Calibration in process monitoring by using unsegmented continuous-flow systems

An overview is presented of the different aspects of the role of analytical chemistry in process monitoring and control. On-line monitoring is currently the most attractive option in this area, especially with unsegmented-flow techniques. In addition to allowing automation of these systems, the variety of ways in which calibration and recalibration can be performed allows their adaptation to any situation by using extremely simple, home-made manifolds. The most relevant designs are presented and critically discussed in this paper

Non-critically squeezed light via spontaneous rotational symmetry breaking

We theoretically address squeezed light generation through the spontaneous breaking of the rotational invariance occuring in a type I degenerate optical parametric oscillator (DOPO) pumped above threshold. We show that a DOPO with spherical mirrors, in which the signal and idler fields correspond to first order Laguerre-Gauss modes, produces a perfectly squeezed vacuum with the shape of a Hermite-Gauss mode, within the linearized theory. This occurs at any pumping level above threshold, hence the phenomenon is non-critical. Imperfections of the rotational symmetry, due e.g. to cavity anisotropy, are shown to have a small impact, hence the result is not singular.Comment: 4 pages, 1 figure, replaced with resubmitted versio

Sequential automatic on-line determination of aquiculture nutrients: phosphate and nitrate

A continuous-flow method for the determination of nitrate and phosphate in water is proposed. The method is based on insertion of reagents and sample solutions into a single channel through a programmable switching valve. The method depends upon heteropolyacid with phosphate and on the modified Griess reaction for nitrate, and permits the determination of PO-34 in the range 1-20 μg/ml and NO-3 between 5 and 100 μg/ml, the achievable sampling frequency being 45/hour. The two analytes can be determined in N/P ratios between 0.25 and 100. The method has been applied to the determination of nitrate and phosphate in the sea-water used in fish farms

Flow injection analysis of water. Part 2: Integrated system for automatic multideterrnination

This paper describes an integrated flow injection (FI) system for the determination of ammonia, sulphate and Fe(II)/Fe(III) which can work unattended for long periods. The system was designed for the determination of individual analytes in long series of samples. Each batch of samples requires manual selection of parameters and units, such as wavelength for monitoring, preconcentration column, loops and switching of three valves to select the carrier, reagents and eluent. The system then works automatically

Espectroscopia. fundamento de la resonancia magnética nuclear

Presentamos una introducción al fenómeno de la espectroscopia, su significado y los principios físicos básicos involucrados en el proceso de absorción y emisión de  radiación que posee una capacidad suficiente para perturbar las condiciones de equilibrio de un átomo. Explicamos  el principio de operación de un espectrómetro sencillo y  analizamos la espectroscopia de resonancia magnética nuclear (RMN) una de las herramientas más poderosas con que cuenta la Medicina moderna para detectar ciertos desequilibrios en la estructura y configuración molecular.AbstractWe present an introduction to the phenomenon of spectroscopy.Its meaning and the basic physical principles involve the process of absorption and emission of radiation that possess enough capacity to perturb the conditions of equilibrium of an atom. We explain the principle of operation of a simple spectrometer and analyze the spectroscopy of nuclear magnetic resonance (NMR). It is one of the most powerful tools available to modern medicine to detect certain imbalances in the structure and molecular configuration

Flow-injection analysis for on-line monitoring of nutrients (ammonia and nitrite) in aquaculture

This article describes photometric flow injection (FI) methods for the determination of ammonia and nitrite in aquaculture. The methods are based on the use of normal and reversed FI approaches and show the potential of this technique for monitoring the input and output streams of small tanks at young fish-breeding farms. The methods meet the requirements of fish hatcheries, particularly in terms of the high sampling rate allowable (40/h)

Unsegmented flow approach for on-line monitoring of pH, conductivity, dissolved oxygen and determination of nitrite and ammonia in aquaculture

A fully automated flow system for on-line monitoring of analytes/parameters of interest in aquaculture is described. The approach has been optimized for the photometric determination of nitrite and ammonia and the continuous monitoring of pH, conductivity and dissolved oxygen, but these analytes/parameters are readily changeable as required. The system has been tested by monitoring these species in the input and output sea water streams of tanks at a fish breeding farm and also by monitoring water containing high concentrations of fish feed

Theory of quantum fluctuations of optical dissipative structures and its application to the squeezing properties of bright cavity solitons

We present a method for the study of quantum fluctuations of dissipative structures forming in nonlinear optical cavities, which we illustrate in the case of a degenerate, type I optical parametric oscillator. The method consists in (i) taking into account explicitly, through a collective variable description, the drift of the dissipative structure caused by the quantum noise, and (ii) expanding the remaining -internal- fluctuations in the biorthonormal basis associated to the linear operator governing the evolution of fluctuations in the linearized Langevin equations. We obtain general expressions for the squeezing and intensity fluctuations spectra. Then we theoretically study the squeezing properties of a special dissipative structure, namely, the bright cavity soliton. After reviewing our previous result that in the linear approximation there is a perfectly squeezed mode irrespectively of the values of the system parameters, we consider squeezing at the bifurcation points, and the squeezing detection with a plane--wave local oscillator field, taking also into account the effect of the detector size on the level of detectable squeezing.Comment: 10 figure