Álvaro J. Santos-Neto

Simultaneous analysis of five antidepressant drugs using direct injection of biofluids in a capillary restricted-access media-liquid chromatography-tandem mass spectrometry system

Direct analysis, with minimal sample pretreatment, of antidepressant drugs, fluoxetine, imipramine, desipramine, amitriptyline, and nortriptyline in biofluids was developed with a total run time of 8 min. The setup consists of two HPLC pumps, injection valve, capillary RAM-ADS-C18 pre-column and a capillary analytical C18 column connected by means of a six-port valve in backflush mode. Detection was performed with ESI-MS/MS and only 1 microm of sample was injected. Validation was adequately carried out using FLU-d(5) as internal standard. Calibration curves were constructed under a linear range of 1-250 ng mL(-1) in plasma, being the limit of quantification (LOQ), determined as 1 ng mL(-1), for all the analytes. With the described approach it was possible to reach a quantified mass sensitivity of 0.3 pg for each analyte (equivalent to 1.1-1.3 fmol), translating to a lower sample consumption (in the order of 10(3) less sample than using conventional methods).

Analysis of fluoxetine and norfluoxetine in human plasma by liquid-phase microextraction and injection port derivatization GC-MS.

A two-phase liquid phase microextraction using a hollow fiber combined with injection port derivatization and gas chromatographic analysis was developed for extracting and detecting fluoxetine (FLU) and norfluoxetine (NOR) in human plasma. Simultaneous extraction in a multiple tube shaker was used and, afterward, the organic phase was simply injected together with the derivatizing agent n-methyl-bis(trifluoroacetamide) (MBTFA). Factors influencing injection port derivatization, and several extraction parameters were optimized. Under optimal conditions the proposed method provided linearity between 10 and 500ngmL(-1) (R(2)=0.9973) for FLU, and between 15 and 500ngmL(-1) (R(2)=0.9972) for NOR. Intra-assay precision (RSD) between 4.8 and 13.1% and inter-assay between 5.4 and 14.2% were obtained, with detection and quantification limits of 3 and 10ngmL(-1), and of 5 and 15ngmL(-1) for FLU and NOR, respectively, using selected ion monitoring mode. Selectivity, short term stability and extraction efficiency were also evaluated. This method was simple, cheap, and environmentally friendly, yielding significant reduction of solvents and derivatizing agent consumption. The method was successfully applied to the analysis of samples from 5 patients under fluoxetine treatment.

Development of a new stir bar sorptive extraction coating and its application for the determination of six pesticides in sugarcane juice

In this article, a novel polydimethylsiloxane/activated carbon (PDMS-ACB) material is proposed as a new polymeric phase for stir bar sorptive extraction (SBSE). The PDMS-ACB stir bar, assembled using a simple Teflon(®)/glass capillary mold, demonstrated remarkable stability and resistance to organic solvents for more than 150 extractions. The SBSE bar has a diameter of 2.36 mm and a length of 2.2 cm and is prepared to contain 92 μL of polymer coating. This new PDMS-ACB bar was evaluated for its ability to determine the quantity of pesticides in sugarcane juice samples by performing liquid desorption (LD) in 200 μL of ethyl acetate and analyzing the solvent through gas chromatography coupled with mass spectrometry (GC-MS). A fractional factorial design was used to evaluate the main parameters involved in the extraction procedure. Then, a central composite design with a star configuration was used to optimize the significant extraction parameters. The method used demonstrated a limit of quantification (LOQ) of 0.5-40 μg/L, depending on the analyte detected; the amount of recovery varied from 0.18 to 49.50%, and the intraday precision ranged from 0.072 to 8.40%. The method was used in the analysis of real sugarcane juice samples commercially available in local markets.

Optimization of in situ derivatization SPME by experimental design for GC-MS multi-residue analysis of pharmaceutical drugs in wastewater

This paper presents the development of a procedure, which enables the analysis of nine pharmaceutical drugs in wastewater using gas chromatography-mass spectrometry (GC-MS) associated with solid-phase microextraction (SPME) for the sample preparation. Experimental design was applied to optimize the in situ derivatization and the SPME extraction conditions. Ethyl chloroformate (ECF) was employed as derivatizing agent and polydimethylsiloxane-divinylbenzene (PDMS-DVB) as the SPME fiber coating. A fractional factorial design was used to evaluate the main factors for the in situ derivatization and SPME extraction. Thereafter, a Doehlert matrix design was applied to find out the best experimental conditions. The method presented a linear range from 0.5 to 10 μg/L, and the intraday and interday precision were lower than 16%. Applicability of the method was verified from real influent and effluent samples of a wastewater treatment plant, as well as from samples of an industry wastewater and a river.

Determination of steroids, caffeine and methylparaben in water using solid phase microextraction-comprehensive two dimensional gas chromatography-time of flight mass spectrometry.

Analysis of several emerging contaminants (steroids, caffeine and methylparaben) in water using automated solid-phase microextraction with comprehensive two dimensional gas chromatography coupled to time of flight mass spectrometry (SPME-GCxGC-ToF/MS) is presented. Experimental design was used to determine the best SPME extraction conditions and the steroids were not derivatized prior to injection. SPME-GCxGC-ToF/MS provided linear ranges from 0.6 to 1200μgL(-1) and limits of detection and quantitation from 0.02 to 100μgL(-1). A series of river water samples obtained locally were subjected to analysis. SPME-GCxGC-ToF/MS is readily automated, straightforward and competitive with other methods for low level analysis of emerging contaminants.

Development of on-line molecularly imprinted solid phase extraction-liquid chromatography-mass spectrometry for triazine analysis in corn samples

A highly selective method for the analysis of triazine herbicides in corn samples based on molecularly imprinted solid phase extraction (MISPE) has been developed. Molecularly imprinted polymers (MIPs) were synthesized by precipitation polymerization using atrazine as a template, methacrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, and 2,2′-azobis-isobutrynitrile as an initiator. MISPE was developed for the on-line and automated enrichment of atrazine, simazine, terbutryn, simetryn and ametryn from corn sample extracts. High-performance liquid chromatography and time-of-flight mass spectrometry were used for the separation and confident determination of the herbicides. The limits of detection and quantitation of the proposed method were set to be 1.6–3.3 μg kg−1 and 5.0–10.0 μg kg−1. The method was successfully applied for the analysis of five types of corns and the recoveries of the triazines from the spiked samples ranged from 80.2 to 119.1%.

Sulfamethoxazole and ciprofloxacin removal using a horizontal-flow anaerobic immobilized biomass reactor

ABSTRACT The antibiotics sulfamethoxazole (SMTX) and ciprofloxacin (CIP) are commonly used in human and veterinary medicine, which explains their occurrence in wastewater. Anaerobic reactors are low-cost, simple and suitable technology to wastewater treatment, but there is a lack of studies related to the removal efficiency of antibiotics. To overcome this knowledge gap, the objective of this study was to evaluate the removal kinetics of SMTX and CIP using a horizontal-flow anaerobic immobilized biomass reactor. Two different concentrations were evaluated, for SMTX 20 and 40 μg L−1; for CIP 2.0 and 5.0 μg L−1. The affluent and effluent analysis was carried out in liquid chromatography/tandem mass spectrometry (LC-MS/MS) with the sample preparation procedure using an off-line solid-phase extraction. This method was developed, validated and successfully applied for monitoring the affluent and effluent samples. The removal efficiency found for both antibiotics at the two concentrations studied was 97%. Chemical oxygen demand (COD) exhibited kinetic constants that were different from that observed for the antibiotics, indicating the absence of co-metabolism. Also, though the antibiotic concentration was increased, there was no inhibitory effect in the removal of COD and antibiotics.

Leaf-Cutter Ant Fungus Gardens Are Biphasic Mixed Microbial Bioreactors That Convert Plant Biomass to Polyols with Biotechnological Applications

ABSTRACT Leaf-cutter ants use plant matter to culture the obligate mutualistic basidiomycete Leucoagaricus gongylophorus. This fungus mediates ant nutrition on plant resources. Furthermore, other microbes living in the fungus garden might also contribute to plant digestion. The fungus garden comprises a young sector with recently incorporated leaf fragments and an old sector with partially digested plant matter. Here, we show that the young and old sectors of the grass-cutter Atta bisphaerica fungus garden operate as a biphasic solid-state mixed fermenting system. An initial plant digestion phase occurred in the young sector in the fungus garden periphery, with prevailing hemicellulose and starch degradation into arabinose, mannose, xylose, and glucose. These products support fast microbial growth but were mostly converted into four polyols. Three polyols, mannitol, arabitol, and inositol, were secreted by L. gongylophorus, and a fourth polyol, sorbitol, was likely secreted by another, unidentified, microbe. A second plant digestion phase occurred in the old sector, located in the fungus garden core, comprising stocks of microbial biomass growing slowly on monosaccharides and polyols. This biphasic operation was efficient in mediating symbiotic nutrition on plant matter: the microbes, accounting for 4% of the fungus garden biomass, converted plant matter biomass into monosaccharides and polyols, which were completely consumed by the resident ants and microbes. However, when consumption was inhibited through laboratory manipulation, most of the plant polysaccharides were degraded, products rapidly accumulated, and yields could be preferentially switched between polyols and monosaccharides. This feature might be useful in biotechnology.

SPME determination of low concentration levels of monoaromatic chemical markers in soils after remediation by supercritical fluid extraction

Soil contamination by organic compounds has been a serious concern over the years. Among the various forms of pollutant release, gas station contamination has been widely emphasized. The presence of simple aromatic compounds in soils sampled near gas stations may indicate contamination, considering that such compounds are frequently found in petroleum-derived products. The present paper reports on the development of a process that uses pressurized fluids for the remediation of contaminated soils. Supercritical fluid extraction (SFE) employing CO2 as the solvent and an 11.0 g capacity extraction cell was utilized. In order to demonstrate the efficiency of the process, an analytical procedure employing headspace-solid phase micro extraction (HS-SPME) as the sample preparation method and GC-MS as the separation technique was optimized and validated. Limits of quantification and detection obtained were in agreement with the values established by national and international regulatory agencies. The linear range obtained was from 10 to 260 μg kg−1, with determination coefficients r2 > 0.98 for all analyses. Different removal rates were observed for the contaminants studied, the best results being achieved by employing CO2 in a supercritical state.

Liquid-phase microextraction for simultaneous chromatographic analysis of three antidepressant drugs in plasma

A method using Liquid Phase Microextraction for simultaneous detection of citalopram (CIT), paroxetine (PAR) and fluoxetine (FLU), using venlafaxine as internal standard, in plasma by high performance liquid chromatography with fluorescence detection was developed. The linearity was evaluated between 5.0 and 500 ng mL-1 (r > 0.99) and the limit of quantification was 2.0, 3.0 and 5.0 ng mL-1 for CIT, PAR and FLU, respectively. Therefore, it can be applied to therapeutic drug monitoring, pharmacokinetics or bioavailability studies and its advantages are that it necessary relatively inexpensive equipment and sample preparation techniques. The SSRIs, citalopram (CIT), fluoxetine (FLU), fluvoxamine, paroxetine (PAR) and sertraline, are the result of research to find drugs as effective as TCAs, but with fewer problems with tolera- bility and safety. SSRIs inhibit serotonin reuptake potently and selectively, resulting in the increase of serotonergic neurotransmis- sion. Although they share the primary mechanism of action with TCAs, SSRIs are structurally distinct, with marked differences in the pharmacokinetic and pharmacodynamic profile. Sertraline and paroxetine are the most potent reuptake inhibitors. The relative potency of sertraline in inhibiting dopamine uptake differentiates it pharmacologically from other SSRIs. Citalopram and fluoxetine are racemic mixtures of chiral forms that have different pharmacokinetic and pharmacodynamic profiles. The fluoxetine metabolite is long acting and is pharmacologically active. SSRIs also have different pharmacokinetic profiles, including half-life, linear pharmacoki - netics versus the non-linear effect of age on its clearance, and its potential to inhibit the drug-metabolising isoenzyme, cytochrome P450 (CYP). These differences underscore that the pharmacological and pharmacokinetic clinical differences have become increasingly important for SSRIs.2 Figure 1 shows the chemical structures of