Walter Slavin

A rapid Zeeman graphite furnace atomic absorption spectrometric method for the determination of lead in blood

A method is described for the rapid determination of lead in blood. About 100 samples are processed in a 7.5-h shift, with two replicate injections per sample. Whole blood, obtained either by venipuncture or fingerstick, is diluted 1:10 in a phosphate matrix modifier containing Triton X-100 and dilute nitric acid, and 12 μl of the diluted blood is deposited in the graphite furnace. An entire cycle is completed every 90 s. Aqueous standards in the matrix modifier are used for calibration. The within-run standard deviation is typically about 0.25 μgdl at low concentrations, indicative of very good precision. Considerable amounts of data using various reference materials are provided establishing the accuracy of the method to better than 1 μgdl at low concentrations (c. 10 μgdl) of blood lead. The speed and precision of the method is made possible by the use of the new transversely heated graphite furnace with a longitudinal Zeeman field background correction system.

The Determination of Trace Elements in Natural Waters Using the Stabilized Temperature Platform Furnace

We have developed procedures to determine 12 trace elements, Al, As, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, and V, in natural water using the stabilized temperature platform furnace. Suitable matrix modifiers were tested. Confirmation of the techniques was obtained by recovery experiments at four different concentration levels. Only simple aqueous standards were required and the method of additions was not used. A simple recovery experiment was satisfactory confirmation of freedom from chemical interferences. The detection limits in the natural waters were less than 1 μg/liter, closer to 0.1 μg/liter for most of the elements. The precision was 10 to 15%. The work did not require clean-room facilities.

Graphite Furnaces as Atomizers and Emission Sources in Analytical Atomic Spectrometry

I. THE ROLE OF ATOMIZERS IN ANALYTICAL ATOMIC SPECTROMETRY During the last 2 decades, a large variety of procedures for analytical atomic spectroscopy have been developed. This was a result of the need for more and more sensitive and precise methods of trace analysis in various fields of application. Most of the thinkable versions of combinations of the essential parts of the spectrometric arrangements have now been tried out, at least from the theoretical point of view, and often also experimentally. But there are still some possibilities left to form new setups for analytical purposes. This was especially promoted by the advent of tunable lasers as very intense, coherent, and spectrally narrow band radiation sources1. Spectroscopic methods originally devoted to fundamental physical or chemical studies have often been exploited as efficient tools for analytical purposes. This fruitful interaction between fundamental and applied research in atomic spectroscopy was recently analyzed by Alkemade2

Determination of selenium in biological materials with platform furnace atomic-absorption spectroscopy and Zeeman background correction

The presence of phosphate and iron provides a spectral interference for the determination of selenium at its primary resonance line at 196.0 nm that is avoided by using Zeeman background correction. Good quality pyrolytic graphite tubes, platform atomisation and integrated absorbance readings provide an acceptable quantitative environment for selenium and permit most analyses to be performed against a simple calibration graph using selenium in a nickel matrix modifier. Remaining problems appear to relate to loss of selenium prior to atomisation in the presence of certain matrices, notably the combination of sodium and sulphate. Charring in the presence of oxygen did not improve the analytical situation, nor did the use of silver, molybdenum or copper as a matrix modifier. We found a 2σ detection limit of 28 pg and a sensitivity of about 25 pg per 0.0044 As (A = absorbance units), expressed as characteristic amount. A preliminary direct method is presented for selenium in urine, with nickel, nitric acid and magnesium nitrate present, with a detection limit in urine of about 10 µg 1–1.

Reduction of temperature variation in the atomic absorption graphite furnace

Abstract The temperature variation that is experienced along the length of the graphite furnace tube of the Massmann design can be reduced by the use of a contoured tube. An analytical model of the steady-state temperature distribution along the graphite tube has been developed and has been shown to agree quite well with experimental data. Steady-state and time-dependent measurements along the length of the graphite tube are reported for different conditions. With conventional tubes at thermal equilibrium, there is a temperature difference exceeding 1000°C between the center and the ends when the center of the tube is at 2500°C. With a contoured tube this temperature gradient has been reduced to 100°C.

A low-cost tungsten filament atomizer for measuring lead in blood by atomic absorption spectrometry

Abstract A low-cost electrothermal atomic absorption spectrometry (AAS) system based on a tungsten filament atomizer is proposed for the measurement of blood lead. Preliminary experiments have been carried out using a tungsten filament enclosed in a glass cell, purged with argon and 10% H 2 , and mounted on the optical bench of a commercial atomic absorption spectrometer with continuum background correction. The tungsten filament is ballistically heated with a 12 V d.c. power supply. A number of parameters, including filament position, gas flow, drying, pyrolysis and atomization steps, are optimized specifically for blood lead. Peak absorbance is the measurement mode used because of the very fast signals observed. The atomizer is calibrated with aqueous lead standards, and the calibration verified by analyzing blood lead reference materials from NIST, CDC and NYS, that cover the clinical range for blood lead (5–54 μg dl −1 ). Results below 40 μg dl −1 are within ±2 μ g of the certified value, and within ±10% of the certified value above 40 μg dl −1 , indicative of good accuracy especially at the lower blood lead levels. Blood is prepared by diluting 1 + 9 with modifier. Ten microliters of diluted blood is deposited on the filament using a micropipet. Forty-two human blood specimens covering the range 3–31 μg dl −1 are analyzed in parallel with a well established graphite furnace AAS method. There is good agreement between the two AAS methods, and the differences between individual paired blood lead results are less than ±4 μ g. The sensitivity or characteristic ( m o ) of the tungsten filament atomizer is 26 pg, and the method detection limit (3 SD) is about 2 μg dl −1 .

Rapid slurry analysis of solid coal and fly ash samples

Abstract Coal and coal fly ash samples were analyzed as solid slurries. These preliminary experiments used fast sampling STPF procedures which omitted the pyrolysis step and the matrix modifier. The experiments also used an ultrasonic mixing device that automatically stirred the suspension just before the autosampler probe withdrew the aliquot which it would dispense onto the platform. The combination of these techniques made it possible to reduce the analytical time to less than 1 min per sample. Simple aqueous standards were used for calibration. The NIST SRM 1633a Coal Fly Ash was successfully analyzed for As, Pb and Tl, with results for Se in this material that suggested that more work was required to gain confidence in the determination. The SRM 1632a Coal was successfully analyzed for As and Pb. The methods were the same for both materials. A few mg of the dry solid powder was weighed directly into the autosampler cup followed by a weighed amount (about 1.5 ml) of suspending diluent The characteristic mass was calculated from several aliquots of simple aqueous standards and this value was used to calculate the amount of analyte delivered to the furnace. In the work reported here the detection limits for the elements determined were about 0.5–1 μg g in the solid sample. With further experience these limits may be improved. The precision for replicates of slurries from the same cup varied from 2 to 10% depending upon the amount of solid sample delivered to the furnace.

Amino Acid Profiling of Protein Hydrolysates Using Liquid Chromatography and Fluorescence Detection

Abstract A liquid chromatography procedure is described for separating the amino acids in protein hydrolysates. The proteins are hydrolyzed with hydrochloric acid and an aliquot of the hydrolysate is derivatized with dansyl chloride reagent. The derivatization procedure takes only 2 minutes using a reaction temperature of 100°C. The dansylated amino acids are chromatographed using a reversed-phase C8 column and a multi-step, nonlinear gradient elution solvent program which is readily achieved using a microprocessor-controlled liquid chromatograph. Chromatography is complete in approximately 40 min. The procedure is useful for characterizing proteins and may also be used to analyse intact dansylated polypeptides. Chromatograms showing the amino acid profile of chymotrypsin, albumin and histone are given.

Atomic-Absorption Spectroscopy— a Critical Review

Atomic-absorption spectroscopy is reviewed as an analytical technique. The effect of recent instrumental advances on analytical procedures is reported. It is now possible to determine every metal and semimetal for which lamps have been made. Analytical procedures by atomic absorption are generalized and limitations of the technique stated. The various instrumental techniques for metal analysis are compared to show for what purposes atomic absorption is useful. Applications in various analytical fields are mentioned briefly.

Graphite-tube effects on perchloric acid interferences on aluminum and thallium in the stabilized-temperature platform furnace

Abstract The determination of aluminum in the presence of perchloric acid is shown to depend upon the quality of the pyrolytic coating of furnace tubes. With new pyrolytically coated tubes, no interference was found from 0.5 M HClO4 on 0.5 ng Al and no decrease in signal or deterioration of the pyrolytic coating was found after more than 150 firings. Very little interference was found in the determination of thallium in perchloric acid. In both cases the literature reported severe interferences. The determination of thallium and aluminum in perchloric acid appears to be more sensitive to the quality of the pyrolytic graphite coating than any of the materials studied previously here.