This thesis presents enhanced analytical methods developed for complex aqueous sample analysis based on solid phase microextraction (SPME). First, the laboratory evaluation of the kinetic calibration approach in aqueous sample analysis using SPME is discussed. A modified SPME device, Polydimethylsiloxane (PDMS) rod passive sampler, was developed and the kinetic calibration method based on the standard preloaded in the extraction phase was applied to determine the time-weighted average (TWA) concentration of organic pollutants in water. Later, the SPME technique was used to investigate the complex interactions between the organic pollutants and humic organic matter (HOM) present in the aqueous samples. The kinetics of the SPME approach in complex aqueous samples was studied. The concentration of freely dissolved analytes and the total concentration of the target analytes in the sample matrix were determined by SPME sampling. The usefulness of the SPME approach for binding studies was further demonstrated by determining the sorption coefficient, a useful parameter for studying the bioavailability of the organic pollutants in the environment. In addition, the commercial Computational Fluid Dynamics (CFD) software COMSOL Multiphysics was used to predict the kinetics of analyte extraction and flow pattern under different experimental conditions using the SPME technique. A good agreement between the prediction and the experimental data confirms the advantages of the CFD application for experimental optimization thus minimizing the need of extensive experiments.

Solid phase microextraction (SPME) has gained much popularity for in vivo applications recently. Thus far, there are two types of pre-equilibrium kinetic calibration that have been applied to in vivo SPME: on-fibre standardization and dominant pre-equilibrium desorption. Both of these techniques have their own advantages and disadvantages. To address the limitations presented by these two techniques, a third pre-equilibrium kinetic calibration method, the diffusion-based interface model, was investigated. The diffusion-based interface model had been successfully applied to air and water samples but was never utilized for in vivo SPME studies. For the first part of the research, on-fibre standardization, dominant pre-equilibrium desorption, and diffusion-based interface model were compared in terms of accuracy, precision, and experimental procedures, by using a flow-through system. These three kinetic calibrations were further validated by equilibrium SPME extraction and protein-plasma precipitation, a current state-of-the-art sampling method. The potential of diffusion-based interface model was yet again demonstrated in the second part of the research project. This calibration method was applied to comparative pharmacokinetic studies of two drugs, fenoterol and methoxyfenoterol, on 5 rats. To provide a constant sampling rate as required for diffusion-based interface model, a SPME animal sampling autosampler, AccuSampler®, was utilized. It custom-written program allowed the entire SPME sampling procedure excluding insertion and removal of SPME probes to be automated. Furthermore, to validate the results obtained by SPME, the AccuSampler® was programmed to withdraw blood after each SPME sampling time point for conventional method analysis using protein-plasma precipitation. The well correlated data obtained by SPME sampling and the conventional method illustrated the potential of diffusion-based interface model as an excellent choice for future in vivo SPME applications.

Although microdialysis (MD) and solid-phase microextraction (SPME) are widely used sampling techniques, a comparison study has not been performed to date. The goal of the research presented was not only to address this issue but also to develop new analytical methods that were more suitable for in vivo study using MD and SPME. A new calibration method called kinetic microdialysis was developed for in vivo sampling. Two MD probes with different flow rates were simultaneously inserted into the symmetric parts of sampling system. A simple empirical equation was proposed to calculate the analyte concentrations in the sample matrix using two different dialysate concentrations. Several factors that influenced the correction factor in this equation were discussed. An excellent correlation was observed between the calculated and theoretical value. This method was subsequently applied for in vivo sampling, for the measurement of pesticide allocation in the different leaves of a jade plant (Crassula ovata). Compared to the other reported MD calibration methods, this novel approach offers several advantages including simplicity, speed, robustness, and increased accuracy. The on-fiber standardization technique for solid-coated SPME was studied and a theoretical model is proposed for the isotropic behavior of adsorption and desorption, based on Fick’s law of diffusion and the Langmuir model. The isotropy of the adsorption and desorption of analytes onto and from the surface of porous solid SPME fiber was validated with the use of a commercially available fiber, a 50 um carbowax/templated resin (CW/TPR) for carbamate pesticide analysis in various in vitro sample matrices. Time constants were comparable for the adsorption and desorption processes. Equilibrium constants and fiber capacities were calculated with the Langmuir Isotherm Model. A kinetic method was developed to calibrate adsorption using desorption. This calibration corrected for the sample matrix effects and minimized displacement effects as a pre-equilibrium extraction. The technique was successfully applied to the analysis of pesticides in river water and white wine. This developed method could be potentially applied for in vivo study. A new kinetic calibration was developed using dominant pre-equilibrium desorption by SPME. The calibration was based on isotropism between absorption and desorption, which was proved theoretically and experimentally in an aqueous solution and semi-solid matrix. This approach allows for the calibration of absorption using desorption to compensate for matrix effects. Moreover, concentration profiles are initially proposed to verify isotropism between the absorption and desorption, while providing a linear approach to obtain time constants for the purpose of quantitative analysis. This linear approach is more convenient, robust and accurate than the non-linear version with the previously used time profiles. Furthermore, the target analytes are used as the internal standards, thus radioactive or deuterated internal standards are not necessary. In addition, dominant pre-equilibrium desorption utilizes the pre-equilibrium approach and offers a shorter sample preparation time, which is typically suitable for in vivo sampling. This kinetic calibration method was successfully applied to prepare samples of polycyclic aromatic hydrocarbons (PAHs) in a flow-through system and in vivo pesticide sampling in a jade plant (Crassula ovata). Previous field studies utilizing SPME predominantly focused on volatile compounds in air or water. Earlier in vivo sampling studies utilizing SPME were limited to liquid matrices, namely blood. In this study, SPME was developed for in vivo laboratory and field sampling of pharmaceuticals in fish muscle. Pre-equilibrium extraction was used to shorten in vivo sampling time. The use of pre-equilibrium desorption rates are proposed as a means to calibrate pre-equilibrium extractions. Excellent linearity was found between the free concentrations determined by SPME from the muscle of living fish and the waterborne concentrations of several pharmaceuticals. It is also firstly proposed a simple SPME method to determine free and total concentrations simultaneously in a living tissue using the known protein binding value. The utility of in vivo SPME sampling under field conditions was evaluated in wild fish collected from a number of different river locations under varying degrees of influence from municipal wastewater effluents. Diphenhydramine and diltiazem were detected in the muscle of fish downstream of a local wastewater treatment plant. Based on this study, SPME technique has demonstrated several important advantages for laboratory and field in vivo sampling. The development of a rapid, robust, easy to deploy technique which combines sampling, extraction and concentration into one step is a potentially important tool for use in vivo field-based sampling. MD and SPME methods have been developed and compared through in vitro and in vivo study. For in vitro study (juice, milk and orange jelly), both methods offered accurate and precise results (recovery: 88-105% with RSD < 15%) for complex sample matrices by standard addition method. The limits of quantification (LOQs) of the two methods developed were below the tolerance levels in milk set by the United Nations Food and Agriculture Organization (FAO). Compared to MD, the fully automated SPME procedure offered several advantages including high-throughput and more efficient sampling, less labor intensity, and capability for batch analysis. For in vivo study, kinetic calibrations were performed using retrodialysis and in-fiber standardization techniques for MD and SPME, respectively. Quantitative analysis was performed to measure pesticide concentrations in living tissue, i.e., the leaves of a living jade plant (Crassula ovata). Although both techniques provided sampling with minimal perturbation to the system under study, SPME was more sensitive, precise and accurate, suitable for field sampling and had a wider application than MD. It demonstrated that SPME has the potential to replace MD for in vivo study.

This thesis presents enhanced analytical methods developed for complex aqueous sample analysis based on solid phase microextraction (SPME). First, the laboratory evaluation of the kinetic calibration approach in aqueous sample analysis using SPME is discussed. A modified SPME device, Polydimethylsiloxane (PDMS) rod passive sampler, was developed and the kinetic calibration method based on the standard preloaded in the extraction phase was applied to determine the time-weighted average (TWA) concentration of organic pollutants in water. Later, the SPME technique was used to investigate the complex interactions between the organic pollutants and humic organic matter (HOM) present in the aqueous samples. The kinetics of the SPME approach in complex aqueous samples was studied. The concentration of freely dissolved analytes and the total concentration of the target analytes in the sample matrix were determined by SPME sampling. The usefulness of the SPME approach for binding studies was further demonstrated by determining the sorption coefficient, a useful parameter for studying the bioavailability of the organic pollutants in the environment. In addition, the commercial Computational Fluid Dynamics (CFD) software COMSOL Multiphysics was used to predict the kinetics of analyte extraction and flow pattern under different experimental conditions using the SPME technique. A good agreement between the prediction and the experimental data confirms the advantages of the CFD application for experimental optimization thus minimizing the need of extensive experiments.

Solid phase microextraction (SPME) has gained much popularity for in vivo applications recently. Thus far, there are two types of pre-equilibrium kinetic calibration that have been applied to in vivo SPME: on-fibre standardization and dominant pre-equilibrium desorption. Both of these techniques have their own advantages and disadvantages. To address the limitations presented by these two techniques, a third pre-equilibrium kinetic calibration method, the diffusion-based interface model, was investigated. The diffusion-based interface model had been successfully applied to air and water samples but was never utilized for in vivo SPME studies. For the first part of the research, on-fibre standardization, dominant pre-equilibrium desorption, and diffusion-based interface model were compared in terms of accuracy, precision, and experimental procedures, by using a flow-through system. These three kinetic calibrations were further validated by equilibrium SPME extraction and protein-plasma precipitation, a current state-of-the-art sampling method. The potential of diffusion-based interface model was yet again demonstrated in the second part of the research project. This calibration method was applied to comparative pharmacokinetic studies of two drugs, fenoterol and methoxyfenoterol, on 5 rats. To provide a constant sampling rate as required for diffusion-based interface model, a SPME animal sampling autosampler, AccuSampler®, was utilized. It custom-written program allowed the entire SPME sampling procedure excluding insertion and removal of SPME probes to be automated. Furthermore, to validate the results obtained by SPME, the AccuSampler® was programmed to withdraw blood after each SPME sampling time point for conventional method analysis using protein-plasma precipitation. The well correlated data obtained by SPME sampling and the conventional method illustrated the potential of diffusion-based interface model as an excellent choice for future in vivo SPME applications.

The traditional approach for predicting the risk of hydrophobic organic contaminants in sediment is to relate organic carbon normalized sediment concentrations to body residues or toxic effects in organisms. This method is limited, however due to the plethora of variables that can influence bioavailability. Therefore, a matrix independent method of predicting bioavailability needs to be developed in order to be universally applicable. Solid phase microextraction (SPME) and Tenax are two commonly used bioavailability-based methods. While both SPME fiber and Tenax extractable concentrations can be correlated to tissue residues of aquatic species, the majority of this research (with a few exceptions) focuses on compounds that are not acutely toxic or biotransformed. Less is known about the potential applicability of these methods to predict bioaccumulation, and ultimately toxicity, for highly toxic, rapidly biotransformed compounds, such as pyrethroid insecticides. This class of compounds is of particular concern due to frequent environmental detection in sediments at concentrations lethal to benthic species. This research has four specific goals: Determining exposure conditions that may change the concentration on the SPME fibers at equilibrium (Chapter 2); Comparing the ability of SPME fibers and Tenax to predict the bioavailability of two pyrethroids (permethrin and bifenthrin) (Chapter 3); Developing bioavailability-based toxicity endpoints for bifenthrin using two aquatic species (Chapter 4); and, Validating these techniques using sediments from known contaminated field sites (Chapter 5). Overall this research was focused on comparing and contrasting the ability and applicability of SPME fibers and Tenax to adequately predict the exposure of pyrethroids under varying conditions. While comparing these two methods, they were optimized to better provide accurate predictions of bioavailability and toxicity for pyrethroids from sediments. Regardless of the fiber or animal density examined, the SPME fibers exposure did not significantly affect fiber concentrations for permethrin or DDE. Additionally, bioaccumulation of parent permethrin and bifenthrin was predicted using both SPME fibers and Tenax using 6 or 24 h extraction times. Further, a single regression model predicted bioaccumulation across compounds and species using Tenax extractable concentrations. Once demonstrated that these techniques could predict bioaccumulation, median lethal and effect levels were examined for bifenthrin and as expected the bioavailability-based endpoints were more uniform across sediments than use of whole sediment concentrations. Additionally, the relationships among the two methods were compared across multiple sediments. Despite the SPME fiber's ability to determine toxicity in laboratory sediments, the field validation study determined that lethal levels were often too low to detect on the SPME fibers using current methodologies, but Tenax extractable concentrations correlated to toxicity. Overall, while both methods could predict bioavailability, the limitations of SPME fibers including lower sensitivity, inability to function across compounds, and long equilibration time, made Tenax extraction a preferable method.

This thesis project describes research using headspace solid phase micro-extraction with gas chromatography (HS-SPME GC-MS) as an analytical tool for assessing textile fibres. It was found that this method required a temperature of >500oC to pyrolize the textile sample. A total of 5 minutes was determined to be the optimal time for collecting the volatile analytes. Numerous analytes were found to be chemical markers for each of the individual textile fibres. The chemical markers are qualitatively used to describe each textile uniquely, and it was found that by using the chromatographic patterns, the textiles could be identified individually and in mixtures containing two textiles. Lastly, by accelerating the age of the textile fibres by means of heat, ultra-violet light, and humidity, a comparison was made between the un-aged and aged fibres. It was found that each of the techniques arose different results and in some cases new compounds. / October 2016

New liquid phase microextraction (LPME) has been optimized. Plastic adapter with tapered tip was used as extraction device. Concentration of analytes was determined by GC-MS. Face centered design was used to optimize LPME and the results were evaluated by Minitab 16 programme. Volume of sample, volume of extraction solvent, stirring rate, extraction time, ionic strength and time after microextraction were optimized. Response of system was defined as the sum of the peak relative areas. Toluene, tetrachlorethylene, ethylbenzene, xylenes, mesitylene and naphthalene were the studied analytes. Methylhexadecanoate was used as an internal standard. Optimal system conditions were as follows: 20 mL sample volume, 300 μL extraction solvent volume, 20 minutes, stirring speed 700 rpm, no addition of salt, and time after microextraction 3.5 minutes. Determination coefficient was 0.9700 and the lack-of-fit was insignificant which indicated good agreement of the model with the experimental data. The preconcentration factor ranged from 26 (tetrachlorethylene) to 39 (xylenes). The microextraction yield was varied from 39.5% (tetrachlorethylene) to 59.1% (p-xylene and m-xylene). The new method was tested by analyzing real samples of tap water, river water and water from the sewage treatment plant. The samples were...

A necessidade de metodologias adequadas para análise de fármacos e seus metabólitos em matrizes biológicas complexas levaram a um crescente interesse no desenvolvimento de novas técnicas de preparação de amostras, particularmente as técnicas de microextração, por serem altamente seletivas e requererem o consumo mínimo de solventes orgânicos. Aliado a esses avanços, o emprego de modernas e eficientes tecnologias analíticas, como a eletroforese capilar (CE) e a cromatografia líquida de alta eficiência acoplada à espectrometria de massas (LC-MS-MS), tem resultado em um considerável avanço em qualidade nas metodologias analíticas disponíveis para bioanálises. Dentro desse cenário, destaca-se a utilização dessas técnicas para o desenvolvimento de metodologias enantiosseletivas, permitindo quantificar os enantiômeros de fármacos administrados como racematos. Sendo assim, propusemos o desenvolvimento e a validação de metodologias enantiosseletivas para a análise dos enantiômeros da mirtazapina (MRT) e de seus principais metabólitos em plasma e urina, utilizando a CE e a LC-MS-MS. Para a preparação das amostras foram empregadas a microextração em fase sólida (SPME) e a microextração em fase líquida (LPME). No primeiro método desenvolvido, a LPME foi utilizada para extrair os analitos das amostras de plasma (1 mL), previamente diluídas, alcalinizadas com 3,0 mL de uma solução tampão fosfato 0,5 mol L-1 (pH 8) e adicionadas de 15% (m/v) de cloreto de sódio. Éter n-hexílico e uma solução de ácido acético 0,01 moL L-1 foram utilizados como solvente extrator e fase aceptora, respectivamente. As análises cromatográficas foram feitas em uma coluna Chiralpak AD-RH, empregando acetonitrila:metanol:etanol (98:1:1, v/v/v) mais 0,2% de dietilamina como fase móvel, na vazão de 1 mL min-1. A detecção dos analitos foi conduzida por LC-MS-MS usando um analisador triplo-quadrupolo e ionização por eletrospray positivo. Nessas condições, foram obtidas recuperações de 18,3 a 45,5%, resposta linear na faixa de concentração de 1,25-125 ng mL-1 e limite de quantificação (LQ) de 1,25 ng mL-1 para todos os enantiômeros avaliados. Posteriormente, a CE e a LPME foram utilizadas para a análise da MRT e seus principais metabólitos em urina. Antes da extração, amostras de urina (1 mL) foram submetidas a hidrólise enzimática a 37 ºC por 16 horas. Então, a enzima foi precipitada com ácido tricloroacético, o pH foi ajustado para 8 com uma solução tampão fosfato 0,5 mol L-1 (pH 11) e 10% de NaCl também foi adicionado. Em seguida as amostras foram submetidas a extração de forma similar aquela realizada para as amostras de plasma. As análises eletroforéticas foram obtidas em uma solução tampão fosfato 50 mmol L-1 (pH 2,5) contendo 0,55% (m/v) de carboximetil-b-ciclodextrina (CM-b-CD). O método foi linear na faixa de concentração de 62,5-2500 ng mL-1 para cada enantiômero da MRT e 8-hidroximirtazapina (8-OHM) e 62,5-1250 ng mL-1 para cada enantiômero da desmetilmirtazapina (DMR). O LQ foi 62,5 ng mL-1 para todos os enantiômeros. A SPME também foi utilizada no desenvolvimento de um método para a determinação simultânea do fármaco e seus metabólitos em urina usando CE e LC-MS-MS. Os analitos de interesse foram transferidos da solução aquosa hidrolisada para uma fibra de polidimetilsiloxano-divinilbenzeno (PMDS-DVB) e então foram desorvidos em metanol. As recuperações médias foram de 12 % para os enantiômeros da MRT, 3,8 % para a DMR e 0,72 % para a 8-OHM. O método foi linear na faixa de concentração de 62,5-2500 ng mL-1 com adequado LQ (62,5 ng mL-1) para todos os enantiômeros. A precisão e exatidão foram menores que 15% para todos os métodos desenvolvidos. Além disso, os métodos foram adequadamente aplicados em estudos preliminares de determinação dos enantiômeros da MRT, 8-OHM e DMR em amostras de plasma e urina obtidos após a administração oral de uma dose única de rac-MRT a voluntários sadios. / The need for appropriate methodology for the analysis of drugs and their metabolites in complex biological matrices led to a growing interest in developing new techniques for sample preparation, particularly microextraction techniques because they are highly selective and require a minimum consumption of organic solvents. Allied to these developments, the employment of modern and efficient analytical technologies, such as capillary electrophoresis (CE) and high-performance liquid chromatography coupled to mass spectrometry (LC-MS-MS), has resulted in a considerable improvement in quality in the analytical methodologies available for bioanalysis. In this context, it is worth to mention the use of such techniques to develop enantioselective methodologies, allowing the quantification of the enantiomers of drugs administered as racemates. Therefore, we proposed the development and validation of enantioselective methodologies for the analysis of the enantiomers of mirtazapine (MRT) and of its main metabolites in plasma and urine, using the CE and LC-MS-MS. Solid phase microextraction (SPME) and liquid phase microextraction (LPME) were used for sample preparation. In the first method, LPME was used to extract the analytes from plasma samples (1 ml), previously diluted, alkalinized with 3.0 mL 0.5 mol L-1 pH 8 phosphate buffer solution and supplemented with 15% (w/v) sodium chloride. N-hexyl ether and 0.01 mol L-1 acetic acid solution were used as solvent extractor and acceptor phase, respectively. The analyses were carried out on a CHIRALPAK AD-RH column and acetonitrile: methanol: ethanol (98:1:1, v / v / v) plus 0.2% of diethylamine was used as mobile phase, at a flow rate of 1 mL min-1. The detection was performed by LC-MS-MS equipped with a triple-quadrupole analyzer and ionization by eletrospray positive. Under these conditions, recoveries were from 18.3 to 45.5%; linear response over the 1,25-125 ng ml-1 concentration range and limit of quantification (LOQ) of 1.25 ng ml-1 for all enantiomers evaluated were obtained. CE and LPME were also used for the analysis of MRT and its main metabolites in urine. Before the extraction, urine samples (1 mL) were submitted to enzymatic hydrolysis at 37 ºC for 16 hours, the enzyme was precipitated with trichloroacetic acid, the pH was adjusted to 8 with 0.5 mol L-1 phosphate buffer solution (pH 11) and 10% (w/v) sodium chloride was further added. Then, the LPME extraction was performed according to the procedure previously developed. The electrophoretic analyses were carried out in 50 mmol L-1 phosphate buffer solution (pH 2.5) containing 0.55% (w/v) carboxymethyl-b-cyclodextrin (CM-b-CD). The method was linear over the concentration range of 62.5-2500 ng mL-1 for each MRT and 8-OHM enantiomer and 62.5-1250 ng mL-1 for each DMR enantiomer. The quantification limit (LOQ) was 62.5 ng mL-1 for all the enantiomers. A SPME method was also developed for the simultaneous enantioselective determination of MRT and its metabolites in urine using CE and LC-MS-MS. The target analytes were transferred from the hydrolyzed aqueous solution to the polydimetylsiloxane-divinylbenzene (PMDS-DVB) fiber coating and then desorbed in methanol. The means recoveries were 12 % for the enantiomers of MRT, 3.8 % for DMR and 0.72 % for 8-OHM. The method was linear over the concentration range of 62.5-2500 ng mL-1 with suitable LOQ (62.5 ng mL-1) for all the enantiomers. The precision and accuracy were lower than 15% for all developed methods. Moreover, the methods were successfully employed for the determination of MRT, 8-OHM and DMR enantiomers in plasma and urine samples obtained after oral administration of a single dose of rac-MRT to healthy volunteers.

Sample preparation is a key step in chemical analysis, and includes isolation of target analytes, removal of interferences, preconcentration, and/or modification of target analytes (if needed). Sample preparation is also the most time-consuming and error-prone step in the whole analytical process. Traditional sample preparation techniques involve hazardous solvents. Considering the environmental and health safety, it is desirable to reduce or eliminate organic solvents in sample preparation. Solid phase microextraction (SPME) was introduced as a solvent free sample preparation technique. Capillary microextraction (CME) is one of the formats of SPME that can be easily coupled to high performance liquid chromatography (HPLC). In SPME and CME a solvent free sample preparation is accomplished by using a sorbent coating instead of hazardous organic solvents commonly used in conventional extraction techniques. This research is focused on the development and systematic examination of novel niobia-, titania- and silica-based organic-inorganic hybrid sol-gel sorbents for CME. Conventionally silica and titania based precursors were used in organi-inorganic hybrid sol-gel sorbents for CME, here novel niobia based precursor was used in creating organic-inorganic hybrid sol-gel sorbents. Poly tetrahydrofuran (polyTHF) as well as electrically neutral and charged organic ligands were used to prepare the sorbents for CME coupled to HPLC. Characterization of created sol-gel sorbents, evaluation of extraction performance, and enrichment of environmentally and biomedically important analytes including organophosphorus compounds were performed. CME performances of the created sorbents were characterized by specific extraction (SE) (a measure of extraction efficiency) and desorption efficiency (DE) (a measure of completeness desorption of extracted analytes). Scientific findings of this research has shown that sol-gel niobia-polyTHF sorbent provides 60 to 70 % higher SE values for different environmentally important analytes compared to analogously prepared silica-polyTHF sorbent. This superior extraction performance can be attributed to the presence of surface Lewis acid sites undergoing Lewis acid-base interactions with analytes representing Lewis bases. The prepared sorbents also have the ability to undergo van der Waals interactions due to the presence of polyTHF. Absence of Lewis acid sites on silica surface resulted in inferior extraction efficiency compared to niobia-polyTHF sorbents. Extraction efficiency of the created sol-gel based niobia-polyTHF was also explored in the enrichment of organophosphorus pesticides and compared with that of the state-of-the-art titania-based sorbent. Sol-gel niobia-polyTHF sorbent has provided 40 to 50 % higher SE values in the enrichment of organophosphorus pesticides compared to sol-gel titania-polyTHF sorbent which can be attributed to the presence of bronsted acid sites on niobia surface (but lacking on titania) along with Lewis acid sites. To explore relative contributions of electrostatic, Lewis acid-base and van der Waals interactions between sol-gel sorbents and analytes, two sol-gel sorbents, one containing a positively charged octadecyl ligand and the other a neutral octadecyl ligand were created. Positive charge was imparted by using N-octadecyldimethyl [3-(trimethoxysilyl) propyl] ammonium chloride (C18 (+ve)) as ligand bearing co-precursor. Similarly N-octadecyl trimethoxysilane was used to impart a neutral C18 ligand in sol-gel coating. Experimental results have shown that sol-gel Nb2O5-C18 (+ve) sorbent has superior extraction efficiency compared to sol-gel based Nb2O5-C18 and purely inorganic Nb2O5 sorbents in enrichment of organophosphorus compounds (nucleotides and organophosphorus pesticides). Electrostatic interactions between the positive charge of organic ligand (C18 (+ve)) and negative charge of phosphate group has contributed to the higher extraction performance of sol-gel based Nb2O5-C18 (+ve) sorbent. TiO2-C18 (+ve) sorbent was also created to compare with the novel sol-gel niobia based sorbents, since titania-based sorbents are considered as the state-of-the-art extraction material in the enrichment of organophosphorus compounds. Established research results has shown that sol-gel based Nb2O5-C18 (+ve) sorbent has provided 40 to 50 % higher specific extraction values for organophosphorus compounds compared to sol-gel based TiO2-C18 (+ve) sorbent. Desorption efficiency of sol-gel Nb2O5-C18 (+ve) and TiO2-C18 (+ve) sorbents were 96% vs 90%. This superior DE of sol-gel Nb2O5-C18 (+ve) sorbent can be attributed the higher Lewis acid strength of titania than nioiba. The developed sol-gel niobia based sorbents have also shown high pH stability compared to traditional sol-gel silica based sorbents. The created sol-gel sorbents were characterized by less than 5% run to run RSD values and also less than 5% capillary to capillary RSD values which indicated the high reproducibility of developed method. The developed sol-gel niobia sorbents are applicable to sample preparation in different fields including biomedical, environmental, forensic, defense etc.