FTIR spectroscopy with chemometrics for determination of tylosin residues in milk.

BACKGROUND: Contamination of milk by antibiotic residues represents risks to the health of consumers; therefore they should be monitored. The objective of this study was to propose a methodology for the determination of tylosin residues directly in fluid milk based on mid-infrared spectroscopy associated with chemometrics, using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy associated with multilayer perceptron network (MLP) and partial least squares (PLS). RESULTS: MLP was shown to be adequate for the discrimination of milk samples contaminated with tylosin below or equal to or above the maximum residue limit (MRL), with an accuracy greater than 99%, using FTIR spectra data. PLS was shown to be appropriate for the prediction of the very low concentrations (0-100 µg L-1 ) of tylosin residues in milk using FTIR spectra data. PLS models with high correlation coefficients (R > 0.99) were generated. CONCLUSION: FTIR with chemometrics proved to be a non-destructive, efficient and low-cost method for the investigation and quantification of tylosin residues directly in fluid milk. © 2020 Society of Chemical Industry.

Simultaneous determination of cadmium, iron and tin in canned foods using high-resolution continuum source graphite furnace atomic absorption spectrometry.

A method was established to simultaneously determine cadmium, iron and tin in canned-food samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The quantification step has been performed using the primary line (228.802nm) for cadmium and the adjacent secondary lines (228.725nm and 228.668nm) for iron and tin, respectively. The selected chemical modifier was an acid solution that contained a mixture of 0.1% (w/v) Pd and 0.05% (w/v) Mg. The absorbance signals were measured based on the peak area using 3 pixels for cadmium and 5 pixels for iron and tin. Under these conditions, cadmium, iron and tin have been determined in canned-food samples using the external calibration technique based on aqueous standards, where the limits of quantification were 2.10ngg(-1) for cadmium, 1.95mgkg(-1) for iron and 3.00mgkg(-1) for tin, and the characteristic masses were 1.0pg for cadmium, 0.9ng for iron and 1.1ng for tin. The precision was evaluated using two solutions of each metal ion, and the results, which were expressed as the relative standard deviation (RSD%), were 3.4-6.8%. The method accuracy for cadmium and iron was confirmed by analyzing a certified reference material of apple leaves (NIST 1515), which was supplied by NIST. However, for tin, the accuracy was confirmed by comparing the results of the proposed method and another analytical technique (inductively coupled plasma optical emission spectrometry). The proposed procedure was applied to determine cadmium, iron and tin in canned samples of peeled tomato and sardine. Eleven samples were analyzed, and the analyte concentrations were 3.57-62.9ngg(-1), 2.68-31.48mgkg(-1) and 4.06-122.0mgkg(-1) for cadmium, iron and tin, respectively. In all analyzed samples, the cadmium and tin contents were lower than the permissible maximum levels for these metals in canned foods in the Brazilian legislation.

Determination of copper in airborne particulate matter using slurry sampling and chemical vapor generation atomic absorption spectrometry.

The present paper describes the development of a method for the determination of copper in airborne particulate matter using slurry sampling and chemical vapor generation atomic absorption spectrometry (CVG AAS). Chemometric tools were employed to characterize the influence of several factors on the generation of volatile copper species. First, a two-level full factorial design was performed that included the following chemical variables: hydrochloric acid concentration, tetrahydroborate concentration, sulfanilamide concentration and tetrahydroborate volume, using absorbance as the response. Under the established experimental conditions, the hydrochloric acid concentration had the greatest influence on the generation of volatile copper species. Subsequently, a Box-Behnken design was performed to determine the optimum conditions for these parameters. A second chemometric study employing a two-level full factorial design was performed to evaluate the following physical factors: tetrahydroborate flow rate, flame composition, alcohol volume and sample volume. The results of this study demonstrated that the tetrahydroborate flow rate was critical for the process. The chemometric experiments determined the following experimental conditions for the method: hydrochloric acid concentration, 0.208 M; tetrahydroborate concentration, 4.59%; sulfanilamide concentration, 0.79%; tetrahydroborate volume, 2.50 mL; tetrahydroborate flow rate, 6.50 mL min(-1); alcohol volume, 200 µL; and sample volume, 7.0 mL. Thus, this method, using a slurry volume of 500 µL and a final dilution of 7 mL, allowed for the determination of copper with limits of detection and quantification of 0.30 and 0.99 µg L(-1), respectively. Precisions, expressed as RSD%, of 4.6 and 2.8% were obtained using copper solutions at concentrations of 5.0 and 50.0 µg L(-1), respectively. The accuracy was evaluated by the analysis of a certified reference material of urban particulate matter. The copper concentration obtained was 570±63 mg kg(-1), and the certified value was 610±70 mg kg(-1). This method was applied for the determination of copper in airborne particulate matter samples collected in two Brazilian regions of Bahia State, Brazil. The copper contents found varied from 14.46 to 164.31 ng m(-3).

Analytical strategies for determination of cadmium in Brazilian vinegar samples using ET AAS.

This paper proposes two methods for determination of cadmium in vinegar employing electrothermal atomic absorption spectrometry. The optimization step was performed using two-level full factorial and Box-Behnken designs, being that a new multiple response function was established. Under experimental conditions of pyrolysis temperature of 640 °C and atomization temperature of 2000 °C, the direct method allows the analysis using the external calibration technique, with limit of quantification of 14 ng L(-1) and characteristic mass of 1.2 pg, having aluminium as chemical modifier. This method was applied in six samples of vinegar acquired from Salvador City, Brazil. The cadmium content varied from 20 to 890 ng L(-1). Other method was also proposed by digestion using nitric acid and hydrogen peroxide in reflux system employing cold finger, being cadmium determined by ETAAS. The results obtained with the complete digestion procedure were in agreement with those found by the direct method proposed herein.