Kunnath S. Subramanian

Determination of arsenic(III), arsenic(V), antimony(III), antimony(V), selenium(IV) and selenium(VI) by extraction with ammonium pyrrolidinedithiocarbamate—methyl isobutyl ketone and electrothermal atomic absorption spectrometry

Abstract The solution conditions and other parameters affecting the ammonium pyrrolidine-dithiocarbamate—methyl isobutyl ketone extraction system for graphite-furnace atomic absorption spectrometric determination of As(III), As(V), Sb(III), Sb(V), Se(IV) and Se(VI) were studied in detail. The solution conditions for the single or simultaneous extraction of As(III), Sb(III) and Se(IV) were not critical. Arsenic(V) and Se(VI) were not extracted over the entire range of pH and acidity studied. Antimony(V) was extracted only in the acidity range 0.3—1.0 M HCl. Simultaneous extraction of total arsenic and total antimony was possible after reduction of As(V) with thiosulphate. Interference studies are also reported.

Removal of trace mercury(II) from drinking water: Sorption by granular activated carbon

Abstract Optimum conditions were established for abstracting μg/L levels of Hg(II) species from aqueous solution and drinking water using the FS‐400 granular activated carbon (GAC) as adsorbent. The conditions were: system pH around 7, GAC suspension density of ≥100 mg/L, and a mixing or contact time of 1 h. Uptake of Hg(II) increased in the presence of 1–10 mg/L of humic acid, nitrilotriacetic acid (NTA) or Fe(III) salts; was little affected by Al(III) salts; and decreased when Ca(II) and Mg(II) levels exceeded 50 mg/L. The amount of Hg(II) adsorbed per unit weight of GAC varied with the initial concentration of Hg(II) until saturation was achieved. Under optimum conditions, the residual Hg(II) levels were below the maximum acceptable concentration (MAC) values given in the Guidelines for Canadian Drinking Quality.

Leaching of antimony, cadmium, copper, lead, silver, tin and zinc prom copper piping with non‐lead‐based soldered joints

Abstract Studies were done on the leaching of Ag, Cd, Cu, Pb, Sb, Sn and Zn from 95/5 Sn/Sb‐, 96/4 Sn/Ag‐, 94/6 Sn/Ag‐, and 95.5/4.0/0.5 Sn/Cu/Ag‐soldered copper pipes into high‐purity, tap, and well water samples as a function of standing time in a static test on new plumbing. There was no significant leaching of Ag, Cd, Pb, Sb and Sn from the above solders into the three types of water samples studied. The amount of Cu released from soldered copper pipes was lower than that released from non‐soldered copper pipes. The amount of Zn leached from the non‐Pb‐based solders studied was well below the Guidelines (<5 mg/1) for Canadian drinking water guality. Since the potential for public health hazard from Pb‐based solders in plumbing systems is significant, it is advisable to use these Pb‐free’ solders.

Determination of tin in lead/tin solder leachates from copper piping by graphite platform furnace atomic-absorption spectrometry

A stabilized-temperature platform furnace/atomic-absorption spectrophotometric(STPF-AAS) method has been developed for the determination of tin leached from lead/tin-soldered copper pipes. The method involves the use of a modifier composed of diammonium hydrogen phosphate, magnesium nitrate and nitric acid. Aqueous tin standards in the composite matrix modifier are used for calibration. The characteristic mass and detection limit (three standard deviations of the blank) for peak-height measurement of tin are 5 pg and 1.7 microgl., respectively. The corresponding peak-area values are 26.8 pg and 12.8 microgl., respectively. The accuracy, precision, and interferences (especially of sulphate) have been assessed.

Adsorption of low levels of lead(II) by granular activated carbon

Abstract Factors influencing the adsorption of μg/L levels of lead(II) from solution by granular activated carbon have been investigated. Uptake varied nearly linearly with adsorbent density at loadings ≤ 100 mg/L, but changed gradually to a fractional power term of 0.25 at loadings ≥ 1 g/L to achieve a 95% removal. An agitation period of at least 5 h was required for the establishment of pseudo‐equilibrium conditions. The amount of lead(II) adsorbed varied with pH and optimum removal occurred at pH > 8. The adsorption process was inhibited by the presence of humic acid, iron(III) and aluminum(III) at levels 2–8 mg/L; by calcium(II) at 100 mg/L; and by polyphosphate at 10 mg/L. Addition of nitrilotriacetic acid and ethylenediaminetetraacetic acid caused an enhancement in the amount of lead(II) removed from solution. The presence of Mg(II) at 100 mg/L, and chloride and sulphate at 200 mg/L each, had no significant effect on lead(II) sorption by granular activated carbon. The processes responsible for the s...

Bone-lead analysis: development of analytical methodology for milligram samples.

A graphite platform-in-furnace atomic absorption spectrometric (GFAAS) method for determining μg/g levels of Pb in 10–20 mg cortical and trabecular primate bone samples is described. The GFAAS method is based on an ambient temperature nitric acid digestion of the sample, matrix modification with palladium nitrate, stabilized temperature platform furnace atomization, and a systematic evaluation of the temperature program of the atomizer. The method of standard additions is mandatory. The detection limit (3 standard deviations of the blank) is 0.19 μg Pb/g dry weight for a 10-mg sample taken up in a 1-mL volume. Data are presented on the degree of accuracy and precision. The accuracy of the proposed GFAAS method has been assessed using the IAEA bone reference material, H-5, and by comparing the values obtained in a bone sample with an isotope dilution mass spectrometric (IDMS) procedure. The GFAAS method can be applied to the determination of Pb in 10–20 mg bone samples and for concentrations which are ≥10 × detection limit. The method is simple, fast, and contamination-free since the entire operation from weighing to GFAAS measurement is carried out in the same centrifuge tube. The method has been applied to the determination of total-Pb in some adult and fetal primate cortical and trabecular bone specimens.

Hemolyzed, lyophilized bovine blood for quality control of lead determination of human whole blood

The determination of Pb in human whole blood is perhaps the most common application of biological monitoring in occupational and environmental health. However, the lack of an adequate reference material has prevented a thorough evaluation of current analytical methods for Pb in blood and hence the evaluation of data generated by using such methods. As a result the concentration of Pb in human whole blood is not accurately known. In this paper the authors report the preparation and analysis of two freeze-dried bovine whole blood reference specimens containing two different levels of Pb.

Removal of trace cadmium(II) by EDTA‐coated granular activated carbon

Abstract The factors influencing the uptake of trace cadmium by an ethylenediaminetetraacetate‐coated granular activated carbon (ECGAC) have been examined and optimum conditions determined. Variables investigated include agitation time, adsorbent dose (or suspension density), Cd(II) concentration and pH. At a substrate suspension density of 200 mg/L, pH of 5.4 and an agitation time of 18 h, uptake was approximately 90% from a solution of 25 μg Cd(II)/L. In comparison, the amount sorbed by uncoated granular activated carbon of 1.0–1.4 mm size fraction under the same conditions was only 5%. The maximum sorption capacity of ECGAC was about 0.4 mg Cd(II)/g (i.e., 3.6 μM/g). Under optimum conditions, it is possible to lower the Cd(II) level to below the maximum acceptable concentration of 5 μg/L specified in the Guidelines for Canadian Drinking Water Quality.

Effect of container material, storage time and temperature on determinations of cadmium levels in human urine

The effect of container material (polyethylene, polypropylene, polystyrene, borosilicate glass and flint glass), storage time (0-86 days), and temperature (22 degrees and 4 degrees ) on the cadmium content found by graphite-furnace atomic-absorption spectrometry for spiked and unspiked urine samples has been studied. No loss of cadmium occurred for at least 10 and 28 days when unspiked and spiked samples respectively, were stored in polyethylene containers at 22 degrees . For storage up to 3-4 days at 22 degrees , polypropylene, polystyrene, borosilicate glass and flint glass containers were also found suitable. Storage at 4 degrees was not effective in preventing loss of cadmium.