Flow-Batch Analyzer for the Chemiluminescence Determination of Catecholamines in Pharmaceutical Preparations

A soft material for chromium speciation in water samples using a chemiluminescence automatic system

A soft material formed by multiwall carbon nanotubes and 1-butyl-3-methyl imidazolium chloride was used as sorbent material to perform the chromium speciation in natural waters. This soft material was not yet used for the speciation of metals as chromium. Thus, a multicommutated flow system containing a minicolumn packed with the soft material was designed. The procedure was based on the capacity of the sorbent to retain Cr(VI) as Cr₂O₇⁼ and allow to pass Cr(III) through the column. Then, a fully automated flow-batch analysis system was developed to quantify both species using chemiluminescence detection. Thus, Cr(III) was determined as catalyst of the luminol and hydrogen peroxide reaction and Cr(VI) as oxidant of luminol reaction. This represents a new approach because the oxidation of luminol using Cr₂O₇⁼ has not been reported in literature. The variables of the two systems were optimized. The limits of detection were 1.4 μg L^-1 for Cr(VI) and 4.0 μg L^-1 for Cr(III). The precision of the method was 3.8% and 7.0% for Cr(VI) and Cr(III), respectively. The present method was applied to real water samples with recoveries between 95% and 107%. Besides, these results were in accordance with those obtained using inductive coupled plasma-optical emission spectrometry technique.

Flow analysis with chemiluminescence detection: Recent advances and applications

This article highlights the most important developments in flow analysis with chemiluminescence (CL) detection, describing different flow systems that are compatible with CL detection, detector designs, commonly applied CL reactions and approaches to sample treatment. Recent applications of flow analysis with CL detection (focusing on outputs published since 2010) are also presented. Applications are classified by sample matrix, covering foods and beverages, environmental matrices, pharmaceuticals and biological fluids. Comprehensive tables are provided for each area, listing the specific sample matrix, CL reaction used, linear range, limit of detection and sample treatment for each analyte. Finally, recent and emerging trends in the field are also discussed.

Flow method based on cloud point extraction for fluorometric determination of epinephrine in human urine

A novel stepwise injection fluorometric method for the determination of epinephrine in human urine has been developed. In the current study, the stepwise injection analysis (SWIA) was successfully combined with on-line in-syringe cloud point extraction (CPE) and fluorometric detection. The procedure was based on the epinephrine derivatization in the presence of o-phenylenediamine followed by the preconcentration stage based on the CPE with the nonionic surfactant Triton X-114. After the phase separation into a syringe of the flow system, the micellar phase containing the epinephrine derivative was transported to a fluorometric detector. The excitation and emission wavelengths were set at 447 nm and 550 nm, respectively. The conditions of epinephrine derivatization and CPE have been studied. The calibration plot constructed using the developed procedure was linear in the range of 1·10(-11)-5·10(-7) mol L(-1). The limit of detection, calculated as 3 σ of a blank test (n = 10), was found to be 3·10(-12) mol L(-1). The proposed method was successfully applied for the determination of epinephrine in human urine samples.

Recent advances in flow injection analysis

A dynamic development of methodologies of analytical flow injection measurements during four decades since their invention has reinforced the solid position of flow analysis in the arsenal of techniques and instrumentation of contemporary chemical analysis.

Flow analysis in Brazil: contributions over the last four decades

Timeline with the main contributions of Brazilian researchers to flow analysis.

Investigation on the co-luminescence effect of europium (III)-lanthanum(III)-dopamine-sodium dodecylbenzene sulfonate system and its application

A novel luminescence, enhancement phenomenon in the europium(III)-dopamine-sodium dodecylbenzene sulfonate system was observed when lanthanum(III) was added. Based on this, a sensitive co-luminescence method was established for the determination of dopamine. The luminescence signal for the europium (III)-lanthanum(III)-dopamine-sodium dodecylbenzene sulfonate system was monitored at λ(ex) = 300 nm, λ(em) = 618 nm and pH 8.3. Under optimized conditions, the enhanced luminescence signal responded linearly to the concentration of dopamine in the range 1.0 × 10(-10)-5.0 × 10(-7) mol/L with a correlation coefficient of 0.9993 (n = 11). The detection limit (3σ) was 2.7 × 10(-11) mol/L and the relative standard deviation for 11 parallel measurements of 3.0 × 10(-8) mol/L dopamine was 1.9%. The presented method was successfully applied for the estimation of dopamine in samples of pharmaceutical preparations, human serum and urine. The possible luminescence enhancement mechanism of the system is discussed briefly.

Application of Sephadex LH-20 for Microdetermination of Dopamine by Solid Phase Spectrophotometry

A sensitive spectrophotometric method for the determination of dopamine was carried out without any separation steps. Bromocresol green is adsorbed on Sephadex LH-20 gel but the sorption decreases in the presence of dopamine due to ion-pair formation between bromocresol green and dopamine in solution. This attenuation was used to the microdetermination of dopamine by measurement of absorbance of the solid phase (Sephadex LH-20 gel) in a 1.0 mm cell at 625 nm. Dopamine could be determined in the concentration range of 0.4–1.6 μg mL⁻¹ (10-mL Sample volume) with a relative standard deviation (RSD) of 0.03% (n = 4). The detection limit was obtained, 0.26 μg mL⁻¹ (1.7 μM). The method was used for determination of dopamine in pharmaceutical injection sample and satisfactory result was obtained.

Automatic flow-batch system for cold vapor atomic absorption spectroscopy determination of mercury in honey from Argentina using online sample treatment

An automatic flow-batch system that includes two borosilicate glass chambers to perform sample digestion and cold vapor atomic absorption spectroscopy determination of mercury in honey samples was designed. The sample digestion was performed by using a low-cost halogen lamp to obtain the optimum temperature. Optimization of the digestion procedure was done using a Box-Behnken experimental design. A linear response was observed from 2.30 to 11.20 μg Hg L(-1). The relative standard deviation was 3.20% (n = 11, 6.81 μg Hg L(-1)), the sample throughput was 4 sample h(-1), and the detection limit was 0.68 μg Hg L(-1). The obtained results with the flow-batch method are in good agreement with those obtained with the reference method. The flow-batch system is simple, allows the use of both chambers simultaneously, is seen as a promising methodology for achieving green chemistry goals, and is a good proposal to improving the quality control of honey.