Application of solid-phase microextraction in analytical toxicology

The untargeted urine volatilome for biomedical applications: methodology and volatilome database

Chemically diverse in compounds, urine can give us an insight into metabolic breakdown products from foods, drinks, drugs, environmental contaminants, endogenous waste metabolites, and bacterial by-products. Hundreds of them are volatile compounds; however, their composition has never been provided in detail, nor has the methodology used for urine volatilome untargeted analysis. Here, we summarize key elements for the untargeted analysis of urine volatilome from a comprehensive compilation of literature, including the latest reports published. Current achievements and limitations on each process step are discussed and compared. 34 studies were found retrieving all information from the urine treatment to the final results obtained. In this report, we provide the first specific urine volatilome database, consisting of 841 compounds from 80 different chemical classes.

Approaches to Formaldehyde Measurement: From Liquid Biological Samples to Cells and Organisms

Formaldehyde (FA) is the simplest aldehyde present both in the environment and in living organisms. FA is an extremely reactive compound capable of protein crosslinking and DNA damage. For a long time, FA was considered a "biochemical waste" and a by-product of normal cellular metabolism, but in recent decades the picture has changed. As a result, the need arose for novel instruments and approaches to monitor and measure not only environmental FA in water, cosmetics, and household products, but also in food, beverages and biological samples including cells and even organisms. Despite numerous protocols being developed for in vitro and in cellulo FA assessment, many of them have remained at the "proof-of-concept" stage. We analyze the suitability of different methods developed for non-biological objects, and present an overview of the recently developed approaches, including chemically-synthesized probes and genetically encoded FA-sensors for in cellulo and in vivo FA monitoring. We also discuss the prospects of classical methods such as chromatography and spectrophotometry, and how they have been adapted in response to the demand for precise, selective and highly sensitive evaluation of FA concentration fluctuations in biological samples. The main objectives of this review is to summarize data on the main approaches for FA content measurement in liquid biological samples, pointing out the advantages and disadvantages of each method; to report the progress in development of novel molecules suitable for application in living systems; and, finally, to discuss genetically encoded FA-sensors based on existing natural biological FA-responsive elements.

In Vivo Solid-Phase Microextraction and Applications in Environmental Sciences

Solid-phase microextraction (SPME) is a well-established sample-preparation technique for environmental studies. The application of SPME has extended from the headspace extraction of volatile compounds to the capture of active components in living organisms via the direct immersion of SPME probes into the tissue (in vivo SPME). The development of biocompatible coatings and the availability of different calibration approaches enable the in vivo sampling of exogenous and endogenous compounds from the living plants and animals without the need for tissue collection. In addition, new geometries such as thin-film coatings, needle-trap devices, recession needles, coated tips, and blades have increased the sensitivity and robustness of in vivo sampling. In this paper, we detail the fundamentals of in vivo SPME, including the various extraction modes, coating geometries, calibration methods, and data analysis methods that are commonly employed. We also discuss recent applications of in vivo SPME in environmental studies and in the analysis of pollutants in plant and animal tissues, as well as in human saliva, breath, and skin analysis. As we show, in vivo SPME has tremendous potential for the targeted and untargeted screening of small molecules in living organisms for environmental monitoring applications.

Development of a bimetal-organic framework-polypyrrole composite as a novel fiber coating for direct immersion solid phase microextraction in situ supercritical fluid extraction coupled with gas chromatography for simultaneous determination of furfurals in dates

A new, simple, hyphenated technique couples supercritical fluid extraction and direct immersion SPME with GC-FID (SFE-DI-SPME-GC-FID) for the determination of 2-furaldehyde (2-F) and 5-hydroxymethylfurfural (5-HMF) in solid foods. A bimetal-organic framework-polypyrrole composite was grown in situ on stainless steel wire in solution and used as a novel solid phase microextraction (SPME) fiber coating. A central composite design based on a 2^n-1 fractional factorial experimental design was employed to optimize the SFE conditions for 2-F and 5-HMF at a pressure of 325 atm, temperature of 35 °C, dynamic extraction time of 15 min, and modifier volume of 150 μL. Also, the factors related to the solid-phase microextraction method including ionic strength, desorption time and temperature together with extraction time and temperature were optimized prior to the gas chromatography analysis. Under the optimal conditions, the limits of detection were in the range of 1.28-5.92 μg kg^-1. This method showed good linearity for 2-F and 5-HMF in the ranges of 40-50 000 and 4540-500 000 μg kg^-1, respectively, with coefficients of determination more than 0.9995. Single fiber repeatability and fiber-to-fiber reproducibility were less than 6.76% and 9.12%, respectively. The new method was successfully utilized to determine the amounts of 2-F and 5-HMF in the real solid food matrix without the need for tedious pretreatments.

Simple determination of valproic acid serum concentrations using BioSPME followed by gas chromatography-mass spectrometric analysis

Valproic acid (VA) is a drug widely used on the treatment of epilepsy and bipolar affective disorders, with stablished therapeutic concentration ranges in serum. The measurement of VA serum concentrations using chromatographic methods requires a sample preparation step. In this context, this study aims to describe the development and validation of an assay for VA measurement in serum using a new microextraction strategy, known as BioSPME, followed by GC-MS analysis. The extraction procedure was very simple based on direct immersion of the BioSPME tips on acidified serum, followed by agitation and desorption in methanol. The methanolic extracts were directly injected into the chromatograph. Extraction yield was 95.6 to 101.3%. The assay was linear from 10 to 150 mg L^-1. Precision, accuracy and stability assays were acceptable according to bioanalytical validation guidelines. The method was applied to 41 clinical serum samples also tested with a previously GC-MS validated assay, which used liquid-liquid extraction as sample preparation. Measurements obtained with both methods were comparable. This study is the first description of the use of BioSPME tips for a therapeutic drug. BioSPME is a promising alternative for the preparation of biological specimens prior to the determination of therapeutic drugs by GC-MS.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

A green analytical method for the analysis of polycyclic aromatic hydrocarbons in oral fluids from crack smokers

Aim: Develop and validate a method of solid-phase microextraction (SPME) and liquid chromatography to investigate three major polycyclic aromatic hydrocarbons (PAHs) in oral fluid. Results/Methodology: The extraction phase was exposed to 1.5 ml of diluted oral fluid under stirring at 1000 rpm for 60 min, at 70°C. Then, it was immersed in 200 μl of acetonitrile for 10 min at 25°C for desorption of the analytes. Linearity, absolute recovery, and inter- and intra-assay relative standard deviations and relative errors were 50-300 ng.ml^-1, ≥24% and ≤15% for all analytes, respectively. A full factorial design was used to SPME optimization. Discussion/Conclusion: The method is suitable for the exploratory analysis of some PAHs in the oral fluid of crack smokers.

What the lab can and cannot do: clinical interpretation of drug testing results

Urine drug testing is one of the objective tools available to assess adherence. To monitor adherence, quantitative urinary results can assist in differentiating "new" drug use from "previous" (historical) drug use. "Spikes" in urinary concentration can assist in identifying patterns of drug use. Coupled chromatographic-mass spectrometric methods are capable of identifying very small amounts of analyte and can make clinical interpretation rather challenging, specifically for drugs that have a longer half-life. Polypharmacy is common in treatment and rehabilitation programs because of co-morbidities. Medications prescribed for comorbidities can cause drug-drug interaction and phenoconversion of genotypic extensive metabolizers into phenotypic poor metabolizers of the treatment drug. This can have significant impact on both pharmacokinetic (PK) and pharmacodynamic properties of the treatment drug. Therapeutic drug monitoring (TDM) coupled with PKs can assist in interpreting the effects of phenoconversion. TDM-PKs reflects the cumulative effects of pathophysiological changes in the patient as well as drug-drug interactions and should be considered for treatment medications/drugs used to manage pain and treat substance abuse. Since only a few enzyme immunoassays for TDM are available, this is a unique opportunity for clinical laboratory scientists to develop TDM-PK protocols that can have a significant impact on patient care and personalized medicine. Interpretation of drug screening results should be done with caution while considering pharmacological properties and the presence or absence of the parent drug and its metabolites. The objective of this manuscript is to review and address the variables that influence interpretation of different drugs analyzed from a rehabilitation and treatment programs perspective.

Simultaneous Determination of Cocaine and Metabolites in Human Plasma Using Solid Phase Micro-Extraction Fiber Tips C18 and UPLC-MS/MS

The determination of cocaine (COC) and its metabolites ecgonine methyl ester (EME), benzoylecgonine (BZE), norcocaine (NCOC) and cocaethylene (CE) in human plasma is relevant in clinical and forensic toxicology. An efficient extraction and clean-up of plasma specimens for the simultaneous determination of BZE along with COC and basic metabolites is challenging due to their widely different polarities and ionization characteristics. Recently, biocompatible SPME LC tips C18 became commercially available. We applied SPME LC tips C18 to the simultaneous extraction of COC, BZE, EME, NCOC, and CE by direct immersion of the fiber in plasma diluted with a buffer at pH 8.0. Analytes were desorbed from the fiber to methanol containing formic acid and injected into a UPLC-MS/MS system. The assay was linear from 5 to 500 ng mL-1. Precision assays presented CV% in the range of 2.22 to 10.54%, and accuracy was in the range of 93.4-108.1%. The assay requires minimal quantities of plasma and organic solvents, allowing multiple extractions in parallel. Biocompatible SPME is a promising alternative for preparing biological samples prior to drug measurement by UPLC-MS/MS.

Comparative analysis of Rapid Equilibrium Dialysis (RED) and solid phase micro-extraction (SPME) methods for In Vitro-In Vivo extrapolation of environmental chemicals

In vitro to in vivo extrapolation (IVIVE) is a critical component of the efforts to prioritize and assess environmental chemicals using high-throughput in vitro assays. The plasma unbound fraction (F_ub) is a key toxicokinetic parameter in IVIVE, and is usually measured via the Rapid Equilibrium Dialysis (RED) assay widely used for pharmaceuticals. However, pharmaceuticals have a narrower range of physicochemical properties than environmental chemicals. Motivated by the observation that high LogK_OW compounds appeared to have disproportionately low F_ub measurements using RED, we added a protein-free control in order to verify equilibration to 100% unbound in the absence of proteins. We found that many high LogK_OW non-pharmaceuticals fail to equilibrate in RED in protein-free controls, and thus had apparent values of F_ub = 0 in plasma. In these cases, Solid Phase Microextraction (SPME) as an alternative method provided an accurate, though more time-consuming, alternative to accurately determine F_ub. We propose an updated IVIVE workflow that adds a protein-free control to the RED protocol, with the use of alternative approaches, such as SPME, in cases where compounds fail to adequately equilibrate. These refinements will provide additional confidence in the use of IVIVE as part of high-throughput screening programs of chemicals.

Dynamic headspace analysis using online measurements: Modeling of average and initial concentration

Dynamic headspace sampling is an important technique for the analysis of consumer products, the study of biological samples and environmental water analyses. This paper shows the influence of experimental conditions, such as the sampling time, sampling flow rate, headspace volume, liquid volume and Henry coefficient on the measured average concentration values. A corresponding closed expression as function of these variables is introduced in order to quantify the deviation of the initial headspace concentration. The proposed bi-exponential function embeds different current existing models for recovery calculation in dynamic sampling analyses in one single expression. A fully automated and user-friendly Excel^® file to investigate or to model the dynamic headspace sampling results is added to everyone's easy use.

Green sample preparations for the bioanalysis of drugs of abuse in complex matrices

The sample preparation is the most critical step involved in the bioanalytical process. When dealing with green analytical chemistry, sample preparation can be even more challenging. To fit the green analytical chemistry principles, efforts should be made toward the elimination or reduction of the use of toxic reagents and solvents, minimization of energy consumption and increased operator safety. The simplest sample preparations are more appropriate for liquid biological matrices with little interfering compounds such as urine, plasma and oral fluid. The same does not usually occur with complex matrices that require more laborious procedures. The present review discusses green analytical approaches for the analyses of drugs of abuse in complex biological matrices, such as whole blood, breast milk, meconium and hair.

Potential application of amino acids in analytical toxicology

The ability of extraction and preconcentration of small quantities of substances from biological samples is important in analytical sciences, particularly forensic medicine. In the present study, we evaluated the binding potential of amino acids to produce a new solid phase microextraction fiber based on carbon nanotube (CNTs) for extraction and preconcentration of small amount of morphine in urine sample. Raw CNTs were first carboxylated and then functionalized with 3 amino acids including glutamate, arginine, and cysteine. Functionalization was confirmed by FTIR analysis, Raman spectroscopy and SEM imaging. The functionalized CNTs were coated on polypropylene hollow fiber and used for preconcentration. The results of HPLC analysis in isocratic elution mode using acetonitrile-sodium acetate (10:90, v/v; pH 4; 0.01 M) as the mobile phase showed that amino acids are able to adsorb morphine and the prepared fiber could preconcentrate a very low concentration of morphine (0.25 ppb) in urine matrix. In addition, the fiber was successfully used for up to 30 times with no significant loss in the extraction efficiency. Lowest limit of detection (LOD) and limit of quantitation (LOQ) was 0.07 and 0.25, respectively. Also, the lowest and best recovery of the fiber was 87.8% and 139% at LOQ, which belonged to glutamate and arginine, respectively. The fibers based on amino acids can be used for the detection of a small amount of morphine in biological samples, which are not detectable by conventional methods. Simple mechanism of these fibers in preconcentrating morphine makes them a novel candidate for detection of other opiates and drugs of abuses in crime scene investigations and postmortem examinations several days after exposure.

Development of a simple HPLC-DAD multi-analyte procedure and its application in cases evaluated by the Poison Control Center of São Paulo, Brazil

This work describes a simple approach to overcome challenges in emergency toxicological analysis, using liquid-liquid extraction and high-performance liquid chromatography coupled with a diode-array detector (HPLC-DAD). A rapid procedure has been developed, for the extraction and detection of 19 analytes from the following drug classes: analgesics, benzodiazepines, antidepressants, anticonvulsants and drugs of abuse. These substances are relevant in the context of emergency toxicology in Brazil. The method has been validated according to international guidelines by establishing parameters such as lower limit of quantification, sensitivity, linearity, accuracy and precision. The intra and inter-day precision values, at the lowest concentration levels, have always been less than 20% considering its relative standard deviation. As for accuracy values, these have also been satisfactory (above 81.3%). This method was successfully applied in 201 blood samples from patients with suspected poisoning of the Poison Control Center of São Paulo (PCC-SP), Brazil. Finally, the developed method has shown to be relevant for emergency toxicology due to its high sensitivity and it could be also very useful in both fields of clinical and forensic toxicology.

Silicon carbide nanomaterial as a coating for solid-phase microextraction

Silicon carbide has excellent properties, such as corrosion resistance, high strength, oxidation resistance, high temperature, and so on. Based on these properties, silicon carbide was coated on stainless-steel wire and used as a solid-phase microextraction coating, and polycyclic aromatic hydrocarbons were employed as model analytes. Using gas chromatography, some important factors that affect the extraction efficiency were optimized one by one, and an analytical method was established. The analytical method showed wide linear ranges (0.1-30, 0.03-30, and 0.01-30 μg/L) with satisfactory correlation coefficients (0.9922-0.9966) and low detection limits (0.003-0.03 μg/L). To investigate the practical application of the method, rainwater and cigarette ash aqueous solution were collected as real samples for extraction and detection. The results indicate that silicon carbide has excellent application in the field of solid-phase microextraction.

Measurement uncertainty for the determination of amphetamines in urine by liquid-phase microextraction and gas chromatography-mass spectrometry

A gas chromatography-mass spectrometry method for the determination of amphetamines in urine samples by means of liquid-phase microextraction was validated, including calculation of measurement uncertainty. After extraction in the three-phase mode, acceptor phase was withdrawn from the fiber and the residue was derivatized with trifluoroacetic anhydride. The method showed to be very simple, rapid and it required a significantly low amount of organic solvent for extraction. The limits of detection were 10 and 20μg/L for amphetamine and methamphetamine, respectively. The calibration curves were linear over the specified range (20μg/L to 1400μg/L; r(2)>0.99). The method showed to be both precise and accurate and a relative combined uncertainty of 2% was calculated. In order of importance, the factors which were more determinant for the calculation of method uncertainty were: analyte concentration, sample volume, trueness and method precision.

Determination of amphetamines in biological samples using electro enhanced solid-phase microextraction-gas chromatography

In this work, an ordered mesoporous carbon (OMC)/Nafion coated fiber for solid-phase microextraction (SPME) was prepared and used as the working electrode for electro-enhanced SPME (EE-SPME) of amphetamines. The EE-SPME strategy is primarily based on the electro-migration and complementary charge interaction between fiber coating and ionic compounds. Compared with traditional SPME, EE-SPME exhibited excellent extraction efficiency for amphetamine (AP) and methamphetamine (MA) with an enhancement factor of 7.8 and 12.1, respectively. The present strategy exhibited good linearity for the determination of AP and MA in urine samples in the range of 10-1000ngmL(-1) and 20-1000ngmL(-1), respectively. The detection limits were found to be 1.2ngmL(-1) for AP and 4.8ngmL(-1) for MA. The relative standard deviations were calculated to be 6.2% and 8.5% for AP and MA, respectively. Moreover, the practical application of the proposed method was demonstrated by analyzing the amphetamines in urine and serum samples with satisfactory results.

In vivo and ex vivo SPME: a low invasive sampling and sample preparation tool in clinical bioanalysis

Solid phase microextraction (SPME) is well-established technology in bioanalysis. Current review discusses the features of SPME, which determine the non- or low-invasiveness of the method in biomedical analysis. In the first section we analyze the factors, which have significant influence on the SPME sampling device performance in the view of sampling safety and efficiency. In the later sections applicability of various SPME approaches for analysis of easily accessible samples routinely used for analysis (e.g., urine, blood) as well as limited availability samples (tissues) is discussed. Moreover, the examples of sampling alternative matrices such as hair, saliva, sweat or breath are presented. The advantages and limitation of the technology in the view of future development of SPME are also reviewed.

Dendrimer grafted nanoporous silica as a new coating for headspace solid-phase microextraction fibers

Preparation of a SBA-15 silica-supported dendrimer.

Electrochemically controlled in-tube solid phase microextraction of naproxen from urine samples using an experimental design

Electrochemically controlled in-tube SPME approach, which increased the sensitivity and decreased the extraction time, was reported.

Simultaneous analysis of amphetamine-type stimulants in plasma by solid-phase microextraction and gas chromatography-mass spectrometry

Brazil is considered one of the countries with the highest number of amphetamine-type stimulant (ATS) users worldwide, mainly diethylpropion (DIE) and fenproporex (FEN). The use of ATS is mostly linked to diverted prescription stimulants and this misuse is widely associated with (ab)use by drivers. A validated method was developed for the simultaneous analysis of amphetamine (AMP), DIE and FEN in plasma samples employing direct immersion-solid-phase microextraction, and gas chromatographic/mass spectrometric analysis. Trichloroacetic acid 10% was used for plasma deproteinization. In situ derivatization with propylchloroformate was employed. The linear range of the method covered from 5.0 to 100 ng/mL. The detection limits were 1.0 (AMP), 1.5 (DIE) and 2.0 ng/mL (FEN). The accuracy assessment of the control samples was within 85.58-108.33% of the target plasma concentrations. Recoveries ranged from 46.35 to 84.46% and precision was <15% of the value of relative standard deviation. This method is appropriate for screening and confirmation in plasma forensic toxicology analyses of these basic drugs.

Solid phase microextraction and related techniques for drugs in biological samples

In drug discovery and development, the quantification of drugs in biological samples is an important task for the determination of the physiological performance of the investigated drugs. After sampling, the next step in the analytical process is sample preparation. Because of the low concentration levels of drug in plasma and the variety of the metabolites, the selected extraction technique should be virtually exhaustive. Recent developments of sample handling techniques are directed, from one side, toward automatization and online coupling of sample preparation units. The primary objective of this review is to present the recent developments in microextraction sample preparation methods for analysis of drugs in biological fluids. Microextraction techniques allow for less consumption of solvent, reagents, and packing materials, and small sample volumes can be used. In this review the use of solid phase microextraction (SPME), microextraction in packed sorbent (MEPS), and stir-bar sorbtive extraction (SBSE) in drug analysis will be discussed. In addition, the use of new sorbents such as monoliths and molecularly imprinted polymers will be presented.

Solid phase microextraction (SPME) combined with TGA as a technique for guest analysis in crystal engineering

Guest identification using SPME – a technique for analysis of TGA off-gas that eliminates the need for direct TGA-GC/MS coupling.

Oriented ZnO nanorods grown on a porous polyaniline film as a novel coating for solid-phase microextraction

In this work, oriented ZnO nanorods (ZNRs) were in situ hydrothermally grown on a porous polyaniline (PANI) film to function as a solid-phase microextraction (SPME) coating. Scanning electron microscopy (SEM) study revealed that the majority of oriented ZNRs grew from pores of PANI matrix, which protected the ZNRs from easily peeling off during operation. Furthermore, in this process, a thin layer of PANI was found to cover the ZNRs, which can enlarge the effective surface area of the composite coating. This ZNRs/PANI composite coating combined the merits of both ZNRs and PANI and, thus, has several advantages over that of sole PANI film and ZNRs coating such as improved extraction efficiency for benzene homologues, enhanced mechanical stability and longer service life (over 150 cycles of SPME-GC operation). Coupled with gas chromatography-flame ionization detector (GC-FID), the optimized SPME-GC-FID method was used for the analysis of six benzene homologues in water samples. The calibration curves were linear from 1 to 1000μgL(-1) for each analyte, and the limits of detection were between 0.001 and 0.024μgL(-1). Single fiber repeatability and fiber-to-fiber reproducibility were in the range of 1.3-6.8% and 5.3-11.2%, respectively. The spiked recoveries at 100 and 5μgL(-1) for three environmental water samples were in the range of 79.8-115.4% and 73.7-117.4%, respectively.

A solid-phase microextraction method for the in vivo sampling of MTBE in common reed (Phragmites australis)

Phytoscreening of phytoremediation-based plantings is discussed as a promising monitoring tool in literature. We developed and applied an analytical procedure for the in vivo sampling of methyl tert-butyl ether (MTBE) in the common reed (Phragmites australis) from a phytoremediation site highly polluted with MTBE. The approach uses solid-phase microextraction (SPME) with the SPME fibre directly introduced into the aerenchyma of the plant stem. For optimising the analytical procedure and estimating the capability of the proposed method, laboratory tests on the microcosm scale and field studies over one vegetation period were carried out. Furthermore, the results of in vivo SPME sampling were compared with those obtained with the traditional approach for analysing plants using dynamic headspace analysis. The MTBE signals detected within the plants were also correlated with the concentration in the water phase. The discussion of results showed the feasibility of the proposed method for a qualitative phytoscreening of volatile organic compounds present in wetland plants.