Verónica Arancibia

Determination of chromium in urine samples by complexation–supercritical fluid extraction and liquid or gas chromatography

A method was developed for the determination of chromium as the Cr(acac)(3) complex in urine using SFE and chromatography. Quantitative extractions were achieved when the experiments were carried out under 3000 p.s.i. of pressure, at a temperature of 120 degrees C, with 2.0 ml of methanol, 30 min of static extraction and 5 min of dynamic extraction. The chromium was quantified by GC-FID detection. The calibration graph of Cr(acac)(3) solutions was linear between 0.50 and 43.0 microg ml(-1) of chromium (DL 0.18 microg ml(-1), R=0.9994). The same extracts were quantified by HPLC-340 nm detection. The calibration curve of the Cr(acac)(3) solutions was linear over a range of 0.013 to 60.0 microg ml(-1) (DL 0.02 microg ml(-1), R=0.9999). This method was applied to urine samples from 60 diabetic patients and 21 healthy volunteers. Chromium concentration ranges were 2.5-29.5 microg l(-1) for the diabetics and 5.9-12.3 microg l(-1) for the normal subjects.

Characterization of copper in uterine fluids of patients who use the copper T-380A intrauterine device.

BACKGROUND The copper intrauterine device (IUD) is a highly effective method of contraception that requires the dissolution of the copper into uterine cavity. However, there is little information about the amount and form of copper in the fluid and whether the presence of this element produces any change in the protein concentration. METHODS Twenty-seven women were divided into three groups that had used IUD for about 6 months, 1 year and > or =3 years. The samples were collected during the proliferative phase (Pp), secretory phase (Sp) and menstruation (M). Square-wave anodic stripping voltammetry (SWASV), cyclic voltammetry (CV), high performance liquid chromatography (HPLC) and atomic absorption spectrometry (AAS) were used in this study. RESULTS Total copper concentrations were between 3.9 and 19.1 micro g/ml. The mean and standard deviations were as follows: 6 months, 11.4+/-4.7 micro g/ml of copper; 1 year, 11.5+/-7.0 micro g/ml of copper; and 3 years, 6.2+/-1.5 micro g/ml of copper. Total proteins were quantified by measuring the area under the chromatographic peaks. The mean areas obtained with uterine fluid samples from women who used IUDs for 6 months, 1 year and 3 years were 290,013, 538,934 and 201,863 arbitrary units (AU), respectively. The control sample was only 22323. CONCLUSIONS The amount of copper released from IUD, although high, is in the form of complexes with proteins. IUDs have a constant copper release for at least 6-12 months. Copper(I) was not detected in the fluid. Copper induces a change in the total protein concentration. The amount of copper released and the amount of proteins is slightly larger during the menstrual stage.

Selective oxidants for organometallic compounds containing a stabilising anion of highly reactive cations: (3,5(CF3)2C6H3)4B−)Cp2Fe+ and (3,5(CF3)2C6H3)4B−)Cp*2Fe+

A major interest in ferrocenium compounds arises from their usefulness as selective oxidants to prepare mixed-valence metallocenic stable compounds. In this paper, Cp 2 FeBAr′ 4 =((3,5(CF 3 ) 2 C 6 H 3 ) 4 B − )Cp 2 Fe + ) ( a ), and Cp* 2 FeBAr′ 4 =((3,5(CF 3 ) 2 C 6 H 3 ) 4 B − ) Cp* 2 Fe + ) ( b ) are reported. These compounds have wide applications in the obtention of new organometallic salts with improved stability. The selective oxidation capacity of compounds a and b was investigated by the reaction of [Cp*Co II (C 8 H 6 )Fe II (C 8 H 7 )] with stoichiometric quantities of Cp 2 FeBAr′ 4 or Cp* 2 FeBAr′ 4 where [Cp*Co III (C 8 H 6 )Fe II (C 8 H 7 )]BAr′ 4 was exclusively obtained. All salts that have BAr′ 4 − as counterion showed an enhanced solubility in low-polarity solvents, especially in diethyl ether. This fact allowed us to perform non-conventional measurements like cyclic voltammetry in diethyl ether as solvent with NaBAr′ 4 as supporting electrolyte. Single-crystal structural determination of a and b was also achieved.

Determination of iron in water samples by adsorptive stripping voltammetry with a bismuth film electrode in the presence of 1-(2-piridylazo)-2-naphthol

An adsorptive stripping voltammetry method for the determination of iron has been developed. The procedure is based on the adsorptive collection of a complex of iron with 1-(2-piridylazo)-2-naphthol (PAN) on a bismuth-coated glassy carbon electrode (BiFE). Factors affecting the stripping performance, such as pH, PAN concentration (C(PAN)), potential, accumulation time (E(ads), t(ads)), and interference by other ions were also studied. The optimum conditions were obtained in a 0.1 mol L(-1) acetate buffer at pH 4.0, C(PAN) 5.0 micromol L(-1), t(ads) 60 s, E(ads) -400 mV, pulse height 4.0 mV, pulse amplitude 25 mV, and frequency 15 Hz. The detection limit was found to be 0.1 microg L(-1) when a t(ads) of 60 s was used, and the linear range was from 0.4 to 60.0 microg L(-1). The proposed procedure was validated by determining of Fe(III) in CRM-MFD, QCS-19 and CRM-SW certified reference materials and applied in seawater samples with satisfactory results.

Studies on quinones. Part 45: Novel 7-aminoisoquinoline-5,8-quinone derivatives with antitumor properties on cancer cell lines

A variety of 7-aminoisoquinoline-5,8-quinone derivatives were prepared from 2,5-dihydroxyacetophenone, methyl aminocrotonate, and the corresponding amines, through a highly efficient three-step sequence. The members of this series were tested on normal human fibroblasts and on a panel of three human cancer cell lines and their redox properties were determined by cyclic voltammetry in acetonitrile. Both the cytotoxicity and antitumor activity of 7-phenylaminoisoquinoline-5,8-quinone derivatives showed correlation with their half wave potentials and lipophilicities.

Determination of aluminium in water samples by adsorptive cathodic stripping voltammetry in the presence of pyrogallol red and a quaternary ammonium salt.

A fast, sensitive and selective method for the determination of aluminium based on the reaction of the metal with pyrogallol red (PR) in the presence of tetrabutylammonium tetrafluoroborate (TBATFB) to form an Al(PR)(3)x9TBATFB complex which is adsorbed on the mercury electrode is presented. Under these conditions complexation of aluminium is rapid and no waiting period or heating of the sample is required. The reduction current of the accumulated complex is measured by scanning the potential in the cathodic direction. The variation of peak current with pH, adsorption time, adsorption potential, ligand and quaternary ammonium salt concentration, and some instrumental parameters, such as stirring rate in the accumulation stage, and step amplitude, pulse amplitude and step duration while obtaining the square wave voltamperograms were optimized. The best experimental parameters were pH 8.5, (NH(4)Ac-NH(3) buffer), C(PR)=25mumolL(-1), C(TBATFB) over 75mumolL(-1), t(ads)=60s, and E(ads)=-0.60V versus Ag/AgCl. A linear response is observed over the 0.0-30.0mugL(-1) concentration range, with a detection limit of 1.0mugL(-1). Reproducibility for 9.0mugL(-1) aluminium solution was 2.3% (n=6). Synthetic sea water and sea water reference material CRM-SW were used for validation measurements. Aluminium in urine samples of a volunteer who ingested 800mg of Al(OH)(3) was analyzed.

Adsorptive stripping voltammetry of nickel with 1-nitroso-2-napthol using a bismuth film electrode

A sensitive procedure is presented for the voltammetric determination of nickel. The procedure involves an adsorptive accumulation of nickel 1-nitroso-2-napthol (NN) complex on a bismuth film electrode prepared ex situ by electrodeposition. The most suitable operating conditions and parameters such as pH, ligand concentration (C(NN)), adsorptive potential (E(ads)), adsorptive time (t(ads)), scan rate and others were selected and the determination of nickel in aqueous solutions using the standard addition method was possible. The adsorbed Ni-NN complex gives a well defined cathodic stripping peak current at -0.70 V, which was used for the determination of nickel in the concentration range of 10.0-70.0 μg L(-1) (pH 7.5; C(NN) 6.5 μmol L(-1); E(ads) -0.30 V; t(ads) 60s) with a detection limit of 0.1 μg L(-1). The relative standard deviation for a solution containing 10.0 μg L(-1) of Ni(II) was 3.5% (n=4). The proposed method was validated determining Ni(II) in certified reference waste water (SPS-WW1) and Certified Reference Water for Trace Elements (TMDA 51.3) with satisfactory results. Then lake water samples were analyzed.

Nafion–mercury coated film electrode for the adsorptive stripping voltammetric determination of lead and cadmium in the presence of pyrogallol red

An adsorptive stripping voltammetric (AdSV) method is presented for the simultaneous determination of Pb(II) and Cd(II) at trace levels in natural waters, based on metal complexation with pyrogallol red (PR) and subsequent adsorptive deposition on a Nafion-mercury coated glassy carbon electrode (NHgFE). Pyrogallol red forms complexes with a metal:ligand stoichiometry of 1:1 with Pb(II) and of 1:2 with Cd(II). Optimal analytical conditions were pH 4.0 (acetate buffer); C(PR)=2.8 μmol L(-1); E(ads)=-0.40 V vs. Ag/AgCl; t(ads)=100 s. The linear calibration curves ranged from 1.0 μg L(-1) to 16.0 μg L(-1) for Pb(II) and from 1.0 μg L(-1) to 13.0 μg L(-1) for Cd(II). The detection limits (S/N=3) were 0.05 μg L(-1) for Pb(II) and 0.01 μg L(-1) for Cd(II). The relative standard deviation was 1.0% and 2.0% (n=7), respectively, for a solution containing 5.0 μg L(-1) Pb(II) and Cd(II). The method was validated by determining Pb(II) and Cd(II) in certified reference waste water (SPS-WW1). Finally, the method was applied to the determination of Pb(II) and Cd(II) in commercial mineral water samples after UV digestion.

Development of a methodology for the simultaneous determination of inorganic and organolead compounds using supercritical fluid extraction followed by gas chromatography–mass spectrometry and its application to environmental matrices

A method for the extraction of triethyl lead (TEL(+)), trimethyl lead (TML(+)), and Pb(2+) from sand was developed using supercritical modified CO(2)-CH(3)OH extraction and in situ complexation with sodium diethyldithiocarbamate (NaDDTC) using a 2(5) factorial exploratory design is described. The screened variables were (i) pressure (69-193 bar), (ii) temperature (40-150 degrees C), (iii) ligand amount (0-100 mg), (iv) methanol volume (0.0-0.5 mL) and (v) static time (0-45 min). The optimum extraction conditions found were as follow: pressure, 193 bar; temperature, 40 degrees C; amount of NaDDTC, 100 mg; methanol volume, 0.5 mL; static time 45 min; and CO(2) flow rate, 1 mL min(-1). Under these conditions the following recoveries were obtained (TML(+) 97+/-2%, TEL(+) 70+/-5%, and Pb(2+) 100+/-4%). The presence of NaDDTC is not necessary for the extraction of TML(+) and TEL(+), but it is a very significative parameter for Pb(2+). A second experimental design 2(2)+star for temperature and pressure was realized, but the results were not better than those of the first model. SFE extract derivatization was achieved with pentylmagnesium bromide, and target analyte determination was carried out by gas chromatography-mass spectrometry. Detection limits in the full-scan mode were 4, 10, and 39 pg as lead for TMPeL, TEPeL and PbPe(4), respectively. The method was validated with urban dust containing TML(+) (CRM 605. Pb 7.9 +/-1.2 microg kg(-1)) and river sediment containing inorganic lead (GBW08301. Pb 79.0+/-12.0 mg kg(-1)) as reference materials. The proposed method was applied to lead analysis in sand collected from an oil-polluted beach in Chile.

Extraction of arsenic as the diethyl dithiophosphate complex with supercritical fluid and quantitation by cathodic stripping voltammetry.

The separation of arsenic based on in situ chelation with ammonium diethyl dithiophosphate (ADDTP) has been carried out using methanol-modified supercritical CO(2). Aliquots of extract were added to an electroanalytical cell and arsenic was determined by square wave cathodic stripping voltammetry (SWCSV) at a hanging mercury drop electrode (HMDE). Quantitative extractions of As(DDTP)(3) were achieved when the experiments were carried out at a pressure of 2500psi, a temperature of 90 degrees C, 2.0mL of methanol, 20.0min of static extraction and 5.0min of dynamic extraction in the presence of 18mg of ADDTP. Analysis of arsenic was made using 150mgL(-1) of Cu(II) in 1M HCl solution as supporting electrolyte in the presence of ADDTP as ligand. Preconcentration was carried out by deposition at a potential of -0.50V and the intermetallic compound Cu(x)As(y) was reduced at a potential of -0.77 to -0.82V, depending on ligand concentration. The results showed that the presence of ligand plays an important role, increasing the methods sensitivity and preventing the oxidation of As(III). The calibration graph of the As(DDTP)(3) solution was linear from 0.8 to 12.5mugL(-1) of arsenic (LOD 0.5mugL(-1), R=0.9992, t(acc)=60s). The method was validated using carrot pulp spiked with arsenic solution. This method was applied to the determination of arsenic in samples of carrots, beets and irrigation water. Arsenic in beets was: skin 4.10+/-0.18mgkg(-1); pulp 3.83+/-0.19mgkg(-1) and juice 0.71+/-0.09mgL(-1); arsenic in carrots was: skin 2.15+/-0.09mgkg(-1); pulp 0.59+/-0.11mgkg(-1) and juice 0.71+/-0.03mgL(-1). Arsenic in water were: Chiu-Chiu 0.08mgL(-1), Inacaliri 1.12mgL(-1), and Salado river 0.17+/-0.07mgL(-1).