Screening of non-polar heterocyclic amines in urine by microextraction in packed sorbent-fluorimetric detection and confirmation by capillary liquid chromatography

Determining heterocyclic aromatic amines in aqueous samples: A novel dispersive liquid-liquid micro-extraction method based on solidification of floating organic drop and ultrasound assisted back extraction followed by UPLC-MS/MS

A novel dispersive liquid-liquid microextraction based on solidification of floating organic droplet combined with ultrasound assisted back extraction for the determination of four heterocyclic aromatic amines in natural water samples prior ultra high-performance liquid chromatography-tandem mass spectrometry was developed. The analytes were extracted from the water samples by a dispersive liquid-liquid microextraction procedure based on solidification of floating organic drop, which was performed by a mixture composed by a less dense than water extraction solvent, 1-undecanol, and a dispersive solvent, methanol. After that, a novel ultrasound assisted back extraction step was performed in order to make the clean-up/enrichment procedure compatible with the detection requirements. Under optimum conditions, linearity ranged from 2.2 to 50ngmL^-1, with enrichment factors from 130 to 136-folds. Thus limits of detection between 0.7 and 2.9ngmL^-1 were obtained. Precision of the method was evaluated in terms of repeatability, relative standard deviations varied from 4.3% to 6.7%. Relative recoveries ranged from 92% to 106% for all analytes. The satisfactory performance demonstrated that the proposed methodology has a strong potential for application in the multi-residue analysis of heterocyclic aromatic amines present in complex environmental matrices.

High-throughput and sensitive analysis of urinary heterocyclic aromatic amines using isotope-dilution liquid chromatography-tandem mass spectrometry and robotic sample preparation system

Heterocyclic aromatic amines (HCAA) are listed by the US Food and Drug Administration (FDA) as harmful or potentially harmful constituents of tobacco smoke. However, quantifying HCAA exposure is challenging. In this study, we developed a sensitive, precise, and accurate isotope dilution, liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify urinary HCAAs in smokers and nonsmokers. The high-throughput robotic sample preparation system could handle a throughput of over 300 samples per day, while maintaining intra-day and inter-day imprecision and bias ≤10 %. The limits of detection of carcinogenic HCAAs ranged from 0.31 to 0.83 pg/mL. The validated method was applied to measure HCAAs in urine collected from smokers and non-smokers. This sensitive and efficient analytical method is ideal to support large-scale biomonitoring studies of HCAA exposure. Graphical Abstract LC/MS/MS and robotic sample preparation system for urinary HCAA analysis.

Biosensor based on inhibition of monoamine oxidases A and B for detection of β-carbolines

β-Carbolines are inhibitors of monoamine oxidases (MAO-A and MAO-B) and can be found in foods, hallucinogenic plant or various drugs. We have developed a fast analysis method for β-carbolines based on the inhibition of MAO. The enzymes were immobilized on screen-printed electrodes modified with a stabilized film of Prussian blue that contain also copper. We have used benzylamine as substrate for the enzymatic reaction and the hydrogen peroxide was measured amperometrically at -50 mV. The detection limits obtained were 5.0 µM for harmane and 2.5 µM for both harmaline and norharmane. The MAO-A is inhibited by all three tested β-carbolines (harmane, norharmane, and harmaline) while MAO-B is inhibited only by norharmane. The presence of norharmane in mixtures of β-carbolines can be identified based on the difference between the cumulative inhibition of MAO-A by all β-carbolines and MAO-B inhibition. The developed biosensors were used for food analysis.

Microwave-assisted synthesis of carbon dots and its potential as analysis of four heterocyclic aromatic amines

Fluorescent water soluble carbon nanoparticles, in short carbon dots (CDs), was synthesized from lactose by microwave assisted hydrochloric acid method. Characterized by TEM and DLS to obtain the morphology shape (average 10nm in size), with a higher negative surface charge supported by the composition was obtained by XPS spectroscopy. The maximum of the emission was centered at 450 nm with a lifetime of 2.1 ns. Without further functionalization of the CDs a nanosensor was obtained that responded exponentially to HAAs in the 0.35-0.45 mg L(-1) concentration range by fluorescence static quenching, demonstrated by the lifetime analysis of the CDs in presence of HAAs. Some amino compounds were selected as model for interferences to evaluate the selectivity of this method, showing a notorious added value, with recoveries around 98%. The accuracy of the method was in terms of RSD about 2.5%. The results suggest their promising applications in chemical sensing.

Determination of endosulfan isomers and their metabolites in tap water and commercial samples using microextraction by packed sorbent and GC-MS

A simple, rapid, accurate and sensitive method using microextraction by packed sorbent (MEPS) followed by GC-MS has been pursued for the determination of organochlorine insecticide endosulfan isomers (α and β) and their metabolites (ether, lactone and sulfate). MEPS is a miniaturised version of SPE employing C18 packing material. It is very efficient technique as it employs as low as 10 μL of sample volume. The distinct feature of MEPS is the magnitude of the elution volume that could be directly injected to GC system. Various parameters such as extraction cycles, washing solvent, elution solvent, elution volume and pH, which influenced the MEPS performance, were tested and optimised. The calibration curves were obtained in the concentration range 1-500 ng/mL. The results showed a close correlation coefficient (R(2) > 0.991) for all analytes in the calibration range studied. The LOD and LOQ obtained for GC-MS under selected ion monitoring acquisition are between 0.0038-0.01 and 0.0125-0.033 ng/mL, respectively. The developed method is applicable for the quantification of these compounds in tap water and commercial samples. This method has been shown to be selective as no interferences from endogenous substances were detected by analysis. This method not only decreases sample preparation time but is cheaper, eco-friendly and easier to perform compared to traditional techniques.

Microextraction by Packed Sorbent (MEPS) and Solid-Phase Microextraction (SPME) as Sample Preparation Procedures for the Metabolomic Profiling of Urine

For a long time, sample preparation was unrecognized as a critical issue in the analytical methodology, thus limiting the performance that could be achieved. However, the improvement of microextraction techniques, particularly microextraction by packed sorbent (MEPS) and solid-phase microextraction (SPME), completely modified this scenario by introducing unprecedented control over this process. Urine is a biological fluid that is very interesting for metabolomics studies, allowing human health and disease characterization in a minimally invasive form. In this manuscript, we will critically review the most relevant and promising works in this field, highlighting how the metabolomic profiling of urine can be an extremely valuable tool for the early diagnosis of highly prevalent diseases, such as cardiovascular, oncologic and neurodegenerative ones.

A critical review of microextraction by packed sorbent as a sample preparation approach in drug bioanalysis

Sample preparation is widely accepted as the most labor-intensive and error-prone part of the bioanalytical process. The recent advances in this field have been focused on the miniaturization and integration of sample preparation online with analytical instrumentation, in order to reduce laboratory workload and increase analytical performance. From this perspective, microextraction by packed sorbent (MEPS) has emerged in the last few years as a powerful sample preparation approach suitable to be easily automated with liquid and gas chromatographic systems applied in a variety of bioanalytical areas (pharmaceutical, clinical, toxicological, environmental and food research). This paper aims to provide an overview and a critical discussion of recent bioanalytical methods reported in literature based on MEPS, with special emphasis on those developed for the quantification of therapeutic drugs and/or metabolites in biological samples. The advantages and some limitations of MEPS, as well as its comparison with other extraction techniques, are also addressed herein.

Recent advances in bioanalytical sample preparation for LC-MS analysis

Sample preparation has historically been, and continues to be, the most challenging part of the bioanalytical workflow. Several techniques have been developed over the years to deal with the problems of recovery and matrix effects in an effort to increase the reliability and robustness of the bioanalytical method. In recent years certain techniques have come into prominence and gained acceptance in routine sample preparation, and some have shown promise in their use in a discovery environment where speed is critical and method development time is often limited. The aim of this review is to examine several of these techniques and provide examples of their use from the literature, as well as comment on their utility in current workflows.

Rapid screening of polycyclic aromatic hydrocarbons (PAHs) in waters by directly suspended droplet microextraction-microvolume fluorospectrometry

A rapid and simple screening method for polycyclic aromatic hydrocarbons (PAHs) in water samples is proposed. The method is based on the combination of a miniaturized sample preparation approach, namely, directly suspended droplet microextraction (DSDME), and microvolume fluorospectrometry. Benzo[a]pyrene (BaP) was used as the model compound for screening purposes. Under optimal conditions, a detection limit of 0.024 μg L(-1) and an enrichment factor of 159 were obtained for BaP in 5 min. The repeatability, expressed as relative standard deviation (RSD), was 4.9% (n=8). The unreliability region of the screening method was 0.54-0.67 μg L(-1), by using a cut-off value of 0.6 μg L(-1) of BaP. Finally, the proposed method was applied to the in situ achievement of the binary "yes/no" response for PAHs in different water samples and recovery studies were performed at three different levels, with BaP recoveries in the range of 93-104%.