reason, thin layer chromatography was adopted as the standard procedure. A solution of phosphomolybdic acid followed by ammonia is used as the color developer. With this method, it is possible to isolate and identify phenolic antioxidants present in polyethylene in concentrations as low as 1 p.p.m. At present this technique has been applied primarily to the identification Of phenolic-type antioxidants in polyethylene;
however, preliminary indications are that it can be applied to the analysis of antioxidants in other polyolefins. LITERATURE CITED
(1) Dehority, B. A,, J. Chromatog. 2,384-
387 (1959). (2) Luongo, J. P., ANAL.CHEM.33, 1817 ( 1961 ). (3) Mitchell, L. c., J. A S S O C . OflC.Agr. Chemists 40, 909 (1957). (4) Schmidt, J. J. E., Bonomo, F. S., “Development of Schematic Analytical
Procedures for Synthetic hbricants and
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RECEIVEDfor review June 3, 1963. Accepted February 19, 1964. Presented at Southeastern Regional Meeting, ACS, Gatlinburg, Tenn., Nov. 1-3, 1962.
Rapid Spectrophotometric Method for the Determination of Lead in Bone Ash FRANK H. ILCEWICZ, RICHARD B. HOLTZMAN, and HENRY F. LUCAS, Jr. Radiological Physics Division, Argonne National laboratory, Argonne, 111.
b The measurement of the absorbance of the chloro-complex of lead(ll) in 9M hydrochloric acid at 271 mp provides a simple and rapid method for the analysis of microgram quantities of lead in bone ash. Interfering ionse.g., iron(ll1) and copper(l1)-were removed by extraction with triiso-octylamine. The effect of the concentration of hydrochloric acid and calcium phosphate (bone ash) on the absorbance was studied. The optimum experimental condition was attained when bone ash was dissolved in 9M hydrochloric acid at a concentration of 0.2 gram ash/ml. of acid. Beer’s law was obeyed for lead concentrations up to 16 pg./ml. The sensitivity was 0.1 pg./ml. and the standard error for calcium phosphatelead standards was 3=270. The procedure has been used for determinaticns of lead in samples of bone ash in which the concentrations ranged from 6 to 80 p.p.m.
T
of a simple and accurate method for the determination of lead in bone specimens is extremely important in view of the high toxicity of the element and its wide distribution. It is also important for studying the metabolism of the element and comparing its distribution to that of lead-210, a decay product of radium226, in the human skeleton, which has already been studied in this laboratory (4,5). Lead is found in all tissues and fluids of the body and its distribution has been investigated extensively by many workers. For bone samples, spectrographic (IO), polarographic ( I ) , and colorimetric (7‘) methods have been employed for its determination. The HE DEVELOPMENT
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ANALYTICAL CHEMISTRY
cupric, mercuric, and stannic chlorides, bismuth trioxide, cadmium, and thallous nitrates, and tellurium, and zinc metals in 9M HC1. The amount of nitrate introduced in the thallium and cadmium studies was assumed t o be insignificant. DIETHYLAMNONIUM SALT OF DIETHYLDITHIOCARBAMATE (DDC). One gram of DDC was dissolved in 100 ml. of chloroform. TRIISO-OCTYLAMINE (TIA). A 20% v./v. solution of TIA was prepared in chloroform and washed twice with equal volumes of 9M HCl. CHLOROFORM. All chloroform used to wash reference and sample solutions was equilibrated twice with equal volumes of 9M HC1. REFERENCE SOLUTION.One hundred milliliters of 9M HC1 was extracted three times with 5 ml. of TIA and washed three times with 5 ml. of chloroform. CALIBRATION SOLUTION.(0.20 gram of Pb-free synthetic bone salts per ml. of 9M HC1.) Lead-free synthetic bone solution was prepared by extraction of Reagent Grade calcium phosphate with 1% DDC in chloroform (7). It was then evaporated to dryness and ashed overnight a t 620’ C. in a Vycor beaker to remove any residual organic material. The ash was dissolved in 9M HC1. Any residual carbonaceous material was removed by filtering through a previously washed glass-fiber filter. The EXPERIMENTAL solution was brought to a voiume calculated to give a concentration of 0.20 gram of Caa(POa)aper ml. of 9-If HC1. Spectrophotometers. The measureThis solution (100 ml.) was then exments were made on a Perkin-Elmer, tracted three times with 5 ml. of 20% Model 350 recording spectrophotomTIA and three times with 5 ml. of eter and a Beckman DU spectrochloroform. The absorption spectrum photometer with 1.0-cm. silica cells. Reagents. STANDARD SOLUTIONS. of the solution showed no detectable amounts of lead (
