RESUMEN

This study introduces a feasible approach for utilizing a conventional High-Performance Liquid Chromatography (HPLC) instrument at the capillary scale (1 - 10 µL/min). The development of an active flow splitter and an adapted UV-visible (UV-vis) detection cell are described. The system employs an Arduino Uno board to monitor a flow sensor and control a stepper motor that automates a split valve to achieve capillary-scale flow rates from a conventional pump. A capillary UV-vis cell compatible with conventional detectors, featuring an optical path length with a volume of 14 nL, was developed to address the detection challenges at this scale and minimize extra column band broadening. The system performance was assessed by a lab-packed LC capillary column with 0.25 mm x 15 cm dimensions packed with 3.0 µm C18 particles. Model compounds, particularly polycyclic aromatic hydrocarbons (PAHs), were employed to assess the functionality of all developed components in terms of theoretical plates, resolution, and band broadening. The proposed system is a profitable, reliable, and cost-effective tool for miniaturized liquid chromatography.

Asunto(s)

Hidrocarburos Policíclicos Aromáticos , Cromatografía Líquida de Alta Presión/métodos , Hidrocarburos Policíclicos Aromáticos/análisis , Diseño de Equipo , Espectrofotometría Ultravioleta

RESUMEN

The present work exhibits the dynamic viscosity profile data of three distinct nanofluids, at a constant shear stress, and within a range of temperatures that include below-ambient conditions (from -10 to 20 °C). The nanofluids were as follows. Nanofluid I: 30% ethylene glycol and 70% distilled water (v/v), with graphene (0.32% in mass); Nanofluid II: 30% engine coolant NBR 13705; ASTM D-3306; ASTM D-4985) and 70% distilled water (v/v), with graphene (0.2% in mass); and Nanofluid III: 30% engine coolant and 70% distilled water (v/v), with Multi-Walled Carbon Nanotubes (MWCNT) (0.2% in mass). The present work was motivated by the scarcity of experimental data on the temperature dependence of viscosity for graphene, MWCNT, and their hybrid nanofluids, at below-ambient temperatures.