Determination of nickel in urine with graphite furnace AAS using Zeeman correction.

We have developed a rapid and direct method for determining urine nickel. The urine specimen is diluted (1 + 1) with 2.0% v/v nitric acid and 0.001% v/v Triton X-100 and absorbance measurements are made with Zeeman-effect graphite furnace atomic absorption. The method is sensitive enough to be used to evaluate "normal" subjects for baseline studies or to evaluate environmental or other nonoccupational exposure to nickel. The characteristic mass (pg/0.0044A.s) is 26 pg, which is comparable to that obtained for aqueous solutions. The observed absorbance is linear up to about 100 micrograms l-1, after which the calibration curve departs from linearity. Procedures are described to rigorously exclude nickel contamination. We evaluated precision and accuracy with a U.S. National Bureau of Standards urine reference material. SRM 2670, with an informational nickel value of 70 micrograms l-1, and with a multielement water reference material, SRM 1643b, with a certified nickel value of 49 ng g-1. Within- and among-run standard deviations for SRM 2670 were calculated to be 9.0 and 2.45 micrograms l-1, respectively, and 2.1 and 1.1 micrograms l-1 for SRM 1643b. The detection limit, calculated as 3 SD of a "low" concentration urine, is about 1.1 micrograms l-1. The proposed method was applied to the determination of nickel in urine of 258 workers in a magnet manufacturing plant, and the data obtained support the usefulness of urine nickel for biological monitoring.

Simultaneous quantification of erythrocyte zinc protoporphyrin and protoporphyrin IX by liquid chromatography.

A simple, rapid, specific, and sensitive isocratic "high-performance" liquid-chromatographic procedure is described for measuring protoporphyrin (PPIX) and zinc protoporphyrin (ZPP) in erythrocytes. A 30-microL whole-blood sample is treated with a solution of formic acid, deproteinized with acetone, and centrifuged. A 20-microL aliquot of the supernate is injected into a system consisting of a stationary phase of mu-Bondapak C18 and a mobile phase of acetone, methanol, water, and formic acid. ZPP and PPIX are detected fluorometrically (lambda ex = 417 nm, lambda em = 635 nm) within 6 min. The range of linearity extends beyond 10 mg/L for ZPP and 580 micrograms/L for PPIX. The detection limits for ZPP and PPIX are 11.9 micrograms/L (6.93 pg) and 2.55 micrograms/L (1.485 pg), respectively. The precision for ZPP and PPIX determinations averaged 2.86 and 5.59%, respectively, for within-day CVs and 4.98 and 8.14, respectively, for among-day CVs. Analytical recoveries averaged 97.2% for ZPP and 101.5% for PPIX. Interferences in the form of fluorescent quenching of ZPP and PPIX by hemin are avoided by chromatographic separation. We also used this method to determine the purity of commercially prepared ZPP, and compared the results obtained with this method with those from an extraction method.

Determination of thallium in urine with Zeeman effect graphite furnace atomic absorption.

Thallium is determined in urine with a simple dilution as the only sample pretreatment. Zeeman effect background correction provides adequate accommodation for non-atomic absorption such that sufficient diluted urine can be introduced into the furnace to achieve a detection limit of 0.5 ng/mL. Precision and accuracy were evaluated with Environmental Protection Agency water samples and in vitro spiked urine pools; precision of 15% at the 6 ng/mL level was observed. Diluted urine was used in calibration, with only 4 to 5% difference in slope observed within run among randomly selected urine specimens.