Pablo Garrido González

Pulsed flows in flow analysis: Potentialities, limitations and applications.

In flow analysis, use of a steady and pulseless flow was considered essential for ensuring a reproducible handling of the flowing sample. To this end, peristaltic and syringe pumps have been the propelling device in the vast majority of the flow analysers. Recently, the number of applications involving pulsed flow has been increasing. Most of them refer to use of solenoid pumps, the essence of the so-called multi-pumping flow systems. This review critically discusses the characteristics, potentialities and limitations of the pulsed flow systems, emphasizing the main advantageous characteristics of the streams involved, such as high radial mass transference and good mixing of the fluids. Diverse contributions ranging from instrumentation development to analytical applications are presented.

Las piedras de la memoria (II): El uso en época romana de espacios y monumentos sagrados prehistóricos del Sur de la Península Ibérica

This paper tackles the analysis of a series of cases of reutilisation in Roman times of prehistoric sacred spaces and monuments, recorded throughout the South of the Iberian Peninsula. The cases under study are grouped in three main categories: (i) spatial proximity or overlapping of prehistoric and Roman burial areas, (ii) reutilisation of the inner and outer spaces of prehistoric mortuary chambers, and (iii) re-use of rock art sanctuaries and prehistoric stelae. As a conclusion, we suggest, firstly, the need to reconsider the recording criteria by which the appearance of later materials in old monuments is archaeologically assessed; secondly, we point out the need to look at these cases from the viewpoint of the elements of tradition and memory that some old sacred sites convey for the Iberian-Roman populations. Finally, we suggest these cases must be interpreted in terms of religious and political ideology.

LOW COST ANALYZER FOR THE DETERMINATION OF PHOSPHORUS BASED ON OPEN-SOURCE HARDWARE AND PULSED FLOWS

The need for automated analyzers for industrial and environmental samples has triggered the research for new and cost-effective strategies of automation and control of analytical systems. The widespread availability of open-source hardware together with novel analytical methods based on pulsed flows have opened the possibility of implementing standalone automated analytical systems at low cost. Among the areas that can benefit from this approach are the analysis of industrial products and effluents and environmental analysis. In this work, a multi-pumping flow system is proposed for the determination of phosphorus in effluents and polluted water samples. The system employs photometric detection based on the formation of molybdovanadophosphoric acid, and the fluidic circuit is built using three solenoid micropumps. The detection is implemented with a low cost LED-photodiode photometric detection system and the whole system is controlled by an open-source Arduino Uno microcontroller board. The optimization of the timing to ensure the color development and the pumping cycle is discussed for the proposed implementation. Experimental results to evaluate the system behavior are presented verifying a linear relationship between the relative absorbance and the phosphorus concentrations for levels as high as 50 mg L-1.

Multi-pumping flow system for the determination of boron in eye drops, drinking water and ocean water ☆

A novel automated method for the determination of boron based on the use of pulsed flows was developed and applied to the determination of this element in samples of tap water, ocean water and eye drops. The method was implemented by means of a multi-pumping system consisting of three solenoid micropumps and a photometric detector and exploits the reaction of azomethine-H in the presence of boron. The system runs under control of an open-source microcontroller. The main operational parameters were optimized. Given the particular kinetics of the reaction, a stopped-flow period (1 or 5min) was included to allow for color development. The method presents linearity in the range 0.35-3.0mgL-1, good precision (sr<3%), and detection and quantification limits of 0.10 and 0.35mgL-1 respectively. Samples of tap water or eye drops could be successfully analyzed employing a 1-minute stop time, providing a maximum sampling frequency of 32 samples h-1. In order to overcome matrix effect caused by the high saline concentration, ocean water samples required stop times of 5min, providing a sampling frequency of 10 samples h-1. Recoveries of 102% (eye drops), 94% (drinking water) and 93% (ocean water) were obtained. The method was considered accurate and fit for the purpose.