In this study, xiquexique (Pilosocereus gounellei) native endemic cactus from the Brazilian semiarid was used for the first time as a natural carbon source (“green precursor”) for the synthesis of highly fluorescent carbon dots (CDs). These CDs were successfully used to develop a fast, low-cost, eco-friendly fluorescence method for the determination of tannins in teas. This method was automatized employing a flow-batch system coupled to an inexpensive ultraviolet light-emitting diode (UV-LED) used as an excitation source and a cheap handheld spectrometer used as a detector. CDs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis, and fluorescence spectroscopy. The proposed method presented a linear range from 2.0-30.0 mg L-1, relative standard deviation (RSD) < 3.0%, limit of detection (LOD) = 0.102 mg L-1, and recovery rates from 90.5-109.1%. A paired t-test at a 95% confidence level indicated no statistically significant difference between the proposed and reference methods, revealing that it is a useful alternative for the determination of tannins. study Pilosocereus gounellei green precursor precursor” CDs. . (CDs) fast lowcost, lowcost low cost, cost low-cost ecofriendly eco friendly teas flowbatch flow batch lightemitting light emitting UVLED UV LED (UV-LED detector TEM, TEM , (TEM) Xray X ray XRD, XRD (XRD) FTIR, FTIR (FTIR) UVVis, UVVis Vis, Vis UV-Vis 2.030.0 20300 2.0 30.0 2 0 30 2.0-30. L1, L1 L 1, 1 L-1 RSD (RSD 3 3.0% LOD (LOD 0102 102 0.10 90.5109.1%. 9051091 90.5 109.1%. 90 5 109 90.5-109.1% ttest t test 95 methods (CDs (TEM (XRD (FTIR 030 2.030. 2030 20 2. 300 30. 2.0-30 L- 3.0 010 10 0.1 5109 90.5109.1% 905109 905 90. 1091 109.1% 9 90.5-109.1 03 2.030 203 2.0-3 3. 01 0. 510 90.5109.1 90510 109.1 90.5-109. 2.03 2.0- 51 90.5109. 9051 109. 90.5-109 90.5109 90.5-10 90.510 90.5-1 90.51 90.5-

An automated microsystem for sulfite determination in beverages was developed. It presents higher sampling throughput, lower chemical consumption and less waste generation than previous flow methods, while using the same p-rosaniline-formaldehyde-sulfite reaction. The sampling rate, limit of detection (LOD), and relative standard deviation (RSD) were estimated at 130 h-1, 80.0 µg L–1, and < 1.3% (n = 5), respectively. Recoveries ranged from 96.8 to 102.6%.

Neste trabalho é proposto um analisador micro-flow-batch (µFBA) usando uma webcam para determinação espectrofotométrica de ortofosfato e alumínio(III) em água de torneira. Este microssistema foi feito com uretana-acrilato e lâminas de vidro. As determinações de PO4(3-) e Al3+ foram realizadas empregando os métodos do azul de molibdênio e quercertina, respectivamente. Para a construção de curvas analíticas lineares um modelo matemático foi usado com base nos valores RGB (vermelho, verde e azul). As faixas de trabalho foram de 25 a 500 µg L-1 para ambos os analitos com limites de detecção, desvio padrão relativo (RSD, n = 5) e frequência analítica de 0,82 µg L-1, < 0,8% e 160 h-1 para PO4(3-), e 0,93 µg L-1, < 1,1% e 160 h-1 para Al(III). Comparando com os métodos de referência, diferenças estatisticamente significativas não foram observadas quando aplicado o teste-t pareado com 95% de confiança. O teste de recuperação apresentou resultados entre 98,1 e 102,8%. O µFBA proposto apresentou portabilidade satisfatória, robustez, flexibilidade e reduzido consumo de reagentes.

In this work, a micro-flow-batch analyzer (µFBA) using webcam for spectrophotometric determination of ortho-phosphate and aluminium(III) in tap water is proposed. PO4(3-) and Al3+ determinations were performed by employing molybdenum blue and quecertin methods, respectively. In order to build linear analytical curves, a mathematical model was used on the basis of the RGB (red, green and blue) values. Working ranges were from 25 to 500 µg L-1 for both analytes with estimated limits of detection, relative standard deviation (RSD, n = 5) and sampling rate of 0.82 µg L-1, < 0.8% and 160 h-1 for PO4(3-), and 0.93 µg L-1, < 1.1% and 160 h-1 for Al(III). Comparing with the reference methods, no statistically significant differences were observed when applying the paired t-test at a 95% confidence level. Recovery study shows results between 98.1 and 102.8%. The proposed µFBA presented satisfactory portability, robustness, flexibility, low-cost device and reduced chemicals consumption.