ABSTRACT
New and reliable methodologies are described for the determination of amino acids in gym supplements, offering rapid and clean analysis, with low generation of waste. The proposed methods are based on the reaction between ninhydrin and amino acids in acetate buffer medium (pH 4.75). Experimental design tools were used to optimize the analytical conditions. The linear range obtained for both methodologies was 20.0-350.0â¯mgâ¯L-1. The detection (LOD) and quantification (LOQ) limits were 6.2 and 21.0â¯mgâ¯L-1, respectively, for diffuse reflectance using a paper filter with hydrophobic barriers to increase the sensitivity and homogeneity of the colored product, and 5.7 and 18.8â¯mgâ¯L-1, respectively, for digital image analysis. A USB device was used in the diffuse reflectance spectroscopy method for heating the filter paper, providing speed and portability for the developed methodology. The methods showed good results when applied to gym supplement samples, with recoveries in the range 93.1-110%.
ABSTRACT
A multi-energy calibration method was applied for the determination of chromium and nickel in nickeliferous ores by laser-induced breakdown spectroscopy. For the optimization of the laser-induced breakdown spectroscopy parameters, such as laser fluence and delay time, an experimental study was conducted. The best results in terms of trueness were observed using a laser fluence and a delay time of 2500 J/cm2 and 1.1 µs, respectively. A study of sample matrix effects and the determination of emission lines for calibration and normalization of the spectra were undertaken, and appropriate values of those variables were selected for each analyte. The trueness values for chromium and nickel varied from 89 to 114% when certified reference samples (nickeliferous laterite, rock phosphate and contaminated soil) were analyzed.
ABSTRACT
A sensitive, rapid and robust method based on the use of stabilizer-free silver nanoparticles was developed for lead detection in honey. Silver nanoparticles were synthesized without the presence of any stabilizers using silver nitrate and sodium borohydride as precursors where the latter was applied as reducing agent. The optimization of the experimental variables (AgNO3 and NaBH4) for the formation of the nanoparticles was carried out using varying volumes of these solutions. Spectrophotometric measurements at 393nm showed a linear working range between 0.0500 and 0.167mgL-1 lead (R=0.994), with limits of detection (LOD) and quantification (LOQ) of 0.0135 and 0.0451mgL-1, respectively. The proposed method proved to be a significantly sensitive mechanism for lead detection in honey samples.
Subject(s)
Honey/analysis , Lead/analysis , Metal Nanoparticles/chemistry , Silver/chemistry , Color , Flowers/chemistry , Hydrogen-Ion Concentration , Limit of Detection , Metal Nanoparticles/ultrastructure , Osmolar ConcentrationABSTRACT
A rapid and simple screening method was developed for the determination of sulfonamides in honey samples by flow injection analysis (FIA) coupled to a liquid waveguide capillary cell. The proposed method is based on the reaction between sulfonamides and p-dimethylaminocinnamaldehyde (p-DAC) in the presence of sodium dodecylsulate (SDS) in dilute acid medium (hydrochloric acid), with the reaction product being measured spectrophotometrically at λ(max) = 565 nm. Experimental design methodology was used to optimize the analytical conditions. The proposed technique was applied to the determination of sulfonamides (sulfaquinoxaline, sulfadimethoxine, and sulfathiazole) in honey samples, in a concentration range from 6.00 × 10(-3) to 1.15 × 10(-1)mg L(-1). The detection (LOD) and quantification (LOQ) limits were 1.66 × 10(-3) and 5.54 × 10(-3)mg L(-1), respectively. Positive and false positive samples were also analyzed by a confirmatory HPLC method. The proposed system enables the screening of sulfonamides in honey samples with a low number of false positive results, with fast response therefore offers a new tool for consumer protection.
