Scielo RSS <![CDATA[Journal of the Brazilian Chemical Society]]> vol. 26 num. 10 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Understanding Ozone Concentrations During Weekdays and Weekends in the Urban Area of the City of Rio de Janeiro]]> In different cities around the world, higher ozone concentrations are observed during weekends for various reasons. This study aims to determine the causes of this effect in the city of Rio de Janeiro based on measurements obtained at three automatic air quality monitoring stations in the Bangu, Campo Grande and Irajá neighborhoods between 2012 and 2013. Variations in the solar radiation and hourly carbon monoxide, nitrogen oxides, non-methane hydrocarbons, ozone and particulate matter concentrations were determined. The Bangu station showed the lowest ozone concentration differences between the weekdays and weekends (8.9%) and recorded the highest ozone concentrations and largest number of exceedances. The low ozone consumption by nitrogen oxide resulted in the high ozone concentrations at the Bangu station. In addition, the volatile organic compounds (VOC)/nitrogen oxides (NOx) ratio for this station was evaluated for each day of the week between 6 and 9 AM, and the observed VOC/NOx ratios were higher at the Campo Grande and Irajá stations. We concluded that the weekend effect occurred at all three of the evaluated stations, with greater intensity at the Campo Grande and Irajá stations. The main cause of this weekend effect is the greater reductions in NO emissions over the weekends, which increase the VOC/NOx ratio. <![CDATA[Cytotoxic Alkaloids from Hippeastrum solandriflorum Lindl.]]> One new alkaloid, 2α-10bα-dihydroxy-9-O-demethylhomolycorine, in addition to seven others known alkaloids, and 5-(hydroxymethyl)furfural, piscidic acid and eucomic acid, were isolated from the bulbs of Hippeastrum solandriflorum. The structures of all compounds were determined using nuclear magnetic resonance (NMR) spectroscopic techniques: 1H NMR and 13C NMR, heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC), nuclear Overhauser effect spectroscopy (NOESY), and also the high-resolution electrospray ionization mass spectrometry (EI-HRMS). The cytotoxic activity of all alkaloids was evaluated against three human cancer cell lines (HCT-116, HL-60, OVCAR8 and SF-295) showing IC50 values ranging from 0.01 to 35.7 µM. <![CDATA[Determination of Essential, Non-Essential, and Potentially Toxic Elements in Graviola (<em>Annona muricata</em> L.) Pulp by ICP OES and GF AAS]]> The determination of essential (B, Ca, Co, Cu, Cr, Fe, K, Li, Mg, Mn, P, S, Se, Si, V, and Zn), non-essential (Al, Ba, Sn, Sr, and Ti), and potentially toxic (As, Cd, and Pb) elements in graviola pulp by inductively coupled plasma optical emission spectrometry (ICP OES) and graphite furnace atomic absorption spectrometry (GF AAS) is proposed. Samples were digested in a closed-vessel microwave oven. The accuracy of the proposed method was checked by citrus leaves standard reference analysis. Limits of quantification (LOQ) were in the range of 0.039 mg g-1 (Ti) to 22 mg g-1 (K) for ICP OES and 0.011 mg g-1 (Cd) to 0.62 mg g-1 (Se) for GF AAS. According to the recommended dietary reference intake (DRI), graviola pulp can be considered a good source of B, Cu, K, Mg, and Mn. For all analysed samples the concentrations of As, Cd, and Pb were below the LOQ. <![CDATA[Determination of Cd, Ni and V in Spices by Solid Sampling High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry]]> This work describes a procedure for determination of Cd, Ni and V in spices by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) using direct solid sampling (SS). The use of Pd/Mg(NO3)2 as modifier for Cd, and an additional air-assisted pyrolysis step allowed the use of aqueous calibration for all analytes. Accuracy was checked by analysis of certified reference materials (CRMs) and the results were in agreement to certified values at 95% confidence level (t-test). Eight samples of spices were analyzed by the proposed procedure and by inductively coupled plasma mass spectrometry (ICP-MS). The found concentrations were 88-233 ng g-1 Cd , 113-2842 ng g-1 Ni and 154-1007 ng g-1 V, with precision generally better than 12%. Results obtained by the proposed procedure were in agreement with those obtained by microwave-assisted digestion and ICP-MS determination. The limits of detection were 0.2, 18 and 7 ng g-1 for Cd, Ni and V, respectively. <![CDATA[Effects of Types of Washing and Peeling in Relation to Pesticide Residues in Tomatoes]]> Tomatoes are widely consumed and most often without cooking, therefore it is important to estimate the reduction of residues using simple washing procedures. An experiment was carried out to evaluate the effects of household processing such as: washing with water, washing with 10% of vinegar solution and washing with 10% of sodium bicarbonate solution on pesticide residue levels of acetamiprid, azoxystrobin, diflubenzuron, dimethoate, fipronil, imidacloprid, procymidone and thiamethoxam, in spiked tomato samples. The amount of residue remaining in the peel and pulp was also investigated. The pesticide residues were monitored using the quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction and analysed by liquid chromatography tandem mass spectrometry method (LC-MS/MS) in dynamic multiple-reaction monitoring mode (DMRM). The effect of the number of washing treatments (n = 3) and control, with six replicates, differed significantly for all pesticides evaluated (n = 8), but despite washing, fipronil residues were not removed from the tomato samples. Overall, washing with water or other solutions, and peeling before consumption are shown to reduce pesticide residues in tomatoes. <![CDATA[Preparation of a Nitrite Electrochemical Sensor Based on Polyaniline/ Graphene‑Ferrocenecarboxylic Acid Composite Film Modified Glass Carbon Electrode and its Analytical Application]]> A sensitive and stable electrochemical sensor based on polyaniline/graphene-ferrocenecarboxylic acid (PANI/GR-FCA) composite film modified glass carbon electrode for determination of nitrite was presented and its morphology and structure were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques were used to investigate the electrochemical behavior of the nitrite oxidation, which exhibited an enhanced voltammetric response at the modified electrode. In the optimal condition, the oxidation of nitrite in Britton-Robinson buffer solution (BR) of pH 4.0 had the higher peak current than the bare electrode. A linear calibration curve over the concentration range 0.4-300 µmol L-1 of nitrite were obtained with a linear regression equation I (µA) = 0.1589 + 0.0020C (µmol L-1) (R = 0.9991, n = 13) and the detection limit was down to 0.02 mmol L-1 (S/N = 3). The recoveries of all determinations ranged between 96-102%. At the same time, the modified electrode showed a good long-term stability and reproducibility for determination of nitrite, as well as high selectivity. <![CDATA[Methyl Salicylate: an Alternative Extraction Solvent for Dispersive-Liquid-Liquid Microextraction of Benzimidazole Fungicides in Water Samples Followed by High‑Performance Liquid Chromatographic Analysis]]> Methyl salicylate based dispersive liquid-liquid microextraction method of benzimidazole fungicides (i.e., carbendazim, thiabendazole and fluberidazole) in water samples and analysis by high performance liquid chromatography has been firstly developed. The target fungicides in aqueous sample were extracted under the selected conditions of 250 µL of methyl salicylate without disperser solvent and 1.0% (m/v) sodium acetate without pH adjustment. The preconcentration factor and extraction recovery were obtained in the range of 24-38 and 54-85%, respectively. Limits of detection ranged from 0.03 to 0.05 µg L–1, while limits of quantification were in the range of 0.20-0.50 µg L–1. Recoveries at three spiked concentration levels of 5, 10, and 50 µg L–1 were obtained in the range of 74.1-118.4%, with the relative standard deviation (RSD) below 11%. The developed method was simple, rapid, low cost, and reliable for trace determination of the studied fungicides. <![CDATA[Oxidative Stress Parameters, Related Trace Elements Levels and Proteomics in Soybean Seeds in Order to Get a Better Assessment of Their Quality]]> Antioxidant systems, Fe, Cu, Zn, Mn and Ni levels and proteomics in soybean seeds of different performance in field were assessed. These results were correlated with the in vitro tests required by regulatory organisms, and the actual behavior in field. Basal superoxide content, superoxide dismutase (SOD) activity (20-80 U mg-1 protein) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity (4.6-7.0 mg antioxidant per g dry seed) permitted to study the oxidative stress of seeds. Essential metal levels were in accordance to previous reports, with the exception of Zn that was higher in some batches of good in vitro quality, but poor performance in field. Proteomic profile showed no differences between batches. Two of the studied parameters (basal superoxide content and Zn level) contribute to a better assessment of the health state of the seeds and predict a possible poor performance in field. <![CDATA[Use of an Automatic System in the Preparation of Gas Mixtures for Multivariate Calibration: A Case Study Involving NIR Analysis of Natural Gas]]> This paper investigates the use of an automatic system for preparation of gas mixtures in a multivariate calibration problem involving near-infrared (NIR) spectrometric analysis of natural gas. The automatic system is used to prepare calibration mixtures according to a Brereton experimental design, in order to exploit a suitable range of gas concentrations and thus avoid extrapolations in the predictions. These mixtures were employed to build partial-least-squares models for NIR determination of methane, ethane and propane, which are the major components of natural gas. Prediction performance was evaluated by using a separate set of prepared mixtures and natural gas samples with composition analyzed by gas chromatography, as well as a group of certified mixtures. The resulting root-mean-square errors of prediction (RMSEP) values for methane, ethane and propane (3.0, 0.9 and 1.2% mol mol-1, respectively) were approximately 10 times smaller than the corresponding calibration ranges, with correlations of 0.91, 0.96 and 0.86 between the predicted and reference values. <![CDATA[Development of a Selective and Sensitive Sensor for Urate Determination Based on Tris(1,10-phenantroline)copper(II) Bis(tetracyanoquinodimethanide) Adsorbed on Carbon Nanotubes]]> The present work describes the development of a selective electrochemical sensor for urate based on tris(1,10-phenantroline)copper(II) bis(tetracyanoquinodimethanide) (Cu(phen)3(TCNQ)2) adsorbed on multi-walled carbon nanotubes (CNT). The composite material was characterized by infrared spectroscopy, scanning electron microscopy, and electrochemical impedance spectroscopy. The composite material showed an excellent electrocatalytic activity toward oxidation of urate. The heterogeneous charge transfer rate constant (k’) between the analyte and the sensor was determined using linear sweep voltammetry experiments. The composite material shows a linear range from 5 up to 2500 µmol L-1 with limit of detection of 1.05 µmol L-1 and limit of quantification of 3.50 µmol L-1. The high sensitivity and selectivity of the sensor for urate was sufficient for its determination in biological fluids. Finally, the proposed sensor was successfully applied in urine samples. <![CDATA[Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop with Central Composite Design for the Determination of Nitrophenols Using High-Performance Liquid Chromatography]]> A simple and practical pre-concentration method, dispersive liquid-liquid microextraction based on solidification of a floating organic drop (DLLME-SFO) technique, was proposed for the determination of 4-nitrophenol and 2-nitrophenol in water samples. The effective experimental parameters on the extraction efficiency such as extraction solvent volume, dispersive solvent volume, and pH were studied using the response surface methodology. Under the optimum experimental conditions, the pre-concentration factors of 116 and 100 for 2-nitrophenol and 4-nitrophenol were obtained, respectively. The calibration curves were linear in the range of 5-150 µg L−1 with the detection limit of 1.70 µg L−1. The proposed method was successfully applied to the determination of nitrophenols in water samples. <![CDATA[Chemical Characterization and Optimization of the Extraction Process of Bioactive Compounds from Propolis Produced by Selected Bees <em>Apis mellifera</em>]]> The extraction process of bioactive compounds from propolis produced by selected bees was optimized using a 2³ factorial design planning to evaluate the effect of ethanol concentration, time and temperature on the extraction of total phenolic compounds and antioxidant activity. Analysis of total flavonoids, antioxidant activity and chemical characterization performed by high-performance liquid chromatography with photodiode array (HPLC-PDA) detection were carried out in optimal conditions of extraction. Optimizing results suggest that the best condition for extraction of bioactive compounds was obtained in higher levels: time (45 min), temperature (70 °C) and concentration of ethanol (80%). The extract evaluated in optimal conditions presented good antioxidant activity by the radical scavenging 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and ferric reducing antioxidant power (FRAP) methods and chromatographic analysis identified phenolic acids: para-coumaric, ferulic and caffeic, indicating that this material is a potential source of bioactive compounds. <![CDATA[Sequential Injection Analysis with Square Wave Voltammetry (SI-SWV) Detection for Investigation of Adsorption of Picloram on a Clay Soil]]> This paper describes a sequential injection analysis method, with detection by square wave voltammetry using a hanging mercury drop electrode, to determine the herbicide picloram in soil extracts (0.010 mol L-1 CaCl2). The method was applied for determination of the Freundlich parameters related to adsorption of picloram on a tropical soil sample. The major advantage of the proposed method over the conventional chromatographic methods is the high sampling throughput of 190 analyses per hour, with detection and quantification limits of 0.036 and 0.12 mg L-1, respectively. The Kf (0.0016 ± 0.0005 µmol1-1/n L1/n kg-1) and 1/n (0.85 ± 0.06) obtained by the proposed method did not differ from those determined by liquid chromatography with UV detection. <![CDATA[Biomimetic Sensor for Detection of Hydrochlorothiazide Employing Amperometric Detection and Chemometrics for Application in Doping in Sports]]> This work describes a simple and cost-effective method for quantitative determination of hydrochlorothiazide using biomimetic sensor based on a carbon paste modified with hemin (biomimetic catalyst of the P450 enzyme). The sensor was evaluated using cyclic voltammetry and amperometry for its electrochemical characterization and quantification, respectively. Amperometric analyses were carried out at 800 mV vs. Ag/AgCl (KClsat), using a 0.1 mol L−1 phosphate buffer solution at pH 8.5 as the support electrolyte. Optimization of the experimental parameters was performed using a multivariate methodology. The proposed method was successfully applied to the analysis of hydrochlorothiazide in spiked urine and pharmaceutical formulations, demonstrating that it is a reliable, feasible and efficient alternative method for the detection of hydrochlorothiazide in doping and can also be used for the quality control method. <![CDATA[Development of a Multiresidue Method for Pesticide Analysis in Drinking Water by Solid Phase Extraction and Determination by Gas and Liquid Chromatography with Triple Quadrupole Tandem Mass Spectrometry]]> In this work, a method for multiclass determination of 70 pesticides residues with different properties in drinking water using solid phase extraction (SPE) with polymeric sorbent and determination by gas and liquid chromatography coupled to tandem mass spectrometry (GC-MS/MS and LC-MS/MS) was developed and validated. Different sample volumes, sorbents and elution solvents were evaluated. The best results were obtained using the sorbent Oasis® HLB, sample acidified at pH 2.5 and a mixture of dichloromethane/methanol as eluent. The limit of quantification (LOD) of the method was 0.02 µg L-1 for aldrin, dieldrin and chlordane and 0.5 µg L-1 for the other compounds. Satisfactory accuracy, with recoveries between 70 and 117.3%, and good precision, with relative standard deviation (RSD) values below 19.7% for most of the compounds, were achieved. The validated method was applied to real water samples and results indicated that the proposed method is suitable for the determination of pesticide residues in water samples. <![CDATA[Bioactive Cyanopeptides Produced by <em>Sphaerocavum brasiliense</em> Strains (Cyanobacteria)]]> The halogenated compounds aeruginosin and cyanopeptolin (protease inhibitors) are well documented in several cyanobacteria. In this work, the presence of genetic coding for aeruginosin and cyanopeptolin in Sphaerocavum genus and their characterization by mass spectrometry and potential toxic effects were investigated. Three strains of Sphaerocavum brasiliense (CCIBt 3094, CCIBt 3096 and CCIBt 3316) isolated from different reservoirs in São Paulo State, and one (CCIBt 3179) from Rio Grande do Norte State were selected for this study. Fragments of aerA-aerB and mcnC-mcnE gene regions (aeruginosin and cyanopeptolin, respectively) were amplified by polymerase chain reaction (PCR) and sequenced. Compounds were characterized by mass spectrometry. All the studied strains presented aeruginosin and cyanopeptolin synthetase genes. Mass spectrometry showed the presence of several aeruginosin and cyanopeptolin variants. The Allium test showed that the ethanolic extract promoted toxic and cytotoxic actions in acute and chronic treatments. These naturally occurring protease inhibitors can play an important role in the physiopathology of human diseases. <![CDATA[Response Surface Methodology Applied in the Study of Emulsion Formulations in the Presence of Leaves of Rosemary (<em>Rosmarinus officinalis</em> L.) as a Source of Natural Antioxidants]]> The use of synthetic antioxidants in human consuming products is in disuse due to health toxic related issues. The search for substances to substitute synthetic antioxidants boosts studies concerned with the findings of sources of natural antioxidants. Thus, the aim of this work was to evaluate the use of comminuted leaves of rosemary (Rosmarinus officinalis L.) as source of natural antioxidants for the lipid protection of different emulsion compositions using central composite rotary experimental design. The Oxitest analysis (oxidation test reactor) revealed rosemary to be an excellent source of antioxidants for emulsions, even with addition of low quantities, and the gain of induction point tripled. The oxygen radical absorbance capacity (ORACFL) results of emulsion obtained separately for the hydrophilic and lipophilic phases showed that the presence of polar compounds was in higher concentration, about 500 more than of non-polar ones. The polar compounds are major responsible for the antioxidant action in the system. <![CDATA[Efficient Eco-Friendly Solvent-Free Click Synthesis and Antimicrobial Evaluation of New Fluorinated 1,2,3-Triazoles and their Conversion into Schiff Bases]]> A facile and convenient green click synthesis has been developed for the preparation of new fluorinated 1,2,3-triazoles under solvent-free conditions via a Huisgen 1,3-dipolar cycloaddition reaction between dimethylacetylene dicarboxylate (DMADC) and fluorophenyl azides in excellent yields within 2 min. Treatment of the resulting diesters with hydrazine hydrate furnished the corresponding dihydrazides, which, upon condensation with benzaldehyde derivatives, afforded a new series of bis-hydrazones. All of the synthesized compounds were fully characterized using infrared (IR) spectroscopy, 1H, 13C and 19F nuclear magnetic resonance (NMR), mass spectrometry (MS) and elemental analysis. A preliminary bioassay indicated that some of the tested compounds exhibited significant antimicrobial activity. <![CDATA[Total Mercury Determination in Petroleum Green Coke and Oily Sludge Samples by Cold Vapor Atomic Fluorescence Spectrometry]]> A fast, simple and reliable method for Hg determination in green coke and oily sludge samples by atomic fluorescence spectrometry is described. Microwave digestion and extraction procedures were evaluated for highly complex samples of coke and oily sludge. The concentrations of SnCl2 and HCl to promote Hg vapor, were optimized, as well as the concentration of KMnO4, to stabilize the Hg2+ before the atomic vapor formation. Accuracy of the method was evaluated through certified reference material, for green coke, and comparison with cold vapor atomic absorption spectrometry (CV AAS), for oily sludge. Recovery tests were also performed. Limits of detection and quantification were 0.8 and 2.6 µg kg−1, respectively. Ten green coke and nine sludge samples were analysed and Hg concentrations in coke are very low, between 0.005 and 0.065 mg kg−1, but oily sludge samples have high concentrations, ranging from 42.5 to 376.6 mg kg−1, requiring careful management. <![CDATA[Transport Properties of Binary Solutions Containing the Ionic Liquid BMI.BF4 and Ethylene Glycol]]> The ionic conductivity values of the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) and ethylene glycol (EG) electrolytes in different concentrations and over a wide temperature range were determined. The results are discussed in terms of the interactions between the cations and anions of the ionic liquid and the organic solvent. The temperaturedependence of the ionic conductivity for BMI.BF4, as well as solutions containing BMI.BF4 and EG as electrolytes, in the temperature range of 248-358 K, obeys the Vogel-Tammann-Fulcher equation. The highest ionic conductivity was 42 mS cm-1 obtained with a solution of BMI.BF4 in EG at a molar fraction of 0.50 (358 K) due to the high ionic mobility. The critical micellar concentration (cmc) of 0.1 mol L-1 determined through the ionic conductivity indicates that BMI.BF4 behaves as a weak electrolyte above this value. The results obtained indicate that binary solutions based on BMI.BF4 and EG are appropriate for use in technological applications, such as capacitors. <![CDATA[Use of Biodiesel Press Cake Waste to Prepare Fe/Carbon Reactive Composites for Environmental Applications: Removal of Hazardous CrVI Contaminants]]> In this work, Ricinus communis L. press cake waste from biodiesel production was used to produce a versatile reactive material for environmental applications. The biodiesel cake waste was impregnated with FeIII at different concentrations (19-45 wt.%) and treated at 400, 600 and 800 °C. Mössbauer, X-ray diffraction (XRD), thermogravimetric analysis (TG/DTA), scanning electron microscope (SEM), elemental analysis CHN, Raman, potentiometric titration, saturation magnetization and Brunauer-Emmett-Teller (BET) analyses showed that the materials prepared at 400 °C are composed mainly of a graphitic and amorphous carbon containing dispersed magnetite (Fe3O4). At higher temperatures, metallic iron (Fe0) and iron carbide (Fe3C) are the predominant phases well dispersed in the carbon porous structure. These reduced iron species, Fe3O4 and Fe0, are active for the reduction of different hazardous contaminants. Preliminary experiments showed very high activities for the reduction and removal of aqueous CrVI. <![CDATA[Rapid Determination of Lead in Progressive Hair Dye Lotion by Spot Test/Diffuse Reflectance Spectroscopy with a Paper Platform]]> A simple, inexpensive, and clean methodology employing a combined spot test/diffuse reflectance spectroscopy procedure was developed and applied for the quality control analysis of lead in hair dyes, using a filter paper platform. The method is based on the complexation reaction of lead, present in a pH 2.8 buffer medium containing tartaric acid and sodium and potassium tartrate, with sodium rhodizonate (ROD) in an aqueous medium containing sodium dodecyl sulfate (SDS) surfactant, yielding a colored compound on the surface of a filter paper. The concentrations of ROD and SDS were optimized using experimental design. The linear range obtained for reflectometric measurements carried out at 545 nm was 4.70-140 mg L-1 of lead (R = 0.998), and the limits of detection and quantification were 1.12 and 3.75 mg L-1, respectively. The proposed method was successfully applied to the analysis of lead in progressive hair dyes. <![CDATA[Chemical Speciation of Iron in Different Varieties of Beans (<em>Phaseolus vulgaris</em> L.): Cooking Effects]]> Beans are considered a source of iron (Fe), and hence have considerable contribution in cases of Fe deficiency. Beans also contain certain anti-nutritional constituents, which are imperative to the cooking of beans. The nutritional value of beans depends on the bioavailability, which can be affected by cooking. Studies about heating effects in distribution of Fe-based inorganic species are limited, especially for bean cultivars commonly consumed in Brazil. The aim of this work was to evaluate the effects of domestic cooking on the distribution of Fe species (water soluble and inorganic) in seven varieties of Phaseolus beans. Fractionation procedures were used to separate Fe associated to various species. The Fe content was quantified by graphite furnace atomic absorption spectrometry (GF AAS). In raw beans, the inorganic Fe species significantly contributes to the water soluble fraction obtained after fractionation. Cooking lowered the concentration of water soluble Fe in majority varieties of beans. <![CDATA[Application of Bar Adsorptive Microextraction-Large-Volume Injection-Gas Chromatography-Mass Spectrometric Method for the Determination of Trace Levels of Agrochemicals in Real Matrices]]> Bar adsorptive microextraction followed by liquid desorption in combination with large volume injection gas chromatography coupled to mass spectrometry, under selected ion monitoring mode acquisition (BAµE-LD/LVI-GC-MS(SIM)), was applied for the determination of trace levels of different classes of agrochemicals (using alachlor, diniconazole, fenpropathrin, as well as cis and trans-permethrin as model compounds) in environmental water and wine matrices. Assays performed on 25 mL of ultra-pure water samples spiked at the 2.0 µg L-1 level, yielded recoveries ranging from 55.2 to 105.6%, under optimized experimental conditions. The analytical performance showed convenient detection limits (8.0 to 32.0 ng L-1) and good linear dynamic ranges (0.03 to 4.00 µg L-1), with remarkable determination coefficients (r2 &gt; 0.9982). Excellent repeatability, based in relative standard deviation (RSD) was also achieved through intraday (RSD &lt; 7.5%) and interday (RSD &lt; 7.0%) assays. Studies performed on surface and ground water, as well as wine samples, using the standard addition method, revealed good sensitivity at the trace level. <![CDATA[Square-Wave Voltammetric Determination of Paracetamol and Codeine in Pharmaceutical and Human Body Fluid Samples Using a Cathodically Pretreated Boron-Doped Diamond Electrode]]> Simple, fast, and inexpensive electroanalytical procedures were developed for the determination of codeine (COD) solely and paracetamol (PCT) and COD simultaneously in pharmaceutical formulations and human body fluids. The methods involve the combination of square-wave voltammetry (SWV) with a cathodically pretreated boron-doped diamond electrode and a 0.2 mol L–1 acetate buffer (pH 4.0) solution as the supporting electrolyte. Significantly low limits of detection were obtained for COD solely or PCT and COD simultaneously: 1.19 or 18 and 14 nmol L–1, respectively. The proposed SWV method was successfully applied in the simultaneous determination of PCT and COD in four samples of pharmaceutical tablets, with results similar (at 98% confidence level) to those obtained using a reference high-performance liquid chromatography (HPLC) method. Additionally, adequate results were obtained when concentrations of PCT and COD were determined in human urine or serum samples by addition-recovery. Clearly, the proposed method is an excellent option for the determination of COD solely or PCT and COD simultaneously.