Estequiometría del complejo Carmín-Boro

Tres métodos establecen la naturaleza del complejo Carmín-Boro en solución. Estos eran el método de variaciones continuas de Job y modificado por Vosburgh y Cooper , el método de relación molar propuesto por Yoe y Jones , y finalmente el método proporción de pendiente de Harvey y Manning modificado por Venkateswarlu y Raghava Rao.Los resultados obtenidos por los tres métodos indican que la fórmula empírica del complejo de boro es de dos átomos de boro a una molécula del reactivo.The nature of the boron-carmine complex in solution is established by three methods. These were the method of continuous variations by Job and modified by Vosburgh and Cooper, the mole ratio method proposed by Yoe and Jones, and the slope ratio method of Harvey and Manning and modified by Venkateswarlu and Raghava Rao. The results obtained by the three methods indicate that the empirical formula of the boron complex is two atoms of boron to one molecule of the reagent.Cátedra de Química Analítica de la Facultad de Ciencias y Estación Experimental del Zaidín del CSIC (Prof. Dr. F. Capitán

Aplicaciones analíticas de la Guanidiltiourea. III. Determinación volumétrica de Ni y Co

En el presente trabajo se propone un nuevo método volumétrico para la determinación de Ni, basado en el empleo de la guanidiltiourea (tiodiciandiamidina) como agente reactivo. Los resultados que se obtienen son correctos, siendo ± 0,0004 el valor de la desviación típica y ± 0,23 % el del error relativo sobre el valor medio. El método consiste, en esencia, en precipitar en Ni mediante guanidiltiourea, disolver el precipitado en un exceso de CIH y valorar este exceso con NaOH en presencia de rojo de metilo como indicador. El método se aplica, asimismo, a la determinación de Co y la de Ni en presencia de Co.In this work has proposed a new volumetric method for determining of Ni , it is based in the use of the guanidilthiourea (tiodiciandiamidina ) as reactive agent . The results obtained are correct, the value being 0.0004 ± standard deviation and ± 0.23% in the relative error of the mean. The method consists essentially in precipitating Ni by guanidiltiourea, dissolving the precipitate in an excess of CIH and value this excess with NaOH in the presence of methyl red as indicator. The method also applies to the determination of Co and Ni in the presence of Co.Cátedra de Química Analitica de la Facultad de Ciencias de la Universidad de Granada y Sección de Química Analítica del CSIC

SARS-CoV-2 viral RNA detection using the novel CoVradar device associated with the CoVreader smartphone app

Supplementary data to this article can be found online at https://doi. org/10.1016/j.bios.2023.115268The COVID-19 pandemic has highlighted the need for innovative approaches to its diagnosis. Here we present CoVradar, a novel and simple colorimetric method that combines nucleic acid analysis with dynamic chemical labeling (DCL) technology and the Spin-Tube device to detect SARS-CoV-2 RNA in saliva samples. The assay includes a fragmentation step to increase the number of RNA templates for analysis, using abasic peptide nucleic acid probes (DGL probes) immobilized to nylon membranes in a specific dot pattern to capture RNA fragments. Duplexes are formed by labeling complementary RNA fragments with biotinylated SMART bases, which act as templates for DCL. Signals are generated by recognizing biotin with streptavidin alkaline phosphatase and incubating with a chromogenic substrate to produce a blue precipitate. CoVradar results are analysed by CoVreader, a smartphone-based image processing system that can display and interpret the blotch pattern. CoVradar and CoVreader provide a unique molecular assay capable of detecting SARS-CoV-2 viral RNA without the need for extraction, preamplification, or pre-labeling steps, offering advantages in terms of time (similar to 3 h/test), cost (similar to epsilon 1/test manufacturing cost) and simplicity (does not require large equipment). This solution is also promising for developing assays for other infectious diseases.FEDER/Junta de Andalucia-Consejeria de Economia y Conocimiento CV20-77741, A-FQM-760-UGR20, PID 2019-110987RB-I00, PID 2019-103938RB-I00Spanish MCIN/AEI P18-RT-2961, P18-TP-4160FEDER/Junta de Andalucia-Consejeria de Salud y Familias PIP-0232-2021European CommissionMCIN/AEI PTQ 2020-011388, IJC 2020-043307-IEuropean Union NextGenerationEU/PRTR PTQ 2020-011388, IJC 2020-043307-

Portable Instrument for Hemoglobin Determination Using Room-Temperature Phosphorescent Carbon Dots

A portable reconfigurable platform for hemoglobin determination based on inner filter quenching of room-temperature phosphorescent carbon dots (CDs) in the presence of H2O2 is described. The electronic setup consists of a light-emitting diode (LED) as the carbon dot optical exciter and a photodiode as a light-to-current converter integrated in the same instrument. The reconfigurable feature provides adaptability to use the platform as an analytical probe for CDs coming from different batches with some variations in luminescence characteristics. The variables of the reaction were optimized, such as pH, concentration of reagents, and response time; as well as the variables of the portable device, such as LED voltage, photodiode sensitivity, and adjustment of the measuring range by a reconfigurable electronic system. The portable device allowed the determination of hemoglobin with good sensitivity, with a detection limit of 6.2 nM and range up to 125 nM.MINECO (Spain) CTQ2016-78754-C2-1-REuropean Union (EU

Capacitive platform for real-time wireless monitoring of liquid wicking in a paper strip

Understanding the phenomenon of liquid wicking in porous media is crucial for various applications, including the transportation of fluids in soils, the absorption of liquids in textiles and paper, and the development of new and efficient microfluidic paper-based analytical devices (μPADs). Hence, accurate and real-time monitoring of the liquid wicking process is essential to enable precise flow transport and control in microfluidic devices, thus enhancing their performance and usefulness. However, most existing flow monitoring strategies require external instrumentation, are generally bulky and unsuitable for portable systems. In this work, we present a portable, compact, and cost-effective electronic platform for real-time and wireless flow monitoring of liquid wicking in paper strips. The developed microcontroller-based system enables flow and flow rate monitoring based on the capacitance measurement of a pair of electrodes patterned beneath the paper strip along the liquid path, with an accuracy of 4 fF and a full-scale range of 8 pF. Additionally to the wired transmission of the monitored data to a computer via USB, the liquid wicking process can be followed in real-time via Bluetooth using a custom-developed smartphone application. The performance of the capacitive monitoring platform was evaluated for different aqueous solutions (purified water and 1 M NaCl solution), various paper strip geometries, and several custom-made chemical valves for flow retention (chitosan-, wax-, and sucrose-based barriers). The experimental validation delivered a full-scale relative error of 0.25%, resulting in an absolute capacitance error of ±10 fF. In terms of reproducibility, the maximum uncertainty was below 10 nl s−1 for flow rate determination in this study. Furthermore, the experimental data was compared and validated with numerical analysis through electrical and flow dynamics simulations in porous media, providing crucial information on the wicking process, its physical parameters, and liquid flow dynamics

In situ synthesis of fluorescent silicon nanodots for determination of total carbohydrates in a paper microfluidic device combined with laser prepared graphene heater

We report a simple, rapid, low-resource and one-step method for formation of fluorescent silicon nanodots (SNDs) in a microfluidic paper-based analytical device (μPAD) incorporated in a reusable, portable and flexible heater for determination of total carbohydrates. The synthesis of SNDs is based on the redox reaction between (3-aminopropyl) triethoxysilane (APTS) reagent and carbohydrates, which act as a reducer. The graphene-based heater was fabricated by laser ablation of Kapton polyimide. Thereby, the developed system heat the μPAD during the synthesis of SNDs at 80 °C for 30 min. The blue emitting SNDs formed have an emission peak wavelength at 475 nm. We used a digital camera and smartphone for the quantitative analysis of total carbohydrates expressed such as index of glucose or fructose with grey scale value as the analytical parameter. Under the optimal conditions, the method has a low detection limit (0.80 μM for glucose and 0.51 μM for fructose, respectively), and a linear response (10–200 μM for glucose and 10–100 μM for fructose). The method has been applied to the determination of glucose in biological fluids (serum and urine samples). In addition, determination of total carbohydrates in commercial juices and teas have been carried outThis work was founded by Spanish “Ministerio de Economía y Competitividad” (Projects PID2019-103938RB-I00 and CTQ2017-86125-P) and Junta de Andalucía (Projects B-FQM-243-UGR18 and P18-RT-2961). The projects were partially supported by European Regional Development Funds (ERDF)

QRsens: Dual-purpose quick response code with built-in colorimetric sensors

Supplementary data associated with this article can be found in the online version at doi:10.1016/j.snb.2022.133001.QRsens represents a family of Quick Response (QR) sensing codes for in-situ air analysis with a customized smartphone application to simultaneously read the QR code and the colorimetric sensors. Five colorimetric sensors (temperature, relative humidity (RH), and three gas sensors (CO2, NH3 and H2S)) were designed with the aim of proposing two end-use applications for ambient analysis, i.e., enclosed spaces monitoring, and smart packaging. Both QR code and colorimetric sensing inks were deposited by standard screen printing on white paper. To ensure minimal ambient light dependence of QRsens during the real-time analysis, the smartphone application was programmed for an effective colour correction procedure based on black and white references for three standard illumination temperatures (3000, 4000 and 5000 K). Depending on the type of sensor being analysed, this integration achieved a reduction of ~71 – 87% of QRsens’s dependence on the light temperature. After the illumination colour correction, colorimetric gas sensors exhibited a detection range of 0.7–4.1%, 0.7–7.5 ppm, and 0.13–0.7 ppm for CO2, NH3 and H2S, respectively. In summary, the study presents an affordable built-in multi-sensing platform in the form of QRsens for in-situ monitoring with potential in different types of ambient air analysis applications.Spanish MCIN/AEI/10.13039/ 501100011033/ (Projects PID2019–103938RB-I00, ECQ2018–004937- P and grant IJC2020–043307-I)Junta de Andalucía (Projects B- FQM-243-UGR18, P18-RT-2961)European Regional Development Funds (ERDF)European Union NextGenerationEU/PRT

Identificación de paladio utilizando como reactivo sal nitroso-R. Estequiometria del complejo

Se propone como reactivo para la identificación de paladio la sal nitroso- R. Se estudian diversos factores que pueden afectarla, tales como la acción de distintos ácidos y el orden de adición de los reactivos, así como el efecto de 15 iones extraños. La sensibilidad de la reacción es muy elevada (1: 5x10 elevado a 6). La estequiometría del complejo,determinada por diversos métodos, es 1 Pd: 2 sal nitroso-R.The nitroso-R-salt as a reagent for the detection of palladium is proposed. The study of the effect of differents acids, order of addition of reagents and 15 extraneous ions is made.The reaction's sensitivity is very high (1:5x10high6).The empirical formula of the formed complex in solution is determined.Cátedra de Química Analítica de la Facultad de Ciencias (Prof. Dr. F. Capitán García) y Estación Experimental del Zaidín del CSIC (Granada)