Determination Of Lead In Urine Research Articles

Determination of Lead in Urine by Slotted Quartz Tube (SQT) – Flame Atomic Absorption Spectrometry (FAAS) Following Preconcentration by Dispersive Liquid Phase Microextraction (DLLME)

This study was aimed to develop a sensitive and accurate method for the determination of lead in urine. Dispersive liquid-liquid microextraction (DLLME) was applied prior to slotted quartz tube – flame atomic absorption spectrometry (SQT-FAAS). Dithizone was employed in generating water-insoluble forms of lead to isolate the analyte in the microextraction. All variables having a direct effect on extraction and instrumental outputs were systematically optimized. The detection limit was 0.5 µg L−1 which indicates a 305-fold enhancement compared to conventional FAAS. The wide linear range is between 2.0 and 250 µg L−1 with a high regression coefficient (0.9998). Urine samples were used in order to examine the practical application of the developed method. The recovery values were between 98.2 and 107.0%.

Multivariate optimization of the hollow fiber-based liquid phase microextraction of lead in human blood and urine samples using graphite furnace atomic absorption spectrometry

The present study developed a liquid-phase microextraction based on hollow fiber coupled with graphite furnace atomic absorption spectrometry for the effective extraction and quantitation of lead from urine and blood samples. A multivariate design was used for the optimization of the experimental conditions to ensure high extraction efficiency. Six factors (solvent type, chelating agent, time extraction, temperature, donor phase pH, and acceptor phase pH) were obtained by screening eleven factors of the Plackett–Burman design; these were optimized using the central composite design of response surface methodology. The optimum conditions of donor phase pH, acceptor phase pH, temperature, and extraction time were 5, 9.5, 40 °C, and 120 min, respectively. In addition, oleic acid containing dicyclohexyl-18-krone-6 was used for the membrane phase. Under optimal conditions, the enrichment factor, limit of detection, and limit of quantification were obtained in the ranges of 21.3–18.7, 0.001–0.002 ng mL−1, and 0.008–0.01 ng mL−1, respectively, in urine and blood samples. The linearity of the calibration curve was established for the concentration of Pb in the range of 1–50 ng mL−1 (r2 = 0.9983). Finally, the performance of the developed method was evaluated for the determination of lead in urine and blood samples, and satisfactory results were obtained (RSDs 95).

Multiwalled carbon nanotubes as a sorbent material for the solid phase extraction of lead from urine and subsequent determination by electrothermal atomic absorption spectrometry

The determination of lead in urine is a way of monitoring the chemical exposure to this metal. In the present paper, a new method for the Pb determination by electrothermal atomic absorption spectrometry (ETAAS) in urine at low levels has been developed. Lead was separated from the undesirable urine matrix by means of a solid phase extraction (SPE) procedure. Oxidized multiwalled carbon nanotubes have been used as a sorbent material. Lead from urine was retained at pH4.0 and was quantitatively eluted using a 0.7M nitric acid solution and was subsequently measured by ETAAS. The effects of parameters that influence the adsorption–elution process (such as pH, eluent volume and concentration, sampling and elution flow rates) and the atomic spectrometry conditions have been studied by means of different factorial design strategies. Under the optimized conditions, the detection and quantification limits obtained were 0.08 and 0.26μgPbL−1, respectively. The results demonstrate the absence of a urine matrix effect and this is the consequence of the SPE process carried out. Therefore, the developed method is useful for the analysis of Pb at low levels in real samples without the influence of other urine components. The proposed method was applied to the determination of lead in urine samples of unexposed healthy people and satisfactory results were obtained (in the range 3.64–22.9μgPbL−1).

Assessing state-of-the-quality of Jaffe creatinine assay results using proficiency testing data

Results of an interlaboratory study are reported for the determination of lead in urine. Two levels of a lyophilized material containing biologically-bound lead were prepared using pooled urine obtained from lead-poisoned children undergoing the CaNa2EDTA mobilization test. The materials were circulated to a group of reference laboratories that participate in the `New York State Proficiency Testing Program for Blood Lead'. Results of the initial round-robin gave all-method consensus target values of 145±22 μg/l (S.D.) for lot 17 and 449±43 μg/l (S.D.) for lot 20. The interlaboratory exercise was repeated some 5 years later and consensus target values were re-calculated using the grand mean (excluding outliers) of results reported by laboratories using electrothermal atomization atomic absorption spectrometry (ETAAS). The re-calculated target values were 139±10 μg/l (S.D.) and 433±12 μg/l (S.D.). The urine reference materials were also analyzed for lead by several laboratories using other instrumental techniques including isotope dilution (ID), inductively coupled plasma (ICP) mass spectrometry (MS), flame atomic absorption with extraction, ICP-atomic emission spectrometry, ID-gas chromatography MS and flow injection-hydride generation AAS, thus providing a rich source of analytical data with which to characterize them. The materials were also used in a long-term validation study of an ETAAS method developed originally for blood lead determinations that has since been used unmodified for the determination of lead in urine also. Recently, urine lead method performance has been tracked in a proficiency testing program specifically for this analysis. In addition, a number of commercial control materials have been analyzed and evaluated.

Electrothermal atomization atomic absorption spectrometry for the determination of lead in urine: results of an interlaboratory study

Results of an interlaboratory study are reported for the determination of lead in urine. Two levels of a lyophilized material containing biologically-bound lead were prepared using pooled urine obtained from lead-poisoned children undergoing the CaNa 2EDTA mobilization test. The materials were circulated to a group of reference laboratories that participate in the `New York State Proficiency Testing Program for Blood Lead'. Results of the initial round-robin gave all-method consensus target values of 145±22 μg/l (S.D.) for lot 17 and 449±43 μg/l (S.D.) for lot 20. The interlaboratory exercise was repeated some 5 years later and consensus target values were re-calculated using the grand mean (excluding outliers) of results reported by laboratories using electrothermal atomization atomic absorption spectrometry (ETAAS). The re-calculated target values were 139±10 μg/l (S.D.) and 433±12 μg/l (S.D.). The urine reference materials were also analyzed for lead by several laboratories using other instrumental techniques including isotope dilution (ID), inductively coupled plasma (ICP) mass spectrometry (MS), flame atomic absorption with extraction, ICP-atomic emission spectrometry, ID-gas chromatography MS and flow injection-hydride generation AAS, thus providing a rich source of analytical data with which to characterize them. The materials were also used in a long-term validation study of an ETAAS method developed originally for blood lead determinations that has since been used unmodified for the determination of lead in urine also. Recently, urine lead method performance has been tracked in a proficiency testing program specifically for this analysis. In addition, a number of commercial control materials have been analyzed and evaluated.

Supported liquid membrane enrichment combined with atomic absorption spectrometry for the determination of lead in urine.

Supported liquid membrane (SLM) methodology was used for sample clean-up and enrichment of lead in urine prior to determination by AAS. Lead ions at pH 3 were extracted across a membrane solution containing 40% m/m di-2-ethylhexylphosphoric acid dissolved in kerosene and back-extracted into an acceptor solution of 1 mol l-1 nitric acid. The mechanism of mass transfer is a proton gradient across the membrane. The concentration range investigated was between 5 and 80 ng ml-1 and the extraction time was varied between 0.5 and 4 h, leading to enrichment factors of up to 200. The extraction efficiency was about 95%. The detection limit, expressed as 3 sigma of five replicate determinations, using a 45 min enrichment of a urine sample low in lead, was 0.1 and 6.0 micrograms l-1 for ETAAS, and FAAS respectively. The results obtained by the developed method agreed with those obtained by direct ICP-MS determinations for reference urine samples and samples from occupationally lead-exposed workers. The linear correlation coefficient was 0.97, the slope of the regression line was 1.06 and the intercept was -0.37 microgram l-1. The 95% confidence intervals for the slope and the intercept were 0.95 to 1.18 and -3.9 to 3.1, respectively. The results at the 95% confidence level for reference urine material were of 91 +/- 1.5 and 92 +/- 2.0 micrograms l-1 for ICP-MS and SLM-AAS, respectively, which agreed well with the recommended value of 90 micrograms l-1 (range 83-97 micrograms l-1).

Determination of lead in urine and whole blood by stable isotope dilution gas chromatography-mass spectrometry

A stable isotope dilution gas chromatography-mass spectrometry (GC-MS) method is described for the determination of lead (Pb) in urine and whole blood. The use of lithium bis(trifluoroethyl)dithiocarbamate Pb(FDEDTC) as a chelating agent showed strong memory effect, restricting the range of Pb isotope ratios that can be measured in unknown samples. To overcome this carryover problem, we further derivatized the Pb(FDEDTC)2 chelate with 4-fluorophenyl magnesium bromide to form Pb(FC6H4)4. The sequential analyses of solutions of natural Pb and enriched 204Pb with Pb(FC6H4)4 chelate by GC-MS demonstrated no observable memory effect. Precision and accuracy of Pb isotope ratio measurements with Pb(FC6H4)4 were established, and the isotope dilution GC-MS method was validated by determining Pb concentrations in urine standards from the National Institute of Standards and Technology, urine and blood reference materials from the New York State Department of Health, and blood Pb survey samples from the College of American Pathologists.

Determination of lead in urine by electrothermal atomic absorption spectrometry with probe atomization.

An automated graphite-probe atomizer was used for the direct analysis of diluted (2- to 12.5-fold) urine samples by electrothermal atomic absorption spectrometry (ETAAS). The method was applied successfully to the determination of Pb in reference materials, quality control urines and patient samples. The concentrations found were mainly in the range 7-93 micrograms dm-3 and agreed well with results obtained by an established ETAAS method, which involved chelation of Pb and solvent extraction into isobutyl methyl ketone. The detection limit, based on three times the standard deviation of the blank, was 4 micrograms dm-3 at 283.3 nm and 2 micrograms dm-3 at 217.0 nm. Although probe atomization removed chemical interferences for peak-area measurements, 10-20% suppression remained for some samples with peak-height measurements.

Fumed silica for the direct determination of lead in urine by differential-pulse anodic stripping voltammetry

The use of fumed silica for the direct determination of lead in urine by differential-pulse anodic stripping voltammetry was investigated. Fumed silica, added to urine prior to the nitrogen purge step, completely removed sorption interferences by urinary organic constituents. Values for lead in urine from eight unexposed individuals were 3 ± 2 μg l −1 or 3 ± 2 μg g −1 creatinine. This method is a fast, simple and effective means for the accurate determination of lead in undiluted urine without pretreatment.

Automated determination of lead in urine by means of computerized flow potentiometric stripping analysis with a carbon-fibre electrode

Five different digestion procedures have been investigated. In the recommended procedure 5 ml of concentrated hydrochloric acid—nitric acid mixture (1:1) were added to a 5-ml urine sample. After 1 min the sample was diluted to 100 ml with distilled water. The sample was divided into two 50-ml samples and to one of them a standard addition of 10 μg/l. lead(II) was made. The two samples were analysed fully automatically by means of computerized flow potentiometric stripping analysis, the main features of the procedure being mercury-film precoating, electrolysis of the sample for 90 sec and subsequent stripping in 1 M calcium chloride/0.1 M hydrochloric acid. Tin and copper were found not to interfere if present at concentrations below 50 mg/l. but high concentrations of tin had to be masked by the addition of copper in order to form a copper—tin intermetallic compound. Complexing agents used in lead poisoning therapy did not interfere with the determination. The lead concentration in a Seronorm® reference urine sample was found to be 93 μg/l. with a standard deviation of 8 μg/l. ( n = 5), the certified value being 88 μg/l.

Direct determination of lead in urine by Zeeman atomic absorption spectrometry with the stabilized temperature platform furnace

Direct determination of lead in urine by Zeeman atomic absorption spectrometry with the stabilized temperature platform furnace

Direkte Blei-Bestimmung in Urin mit einer neuen Mikromethode der Flammen-Atomabsorptionsspektrometrie (Schlaufen-AAS)

This paper describes a method for the direct determination of lead in urine using the newly developed loop AAS. In this technique, the sample to be analyzed is dried outside the flame on an electrically heated iridium loop. The loop is introduced into the flame of an AA-spectrometer by a precise transport mechanism. The detection limits of slightly and medium volatile elements are one or two orders of magnitude lower than those of conventional flame-AAS. By using an additional ceramic stagnation tube arranged in the flame, the power of detection is increased once more by about a factor 10. The high chemical resistance of iridium permits the use of strong acids for decomposition of the urine directly on the loop. The relative standard deviation is about 0.04 for a lead concentration of 90 micrograms/l. The detection limits are 3 to 10 micrograms/l depending on the AA-spectrometer used. The accuracy of the method is controlled by the analysis of control urine and by analyzing the same samples by graphite furnace-AAS.

Determination of lead in urine by atomic-absorption spectroscopy with electrothermal atomisation.

A method is described for the determination of lead in urine by atomicabsorption spectroscopy with electrothermal atomisation. The determination is rapid and minimum pre-treatment of the sample is required. Matrix interference is minimised by the addition of orthophosphoric acid and also by pre-coating the graphite tubes with molybdenum. Consideration is given to possible losses of organically bound lead during the drying and ashing cycle and steps to prevent these are incorporated in the procedure. The range of the method is 5–200 µg l–1 of lead.

Determination of lead in urine by atomic absorption spectrophotometry : Urine from persons orally administered with EDTA and from rabbit exposed to lead-fume

Determination of lead in urine by atomic absorption spectrophotometry : Urine from persons orally administered with EDTA and from rabbit exposed to lead-fume

Determination of lead in urine by atomic absorption spectrophotometry after coprecipitation with thorium

Lead is determined in urine by atomic absorption spectrophotometry after separation by coprecipitation with thorium, in the presence of copper(II) ; concentration of lead and removal of interferences are achieved simultaneously. Fresh urine or samples acidified with hydrochloric acid must be used. Precipitation is quantitative from the urine of subjects excreting coproporphyrins or treated with chelating agents, as the added copper liberates the chelated lead. The precision of the method is ±0.005 p.p.m. of lead.

Determination of lead in urine by atomic absorption spectrophotometry.

A method for the determination of lead in urine by means of atomic absorption spectrophotometry (AAS) is described. A combination of wet ashing and extraction with ammonium pyrrolidine dithiocarbamate into <i>iso</i>butylmethylketone was used. The sensitivity was about 0·02 μg./ml. for 1% absorption, and the detection limit was about 0·02 μg./ml. with an instrumental setting convenient for routine analyses of urines. Using the scale expansion technique, the detection limit was below 0·01 μg./ml., but it was found easier to determine urinary lead concentrations below 0·05 μg./ml. by concentrating the lead in the organic solvent by increasing the volume of urine or decreasing that of the solvent. The method was applied to fresh urines, stored urines, and to urines, obtained during treatment with chelating agents, of patients with lead poisoning. Urines with added inorganic lead were not used. The results agreed well with those obtained with a colorimetric dithizone extraction method (r = 0·989). The AAS method is somewhat more simple and allows the determination of smaller lead concentrations.

Rapid Determination of Lead in Urine by Ion Exchange

Abstract For routine screening of employees in the lead industry, a method for determination of urinary lead was developed in which this element is removed from urine by means of a chelating agent, eluted, and determined by a modified dithizone method. The method gives values which are about 5% below those obtained by the wet ashing technic, with a precision of ± 2.1% in the range of 2-15 µg. of lead per 50 ml. urine sample. The advantages of the method are that it requires only about 1 hr. to carry out, is convenient, and avoids the time-consuming and potentially hazardous wet ashing step.

A modification of the McCord and Zemp method for the determination of lead in urine.

Abstract In the determination of the total lead content of urine by the dithizone method a large part of the analysis time is spent in ashing. McCord and Zemp described a method using “wet ashing,” which shortened the ashing time to 30 min. The author, by using a modification of the above method, found that no loss of lead occurred as compared with a determination carried out with a longer ashing time. This method may be used for the analysis of urine from persons suffering from lead poisoning even after treatment with EDTA or penicillamine.

Determination of lead in urine by an ion exchange method.

Abstract An ion exchange method for the determination of lead in urine is described which involves 1) the automatic feeding of urine into an ion exchange column; 2) the concentration of lead from urine by a suitable resin; 3) the elution of lead from the resin by an acid, and 4) the subsequent determination of lead by an acceptable method. The results obtained by this method from the urines of lead-exposed persons compare favorably with results obtained by other methods. Recovery in lead-spiked urine is 90 to 100%.

Spectrographic determination of lead in whole urine.

Abstract A method is presented for the determination of lead in urine without requiring the ashing of the urine. An internal standard, indium, is used in preference to bismuth. The method was developed for use in analytical laboratories which require a high degree of versatility. A nitrogen atmosphere is introduced around the sample electrode to reduce the wandering of the arc and to lower the spectral background.