Determination Of Lead In Seawater Research Articles

Critical Evaluation of Analytical Procedures for the Determination of Lead in Seawater

: This article presents a critical evaluation of the analytical procedures used for the determination of lead in seawater, which is important because lead is a good indicator of marine pollution caused by human activities. Sampling, storage, and pretreatment techniques are briefly overviewed, including the significance of systematic errors that cannot be corrected later on. The main techniques in this article are electrothermal–atomic absorption spectrometry (ET-AAS), inductively coupled plasma–mass spectrometry (ICP-MS), and voltammetry. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma–optical emission spectrometry (ICP-OES) are treated as well, although their limits of quantification are not sufficient for a determination of lead in unpolluted seawater. Even when separation and preconcentration techniques are applied, these techniques are only capable of detecting lead in polluted coastal seawater. Separation and preconcentration are actually also required for ET-AAS and ICP-MS in order to determine the lowest concentrations of lead found in unpolluted open-ocean seawater, which is still a challenge for the analytical chemist.

Determination of lead in seawater by flow-injection on-line preconcentration-electrothermal atomic absorption spectrometry after coprecipitation with iron(III) hydroxide.

A flow-injection on-line preconcentration-electrothermal atomic absorption spectrometric (ETAAS) method coupled with a coprecipitation method has been developed for the determination of lead in seawater. The combination of two preconcentration procedures, coprecipitation with iron(II) hydroxide and solid-phase extraction with a lead-selective resin, Pb-Spec, allowed the determination of lead at the ng kg(-1) level. Lead in 250 g of a sample solution was collected by coprecipitation with 10 mg of iron. The precipitate was dissolved in 25 ml of 1 mol l(-1) nitric acid; then, a 4-ml aliquot of the sample solution was introduced into the flow-injection system to preconcentrate and separate lead from iron on a Pb.Spec microcolumn. The sorbed lead was eluted with a 1.0 x 10(-4) mol l(-1) EDTA solution. The 30-microl portion of the eluate corresponding to the highest analyte concentration zone was injected into a graphite furnace. The overall enhancement factor was about 200 for 250 g of the sample. The average and standard deviation of ten blank values obtained were 1.7 ng and 0.38 ng, respectively. The recovery was 93.7 +/- 5.0% for seawater spiked with 20 ng kg(-1) lead. The proposed method is applicable to the analysis of seawater for lead at slightly higher levels.

Determination of lead in seawater by inductively coupled plasma optical emission spectrometry after separation and pre-concentration with cocrystallized naphthalene alizarin

An analytical method for separation and pre-concentration of lead in seawater for determination by inductively coupled plasma optical emission spectrometry has been investigated. Lead was retained in the solid phase (0.5 g) composed of co-precipitated naphthalene and alizarin red. The solid phase quantitatively sorbs Pb(II) at pH 8–9, and the metal was eluted using 5.0 ml of 2 mol l −1 nitric acid. The effect of NaCl, KCl, BaCl 2, CaCl 2, Na 2SO 4, MgCl 2 and Na 3PO 4 on the sorption of Pb(II) in the solid phase was studied. A set of solutions containing varying amounts of electrolytes (0.5; 1.0; 3.0 and 5.0% m/v) with Pb (50 μg) was prepared and the recommended procedure applied. The Na 3PO 4 was found to interfere; the other electrolytes did not interfere up to 5% m/v. A pre-concentration factor of 40 was obtained in this analytical procedure. The limit of detection and limit of quantification for Pb(II) were 53 and 176 μg l −1, respectively. Lead was determined in seawater samples collected in Salvador city, Bahia, Brazil. The precision, expressed as R.S.D., was 1.8–4.6%, and the recovery of lead added to seawater samples was 95–97%.

Application of a Field Flow Preconcentration System with a Minicolumn Packed with Amberlite XAD-4/1-(2-pyridylazo)-2-naphthol and a Flow Injection-Flame Atomic Absorption Spectrometric System for Lead Determination in Sea Water

A field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol was used to preconcentrate lead from seawater. Elution of retained lead on the minicolumns was performed by a flow-injection-flame atomic absorption spectrometric system. Factorial designs have been used to optimise the field flow preconcentration system and the flow injection elution process. Factors such as sample pH, sample flow-rate, eluent concentration and volume (hydrochloric acid), elution flow-rate and minicolumn diameter were considered. The results suggest that the sample flow-rate and the eluent volume are statistically significant factors. The detection limit (3σ) of the procedure was 5 ng/L for a sample volume of 1000 mL. The precision (expressed as relative standard deviation) for eleven independent determinations reached values of 4.0–3.1% in lead solutions of 50–200 ng/L. This procedure has been successfully applied to the determination of lead in seawater from Galicia (Spain).

Minicolumn field sampling and flow‐injection‐atomic absorption spectrometric determination of lead in seawater

AbstractA simple field‐flow preconcentration system has been developed for lead determination in seawater. Seawater samples are collected in situ by passing them with a pump through minicolumns packed with poly(aminophosphonic acid) chelating resin to retain and preconcentrate lead, and remove the saline matrix. Minicolumns loaded with lead are then returned to the laboratory where they are inserted into a flow‐injection system and eluted with a small volume of hydrochloric acid into the nebulizer‐burner system of a flame atomic absorption spectrometer. The detection limit for lead in seawater was 2.8 ng l−1. This procedure was applied to the determination of lead in seawater samples from Galicia (Spain). © 2001 John Wiley & Sons, Inc. Field Analyt Chem Technol 5: 239–243, 2001

Determination of lead in a chloride matrix by atomic absorption spectrometry using electrothermal vaporization and capacitively coupled plasma atomization

A simple and rapid method using graphite furnace vaporization and plasma atomization for the determination of lead in a sodium chloride matrix was developed. Samples were injected into the furnace of a commercial graphite furnace atomic absorption/plasma emission spectrometer. A relatively low vaporization temperature of 750 °C was used to vaporize lead chloride preferentially from the bulk sodium chloride matrix. The lead chloride molecules were then atomized by a capacitively coupled plasma. The lead atomic absorption signal is, therefore, separated from the sodium chloride background absorption temporally. Detection limits (3σ) in 3% m/v sodium chloride are 4 and 40 pg of lead using peak absorbance and integrated absorbance, respectively, for a 20 µl sample. The direct determination of lead in sea-water, however, suffers from matrix effects due to magnesium sulfate. Addition of oxalic acid as a chemical modifier eliminates the magnesium sulfate interference. Detection limits (3σ) in a sea-water matrix are 28 and 2 pg of lead using peak absorbance and integrated absorbance, respectively. The precision of the method is ≤7% RSD (five replicates of 20 µl of a 25 ng ml–1 Pb sample in either a sodium chloride or sea-water matrix).

Determination of lead in seawater by electrothermal atomic absorption spectrometry with transversely heated furnace by using oxalic acid or Pd/Mg as modifiers

The simultaneous volatilization of seawater salts and lead free atoms induces chemical interferences. Moreover, an under-compensation related to the vaporization of seawater salts is observed; the systematic error depends on the magnitude of the background absorption signal to be corrected and can be very important at low Pb concentrations. In the presence of oxalic acid, which modifies the seawater matrix and promotes a lower atomization temperature, the chemical interference is suppressed and the background absorption signal is dramatically reduced. In the presence of the Pd/Mg modifier and nitric acid, Pb is stabilized at a higher temperature and the major part of the seawater matrix can be removed before atomization, but the integrated absorbance remains depressed. The detection limits obtained for 10 μ1 of seawater in the presence of oxalic acid or Pd/Mg and nitric acid used as modifiers are respectively 0.3 μg 1 −1 and 0.5 μg 1 −1.

Determination of lead in sea-water with a graphite furnace atomic absorption spectrometer and an improved automatic on-line pre-concentration system

An improved automatic on-line pre-concentration system for graphite furnace atomic absorption spectrometry (GFAAS) for the determination of trace metals in sea-water was developed. This system was modified from a Perkin-Elmer AS-40 autosampler by mounting a silica gel C 18 microcolumn near the tip of the autosampler capillary. The pre-concentration procedure was performed by using a four-way distribution valve and controlled by a programmable controller. The pre-concentration system developed previously was improved by using a peristaltic pump to replace the reciprocating pumps, a newly designed tube bed adjuster to release the back-pressure in the pre-concentration system, and a better control program, such that on-line pre-concentration became more reliable and fully automatic. The chelating agent ammonium pyrolidinedithiocarbamate (APDC) and a miniature column packed with 5 mg of C 18 silica gel were used for pre-concentration. This system was tested by analyzing the lead content in reference standard sea-water samples. A sample volume of only 2 ml was required to determine lead in sea-water. The relative limit of detection of lead was 3.5 pg/ml.

Determination of lead in sea-water by inductively coupled plasma atomic emission spectrometry combined with chelating resin preconcentration and hydride generation

A combination of hydride generation with inductively coupled plasma atomic emission spectrometry (ICP-AES) after sample preconcentration using Chelex-100 resin was successfully applied to the determination of Pb in open sea-water where the concentration found ranged between 40 and 50 ng l–1 and coastal sea water where the lead concentration was higher. The detection limit of the proposed method was 6 ng l–1, which was about 100 times better than the methods using preconcentration such as solvent extraction or ion exchange, followed by ICP-AES with direct nebulization of the solution. The method was checked with a reference material (Near-shore Seawater, CASS-1, National Research Council of Canada) and the result was in good agreement with the certified value.

Determination of lead in seawater by furnace atomic absorption spectrometry after concentration with yield tracer

Determination of lead in seawater by furnace atomic absorption spectrometry after concentration with yield tracer

Microquantitative determination of lead in sea-water and its geochemical meaning, the age of the ocean (I)

Microquantitative determination of lead in sea-water and its geochemical meaning, the age of the ocean (I)