A comparison of spectrophotometric and denuder based approaches for the determination of gaseous molecular iodine

The presence of molecular iodine in the atmosphere is thought to have implications for both climate and human nutritional health, but measurement of the gas at low concentrations requires technically demanding techniques that are not widely accessible. Here, amylose coated denuder tubes and solvent traps coupled with spectrophotometric detection are evaluated and compared as relatively cheap and straightforward methods to measure gaseous molecular iodine at environmentally relevant concentrations. Denuder tubes were found to give unacceptably low and highly variable recoveries of molecular iodine from a test gas source, with values ranging from 1 to 62%. Blank concentrations were also high, being equivalent to a gas phase concentration of 5 pptv under typical operating conditions. Ethanol and hexane solvent traps gave much better performance. Optimisation of the hexane solvent trap method gave 100% recovery and an atmospheric limit of detection of 70 pptv, which is within the range of concentrations observed in the coastal marine atmosphere

Development of analytical methodologies for iodine species in gaseous and particulate phases of the coastal atmosphere

It has been demonstrated that iodine does have an important influence on atmospheric chemistry, especially the formation of new particles and the enrichment of iodine in marine aerosols. It was pointed out that the most probable chemical species involved in the production or growth of these particles are iodine oxides, produced photochemically from biogenic halocarbon emissions and/or iodine emission from the sea surface. However, the iodine chemistry from gaseous to particulate phase in the coastal atmosphere and the chemical nature of the condensing iodine species are still not understood. A Tenax / Carbotrap adsorption sampling technique and a thermo-desorption / cryo-trap / GC-MS system has been further developed and improved for the volatile organic iodine species in the gas phase. Several iodo-hydrocarbons such as CH3I, C2H5I, CH2ICl, CH2IBr and CH2I2 etc., have been measured in samples from a calibration test gas source (standards), real air samples and samples from seaweeds / macro-algae emission experiments. A denuder sampling technique has been developed to characterise potential precursor compounds of coastal particle formation processes, such as molecular iodine in the gas phase. Starch, TMAH (TetraMethylAmmonium Hydroxide) and TBAH (TetraButylAmmonium Hydroxide) coated denuders were tested for their efficiencies to collect I2 at the inner surface, followed by a TMAH extraction and ICP/MS determination, adding tellurium as an internal standard. The developed method has been proved to be an effective, accurate and suitable process for I2 measurement in the field, with the estimated detection limit of ~0.10 ng∙L-1 for a sampling volume of 15 L. An H2O/TMAH-Extraction-ICP/MS method has been developed for the accurate and sensitive determination of iodine species in tropospheric aerosol particles. The particle samples were collected on cellulose-nitrate filters using conventional filter holders or on cellulose nitrate/tedlar-foils using a 5-stage Berner impactor for size-segregated particle analysis. The water soluble species as IO3- and I- were separated by anion exchanging process after water extraction. Non-water soluble species including iodine oxide and organic iodine were digested and extracted by TMAH. Afterwards the triple samples were analysed by ICP/MS. The detection limit for particulate iodine was determined to be 0.10~0.20 ng•m-3 for sampling volumes of 40~100 m3. The developed methods have been used in two field measurements in May 2002 and September 2003, at and around the Mace Head Atmospheric Research Station (MHARS) located at the west coast of Ireland. Elemental iodine as a precursor of the iodine chemistry in the coastal atmosphere, was determined in the gas phase at a seaweed hot-spot around the MHARS, showing I2 concentrations were in the range of 0~1.6 ng∙L-1 and indicating a positive correlation with the ozone concentration. A seaweed-chamber experiment performed at the field measurement station showed that the I2 emission rate from macro-algae was in the range of 0.019~0.022 ng•min-1•kg-1. During these experiments, nanometer-particle concentrations were obtained from the Scanning Mobility Particle Sizer (SMPS) measurements. Particle number concentrations were found to have a linear correlation with elemental iodine in the gas phase of the seaweeds chamber, showing that gaseous I2 is one of the important precursors of the new particle formation in the coastal atmosphere. Iodine contents in the particle phase were measured in both field campaigns at and around the field measurement station. Total iodine concentrations were found to be in the range of 1.0 ~ 21.0 ng∙m-3 in the PM2.5 samples. A significant correlation between the total iodine concentrations and the nanometer-particle number concentrations was observed. The particulate iodine species analysis indicated that iodide contents are usually higher than those of iodate in all samples, with ratios in the range of 2~5:1. It is possible that those water soluble iodine species are transferred through the sea-air interface into the particle phase. The ratio of water soluble (iodate + iodide) and non-water soluble species (probably iodine oxide and organic iodine compounds) was observed to be in the range of 1:1 to 1:2. It appears that higher concentrated non-water soluble species, as the products of the photolysis from the gas phase into the particle phase, can be obtained in those samples while the nucleation events occur. That supports the idea that iodine chemistry in the coastal boundary layer is linked with new particle formation events. Furthermore, artificial aerosol particles were formed from gaseous iodine sources (e.g. CH2I2) using a laboratory reaction-chamber experiment, in which the reaction constant of the CH2I2 photolysis was calculated to be based upon the first order reaction kinetic. The end products of iodine chemistry in the particle phase were identified and quantified

In situ sensors for measurements in the global trosposphere

Current techniques available for the in situ measurement of ambient trace gas species, particulate composition, and particulate size distribution are reviewed. The operational specifications of the various techniques are described. Most of the techniques described are those that have been used in airborne applications or show promise of being adaptable to airborne applications. Some of the instruments described are specialty items that are not commercially-available. In situ measurement techniques for several meteorological parameters important in the study of the distribution and transport of ambient air pollutants are discussed. Some remote measurement techniques for meteorological parameters are also discussed. State-of-the-art measurement capabilities are compared with a list of capabilities and specifications desired by NASA for ambient measurements in the global troposphere

Entwicklung und Anwendung massenspektrometrischer Methoden zur Spurenanalytik iodhaltiger Verbindungen und aliphatischer Amine in der marinen Umwelt

In der marinen Grenzschicht beeinflussen reaktive Iodspezies wie z.B. I2 sowie aliphatische Amine eine Vielzahl atmosphärischer Prozesse, vor allem bei der Partikelneubildung spielen sie eine entscheidende Rolle. Allerdings stellt die Quantifizierung dieser Verbindungen im Spurenbereich immer noch eine große analytische Herausforderung dar. rnAus diesem Grund wurde im Rahmen der vorliegenden Arbeit das GTRAP-AMS (Gaseous compound trapping in artificially generated particles – aerosol mass spectrometry) entwickelt, um gasförmiges I2 und aliphatische Amine zu bestimmen. Hierbei wird ein Flugzeit-Aerosolmassenspektrometer (ToF-AMS), das ursprünglich für die on-line Charakterisierung von Aerosolen entwickelt wurde, mit einer GTRAP-Einheit gekoppelt. Im Fall von I2 werden mit Hilfe eines pneumatischen Zerstäubers a-Cyclodextrin/NH4Br-Partikel erzeugt, die mit dem gasförmigen I2 innerhalb der GTRAP-Einheit eine Einschlussverbindung bilden und dieses dadurch selektiv in die Partikelphase aufnehmen. Für die on-line Bestimmung gasförmiger aliphatischer Amine dagegen wurde Phosphorsäure als partikulärer Reaktionspartner eingesetzt. Nach Optimierung des GTRAP-AMS Systems wurde sowohl für I2 als auch für die aliphatischen Amine eine Nachweisgrenze im sub-ppb-Bereich für eine Zeitauflösung zwischen 1 und 30 min erhalten. Als erstes wurde das GTRAP-AMS System zur Charakterisierung von Permanentdenudern eingesetzt, um deren I2-Aufnahmefähigkeit und Wiederverwendbarkeit im Vergleich zu den herkömmlichen einmal verwendbaren a-Cyclodextrin Denudern zu testen.rnIm Anschluss daran wurde das GTRAP-AMS für die Bestimmung zeitlich aufgelöster I2- Emissionsraten ausgewählter Makroalgen unter dem Einfluss von Ozon eingesetzt. Die Kenntnis der Emissionsraten iodhaltiger Verbindungen der wichtigsten weltweit vorkommenden Makroalgen ist für die Modellierung der Iodchemie in der marinen Grenzschicht von besonderer Bedeutung. Die Resultate zeigen, dass verschiedene Makroalgen sowohl unterschiedliche zeitlich aufgelöste I2-Emissionsprofile als auch Gesamtemissionsraten liefern. Im Vergleich zu den iodorganischen Verbindungen ist die Gesamtemissionsrate an I2 allerdings eine bis zwei Größenordnungen größer. Dies und die deutlich kürzere atmosphärische Lebensdauer von I2 im Vergleich zu den iodorganischen Verbindungen führen dazu, dass I2 die dominierende iodhaltige Verbindung für die Bildung reaktiver Iodatome in der marinen Grenzschicht ist. rnDa über dem tropischen Atlantischen Ozean bislang jedoch nur ein geringer Anteil der IO- Konzentration durch die Oxidation von iodorganischen Verbindungen erklärt werden kann, wurden weitere Quellen für I2 erforscht. Deshalb wurden Kammerexperimente mit Mikrolagen durchgeführt, um deren Einfluss auf die I2-Freisetzung in die Atmosphäre zu untersuchen. Hierbei konnte gezeigt werden, dass die Anwesenheit von Mikroalgen (z.B. Coscinodiscus Wailesii) im Meerwasser zu einer erhöhten Freisetzung von I2 aus dem Meerwasser in die Atmosphäre führen kann. rnDes Weiteren wurden auch Versuche zu abiotischen Bildungswegen von I2 durchgeführt. Die Ergebnisse der Atmosphärensimulationsexperimente haben gezeigt, dass partikuläre Iodoxide durch organische Verbindungen zu I2 reduziert werden können, welches im Anschluss von der Partikelphase in die Gasphase übergehen kann und dort wieder für Gasphasenprozesse zur Verfügung steht.rnReactive iodine species (e.g. I2 or iodocarbons) and aliphatic amines play an important role in various atmospheric processes in the marine boundary layer, e.g. new particle formation and tropospheric ozone depletion. However, the trace analysis of gaseous I2 and aliphatic amines is still an analytical challenge.rnTherefore a new GTRAP-AMS system (Gaseous compound trapping in artificially generated particles – aerosol mass spectrometry) was developed to quantify gaseous I2 and aliphatic amines and is described in this work. Thereby a ToF-AMS, which was originally developed for the on-line characterization of non-refractory aerosols, was coupled with a GTRAP unit. To use the high-sensitivity of the ToF-AMS (detection limit is in the sub-µg/m3 range for 1 min integration time) for the measurement of atmospheric trace gases however, they first have to be converted from the gas phase into the particle phase by particulate reactants inside the GTRAP unit before they enter the ToF-AMS. Therefore a-cyclodextrin/NH4Br particles that are produced by an atomizer are used as selective sampling probes for I2, whereas phosphoric acid particles are used as selective probes for aliphatic amines. In general it could be demonstrated that the GTRAP-AMS has the potential for quantitative measurement of atmospheric trace gases in the sub-ppb-range with a high time resolution (1 – 30 min). rnThe GTRAP-AMS was first used for the characterization of denuders, which were permanently coated with modified a-cyclodextrin-silica gel particles. In this study their I2 collection efficiency and reusability was investigated and compared to previously developed a-cyclodextrin denuders. rnIn the following the GTRAP-AMS was used for the determination of time-resolved I2 emission rates from different macroalgae under the influence of ozone. Knowledge of the composition and the emission rates of iodine containing compounds from major world-wide macroalgae are important for modeling the iodine chemistry in the marine boundary layer. Compared to the emission rate of iodocarbons, that were measured using TD-GC-MS, the emission rate of I2 was one to two orders of magnitude higher. This and the much shorter atmospheric lifetime of I2 compared to iodocarbons demonstrate that I2 is the major source for reactive iodine atoms in the marine boundary layer. rnRecent modeling studies showed that the oxidation of iodocarbons can only explain 10 - 25% of the observed IO concentration over the tropical Atlantic Ocean. For that reason further possible sources of I2 over the open ocean were investigated. Therefore chamber experiments with microalgae were performed to study their impact on the I2 release in the atmosphere. Results of these studies show that the presence of microalgae in seawater can lead to increased release of I2 from seawater into the gas phase. rnFurthermore abiotic release mechanisms of I2 in the marine boundary layer were investigated. Atmospheric chamber studies showed that particulate iodine oxides can be reduced by organic compounds (e.g. alcohols) to produce I2. In the next step the generated I2 can be released from the particle phase to the gas phase and is then again available for gas phase chemistry.rn172 S

Ozone-Based Decolorization of Food Colorants: Characterization and Application to Fruit Leather Recycling

The commercial production of fruit leathers results in some material that is not to specification. Although this product remains edible and contains valuable ingredients such as fruit pulp, sugars and acidulates, it is not salable and its disposal is costly. Because these products are typically highly colored, recovery of fruit leather for recycling into the product requires colorant removal to avoid an unappetizing brownish color from the mixture of colorants. This research introduces a novel approach utilizing ozonation for color removal. The treatment was first applied to pure solutions of the commonly used food colorants 2-naphthalenesulfonic acid (Red 40), tartrazine (Yellow 5), and erioglaucine (Blue 1). Color removal was measured by UV/Vis spectrometer, and a Hunter colorimeter. Byproducts from ozone-based colorant decomposition were identified and quantified with SPME-GC-MS. Removal of Yellow 5, Red 40 and Blue 1 was about 65%, 80% and 90% complete, respectively, with 70 g ozone applied to 1 kg aqueous fruit leather suspension solution. Given the known structures of these dyes, a concern with this approach is the potential formation of toxic ozonolysis byproducts. In initial work, carbonyl compounds were identified as major byproducts. Among these, benzaldehyde, 2-furfural, ethanal and hexanal were identified as byproducts of known toxicity at levels sufficient for concern. A head-space solid-phase microextraction (HS-SPME) method with on-fiber derivatization using o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) was optimized for detection and quantification of carbonyl compounds in ozonated fruit leather suspensions. Ethanal, hexanal, furfural and benzaldehyde were quantified with the newly developed method, and detection limits were in the range of 0.016 - 0.030 yg/L. For furfural, the ozonolysis byproduct noted in the literature as having the highest median lethal dose value, the maximum amount generated was determined to be under the detection limit, 0.016 yg/L of 100% fruit leather solution/suspension, while hexanal was the most abundantly generated, at 80.0 y 22.0 mg/L. A conservative risk assessment based on published toxicity information for the main ozonolysis products generated in this study suggests the acceptability of ozone-based decolorization in fruit leather recycling. A preliminary cost estimate suggests a potential $0.25 million annual profit on recycling a 1,000 tons of waste fruit leathers per year

Iodine oxoacids in atmospheric aerosol formation : from chamber simulations to field observations

New particle formation is estimated to contribute to around half of the cloud condensation nuclei (CCN) in the atmosphere which in turn have a cooling effect on Earth’s surface. Only a few gas species, including sulfuric acid, oxidized organic vapors and iodine species, are confirmed to contribute to new particle formation, which converts gases to aerosol particles. While new particle formation from sulfuric acid (with water or bases, such as ammonia and amines) is recognized globally, new particle formation solely induced by pure organic vapors only occurs under special conditions. Least is known about the coverage of iodine particle formation processes in the atmosphere. Iodine species have widely been measured in marine and polar environments. However, most ambient measurements concentrated on molecular iodine (I2 ), iodine monoxide (IO), iodine dioxide (OIO) and organic iodine precursors. These measurements constrained the effect of iodine species in catalytic ozone loss processes, but far from enough to understand the particle formation processes. In this thesis, I utilized a bromide chemical ionization method to nearly comprehensively measure inorganic iodine species, including I2 , iodine oxides and oxoacids. An unprecedented performance both in coverage and sensitivity is achieved. We further deployed the bromide chemical ionization method for ambient observations at the Mace Head observatory on the Atlantic coast of Ireland. First successful online measurements of hypoiodous acid (HOI), bromoiodide (IBr) and chloroiodide (ICl) confirmed the heterogeneous uptake of HOI at ambient conditions which enhanced iodine atom production rate by 32% and accelerated ozone (O3 ) loss by 12%. Comprehensive experiments were further carried out at the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber to understand the iodine particle formation mechanisms. We found that the ion-induced (charged) and neutral nucleation proceed via distinct mechanisms. The ion-induced nucleation proceeds primarily by sequential addition of iodic acid (HIO3 ) which was measured to proceed at the kinetic limit. However, in contrast to earlier expectations, neutral nucleation additionally involves iodous acid (HIO2 ) to stabilize HIO3 , replacing the role of the negative charge in the ion-induced nucleation. After passing the critical size of nucleation, the growth of iodine particles is essentially sustained by HIO3 , with minor contributions from other species, which are present at much lower concentrations. Additionally, iodine oxoacids have much faster particle formation rates than the sulfuric acid – ammonia mixture at the same acid concentrations (when the ammonia mixing ratio is 100 parts per trillion by volume). While sulfuric acid – ammonia new particle formation has been confirmed to be an important mechanism in polar regions, the role of iodine new particle formation is usually considered to have a limited global reach. We carried out iodic acid measurements at ten boundary layer sites, ranging from the cleanest polar regions to polluted urban environments. The existence of iodic acid is ubiquitously confirmed, with concentrations comparable to sulfuric acid. This indicates a greater importance of iodine oxoacid particle formation processes than just a coastal phenomenon

A machine learning based global sea-surface iodide distribution

Iodide in the sea-surface plays an important role in the Earth system. It modulates the oxidising capacity of the troposphere and provides iodine to terrestrial ecosystems. However, our understanding of its distribution is limited due to a paucity of observations. Previous efforts to generate global distributions have generally fitted sea-surface iodide observations to relatively simple functions using proxies for iodide such as nitrate and sea-surface temperature. This approach fails to account for coastal influences and variation in the bio-geochemical environment. Here we use a machine learning regression approach (random forest regression) to generate a high-resolution (0:125° × 0:125°, ∼ 12:5km × 12:5km), monthly dataset of present-day global sea-surface iodide. We use a compilation of iodide observations (1967-2018) that has a 45 % larger sample size than has been used previously as the dependent variable and co-located ancillary parameters (temperature, nitrate, phosphate, salinity, shortwave radiation, topographic depth, mixed layer depth, and chlorophyll a) from global climatologies as the independent variables. We investigate the regression models generated using different combinations of ancillary parameters and select the 10 best-performing models to be included in an ensemble prediction. We then use this ensemble of models, combined with global fields of the ancillary parameters, to predict new high-resolution monthly global sea-surface iodide fields representing the present day. Sea-surface temperature is the most important variable in all 10 models. We estimate a global average sea-surface iodide concentration of 106 nM (with an uncertainty of ∼ 20 %), which is within the range of previous estimates (60-130 nM). Similar to previous work, higher concentrations are predicted for the tropics than for the extra-tropics. Unlike the previous parameterisations, higher concentrations are also predicted for shallow areas such as coastal regions and the South China Sea. Compared to previous work, the new parameterisation better captures observed variability. The iodide concentrations calculated here are significantly higher (40 % on a global basis) than the commonly used MacDonald et al. (2014) parameterisation, with implications for our understanding of iodine in the atmosphere. We envisage these fields could be used to represent present-day sea-surface iodide concentrations, in applications such as climate and air-quality modelling. The global iodide dataset is made freely available to the community (https://doi.org/10/gfv5v3, Sherwen et al., 2019), and as new observations are made, we will update the global dataset through a "living data" model

Métodos automáticos de análisis para la determinación de parámetros de interés ambiental

El incremento del vertido de sustancias contaminantes al medio ambiente, debido al desarrollo industrial y los malos hábitos de consumo, han provocado la ruptura del equilibrio de muchos ecosistemas llegando afectar, en muchas ocasiones, a los humanos. Con el objetivo de controlar y disminuir estos efectos, los gobiernos han dirigido acciones para legislar y regular el vertido de sustancias tóxicas al medio. De esta manera el Gobierno Nacional de España ha financiado a nuestro grupo de investigación, el proyecto del Plan Nacional en Ciencia y Tecnología Química titulado “Desarrollo de métodos automáticos de análisis. Aplicación a planes de vigilancia ambiental”, con referencia CTQ 2010-15541. La presente tesis forma parte de este proyecto siendo su objetivo general el desarrollo de nuevos métodos automáticos para la determinación de especies químicas de interés ambiental. En la introducción de la tesis se realiza una revisión sobre la automatización del laboratorio químico mediante técnicas de análisis en flujo y se describen las dos utilizadas en esta tesis. Seguidamente se revisa la aplicación de estas técnicas a la automatización de los métodos electroquímicos, especialmente la conductimetría y la voltamperometría redisolución anódica. En el tercer apartado de la introducción se recogen los aportes de las técnicas de flujo en la automatización de procesos de tratamientos de muestras como la difusión gaseosa y la extracción líquido-líquido. De esta última técnica se resume su evolución histórica hasta los métodos más recientes descritos que logran la automatización total del proceso de extracción y que se pudieran clasificar dentro de la tercera generación de las técnicas en flujo. En el último apartado de la introducción se trata la automatización de métodos cinético-catalíticos mediante técnicas de análisis en flujo, destacando el elevado potencial que tienen estos métodos para el análisis de trazas y el bajo número de trabajos publicados donde se consigue la automatización de los mismos. Contenido de la investigación En esta tesis se han utilizado dos técnicas de análisis en flujo, el análisis por inyección en flujo multijeringa (MSFIA) y los sistemas en flujo multibombas (MPFS), acopladas a dos métodos de tratamiento de muestras, la difusión gaseosa y la extracción líquido-líquido, y tres técnicas de detección, la voltamperometría de redisolución anódica, la conductimetría y la espectrofotometría, para obtener cinco sistemas automáticos de análisis. Los sistemas desarrollados han sido aplicados a la determinación, fundamentalmente en agua de mar, de cinco analitos inorgánicos: cadmio, cromato, yoduro, amonio y carbono inorgánico total, en muestras ambientales. Durante el desarrollo de estos sistemas y el estudio de las técnicas utilizadas, se han solucionado problemas relacionados con la automatización de las técnicas en flujo, lo que ha mejorado significativamente las características analíticas de los métodos presentados en comparación con otros similares reportados en la literatura. Entre estas mejoras se encuentran por ejemplo el incremento de la reproducibilidad y sensibilidad de las determinaciones, la disminución de los volúmenes de reactivos y muestras utilizados, la reducción de las dimensiones del sistema y de los costes de la instrumentación, así como el aumento del grado de automatización del proceso analítico: tratamiento de la muestra, calibración y detección. Los trabajos presentados en esta tesis son los siguientes: 1- Un método simple, económico, portátil y automatizado mediante MSFIA que permite la determinación de cadmio mediante voltamperometria de redisolución anódica usando electrodos impresos con película de bismuto. (SPE- BiF-ASV- SFIA) 2- Un sistema automatizado mediante la técnica de MSFIA para la determinación de amonio en muestras de aguas naturales y marinas utilizando la difusión gaseosa y la detección conductimétrica. (C-GD-MSFIA) 3- Un analizador automático, basado en la técnica de MPFS, para la determinación de amonio y de carbono inorgánico total en muestras de aguas marinas usando difusión gaseosa y detección conductimétrica. (C-GD-MPFS) 4- Un sistema totalmente automatizado de microextraccion líquido-líquido dentro de la jeringa de una bureta automática para la determinación espectrofotométrica de cromo (VI) en muestras de aguas naturales. (In syringe-MSA-DLLME) 5- Un chip conductor de microfluidos para la automatización mediante MSFIA de un método cinético-catalíticos que permita el análisis de ioduro en agua de mar y fármacos con un consumo muy reducido de reactivos. (CHIP-MSFIA-Catalytic) Conclusiones Se han desarrollado nuevos sistemas automáticos para la determinación de analitos inorgánicos de interés ambiental. La utilización de técnicas de análisis en flujo multiconmutadas, como MSFIA y MPFS, han demostrado ser muy útiles en la automatización de sistemas de análisis que utilizan diferentes técnicas de detección (electroquímicas y espectrofotométricas), de pretratamiento de muestra y de métodos de determinación cinéticocatalíticos. Los sistemas desarrollados han demostrado su efectividad en la determinación de analitos inorgánicos (cadmio, cromato, yoduro, amonio y carbono inorgánico total) en muestras tan complejas como las aguas de mar, aguas residuales o preparados farmacéuticos. Bibliografía 1.Henríquez C, Laglera LM, Alpizar MJ, Calvo J, Arduini F, Cerdà V: Cadmium determination in natural water samples with an automatic multisyringe flow injection system coupled to a flow-through screen printed electrode. Talanta 2012, 96(0):140-146. 2.Henríquez C, Horstkotte B, Cerdá V: Conductimetric determination of ammonium by a multisyringe flow injection system applying gas diffusion Int J Environ Anal Chem 2012:1-17. 3.Henríquez C, Horstkotte B, Cerdá V: A highly reproducible and robust solenoid micropump system for the analysis of total inorganic carbon and ammonium using gas diffusion with conductometric detection. Talanta 2013, In review 4.Henríquez C, Horstkotte B, Solich P, Cerdá V: In-syringe magnetic stirring assisted liquid-liquid microextraction for spectrophotometric determination of Cr (VI) in waters. Analytical and Bioanalytical Chemistry 2013, Accepted/in press. 5.Abouhiat FZ, Henríquez C, Horstkotte B, El Yousfi F, Cerdà V: A miniaturized analyzer for the catalytic determination of iodide in seawater and pharmaceutical samples. Talanta 2013, 108(0):92-102.Introducción The increasing discharge of pollutants into the environment due to the industrial development and consumer habits have caused the increasing unbalance of many ecosystems, already affecting in many occasions human species itself. In order to control and reduce these effects, many governments have initiated actions to control the discharge of toxic substances into the environment. In this way, the Spanish Government has funded, to our research group, the project of the National Science and Technology Chemistry entitled “Development of automated methods of analysis. Application to environmental monitoring plans”, with reference CTQ 2010- 15541. This PhD thesis is part of this overall project with the main objective of the development of new automated methods for the determination of some chemical species of environmental interest. In the first part of the introduction of this thesis, the automation of different procedures in a chemical laboratory by the use of flow techniques is reviewed and the two selected flow techniques are described. In the second section, the application of these techniques in the automation of electrochemical methods, especially conductometry and anodic stripping voltammetry, is reviewed. In the third section of the introduction, the contributions of flow techniques to the automation sample pretreatment are discussed, especially for gaseous diffusion and liquid-liquid extraction. Moreover, it was reviewed the historical evolution and the most recent reported methods to achieve the full automation of liquid-liquid extraction inside the syringe, which could be classified as the third generation of flow techniques. The last part of the introduction deals with the automation of kinetic-catalytic methods using flow techniques, emphasizing the high potential of these methods for trace analysis and the low number of published papers on this subject. Research content. In this thesis, two flow techniques, MSFIA and MPFS, coupled to two sample pretreatment methods, gas diffusion and liquid-liquid extraction, and three detection techniques, anodic stripping voltammetry, conductometry and spectrophotometry, have been used to develop five automatic analytical systems. These systems have been applied to the determination of five inorganic analytes: cadmium, chromate, iodide, ammonium, and total inorganic carbon and applied to different environmental water samples with main focus on seawater. Involved in the development of these systems were the study of the used techniques and the finding of solutions for the problems related to the automation using flow techniques. Significant improvements of the analytical characteristics of the presented methods in comparison with similar ones reported in the literature are obtained. These improvement were an increase of the reproducibility and sensitivity of measurement, the decrease of reagent and sample consumption, the reduction of the analyzers’ sizes and instrumentation costs, and further, an increase of the automation degree of the analytical procedure, including: sample pretreatment, calibration and detection. The presented contributions are listed below: 1- A simple, economic, automated, and portable analyzer system based on MSFIA, which allows the determination of cadmium with anodic stripping voltammetry using a bismuth film coated screen printed electrode. (SPE-BiF-MSFIA) 2- An automatic MSFIA system for the determination of ammonium in naturals and seawaters in a very wide concentration range using gas diffusion and conductometric detection. (C-GD-MSFIA) 3- An automated and highly reproducible analyzer based on MPFS for the determination of total inorganic carbon and ammonium in seawaters using gas diffusion and conductometric detection. (C-GD-MPFS) 4- A fully automated in-syringe magnetic stirred-assisted dispersive liquid-liquid microextraction system for the spectrophotometric determination of chromate in natural waters. (In syringe-MSA-DLLME) 5- A microfluidic “Chip” conductor to be used in combination with MSFIA for the automated quantification of iodide in seawaters and pharmaceutical preparations using a kinetic-catalytic method characterized by a very low reagent and sample consumption. (CHIP-MSFIA-Catalytic) Conclusions Five new systems have been developed for the automatic determination of inorganic analytes of environmental interest. The use of the multi-commutated flow techniques MSFIA and MPFS has proven to be very useful for the automation of the analytical systems, coupling to different detection techniques, as well as sample pretreatment and kinetic-catalytic determinations. The developed systems have been confirmed to be efficient for the determination of inorganic analytes in complex sample matrices such as seawater, wastewater, or pharmaceutical preparations