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The development of a methodology for the determination of Se(IV) concentration via cathodic stripping voltammetry is described in this work. The methodology is based on the formation of copper selenide (Cu2Se), whose reduction signal at −0.60 V has been used as an analytical response to quantify the Se(IV) concentration in solution. The novelty of our methodology is the study of this system in the presence of a ligand such as ammonium diethyl dithiophosphate (ADTTP), which forms complexes with Cu(II) and Se(IV). The results showed that the presence of ADTTP plays an important role, increasing the sensitivity of the determination by almost a factor of two compared with the methodology in the absence of the ligand. The optimized conditions were pH 1.6 (phosphoric acid, 2.0 × 10−2 mol L−1), CCu(II) = 1.5 mg L−1, CADTTP = 2.0 μmol L−1, Eacc = −0.40 V and tacc = 45 s. The detection and the quantification limits obtained were 0.065 and 0.21 μg L−1, respectively, and linearity was maintained up to 4.0 μg L−1 of Se(IV). The sensitivity was 10.26 nA L μg−1. On the other hand, the relative standard deviation for 15 replicate measurements at 1.0 μg L−1 of Se(IV) was 1.6%. The usefulness of the method was evaluated by determining Se(IV) in two certified reference materials (TMDW and TM−28.4) with relative errors of less than 2.0%. The proposed method was successfully applied to the determination of Se(IV) in spiked tap water and in a liquid pharmaceutical formulation with satisfactory results. The developed methodology presents a low detection limit, good repeatability, selectivity and linear range. Furthermore, the sensibility of the method was achieved by applying a short accumulation time (45 s).

This study presents for the first time a new composite of carbon paste (CP), single-walled carbon nanotubes (SWCNTs) and Nd2O3 (NdOX). This versatile composite (NdOX-SWCNT/CPE) was applied to the oxidation of paracetamol (PCM). The newly formed surface was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results showed greater conductivity and a higher surface area for the composite than those of the carbon paste alone. Moreover, the anodic peak currents for PCM increased from 1.6 to 3.6 µA with CPE and NdOX-SWCNT/CPE, indicating an increase of nearly 51.0% for the anodic peak current. On the other hand, the anodic peak potentials shifted from 0.67 to 0.57 V. The detection limits were 0.05 µmol/L with NdOX-SWCNT/CPE and 0.50 µmol/L with SWCNT/CPE. The relative standard deviations (RSDs) were 1.5% (n = 7). The accuracy and interference of the methods were evaluated with a urine chemistry control spiked with known quantities of PCM, uric acid, dopamine, ascorbic acid, caffeine, acetylsalicylic acid, tartrazine, sunset yellow, allure red, rutin, morin and metal ions. Finally, the novelty and usefulness of the composite were evaluated to quantify PCM in pharmaceutical dosage forms such as tablets, powders and syrups for children., Highlights • A sensitive and selective method for the determination of paracetamol decorated is presented. • The method is based on the oxidation of this substance used in medicinal products. • Other substance used simultaneously with paracetamol not cause interference. • The real samples did not need a previous treatment before the analysis.

An adsorptive stripping voltammetric method for the determination of As(III) and Astotal in water samples using a carrageenan modified carbon paste electrode is presented for the first time (CAR−CPE). The modified electrode was prepared in different ways: by adding CAR in solid form or as a hydrogel together with graphite and paraffin, as well as adsorbing CAR by applying a potential on an unmodified carbon paste electrode. The best results were obtained when CAR was incorporated as hydrogel (HCAR−CPE). The selection of the ratio amounts for electrode preparation was carried out applying a multivariate experimental design. Variables like amount of graphite (U1), HCAR (U2) and paraffin (U3) were optimized using a (2K+2K+C) model. The results showed that the amount of HCAR was the most significant factor, and the adequate U1:U2:U3 ratio to prepare the electrode was: 493 mg of graphite, 214 μL of paraffin and 134 μL of carrageenan as gel. The optimum parameters for the determination of As(III) were pH = 3.25 (0.01 mol L−1 H3PO4/H2PO4− solution); Eacc = −0.50 V and tacc = 30 s. The electrode presents good linear behavior concentration range from 0.50 to 6.70 μg L−1, with a limit of detection of 0.22 μg L−1. The relative standard deviation was 5.0% at the 1.5 μg L−1 As(III) level (n = 16). The method was validated by quantifying As(III) in spiked tap water from laboratory (RE: 3.0%), and it was applied for the determination of Astotal in water samples from the Loa River (North of Chile) prior reduction of As(V) with Na2S2O3 solution, obtaining 814.00 ± 0.03 μg L−1. The results of the proposed method were compared with those obtained by adsorptive stripping voltammetry with HMDE and by Inductively Coupled Plasma Mass Spectrometry (ICP−MS) techniques.

The determination of Mo(VI) in water samples by electroanalytical techniques has been studied previously. Special attention has been paid to catalytic adsorptive stripping voltammetry (cAdSV) due to the high sensitivity and low detection limits achieved with this technique. In this work, a fast and sensitive method was optimized and developed for Mo(VI) determination by cAdSV. The method is based on the accumulation of the Mo(VI) complex with 5–chloro–7–iodo–8–hydroxyquinoline (Clioquinol, CQ) and its reduction on the electrode surface in the presence of KBrO3. An increase of the intensity of the reduction signal of the complex in the presence of potassium bromate was observed (catalytic effect). The effects of different experimental conditions on the signal response were studied. These were optimized to obtain the highest sensitivity. The optimal conditions were pH: 4.4 (acetate buffer), potassium bromate concentration (CKBrO3): 1.8 × 10−2 mol L−1, CQ concentration (CCQ): 1.5 × 10−5 mol L−1, accumulation potential (Eacc): −0.10 V and accumulation time (tacc): 10 s. Under the optimal conditions, the repeatability was 5.4% (RSD) for 20 successive assays with a 200 ng L−1 solution of Mo(VI). The detection limit (DL) was 3.1 ng L−1, the quantification limit (QL) was 10.3 ng L−1 and linearity was maintained up to 580.0 ng L−1. Studies of the interference were made for 29 foreign metal ions in the presence of 1,2−cyclohexylenedinitrilo tetraacetic acid (CDTA) and fluoride ion as masking agents. The accuracy of the methodology was evaluated using three different water certified reference materials with different Mo(VI) concentrations and matrix compositions. The method was applied to the determination of Mo(VI) in tap water, river water from a mining zone in the north of Chile and purified bottled water with satisfactory results.

A new probe (E)-7-(diethylamino)-3-(3-(thiophen-2-yl)acryloyl)-2H-chromen-2-one (ChC16) was synthesized and studied as a turn-on fluorescent probe, based on a Michael addition mechanism for sensing SO2 derivatives, which is favored in the presence of cationic micellar media such as cetylpyridinium bromide (CPB). The probe showed high selectivity and sensitivity toward bisulfite over other anions and biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), with a detection limit of 240 nM. Moreover, the probe showed great potential for its practical application in the detection of bisulfite in real samples, such as dry white wine, and in bioimaging.

In this work, two isoxazole derivatives ( 1 and 2 ) were synthesized and characterized using common spectroscopic tools. The chemosensor behavior of 1 and 2 toward various analytes was explored and we found that both probes follow a ‘switch-off’ mechanism during SO 2 -derivatives sensing, with limits of detection near 10 −6 and 10 −5 M, respectively. A recognition mechanism is proposed, based on a Michael-type addition reaction toward the probes, induced by SO 2 -derivatives and favored by micellar media. Typical interferences like glutathione (GSH) and cysteine (Cys) were inhibited by the presence of the cationic micelles of cetylpyridinium bromide (CPB) and the zwitterionic micelle of sulfobetaine (SB3-14); the detection limits were considerably improved. Thus, on the basis of these results, it is suggested that the use of these kinds of surfactants can be considered as a strategy for optimizing the detection of sulfite via its addition reaction to activated olefins containing isoxazole. Finally, probe 1 was chosen as the best sensor since it was assessed to detect SO 2 -derivatives in real samples (red and white wines) and in a biological system (Caco-2 cells) with very good results.

A electrochemical biosensor for As(III) determination has been developed by immobilization of the Alcaligenis faecalis bacteria on gold nanoparticle–modified screen–printed carbon electrode (AuNPs–SPCE). The detection of As(III) is due to the catalytic activity of arsenite oxidase enzyme which oxidizes As(III) to As(V) producing an analytical signal. To enhance the performance of the biosensor, was optimized the amount of bacteria, amount of glutaraldehyde and incubation time applied in the preparation of the electrode, in addition to the effect of pH and applied potential. The analytical application was carried out applying 300 mV (pH = 7) obtaining a LOD of 6.61 μmol L−1 (R = 0.9975) and 700 mV (pH = 12) obtaining a LOD of 1.84 μmol L−1 (R = 0.9983). AF/AuNPs–SPCE was applied to the determination of total arsenic in Loa river water samples after reduction, with satisfactory results.

A simple and fast anodic voltammetric method was employed to determine traces of As(III) in urine samples using commercial screen–printed graphene electrodes without subsequent modification. To obtain a sensitive and selective method for As(III) determination, the effects of various parameters such as pH, supporting electrolyte concentration, accumulation potential (Eacc), accumulation time (tacc), and potential scan conditions were studied. The optimum experimental conditions were chosen to be as follows: pH of 2.8 (0.01 mol L−1 phosphate buffer), scan increment of 4 mV, pulse width of 80 ms, pulse period of 0.5 s, and pulse amplitude of 200 mV. Differential pulse voltammograms were obtained by scanning from −0.80 V to 0.80 V without applying an accumulation step. Under these conditions, one peak was observed at 0.27 V due to As0 oxidation. After optimizing the experimental conditions, the anodic peak current for As was found to be linearly related to its concentration up to ca. 5.0 μg L−1, with detection and quantitation limits (DLs, QLs) of 0.28 µg L−1 and 0.92 µg L−1, respectively. The developed method was validated by the determination of As(III) in spiked tap water from our laboratory, which showed an As(III) concentration of 50.64 ± 0.10 μg L−1 (spiked with 50.0 μg L−1); two urine samples (where As was not detected) spiked with As(III) 0.73 μg L−1 and 0.91 μg L−1 (in the cell) showed an As(III) concentration of 0.70 μg L−1 and 0.91 μg L−1, respectively. The method was successfully applied to the determination of Astotal in 16 urine samples obtained from workers occupationally exposed to inorganic arsenic compounds without previous treatment. The results obtained for Astotal were compared with measurements made by an external analytical laboratory, which used HG–AAS. To determine Astotal, As(V) was reduced in the presence of thiosulfate in an acid medium. The electrode showed good stability and repeatability.

Using the differential pulse anodic stripping voltammetry technique and an in-situ bismuth film deposited on a glassy carbon electrode, a simple and sensitive method for rapid Pb(II) and Cd(II) quantification was developed. The effect of the presence of Alizarin Red S (ARS) was studied, and an increase in the sensitivity of the method was obtained. The developed method was compared to another reported method that uses a 0.1 mol L−1 acetate buffer medium (pH 4.5). The optimal experimental conditions are listed as follows: [CH3COOH]: 30.0 mmol L−1; [Bi(III)]: 0.75 mg L−1; [ARS]: 40.0 µmol L−1; [Fe(CN)64−]: 50.0 µmol L−1; Edep: −1.40 V; tdep: 60 s. Under these conditions, the detection limits were 0.16 and 0.09 µg L−1 and the linearity was maintained at values as great as 30.0 and 15.0 µg L−1 for Pb(II) and Cd(II), respectively. The effect of 35 foreign ions as possible interferents was studied. The method was validated using two certified reference materials (TMDW and TMDA-61.3) with satisfactory results. Finally, the method was applied for the analysis of four natural water samples.

The determination of Sb(III) on an ex-situ bismuth screen-printed carbon electrode (ex-situ BiSPCE) by means of adsorptive stripping voltammetry (AdSV) using quercetin-5′-sulfonic acid as chelating agent was optimized. The effect of different experimental parameters such pH, ligand concentration (CQSA), accumulation potential (Eacc) and accumulation time (tacc) were studied to obtain a wide linear range, the highest sensitivity and the lowest detection limit. Ex-situ BiSPCE was analytically compared with a sputtered bismuth screen-printed electrode (BispSPE) under optimal conditions. The obtained analytical parameters suggest that ex-situ BiSPCE behaves much better than BispSPE and the first was selected for this study. Optimal parameters were pH=4.6; CQSA=10.0 to 20.0×10−6 mol L−1; Eacc=−0.5 V and tacc=60 s. Peak area is proportional to Sb(III) concentration up to 100.0 μg L−1 (tacc 60 s) and 45.0 μg L−1 (tacc 120 s) range, with detection limits of 1.2 μg L−1 (tacc 60 s) and 0.8 μg L−1 (tacc 120 s). The relative standard deviation for a Sb(III) solution (20.0 μg L−1) was 3.9% for ten successive assays. Thus, the effect of various interfering metal ions was studied and the methodology was validated using a spiked groundwater reference material with very satisfactory results.

A sensitive method for the determination of arsenic based on the formation of their complexes with ammonium pyrrolidine dithiocarbamate (APDTC) or ammonium diethyl dithiophosphate (ADDTP) prior to the formation of the intermetallic compound (Cu x As y ) whose reduction is directly related to As(III) concentration is presented. The effects of various operational parameters such as HCl, Cu(II) and ligand concentrations (C HCl , C Cu(II) , C APDTC , C ADDTP ); accumulation potential and time (E ads , t ads ) were optimized. The optimum experimental conditions chosen were C HCl : 1.25 and 2.00 mol L − 1 ; C Cu(II) : 60 and 40 mg L − 1 ; E ads : − 0.40 and − 0.30 V; and t ads : 80 and 60 s for APDTC and ADDTP, respectively. On the other hand, the optimum ligand concentrations were 0.20 and 1.50 μmol L − 1 for APDTC and ADDTP, respectively (C As(III) : 15.00 μg L − 1 ). It was found that in the presence of cetylpyridinium bromide (CPB) the peak current of the arsenic signal is higher than in the absence of this cationic surfactant, and these values attained a maximum at 7.8 and 2.6 μmol L − 1 for APDTC and ADDTP, respectively. Under these conditions, the reduction signals of Cu x As y are found at − 0.82 V and − 0.64 V for APDTC and ADDTP, respectively. The relationship between peak current and As(III) concentration is linear in the 0.50–3.00 μg L − 1 (APDTC) and 2.50–15.00 μg L − 1 (ADDTP) range. The detection limits (DLs) were found to be 0.08 and 0.27 μg L − 1 for APDTC and ADDTP, respectively (t ads : 30 s). The relative standard deviations for 30 replicate measurements at the lowest level of each method, 0.10 μg L − 1 for APDTC and 2.00 μg L − 1 for ADDTP, were 3.9 and 25.2%, respectively. The results showed that the presence of ligand plays an important role, improving the signal current of As(III) and preventing the oxidation of As(III) to As(V), achieving the best sensitivity and repeatability when APDTC was used. Finally, the method was validated using synthetic drinking water spiked with As(III) and was applied to the determination of total arsenic in water from the Loa River (North of Chile) with satisfactory results.

Catalytic adsorptive stripping voltammetry has been a powerful technique for trace metal determination. We now report one of the most sensitive voltammetric methods developed for vanadium. The determination is based on the complexation of vanadium with quercetin-5-sulfonic acid (QSA), adsorption of V(V)-QSA and reduction to V(III)-QSA onto HMDE; and finally in the scan step electrochemical reduction of V(III)-QSA to V(II) at about −0.78 V applying differential pulse catalytic adsorptive stripping voltammetry. With the aim of comparing the effect of the sulfonic group on the sensitivity of the determination, two methods were developed using quercetin (Q) and Quercetin-5-sulfonic acid (QSA) as complexing and adsorbing ligands. The effects of various operational parameters such as pH, ligand, and potassium bromate concentration (C Q , C QSA , C KBrO3 ), potential, and adsorption time ( E ads , t ads ) were optimized. The best results were obtained with QSA, and the optimal experimental parameters were pH: 7.0; C QSA : 0.6 × 10 −6 mol L −1 , C KBrO3 : 3.5 × 10 −2 mol L −1 , E ads : 0.0 V, and t ads : 30 s. Under the best experimental conditions the RSD for a V(V) solution (0.1 μg L −1 ) was 3.4% for ten successive assays. Linearity was maintained up to 0.35 μg L −1 and the detection limit was 0.23 ng L −1 ( t ads : 30 s; C QSA : 0.6 × 10 −6 mol L −1 ). The method was validated using certified reference water (TMDA – 61.2) and finally, the method was applied to the determination of vanadium in tap water, purified drinking water, river water, and commercial water for chromatography.

The development of a method for molybdenum(VI) determination in the presence of quercetin‒5′‒sulfonic acid (QSA) using a mercury‒free electrode is presented. Adsorptive stripping voltammetry is the electroanalytical technique used and an ex‒situ bismuth screen‒printed carbon electrode (BiSPCE) is the working electrode. The conditions for the bismuth film deposition were optimized and the different films were compared using field emission scanning electron microscopy. Different experimental parameters were optimized to obtain a sensitive, selective, and reproducible method. The best experimental parameters were: pH 5.8, ligand concentration: 30.0 µmol L−1; accumulation potential: −0.4 V, and accumulation time: 10 s. The detection and quantification limits obtained were 0.7 and 2.1 µg L−1, respectively. The linearity of the method was maintained in the range of 2.1 to 90.0 µg L−1. The possible interference of 36 foreign ions was studied. The method was validated with two certified water reference materials and synthetic seawater spiked with Mo(VI). The method was applied to determine the Mo(VI) concentration in tap water, groundwater, bottled mineral water, and seawater samples. The results were compared with measurements performed by an external analysis laboratory via ICP‒OES. The present work is an alternative method for molybdenum determination by an electroanalytical method, avoiding the use of mercury as electrode material. Additionally, the time required for sample analysis is fast due to the application of only 10 s in the accumulation step.

This work reports the development of a composite of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BP4) and chitosan (CS) described in previous reports through a new method using cyclic voltammetry with 10 cycles at a scan rate of 50.0 mV s&minus, 1. This method is different from usual methods such as casting, deposition, and constant potential, and it allows the development of an electroactive surface toward the oxidation of rutin by stripping voltammetry applied to the detection in tropical fruits such as orange, lemon, and agraz (Vaccinium meridionale Swartz), with results similar to those reported in previous studies. In addition, the surface was characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and Raman spectroscopy. The limit of detection was 0.07 &micro, mol L&minus, 1 and the relative standard deviation (RSD) of 10 measurements using the same modified electrode was 0.86%. Moreover, the stability of the sensor was studied for six days using the same modified electrode, where the variation of the signal using a known concentration of rutin (RT) was found to be less than 5.0%. The method was validated using a urine chemistry control spiked with known amounts of RT and possible interference was studied using ten substances including organic and biological compounds, metal ions, and dyes. The results obtained in this study demonstrated that this electrodeveloped composite was sensitive, selective, and stable.

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A fast, sensitive, and selective method for the simultaneous determination of one pair of synthetic colorants commonly found mixed in food products, Amaranth (AM) and Tartrazine (TZ), based on their adsorption and oxidation on a screen-printed electrode (SPE) is presented. The variation of peak current with pH, supporting electrolyte, adsorption time, and adsorption potential were optimized using square wave adsorptive voltammetry. The optimal conditions were found to be: pH 3.2 (PBS), Eads 0.00 V, and tads 30 s. Under these conditions, the AM and TZ signals were observed at 0.56 and 0.74 V, respectively. A linear response were found over the 0.15 to 1.20 µmol L−1 and 0.15 to 0.80 µmol L−1 concentrations, with detection limits (3σ/slope) of 26 and 70 nmol L−1 for AM and TZ, respectively. Reproducibility for 17.7 µmol L–1 AM and TZ solutions were 2.5 and 3.0% (n = 7), respectively, using three different electrodes. The method was validated by determining AM and TZ in spiked tap water and unflavored gelatin spiked with AM and TZ. Because a beverage containing both AM and TZ was not found, the method was applied to the determination of AM in a kola soft drink and TZ in an orange jelly and a soft drink powder.

A sensitive and selective method for the determination of Sb3+ based on the formation of its complexes with 8-hydroxyquinoline (HQ) and 8-hydroxyquinoline-5-sulfonic acid (HQS) is proposed. The best analytical conditions are: pH 5.4 and 2.2 for HQ and HQS, respectively; CHQ from 15.0 to 25.0 µmol L−1 and CHQS from 70.0 to 200.0 µmol L−1. The detection limits are 100.0 and 14.0 ng L−1 (tacc=30 s) for Sb3+ with HQ and HQS, respectively. The method using HQS as ligand has a 2.2-fold higher sensitivity than that with HQ and the former was chosen for Sb3+ determination.

This work presents an adsorptive stripping voltammetric method for the determination of Cu(II) at trace levels in foods samples based on metal complexation with α-lipoic acid (LA) and subsequent adsorptive accumulation on mercury electrode. The optimum experimental conditions chosen were 0.6–1.2 μmol L− 1 α-lipoic acid, pH 3.6 (acetate buffer), Eacc of − 0.30 V and tacc of 30 s. In these conditions the signal of Cu–LA complex is observed at − 0.55 V. The relationship between the peak current and copper concentration is linear in the 0.33–65.0 μg L− 1 range. The detection limit was found to be 0.1 μg L− 1 (30 s). The relative standard deviation for 12 replicates measurements of 5.0 μg L− 1 Cu(II) is equal to 2.1%. The method was validated by determining Cu(II) in certified reference waste water (SPS-WW1) and water samples spiked with 18 foreign metal ions. The method was applied to the determination of Cu in sweeteners, sugar, tea, coffee, and mate infusions after UV digestion.

A sensitive and selective method for the simultaneous determination of lead, cadmium and zinc based on the formation of their complexes with Clioquinol (5-chloro-7-iodo-8-hydroxyquinoline, CQ) is described. These studies were carried out using separate copper, lead, cadmium and zinc solutions and also mixtures of them. The optimum pH values were 2.3; 5.1; 5.3 and 5.2 for copper, lead, cadmium and zinc respectively (Britton Robinson buffer 0.03 mol L − 1 ). In addition to optimum pH values, copper not interfere, but simultaneous determination of four elements is not possible. A pH of 5.3, a CQ concentration of 3.6 μmol L − 1 and an accumulation potential of −0.65 V were chosen for the analysis. Copper, lead, cadmium and zinc complexes peak currents were observed at −0.30; −0.41; −0.59 and −0.95 V whereas the free CQ is reduced at –0.80 V. For individual analysis, the relationship between the peak current and metal concentration is linear until 40.0; 31.0 and 70.0 μg L − 1 for lead, cadmium and zinc respectively. However in the simultaneous determination, the relationship is linear until 15.0 μg L − 1 for lead and cadmium and 25.0 μg L − 1 for zinc and the detection limits were found to be 0.10; 0.06 and 0.06 μg L − 1 for lead, cadmium and zinc respectively. The relative standard deviation for 6 replicates determination of 5.0 μg L − 1 lead, cadmium and zinc is equal to 1.8%, 0.9% and 1.6% respectively. The method was validated by determining lead, cadmium and zinc in spiked synthetic sea water (ASTM D665), Ontario lake reference water (TMDA-61.2) and was applied to the determination of these metal ions in tap water, sea water, and mineral water samples.

Nafion combined with ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM]F 3 MSO 3 ) coated with mercury film (NLIHgFE) on a glassy carbon electrode modified allow the determine Pb(II) by adsorptive stripping voltammetry in the presence of Amaranth (Am). Properties of the NLIHgFE were characterized by square wave without and in the presence of other ionic liquid´s with different anion where ([EMIM]F 3 MSO 3 ) showed to be more convenient in the determination the lead compared with other ionics liquids with smaller anions. pH 2.6 with buffer Britton-Robinson the complex Am-Pb was accumulated by adsorption on surface of the working electrode at -0.3 V by 80 s. and later reduce at negative potential by square wave and current peak appeared at -0.51 V earmarked to the reduction of lead in the complex. The linear calibration curves with ranged from 0.9–12.0 µgL –1 for Pb(II). The detection limits (3s) were estimated to be around 0.4 µgL –1 to Pb(II) . The relative standard deviations were 2.0 % at the 4.9 µg L –1 level of Pb(II) with 80 s of accumulation (n=7). Other optimal conditions were (C Am 0.77 µmol L –1 ; E ads –0.3 V; Frecuency 15 Hz and Amplitud pulse 25 mV). The methods were validated using reference material waste waters (SPS–WW1). Finally, the method was successfully applied to the determination of Pb(II) in tap water after UV digestion.

A variety of 6-bromine-containing 7-anilino-1-arylisoquinolinequinones 2a-g were synthesized to evaluate their half-wave potentials and in vitro antiproliferative activity on gastric and leukemia cancer cell lines. The new compounds displayed significant IC50 values in the range: 1.31 to 11.04 μM. The structure activity relationship analysis of the new series suggest that the antiproliferative activity is dependent, in part, on the push-pull electronic effects of the nitrogen and bromine substituents inserted into the redox fragment of the 1-arylisoquinolinequinone scaffold. Linear regression analysis provided satisfactory relationships between the log IC50 and ClogP values for the AGS gastric cancer cell line.

An efficient, fast and sensitive method for the determination of 17β-estradiol, (E2) and 17α-ethinylestradiol (EE2) in pharmaceutical formulations and in urine was developed and validated using a hanging mercury drop electrode (HMDE), screen printed carbon electrodes (SPCE), and screen printed carbon nanotube electrodes (SPCNTE). Both analytes are adsorbed on the working electrodes. To obtain sensitive and selective methods, the effects of various parameters such as pH, adsorption potential, and time (Eads, tads) were optimized. The optimum experimental conditions chosen for the two analytes were pH: 10.0; Eads: −0.60 and tads: 30 s, when HMDE was used. Under these conditions, one reduction signal was found at −1.31 V for E2 and two reduction signals at −0.23 V and −1.20 V for EE2. The detection limits (DLs) were found to be 0.3 μg L−1 for E2, 14.8 μg L−1 for EE2 at −0.23 V, and 9.7 μg L−1 for EE2 at −1.20 V. On the other hand, in screen printed electrodes E2 and EE2 present oxidation of the phenolic hydroxyl groups at 0.30, 0.31, 0.32, and 0.33 V (pH:10) with DLs of 242, 277; 182, and 191 μg L−1 for SPCE and SPCNTE, respectively. The method was successfully applied to the determination of these analytes in Primaquin® (E2), Gynera® (EE2), spiked urine (with EE2), and urine samples of women who used Tinelle® (EE2) as contraceptive drug.

A nafion-coated antimony film electrode (NSbFE) was prepared ex situ and applied to the model metal ions Pb(II) and Cd(II) by adsorptive stripping voltammetry in the presence of pyrogallol red (PGR). To enhance the electroanalytical performance of the NSbFE, we optimized several operational parameters, including antimony concentration, deposition potential and time used in the preparation of the electrode, and effect of pH, ligand concentration (CPGR), adsorptive potential, and time (Eads, tads). The NSbFE exhibited well developed signals for the reduction of the adsorbed complexes at −0.63 and −0.92 V for Pb-PGR and Cd-PGR, respectively, with higher current compared to unmodified electrodes. The optimum parameters for NSbFE preparation consisting of 100 mg L−1 Sb(III), 0.5 mol L−1 HCl at −1.5 V (150 s) and for the determination of Pb(II) and Cd(II) were pH = 4.5 (acetate buffer); CPGR = 2.8 μmol L−1; Eads = −0.40 V and tads = 100 s. The electrode presents good linear behavior in the examined concentration range from 0.9 to 12.0 μg L−1 for both metal ions, with a limit of detection (3σ) of 0.4 and 0.9 μg L−1 for Pb(II) and 0.5 and 1.0 μg L−1 for Cd(II) using 2-mm and 3-mm diameter glassy carbon electrodes, respectively. The relative standard deviation for a Pb(II) a Cd(II) solution (9.8 μg L−1) was 2.0% for six successive assays. The method was validated using certified reference water for trace elements (TMDA-61) with satisfactory results. Finally, the method was applied to the determination of Pb(II) and Cd(II) in tap and mineral water.

A sensitive and selective voltammetric method for simultaneous determination of Sb(III) and Mo(VI) using Quercetin (Q) as complexing agent is described. Optimal conditions were found to be: pH 3.7, CQ = 6.0 mmol L 1 and Eacc =0.10 V. The LOD (3s) for Sb(III) are 0.076 and 0.040 m gL 1 , whereas for Mo(VI) are 0.086 and 0.048 m gL 1 with tacc of 60 and 120 s, respectively. The method was validated using synthetic sea water (ASTM D665) and was applied to the determination of Sb(III) and Mo(VI) in natural waters with satisfactory results.

An efficient, fast and sensitive method for the determination of Sudan I (SI) in drinks containing Sunset yellow (Sy) is developed and validated using an adsorptive stripping voltammetric procedure. Sy is currently added to a large number of foods; however during their synthesis SI may be produced. The determination is based on adsorption of Sy and SI onto HMDE and later reduction of the azo group at -0.71 and -0.82V, respectively. Using the best set of the experimental conditions (pH 12.3; Eads: -0.40V) for the determination of SI in Sy, a linear response for SI in the concentration range 0.5-27.2μgL(-1) was found, with a detection limit of 1.5μgL(-1) in a tads of only 30s. The method was applied to the determination of SI in commercial drinks with satisfactory results. The presence of SI was confirmed by mass spectrometry.

Cadmium concentration in an aqueous medium is quantified using an alginic acid-modified carbon paste electrode. The working electrode was prepared using a homogeneous mixture of graphite powder, alginic acid (AA) and mineral oil. Square wave anodic stripping voltammetry (SWASV) using this modified electrode showed one small well-resolved anodic wave for the oxidation of AA at -0.05 V. This signal shifts toward less positive potential and peak current increases in the presence of CdII. After optimizing the experimental conditions, the anodic peak current of CdII-AA was linearly related to its concentration up to ca. 30.0 µg L-1, with a detection limit of 0.9 µg L-1 at pH 2.0 (HNO3. t acc = 60 s, Eacc = -0.80 V). The method was validated by determining CdII in spiked synthetic sea water (ASTM D665). The modified electrode showed good stability and repeatability. A concentração do cádmio em um meio aquoso foi determinada usando-se um elétrodo de carbono ácido-modificado de pasta de alginina. O elétrodo de trabalho foi preparado usando-se uma mistura homogênea de pó de grafite, alginina ácida (AA) e óleo mineral. A voltametria de onda quadrada com redissolução anódica (SWASV) usando-se este elétrodo modificado, mostrou uma onda anódica bem definida com pequena oxidação do AA em -0,05 V. O sinal é deslocado para um potencial menos positivo e a corrente máxima aumentou na presença do CdII. Após a otimização das condições experimentais, a corrente máxima anódica do CdII-AA mostrou ser linear com sua concentração até ca. 30.0 µg L-1, com limite de detecção de 0.9 µg L-1 em pH 2.0 (HNO3. t acc = 60 s, Eacc = -0.80 V). O método foi validado com a determinação de CdII em água do mar sintética enriquecida (ASTM D665). O elétrodo modificado mostrou boa estabilidade e repetibilidade.

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.

The reaction of the dimer complex [{Ru(CO)3Cl2}2] with the ligands 4,6-dichloroquinoline-5,8-dione and 6-methoxybenzo[g]quinoline-5,10-dione in ethanol solution led to the neutral mononuclear complexes of general formula [Ru(CO)2Cl2(κ2-quinolinedione-N,O)]. The complexes were characterized by elemental analysis, IR and RMN spectroscopy, and the molecular structure of [Ru(CO)2Cl2(6-methoxybenzo[g]quinoline-5,10-dione)] was determined by single-crystal X-ray diffraction. The redox chemistry of ligands and complexes was investigated by cyclic voltammetry, and their potential antitumor activity was also evaluated., We thank the “Fondo de Desarrollo Científico y Tecnológico” (FONDECYT), Chile (Project Nos. 3040053 and 1060597), and Factoria de Cristalización, CONSOLIDER INGENIO-2010 for financial support.

Successful trials with 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol, CQ) for Alzheimer's disease treatment prompted renewed interest in assessing whether its therapeutic action is related to the coordination of neurotoxic trace metals, such as Cu(II) and Zn(II). We now report conditional stability constants (K(C')) for CQ Cu(II) and Zn(II) complexes measured in a biological buffer containing Ca(II) and Mg(II) ions. UV-vis spectroscopy and polarography evidenced a 1:2 stoichiometry of Cu(II) and Zn(II) CQ complexes; the K(C')s calculated were: Cu(CQ)(2) 1.2x10(10), and Zn(CQ)(2) 7.0x10(8)M(-2); the CQ affinity for Cu(II) is at least an order of magnitude higher than for Zn(II). To test the possible functional relevance of the Cu(II) CQ complexes in the brain, we bioassayed free Cu(II) concentration by the metal-induced inhibition of ATP-gated currents of the P2X(4) receptor, a predominant brain P2X receptor. CQ reduced concentration-dependently the Cu(II) inhibition of the ATP-gated currents. In view that the stability constant of CQ for Zn(II) is similar to that of Abeta-amyloid for Zn(II), and the fact that CQ may form complexes with Cu(II), even in the presence of competing ions, the present results highlight that the formation of Cu(II) CQ complexes in the brain may act by diminishing free Cu(II) concentrations modifying thereby brain excitability, or favoring the degradation of beta-amyloid plaques or huntingtin, rather than through a specific effect of CQ itself.

The Mapocho river, which crosses downtown Santiago, is one of the most important rivers in contact with a population of about six million inhabitants. Anthropogenic activities, industrialization, farming activities, transport, urbanization, animal and human excretions, domestic wastes and copper mining have affected the river, contaminating it and its sediments with heavy metals. Concentration and distribution of Cu, Zn, Pb and Cd were studied with the purpose of determining their bioavailability and their relation with the characteristics of the sediments. Freshly deposited seasonal sediments were collected from 0–8 cm depths from 6 locations (S1 to S6) along the 30-km long channel length, in the four seasons of year on the following dates: May 2001 (D1, autumn); August 2001 (D2, winter); October 2001 (D3, spring) and January 2002 (D4, summer). The dried samples were sifted to obtain the

A new fused ring compound 2,9-dimethyl-1,10-dihydro-dicyclopenta[a,h]naphthalene (VI), (H2L), has been synthesized from naphthalic anhydride. Two organometallic binuclear complexes, [Cp*Fe-L-FeCp*] (1) and the mixed valence compound, [ Cp ∗ Fe - L - FeCp ∗ ] + BF 4 - (2) have been characterized by spectroscopic and electrochemical techniques. The structure resolution of (1) by single crystal X-ray diffraction shows that the two organometallic fragments Cp*Fe are in an anti position. Cyclic voltammetry exhibits a potential difference of 348 mV between both redox peaks. The Mossbauer investigation at different temperatures shows a uniform environment for the neutral compound (1) and two sites, assigned to Fe2+ and Fe3+ for the compound (2). The information gathered by all the previously mentioned techniques indicates that the studied binuclear complex belongs to the mixed valence class II complexes according to the classification of Robin and Day.

A method is presented for the extraction of cadmium as the Cd(Ox)2 complex with methanol-modified supercritical CO 2. In a first step, aliquots of Cd 2+ solutions were spiked onto filter paper and air-dried, and the filter paper with cadmium, oxine and methanol was placed in a 10 ml stainless steel extraction vessel. A study was made of extraction as a function of pressure (6.9–24.1 MPa), oven temperature (40–200 ◦ C), restrictor temperature (20–100 ◦ C), presence of modifier (1.0–4.0 ml), and static extraction time (10–50 min). Quantitative extractions of cadmium were achieved when the experiments were carried out at 17.2 MPa, 80–120 ◦ C oven temperature, 60 ◦ C restrictor temperature, 2.0–3.0 ml of methanol, 30 min static extraction, and 5 min in dynamic mode. An aliquot of the extract was placed in an electroanalytical cell that contained a supporting electrolyte, and cadmium was quantified by square wave stripping voltammetry. The calibration graphs using cadmium solutions in the presence of 0.1 M of oxine were linear over a 5.0–120.0 gl −1 range. The detection limits using anodic stripping voltammetry or adsorptive stripping voltammetry were 1.5 and 1.4 gl −1 of cadmium, respectively. The efficiency of the extraction was evaluated using certified reference human hair. The procedure was then applied to cigarette samples and to hair of cigarette smokers and non-smokers. Cadmium concentration ranges were 0.06–0.57 gg −1 (average 0.25 ± 0.18 gg −1 ) for smokers and 0.02–0.26 gg −1 (average

Optimizing operational parameters and obtaining the highest possible recovery are two of the major objectives to be attained when any extraction process is performed on a real sample in which the true analyte concentration is unknown. Sulfadiazine (SDZ), sulfamerazine (SMR), and sulfamethazine (SMZ) were extracted from real samples of chicken liver, beef liver, and pig kidney, using methanol-modified supercritical CO 2 . The optimum extraction parameters were found to be 17.237 MPa and 160 C for two of the three analytes; SMZ, on the other hand, was completely extracted at 120 C. Under these conditions of high temperature, high amounts of modifier (3.0 mL of methanol in a 10-mL extraction vessel) and low pressure, all three sulfonamides (SAs) were shown to be quantitatively extracted from spiked samples from domestic animals which had not been given sulfonamides. Under the same conditions, meat samples of commercial origin were analyzed. These results were compared with those obtained by conventional extraction methods. Almost all the meat samples contained sulfa drug residue levels far exceeding the current tolerance levels allowed for most sulfonamides. Eighteen of thirty samples contained at least one of the three sulfonamides, and seven of these samples contained from 1.1 to 4.2 mg kg -1 of SMZ. The SAs were quantified by HPLC with UV absorbance and amperometric detection.

A procedure is described for the determination of nitrofurantoin and its toxic metabolite in urine from patients with urinary infection using supercritical fluid extraction (SFE) and liquid chromatography. The standard solution of toxic metabolite (radical anion) was obtained by electrochemical reduction of nitrofurantoin in an aprotic medium and chemical reoxidation with oxygen. In our initial SFE studies to find the adequate extraction parameters, drug solutions were impregnated onto filter paper. Quantitative extractions were achieved when the experiments were carried out under 2500 psi of pressure at a temperature of 80 degrees C (oven and restrictor) after 20 min of static extraction and 5 min of dynamic extraction. The modifier used was acetonitrile (2.0 ml in a 10 ml extraction column). Nitrofurantoin and its toxic metabolite were detected in urine samples. Both compounds were quantified in the extracts by high performance liquid chromatography (HPLC) with detection at 310 nm. The calibration graph of these compounds in acetonitrile was linear between 10.9 and 378.0 muM (R=0.9995) for nitrofurantoin and between 3.0x10(-3) and 21.0 muM (R=0.9992) for the metabolite. The detection limits (LOD) were 12.1 and 0.9 muM, respectively. The drug was administered to two patients during 7 days, and all the urine eliminated between 1 day before and 2 days after administration was analyzed. One patient consumed the drug in the form of microcrystals and the other as macrocrystals.

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 ≥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 μg/ml. The mean and standard deviations were as follows: 6 months, 11.4±4.7 μg/ml of copper; 1 year, 11.5±7.0 μg/ml of copper; and 3 years, 6.2±1.5 μg/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 22 323. 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.

Un sensible y simple método electroanalítico es optimizado para la determinación de amaranth por AdSV sobre un electrodo serigrafiado de carbono (Dropsens DRP-154). El amaranth (E123) es depositado por adsorción sobre la superficie del electrodo y el pico de corriente es medido por onda cuadrada (SWV). El electrodo se caracterizó por voltamperometría cíclica (CV) en presencia del surfactante catiónico bromuro de cetilpiridina (CPB) donde el E123 es oxidado a 0,62 V en un proceso controlado por difusión, aumentando en 100% el pico de corriente en presencia de CPB. Las variables experimentales como pH, concentración de surfactante (C ), tiempo de adsorción (tads) y potencial de CPB adsorción (E ), así como también las potenciales interferencias, fueron estudiadas. Bajo las ads -5 -1 óptimas condiciones (pH 2,0; C 1,0x 10 molL ; t 90s; E 0,10 V) el pico de la corriente es CPB acc acc -6 -1 proporcional a la concentración de E123 entre 0,10 to 2,0 x 10 molL , con un límite de -7 -1 detección de 0,18 x 10 molL . La desviación estándar relativa para una solución conteniendo -5 -1 1,0 x 10 molL de E123 fue de 1,0 % para siete medidas iguales. El método fue validado con una muestra de agua dopada con E123. Finalmente el método fue aplicado en la determinación de amaranth en muestras de sodas. A simple and sensitive electroanalytical method is optimized by determining amaranth(E123) by AdSVon a screen printed carbon electrode (Dropsens DRP-154). E123 is deposited by adsorption on the electrode surface and the current peak measured by square wave (SWV). The electrode is characterized by cyclic voltammetry (CV) in the presence of cationic surfactant cetylpyridinium bromide (CPB) where E123 is oxidized to 0.62 V by diffusion, increasing near 100% the peak current in the presence of CPB. The experimental variables such as pH, concentration of surfactant (C ) adsorption time (T ) and adsorption CPB ads potential (E ), as well as potential interference, were studied. Under optimal conditions (pH ads -5 -1 2.0; C 1.x 10 molL ; t 90s; E 0.10 V) the peak current is proportional to the CPB ads ads -6 -1 -7 concentration of E123 between 0.10 to 2.0 x 10 molL , with a detection limit of 0.18 x 10 -1 -5 -1 molL . The relative standard deviation for a solution containing 1.0 x 10 molL of E123 was 1.0% for seven equal measures. The method was validated with a water sample doped with E123. Finally the method was applied in the determination of amaranth in samples of sodas.

The synthesis and properties of new cationic iron(II) complexes of general formula [(η5-C5H5)FeL(η2-dppa)]A [A=I−, L = CO(1); A = BF4, L = CO(2) CH3CN(4), η1-dppa(5); dppa = NH(PPh2)2] are described. The carbonyl complex [(η5-C5H5)Fe(CO)(η2-dppa)]BF4 is deprotonated to give the neutral complex [(η5-C5H5)Fe(CO){η2-(PPh2)2N}](3). All complexes have been characterized by elemental analysis and IR and NMR spectroscopies. Cyclic voltammetry of complexes 1–5 shows a diverse redox chemistry in acetonitrile solution. While the reduction of 1 and 2 leads to the formation of a dinuclear Fe(I) complex, 4 and 5 form mononuclear species of Fe(I); oxidation of metal centers of 1 and 2 is not observed and in complexes 3 and 4 the metal centers are oxidized at potentials < 1. Complex 5 in acetonitrile solution is transformed into complex 4.

Reactions of complexes [{(η 5 -C 5 Me 5 )MCl 2 } 2 ] (M=Rh, Ir) with the ligand (MeS) 2 CH 2 in CH 2 Cl 2 solution led to the neutral dinuclear complexes of the general formula [{(η 5 -C 5 Me 5 )MCl 2 } 2 {μ-(MeS) 2 CH 2 }] [M=Rh ( 1 ), Ir ( 2 )]. Compound 1 reacts in CH 2 Cl 2 solution with silver tetrafluoroborate in 1:2 molar ratio to yield the dinuclear cationic complex [{(η 5 -C 5 Me 5 )Rh} 2 (μ-Cl) 2 {μ-(MeS) 2 CH 2 }](BF 4 ) 2 ·H 2 O ( 3 ). Compound 2 reacts with silver salts in analogous conditions to give the mononuclear cationic complex [(η 5 -C 5 Me 5 )IrCl{η 2 -(MeS) 2 CH 2 }]BF 4 ( 4 ). Reactions of the starting complexes [{(η 5 -C 5 Me 5 )MCl 2 } 2 ] with the ligand (PhS) 2 CH 2 afforded the mononuclear complexes [(η 5 -C 5 Me 5 )MCl 2 (η 1 -(PhS) 2 CH 2 )] [M=Rh ( 5 ), Ir ( 6 )]. All the complexes have been characterised by analytical and spectroscopic means, and the fluxional behaviour of 4 , in solution, has been studied. The crystal structures of complexes 3 and 6 have been established by X-ray crystallography. Complex 3 crystallised in space group P 2 1 / n , a =11.848(2), b =12.693(2), c =21.608(4) A, β =95.18(2)° and Z =4. The complex cation consists of two (η 5 -C 5 Me 5 )Rh moieties connected by two chloride atoms and one dithioether group. The two rhodium atoms are separated by 3.6093(10) A. Complex 6 crystallised in space group P 2 1 / c , a =8.366(1), b =16.011(3), c =17.911(2) A, β =100.28(1)° and Z =4. The iridium atom has a distorted octahedral co-ordination with a η 5 -C 5 Me 5 group occupying the centre of three octahedral sites, two chloride atoms and a sulphur of a monodentate bis(phenylthio)methane ligand.

[Cp*Fe-dicyclopenta(a,f)naphthalene-FeCp*]n+ (Cp*=pentamethylciclopentadiene, n=0, 1), respectively named complexes V and VI, were synthesized and characterized. The X-ray structure has been solved and 1H-, 13C-NMR and elemental analysis were performed for the n=0 complex. Cyclic voltammetry showed a potential difference of 360 mV within the two redox peaks. An absorption band at 850 nm was assigned to an intervalence band. The Mossbauer investigations show a uniform Fe2+ environment for the neutral compound and two sites, assigned to Fe2+ and Fe3+ for the monoxidized compound. The information gathered by all the previously mentioned techniques indicates that the studied binuclear compound belongs to the mixed valence class II using Robin and Day classification.

The synthesis and properties of cationic complexes of general formula [(η6-MeC6H4Pri)RuCl{η2-EPPh2)2CHR-E,E′})]BF4 (RH, ES (1), Se (2); RMe, ES (5)) are described. The methylene proton of the coordinated dichalcogenide ligand reacts with strong bases such as KOH in methanol or TIPz in dichloromethane solutions, to give new cationic complexes in which the anionic ligand is acting as tridentate chelate with a C,E,E′-donor set. [(η6-MeC6H4Pri)Ru{η3-(EPPh2)2CR-C,E,E′ })]A (RH, A BF4−, ES (3), Se (4); RMe, APF6−, ES (6)). The complexes have been characterised by elemental analyses, molar conductivities and IR and NMR spectroscopy. The structure of the title complex was established by X-ray crystallography. The crystals are tetragonal; at 293°Ca = 15.120(2), c = 16.090(3)A, space group P43, Z = 4. The complex contains a tridentate C,S,S′-bonded ligand occupying three coordination positions of a distorted octahedral ruthenium centre, with an η6-MeC6H4Pri group completing the coordination sphere. Cyclic voltammetry shows that under argon the acidic protons of the coordinated neutral disulfide ligands (1.5) are reduced to hydrogen yielding the complexes with the anionic ligand coordinated in their tridentate form (3,6). These compounds are irreversible reduced in one-electron process to give Ru(1) species, followed by chemical decomposition.

Reaction of the complex [{(η5-C5Me5)RhCl2}2], in CH2Cl2 solution, with AgBF4 (1:2 molar ratio) and (SPPh2)3CH leads to the cationic compound [(η5-C5Me5)RhCl{η2-(SPPh2)2CH(SPPh2)-S,S′}]BF4 (1) which is deprotonated by thallium(I) pyrazolate affording [(η5-C5Me5)Rh{η3-(SPPh2)3C−S,S′,S″}]BF4 (2a). The iridium dimer [(η5-C5Me5)IrCl2}2] reacts with silver salts and (SPPh2)3CH, in CH2Cl2 or Me2CO, under analogous conditions, affording mixtures of [(η5-C5Me5)IrCl{η2-(SPPh2)2)-S,S′}]+ and [(η5-C5Me5)Ir{η3-(SPPh2)3C-S,S′,S″}]A [A=BF4− (3a), PF6− (3b). Addition of Et3N to the mixture gives pure complexes 3. The ruthenium complexes [{η6j6-arene)RuCl2}2] (arene = C6Me6, p-MeC6H4Pri) react with (SPPh2)3CH, in the presence of AgA (A = PF6− or BF4−) or Na BPh4, in CH2Cl2 or Me2CO, yielding only the deprotonated complexes [(η6-arene)Ru{η3-(SPPH2)3C−S,S′,S″}]A [arene = C6Me6, A = BF4; arene = p-MeC6H4Pri, A - BPh4 (4a), PF6 (4b)]. The crystal structures of 3a and 4a were established by X-ray crystallography. Compound 3a crystallizes in the orthorhombic space group Pna21, with lattice parameters a-41.477(6), b = 10.6778(11), c = 20.162(3) Å and Z=8. Complex 4a crystallizes in a monoclinic lattice, space group P21/n, with a = 20.810(4), b = 12.555(3), c = 23.008(4) Å, β = 95.82(2)° and Z = 4. Both cationic complexes exhibit analogous pseudo-octahedml molecular structures with the anionic (SPPh2)3C− ligand bonded via the three sulphur atoms in a tripodal, tridentate fashion. Each metal centre completes its coordination environment with a η5-C5Me5 (3a) or a η6-MeC6H4Pri group (4a). A quite interesting result concerns the non-planarity of the methanide carbon which display P−C−P angles in the range 112.6–114.4(5)° in 3a and 111.9–113.6(4)° in 4a. The redox chemistry of the complexes was investigated by cyclic voltammetry. The Rh(III) complexes are quasi-reversibly reduced to Rh(I) and the Ir(III) complex is irreversibly reduced to IKD in acetonitrile solutions. The Ru(II) complex undergoes a quasi-reversible reduction to Ru(I) and a reversible oxidation to Ru(III)., We thank the 'Fondo de Desarrollo Cientifico y Tecnologico, Chile' (Grant No. 460/93-95), Direccion de Investigacion y Postgrado, Pontificia Universidad Catolica de Chile (DlPUC), Fundacion Andes, Chile, and the Instituto de Cooperacion Iberoamericano, Spain, for financial support.