Analytical functions for the calculation of hyperspherical potential curves of atomic systems

We present angular basis functions for the Schrödinger equation of two-electron systems in hyperspherical coordinates. By using the hyperspherical adiabatic approach, the wave functions of two-electron systems are expanded in analytical functions, which generalizes the Jacobi polynomials. We show that these functions, obtained by selecting the diagonal terms of the angular equation, allow efficient diagonalization of the Hamiltonian for all values of the hyperspherical radius. The method is applied to the determination of the 1S e energy levels of the Li + and we show that the precision can be improved in a systematic and controllable way. ©2000 The American Physical Society.

The institutionality of gender in the State: new analytical perspectives

Includes bibliography

Measurements of labile Cd, Cu, Ni, Pb, and Zn levels at a northeastern Brazilian coastal area under the influence of oil production with diffusive gradients in thin films technique (DGT)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A simple method based on ICP-MS for estimation of background levels of arsenic, cadmium, copper, manganese, nickel, lead, and selenium in blood of the Brazillian population

Throughout the world, biomonitoring has become the standard for assessing exposure of individuals to toxic elements as well as for responding to serious environmental public health problems. However, extensive biomonitoring surveys require rapid and simple analytical methods. Thus, a simple and high-throughput method is proposed for the determination of arsenic (As), cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb), and selenium (Se) in blood samples by using inductively coupled plasma–mass spectrometry (ICPMS). Prior to analysis, 200 ml of blood samples was mixed with 500 ml of 10% v/v tetramethylammonium hydroxide (TMAH) solution, incubated for 10 min, and subsequently diluted to 10 ml with a solution containing 0.05% w/v ethylenediamine tetraacetic acid (EDTA) + 0.005% v/v Triton X-100. After that, samples were directly analyzed by ICP-MS (ELAN DRC II). Rhodium was selected as an internal standard with matrix-matching calibration. Method detection limits were 0.08, 0.04, 0.5, 0.09, 0.12, 0.04, and 0.1 mg//L for As, Cd, Cu, Mn, Ni, Pb, and Se, respectively. Validation data are provided based on the analysis of blood samples from the trace elements inter-\comparison program operated by the Institut National de Santé Publique du Quebec, Canada. Additional validation was provided by the analysis of human blood samples by the proposed method and by using electrothermal atomic absorption spectrometry (ETAAS). The method was subsequently applied for the estimation of background metal blood values in the Brazilian population. In general, the mean concentrations of As, Cd, Cu, Mn, Ni, Pb, and Se in blood were 1.1, 0.4, 890, 9.6, 2.1, 65.4, and 89.3 mg/L, respectively, and are in agreement with other global populations. Influences of age, gender, smoking habits, alcohol consumption, and geographical variation on the values were also considered. Smoking habits influenced the levels of Cd in blood. The levels of Cu, Mn, and Pb were significantly correlated with gender, whereas Cu and Pb were significantly correlated with age. There were also interesting differences in Mn and Se levels in the population living in the north of Brazil compared to the south.

Analytical method for determination of nitric oxide in zebrafish larvae: Toxicological and pharmacological applications

Zebrafish are currently used at various stages of the drug discovery process and can be a useful and cost-effective alternative to some mammalian models. Nitric oxide (NO) plays an important role in physiology of zebrafish. The availability of appropriate analytical techniques to quantify the NO is crucial for studying its role in physiological and pathological conditions. This work aimed at establishing a high-performance liquid chromatography method for determination of NO levels in zebrafish larvae. Attempts were also made to assess the normal levels of NO at the first days postfertilization and the possible changes under pathological conditions. The method validation was quantitatively evaluated in terms of sensitivity, specificity, precision, accuracy, linearity, and recovery. NO levels from zebrafish larvae at the first days postfertilization and larvae challenged to N(G)-nitro-L-arginine methyl ester, sodium nitroprusside, Escherichia coil lipopolysaccharide, and copper sulfate were analyzed. The samples were derivatized with 2,3-diaminonaphthalene, and fluorescence detection was used for the indirect determination of NO. The method showed a good performance for all validation parameters evaluated and was efficient to monitor changes in NO concentration under physiological and pathophysiological conditions. This method might represent a powerful tool to be applied in NO studies with zebrafish larvae. (C) 2011 Elsevier Inc. All rights reserved.

Tributyltin in Crustacean Tissues: Analytical Performance and Validation of Method

The hermit crab Clibanarius vittatus is a typical organism from intertidal regions being considered as a good bioindicator of tributyltin presence at these environments. Thus this study presents the analytical performance and validation method for TBT quantification in tissues of C. vittatus by gas chromatography with pulsed flame photometric detector (GC-PFPD) after extraction with an apolar solvent (toluene) and Grignard derivatization. The limits of detection of the method (LOD) were 2.0 and 2.8 ng g(-1) for TBT and DBT (dibutyltin), respectively, and its limits of quantification (LOQ) were 6.6 and 8.9 ng g(-1) for TBT and DBT, respectively. The method was applied to samples from Santos Estuary, Sao Paulo State, Brazil. TBT and DBT concentrations ranged from 26.7 to 175.0 ng g(-1) and from 46.2 to 156.0 ng g(-1), respectively. These concentrations are worrisome since toxic effects (such as endocrine disruption) have been reported for other organisms even under lower levels of registred at this study.

GaMnAs: Position of Mn-d levels and majority spin band gap predicted from GGA-1/2 calculations

Among all magnetic semiconductors, GaMnAs seems to be the most important one. In this work, we present accurate first-principles calculations of GaMnAs within the GGA-1/2 approach: We concentrate our efforts in obtaining the position of the peak of Mn-d levels in the valence band and also the majority spin band gap. For the position of the Mn-d peak, we find a value of 3.3 eV below the Fermi level, in good agreement with the most recent experimental results of 3.5 and 3.7 eV. An analytical expression that fits the calculated E-g(x) for majority spin is derived in order to provide ready access to the band gap for the composition range from 0 to 0.25. We found a value of 3.9 eV for the gap bowing parameter. The results agree well with the most recent experimental data. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4718602]

Tributyltin in crustacean tissues: analytical performance and validation of method

The hermit crab Clibanarius vittatus is a typical organism from intertidal regions being considered as a good bioindicator of tributyltin presence at these environments. Thus this study presents the analytical performance and validation method for TBT quantification in tissues of C. vittatus by gas chromatography with pulsed flame photometric detector (GC-PFPD) after extraction with an apolar solvent (toluene) and Grignard derivatization. The limits of detection of the method (LOD) were 2.0 and 2.8 ng g-1 for TBT and DBT (dibutyltin), respectively, and its limits of quantification (LOQ) were 6.6 and 8.9 ng g-1 for TBT and DBT, respectively. The method was applied to samples from Santos Estuary, São Paulo State, Brazil. TBT and DBT concentrations ranged from 26.7 to 175.0 ng g-1 and from 46.2 to 156.0 ng g-1, respectively. These concentrations are worrisome since toxic effects (such as endocrine disruption) have been reported for other organisms even under lower levels of registred at this study.

Isocyanates and Amines – Sampling and Analytical Procedures

This thesis covers sampling and analytical procedures for isocyanates (R-NCO) and amines (R-NH2), two kinds of chemicals frequently used in association with the polymeric material polyurethane (PUR). Exposure to isocyanates may result in respiratory disorders and dermal sensitisation, and they are one of the main causes of occupational asthma. Several of the aromatic diamines associated with PUR production are classified as suspected carcinogens. Hence, the presence of these chemicals in different exposure situations must be monitored. In the context of determining isocyanates in air, the methodologies included derivatisation with the reagent di-n-butylamine (DBA) upon collection and subsequent determination using liquid chromatography (LC) and mass spectrometric detection (MS). A user-friendly solvent-free sampler for collection of airborne isocyanates was developed as an alternative to a more cumbersome impinger-filter sampling technique. The combination of the DBA reagent together with MS detection techniques revealed several new exposure situations for isocyanates, such as isocyanic acid during thermal degradation of PUR and urea-based resins. Further, a method for characterising isocyanates in technical products used in the production of PUR was developed. This enabled determination of isocyanates in air for which pure analytical standards are missing. Tandem MS (MS/MS) determination of isocyanates in air below 10-6 of the threshold limit values was achieved. As for the determination of amines, the analytical methods included derivatisation into pentafluoropropionic amide or ethyl carbamate ester derivatives and subsequent MS analysis. Several amines in biological fluids, as markers of exposure for either the amines themselves or the corresponding isocyanates, were determined by LC-MS/MS at amol level. In aqueous extraction solutions of flexible PUR foam products, toluene diamine and related compounds were found. In conclusion, this thesis demonstrates the usefulness of well characterised analytical procedures and techniques for determination of hazardous compounds. Without reliable and robust methodologies there is a risk that exposure levels will be underestimated or, even worse, that relevant compounds will be completely missed.

Innovative analytical methods for Central Nervous System Drug analysis in biological fluids

During recent years a consistent number of central nervous system (CNS) drugs have been approved and introduced on the market for the treatment of many psychiatric and neurological disorders, including psychosis, depression, Parkinson disease and epilepsy. Despite the great advancements obtained in the treatment of CNS diseases/disorders, partial response to therapy or treatment failure are frequent, at least in part due to poor compliance, but also genetic variability in the metabolism of psychotropic agents or polypharmacy, which may lead to sub-therapeutic or toxic plasma levels of the drugs, and finally inefficacy of the treatment or adverse/toxic effects. With the aim of improving the treatment, reducing toxic/side effects and patient hospitalisation, Therapeutic Drug Monitoring (TDM) is certainly useful, allowing for a personalisation of the therapy. Reliable analytical methods are required to determine the plasma levels of psychotropic drugs, which are often present at low concentrations (tens or hundreds of nanograms per millilitre). The present PhD Thesis has focused on the development of analytical methods for the determination of CNS drugs in biological fluids, including antidepressants (sertraline and duloxetine), antipsychotics (aripiprazole), antiepileptics (vigabatrin and topiramate) and antiparkinsons (pramipexole). Innovative methods based on liquid chromatography or capillary electrophoresis coupled to diode-array or laser-induced fluorescence detectors have been developed, together with the suitable sample pre-treatment for interference removal and fluorescent labelling in case of LIF detection. All methods have been validated according to official guidelines and applied to the analysis of real samples obtained from patients, resulting suitable for the TDM of psychotropic drugs.

Development of original analytical methods for the therapeutic drug monitoring of CNS druges: Antipsychotics, Antidepressants and Anxiolytics-hypnotics

Great strides have been made in the last few years in the pharmacological treatment of neuropsychiatric disorders, with the introduction into the therapy of several new and more efficient agents, which have improved the quality of life of many patients. Despite these advances, a large percentage of patients is still considered “non-responder” to the therapy, not drawing any benefits from it. Moreover, these patients have a peculiar therapeutic profile, due to the very frequent application of polypharmacy, attempting to obtain satisfactory remission of the multiple aspects of psychiatric syndromes. Therapy is heavily individualised and switching from one therapeutic agent to another is quite frequent. One of the main problems of this situation is the possibility of unwanted or unexpected pharmacological interactions, which can occur both during polypharmacy and during switching. Simultaneous administration of psychiatric drugs can easily lead to interactions if one of the administered compounds influences the metabolism of the others. Impaired CYP450 function due to inhibition of the enzyme is frequent. Other metabolic pathways, such as glucuronidation, can also be influenced. The Therapeutic Drug Monitoring (TDM) of psychotropic drugs is an important tool for treatment personalisation and optimisation. It deals with the determination of parent drugs and metabolites plasma levels, in order to monitor them over time and to compare these findings with clinical data. This allows establishing chemical-clinical correlations (such as those between administered dose and therapeutic and side effects), which are essential to obtain the maximum therapeutic efficacy, while minimising side and toxic effects. It is evident the importance of developing sensitive and selective analytical methods for the determination of the administered drugs and their main metabolites, in order to obtain reliable data that can correctly support clinical decisions. During the three years of Ph.D. program, some analytical methods based on HPLC have been developed, validated and successfully applied to the TDM of psychiatric patients undergoing treatment with drugs belonging to following classes: antipsychotics, antidepressants and anxiolytic-hypnotics. The biological matrices which have been processed were: blood, plasma, serum, saliva, urine, hair and rat brain. Among antipsychotics, both atypical and classical agents have been considered, such as haloperidol, chlorpromazine, clotiapine, loxapine, risperidone (and 9-hydroxyrisperidone), clozapine (as well as N-desmethylclozapine and clozapine N-oxide) and quetiapine. While the need for an accurate TDM of schizophrenic patients is being increasingly recognized by psychiatrists, only in the last few years the same attention is being paid to the TDM of depressed patients. This is leading to the acknowledgment that depression pharmacotherapy can greatly benefit from the accurate application of TDM. For this reason, the research activity has also been focused on first and second-generation antidepressant agents, like triciclic antidepressants, trazodone and m-chlorophenylpiperazine (m-cpp), paroxetine and its three main metabolites, venlafaxine and its active metabolite, and the most recent antidepressant introduced into the market, duloxetine. Among anxiolytics-hypnotics, benzodiazepines are very often involved in the pharmacotherapy of depression for the relief of anxious components; for this reason, it is useful to monitor these drugs, especially in cases of polypharmacy. The results obtained during these three years of Ph.D. program are reliable and the developed HPLC methods are suitable for the qualitative and quantitative determination of CNS drugs in biological fluids for TDM purposes.

New analytical LC-mass spectrometry methodologies for the quali-quantitative determination of natural substances and drugs in complex matrices

This thesis reports an integrated analytical and physicochemical approach for the study of natural substances and new drugs based on mass spectrometry techniques combined with liquid chromatography. In particular, Chapter 1 concerns the study of Berberine a natural substance with pharmacological activity for the treatment of hepatobiliary and intestinal diseases. The first part focused on the relationships between physicochemical properties, pharmacokinetics and metabolism of Berberine and its metabolites. For this purpose a sensitive HPLC-ES-MS/MS method have been developed, validated and used to determine these compounds during their physicochemical properties studies and plasma levels of berberine and its metabolites including berberrubine(M1), demethylenberberine(M3), and jatrorrhizine(M4) in humans. Data show that M1, could have an efficient intestinal absorption by passive diffusion due to a keto-enol tautomerism confirmed by NMR studies and its higher plasma concentration. In the second part of Chapter 1, a comparison between M1 and BBR in vivo biodistribution in rat has been studied. In Chapter 2 a new HPLC-ES-MS/MS method for the simultaneous determination and quantification of glucosinolates, as glucoraphanin, glucoerucin and sinigrin, and isothiocyanates, as sulforaphane and erucin, has developed and validated. This method has been used for the analysis of functional foods enriched with vegetable extracts. Chapter 3 focused on a physicochemical study of the interaction between the bile acid sequestrants used in the treatment of hypercholesterolemia including colesevelam and cholestyramine with obeticolic acid (OCA), potent agonist of nuclear receptor farnesoid X (FXR). In particular, a new experimental model for the determination of equilibrium binding isotherm was developed. Chapter 4 focused on methodological aspects of new hard ionization coupled with liquid chromatography (Direct-EI-UHPLC-MS) not yet commercially available and potentially useful for qualitative analysis and for “transparent” molecules to soft ionization techniques. This method was applied to the analysis of several steroid derivatives.

Original analytical methods for the determination of psychoactive compounds in complex matrices

This thesis work aims to develop original analytical methods for the determination of drugs with a potential for abuse, for the analysis of substances used in the pharmacological treatment of drug addiction in biological samples and for the monitoring of potentially toxic compounds added to street drugs. In fact reliable analytical techniques can play an important role in this setting. They can be employed to reveal drug intake, allowing the identification of drug users and to assess drug blood levels, assisting physicians in the management of the treatment. Pharmacological therapy needs to be carefully monitored indeed in order to optimize the dose scheduling according to the specific needs of the patient and to discourage improper use of the medication. In particular, different methods have been developed for the detection of gamma-hydroxybutiric acid (GHB), prescribed for the treatment of alcohol addiction, of glucocorticoids, one of the most abused pharmaceutical class to enhance sport performance and of adulterants, pharmacologically active compounds added to illicit drugs for recreational purposes. All the presented methods are based on capillary electrophoresis (CE) and high performance liquid chromatography (HPLC) coupled to various detectors (diode array detector, mass spectrometer). Biological samples pre-treatment was carried out using different extraction techniques, liquid-liquid extraction (LLE) and solid phase extraction (SPE). Different matrices have been considered: human plasma, dried blood spots, human urine, simulated street drugs. These developed analytical methods are individually described and discussed in this thesis work.

Quantification of oxidized levels of specific RNA species using an aldehyde reactive probe

Emerging evidence has shown that oxidation of RNA, including messenger RNA (mRNA), is elevated in several age-related diseases, although investigation of oxidized levels of individual RNA species has been limited. Recently we reported that an aldehyde reactive probe (ARP) quantitatively reacts with oxidatively modified depurinated/depyrimidinated (abasic) RNA. Here we report a novel method to isolate oxidized RNA using ARP and streptavidin beads. An oligo RNA containing abasic sites that were derivatized with ARP was pulled down by streptavidin beads, whereas a control oligo RNA was not. In vitro oxidized RNA, as well as total cellular RNA, isolated from oxidatively stressed cells was also pulled down, dependent on oxidation level, and concentrated in the pull-down fraction. Quantitative reverse transcription polymerase chain reaction (RT-PCR) using RNA in the pull-down fraction demonstrated that several gene transcripts were uniquely increased in the fraction by oxidative stress. Thus, our method selectively concentrates oxidized RNA by pull-down and enables the assessment of oxidation levels of individual RNA species. (C) 2011 Elsevier Inc. All rights reserved.

Determination of carbohydrate-deficient transferrin in human serum with capillary zone electrophoresis. Sample preparation strategies for the removal of interferences caused by increased levels of immunoglobulins

Capillary zone electrophoresis (CZE) in fused-silica capillaries is an effective analytical approach for the separation and determination of the transferrin (Tf) isoforms and thus carbohydrate-deficient transferrin (CDT) in human serum. Sera of patients with progressed liver cirrhosis are prone to interferences in the beta region which prevent the proper determination of CDT by CZE without additional sample preparation. Efforts to identify, reduce or even eliminate these interferences have been undertaken. Data obtained by ultrafiltration, affinity subtraction procedures using protein A, protein L and antibodies against immunoglobulins or Tf, and immunopurification of Tf suggest that the interferences in the patient sera are caused by increased levels of IgA and IgM and are best eliminated by immunopurification. Avian IgY antibody spin column immunocapture of serum Tf followed by CZE analysis of the stripped and concentrated fraction is shown to provide an attractive approach for CDT monitoring in sera with beta region interferences.