RESUMEN
A new environmental friendly methodology based on fluorescent signal enhancement of rhodamine B dye is proposed for Pb(II) traces quantification using a preconcentration step based on the coacervation phenomenon. A cationic surfactant (cetyltrimethylammonium bromide, CTAB) and potassium iodine were chosen for this aim. The coacervate phase was collected on a filter paper disk and the solid surface fluorescence signal was determined in a spectrofluorometer. Experimental variables that influence on preconcentration step and fluorimetric sensitivity have been optimized using uni-variation assays. The calibration graph using zero th order regression was linear from 7.4×10(-4) to 3.4 µg L(-1) with a correlation coefficient of 0.999. Under the optimal conditions, a limit of detection of 2.2×10(-4) µg L(-1) and a limit of quantification of 7.4×10(-4) µg L(-1) were obtained. The method showed good sensitivity, adequate selectivity with good tolerance to foreign ions, and was applied to the determination of trace amounts of Pb(II) in refill solutions for e-cigarettes with satisfactory results validated by ICP-MS. The proposed method represents an innovative application of coacervation processes and of paper filters to solid surface fluorescence methodology.
Asunto(s)
Sistemas Electrónicos de Liberación de Nicotina , Plomo/análisis , Cetrimonio , Compuestos de Cetrimonio/química , Fluorescencia , Colorantes Fluorescentes/química , Yoduros/química , Plomo/química , Rodaminas/química , Tensoactivos/químicaRESUMEN
An on-line surfactant mediated extraction method in a flow injection analysis format with fluorescence detection was developed for the determination of Rhodamine B (RhB) in food condiments. The sample was extracted using the phase separation behavior exhibited by the bile salt surfactant, sodium cholate (NaC), upon addition of sodium dodecylsulfate (SDS) in the presence of acid at room temperature. The RhB in the sample was incorporated into the NaC/SDS coacervate phase which was then collected on a glass-wool packed mini column from which it was subsequently eluted using a 1.00 mol L(-1) HCl solution. The inherent fluorescence (λex=555 nm; λem=575 nm) of RhB was employed for detection. Good linearity (r(2)=0.9933) was obtained over the concentration range 0.4-4794-479.0 µg L(-1) RhB. The detection (LOD) and quantification (LOQ) limits were 0.12 and 0.40 µg L(-1), respectively. The method was successfully applied for analysis of RhB in food condiments and spiked samples. The average recoveries ranged from 95.3% to 118.9% at spiked concentration levels of 1.19 and 2.39 µg L(-1). Under optimized conditions, a throughput of 50 samples per hour was achieved. The proposed method may be a valuable tool not only for quality control of food condiments and similar food confectioneries but for the analysis of a variety of other RhB-containing samples as well.
Asunto(s)
Rodaminas/química , Colato de Sodio/química , Espectrometría de Fluorescencia/métodos , Tensoactivos/química , Calibración , Análisis de Inyección de Flujo/métodos , Fluorometría/métodos , Análisis de los Alimentos/métodos , Límite de Detección , Sistemas en Línea , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Dodecil Sulfato de Sodio/química , TemperaturaRESUMEN
Single-walled carbon nanotubes (SWNT) are proposed as chiral selectors for separation of carvedilol stereoisomers beginning since its racemic mixture. The novel developed FIA-methodology employs a microcolumn (mC) packed with a few milligrams of SWNT which showed to be effective in S(-) and R(+) carvedilol separation. Attending to spectral properties of analytes, molecular fluorescence was employed in the detection step. Separation of carvedilol enantiomers was achieved in less than 70s with an acceptable resolution factor of 3.16. Variables that influence the chiral separation such as pH and composition of eluent solution, sample injection volume and flow rate, activation mode of NTs and mass of the same in column have been examined in detail. At optimal operational conditions, well repeatability was achieved using the same column for more than 100 injections, putting in evidence the stability of nanomaterial and the efficacy and versatility of the proposed FIA-configuration. The new methodology was successfully applied to S(-) and R(+) carvedilol quantification in pharmaceutical preparations, resulting an attractive alternative to traditional separative methods being fast, simple, using low cost instrumentation and producing scarce waste.