption spectrometric determination; the cadmium content in the original sample solution could be determined by coprecipitation with lanthanum phosphate 19 in a sample solution spiked with indium as the internal standard and measurements of both the cadmium and indium in the final solution using electrothermal atomic absorption spectrometry. The proposed method is simple and rapid, and enrichment close to 200-times can be readily attained.…”