Preparative ion exchange for salt solutions

Ty��ss�� tutkittiin moniarvoisten metalliformiaattien valmistusta ioninvaihto-menetelm��ll��. Kirjallisuustutkimus k��sitteleetunnettuja alumiiniformiaatin ja rautaformiaatin valmistusmenetelmi��, kationinvaihtohartsien ominaisuuksia, ioninvaihtohartsien selektiivisyytt�� ja alumiinin, raudan, magnesiumin ja sinkin vesikemiaa. Laboratoriokokeiden avulla tutkittiin sinkki-, magnesium-, rauta(II)- ja alumiiniformiaattien valmistusta ioninvaihdolla. Kokeet suoritettiin kolonnissa, joka oli pakattu makrohuokoisella tai geelim��isell�� vahvalla kationin-vaihtohartsilla. Hartsi vaihdettiin natriummuodosta metallimuotoon metallikloridi- tai metallisulfaattiliuoksella.Metalli eluoitiin hartsista natriumformiaatilla. Formiaattien valmistus onnistui makrohuokoista vahvaa kationinvaihtohartsia k��ytt��m��ll��. Rauta(II)formiaatin valmistus oli vaikeampaa kuin muiden formiaattien, koska rauta(II) hapettui osittain rauta(III):ksi valmistuksen aikana. Alumiiniformiaattia valmistettiin k��ytt��en sek�� makrohuokoista ett�� geelim��ist�� hartsia. Makrohuokoisen hartsin havaittiin soveltuvan geelim��ist�� hartsia paremmin alumiiniformiaatin valmistukseen. Kungeelim��ist�� hartsia k��ytettiin, noin 30 % alumiinista j��i kiinni hartsiin eik�� siten eluoitunut. Ioninvaihdon selektiivisyyskertoimien saamiseksi suoritettiin tasapainokokeita. Selektiivisyyskertoimia k��ytettiin ioninvaihtokolonnin dynaamisessa simuloinnissa. Ioninvaihdon simuloiminen dynaamisella kolonnimallilla onnistui hyvin.

Coifman-aallokkeet ja skaalaussuotimen muodostus differentiaalievoluut ion avulla

Ortogonaalisen M-kaistaisen moniresoluutioanalyysin matemaattiset perusteet esitet����n yksityiskohtaisesti. Coifman-aallokkeiden m����ritelm�� yleistet����n dilaatiokertoimelle M ja nollasta poikkeavalle h��vi��vien momenttien keskukselle.Funktion approksimointia n��ytepisteist�� aallokkeiden avulla pohditaan ja erityisesti esitet����n approksimaation asymptoottinen virhearvio Coifman-aallokkeille. Skaalaussuotimelle osoitetaan v��ltt��m��tt��m��t ja riitt��v��t ehdot, jotka johtavat yleistettyihin Coifman-aallokkeisiin. Moniresoluutioanalyysin tiheys todistetaansuoraan Lebesguen integraalin m����ritelm����n perustuen yksik��n partitio-ominaisuutta k��ytt��en. Todistus on riitt��v�� sellaisenaan avaruudessa L2(Wd) k��ytt��m��tt�� Fourier-tason ominaisuuksia tai ehtoja. Mallatin algoritmi johdetaan M-kaistaisille aallokkeille ja moniuloitteisille signaaleille. Algoritmille esitet����n my��s rekursiivinen muoto. Differentiaalievoluutioalgoritmin avulla ratkaistaan Coifman-aallokkeisiin liittyvien skaalaussuotimien kertoimien arvoja useille skaalausfunktiolle. Approksimaatio- ja kuvanpakkausesimerkkej�� esitet����n menetelmien havainnollistamiseksi. Differentiaalievoluutioalgoritmin avulla etsit����n my��s referenssikuville optimoitu skaalaussuodin. L��ydetty suodin on regulaarinen ja eritt��insymmetrinen.

Ion-exchange resins as stationary phase in reactive chromatography

Dynamic behavior of bothisothermal and non-isothermal single-column chromatographic reactors with an ion-exchange resin as the stationary phase was investigated. The reactor performance was interpreted by using results obtained when studying the effect of the resin properties on the equilibrium and kinetic phenomena occurring simultaneously in the reactor. Mathematical models were derived for each phenomenon and combined to simulate the chromatographic reactor. The phenomena studied includes phase equilibria in multicomponent liquid mixture��ion-exchange resin systems, chemicalequilibrium in the presence of a resin catalyst, diffusion of liquids in gel-type and macroporous resins, and chemical reaction kinetics. Above all, attention was paid to the swelling behavior of the resins and how it affects the kinetic phenomena. Several poly(styrene-co-divinylbenzene) resins with different cross-link densities and internal porosities were used. Esterification of acetic acid with ethanol to produce ethyl acetate and water was used as a model reaction system. Choosing an ion-exchange resin with a low cross-link density is beneficial inthe case of the present reaction system: the amount of ethyl acetate as well the ethyl acetate to water mole ratio in the effluent stream increase with decreasing cross-link density. The enhanced performance of the reactor is mainly attributed to increasing reaction rate, which in turn originates from the phase equilibrium behavior of the system. Also mass transfer considerations favor the use ofresins with low cross-link density. The diffusion coefficients of liquids in the gel-type ion-exchange resins were found to fall rapidly when the extent of swelling became low. Glass transition of the polymer was not found to significantlyretard the diffusion in sulfonated PS��DVB ion-exchange resins. It was also shown that non-isothermal operation of a chromatographic reactor could be used to significantly enhance the reactor performance. In the case of the exothermic modelreaction system and a near-adiabatic column, a positive thermal wave (higher temperature than in the initial state) was found to travel together with the reactive front. This further increased the conversion of the reactants. Diffusion-induced volume changes of the ion-exchange resins were studied in a flow-through cell. It was shown that describing the swelling and shrinking kinetics of the particles calls for a mass transfer model that explicitly includes the limited expansibility of the polymer network. A good description of the process was obtained by combining the generalized Maxwell-Stefan approach and an activity model that was derived from the thermodynamics of polymer solutions and gels. The swelling pressure in the resin phase was evaluated by using a non-Gaussian expression forthe polymer chain length distribution. Dimensional changes of the resin particles necessitate the use of non-standard mathematical tools for dynamic simulations. A transformed coordinate system, where the mass of the polymer was used as a spatial variable, was applied when simulating the chromatographic reactor columns as well as the swelling and shrinking kinetics of the resin particles. Shrinking of the particles in a column leads to formation of dead volume on top of the resin bed. In ordinary Eulerian coordinates, this results in a moving discontinuity that in turn causes numerical difficulties in the solution of the PDE system. The motion of the discontinuity was eliminated by spanning two calculation grids in the column that overlapped at the top of the resin bed. The reactive and non-reactive phase equilibrium data were correlated with a model derived from thethermodynamics of polymer solution and gels. The thermodynamic approach used inthis work is best suited at high degrees of swelling because the polymer matrixmay be in the glassy state when the extent of swelling is low.

Lentotuhkan fraktiointi s��hk��suodattimella ja Ion Blast -menetelm��ll��

Diplomity�� on osa YTI-tutkimuskeskuksessa vuosina 2002 - 2004 toteutettavaa J��tekompostit rakeiksi tuhkaseostuksella -k��ytt��arvon parantaminen -projektia. Ty��ss�� tutkittiin Etel��-Savon Energia Oy:n Pursialan voimalaitoksen lentotuhkan fraktioimista voimalaitoksen nykyisell�� 3-kentt��isell�� s��hk��suodattimella ja pilot-mittakaavaisella Ion Blast -koelaitteistolla. S��hk��suodattimen koeajojen aikana muuteltiin sen ajotapaa mm. CBO -suhteen ja maksimij��nniteasetuksen avulla. Ion Blast -koelaitteistolla tutkittiin mahdollisuuksia voimalaitoksen lentotuhkan puhdistamiseksi raskasmetalleista. Lentotuhkan hy��tyk��ytt���� vaikeuttaa sen raskasmetallipitoisuuksien suuri vaihtelu. Ongelmallisin raskasmetalli puuper��isess�� lentotuhkassa on kadmium, jonka lannoitelains����d��nn��n raja-arvo on t��ll�� hetkell�� 3 mg/kg. S��hk��suodattimella tehtyjen fraktiointikokeiden perusteella voidaan todeta raskasmetallipitoisuuksien olevan pienimmill����n s��hk��suodattimen 1-kent��ss�� ja suurimmillaan 3-kent��ss��. T��m�� johtuu siit��, ett�� 1-kentt����n ker����ntyy hiukkaskooltaan suurimmat lentotuhkahiukkaset ja 3-kent��ss�� on mukana enemm��n pienhiukkasia sis��lt��v���� tuhkaa. Lannoitteeksi menev��n tuhkan Cd-pitoisuutta voidaan v��hent���� parhaimmillaan jopa 70 % s��hk��suodattimella fraktioimalla. Muiden raskasmetallien pitoisuudet eiv��t v��hene aivan yht�� paljon. S��hk��suodattimella voidaan tulosten perusteella fraktioida lentotuhkaa. S��hk��suodattimella ei kuitenkaan voida varmasti saavuttaa alle 3 mg/kg Cd-pitoisuuksia polttoaineen laadunvaihtelun vuoksi. Ion Blast -koelaitteiston tulokset tukevat s��hk��suodattimella tehtyj�� kokeita. Erottimen j��nnitteen kasvaessa raskasmetalleja sis��lt��vien hiukkasten erotusaste kasvaa. Ion Blast -laitteistolla tehdyiss�� kokeissa my��s Cd-pitoisuus oli korkeimmillaan pienimm��n raeluokan hiukkasissa ja laski sitten raeluokan suurentuessa. Ion Blast -laitteisto ei kuitenkaan sellaisenaan ole hyv�� fraktiointiin. Se on liian tehokas, jolloin se puhdistaa tehokkaasti my��s raskasmetalleja sis��lt��v��t pienhiukkaset. Jos laitetta aiotaan k��ytt���� fraktiointiin, tulisi sen rakennetta muuttaa.

Ion modulated organic transistors

I likhet med vanliga plaster ��r de &#960;-konjugerade polymererna flexibla, l��sliga och processbara vid l��ga temperaturer (< 150 ��C). D��rut��ver har de egenskapen att leda str��m. Konduktivitetsintervallet ��r brett och omfattar n��stintill metallisk ledningsf��rm��ga �� ena sidan, via halvledarkonduktiva till isolerande �� andra sidan. Polymererna utg��rs av regelbundna kedjor av kolatomer och associeras s��lunda till organiska material. Sedan de f��rsta vetenskapliga rapporterna publicerades vid slutet av 1970-talet har &#960;-konjugerade polymerer anv��nts och utvecklats i exempelvis solceller, dioder, lysdioder och transistorer. Nobelpriset i kemi tilldelades ��r 2000 ��t Hideki Shirakawa, Alan J. Heeger och Alan G. MacDiarmid f��r uppt��ckten och utvecklandet av ledande polymerer. I min avhandling har jag arbetat med att utveckla och f��rst�� l��gsp��nnings jonmodulerade organiska transistorer. Tv�� typer av jonmodulerade organiska transistorer studeras: (1) den jonmodulerade organiska f��lteffekt transistorn (jonmodulerade OFETen), som utg��r den centrala transistorn i avhandlingen, samt (2) den elektrokemiska transistorn. Den f��rsta typen fungerar som en konventionell OFET. Str��mmen i halvledaren moduleras av det elektriska f��ltet ��ver isolatorn. Med anv��ndandet av en elektrolyt ���isolator��� orsakar polariseringen av jonerna d��remot ett h��gt elektriskt f��lt vid elektrolyt/halvledargr��nssnittet och man ��stadkommer modulering av str��mmen redan vid n��gra volts drivsp��nningar. I den andra typen utnyttjas elektrokemi f��r att medelst reduktion/oxidation modulera str��mmen i den &#960;-konjugerade polymeren. Ett viktigt ��ndam��l i avhandlingen har ocks�� varit att kunna tillverka transistorerna med masstillverkningsmetoder. I avhandlingen presenteras de jonmodulerade organiska transistorernas m��jlighet att framst��llas med masstillverkningsmetoder. Nya koncept introduceras och svagheter identifieras. Skillnaderna mellan OFETen, jonmodulerade OFETen och den elektrokemiska transistorn klarg��rs. Arbetet skall d��remot inte anses fullbordat utan forskningen fortg��r f��r att kringg�� svagheterna, ��ka p�� transistorernas stabilitet och framf��rallt till��mpa dem i innovativa applikationer.

Ion selective electrodes for determination of low and ultra low concentrations of lead (II) in natural waters

Att ��vervaka f��rekomsten av giftiga komponenter i naturliga vattendrag ��r n��dv��ndigt f��r m��nniskans v��lm��ende. Eftersom halten av f��roreningar i naturens ekosystem b��r h��llas m��jligast l��g, p��g��r en st��ndig jakt efter kemiska analysmetoder med allt l��gre detektionsgr��nser. I dagens l��ge g��rs milj��analyser med dyr och sofistikerad instrumentering som kr��ver mycket underh��ll. Jonselektiva elektroder har flera goda egenskaper som t.ex. b��rbarhet, l��g energif��rbrukning, och dessutom ��r de relativt kostnadseffektiva. Att anv��nda jonselektiva elektroder vid milj��analyser ��r m��jligt om deras k��nslighetsomr��de kan utvidgas genom att s��nka deras detektionsgr��nser. F��r att s��nka detektionsgr��nsen f��r Pb(II)-selektiva elektroder unders��ktes olika typer av jonselektiva membran som baserades p�� polyakrylat-kopolymerer, PVC och PbS/Ag2S. Fast-fas elektroder med membran av PbS/Ag2S ��r i allm��nhet enklare och mer robusta ��n konventionella elektroder vid sp��r��mnesanalys av joniska f��roreningar. Fast-fas elektrodernas detektionsgr��ns s��nktes i detta arbete med en nyutvecklad galvanostatisk polariseringsmetod och de kunde sedan framg��ngsrikt anv��ndas f��r kvantitativa best��mningar av bly(II)-halter i milj��prov som hade samlats in i den finska sk��rg��rden n��ra tidigare industriomr��den. Analysresultaten som erh��lls med jonselektiva elektroder bekr��ftades med andra analytiska metoder. Att s��nka detektionsgr��nsen m.hj.a. den nyutvecklade polariseringsmetoden m��jligg��r best��mning av l��ga och ultra-l��ga blyhalter som inte kunde n��s med klassisk potentiometri. Den verkliga f��rdelen med att anv��nda dessa blyselektiva elektroder ��r m��jligheten att utf��ra m��tningar i obehandlade milj��prov trots n��rvaron av fasta partiklar vilket inte ��r m��jligt att g��ra med andra analysmetoder. Jag v��ntar mig att den nyutvecklade polariseringsmetoden kommer att s��tta en trend i sp��r��mnesanalys med jonselektiva elektroder.

Electroactive ion exchange membranes based on conducting polymers

Ion exchange membranes are indispensable for the separation of ionic species. They can discriminate between anions and cations depending on the type of fixed ionic group present in the membrane. These conventional ion exchange membranes (CIX) have exceptional ionic conductivity, which is advantageous in various electromembrane separation processes such as electrodialysis, electrodeionisation and electrochemical ion exchange. The main disadvantage of CIX membranes is their high electrical resistance owing to the fact that the membranes are electronically non conductive. An alternative can be electroactive ion exchange membranes, which are ionically and electronically conducting. Polypyrrole (PPy) is a type of electroactive ion exchange material as well as a commonly known conducting polymer. When PPy membranes are repeatedly reduced and oxidised, ions are pumped through the membrane. The main aim of this thesis was to develop electroactive cation transport membranes based on PPy for the selective transport of divalent cations. Membranes developed composed of PPy films deposited on commercially available support materials. To carry out this study, cation exchange membranes based on PPy doped with immobile anions were prepared. Two types of dopant anions known to interact with divalent metal ions were considered, namely 4-sulphonic calix[6]arene (C6S) and carboxylated multiwalled carbon nanotubes (CNT). The transport of ions across membranes containing PPy doped with polystyrene sulphonate (PSS) and PPy doped with para-toluene sulphonate (pTS) was also studied in order to understand the nature of ion transport and permeability across PPy(CNT) and PPy(C6S) membranes. In the course of these studies, membrane characterisation was performed using electrochemical quartz crystal microbalance (EQCM) and scanning electron microscopy (SEM). Permeability of the membranes towards divalent cations was explored using a two compartment transport cell. EQCM results demonstrated that the ion exchange behaviour of polypyrrole is dependent on a number of factors including the type of dopant anion present, the type of ions present in the surrounding medium, the scan rate used during the experiment and the previous history of the polymer film. The morphology of PPy films was found to change when the dopant anion was varied and even when the thickness of the film was altered in some cases. In nearly all cases the permeability of the membranes towards metal ions followed the order K+ > Ca2+ > Mn2+. The one exception was PPy(C6S), for which the permeability followed the order Ca2+ ��� K+ > Mn2+ > Co2+ > Cr3+. The above permeability sequences show a strong dependence on the size of the metal ions with metal ions having the smallest hydrated radii exhibiting the highest flux. Another factor that affected the permeability towards metal ions was the thickness of the PPy films. Films with the least thickness showed higher metal ion fluxes. Electrochemical control over ion transport across PPy(CNT) membrane was obtained when films composed of the latter were deposited on track-etched Nucleopore�� membranes as support material. In contrast, the flux of ions across the same film was concentration gradient dependent when the polymer was deposited on polyvinylidene difluoride membranes as support material. However, electrochemical control over metal ion transport was achieved with a bilayer type of PPy film consisting of PPy(pTS)/PPy(CNT), irrespective of the type of support material. In the course of studying macroscopic charge balance during transport experiments performed using a two compartment transport cell, it was observed that PPy films were non-permselective. A clear correlation between the change in pH in the receiving solution and the ions transported across the membrane was observed. A decrease in solution pH was detected when the polymer membrane acted primarily as an anion exchanger, while an increase in pH occurred when it functioned as a cation exchanger. When there was an approximately equal flux of anions and cations across the polymer membrane, the pH in the receiving solution was in the range 6 - 8. These observations suggest that macroscopic charge balance during the transport of cations and anions across polypyrrole membranes was maintained by introduction of anions (OH-) and cations (H+) produced via electrolysis of water.

Determination of chlorophenols from water by solid phase microextraction - ion mobility spectrometry (SPME-IMS)

Chlorophenols have been classified as possible carcinogens for humans. Chlorophenols have been used as pesticides and wood preservatives. In Finland, during 1930 ��� 1980s, saw mills used KY-5 wood preservative that contained 2,4,6-TCP, 2,3,4,6-TeCP and PCP. Especially in Finland chlorophenols have entered the environment by leaking from contaminated grounds of old saw mills. Although chlorophenol concentrations found in environment do not cause acute concern, long term exposure can increase the risk of cancer. SPME is relatively cheap and simple sampling method, in which the sample extraction and concentration are performed in a single step. Solvents are not required in SPME. IMS is based on the detection of sample ion drift times. Based on the drift times, reduced mobilities are calculated, which are comparable despite the measurement conditions. SPME-IMS coupling has not been used earlier in the determination of chlorophenols from water samples. The scope of this work was to study, if SPME-IMS system is suitable for detecting chloro-phenols from water samples. The aim was to determine the most optimal extraction condi-tions, which were then applied to real water samples. Following detection limits were deter-mined: 2,4,6-TCP: 0.33 mg/l; 2,3,4,6-TeCP: 0.63 mg/l and PCP: 1.63 mg/l. Detection limits were high compared to the highest possible chlorophenol concentration that is allowed in Finnish drinking water, 10 ��g/l. Detected concentrations from water sample differed from verified concentrations in the case of 2,3,4,6-TeCP by 4.6 % and in the case of 2,4,6-TCP by 48.4 %. Based on the results it can be said that SPME-IMS setup is suitable for preliminary analysis of mg/l chlorophenol concentrations from water samples.

DFMA Aspects in the Design of a Transfer Line for Off-line Ion Sources

In this thesis, the DFMA is presented and used for the purpose of having a design for a vertical transfer line that can be easily manufactured and assembled. The design of the transfer line, the major components and drawings are presented. The ease of assembly, the costs of manufacturing and differences between the use of steel structure and aluminum are compared. The ALARA principle is followed to minimize the risk of radiation exposure by the means of locating the test ion sources outside the radioactive area.

Modelling of potentiometric ion sensors

Potentiometric ion sensors are a very important subgroup of electrochemical sensors, very attractive for practical applications due to their small size, portability, low-energy consumption, relatively low cost and not changing the sample composition. They are investigated by the researchers from many fields of science. The continuous development of this field creates the necessity for a detailed description of sensor response and the electrochemical processes important in the practical applications of ion sensors. The aim of this thesis is to present the existing models available for the description of potentiometric ion sensors as well as their applicability and limitations. This includes the description of the diffusion potential occurring at the reference electrodes. The wide range of existing models, from most idealised phase boundary models to most general models, including migration, is discussed. This work concentrates on the advanced modelling of ion sensors, namely the Nernst-Planck-Poisson (NPP) model, which is the most general of the presented models, therefore the most widely applicable. It allows the modelling of the transport processes occurring in ion sensors and generating the potentiometric response. Details of the solution of the NPP model (including the numerical methods used) are shown. The comparisons between NPP and the more idealized models are presented. The applicability of the model to describe the formation of diffusion potential in reference electrode, the lower detection limit of both ion-exchanger and neutral carrier electrodes and the effect of the complexation in the membrane are discussed. The model was applied for the description of both types of electrodes, i.e. with the inner filling solution and solidcontact electrodes. The NPP model allows the electrochemical methods other than potentiometry to be described. Application of this model in Electrochemical Impedance Spectroscopy is discussed and a possible use in chrono-potentiometry is indicated. By combining the NPP model with evolutionary algorithms, namely Hierarchical Genetic Strategy (HGS), a novel method allowing the facilitation of the design of ion sensors was created. It is described in detail in this thesis and its possible applications in the field of ion sensors are indicated. Finally, some interesting effects occurring in the ion sensors (i.e. overshot response and influence of anionic sites) as well as the possible applications of NPP in biochemistry are described.

Ion mobility spectrometry in liquid analysis

Ion mobility spectrometry (IMS) is a straightforward, low cost method for fast and sensitive determination of organic and inorganic analytes. Originally this portable technique was applied to the determination of gas phase compounds in security and military use. Nowadays, IMS has received increasing attention in environmental and biological analysis, and in food quality determination. This thesis consists of literature review of suitable sample preparation and introduction methods for liquid matrices applicable to IMS from its early development stages to date. Thermal desorption, solid phase microextraction (SPME) and membrane extraction were examined in experimental investigations of hazardous aquatic pollutants and potential pollutants. Also the effect of different natural waters on the extraction efficiency was studied, and the utilised IMS data processing methods are discussed. Parameters such as extraction and desorption temperatures, extraction time, SPME fibre depth, SPME fibre type and salt addition were examined for the studied sample preparation and introduction methods. The observed critical parameters were extracting material and temperature. The extraction methods showed time and cost effectiveness because sampling could be performed in single step procedures and from different natural water matrices within a few minutes. Based on these experimental and theoretical studies, the most suitable method to test in the automated monitoring system is membrane extraction. In future an IMS based early warning system for monitoring water pollutants could ensure the safe supply of drinking water. IMS can also be utilised for monitoring natural waters in cases of environmental leakage or chemical accidents. When combined with sophisticated sample introduction methods, IMS possesses the potential for both on-line and on-site identification of analytes in different water matrices.

Artificial Ribonucleases: Oligonucleotides Conjugated with Metal Ion Chelates of Azacrowns

Ribonucleic acid (RNA) has many biological roles in cells: it takes part in coding, decoding, regulating and expressing of the genes as well as has the capacity to work as a catalyst in numerous biological reactions. These qualities make RNA an interesting object of various studies. Development of useful tools with which to investigate RNA is a prerequisite for more advanced research in the field. One of such tools may be the artificial ribonucleases, which are oligonucleotide conjugates that sequence-selectively cleave complementary RNA targets. This thesis is aimed at developing new efficient metal-ion-based artificial ribonucleases. On one hand, to solve the challenges related to solid-supported synthesis of metal-ion-binding conjugates of oligonucleotides, and on the other hand, to quantify their ability to cleave various oligoribonucleotide targets in a pre-designed sequence selective manner. In this study several artificial ribonucleases based on cleaving capability of metal ion chelated azacrown moiety were designed and synthesized successfully. The most efficient ribonucleases were the ones with two azacrowns close to the 3��- end of the oligonucleotide strand. Different transition metal ions were introduced into the azacrown moiety and among them, the Zn2+ ion was found to be better than Cu2+ and Ni2+ ions.

Solid-state reference and ion-selective electrodes : towards portable potentiometric sensing

Potentiometric sensors are very attractive tools for chemical analysis because of their simplicity, low power consumption and low cost. They are extensively used in clinical diagnostics and in environmental monitoring. Modern applications of both fields require improvements in the conventional construction and in the performance of the potentiometric sensors, as the trends are towards portable, on-site diagnostics and autonomous sensing in remote locations. The aim of this PhD work was to improve some of the sensor properties that currently hamper the implementation of the potentiometric sensors in modern applications. The first part of the work was concentrated on the development of a solid-state reference electrode (RE) compatible with already existing solid-contact ion-selective electrodes (ISE), both of which are needed for all-solid-state potentiometric sensing systems. A poly(vinyl chloride) membrane doped with a moderately lipophilic salt, tetrabutylammonium-tetrabutylborate (TBA-TBB), was found to show a satisfactory stability of potential in sample solutions with different concentrations. Its response time was nevertheless slow, as it required several minutes to reach the equilibrium. The TBA-TBB membrane RE worked well together with solid-state ISEs in several different situations and on different substrates enabling a miniature design. Solid contacts (SC) that mediate the ion-to-electron transduction are crucial components of well-functioning potentiometric sensors. This transduction process converting the ionic conduction of an ion-selective membrane to the electronic conduction in the circuit was studied with the help of electrochemical impedance spectroscopy (EIS). The solid contacts studied were (i) the conducting polymer (CP) poly(3,4-ethylienedioxythiophene) (PEDOT) and (ii) a carbon cloth having a high surface area. The PEDOT films were doped with a large immobile anion poly(styrene sulfonate) (PSS-) or with a small mobile anion Cl-. As could be expected, the studied PEDOT solid-contact mediated the ion-toelectron transduction more efficiently than the bare glassy carbon substrate, onto which they were electropolymerized, while the impedance of the PEDOT films depended on the mobility of the doping ion and on the ions in the electrolyte. The carbon cloth was found to be an even more effective ion-to-electron transducer than the PEDOT films and it also proved to work as a combined electrical conductor and solid contact when covered with an ion-selective membrane or with a TBA-TBB-based reference membrane. The last part of the work was focused on improving the reproducibility and the potential stability of the SC-ISEs, a problem that culminates to the stability of the standard potential E��. It was proven that the E�� of a SC-ISE with a conducting polymer as a solid contact could be adjusted by reducing or oxidizing the CP solid contact by applying current pulses or a potential to it, as the redox state of the CP solid-contact influences the overall potential of the ISE. The slope and thus the analytical performance of the SC-ISEs were retained despite the adjustment of the E��. The shortcircuiting of the SC-ISE with a conventional large-capacitance RE was found to be a feasible instrument-free method to control the E��. With this method, the driving force for the oxidation/reduction of the CP was the potential difference between the RE and the SC-ISE, and the position of the adjusted potential could be controlled by choosing a suitable concentration for the short-circuiting electrolyte. The piece-to-piece reproducibility of the adjusted potential was promising, and the day-today reproducibility for a specific sensor was excellent. The instrumentfree approach to control the E�� is very attractive considering practical applications.