THIRD ORDER MULTIVARIATE CALIBRATION APPLIED TO THE QUANTITATION OF AZINPHOS-METHYL IN FRUITS BY EXCITATION-EMISSION-KINETIC MEASUREMENTS

MONTEMURRO, MILAGROS; SIANO, GABRIEL; CULZONI, MARIA J.; GOICOECHEA, HÉCTOR C.

Congreso; XVI Chemometrics in Analytical Chemistry; 2016

p { margin-bottom: 0.25cm; line-height: 120%; }Azinphos-methyl(AZM) is a widely used organophosphate insecticide and acaricide,with demonstrated negative impacts on the environment [1]. The weaknatural fluorescence of AZM in aqueous solution can be enhanced in avariety of ways, including UV photolysis, inclusion intocyclodextrins, and base hydrolysis. Upon absorption of UV-Aradiation, this molecule undergoes photolysis to the highlyfluorescent compound N-methylanthranilic acid, which undergoessubsequent photolysis to photochemically stable products [2].Four-way datagenerated by excitation-emission fluorescence matrices (EEFMs)measured as a function of reaction time can be modelled withappropriate higher order algorithms to achieve the second orderadvantage and improve both the selectivity and sensibility of themethod. In this work, we developed a fluorescent kinetic method forthe determination of AZM in fruit samples. It is based onthird-order data, obtained by measuring the time evolution of theEEFMs of the photolysisof AZM in alkalinemedium.The experiments werecarried out with an instrument consisting in an optic fiber connectedto an UV radiation source, coupled to a fluorescencespectrophotometer. The matrices were recorded in a quartz cell of 1cm of path length. The readings were made in the excitation range of220 to 320 nm every 5 nm, and emission from 320 to 500 nm every 5 nmat a scan rate of 24,000 nm min-1. EEFMs were measuredevery 30 seconds for six minutes, thus having 21 × 33 × 13 datapoints.Calibration andvalidation sets, consisting in five concentration levels of AZM each,were analyzed. The validation samples were prepared by addingfuberidazole, bitertanol and thiabendazole as uncalibratedinterferences. Data modelling was performed with the algorithmsMCR-ALS, PARAFAC and U-PLS/RTL. Relative error prediction andanalytical figures of merit were calculated. The results obtainedwere similar for the three algorithms.The method wasfurther used for the quantitation of AZM in apple, pear, peach andplum. For thispurpose, thestandard addition calibration method was used in order to overcomematrix effect, which involved spiking three levels of AZM standardto the real samples. The sample preparation procedure consisted inan extraction with acetonitrile followed by dispersive liquid-liquidmicroextraction. Recoveries and figures of merit were alsocalculated for real samples