ABSTRACT Ibuprofen is one of the most widely used nonsteroidal anti-inflammatory drugs due to its analgesic, anti-inflammatory and antipyretic properties, as well as its low cost and easy accessibility. A fraction of the compound and its metabolites are excreted in the urine, being eliminated in the wastewater reaching river waters in the range of ng L-1 to μg L-1. In this context, highly sensitive and selective analytical methods are required to quantify them, including these methods a pre-concentration step. In this work, the use of a microextraction technology based on rotating-disk sorptive extraction, involving a sorptive phase of laminar cork, was implemented for the extraction of ibuprofen and 1-hydroxyibuprofen from aqueous samples and their subsequent determination by gas chromatography coupled to mass spectrometry. The optimal conditions for determination of the analytes were: 20 mL of sample volume, pH 2, 20 % w/v NaCl (to increase the ionic strength), 90 min of extraction time and 2000 rpm of rotation velocity of the disk. Recoveries of 118 and 39 % and relative standard deviations of 6 and 13 % for ibuprofen and 1-hydroxyibuprofen were obtained, respectively. The presence of both compounds in river waters (Mapocho river, Santiago of Chile) at a concentration of 2.56 to 4.08 μg L-1 were found. The use of laminar cork as a natural sorbent phase immobilized in the rotating-disk allowed to extract the analytes from water samples through its lipophilic-hydrophilic balance that favors the interaction with the compounds under study.

ABSTRACT A derivative spectrofluorimetric method for simultaneous determination of enrofloxacin (EFX) and ciprofloxacin (CFX) in cow milk was developed. The sample preparation was based on rotating disk sorptive extraction (RDSE) using Oasis HLB® as extraction phase and followed by desorption of the analytes with methanol. The final extracts were evaluated by derivative spectrofluorimetry. An analyte-free cow milk was used as blank sample which was spiked with a known amount of analytes for the study of variables. The sample was treated with trichloroacetic acid in order to precipitate proteins. Furthermore, the extraction was carried out in the presence of Mc Ilvaine-EDTA 0.3M buffer to avoid any type of interference from the calcium ion. The variables involved in the RDSE process were pH and extraction time. Spectral variables were also optimized and analytical signals were evaluated at 417nm and 438nm for EFX and CFX, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were 2.98 – 9.04 μg · L−1 and 2.56 – 7.75 μg · L−1, for EFX and CFX respectively. The precision levels, expressed as relative standard deviation, for EFX and CFX were 3.2% and 3.0%, respectively. The recoveries were between 98.8% to 100.5%. Commercial milks were analyzed and both antibiotics shown concentrations below to LOD in the batches analyzed. Finally, the proposed method offers advantages in terms of simplicity, efficiency and cost. Besides being friendly with the environment.

ABSTRACT The total elemental composition and the water-soluble fraction of PM10 from three different urban areas in Santiago, Chile, from downtown to the suburbs, were investigated. PM10 samples collected during the month of May (mid-autumn in the Southern Hemisphere) in 2006, 2008, 2009, and 2010 were analyzed for major and trace metals, and the partitioning between the insoluble and soluble fractions was determined for most of them. PM10 average concentrations ranged from 71 µg m-3 (Cerrillos) to 128 µg m-3 (La Pintana), which are within the seasonal ranges observed in Santiago. Twenty five major and trace elements (Fe, Al, Ca, K, Mg, P, Pb, S, Ti, Mn, Cu, Zn, Ba, Zr, Cr, As, Sn, Sb, Ni, V, Li, Co, Cd, La, and Rb) were determined in the present study. Ba, Sb, Cd, As, and Zn, with proportions in the soluble fraction varying from 50% to 98%, were the most soluble elements. On the contrary, the less soluble trace elements were Ti, Sn, Pb, and Cr. Most of the high-solubility trace metals are strongly linked to non-exhaust traffic emissions, as well as to certain industrial sources. Our results evidence the significant amount of soluble trace elements in Santiago’s urban atmosphere classified as toxic and/or carcinogenic, thus suggesting a non-negligible health impact.

RESUMEN Se investigó la composición elemental total y la fracción soluble en agua de PM10 en tres áreas urbanas diferentes de Santiago de Chile, del centro a los suburbios. Las muestras de PM10 recogidas durante el mes de mayo (mediados del otoño en el hemisferio sur) en 2006, 2008, 2009 y 2010 fueron analizadas para metales mayores y trazas, y la partición entre fracciones insolubles y solubles se determinó para la mayoría de ellos. Las concentraciones medias de PM10 variaron de 71 µg m-3 (Cerrillos) a 128 µg m-3 (La Pintana), valores que se encuentran dentro de los rangos estacionales observados en Santiago. Se cuantificaron 25 elementos principales y trazas (Fe, Al, Ca, K, Mg, P, Pb, S, Ti, Mn, Cu, Zn, Ba, Zr, Cr, As, Sn, Sb, Ni, V, Li Co, Cd, La y Rb) en el presente estudio. Ba, Sb, Cd, As y Zn fueron los elementos más solubles, con proporciones que varían de 50% a 98% de solubilidad. Por el contrario, los oligoelementos menos solubles fueron Ti, Sn, Pb y Cr. La mayor parte de los metales traza de alta solubilidad no están solamente fuertemente ligados a la emisión de tubos de escape vehiculares, sino a emisiones vehiculares como el sistema de frenos o a ciertas fuentes industriales. Nuestros resultados evidencian la cantidad significativa de oligoelementos solubles en la atmósfera urbana de Santiago clasificados como tóxicos y/o carcinógenos, lo que sugiere un impacto no despreciable en la salud.

In this study, a new method for determination of triclabendazole (TCB) as its main metabolites, triclabendazole sulfoxide (TCB-SO) and triclabendazole sulfone (TCB-SO2) in animal plasma was developed. TCB is widely used as antiparasitic in the veterinary industry. Rotating disk sorptive extraction (RDSE) was the selected sample preparation technique for extraction/clean up of the compounds from the samples followed by high performance liquid chromatography coupled to diode array detection (HPLC-DAD) for quantification. Optimization of physicochemical variables was performed using a multivariate experimental design. Following the recommendations given in the Veterinary International Conference on Harmonization guides (VICH GL02 and VICH GL49), the validation of the method was performed, given rise to improved analytical features compared with those provided by other methods based on solid phase extraction (SPE). Linearity (r > 0.99) was achieved for both compounds when calibration was performed not only in standard solutions but also in animal spiked plasma. Selectivity, defined as the response ratio between blank and analyte at the limit of quantification, was 11.8% and 3.4% for TCB-SO and TCB-SO2, respectively. Accuracy and precision, expressed in percentage, were always lower than -16.7% and 8.1%, respectively. Eco-efficiency was quantitatively assessed indicating that the method is an excellent green method. The proposed analytical method was applied to the determination of the pharmacokinetic of two commercial products of TCB in cattle plasma after oral administration. The good analytical performance, eco-efficiency and economy, make the method interesting for alternative use in routine laboratories.

The rotating disk sorptive extraction (RDSE) technique was applied in this study to the extraction of 16 polycyclic aromatic hydrocarbons (PAHs) in real water samples. The sorptive and desorptive behavior of the analytes were studied by using a rotating disk coated with polydimethylsiloxane (PDMS) on one of its surfaces. The optimal conditions for extractions of all analytes were: rotational velocity of the disk: 1250 rpm; sample volume: 20 mL; matrix modifier: 20 % MeOH and extraction time: 30 min. A desorption time of 10 min at 1250 rpm was used for the analytes using 5 mL of methanol. PAHs were measured in the extract by gas chromatography coupled to mass spectrometry (GC-MS). Under these conditions, recoveries ranging from 84 to 100 % were obtained in drinking water enriched with the analytes, and the precision, expressed as relative standard deviation, was between 2 and 20%. The detection limit of the method was between 8 and 115 ng L-1 depending on the analyte. The method was applied to the analysis of water samples obtained from a lagoon in Curauma, Chile, obtaining quantitative recoveries.

Um método rápido e eficiente, baseado na integração da extração com solvente sob pressão (PSE) com limpeza através do método sólido de extração (SPE) e sistema de cromatografia gasosa com detector por captura de elétrons (GC-ECD) foi desenvolvido para a determinação de bifenilos policlorados (PCBs). Seis indicadores e doze PCBs semelhantes à dioxina foram selecionados como analitos. Este método baseia-se na integração da extração de solvente e de processos de limpeza no interior de uma célula pressurizada de aço inoxidável. As condições de extração otimizadas foram 6 min de extração, a 70 °C e dois ciclos de extração utilizando hexano/cloreto de metileno (1:1, v/v) como solvente de extração. Sílica gel acidificada com ácido sulfúrico foi utilizada para a limpeza integrada do extrato orgânico. Este método permite uma redução significativa no tempo de processo e o consumo de solvente. Repetibilidade, expressa como o desvio padrão relativo, variou de 3 a 6%, e a recuperação para a concentração de 20 ng g-1 variou entre 71 a 104%. O limite de detecção e quantificação variaram de 0,03 a 0,29 ng g-1 e 0,1 a 0,97 ng g-1, respectivamente. A variação linear foi entre 5 e 100 ng g-1. Finalmente, este novo método foi aplicado em amostras de carne de frango e de porco.

A rapid and efficient method based on the integration of pressurized solvent extraction (PSE) with solid phase extraction (SPE) cleanup and gas chromatography system with electron capture detection (GC-ECD) has been developed for determination of polychlorinated biphenyls (PCBs). Six indicators and twelve dioxin-like PCBs were selected as analytes. This method is based on the integration of solvent extraction and cleanup processes inside a pressurized stainless steel cell. The optimum extraction conditions were 6 min of extraction at 70 °C and two cycles of extraction using hexane/methylene chloride (1:1, v/v) as the extraction solvent. Silica gel acidified with sulfuric acid was used for integrated cleanup of the organic extract. This method allows a significant reduction in extraction time and solvent consumption. Repeatability, expressed as the relative standard deviation, ranged from 3 to 6%, and recoveries for concentration of 20 ng g-1 was ranged between 71 to 104% .The limit of detection and quantification ranged from 0.03 to 0.29 ng g-1 and 0.1 to 0.97 ng g-1 respectively. The linear range was between 5 and 100 ng g-1 . Finally this new method was applied to samples of chicken and pork.

Neste estudo, uma metodologia de extração em solvente pressurizado de alquilfenóis (APs) e alquilfenóis etoxilados (APEOs) a partir de biosólidos foi otimizada utilizando-se um biosólido contendo nativamente estes compostos em um nível de concentração elevada. A otimização da extração foi realizada através de um planejamento experimental de análise multivariada com um planejamento composto central (CCD) produzindo os seguintes valores otimizados: temperatura de 129 ºC, tempo de extração por ciclo de 34 min em dois ciclos e acetona como solvente de extração. Em comparação com a extração Soxhlet, esta metodologia acabou por ser mais eficiente para a extração de APEOs e de eficiência semelhante para a extração de APs. Por outro lado, a metodologia é consideravelmente mais rápida do que a de Soxhlet e usa uma pequena quantidade de solvente de extração. As concentrações de 204 ± 20 e 1053 ± 23 mg kg-1 de nonilfenol e nonilfenol-etoxilato, respectivamente, foram determinadas na amostras de biosólido.

In this study, a methodology for pressurized solvent extraction of alkylphenols (APs) and alkylphenol ethoxylates (APEOs) from biosolids was optimized by utilizing a biosolid natively containing these compounds at a high concentration level. Optimization of the extraction was carried out through a multivariate analysis experimental design with a central composite design (CCD) producing the following optimum values for the variables: temperature of 129 ºC, extraction time per cycle of 34 min in two cycles and acetone as extraction solvent. Upon comparison with Soxhlet extraction, this methodology turned out to be more efficient for the extraction of APEOs and of similar efficiency for APs. On the other hand, the methodology is considerably faster than Soxhlet and uses a smaller amount of extraction solvent. Concentrations of 204 ± 20 and 1053 ± 23 mg kg-1 for nonylphenol and nonylphenol-ethoxylate, respectively, were determined in the biosolid sample assayed.

Biosolid model samples (BMSs) were developed to study the capacity of various matrixes to adsorb polybrominated diphenyl ethers (PBDEs) as a function of their composition. A commercial standard reference samples for biosolids containing a certified amount of PBDEs is currently not available for extraction evaluation. Therefore, this study will allow for the selection of an appropriate concentration of PBDEs to produce a reference material for analytes associated with the matrix. The sorption of PBDEs increased clearly concomitantly with the amount of organic matter present in the model, revealing that organic matter rather than the inorganic fraction is mainly responsible for the analyte-matrix interaction. Hydrophobic interactions are predominant in the retention of PBDEs in the biosolid matrix because more hydrophobic congeners are generally sorbed to a higher extent than those that are less hydrophobic. In order to know the probable PBDE sorption mechanism on the model sample of biosolid, the Gibbs free energies were calculated using the Freundlich model, giving values between -8 and -10 kJ/mol. These results suggest that the sorption mechanism of the PBDEs is through physiosorption. Therefore, the Freundlich model should be satisfactory for describing the analyte behavior.

In this work, Ferrospectral;3-(2-pyridyl)-5,6-bis(4-phenylsulfonic acid)-1,2,4-triazine (FST) sorbed on DEAE Sephadex A-25 is used as solid phase for spectrophotometric determination of iron and cobalt by batch and continuos flow modes. In batch simultaneous determination, the second derivative at 536.0 and 601.4 nm were used for iron and cobalt determination, respectively. In this modality, the detection limits (3 o criterion), for iron and cobalt were 1.3, 9.1, ug L¹ and the determination ranges were: 4.3 to 220 and 30.3 to 800 ug L¹. The method by FIA mode was carried out by stopped flow and then the analytical signal was evaluated by second derivative at 560.9 and 482.3 nm for iron and cobalt determination; respectively. In FIA modality, the detection limits for iron and cobalt were 6.4, 31 ug L¹, and the determination ranges 21 to 200 and 106 to 1000 ug L¹ iron and cobalt, respectively. In both modalities the repeatability for iron and cobalt were < 4 % and the recovery was near to 100%. These methods were applied successfully in drinking water and soil samples.

O efeito da aplicação de biossólido na distribuição e extração de Cr, Cu, Ni, Pb e Zn foi avaliado em solos Molisol de uma importante zona destinada à agricultura no Chile central. Massas de 15 e 30 Mg ha-1 de biossólidos foram adicionadas aos solos e os mesmos foram incubados por 60 dias sob condições controladas de umidade e temperatura. Quatro biossólidos domésticos foram obtidos em uma das plantas de tratamento de águas residuárias de Santiago. As extrações sequenciais a partir de amostras de biossólido e solo foram efetuadas de acordo com o procedimento recomendado pelo BCR, que se baseia em quatro extrações para obter uma fração solúvel em ácido (trocável, carbonatos), uma fração reduzível (óxidos de ferro/manganês), uma fração oxidável (matéria orgânica e sulfetos) e uma fração residual. Os metais traço foram determinados por espectrometria de absorção atômica com chama e espectrometria de massa acoplada ao plasma indutivo. Dentre os metais determinados em biossólidos, Zn apresentou a concentração mais alta. A quantidade de metais traço determinada em alguns biossólidos, exceto para Ni, foi abaixo dos limites permitidos pela legislação Chilena para biossólidos. Em geral, desconsiderando-se a fração residual, os metais foram encontrados predominantemente nas frações reduzíveis e oxidáveis. Um planejamento multifatorial foi empregado para avaliar os efeitos da quantidade de biossólido aplicada, do tipo de biossólido e do tempo de incubação. A incorporação do biossólido à razão de 30 Mg ha-1 produziu um aumento na disponibilidade de Zn e Ni em todos os solos e de Cu na maioria deles. Por outro lado, Cr e Pb não variaram significativamente. Em geral, os fatores incubação e tipo de biossólido não apresentaram efeitos pronunciados quando comparados com as condições iniciais.

The effect of biosolid application on the distribution and extractability of Cr, Cu, Ni, Pb, and Zn was assessed in Mollisol soils from an important agricultural zone in central Chile. These were amended with biosolids at the amounts of 15 and 30 Mg ha-1 and incubated for 60 days under controlled conditions of moisture and temperature. Four domestic biosolids were obtained from the monofill at one of the Santiago wastewater treatment plants. Biosolid and soil sequential extraction was performed according to the procedure recommended by BCR, which considers four extractions to obtain an acid-soluble fraction (exchangeable, carbonates), a reducible fraction (iron/manganese oxides), an oxidizable fraction (organic matter and sulfides) and the residual one. Trace metals were determined by flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry. Among the metals determined in biosolids, Zn had the highest concentration. Total trace metal contents found, except for Ni in some biosolids, was below the limits allowed by the Chilean regulation for biosolids. In general, without considering the residual fraction, the metals were found predominantly as reducible and oxidizable fractions. A multifactorial design was applied to assess the effects of biosolid application amounts, biosolid type and incubation time. Biosolid incorporation at the amount of 30 Mg ha-1 produced an increase in Zn and Ni availability in all soils and Cu in most of them, while Cr, and Pb showed no significant variations. In general, the factors incubation and type of biosolid did not show remarkable effects compared with initial conditions.

The concentration of trace elements and other analytes of environmental interest was determined in waters and sediments of the Coya and Cachapoal rivers (VI Region, Central Chile), which corresponds to a location highly polluted by copper mining activity. Analysis showed the highest pollution at the sampling station closest to the copper smelter (Caletones), then pollutant concentrations decrease at sites far away from this source. The statistical correlation between the different variables determined in waters and sediments was carried out through a principal components analysis (PCA). It was observed that the parameters fell into three groups: (a) analytes present in waters and sediments which come from the mining wastes (b) analytes of lithoge-nic character present in waters plus alkaline and alkaline earth metals plus organic matter present in sediments and waters, and (c) lithogenic elements present in sediments. On the other hand, by using cluster analysis (CA), it was possible to group the different sampling stations according to their extent of pollution

Um método simples e rápido foi desenvolvido para análise de bifenis policlorados (PBC) em transformadores a óleo. O método baseia-se na extração líquido-líquido em metanol e subseqüente determinação direta por cromatografia gasosa acoplada a espectrômetro de massa. A polaridade do metanol permite extrair PCBs, junto com uma quantidade mínima de componentes apolares do óleo, evitando assim etapas demoradas na preparação de amostras. Uma vez que o padrão estabelecido internacionalmente para resíduos contento PCBs é 50 mg kg-1, o método determina rapidamente se o transformador a óleo está contaminado com PCBs ou não. Para conseguir as melhores condições de extração, foi realizada uma otimização multivariada, considerando duas variáveis significativas: volume de metanol e tempo de extração. Sob condições ótimas, as recuperações de Aroclor 1256 e Aroclor 1260 estavam entre 80 e 100%, e a precisão, expressa como desvio padrão relativo, entre 2 e 4%. O método foi aplicado em amostras reais poluídas com PCBs.

A rapid and simple method was developed for screening polychlorinated biphenyls in transformer oil. The method is based on liquid-liquid extraction in methanol and subsequent direct gas chromatography-mass spectrometric determination. The extent of methanol polarity allows to extract the PCBs, co-extracting a minimum amount of the apolar oil components, thus avoiding the time-consuming steps involving in sample preparation. Since the regulation established internationally for wastes containing PCBs is 50 mg kg-1, the method rapidly determines whether the transformer oil is PCBs-contaminated or not. In order to reach the best conditions for extraction a multivariate optimization was carried out considering two significant variables: volume of methanol and extraction time. Under optimum conditions, recoveries of Aroclor 1256 and Aroclor 1260 were between 80 and 100%, and precision, expressed as relative standard deviation, was from 2 to 4%. The method was applied to real samples polluted with PCBs.

A direct and simple second derivative digital spectrophometric method has been developed for the simultaneous determination of the sulfamethoxazole and trimethoprim in pharmaceutical formulation. A study of the spectral behavior of these drugs in different solvents is included, in order to select the best conditions for their simultaneous determination. Acetonitrile was used as solvent to extract the drugs from the pharmaceutical formulations and then to evaluate directly by second derivative spectra. This sumultaneous determination was carried out by the zero crossing approach, at 272,8 nm for sulfamethoxazole determination and at 256,0 nm for trimethoprim determination. The determination range for sulfamethoxazole was from 6,31x10-8 to 1,20x10-4 mol/L and for trimethoprim from 2,47x10-7 to 1,20x10-4 mol/L, and the detection limits for sulfamethoxazole and trimethoprim were 1,89x10-8 mol/L and 7,40x10-8 mol/L, respectively. The method was applied successfully in pharmaceutical formulations (tablets). Besides a study of photo-stability of both drugs with standard solutions and real pharmaceutical formulations was performed

RESUMEN En este trabajo, se propone un método simple y directo para la determinación simultánea de sulfametoxazol y trimetoprim en formulaciones farmacéuticas por espectrofotometría derivada digital de segundo orden. Se incluye además, un estudio de la conducta espectral de estas drogas en diferentes solventes, con el objeto de seleccionar las condiciones óptimas para su determinación simultánea. Acetonitrilo fue utilizado como solvente para extraer las drogas desde las formulaciones farmacéuticas y luego evaluar directamente las segundas derivadas espectrales. Esta determinación simultánea fue realizada por la aproximación de "zero crossing" a 272,8 nm para la determinación de sulfametoxazol y a 256,0 nm para la determinación de trimetoprim. Se encontró un rango de determinación para sulfametoxazol desde 6,31x10-8 a 1,20x10-4 mol/L y para trimetoprim desde 2,47x10-7 a 1,20x10-4 mol/L siendo los límites de detección 1,89x10-8 mol/L para sulfametoxazol y 7,40x10-8 mol/L para trimetoprim. El método propuesto fue aplicado exitosamente en formulaciones farmacéuticas (tabletas). Además se realizó un estudio de la foto-estabilidad de ambas drogas con soluciones estándares y en formulaciones farmacéuticas reales

A microdetermination of iron at sub-mug/L level by derivative spectrophotometry has been developed. The compound TPTZ (2,4,6-tripyridyl-1,3,5-triazine) was used as chromogenic reagent to form a blue complex (pH = 5.0), which is fixed and concentrated on a cation-exchange resin sp sephadex C-25. The influence of experimental variables on the retention of the complex on sp sephadex C-25 is discussed. The signals in derivative units were measured directly on the resin, packed in a 1 mm spectrophotometric cell. The characteristic amplitude of the signal at 660 nm in second-derivative spectra is useful for quantitative determination of iron. (0,241-120 ng/mL; RDS < 2,7 %). The method was applied to the iron determination in different types of water

En este trabajo se propone un método por espectrofotometría derivada para la microdeterminación de hierro a niveles de sub-myg/L. El TPTZ (2,4,6-tripiridil-1,3,5-triazina) fue usado como reactivo cromóforo para formar a pH = 5,0 un complejo azul, el cual es retenido y concentrado sobre una resina sp sephadex C-25 de intercambio catiónico. Se incluye una discusión de las variables experimentales que influyen sobre la retención del complejo sobre sp sephadex C-25. Las señales en unidades derivativas fueron medidas directamente en una resina, empaquetada en una celda espectrofotométrica de paso de luz de 1 mm. En la segunda derivada de los espectros, la amplitud de la señal a 660 nm es característica del complejo Fe(II)-TPTZ retenido en la resina y es útil para la determinación cuantitativa de hierro ( 0,241-120 ng/mL; DER < 2,7 %). El método fue aplicado en la determinación de hierro en diferentes tipos de agua

In this work a method for determination of copper at low cncentration levels is proposed by using a continuous flow manifold in which the liquid-liquid extraction step for extracting the copper from the aqueous matrix is automated. The analyte is transferred into 1,2 dichloroethane as the colored complex Cu(I)-bathocuproine-counter ion. The manifold also contains a sandwich type membrane separator which is used after the extraction process. This phase separator provides the channel of the outlet organic stream free of aqueous phase, thus avoiding the interference with the transiently detection process at 478 nm. By keeping the chemical and hydrodynamic variables of the method in the optimal condition, it was found that copper can be determined from 64.5 ng/mL to 4000 ng/mL, with a detection limit of 19.3 ng/mL. The repeatability of the method for concentrations of 200 and 1000 ng/mL, expressed as variation coefficient, were of 3.77% and 1.08%, respectively. The sampling rate was 22 h-1. The accuracy of the method was tested by using the certified reference material for elements in waters GBW 08607. The relative error between the found and the certified value was + 2.9%.

En este tabajo se propone un método para determinar cobre a bajos niveles de concentración empleando una configuración de flujo continuo que permite la automatización de la etapa de extacción líquido-líquido, mediante la cual el cobre es extraído en un solvente orgánico como el complejo coloreado Cu(I)-baocuproina-contra ion. La configuración además contiene un separador de fases de membrana tipo "sandwich" que permite, posteriormente al proceso de extracción, dejar libre a la fase orgánica de fase acuosa y de esta forma llevar a cabo en transiente la lectura de absorbancia a 478 nm, sin interferencia de fase acuosa. Manteniendo cada una de las variables químicas e hidrodinámicas del método en su condición seleccionada, se encontró un rango lineal para la determinación de cobre desde 64,5 ng/mL hasta 4000 ng/mL, con un límite de detección de 19,3 ng/mL. La repetibilidad del método para concentraciones de 200 y 1000 ng/mL, expresada como coeficiente de variación, fue de 3,77% y 1,08%, respectivamente. La frecuencia de muestreo fue de 22 h-1. La exactitud del método fue evaluada utilizando el material de referencia certificado de elementos metálicos en aguas GBW 08607, obteniéndose un error relativo al valor certificado de + 2,9%