Nonspecificity of Urinary Lead Measurements by Atomic Absorption Spectroscopy

Lead measurements by direct AAS at 217 nm on a pooled urine sample gave values of 57 µg/l by the method of standard additions. In contrast, dithizone procedures gave values of 15-20 µg/l. Studies demonstrated that various urine salts and organic compounds contributed to the absorbance at 217 nm. These native urine materials also give a similar absorbance value at 220 nm, a line not related to lead emitted by the lead hollow cathode tube. Thus, correction of the nonlead absorbance was possible by subtracting the A220 from A217. Utilizing this correction, the standard addition procedure gave values of 12 µg/l. The correction technic was also applied to the lead isolation-concentration technic of Kopito and Shwachman (3) which employs bismuth coprecipitation. The simplicity of operations, increased sensitivity and reproducibility obtained by coupling the AAS correction technic with bismuth coprecipitation recommends it as a method for serious consideration.

Regularities and anomalies in the isotope shifts in the arc spectrum of barium

The isotope shifts in the lines 3072 and 3501 Å of the arc spectrum of barium have been determined from measurements of differences of the wavelengths of these lines emitted by enriched isotopes in a hollow cathode tube. A revision of earlier measurements of the shifts in the line 5536 Å has been made on the basis of measurements made with atomic beams and with the hollow cathode tube with more highly enriched isotopes. The shifts, relative to the isotope 138 (measured in millikaysers-10 -3 cm -1 ) are: 137 136 135 134 132 130 5536 Å 7.0 4.1 8.1 4.6 6. 3 7. 2 3072 Å 6. 5 3. 3 7. 8 4. 1 3. 0 3. 8 3501 Å 7. 0 3. 7 8. 5 2. 0 4. 1 -2. 7 It is shown that when the volume shifts and the mass shifts are separated, the anomalous distribution of the shifts disappears in the case of the isotopes of even mass number, but an unusually large staggering of the shifts of the odd isotopes remains.

Isotope shifts in the NdI spectrum

Isotope shifts in about fifty lines of the Nd I spectrum emitted by a hollow cathode tube, in the region 5200 to 6000 Å, have been recorded on a Fabry-Perot spectrometer equipped with a photoelectric detector. The results are used to examine the existing classification of the spectrum . The structure of the line 5525-7 Å suggests the inversion of the odd-even staggering phenomenon for 143 Nd.