Determination Of Total Lead Research Articles

A separation system for lead fractionation in river water using electrothermal atomic absorption spectrometry

This work proposes a separation system that uses the Sep-Pak C-18 cartridge to enable the determination of labile and total lead in natural water samples. This method is composed of two steps. First, the sample is percolated through the cartridge, where the lead that is bound to the organic compounds is retained and the quantification of labile lead is performed using the eluate from this separation. Afterwards, another sample enables the determination of total lead. Lead was determined through electrothermal atomic absorption spectrometry (ET-AAS) using aluminum as a chemical modifier under the following instrumental conditions: pyrolysis temperature of 800 °C and atomization temperature of 1800 °C. This method allows the determination of lead with limits of detection and quantification of 0.14 and 0.47 μg L−1, respectively. The accuracy of this method for the determination of total lead was confirmed by analysing a standard reference material of trace elements in natural water supplied by NIST. Experiments using lead solutions in the presence of humic acid confirmed the efficiency of the Sep-Pak C-18 cartridge for the quantitative extraction of lead ions bound to organic complexing agents. This method was applied for the determination of labile and total lead in river water samples collected in Santo Amaro City, Bahia State, which is a region that is historically contaminated by lead as a result of a lead ore smelter that operated in the area from 1960 to 1993. For the five samples analyzed, the total lead concentrations ranged from 1.18 to 13.57 μg L−1. The fraction of labile lead ranged from 48% to 80% in four samples. The fifth sample had a labile lead content of 11%. The total carbon content was also determined in all the analyzed samples. The obtained concentrations did not present a correlation with the results obtained for lead.

Determination of total lead and lead species according to their lability in coastal seawater by Chelex-100 titration and electrothermal-atomic absorption spectrometry

A speciation method based on Chelex-100 titration in combination with electrothermal-atomic absorption spectrometry has been developed to study the distribution of Pb among different fractions in coastal seawater. The method allows an accurate determination of total Pb, thereby avoiding the effect of the saline matrix. Additionally, the distribution patterns of Pb among species with different lability can be established in seawater as a function of pH. Four Pb fractions have been obtained in a model seawater and two seawater samples from Ria de Vigo (NE Atlantic ocean), i.e. free Pb ion, inorganic Pb fraction, organic Pb fraction and inert Pb fraction. The inert and labile organic Pb fractions dominate at natural pH (≈8).Complexation mechanisms of Pb were investigated from the sorption curves of lead on Chelex-100 according to the Gibbs–Donnan model. Three complexes were formed, PbL, PbL2 and Pb(HL)2 with the following intrinsic complexation constants logβ(1np) = −3.25, −10.10 and −1.98, respectively. The formation of the complex PbL is negligible in all range of pH studied, while the complex Pb(HL)2 predominates up to pH 4 and PbL2 from pH 4.

Determination of total lead in lipstick: Development and validation of a microwave‐assisted digestion, inductively coupled plasma–mass spectrometric method

Recent reports describing the presence of lead (Pb) in lipsticks have suggested that, under ordinary use, the potential amount of Pb exposure is harmful. To permit independent assessment of the Pb contamination, a method for determining total Pb in lipstick using microwave-assisted digestion and analysis employing inductively coupled plasma-mass spectrometry (ICP-MS) was developed and validated. Since lipsticks may contain fats, oils, pigments, dyes, and minerals, several reference materials (RM) were analyzed, including coal, wear metals in oil, organic Pb in oil, milk powder, and estuarine sediment. With the exception of the RM with mineral content (estuarine sediment), complete recovery of Pb from the RMs was obtained by simple nitric acid (HNO(3)) digestion. Complete recovery of Pb from estuarine sediment was achieved only when hydrofluoric acid (HF) was added to the digestion mix, followed by treatment with excess boric acid (H(3)BO(3)) to neutralize the HF and to dissolve insoluble fluorides. Commercial lipsticks were tested for total Pb by the validated method. The detection limit was estimated to be 0.04 microg Pb/g. The average value obtained for the lipsticks was 1.07 microg/g. Undigested material was present in some lipstick digests when only HNO(3) was used, and generally lower Pb values were obtained. All of the Pb levels found by the U.S. Food and Drug Administration (FDA) were within the range the agency would expect to find in lipsticks formulated with permitted color additives and other ingredients prepared under good manufacturing practice (GMP) conditions. This method will be useful for the FDA and industry in helping to ensure the safety of cosmetic products.

Anodic stripping voltammetric determination of total lead, copper and selenium in whole blood and blood serum

A two-step procedure including appropriate wet-digestions, separation of selenium from interfering ions such as heavy metal ions with pentyl alcohol and anodic stripping voltammetric (ASV) determination of Pb2+, Cu2+ and SeO32– is developed. The elements in digested whole blood and serum sample solutions were determined by using a standard addition method. 1 × 10–9 mol/L SeO2–3, Cu2+ and Pb2+ were successfully determined with relative standard deviations of approximately 1–2% (n = 6–8).

Enthalpimetric determination of total lead in gasoline

A method is descubed for the determination of lead alkyl additives in gasoline by direct injection enthalpimetry. The method is a single step process, iodine monochloride solution is injected into a sample of the gasoline diluted with an equal volume ofo-xylene. The system can be arranged to gave a direct reading of the concentration of the permitted lead alkyls for several concentration ranges. Once calibrated the proposed method can be operated by semi-skilled workers. The precision and accuracy are within industrial limits. The main advantages of the method are those of low cost and low time of analysis.

The Effectiveness of the Freeze Fracture Carpet Grinding Technique in the Determination of Total Lead

The Effectiveness of the Freeze Fracture Carpet Grinding Technique in the Determination of Total Lead

The Effectiveness of the Freeze Fracture Carpet Grinding Technique in the Determination of Total Lead

This article describes a study using carpets of known lead content to determine whether a grinding technique is useful in preparing carpeted surfaces for chemical analysis for total lead. This technique, termed “freeze fracture,” involves freezing and grinding carpet samples, then digesting and analyzing the ground material. The freeze fracture technique was performed by two technicians on three sample sets of known lead content. The results indicated that the procedure recovers less (∼67%) than the total lead known to be present within the carpet. Excessive sample handling requirements causing numerous opportunities for material losses during the procedure create the potential for additional reduction in recovery. If this technique is to be attempted as part of a carpet sampling and testing program, a rigorous sampling protocol, strict quality control procedures, and a technician proficiency testing program should be developed. Data obtained through the use of this method should be carefully examined pri...

Analysis of tellurides of lead and tin by automatic titrations

An analytical method based on automatic potentiometric EDTA and redox titrations was developed for the analysis of tellurides of lead and tin.First, the sum of lead and tin is titrated at pH 4.5 by adding a known excess of EDTA and back-titrating with a standard lead solution. After addition of ammonium fluoride to mask the tin, the EDTA released from the Sn-EDTA complex is titrated with standard lead solution. Alternatively, after the determination of total lead and tin, lead may be determined by back-titration with standard lead on a separate sample aliquot using tartaric acid to mask the tin. Tellurium is separated as tellurous acid, which is then dissolved in a dilute sulfuric acid solution and oxidized by permanganate at room temperature; the excess permanganate is back-titrated with iron(II) solution automatically. This titration may also be used to determine tellurium in the presence of lead and tin after treatment with perchloric acid. Accuracies of 0.1-0.2% can be obtained.