Microcystin-LR detection in water by the Fabry–Pérot interferometer using an optical fibre coated with a sol–gel imprinted sensing membrane

Cyanobacteria deteriorate the water quality and are responsible for emerging outbreaks and epidemics causing harmful diseases in Humans and animals because of their toxins. Microcystin-LR (MCT) is one of the most relevant cyanotoxin, being the most widely studied hepatotoxin. For safety purposes, the World Health Organization recommends a maximum value of 1 μg L−1 of MCT in drinking water. Therefore, there is a great demand for remote and real-time sensing techniques to detect and quantify MCT. In this work a Fabry–Pérot sensing probe based on an optical fibre tip coated with a MCT selective thin film is presented. The membranes were developed by imprinting MCT in a sol–gel matrix that was applied over the tip of the fibre by dip coating. The imprinting effect was obtained by curing the sol–gel membrane, prepared with (3-aminopropyl) trimethoxysilane (APTMS), diphenyl-dimethoxysilane (DPDMS), tetraethoxysilane (TEOS), in the presence of MCT. The imprinting effect was tested by preparing a similar membrane without template. In general, the fibre Fabry–Pérot with a Molecular Imprinted Polymer (MIP) sensor showed low thermal effect, thus avoiding the need of temperature control in field applications. It presented a linear response to MCT concentration within 0.3–1.4 μg L−1 with a sensitivity of −12.4 ± 0.7 nm L μg−1. The corresponding Non-Imprinted Polymer (NIP) displayed linear behaviour for the same MCT concentration range, but with much less sensitivity, of −5.9 ± 0.2 nm L μg−1. The method shows excellent selectivity for MCT against other species co-existing with the analyte in environmental waters. It was successfully applied to the determination of MCT in contaminated samples. The main advantages of the proposed optical sensor include high sensitivity and specificity, low-cost, robustness, easy preparation and preservation.

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Carta Pastoral del I. y R.S. Obispo de Querétaro, publicando la de los II. y RR. Sres. Arzobispos de la nación, en que insertan el breve pontificio disponiendo la coronación de la maravillosa imagen de Ntra. Sra. de Guadalupe, y reglamentando la colecta que debe hacerse en la Diócesis con este objeto.

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Reflexiones critico-apologeticas sobre las obras del RR. P. maestro Fr. Benito Geronymo Feyjoo : en defensa de las milagrosas flores de S. Luis del Monte, de la constante pureza de fé admirable sabiduría,i utilissima doctrina de el iluminado doctor, i esclarecido martyr, B. Raimundo Lulio : de la gran erudición, i sólido juicio del clarissimo doctor el V. Fr. Nicolao de Lyra : de la famosa literatura, i constante veracidad historica de el Ilmo. , i V. D. Fr. Antonio de Guevara, i de otros clarissimos ingenios, que ilustraron al orbe literario

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