Development of a fluorimetric sequential injection analysis (SIA) methodology for determination of quinine

Abstract

Desenvolveu-se uma metodologia de análise por injeção sequencial (SIA) para a determinação fluorimétrica de quinino em refrigerantes. Dispersão mínima e mistura eficiente foram obtidas aspirando-se 200 mL de amostra entre duas zonas de 100 mL de reagente (0,10 mol L -1 H 2 SO 4 ) a uma vazão de 250 mL s -1 , usando uma bobina de reação de 50 cm de comprimento (0,8 mm de diâmetro interno). Resposta linear para concentrações (C) entre 0,050 e 100,0 mg L -1 foi descrita por: I = (532 ± 40) + (2,36 ± 0,04) C, com r = 0.999, onde I é intensidade relativa de fluorescência. Coeficiente de variação e limites de detecção e quantificação foram 1,9% (0,50 mg L -1 , n = 10), 2,3 e 4,5 mg L -1 , respectivamente. A frequência de amostragem foi 60 amostras por hora, consumindo 2,2 mL de H 2 SO 4 concentrado e produzindo 4 mL de resíduos por análise. Não foram observadas diferenças significativas entre os resultados obtidos pela metodologia SIA proposta e aqueles obtidos pelo procedimento em batelada.A sequential injection analysis (SIA) methodology was developed for fluorimetric determination of quinine in soft drinks. Minimum dispersion and efficient mixing were achieved by aspirating 200 mL of sample between two 100 mL reagent zones (0.10 mol L -1 H 2 SO 4 ) at flow rate of 250 mL s -1 and using a reaction coil length of 50 cm (0.8 mm internal diameter). Linear response for quinine concentrations (C) between 0.050 and 100.0 mg L -1 was described by: I = (532 ± 40) + (2.36 ± 0.04) C, with r = 0.999, where I is the relative fluorescence intensity. The coefficient of variation and limits of detection and quantification were 1.9% (0.50 mg L -1 n = 10), 2.3 and 4.5 mg L -1 , respectively. The sampling throughput was 60 analyses per hour, consuming 2.2 mL of concentrated H 2 SO 4 and producing 4 mL of wastes per analysis. No statistically significant differences were observed between the results obtained by the proposed SIA methodology and the ones obtained by the batch procedure.Keywords: sequential injection analysis, quinine, fluorimetry, dispersion, optimization IntroductionSequential injection analysis (SIA) is a robust single channel flow technique widely used to automate analytical determinations and process control. It is based on the measurement of a transient signal resulting from sequential injection of defined sample and reagent volumes in a carrier solution under controlled dispersion. 1 The sample processing conditions can be changed by software control as required by the analytical procedure. The possibility of exploiting feedback mechanisms to change sample processing conditions using a unique physical configuration make these approaches attractive to design flow procedures for process monitoring. 2,3 The characteristics of SIA enable automation of diverse operations such as sampling, chemical derivatization, dilution, standard addition and others, improving the reproducibility. Low sample and reagent consumption and small waste generation 4,5 are remarkable features of this technique, following the principles of g...

A Novel Equipment-Free Paper-Based Fluorometric Method for the Analytical Determination of Quinine in Soft Drink Samples

“…In terms of analytical chemistry, there have been developed many analytical methods for the determination of QN in several samples, including biochemical and food samples. These methods are mainly instrumental, including batch spectrometry [15], atomic absorption spectroscopy (AAS) [16], capillary electrophoresis [17,18], electrochemistry [19][20][21], flow injection analysis (FIA) [22,23], chemiluminescence [24][25][26], liquid chromatography [27][28][29][30], mass spectrometry [31], and fluorescence [32,33].…”

Multifunctional Portable System Based on Digital Images for In-Situ Detecting of Environmental and Food Samples

“…In addition, the variation in fluorescence intensity of quinine solutions increased with the decrease in the solution pH [ 15 , 48 ]. Therefore, pH 2 was chosen as the working pH for further works.…”

A study of the effect of organic solvents on the fluorescence signal in a sequential injection analysis system

“…As a naturally uorescent compound in acidic pH conditions, it is used as a standard to study the uorescence quantum yield under different conditions. 17,18 Methods based on SIA were reported for either determination of quinine 19 or using quinine as a sensitizer of photo-oxidation 20 or chemiluminescence 21 in determination of other substances.…”