Voltammetric Studies of Cadmium‐ and Zinc‐Containing Metallothioneins at Nafion‐Coated Mercury Thin Film Electrodes

Voltammetric studies of rabbit liver metallothioneins (MTs, containing both Zn and Cd ions) and Zn₇‐MT were carried out at Nafion‐coated mercury film electrodes (NCMFEs). The accumulation of MT molecules into the NCMFEs enhances the voltammetric signals and the electrostatic interaction between the Nafion membrane and MT facilitates facile electron transfer reactions. Two well‐defined redox waves, with reduction potential (E_pc) values at ?0.740 and ?1.173 V, respectively, were observed. The peak at E_pc =?0.740 V is attributable to the reduction of the Cd‐MT complex, whereas that at E_pc=?1.173 V was assigned to the reduction of the Zn‐MT complex. Zn₇‐MT exhibits only one redox wave with E_pc=?1.198 V. The NCMFE was found to be more advantageous than thin mercury film electrode (MFE), because the pristine metal ions in MTs (e.g., Cd²⁺ and/or Zn²⁺) are not significantly replaced by Hg²⁺. The NCMFE is also complementary to Nafion‐coated bismuth film electrode in that it has a greater hydrogen overpotential, which allows the reduction of the Zn‐MT complex to be clearly observed. Moreover, intermetallic compound formation between Cd and Zn appears to be less serious at NCMFEs. Consequently, the amounts of Cd and Zn deposited into the electrode upon the reduction reactions can be quantified more accurately.     

Constant Current Stripping Chronopotentiometry for the Study of Adsorbing Inert and Electrochemically Nonreversible Metal Complexes at Low Concentrations: Application to Cd and Zn Metallothioneins

Constant current chronopotentiometric stripping analysis using adsorptive accumulation and negative stripping current (AdSCP) was applied for the study of behavior of rabbit liver Cd‐Zn and Zn metallothionein (Cd‐Zn‐MT, ZnMT) on hanging mercury drop electrode. Electrochemically inert or labile behavior of complexes can be distinguished with the application of high (1000 nA) or low (100 to 20 nA) current. Using high current, no influence of added Cd²⁺ or Zn²⁺ ions on the reduction of Cd(II) or Zn(II) complexed within MT molecule was observed, except of additions of Cd²⁺ to ZnMT, where bound Zn(II) was substituted by cadmium ions. With lowering of stripping current and increasing concentration of added Cd²⁺ or Zn²⁺ ions in solution progressive formation of reorganized complex with labile behavior is observed. Parallel measurement using DC voltammetry with different rates of polarization or differential pulse voltammetry were in agreement with AdSCP measurement. However, only chronopotentiometric method combines good sensitivity and signal separation at μM concentrations, inevitable in MT studies.     

Bioaccumulation of metals and induction of metallo‐ thioneins in selected tissues of common carp (Cyprinus carpio L.) co‐exposed to cadmium,mercury and lead

The concentrations of mercury (Hg), cadmium (Cd) and lead (Pb) at various exposure periods were determined in the gill, kidney, liver and muscle of common carp (Cyprinus carpio L.) co‐exposed to 1.0 µg ml^?1 each of Cd²⁺, Hg²⁺ and Pb²⁺ for up to 10 days. Metallothionein fractions (MTs) in these organs were characterized using the hyphenated technique of size‐exclusion chromatography (SEC) and inductively coupled plasma mass spectrometry (ICP‐MS). After 10 days of exposure, maximum toxic metal concentrations of Hg, Cd and Pb were 10.7 (gill), 0.145 (kidney) and 0.112 µg g^?1_dryweight (gill), respectively. The pattern of accumulation of Hg and Pb was in the order gill > kidney > liver > muscle. In the case of Cd, accumulation was in the order kidney > gill > liver > muscle. Cd and Hg binding MTs were significantly induced in the gill, kidney and liver of all the exposure groups in comparison with the control group (p < 0.05), and the amounts of them increased with the longer exposure time. Despite the higher intracellular Hg concentration and the stronger Hg? SH binding affinity, the amount of Cd‐binding MTs was much higher than that of Hg‐binding MTs. The results indicate that MT synthesis in these organs was clearly metal‐specific. MTs in gill may be used as a bio‐marker to detect the metal pollution caused by Hg and Cd. Zinc and copper binding MTs in the organs of the exposed fish were also increased. This may be due to the MTs' important role in the homeostatic regulation of essential metals and their protective role against the acute toxicity of non‐essential metals. Even though there was considerable accumulation of lead in the organs of the exposed fish, Pb‐binding MT synthesis was non‐significant. Copyright © 2006 John Wiley & Sons, Ltd.     

Analysis OF Trace Metals In Water By Inductively Coupled Plasma Emission Spectrometry Using Sodium Dibenzyldithiocarbamate For Preconcentration

Abstract

Since concentrations of trace elements in most natural waters seldom exceed the μg/L level, analysis of trace elements in natural waters by inductively coupled plasma emission spectrometry (ICP) requires a preconcentration procedure. The elements Ag, Bi, Cd, Co, Cu, Fe, Mo, Ni, Pb, Sn, V, W, and Zn were separated and concentrated from 500 mL of water by coprecipitating them with sodium dibenzyldithiocarbamate (NaDBDTC) using nickel or silver as a carrier. The precipitated trace elements were collected on a membrance filter, redissolved from the filter with hot nitric and hydrochloric acids, and analyzed using ICP. Recoveries for all the trace elements except tungsten exceeded 80%. Coprecipitation of trace elements with NaDBDTC eliminated the use of difficult-to-inject organic solvents, and NaDBDTC coprecipitated a wider array of trace elements than ammoniumpyrrolidinedithiocarbamate (APDC), another commonly used coprecipitate.     

Simultaneous determination of macro and trace elements in biological reference materials by microwave induced plasma optical emission spectrometry with slurry sample introduction

A slurry sampling technique (SST) has been utilized for simultaneous multi-element analysis by microwave-induced plasma optical emission spectrometry (MIP-OES). Slurry samples from a spray chamber are fed directly into the microwave cavity-torch assembly (power 300 W) with no desolvation apparatus. The performance of SST-MIP-OES was demonstrated by the determination of macro (Na, K, Ca, Mg, P) and trace (Cd, Cu, Mn, Sr, Zn) elements in three biological certified reference materials using a V-groove, clog-free Babington-type nebulizer. Slurry concentrations up to 1% m/v (particles <20 μm), prepared in 10% HNO₃ (pH 1.2) containing 0.01% of Triton X-100, were used with calibration by the standard additions method. The method offers relatively good precision (R.S.D. ranged from 7 to 11%) with measured concentrations being in satisfactory agreement with certified values for NRCC TORT-1 (Lobster hepatopancreas), NRCC LUTS-1 (Lobster hepatopancreas) and IAEA-153 (Milk powder). The concentrations of Na, K, Ca, Mg, P and Cd, Cu, Mn, Sr, Zn were determined in the range 90–22 000 μg/g and 1–420 μg/g, respectively. The method could be useful as a routine procedure.     

Simultaneous Determination of Cd(II), Cu(II), Pb(II) and Zn(II) in Human Plasma by Potentiometric Stripping Analysis

In this paper, Potentiometric Stripping Analysis (PSA) was simultaneously used to determine the concentrations of trace metals (Zn, Cd, Pb and Cu) in human plasma. The metal ions were concentrated as their amalgams on the glassy carbon surface of a working electrode that was previously coated with a thin mercury film and then stripped by a suitable oxidant. The selection of the experimental conditions was made by using the experimental‐designed methodology. The optimum conditions of the method includes a 0.2 M HAc‐NaAc buffer mixture (pH 4.5) as supporting electrolyte, and an electrolysis potential of‐1220 mV. The limits of detection (LOD) were obtained 1 μg L^?1 for Zn(II) and Pb(II), 0.5 μg L^?1 for Cu(II) and 2 μg L^?1 for Cd(II) in the studied medium. The good recoveries were obtained for the analysis in human plasma. The method was applied to blood samples, using the method of standard additions and the results were compared with Inductively Coupled Plasma‐Atomic Emission Spectrometry (ICP‐AES) as reference method. Furthermore, a simple digestion protocol of samples is investigated compared to the conventional digestion method.     

Cadmium Determination in Sedimented Dust by Atomic Emission Spectrometry With a New Radiofrequency Capacitively Coupled Plasma Source

ABSTRACT

A new radiofrequency capacitively coupled plasma source (r.f.CCP) was used for Cd determination in dust samples by atomic emission spectrometry. The plasma torch consists of a molybdenum tube electrode and one or two ring electrodes situated outside the quartz tube. Plasma was operated at 27.12 MHz, at low power (275 W) and low gas consumption (0.4 1 min^? argon flow). The choice of the optimum operating conditions for Cd determination in dust samples dissolved in acids and pneumatically nebulized is presented. The results obtained in such samples were compared with those obtained by flame atomic absorption spectrometry (FAAS). The matrix effect of NaCl and CaCl₂ on Cd emission was also studied depending of the plasma coupling system. The true limit of detection for Cd in dust sample by r.f.CCP-AES is 3 μg g^?1. Concentration of Cd higher than 10 μg g^?1 can be determined by the proposed method with a relative standard deviation within the range 5 - 10%. The recovery is 100 ± 10%.     

Anodic Stripping Potentiometric Determination of Cu,Pb, Cd and Zn In Natural Waters on a Novel Combined Electrode System

Abstract

A method is described for the reliable determination of copper, lead, cadmium and zinc in natural waters by anodic stripping potentiometry with the use of a novel combined electrode. The method involves two stripping cycles during which copper is initially determined on its own, followed by simultaneous determination of lead, cadmium and zinc after addition of gallium (III) ions. The optimum conditions include 0.01 M HCl as supporting electrolyte, 10 mg/L Hg (II) as chemical oxidant; E_dep(Cu) -700 mV vs Ag/AgCl; E_{dep(Pb,Cd,Zn)} -1200 mV vs Ag/AgCl; t_dep 10s; 150 μg/L Ga (III); sample rotation rate 5 and rest period 30s. Under these conditions, as low as 0.06 μg/L Cu (0.7% RSD); 0.2 μg/L Pb (13% RSD); 0.04 μg/L Cd (7.8% RSD) and 0.06 μg/L Zn (5.5% RSD) can be determined reliably. A linear concentration range of 0–110 μg/L was obtained for the four metals. The successful application of the method to reference fresh water, creek water and tap water is demonstrated.     

X-ray fluorescence determination of As, Bi, Co, Cu, Fe, Ni, Pb, Se, V and Zn in natural water and soil extracts after preconcentration of their pyrrolidinedithiocarbamates on cellulose filters

A simple method for the elements preconcentration on thin-layer paraffin-treated cellulose filters was proposed. It was found that pyrrolydinedithiocarbamates of As(III), Bi, Cd, Co, Cu, Fe(III), Ni, Pb, Se(IV), V(V) and Zn obtained after mixing of sample (3-5 ml min⁻¹) and reagent (0.7-1.0 ml min⁻¹) streams were quantitatively recovered from 100 ml sample. The sample acidity was adjusted to pH 4.8-5.2 for preconcentration of Cd, Co, Cu, Fe(III), Ni, Pb, V(V) and Zn, and to 2 M HCl for preconcentration of As, Bi and Se. The optimum reagent concentration was found to be 0.1%. The elements were determined on the filters by X-ray fluorescence spectrometry. The detection limits achieved were 0.1-4.0 μg of element on the filter. Relative standard deviation (R.S.D.) was not higher than 0.08 while determining 5-50 μg of elements on filter. Accuracy and precision of the technique proposed were evaluated by the analysis of spiked natural samples.     

Spectrophotometric Determination of Trimethoprim in Pure Form and in Pharmaceutical Preparations using Bromothymol Blue,Bromocresol Green and Alizarin Red S

ABSTRACT

Simple, sensitive and selective methods for the determination of trimethoprim (TMP) in pure form and in pharmaceutical formulations are described. The methods are based on the reaction of TMP as a π-electron donor with bromothymol blue (BTB), bromocresol green (BCG) and alizarin red S (ARS) as electron acceptors. The coloured products are quantified spectrophotometrically at their corresponding λ_max.

Beer's law is obeyed in case of BTB in the range 2.9-23.2 μg/ml (CHCl₃), 2.9-20.0 μg/ml (CH₂Cl₂) and 5.0-29.0 μg/ml (ClC₆H₅), in the case of BCG 2.9-27.5 μg/ml (H₂O/alc.), 2.9-18.3 μg/ml (CHCl₃) and 2.9-20.3 μg/ml (CH₂Cl₂) and for ARS in the range 3.0-12.0 μg/ml in H₂O/alc medium.

The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries are evaluated. Application of the suggested methods to dosage forms is presented and compared with the pharmacopoeial method. The interference from additives and sulfa compounds, especially sulfamethoxazole, has been overcome by extraction into chloroform or methylene chloride.     

Determination of cadmium and lead at low levels by using preconcentration at fullerene coupled to thermospray flame furnace atomic absorption spectrometry

A new and sensitive method for Cd and Pb determinations, based on the coupling of thermospray flame furnace atomic absorption spectrometry and a preconcentrator system, was developed. The procedure comprised the chelating of Cd and Pb with ammonium pyrrolidinedithiocarbamate with posterior adsorption of the chelates on a mixture (40 mg) of C₆₀ and C₇₀ at a flow rate of 2.0 ml min⁻¹. These chelates were eluted from the adsorbent by passing a continuous flow of ethanol (80% v/v) at 0.9 ml min⁻¹ to a nickel tube placed in an air/acetylene flame. After sample introduction into the tube by using a ceramic capillary (0.5 mm i.d.), the analytical signals were registered as peak height. Under these conditions, improvement factors in detectability of 675 and 200 were obtained for Cd and Pb, respectively, when compared to conventional flame atomic absorption spectrometry. Spiked samples (mineral and tap waters) and drinking water containing natural concentrations of Cd were employed for evaluating accuracy by comparing the results obtained from the proposed methodology with those using electrothermal atomic absorption spectrometry. In addition, certified reference materials (rye grass, CRM 281 and pig kidney, CRM 186) were also adopted for the accuracy tests. Due to the good linearity ranges for Cd (0.5–5.0 μg l⁻¹) and Pb (10–250 μg l⁻¹), samples with different concentrations could be analyzed. Detection limits of 0.1 and 2.4 μg l⁻¹ were obtained for Cd and Pb, respectively, and RSD values <4.5% were observed (n=10). Finally, a sample throughput of 24 determinations per hour was possible.     

Determination of trace Pb(Ⅱ), Cd(Ⅱ) and Zn(Ⅱ) using differential pulse stripping voltammetry without Hg modification

In this work,we reported a simultaneous determination approach for Pb(II),Cd(II)and Zn(II)atμg L 1concentration levels using differential pulse stripping voltammetry on a bismuth film electrode(BiFE).The BiFE could be prepared in situ when the sample solution contained a suitable amount of Bi(NO)3,and its analytical performance was evaluated for the simultaneous determination of Pb(II),Cd(II)and Zn(II)in solutions.The determination limits were found to be 0.19μg L 1for Zn(II),and0.28μg L 1for Pb(II)and Cd(II),with a preconcentration time of 300 s.The BiFE approach was successfully applied to determine Pb(II),Cd(II)and Zn(II)in tea leaf and infusion samples,and the results were in agreement with those obtained using an atomic absorption spectrometry approach.Without Hg usage,the in situ preparation for BiFE supplied a green and acceptability sensitive method for the determination of the heavy metal ions.     

Combining Ammonium Pyrrolidine Dithiocarbamate/methyl Isobutyl Ketone Microextraction in an Inexpensive Disposable Pipette with Laser Ablation Inductively Coupled Plasma Mass Spectrometry for the Determination of Cd and Pd

This paper describes a new analytical method, using a combination of ammonium pyrrolidine dithiocarbamate/methyl isobutyl ketone (APDC‐MIBK) microextraction and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS), for the determination of the concentrations of Cd and Pb in aqueous samples. Only 200 μL of organic solvent was used throughout the entire analysis process, with enhancement factors as high as 25. Recoveries from replicate analyses of natural water [NIST 1640(a)] containing mean concentrations of 3.1 μg Cd L^?1 and 9.3 μg Pb L^?1 were 95 ± 3 and 104 ± 4%, respectively. The corresponding detection limits were 0.6 μg L ^?1 for Cd and 0.9 μg L ^?1 for Pb. The main advantage of this approach is its simplicity in terms of sample preparation, as demonstrated by quantifying the levels of Cd and Pd in real samples, including tap water, groundwater, and seawater, using a standard addition method.     

Thermal studies on metal complexes of 5-nitrosopyrimidine derivatives

The following Zn(II), Cd(II), Hg(II) and Hg(I) complexes of 4-amino-1,6-dihydro-2-methylthio-5-nitroso-6-oxopyrimidine (MTH) have been prepared and their thermal behaviour studied by TG and DSC techniques: Zn(MT)₂·3H₂O, Cd(MT)·H₂O. Cd(MTH)Cl₂, Hg(MTH)Cl₂ and Hg₂(MT)(NO₃). The dehydration and dehalogenation enthalpy values were calculated.     

Inductively coupled plasma optical emission spectrometric determination of trace element in PM10 airborne particulate matter collected in an industrial area of Argentina

Trace metals of relevance from the environmental and toxicological point of view were quantified in the city of Campana, Buenos Aires, Argentina. The collection of particulate matter was performed on ash-free fiber glass filters using high-volume samplers with a PM₁₀ sampling head, during a 3-month period in 2002. An acid leaching of elements deposited on the filters was adopted paying special attention to the recovery of volatile elements. Analysis was performed by inductively coupled plasma optical emission spectrometry (ICP OES) to ascertain the concentrations of 12 key elements, namely, Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn. The validation of the procedure was performed by the analysis of the standard reference material NIST 1648, urban particulate matter, and good agreement between concentrations found and the reported certified values was achieved. Blank filters were spiked with the analytes investigated and the recoveries varied between 83% and 92%. Metal concentrations spanned the range 0.03 ng m⁻³ (equivalent to 0.42 μg g⁻¹) for Cd to 1.9 μg m⁻³ (equivalent to 29.7 mg g⁻¹) for Fe. The results obtained show that the pollutants of special environmental and health concern are As and Pb. Mean As concentration was higher than the guideline value associated with an excess cancer risk of 1:10⁻⁶, reported by the World Health Organization (WHO). Lead is the only element that showed higher concentrations than those recently measured in the large and heavily trafficked metropolitan area of Buenos Aires. Cadmium>Pb>As>Zn>Cu are the elements more enriched in airborne PM₁₀.     

Inductively coupled plasma-atomic emission spectrometry method for determination of trace metals in alkaline-earth matrices after flotation separation

An inductively coupled plasma-atomic emission spectrometry (ICP-AES) method is developed for determination of Cd, Co, Cr, Cu, Ni, Tl and Zn in traces in calcite, CaCO₃, dolomite, CaMg(CO₃)₂, and gypsum, CaSO₄. Interferences of a Ca/Mg matrix on analyte intensities were investigated. The results reveal that Ca does not interfere with Cr, Ni and Zn, but tends to decrease the intensity of the other elements. Magnesium as a matrix element does not interfere on with Zn, but increases the intensities of Ni, Cr and Cu, and decreases the intensities of Cd, Co and Tl. To eliminate these matrix interferences on trace element intensities, a flotation separation method is proposed. Lead(II) hexamethylenedithiocarbamate, Pb(HMDTC)₂, is applied as a collector for flotation of trace elements from acidic solutions of mineral samples. The flotation of acidic aqueous solutions of calcite, dolomite and gypsum was performed at pH 6.0, using 10 mg l⁻¹ Pb and 0.3 mmol l⁻¹ HMDTC⁻ added to 1 l of solution tested. The method detection limits of analytes in different minerals range from 0.02 to 0.06 μg g⁻¹ for Cd, 0.04 to 0.10 μg g⁻¹ for Co, 0.03 to 0.13 μg g⁻¹ for Cr, 0.02 to 0.16 μg g⁻¹ for Cu, 0.09 to 0.30 μg g⁻¹ for Ni, 6.45 to 7.71 μg g⁻¹ for Tl and 0.18 to 0.20 μg g⁻¹ for Zn.     

Investigation of mercury metallothionein complexes in tissues of rat after oral intake of HgCl2

Mercury, a highly toxic metal found widely throughout the environment, is a potent inducer of metallothionein (MT) expression. The role of MTs in the detoxification of mercury after its oral intake in mammals is studied. After feeding rats with mercuric chloride by gastric gavage, the distribution of heavy metals in rat tissues was investigated by inductively coupled plasma mass spectrometry (ICP‐MS). Extensive accumulation of mercury, copper and zinc in kidney and liver is observed. A homemade preparative size‐exclusion chromatography (SEC) column (30 cm × 1.9 cm) packed with Sephadex G‐75 (40–120 µm particle size) gel (Pharmacia) was used for the purification of MT fractions in rat tissues. Preliminary results from SEC indicate that the mercury‐binding MT levels in liver were much lower than in kidney. The MT fractions were collected, desalted, and then separated by reversed‐phase high‐performance liquid chromatography (HPLC) with UV–Vis spectrometry, ICP‐MS and electrospray ionization MS detection. One major and several minor peaks were observed in the HPLC chromatograms of the MT fraction for the kidney sample. UV absorption spectra indicate that MTs were found to bind with mercury. There were no significant mercury‐binding MTs detected in the liver sample using UV detection. ICP‐MS detection showed that mercury‐binding MTs in kidney contained large amounts of mercury and copper but little zinc. Further characterization with ESI‐MS showed that the major peak found in kidney contained Hg₆Cu, Hg₅Cu₂‐MT‐2c and Hg₆‐MT‐2β, Hg₆Cu‐MT‐1γ, Hg₇‐MT‐2α. However, distinction between copper and zinc could not be made based on current mass spectrometric analysis because of instrumental resolution limitations. Copyright © 2005 John Wiley & Sons, Ltd.     

Voltammetric Analysis of Cadmium and Lead (Undesirable Elements) in Brine,Supported by Solid Phase Extraction – the Right Solution of the Analytical Challenge

The stripping voltammetry at HMDE is proposed for Cd and Pb (undesirable ingredients) determination in the natural brine (C_Cl >43 g L⁻¹). Samples with so high salinity have to be significantly diluted. For ICP MS, a 10^5–6 times dilution is required, which disqualifies this method. The proposed procedure allows to determine Cd (0.001 μg L⁻¹) and Pb (0.005 μg L⁻¹) after only 100 times dilution. The thermal chloride stripping or isolation by Chelex 100 increase the quality of obtained data. The recovery study was performed. The LOQs are below recommendations related to the use of brines in balneology.     

Double resonance laser-induced fluorescence of Cadmium and Zinc in the inductively coupled plasma and electrothermal atomizer

Double resonance laser-induced fluorescence (LIF) spectrometry studies of Zn and Cd have been performed in the inductively coupled plasma (ICP) and electrothermal atomizer (ETA). Stepwise excitation of Zn is accomplished at 213.856 nm and 636.235 nm with fluorescence emissions observed near 334.5 nm. Excitation of Cd is accomplished at 228.802 nm and 643.847 nm with fluorescence emissions observed near 361.1 nm and 347.6 nm. Calibration studies demonstrate that the double resonance LIF approaches provide high sensitivity and linearity over several orders of magnitude in both atomizers. Limits of detection for Zn and Cd in the ICP are 1.7 ng/ml and 5 ng/ml, respectively. Excellent sensitivity is observed in the ETA resulting in limits of detection of 70 pg/ml (700 fg absolute mass) and 4 pg/ml (40 fg absolute mass) for Zn and Cd, respectively. The Zn content of a bovine serum standard reference material (NIST SRM #1598) has been determined by ETA-LIF and found to be 940±60 ng/g, which is in very good agreement with the certified value of 890±60 ng/g. Low-level ETA-LIF measurements of Zn in these studies are strongly limited by the high background level observed for this element.     

Revised Method for Determination of Aspirin and Salicylic Acid in Human Plasma by High Pressure Liquid Chromatography

Abstract

The method for the analysis of aspirin and salicylic acid in human plasma has been updated to include advances in column technology, extraction procedures and absorbance detection. Aspirin and salicylic acid are extracted from acidified plasma into an organic solvent system containing internal standard. Following controlled evaporation under partial vacuum of the organic extract, the dried down-residue is reconstituted with mobile phase. Chromatography is ion suppression reverse phase on a 5 μm O.D.S. column with detection by absorbance at 237 nm and optional fluorescence. Concentration of aspirin as low as 0.20 μg/ml and salicyclic acid as low as 0.50 μg/ml can be quantitated.