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An on-line synthesis of CDots is proposed for the first time, using the flow injection analysis (FIA) technique, which was coupled, in a single system, to the analytical determination of aluminium in water samples. The nanoparticles were obtained from the carbonization of glucose and iron(III) in an acidic medium, and their photoluminescence increased in the presence of aluminium ions. Under optimal experimental conditions, the proposed method has shown an acceptable linearity range –between 0.04 and 3.0 mg L−1 (R2 = 0.9999) – and a detection limit of 0.007 mg L−1. The analysis of drinking water and groundwater samples showed good accuracy (recoveries ranged between 91 – 113%) and RSD% < 13. The on-line system exhibited a high sample throughput (36 h−1), since no incubation time was required.

A new and environmentally friendly analytical method for simultaneous determination of As, Cd, Hg and Pb in drug samples by inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. In order to increase the sensitivity of the analysis, a multinebulizer has been used for chemical vapor generation (CVG) after a dispersive liquid-liquid microextraction (DLLME) procedure using a natural deep eutectic solvent (NADES) as extractant solvent. The factors affecting analyte extraction and on-line chemical vapor generation have been optimized by multivariate analysis. Under optimized conditions, DLLME-CVG-ICP OES improved limit of quantitation (LOQ) values on average 50-fold higher compared with direct ICP OES analysis and afforded an increase of the sensitivity (i.e., enrichment factor) on average 25-times higher than those obtained with CVG-ICP OES analysis. According to the United States Pharmacopoeia (USP) Chapter 232, it means LOQ values are on average 4.3-times lower than their respective 0.3J values for the target-elements from class 1. Trueness has been evaluated by recovery experiments following USP recommendations for two oral drug samples in solid dosage form (i.e., commercial dosage tablets). In addition, the greenness of the developed method has been evaluated using the AGREEprep metrics, showing an excellent green character since it includes the miniaturization of the sample preparation procedure using a reduced volume (i.e., few microliters) of a non-hazardous extractant solvent for multielemental analysis.

A new fast, sensitive, and environmentally friendly analytical method has been developed for the simultaneous determination of Ba, Be, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in wastewater samples using inductively coupled plasma optical emission spectroscopy (ICP OES). A preconcentration step using a magnetic dispersive solid-phase extraction (MDSPE) technique with a new magnetic sorbent was performed. The new sorbent material was a carbon containing magnetic cobalt and nitrogen groups. This material was synthetized using controlled pyrolysis of a zeolitic imidazolate framework (i.e., ZIF-67). In order to optimize the experimental parameters that affect the MDSPE procedure, a multivariate optimization strategy, using Plackett–Burman and circumscribed central composite designs (CCD), was used. The method has been evaluated employing optimized experimental conditions (i.e., sample weight, 10 g; sample pH, 7.6; amount of sorbent, 10 mg; dispersive agent, vortex; complexing agent concentration, 0.5%; ionic concentration, 0%; eluent, HCl; eluent concentration, 0.5 M; eluent volume, 300 μL; elution time, 3 min and extraction time, 3 min) using external calibration. Limits of detection (LODs) in a range from 0.073 to 1.3 μg L−1 were obtained, and the repeatability was evaluated at two different levels, resulting in relative standard deviations below 8% for both levels (n = 5). An increase in the sensitivity was observed due to the high enrichment factors (i.e., 3.2 to 13) obtained compared with direct ICP OES analysis. The method was also validated through carrying out recovery studies that employed a real wastewater sample and through the analysis of a certified reference material (ERM®-CA713). The recovery values obtained with the real wastewater were between 94 and 108% and between 90 and 109% for the analysis of ERM®-CA713, showing negligible matrix effects.

A novel simple, environmentally friendly and portable method to determine vitamin E in edible oils based on reversed-phase dispersive liquid-liquid microextraction combined with electrochemical detection using screen-printed carbon electrodes (SPCEs) has been developed. Vitamin E was extracted from oil samples into a 4 M HCl aqueous solution and determined by differential pulse voltammetry using SPCEs. The extraction conditions optimized by experimental design (i.e., Plackett–Burman and central composite designs) were: aqueous 4 M HCl extractant volume, 43 µL; extraction time, 2 min; centrifugation time, 10 min; and centrifugation speed, 3000 rpm. The proposed method requires a standard addition calibration approach, and the working range showed good linearity from 0 to 20 mg L−1, with a correlation coefficient ranging from 0.990 to 0.995 (N=5). The methodological limit of detection was between 1 and 3 mg L−1. The repeatability of the proposed method was evaluated at 15 mg L−1, and the relative standard deviation ranged between 10 and 15% (n=5). For the quantification of vitamin E in ten commercial samples of olive, sesame, soybean, sunflower and a mixture of sunflower and corn oils, the volume of the extractant phase (i.e., 4 M HCl aqueous solution) was increased up to 100 µL and satisfactory recoveries were obtained in the range of 85–115%, confirming the applicability of the method.

Two analytical methods based on miniaturized electrochemical sensors, voltammetric and amperometric sensors, have been developed for the determination of 6-methyl-2-thiouracil (MTU) in meat consumption samples (beef liver and foie). A multivariate approach has been considered to optimize the experimental procedure including extraction and electrochemical detection. Under optimal conditions and at a typical working potential of 1.55 V (vs Ag pseudo-reference electrode), response is linear in the range 0 to 20 µg L−1 MTU concentration range. The empirical limit of detection is 0.13 µg L−1, lower than the maximum concentration established by legislation. The electrochemical methods have been used to analyze MTU-spiked meat samples, and recovery values varying between 85 and 95% with coefficients of variation

In this work, on-line calibration methods were applied for compensation for matrix effects in Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) using three novel multiple sample introduction systems based on Flow Blurring®technology. The methods were compared with conventional calibration methods, using a Conikal nebulizer and a cyclonic spray chamber (i.e., Standard Sample Introduction (SSI) system). Experiments were carried out with synthetic samples containing different matrices. The total liquid flow through the multinebulizers was 400 μL min−1whereas in the SSI system it was 1000 μL min−1. One type of calibration method tested was external calibration. By using this calibration method, the mean of absolute values corresponding to the relative error values of different multiple sample introduction systems and all the matrices was 14% and uncertainty was 0.6%. When on-line internal standard calibration was used, the mean relative error value dropped to 3% and uncertainty was 0.6%. With on-line standard addition calibration, relative error values went down to 2%. However, uncertainty values increased to 2% in all cases. With all the calibration methodologies, the accuracy and uncertainty of the obtained results were very similar for both standard and multiple sample introduction systems. The main difference was a significant reduction in resource consumption (i.e., samples, reagents and time) when multinebulization systems were used. Sensitivity, precision and limits of detection were evaluated for the different Flow Blurring®based systems and SSI system. For most of the emission lines evaluated, all the Flow Blurring®based systems gave higher precision values and lower limits of detection than SSI system. A certified reference material (Estuarine Water, LGC6016), without prior sample treatment (i.e., dilution), was analyzed using external calibration with the SSI system and on-line standard addition calibration with Flow Blurring®based systems. The certified reference material analysis gave relative error values ranging between % and −30% for the SSI system, and between % and −2% for Flow Blurring®based systems. [ABSTRACT FROM AUTHOR]

In this work, on-line calibration methods were applied for compensation for matrix effects in Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) using three novel multiple sample introduction systems based on Flow Blurring®technology. The methods were compared with conventional calibration methods, using a Conikal nebulizer and a cyclonic spray chamber (i.e., Standard Sample Introduction (SSI) system). Experiments were carried out with synthetic samples containing different matrices. The total liquid flow through the multinebulizers was 400 μL min−1whereas in the SSI system it was 1000 μL min−1. One type of calibration method tested was external calibration. By using this calibration method, the mean of absolute values corresponding to the relative error values of different multiple sample introduction systems and all the matrices was 14% and uncertainty was 0.6%. When on-line internal standard calibration was used, the mean relative error value dropped to 3% and uncertainty was 0.6%. With on-line standard addition calibration, relative error values went down to 2%. However, uncertainty values increased to 2% in all cases. With all the calibration methodologies, the accuracy and uncertainty of the obtained results were very similar for both standard and multiple sample introduction systems. The main difference was a significant reduction in resource consumption (i.e., samples, reagents and time) when multinebulization systems were used. Sensitivity, precision and limits of detection were evaluated for the different Flow Blurring®based systems and SSI system. For most of the emission lines evaluated, all the Flow Blurring®based systems gave higher precision values and lower limits of detection than SSI system. A certified reference material (Estuarine Water, LGC6016), without prior sample treatment (i.e., dilution), was analyzed using external calibration with the SSI system and on-line standard addition calibration with Flow Blurring®based systems. The certified reference material analysis gave relative error values ranging between +20% and −30% for the SSI system, and between +4% and −2% for Flow Blurring®based systems. [ABSTRACT FROM AUTHOR]

In this work, a new multiple nebulizer for liquid sample introduction in ICP-based spectrometers was developed and characterized on ICP-AES. The association of the Flow Focusing multiple nebulizer (FFMN) and a dedicated spray chamber was called Flow Focusing multi nebulization system (FFMNS). The nebulizer incorporates four nebulization nozzles with independent liquid feeding and a common gas inlet. Four different spray chambers were constructed and evaluated and the geometry of the best performing one was optimized. The FFNMS was characterized at 0.6–0.9 L min−1nebulizing gas flow and 0.04–0.6 mL min−1total liquid sample flow. Drop size and velocity distributions of primary and tertiary aerosols were studied together with total solvent and analyte transport rates. The system was characterized on ICP-AES in both axial and radial view modes and compared to a standard sample introduction system consisting in a concentric nebulizer and a cyclonyc spray chamber using model solutions and certified reference materials (CRM). In terms of sensitivity and LOD, the FFMNS showed a similar behavior to the reference system at half of the liquid sample uptake (0.5 mL min−1for FFMNS vs.1 mL min−1for the standard system). The CRM (hard drinking water) analysis recovery results are ranged between 89%–106% for FFMNS, and between 78%–102% for the reference system. Finally, the FFMNS was applied to an “in chamber” standard addition analysis of synthetic samples and CRM (estuarine water). The results of the CRM analysis showed better recoveries with respect to the external calibration for Cd, Mn and Ni, and similar results for Cu and Pb. [ABSTRACT FROM AUTHOR]