In this communication, a new methodology for the simultaneous and automated monitoring of biosorption processes of multimetal mixtures of polluting heavy metals on vegetable wastes based on flow-injection potentiometry (FIP) and electronic tongue detection (ET) is presented. A fixed-bed column filled with grape stalks from wine industry wastes is used as the biosorption setup to remove the metal mixtures from the influent solution. The monitoring system consists in a computer controlled-FIP prototype with the ET based on an array of 9 flow-through ion-selective electrodes and electrodes with generic response to divalent ions placed in series, plus an artificial neural network response model. The cross-response to Cu2+, Cd2+, Zn2+, Pb2+ and Ca2+ (as target ions) is used, and only when dynamic treatment of the kinetic components of the transient signal is incorporated, a correct operation of the system is achieved. For this purpose, the FIA peaks are transformed via use of Fourier treatment, and selected coefficients are used to feed an artificial neural network response model...
In this communication, a new methodology for the simultaneous and automated monitoring of biosorption processes of multimetal mixtures of polluting heavy metals on vegetable wastes based on flow-injection potentiometry (FIP) and electronic tongue detection (ET) is presented. A fixed-bed column filled with grape stalks from wine industry wastes is used as the biosorption setup to remove the metal mixtures from the influent solution. The monitoring system consists in a computer controlled-FIP prototype with the ET based on an array of 9 flow-through ion-selective electrodes and electrodes with generic response to divalent ions placed in series, plus an artificial neural network response model. The cross-response to Cu2+, Cd2+, Zn2+, Pb2+ and Ca2+ (as target ions) is used, and only when dynamic treatment of the kinetic components of the transient signal is incorporated, a correct operation of the system is achieved. For this purpose, the FIA peaks are transformed via use of Fourier treatment, and selected coefficients are used to feed an artificial neural network response model. Real-time monitoring of different binary (Cu2+/ Pb2+), (Cu2+/ Zn2+) and ternary mixtures (Cu2+/ Pb2+/ Zn2+), (Cu2+/ Zn2+/ Cd2+), simultaneous to the release of Ca2+ in the effluent solution, are achieved satisfactorily using the reported system, obtaining the corresponding breakthrough curves, and showing the ion-exchange mechanism among the different metals. Analytical performance is verified against conventional spectroscopic techniques, with good concordance of the obtained breakthrough curves and modeled adsorption parameters.
An automated flow injection potentiometric (FIP) system with electronic tongue detection (ET) is used for the monitoring of biosorption processes of heavy metals on vegetable wastes. Grape stalk wastes are used as biosorbent to remove Cu2+ ions in a fixed-bed column configuration. The ET is formed by a 5-sensor array with Cu2+ and Ca2+-selective electrodes and electrodes with generic response to heavy-metals, plus an artificial neural network response model of the sensor's cross-response. The real-time monitoring of both the Cu2+ and the cation exchanged and released (Ca2+) in the effluent solution is performed by using flow-injection potentiometric electronic tongue system. The coupling of the electronic tongue with automation features of the flow-injection system allows us to accurately characterize the Cu2+ ion-biosorption process, through obtaining its breakthrough curves, and the profile of the Ca2+ ion release. In parallel, fractions of the extract solution are analysed by spectroscopic techniques in order to validate the results obtained with the reported methodology. The sorption performance of grape stalks is also evaluated by means of well-established sorption models.
A simple comparison is made to evaluate the relative performance of active and passive sampling methods for the analysis of volatile organic compounds (VOCs) in ambient air. The active sampling is done through a multi-sorbent bed tube (Carbotrap, Carbopack X, Carboxen 569) created in our laboratory and the passive sampling through the Radiello® diffusive sampler specified for thermal desorption (filled with Carbograph 4). Daily duplicate samples of multi-sorbent bed tubes were taken during a period of
14 days. During the same period of time, quadruplicate samples of Radiello® tubes were taken during 3 days, 4 days, 7 days and 14 days. The sampling was carried out indoors during the months of February
and March 2010 and outdoors during the month of July 2010 in La Canonja (Tarragona, Spain). The analysis was performed by automatic thermal desorption (ATD) coupled with capillary gas chromatography (GC)/mass spectrometry detector (MSD). The analytical performance of the two sampling approaches
was evaluated by describing several quality assurance parameters. The results show that the analytical performances of the methodologies studied are quite similar. They display low limits of detection, good
precision, accuracy and desorption efficiency, and low levels of breakthrough for multi-sorbent bed tubes. However, the two monitoring methods produced varying air-borne concentration data for most of the
studied compounds, and the Radiello® samplers generally gave higher results. Sampling rates (Qk) were determined experimentally, and their values were higher than those supplied by the producer. As the
experimental calculation of Qk values is generally carried out by the suppliers in exposure chambers with only the target compounds present in the air samples, as well as in concentrations dissimilar to those
found in ambient air, the use of constant settled Qk can lead to inaccurate results in complex samples.
A comparison between two types of adsorbent tubes, the commonly used Tenax TA and a multi-sorbent bed (Carbotrap, Carbopack X, Carboxen 569) tube developed in our laboratory, has been done to evaluate their usefulness in the analysis of VOCs in ambient air. Duplicate indoor and outdoor samples of Tenax TA and multi-sorbent tubes of 10, 20, 40, 60 and 90 l were taken in Barcelona city (Spain) on July and October of 2009. Breakthrough values (defined as %VOCs found in the back tube) were determined
for all sampling volumes connecting two sampling tubes in series. The analysis was performed by automatic thermal desorption (ATD) coupled with capillary gas chromatography (GC)/mass spectrometry
detector (MSD). Significant differences between the concentrations obtained-from multi-sorbent bed and Tenax TA tubes are observed for the very volatile compounds (56 ◦C < boiling point < 100◦C and 4 kPa < vapour pressure (20◦C) < 47 kPa) (e.g. acetone, isopropanol, n-hexane) and for alcohols and chlorinated compounds (e.g. 1-butanol, carbon disulphide, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene), being the concentrations found higher in multi-sorbent bed than in Tenax TA tubes. On the other hand, mainly all compounds with boiling points higher than 100◦C ( except α-pinene, chlorinated and polar compounds) do not show significant differences between the obtained
multi-sorbent bed and Tenax TA tube concentrations. For the concentrations obtained (5 ppt to 100 ppb), Tenax TA present high breakthrough values (from 0 to 77%) for mainly all compounds and sampling volumes studied. On the other hand, multi-sorbent bed tubes do not exhibit important breakthrough values for these compounds, except the VVOCs ethanol (for all sampled volumes), and acetone, dichloromethane and isopropanol (for sampling volumes over 40 l). The concentration differences observed between Tenax TA and multisorbent bed tubes are directly related to the high breakthrough values determined for Tenax TA adsorbent.
Synchrotron radiation X-ray diffraction ( -SR-XRD) and Fourier transform infrared spectroscopy ( -SRFTIR)
are used in the non-destructive identification of reaction and aging compounds from micrometric
ancient painting layers. The combination of the micrometer size and non-destructive nature of the techniques
together with the high resolution and brilliance of the synchrotron radiation has proved to be a
procedure most advantageous for the study of reaction, aging and degradation processes. Copper, lead
and calcium carboxylates and oxalates are determined in the chromatic, preparation and alteration layers
from 15th century egg tempera and oil paintings. Their nature and crystallinity have been assessed. Some
hypothesis about the mechanisms of development of both carboxylates and oxalates are presented.
This work presents a comparative study between two different methods for the preparation of mediator-modified screen-printed electrodes,
to be used as detectors in a reliable flow injection system for the determination of the nicotinamide adenine dinucleotide (NADH) coenzyme.
The best strategy was selected for the final development of compact biosensors based on dehydrogenase enzymes. For the first immobilisation
strategy, different redox mediators were electropolymerised onto the SPE surface. The second immobilisation strategy was carried out using
polysulfone–graphite composites, which were deposited by screen-printing technology onto the screen-printed electrode (SPE) surface. Both
methods achieved an effective and reliable incorporation of redox mediators to the SPE configuration. Finally, a flow system for ammonium
determination was developed using a glutamate dehydrogenase (GlDH)-Meldola’s Blue (MB)-polysulfone-composite film-based biosensor.
The stability of the redox mediators inside the composite films as well as the negligible fouling effect observed on the electrode surface improve the
repeatability and reproducibility of the sensors, important features for continuous analysis in flow systems. Furthermore, the optimised bio/sensors,
incorporated in a flow injection system, showed good sensitivities and short response times. Such a good analytical performance together with
the simple and fast sensor construction are interesting characteristics to consider the polysulfone-composite films as attractive electrochemical
transducer materials for the development of new dehydrogenase-based SPEs.
A sequential injection (SI)-DAD spectrophotometric method to control the exhaustion of dyes in a mixture of three dyes from a tanning industry process has been developed. It is based on an interdiffusion process of the sample and reagents which leads to a gradual fall in pH through the channel to the detector recording a data matrix. The aim of this paper is to develop a second-order calibration model that is unaffected by interferents by applying multivariate curve resolution with alternating least squares (MCR-ALS). We obtained a linear calibration in the 5–30 mg l−1 range with a correlation coefficient of 0.999 for each dye with detection limits of 2.6, 3.9 and 2.1 mg l−1 for Acid Red, Acid Brown and Acid Orange,
respectively. The simultaneous determination of the three dyes from tanning samples showed a satisfactory precision for the three analytes. The method has been validated comparing the concentration of some spiked samples with the expected concentration using a t-paired test. When we
used this method to study the exhaustion of dyes, we found that there were several stages in this process. These data may be the key to optimising the exhaustion process.