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Analytical and bioanalytical chemistry 413(12), 3253-3268 (2021). doi:10.1007/s00216-021-03261-3 special issue: "Acylation as derivatization strategy during an OPCW Proficiency Test/Comprehensive prognosis risk prediction of hepatocellular carcinoma/3D printed microdevice for smartphone-based on-site-capable uranium analysis/Intermolecular FRET sensor for tracking glycosylation of CD147 in living cells", Published by Springer, Berlin ; Heidelberg

In situ detection and quantification of reaction intermediates and products is of paramount importance in applied and fundamental research. In the present work, differential electrochemical mass spectrometry (DEMS) is coupled with flow injection analysis (FIA) to study the hydrogen evolution reaction (HER) on a carbon screen-printed electrode (SPE) modified with a carbon-supported platinum (Pt/C) catalyst. Using this approach, the gaseous and volatile species produced during an electrochemical reaction of interest can be detected and quantified. The reported results support the viability of the novel setup, which can be employed not only for the HER, but also for a vast diversity of electrochemical reactions occurring at various modified SPEs.

WOS: 000449439800013 A new and highly sensitive spectrophotometric based flow injection analysis method has been developed for the determination of copper (II). N, N'-o-phenylene-bis (3-methoxysalicylideneimine) (H2IF) was used as a new chromogenic reagent. The absorbance was measured at lambda(max) = 420 nm. Various factors affecting complex formation have been investigated. For example, the pH effect, reagent concentration was studied. Under optimum conditions, Beer's law was met in the range of 3.18-318 mu g L-1 copper (II) concentration. The system required no mixing chamber and allowed a sample throughput > 60 sample per hour for 20 mu L injection volume. The interaction of the various ions was investigated and the experimental results were reported. The proposed method has been successfully applied to the determination of the amount of copper (II) found in pharmaceutical samples and water samples. The validity and applicability of the method was confirmed by AAS and standard reference material SPS-WW2 (Wastewater) analysis.

There is a strong need for techniques that can quantify the important reactive oxygen species hydrogen peroxide (H2O2) in complex media and in vivo. We combined chemiluminescence-based H2O2 measurements on a commercially available flow injection analysis (FIA) system with sampling of the analyte using microdialysis probes (MDPs), typically used for measurements in tissue. This allows minimally invasive, quantitative measurements of extracellular H2O2 concentration and dynamics utilizing the chemiluminescent reaction of H2O2 with acridinium ester. By coupling MDPs to the FIA system, measurements are no longer limited to filtered, liquid samples with low viscosity, as sampling via a MDP is based on a dynamic exchange through a permeable membrane with a specific cut-off. This allows continuous monitoring of dynamic changes in H2O2 concentrations, alleviates potential pH effects on the measurements, and allows for flexible application in different media and systems. We give a detailed description of the novel experimental setup and its measuring characteristics along with examples of application in different media and organisms to highlight its broad applicability, but also to discuss current limitations and challenges. The combined FIA-MDP approach for H2O2 quantification was used in different biological systems ranging from marine biology, using the model organism Exaiptasia pallida (light stress induced H2O2 release up to ~ 2.7 µM), over biomedical applications quantifying enzyme dynamics (glucose oxidase in a glucose solution producing up to ~ 60 µM H2O2 and the subsequent addition of catalase to monitor the H2O2 degradation process) and the ability of bacteria to modify their direct environment by regulating H2O2 concentrations in their surrounding media. This was shown by the bacteria Pseudomonas aeruginosa degrading ~ 18 µM background H2O2 in LB-broth. We also discuss advantages and current limitations of the FIA-MDP system, including a discussion of potential cross-sensitivity and interfering chemical species.

The rate of carbon dioxide production is commonly used as a measure of microbial activity in the soil. The traditional method of CO2 determination involves trapping CO2 in an alkali solution and then determining CO2 concentration indirectly by titration of the remaining alkali in the solution. This method is still commonly employed in laboratories throughout the world due to its relative simplicity and the fact that it does not require expensive, specific equipment. However, there are several drawbacks: the method is time-consuming, requires large amounts of chemicals and the consistency of results depends on the operator's skills. With this in mind, an improved method was developed to analyze CO2 captured in alkali traps, which is cheap and relatively simple, with a substantially shorter sample handling time and reproducibility equivalent to the traditional titration method. A comparison of the concentration values determined by gas phase flow injection analysis (GPFIA) and titration showed no significant difference (p > 0.05), but GPFIA has the advantage that only a tenth of the sample volume of the titration method is required. The GPFIA system does not require the purchase of new, costly equipment but the device was constructed from items commonly found in laboratories, with suggestions for alternative configurations for other detection units. Furthermore, GPFIA for CO2 analysis can be equally applied to samples obtained from either the headspace of microcosms or from a sampling chamber that allows CO2 to be released from alkali trapping solutions. The optimised GPFIA method was applied to analyse CO2 released from degrading hydrocarbons from a site contaminated by diesel spillage. A taxa de produção de dióxido de C é comumente utilizada como medida da atividade microbiana no solo. O método tradicional de determinação de CO2 envolve a captura do CO2 em solução alcalina e determinação indireta por meio da titulação da base remanescente em solução. Esse método é ainda comumente empregado em laboratórios por todo o mundo, devido à sua relativa simplicidade e ao fato de não ser dependente de equipamento caro e específico. No entanto, o método possui várias desvantagens: é demorado, utiliza-se grande quantidade de reagentes químicos e a consistência dos resultados depende da habilidade de quem está analisando. Desse modo, foi desenvolvido um método otimizado de análise de CO2 capturado em soluções alcalinas, de baixo custo e relativamente simples, o qual fornece tempo de manuseio da amostra melhorado e com reprodutibilidade equivalente à do método de titulação tradicional. Uma comparação dos valores de concentração determinados por análise por injeção em fluxo em fase gasosa (GPFIA) e titulação mostrou que eles não foram significativamente diferentes (p > 0,05), porém o GPFIA teve a vantagem de utilizar um décimo da quantidade de amostra do método da titulação. O sistema GPFIA não necessita de equipamentos novos e caros, tendo sido construído a partir de itens comumente encontrados em laboratórios, com sugestões para configurações alternativas para outras unidades de detecção. Além disso, o GPFIA para análise de CO2 pode ser igualmente aplicado em amostras obtidas tanto de "headspace'' do microcosmo como de amostragens em câmaras que permitem o CO2 ser liberado da solução alcalina de captura. O método otimizado GPFIA foi aplicado para análise de CO2 liberado da degradação de hidrocarbonetos de um local contaminado por derramamento de diesel.

In this work, a method for the determination of phosphorus in biodiesel (B100) using flow injection analysis with spectrophotometric detection (FIA-SD) is described. Samples were digested using an acid mixture in a heating block. The phosphorus concentrations obtained by the (FIA-SD) method were similar to those obtained by the official method. Recovery tests show results between 98.6% and 101.0% for biodiesel produced from sunflower and between 102.1% and 113.5% for biodiesel produced from castor and soybeans. The limits of detection (LOD) and quantification (LOQ) obtained using the FIA system were 0.14 mg L−1 and 0.46 mg L−1, respectively.

A bare graphite-polyurethane composite was evaluated as an amperometric flow injection detector in the determination of paracetamol (APAP) in pharmaceutical formulations. A linear analytical curve was observed in the 5.00 x 10-5 to 5.00 x 10-3 mol L-1 range with a minimum detectable net concentration of 18.9 µmol L-1 and 180 determinations h-1, after optimization of parameters such as the detection potential, sample loop volume, and carrier solution flow rate. Interference of ascorbic acid was observed, however, it was possible overcome the interference, reaching results that agreed with HPLC within 95% confidence level. These results showed that the graphite-polyurethane composite can be used as an amperometric detector for flow analysis in the determination of APAP. Um eletrodo compósito de grafite-poliuretana sem modificação foi avaliado como um detector amperométrico para análise em fluxo, na determinação de paracetamol (APAP) em formulações farmacêuticas. Uma curva analítica foi obtida com região linear entre 5,00 x 10-5 e 5,00 x 10-3 mol L-1, com um limite de detecção de 18,9 µmol L-1 e 180 determinações por hora, depois de parâmetros otimizados como potencial de detecção, volume de amostragem, e vazão da solução carregadora. Interferência de ácido ascórbico foi observada, entretanto foi possível contorná-la, como visto pelos resultados que concordaram com HPLC com nível de confiança de 95%. Estes resultados mostraram que o compósito grafite-poliuretana pode ser usado como um detector amperométrico para análise em fluxo na determinação de APAP.

In order to improve the quality control of dehydrated broth, a new automated method was developed to determine total creatinine in dehydrated broths. The sample pretreatment was coupled on-line with the Flow Injection Analysis (FIA) system for analyte determination by the classical Jaffe reaction, stopped flow methodology, and spectrophotometric detection. The time consumed was reduced from 7h, which is necessary with the official method, to 25 min. The calibration graph is linear between 0.342-1.368 mg creatinine/ 100 mL. The relative standard deviation (RSD%) was 1.7%, the sample throughput was 7 h -1, and the detection limit was 0.185 mg creatinine/100 mL. The validation of the proposed method was carried out with real samples. The obtained results were compared with those obtained from the Association of Official Analytical Chemists (AOAC) reference method. Fil: Acebal, Carolina Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Centurión, María Eugenia. Universidad Nacional del Sur. Departamento de Química; Argentina Fil: Lista, Adriana Guillermina. Universidad Nacional del Sur. Departamento de Química; Argentina Fil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina

A flow injection turbidimetric method for determination of cyclamate in low calorie soft drinks and sweeteners without pre-treatment is proposed. It was based on the oxidation of the sulphamic group of cyclamate, to sulphate by addition of nitrite. Then, a precipitate of sulphate was obtained by reaction with barium chloride, in presence of poly(vinyl alcohol) (PVA) in perchloric acid solution, at 30°C. The analytical signal was measured at 420 nm. The method presented a linear range between 0.015 and 0.120% (w/v) and the calibration graph was S = (7.792 ± 0.179) X - (0.114 ± 0.012), R2 = 0.999. A reproducibility of 5.9% was obtained from nine calibration graphs that were carried out on different days and with different conditions (standard solution, reagents solution, etc.). The detection and quantification limits were 0.006 and 0.02% (w/v), respectively, the sample throughput 45 h-1 (by considering the wash cycle and the time consuming to eliminate the clean solution from the system). The obtained results were agreement with that obtained with the standard method. Fil: Llamas, Natalia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina

The present manuscript deals with a simple and sensitive flow-injection method for the chemiluminescent determination of thiazides. The method is based on the on-line photodegradation and chemiluminescent determination of the resulting photo-fragments. The on-line photodegradation is performed in basic medium by using a photoreactor consisting of a 550 cm long x 0.8 mm ID piece of PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. The determination of the photo-irradiated thiazides is performed by a chemiluminescent oxidative reaction with Ce(IV) in sulphuric acid medium. A heterogeneous group of thiazides (indapamide, metolazone, hydroflumethiazide, chlorthalidone and bendroflumethiazide) has been studied. Hydrochlorothiazide was selected as a test substance. The "on-line" photochemical reaction approach allows the sensitive chemiluminescent determination of thiazides which do not present native chemiluminescence in the absence of sensitizers such as Rhodamine 6G. Linear calibration graphs were typically over the range 0.5-12 mug ml(-1) (indapamide, metolazone, hydroflumethiazide and chlorthalidone); and over the range 0.5-5 mug ml(-1) (hydrochlorothiazide). Limits of detection ranged between 0.005 mug ml(-1) (hydrochlorothiazide) and 0.06 mug ml(-1) (bendroflumethiazide). The relative standard deviation for the test substance was 2.0% for 2 mug l(-1) of the drug (n = 11) and the throughput was 65 h(-1) in all cases. The assessment of the photodegradation step on the molecular structure of thiazides was established by recording UV and fluorimetric spectra. The viability of the on-line photoinduced fluorescent determination of hydroflumethiazide and bendroflumethiazide was confirmed. The method was also applied to the determination of hydrochlorothiazide in commercially available formulation. (C) 2004 Elsevier B.V. All rights reserved.

A square-wave voltammetric (SWV) method and a flow injection analysis system with amperometric detection were developed for the determination of tramadol hydrochloride. The SWV method enables the determination of tramadol over the concentration range of 15-75 microM with a detection limit of 2.2 microM. Tramadol could be determined in concentrations between 9 and 50 microM at a sampling rate of 90 h(-1), with a detection limit of 1.7 microM using the flow injection system. The electrochemical methods developed were successfully applied to the determination of tramadol in pharmaceutical dosage forms, without any pre-treatment of the samples. Recovery trials were performed to assess the accuracy of the results; the values were between 97 and 102% for both methods.

One of the main factors limiting agricultural production in tropical climate regions is mainly related to the presence of exchangeable aluminum (Al3+) in highly weathered acid soils. Four methods of Al3+ determination extracted with neutral 1 mol L¹ KCl solution were evaluated: three colorimetric methods (aluminon plus ascorbic acid, and eriochrome cyanine R by FIA) and the usual titrimetric method with back-titration. Surface samples from 20 soils of different Brazilian regions, with active acidity (0.01 mol L¹ CaCl2 pH) ranging from very high to medium (3.82 to 5.52), were used. The variance analysis revealed significant interaction among Al3+ determination methods and soil. Mean methods comparisons within each soil (Tukey, P < 0.05) indicated that, for most of the soils, the methods differed among each other, although there were high correlations between the obtained values. Al3+ values determined for soil samples by titration varied between 0.15 and 14.71 mmol c dm³. The colorimetric methods showed higher values than the titration method, mainly for those with aluminon (up to 18.75 mmol c dm-3). The Al3+ contents of colorimetric methods correlated quadraticaly with the titration values, for the soil samples with Al3+ > 10 mmol c dm³. Among colorimetric methods, in operational terms, the eriochrome with FIA method presented analytical performance up to 50 samples per hour, easiness and sensibility for routine Al analysis in soil samples. However, due to the specificity, the titration/back-titration method should be used, despite the moroseness, when the Al3+ ions are the objective. Um dos principais fatores que afetam a produção agrícola em regiões de clima tropical, é a presença de alumínio trocável (Al3+) em solos ácidos altamente intemperizados. Foram avaliados quatro métodos de determinação de alumínio trocável em solução neutra de KCl 1 mol L¹: três métodos colorimétricos (aluminon, aluminon + ácido ascórbico e eriocromo cianina R por FIA) e o método titulométrico usual com retrotitulação ácida. Para obtenção dos extratos de KCl, foram usadas amostras superficiais de 20 solos de diferentes regiões brasileiras, com acidez ativa (pH em CaCl2 0,01 mol L¹) variando de muito alta a média (3,82 a 5,52). A análise de variância revelou interação significativa entre os métodos de determinação e amostras de solos. O teste de médias (Tukey, P < 0,05) de métodos dentro de amostras evidenciou, para a maioria das amostras de solos, que os métodos analíticos diferenciaram entre si, embora tenha havido forte correlação entre os valores obtidos. Os valores de Al3+ determinados por titulação variaram de 0,15 a 14,71 mmol c dm³. Os métodos colorimétricos apresentaram valores superiores aos da titulação, notadamente aqueles com aluminon (até 18,75 mmol c dm³). Os teores de Al3+ dos métodos colorimétricos se relacionaram quadraticamente com os teores obtidos por titulação, em amostras de solos com Al3+ > 10 mmol c dm³. Dentre os métodos colorimétricos, o reagente eriocromo cianina R, em sistema FIA, mostrou-se operacionalmente confiável e eficiente para a análise de Al, de amostras de solos, em rotina, com freqüência analítica de 50 determinações por hora. Todavia, devido à especificidade, o método titulométrico com retrotitulação deve ser usado, não obstante a morosidade, quando o objetivo é a determinação do íon Al3+.

The work describes a new procedure for cetylpyridinium chloride determination in oral disinfectants, based on a flow-injection system with potentiometric detection. The determination was based on the measurement of picrate concentration decrease as result of ion-pair reaction with the analyte present in the injected sample. In the optimised set-up the sample injection volume was kept at 400 µL and merged downstream with the reagent solution containing 1,0 x10-5 mol/L of picrate adjusted to pH 5.0 with citrate/citric acid buffer. The flow rate was fixed at 8 mL/min and the reactor length at 40 cm. The proposed procedure enables the determination of cetylpyridinium in the analytical range of 5,0x10-6 - 7,5x10-5 mol/L at a sampling rate of 60/h. The results for real samples had a precision better than 3% and were comparable to the labelled values.

Design of the fluoride ion-selective electrode (FISE) as the tubular detector used in the flow injection analysis (FIA) has been described. Among other things, this design makes it possible to use various internal contacts. The effect of pH on peak height and detection limit in the pH range from 2.8 to 8.0 has been examined. The effect of flow rate and sample injection volume on peak height and range of linear response has also been examined. The flow rates range from 0.56 mL/min to 4.05 mL/min, while the injection volumes are 100 and 200 μL. The optimum conditions are carrier solution (0.1 M KNO3 buffer pH 4 and 10-6 M NaF), flow rate 1.54 mL/min and sample injection volume 100 μL. Applicability of the FISE as the tubular detector in determination of Fe(III)-ions and AI(III)-ions by flow infection analysis has been examined at pH values of 2.8 and 3.4.

Phenol and o-cresol determination by flow injection analysis (FIA) with spectrophotometric detection, employing the 4-aminoantipyrine reaction, is proposed in this work in order to quantify these species in soil extracts. The method was improved by a factorial planning, being verified a higher sampling rate in comparison with the conventional method, and recovery values, limits of detection and quantification similar for both methods. These aspects suggest this method as a feasible alternative for phenolic compound determinations in soil extracts. Neste trabalho, propõe-se a determinação de fenol e o-cresol por análise por injeção em fluxo (FIA) com detecção espectrofotométrica, utilizando a reação com 4-aminoantipirina, a fim de quantificar essas espécies em extratos de solo. Após otimização das condições por planejamento fatorial, constatou-se uma maior frequência de amostragem em comparação com o método convencional, bem como valores de recuperação, limites de detecção e de quantificação comparáveis para ambos os métodos. Tais aspectos sugerem que esse método pode ser uma alternativa viável para a determinação de compostos fenólicos em extratos de solos.

A simple flow system with multiple pulse amperometric detection using a single working electrode is proposed for simultaneous determination of ascorbic (AA) and acetylsalicylic (AAS) acids in pharmaceutical formulations. The procedure is based on application of two potential pulses: 0.90 V/50 ms: oxidation and determination of AA without the interference of AAS; 1.35 V/50 ms: oxidation of both compounds and quantification of AAS by current subtraction using a correction factor. Sampling rate was estimated as 125 injections per hour and the limits of detection were 0.17 and 0.16 µmol L-1 for AA and AAS, respectively. Results for commercial samples agreed with those obtained using HPLC.

This article reports a flow-injection spectrophotometric determination (FIA) with a photodegradation step to determine ascorbic acid and total sugars. The flow-injection system includes a simple ultraviolet photoreactor for the on-line photodegradation. The method is based on the determination of ascorbic acid at 300. nm before the photodegradation step, followed by UV irradiation and measurement of total sugars at 268. nm. The proposed method was used to determine ascorbic acid and total sugars in commercial and natural fruit juice samples. The method was validated by using spiked samples with recoveries in the range 96.4-108.3% for ascorbic acid, and 91.0-113.2% for total sugars. © 2010 Elsevier Inc. Fil: Llamas, Natalia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Di Nezio, Maria Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina

A biomimetic sensor for norfloxacin is presented that is based on host-guest interactions and potentiometric transduction. The artificial host was imprinted into polymers made from methacrylic acid and/or 2-vinyl pyridine. The resulting particles were entrapped in a plasticized poly(vinyl chloride) (PVC) matrix. The sensors exhibit near-Nernstian response in steady state evaluations, and detection limits range from 0.40 to 1.0 μg mL−1, respectively, and are independent of pH values at between 2 and 6, and 8 and 11, respectively. Good selectivity was observed over several potential interferents. In flowing media, the sensors exhibit fast response, a sensitivity of 68.2 mV per decade, a linear range from 79 μM to 2.5 mM, a detection limit of 20 μg mL−1, and a stable baseline. The sensors were successfully applied to field monitoring of norfloxacin in fish samples, biological samples, and pharmaceutical products.

A new man-tailored biomimetic sensor for Chlorpromazine host-guest interactions and potentiometric transduction is presented. The artificial host was imprinted within methacrylic acid, 2-vinyl pyridine and 2-acrylamido-2-methyl-1-propanesulfonic acid based polymers. Molecularly imprinted particles were dispersed in 2-nitrophenyloctyl ether and entrapped in a poly(vinyl chloride) matrix. Slopes and detection limits ranged 51–67 mV/decade and 0.46–3.9 μg/mL, respectively, in steady state conditions. Sensors were independent from the pH of test solutions within 2.0–5.5. Good selectivity was observed towards oxytetracycline, doxytetracycline, ciprofloxacin, enrofloxacin, nalidixic acid, sulfadiazine, trimethoprim, glycine, hydroxylamine, cysteine and creatinine. Analytical features in flowing media were evaluated on a double-channel manifold, with a carrier solution of 5.0 × 10−2 mol/L phosphate buffer. Near-Nernstian response was observed over the concentration range 1.0 × 10−4 to 1.0 × 10−2 mol/L. Average slopes were about 48 mV/decade. The sensors were successfully applied to field monitoring of CPZ in fish samples, offering the advantages of simplicity, accuracy, automation feasibility and applicability to complex samples.

International audience; Developments in UV/VIS spectrophotometry during the past decade are critically reviewed. Advances in instrumentation: sample handling, optical systems, detectors, and signal processing are discussed. The application of spectrophotometric detection in hydrodynamic systems is surveyed. Newer types of color systems employing macrocyclic compounds, porphyrines, surfactants, and basic dyes are evaluated. Separate sections are devoted to advances in spectrophotometric determination both of individual elements and organic compounds. Future trends in spectrophotometric analysis are discussed. © 1992, Taylor & Francis Group, LLC. All rights reserved.

Flow injection analysis (FIA) with ESI-MS and ion chromatography (IC) with inductively coupled plasma-MS (ICP-MS) as the complementary technique have been explored for the determination of metal ions as their metal-EDTA complexes. ESI-MS enabled the identification of metal-EDTA complexes such as [Mn(EDTA)](2-), [Co(EDTA)](2-), [Ni(EDTA)](2-), [Cu(EDTA)](2-), [Zn(EDTA)](2-), [Pb(EDTA)](2-), and [Fe(EDTA)](1-) and their MS spectral showed that these metal-EDTA complexes were present in solution. Based on the ESI-MS, ion chromatographic separation and ICP-MS detection of these complexes are possible because IC-ICP-MS requires stable metal-EDTA complex during the chromatographic separation. The separation of these metal-EDTA complexes was achieved on an anion-exchange column with a mobile phase containing 30 mM NH(4)(HPO(4))(2) at pH 7.5 within 7 min with ICP-MS providing element specific detection. The ICP-MS LODs for the metal-EDTA were in the range of 0.1-0.5 microg/L with the exception of Fe (15 microg/L). The proposed method was a simple procedure for sample processing, using direct injection of sample without removal of sample matrix and was successfully applied to the determination of metal-EDTA complexes in real samples.

The native fluorescence of ibuprofen was enhanced when a host-guest complex of the analyte with b cyclodextrin (b-CD) was formed. So, based on this fact, a flow injection method to determine ibuprofen in different pharmaceutical preparations with fluorescence detection (lem 287 nm, lexc 223 nm) was developed. The calibration curve was linear over the range 6.00 – 60.0 mg L-1 of ibuprofen and the detection limit (LOD) for S/N=3 was 4.5 mg L-1. The relative standard deviation was 1.2% and the sample throughput 240 h-1. The method was validated by comparing the proposed and the official method to commercial preparation samples. A fluorescência natural da ibuprofeína foi melhorada quando foi formado um complexo convidado-hospedeiro com a beta-ciclodextrina (beta-CD). A partir disso, foi desenvolvido um método por injeção em fluxo para a determinação de ibuprofeína em diferentes preparações farmacêuticas, com detecção fluorescente (lem 287 nm, lex 233 nm). A curva de calibração foi linear no intervalo entre 6,00 a 60,0 mg L-1 de ibuprofeína, com limite de detecção (LOD para S/N=3) de 4,5 mg L-1. O desvio padrão relativo foi de 1,2% e a velocidade de determinação de 240 amostras por hora. O método foi validado pela comparação do método proposto, e do usado oficialmente, em amostras comerciais preparadas. Fil: Lista, Adriana Guillermina. Universidad Nacional del Sur. Departamento de Química. Química Analitica; Argentina Fil: Palomeque, Miriam Edid. Universidad Nacional del Sur. Departamento de Química. Química Analitica; Argentina Fil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina

Fabrication of an amperometric-rotating biosensor for the enzymatic determination of cholesterol is reported. The assay utilizes a combination of three enzymes: cholesterol esterase (ChE), cholesterol oxidase (ChOx) and peroxidase (HRP); which were co-immobilizing on a rotatory disk. The method is developed by the use of a glassy carbon electrode as detector versus Ag/AgCl/3 M NaCl in conjunction with a soluble-redox mediator 4-tert-butylcatechol (TBC). ChE converts esterified cholesterol to free cholesterol, which is then oxidized by ChOx with hydrogen peroxide as product. TBC is converted to 4-tert-butylbenzoquinone (TBB) by hydrogen peroxide, catalyzed by HRP, and the glassy carbon electrode responds to the TBB concentration. The system has integrated a micro packed-column with immobilized ascorbate oxidase (AAOx) that works as prereactor to eliminate l-ascorbic acid (AA) interference. This method could be used to determine total cholesterol concentration in the range 1.2 μM-1 mM (r = 0.999). A fast response time of 2 min has been observed with this amperometric-rotating biosensor. Lifetime is up to 25 days of use. The calculated detection limits was 11.9 nM. Reproducibility assays were made using repetitive standards solutions (n = 5) and the percentage standard error was less than 4%. Fil: Salinas, Eloy. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Departamento de Química; Argentina Fil: Rivero Osimani, Valeria Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; Argentina Fil: Torriero, Angel Alberto Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; Argentina Fil: Benuzzi, Delia Aurora. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Departamento de Química; Argentina Fil: Sanz Ferramola, Maria Isabel. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Departamento de Química; Argentina Fil: Raba, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; Argentina

The spectrophotometric determination of Cd(II) using a flow injection system provided with a solid-phase reactor for cadmium preconcentration and on-line reagent preparation, is described. It is based on the formation of a dithizone-Cd complex in basic medium. The calibration curve is linear between 6 and 300 μg L-1 Cd(II), with a detection limit of 5.4 μg L -1, an RSD of 3.7% (10 replicates in duplicate) and a sample frequency of 11.4 h-1. The proposed method was satisfactorily applied to the determination of Cd(II) in surface, well and drinking waters. Fil: Di Nezio, Maria Susana. Universidad Nacional del Sur. Departamento de Química; Argentina Fil: Palomeque, Miriam Edid. Universidad Nacional del Sur. Departamento de Química; Argentina Fil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina

[EN] A flow injection analysis (FIA) manifold for the determination of penicillamine in pharmaceutical preparations is proposed. The manifold includes a solid-phase reactor for the in situ production of the derivatizing reagent, Co(II) ion, which forms a coloured complex with penicillamine in an alkaline medium. The reactor is prepared by natural immobilization of cobalt carbonate on a polymer matrix, which endows it with a high mechanical and microbiological stability. The cobalt released by passage of a 5 x 10(-4) Mol l(-1) sulphuric acid stream at a flow-rate of 2.3 ml min(-1) is merged with a volume of 314 mu l of sample containing penicillamine in ammonium-ammonia buffer at pH 9.5 to measure the absorbance at 360 nm. Beer's law is obeyed over the penicillamine concentration range 5-60 mg l(-1). The limit of detection (LOD) of the method is 1 mg l(-1) and its throughput 70 samples h(-1). (c) 2005 Elsevier B.V. All rights reserved.

A new flow injection (FI) system for the determination of Pb(II) at trace level with a preconcentration step and spectrophotometric detection is proposed. It is based on preconcentration of lead ions on chitosan and dithizone-lead complex formation in aqueous medium (pH 9). The chemicals and FIA variables influencing the performance of the system were optimized and applied to the determination of lead in natural, well, and drinking water samples. It is a simple, highly sensitive, and low cost alternative methodology. The method provided a linear rage between 25 and 250 μg l-1, a detection limit of 5.0 ng ml-1 and a sample throughput of 15 h-1. The obtained results of spiked samples are in good agreement between the proposed method and ICP-AES. Fil: Di Nezio, Maria Susana. Universidad Nacional del Sur. Departamento de Química; Argentina Fil: Palomeque, Miriam Edid. Universidad Nacional del Sur. Departamento de Química; Argentina Fil: Fernández Band, Beatriz Susana. Universidad Nacional del Sur. Departamento de Química; Argentina

Whey is an abundant effluent in the production of cheese and casein. The biotechnological utilization of this economically important and nutritive source is limited mainly because of the presence of high percentages of lactose. This disaccharide has poor solubility, which can cause crystallization and insufficient sweetness in dairy food; additionally, part of the adult population suffers from associated lactose intolerance diseases. There are several methods to determine lactose such as spectrophotometry, polarimetry, infrared spectroscopy, titrimetry and chromatography. However these methods are tedious and time-consuming due to long sample preparation. These disadvantages stimulated the development of an enzymatic lactose biosensor. It employs two immobilized enzymes, beta-galactosidase and glucose oxidase and the quantitative analysis of lactose is based on determination of oxygen consumption in the enzymatic reaction. The influence of temperature on the biosensor signal was 'experimentally studied. It was observed that a nonlinear relationship exists between the electric response of the biosensor - provided by CAFCA (Computer Assisted Flow Control & Analysis - ANASYSCON, Hannover) - and lactose concentration. In this work, attempts were made to correlate these variables using a simple nonlinear model and multilayered neural networks, with the latter providing the best modeling of the experimental data.

A novel flow injection analysis (FIA) method with Rayleigh light scattering (RLS) detection was developed for the determination of total protein concentrations. This method is based on the weak intensity of RLS of bromothymol blue (BB) (3′,3″-dibromothymolsulfonephthalein) which can be enhanced by the addition of protein in weakly acidic solution. A common spectrofluorimeter was used as a detector. It was proved that the application of this method to quantify the total proteins in real samples by using bovine serum albumin was possible. The RLS signal was detected at λ ex=λ em=572 nm. The linear range was 7.0-70.0 μg mL-1, the detection limit was 3.75 μg mL-1, the reproducibility was 5.5% (n=7), and the sample throughput was 26 h-1. Fil: Vidal, Ezequiel Martin. Universidad Nacional del Sur. Departamento de Química. Química Analítica; Argentina Fil: Palomeque, Miriam Edid. Universidad Nacional del Sur. Departamento de Química. Química Analítica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Lista, Adriana Guillermina. Universidad Nacional del Sur. Departamento de Química. Química Analítica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Fernández Band, Beatriz Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina. Universidad Nacional del Sur. Departamento de Química. Química Analítica; Argentina

Two analytical methods for the quality control of dihydrocodeine in commercial pharmaceutical formulations have been developed and compared with reference methods: a square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC). The electrochemical methods proposed were successfully applied to the determination of dihydrocodeine in pharmaceutical tablets and in oral solutions. These methods do not require any pretreatment of the samples, the formulation only being dissolved in a suitable electrolyte. Validation of the methods showed it to be precise, accurate and linear over the concentration range of analysis. The automatic procedure based on a flow injection analysis manifold allows a sampling rate of 115 determinations per hour.

International audience; A conducting polymer of poly 3,4-ethylenedioxythiophene (PEDT) was used as a matrix for entrapment of enzymes onto a platinum electrode surface in order to construct amperometric biosensors. Glucose oxidase (GOD) was used as an example, and it was entrapped in the polymer during the electrochemical polymerization. Glucose in oxygenated solutions was tested by amperometric measurements at +650 mV (vs. SCE) in a batch system. The influence of several experimental parameters in the electropolymerization process was explored to optimize the analytical performance. The detection limit and sensitivity for this biosensor were 4×10−5 M and 15.2 mA M−1cm−2, respectively. A linear range of response was found from 0.2 to 8 mM of glucose. The response time was 2–5 s. The stability of the electropolymerized films was evaluated in operational conditions. The glucose probe, stored in buffer at 4 °C when not in use, showed a residual activity of 40% after about 1 month. Glucose in synthetic serum was determined under flow injection conditions using an amperometric flow cell.

International audience; The simultaneous determination of copper and zinc in human plasma and urine by inductively coupled plasma mass spectrometry (ICP MS) is discussed. The performances of a cross-flow nebulizer and a direct-injection nebulizer (DIN) were compared. Flow-injection-DIN-ICP MS analysis of clinical samples using 1-2 ?l samples was optimized. Isobaric interferences were discussed and were demonstrated to be eliminated for the 65Cu and most of the Zn nuclides. The need for standard addition to compensate for signal suppression in the case of some serum samples was indicated. Results obtained by ICP MS using calibration with aqueous standard solutions were found to be in good agreement with those obtained by flame AAS for a batch of real blood plasma and urine samples. The methods developed were validated by analysis of several standard reference materials.

An immobilized hybridoma cell line was cultivated at controlled glucose and glutamine concentrations. On-line analysis of the substrates was carried out with a multi-channel flow injection analysis system. The analysis system also determined on-line the lactate and ammonium concentration. The substrate concentrations were controlled using an adaptive-control strategy. This strategy consisted of the estimation of the real-time concentrations and volumetric substrate consumption rates by an Extended Kaiman Filter, and a minimum variance controller, which used the estimated parameters to set the feed rates of the substrates. The closed-loop control was used to start-up two cultures with either glucose or glutamine as control-substrate for the medium feed rate. The controller kept the concentration of the control-substrate constant by enhancing the medium feed rate simultaneously to the increasing volumetric consumption rate of the substrate. When glutamine was used as control-substrate, the glucose concentration remained relatively constant, whereas the glutamine concentration decreased during the start-up at a constant glucose concentration. This indicates that glutamine is consumed faster than glucose and will be a better control-substrate to avoid limitation during the start-up of a culture with the applied hybridoma cell line. During the colonization of the microcarriers, the yield of ammonium on glutamine decreased from 0.80 to 0.55 (mol mol−1), indicating a change in the glutamine metabolism. The yield of lactate on glucose stayed constant for both experiments. During long-term culture of more than 800 h, the controller kept both the glucose and glutamine concentrations constant at perfusion rates between 0.50 h−1 and 0.15 h−1. The medium, glucose and glutamine feed rate were independently controlled. Both the specific glutamine and glucose consumption rates remained constant for all perfusion rates, which was probably as a result of the constant concentrations. The specific monoclonal antibody production rate decreased with the perfusion rate decreasing from 0.40 h−1 to 0.20 h−1. The immobilized-cell concentration decreased only at the lowest perfusion rate. Both effects could not be explained directly by the increasing ammonium and lactate concentrations nor by the decreasing amino-acid concentrations.

A flow injection system for the determination of acetic acid in the 10–60 mM range was conceived and optimized on basis of the coupled reactions of acetate kinase/pyruvate kinase/lactate dehydrogenase. The enzymes were immobilized in series, a reagent mixture containing PEP, ATP and NADH was pulsed into the analyte stream, and the decrease of the NADH absorption was determined. One injection cycle was performed within 90 s. Two identical parallel enzyme lines were installed, one of them being in use while the other was calibrated. Automated calibration, control of sample dilution, compensation for enzyme activity loss, the switching between the two enzyme lines and the control of all instruments were performed by an appropriate computer system. The analysis of vinegar samples resulted correct and reliable results. The semi-automated control of continuous vinegar production of 60 h yielded very satisfactory results in the range of 0.5–1.5 M after 40-fold dilution and was more reliable than the reference HPLC method. The extension of the analysis system to higher concentrations ranges still demands an optimization of the dilution method. In total, the enzyme-based FIA for continuous acetic acid determination seems to be a very useful and reliable method.

International audience; An enzyme immobilization technique has been developed to determine the concentration of biological compounds. This technique has been applied to penicillinase and urease, which are crosslinked as very fine films directly onto the sensitive ends of pH glass electrodes, thereby dispensing with the need of an on-line enzyme reactor. The biosensor is incorporated in an FIA system within a magnetically stirred detection cell. Penicillin-V in fermentation broth and urea in human serum samples were detected and the results were compared with HPLC and spectrophotometric methods. On-line measurement is achieved through the automation of this FIA system.

A new compact system encompassing in flow gas diffusion unit and a wall-jet amperometric FIA detector, coated with a supramolecular porphyrin film, was specially designed as an alternative to the time-consuming Monier-Williams method, allowing fast, reproducible and accurate analyses of free sulphite species in fruit juices. In fact, a linear response between 0.64 and 6.4 ppm of sodium sulphite, LOD = 0.043 ppm, relative standard deviation of ±1.5% ( n = 10) and analytical frequency of 85 analyses/h were obtained utilising optimised conditions. That superior analytical performance allows the precise evaluation of the amount of free sulphite present in foods, providing an important comparison between the standard addition and the standard injection methods. Although the first one is most frequently used, it was strongly influenced by matrix effects because of the unexpected reactivity of sulphite ions with the juice matrixes, leading to its partial consumption soon after addition. In contrast, the last method was not susceptible to matrix effects yielding accurate results, being more reliable for analytical purposes.