Dispersive liquid-liquid microextraction combined with capillary electrophoresis and time-of-flight mass spectrometry for urine analysis

Microextraction Techniques for Sample Preparation of Amphetamines in Urine: A Comprehensive Review

Psychological disorders and dramatic social problems are serious concerns regarding the abuse of amphetamine and its stimulant derivatives worldwide. Consumers of such drugs experience great euphoria along with serious health problems. Determination and quantification of amphetamine-type stimulants are indispensable skills for clinical and forensic laboratories. Analysis of low drug doses in bio-matrices necessitates applications of simple and also effective preparation steps. The preparation procedures not only eliminate adverse matrix effects, but also provide reasonable clean-up and pre-concentration benefits. The current review presents different methods used for sample preparation of amphetamines from urine as the most frequently used biological matrix. The advantages and limitations of various sample preparation methods were discussed focusing on the miniaturized methods.

Recent Update on Pretreatment and Analysis Methods of Buprenorphine in Different Matrix

Buprenorphine is one of the most commonly used pain-killing drugs due to its lengthy duration of action and high potency. However, excessive usage of buprenorphine can be harmful to one's health and prolonged use might result in addiction. Additionally, an increasing number of cases have been documented involving the illegal use of buprenorphine. Therefore, a variety of effective and reliable methods for pretreatment and determination of buprenorphine and its main metabolite norbuprenorphine have been established. This review aims to update the current state of pretreatment and detection techniques for buprenorphine and norbuprenorphine from January 2010 to March 2022. Pretreatment methods include several traditional extraction methods, solid-phase extraction, QuECHERS, various micro-extraction techniques, etc. while analytical methods include LC-MS, LC coupled with other detectors, GC-MS, capillary electrophoresis, electrochemical sensors, etc. The pros and cons of various techniques were compared and summarized, and the prospects were provided.HIGHLIGHTSProgress in pretreatment and detection methods for buprenorphine is demonstrated.Pros and cons of different pretreatment and analysis methods are compared.New materials (such as nanomaterials and magnetic materials) used in buprenorphine pretreatment are summarized.Newly emerged environmental-friendly methods are discussed.

Development of a dispersive liquid-liquid microextraction method for the evaluation of maternal-fetal exposure to cocaine employing human umbilical cord tissue

Illicit drug use is a serious and complex public health problem, not only due to the severity of the health damage but also to the social implications, such as marginalization and drug trafficking. Currently, cocaine (COC) is among the most abused drugs worldwide with about 22 million users. Drug abuse has also been found in women during the pregnancy period, which has shed light on a new group for epidemiology. The diagnosis of COC use in these cases usually depends largely on the mother's reports, which in several cases omit or deny consumption. Therefore, considering physical-chemical methods of sample preparation and exposure biomarkers, the development of analytic toxicological methods can help to confirm drug use during pregnancy. Thus, the objective of the present work was to develop an analytical method based on dispersive liquid-liquid microextraction for the determination of COC analytes, using umbilical cord tissue as an alternative biological matrix, and detection by gas chromatography coupled to mass spectrometry. Therefore, after optimization, the dispersive liquid-liquid microextraction method was fully validated for quantification of COC, benzoylecgonine, cocaethylene, ecgonine, ecgonine methyl ester and norcocaine. The limits of detection were between 15 and 25 ng/g, the limits of quantification were 30 ng/g for ecgonine and 25 ng/g for the other analytes. Linearity ranged from the limits of quantification to 1,000 ng/g. Coefficients of variation for intra-assay precision were <18.5%, inter-assay was <8.75% and bias was <16.4% for all controls. The developed method was applied in 10 suspected positive samples, based on the mother's report and maternal urine screening and confirmation. COC, benzoylecgonine, ecgonine and ecgonine methyl ester were quantified in four umbilical cords with concentrations that ranged from 39.6 to 420.5 ng/g.

Dispersive liquid-liquid microextraction followed by sweeping micellar electrokinetic chromatography-tandem mass spectrometry for determination of six breast cancer drugs in human plasma

Herein, we have developed a novel method of aqueous-sample dispersive liquid-liquid microextraction (AqS-DLLME) followed by sweeping micellar electrokinetic chromatography-tandem mass spectrometry (MEKC-MS/MS) for simultaneous determination of breast cancer drugs letrozole, anastrozole, palbociclib, ribociclib, abemaciclib, and fulvestrant in human plasma. Coupling of MEKC to MS was possible due to the use of ammonium perfluorooctanoate (APFO) as a volatile surfactant. The MEKC and MS conditions were optimized to achieve a fast, sensitive, selective, and green analysis enabling full separation of the analytes within 16 min. Electrophoretic buffer was 125 mM APFO at apparent pH 10.5 in 32 % MeOH, while sheath liquid was 70 % MeOH with 0.2 % formic acid, delivered at 10 µL/min. Excellent extraction recoveries from plasma ranging from 89.4 to 104.9 % were obtained with a combination of protein precipitation and DLLME. The developed method was validated according to the ICH guidelines. Remarkable selectivity, accuracy (bias < 6.7 %), precision (RSD < 15.8 %), and stability (bias < 10.4 %) with insignificant matrix effect (RSD < 14.0 %) and no carry-over were obtained over a wide range of concentrations. Linearity with inter-day slope RSD lower than 8.7 % was demonstrated. With this method, very low concentrations could be detected after the injection of only 68.7 nL of the sample. The method was applied to plasma samples from six women currently receiving breast cancer treatment. Determined concentrations of the drugs of interest agreed with concentrations found in clinical studies, thus proving the suitability of the developed method for therapeutic drug monitoring as a superior alternative to published LC-MS methods.

Analysis of opiates in urine using microextraction by packed sorbent and gas Chromatography- Tandem mass spectrometry

Opiates recreational consumption has always been a concern in society, public health, and in clinical toxicology analysis. The aim of this study was to develop and fully validate an analytical method, which was simple and rapid for the determination of tramadol, codeine, morphine, 6- acetylcodeine, 6-monoacetylmorphine and fentanyl using gas chromatography coupled to tandem mass spectrometry. The procedure includes the use of microextraction by packed sorbent for sample clean-up. A mixed mode sorbent was used, allowing the minimal use of solvents. The method was validated in urine samples, with the ability to detect and quantify all analytes with satisfactory linearity (in the range of 1 - 1000 ng/mL for all analytes, except for fentanyl (10-1000 ng/mL)). Extraction efficiency varied from 17 to 107%, which did not impair sensitivity, taking into account the low LLOQs obtained (1 ng/ mL for all analytes; and 10 ng/mL for fentanyl). The developed procedure proved to be fast, selective, and accurate for use in routine analysis, with a low volume of sample (250 µL).

The Evolution Toward Designer Benzodiazepines in Drug-Facilitated Sexual Assault Cases

Drug-facilitated sexual assault (DFSA) is a crime where the victim is unable to provide sexual consent due to incapacitation resulting from alcohol or drug consumption. Due to the large number of substances possibly used in DFSA, including illicit, prescription and over-the-counter drugs, DFSA faces many toxicological challenges. Benzodiazepines (BZDs) are ideal candidates for DFSA, as they are active at low doses, have a fast onset of action and can be easily administered orally. The last decade has seen the emergence of designer benzodiazepines (DBZDs), which show slight modifications compared with BZDs and similar pharmacological effects but are not controlled under the international drug control system. DBZDs represent an additional challenge due to the number of new entities regularly appearing in the market, their possibly higher potency and the limited knowledge available on their pharmacokinetic and pharmacodynamics properties. Many BZDs and DBZDs have a short half-life, leading to rapid metabolism and excretion. The low concentrations and short time windows for the detection of BZD in body fluids require the use of highly sensitive analysis methods to enable the detection of drugs and their respective metabolites. This review discusses the current state of the toxicological analysis of BZDs and DBZDs in forensic casework and their pharmacokinetic properties (i.e., absorption, distribution, metabolism, and elimination), as well as their analysis in biosamples typically encountered in DFSA (i.e., blood, urine and hair).

Membrane-based liquid-phase microextraction of basic pharmaceuticals - A study on the optimal extraction window

The present paper defines the optimal extraction window (OEW) for three-phase membrane-based liquid-phase microextraction (MP-LPME) in terms of analyte polarity (log P), and anchors this to existing theories for equilibrium partitioning and kinetics. Using deep eutectic solvents (DES) as supported liquid membranes (SLM), we investigated how the OEW was affected by ionic-, hydrogen bond and π-π interactions between the SLM and analyte. Eleven basic model analytes in the range -0.4 < log P < 5.0 were extracted by MB-LPME in a 96-well format. Extraction was performed from 250 µL standard solution in 25 mM phosphate buffer (pH 7.0) into 50 µL of 10 mM HCl acceptor solution (pH 2.0) with mixtures of coumarin, camphor, DL-menthol, and thymol, with and without the ionic carrier di(2-ethylhexyl) phosphate (DEHP), as the SLM. The OEW with pure DES was in the range 2 < log P < 5, and low SLM aromaticity was favorable for the extraction of non-polar analytes. Here, extraction recoveries up to 98% were obtained. Upon addition of DEHP to the SLMs, the OEW shifted to the range -0.5 < log P < 2, and a combination of 5% DEHP and moderate aromaticity resulted in extraction recoveries up to 80% for the polar analytes. Extraction with ionic carrier was inefficient for the non-polar analytes, due to excessive trapping in the SLM. The results from our study show that LPME performs optimally in a relatively narrow log P-window of ≈ 2-3 units and that the OEW is primarily affected by ionic carrier and aromaticity.

Dispersive liquid-liquid microextraction of 11-nor-Δ9-tetrahydrocannabinol-carboxylic acid applied to urine testing

Aim: THC-COOH is the major metabolite of Δ⁹-tetrahydrocannabinol commonly tested in urine to determine cannabis intake. In this study, a method based on dispersive liquid-liquid microextraction was developed for testing THC-COOH in urine. Materials & methods: Hydrolyzed urine specimens were extracted via dispersive liquid-liquid microextraction with acetonitrile (disperser solvent) and chloroform (extraction solvent). Derivatization was performed with N,O-Bis(trimethylsilyl)trifluoroacetamide with 1% trichloro(chloromethyl)silane. Analysis was performed by GC-MS/MS. Results: The method showed acceptable linearity (5-500 ng/ml), imprecision (<10.5%) and bias (<4.9%). Limits of detection and quantitation were 1 and 5 ng/ml, respectively. Twenty-four authentic samples were analyzed, with 22 samples being positive for THC-COOH. Conclusion: The proposed method is more environmentally friendly and provided good sensitivity, selectivity and reproducibility.

Application of a Low Transition Temperature Mixture for the Dispersive Liquid-Liquid Microextraction of Illicit Drugs from Urine Samples

The use of psychoactive substances is a serious problem in today’s society and reliable methods of analysis are necessary to confirm their occurrence in biological matrices. In this work, a green sample preparation technique prior to HPLC-MS analysis was successfully applied to the extraction of 14 illicit drugs from urine samples. The isolation procedure was a dispersive liquid–liquid microextraction based on the use of a low transition temperature mixture (LTTM), composed of choline chloride and sesamol in a molar ratio 1:3 as the extracting solvent. This mixture was classified as LTTM after a thorough investigation carried out by FTIR and DSC, which recorded a glass transition temperature at −71 °C. The extraction procedure was optimized and validated according to the main Food and Drug Administration (FDA) guidelines for bioanalytical methods, obtaining good figures of merit for all parameters: the estimated lower limit of quantitation (LLOQ) values were between 0.01 µg L⁻¹ (bk-MMBDB) and 0.37 µg L⁻¹ (PMA); recoveries, evaluated at very low spike levels (in the ng-µg L⁻¹ range), spanned from 55% (MBDB) to 100% (bk-MMBDB and MDPV); finally, both within-run and between-run precisions were lower than 20% (LLOQ) and 15% (10xLLOQ).

Application of Microextraction-Based Techniques for Screening-Controlled Drugs in Forensic Context-A Review

The analysis of controlled drugs in forensic matrices, i.e., urine, blood, plasma, saliva, and hair, is one of the current hot topics in the clinical and toxicological context. The use of microextraction-based approaches has gained considerable notoriety, mainly due to the great simplicity, cost-benefit, and environmental sustainability. For this reason, the application of these innovative techniques has become more relevant than ever in programs for monitoring priority substances such as the main illicit drugs, e.g., opioids, stimulants, cannabinoids, hallucinogens, dissociative drugs, and related compounds. The present contribution aims to make a comprehensive review on the state-of-the art advantages and future trends on the application of microextraction-based techniques for screening-controlled drugs in the forensic context.

Neuropathology changed by 3- and 6-months low-level PM2.5 inhalation exposure in spontaneously hypertensive rats

BACKGROUND

Epidemiological evidence has linked fine particulate matter (PM2.5) to neurodegenerative diseases; however, the toxicological evidence remains unclear. The objective of this study was to investigate the effects of PM2.5 on neuropathophysiology in a hypertensive animal model. We examined behavioral alterations (Morris water maze), lipid peroxidation (malondialdehyde (MDA)), tau and autophagy expressions, neuron death, and caspase-3 levels after 3 and 6 months of whole-body exposure to urban PM2.5 in spontaneously hypertensive (SH) rats.

RESULTS

SH rats were exposed to S-, K-, Si-, and Fe-dominated PM2.5 at 8.6 ± 2.5 and 10.8 ± 3.8 μg/m3 for 3 and 6 months, respectively. We observed no significant alterations in the escape latency, distance moved, mean area crossing, mean time spent, or mean swimming velocity after PM2.5 exposure. Notably, levels of MDA had significantly increased in the olfactory bulb, hippocampus, and cortex after 6 months of PM2.5 exposure (p < 0.05). We observed that 3 months of exposure to PM2.5 caused significantly higher expressions of t-tau and p-tau in the olfactory bulb (p < 0.05) but not in other brain regions. Beclin 1 was overexpressed in the hippocampus with 3 months of PM2.5 exposure, but significantly decreased in the cortex with 6 months exposure to PM2.5. Neuron numbers had decreased with caspase-3 activation in the cerebellum, hippocampus, and cortex after 6 months of PM2.5 exposure.

CONCLUSIONS

Chronic exposure to low-level PM2.5 could accelerate the development of neurodegenerative pathologies in subjects with hypertension.

Dispersive liquid-liquid microextraction followed by green high-performance liquid chromatography for fluconazole determination in cerebrospinal fluid with the aid of chemometric tools

A new method, simple and fast, for fluconazole (FLU) quantification in cerebrospinal fluid (CSF) samples using dispersive liquid-liquid microextraction (DLLME) and an eco-friendly mobile phase for HPLC-PDA was developed. The study of DLLME extraction condition covered the investigation of 12 combinations of extraction and disperser solvents followed by a fractional factorial design 2(7-3) to determine the influence of seven factors. After this stage, a central composite design was performed for three factors and a response surface was obtained. Aiming a compromise between a good recovery and a low organic solvent use it was established an extraction condition that consists of: 100 μL of chloroform, 100 μL of isopropyl alcohol, 200 μL of CSF, 200 μL of 50 mM phosphate buffer pH 7.3 and centrifugation for 5 min at 2200g and 4 °C. The HPLC analysis used an Ascentis® Express C18 column (100 mm × 4.6 mm, 2.7 μm) and an Ascentis® Express C18 guard column (3 mm × 4.6 mm, 2.7 μm), ethanol : water (15 : 85, v/v) as mobile phase, temperature of 45 °C, flow rate of 0.8 mL min-1 and phenacetin as internal standard. The method validation was performed according to European Agency's Guideline on Bioanalytical Validation Methodology and a linear range was obtained from 0.25 to 62.5 μg mL-1, with precision and accuracy within the recommended limits and recovery of 70% for FLU and 81% for phenacetin. Samples were stable in the studies performed and the method showed to be selective and with no carryover effect. The feasibility of the obtained method was confirmed by FLU determination at a CSF from a patient who was treated for neuromycosis. Therefore, here is described a method that meets many principles of green analytical chemistry and is useful for FLU therapeutic monitoring.

Recent Progresses in Sensitive Determination of Drugs of Abuse by Capillary Electrophoresis

Background:

Today, “drugs of abuse” pose serious social problems such as many crimes, medical treatment costs, and economic repercussions. Several worldwide clinical laboratories use analytical separation methods to analyze their patient samples for drugs and poisons. In this way, they provide qualitative and quantitative data on the substances in various biological matrices (e.g., urine, plasma or serum, saliva, and breath).

Methods:

An extensive review of the published articles indicates that the use of Capillary Electrophoresis (CE) coupled with sensitivity enhancing methods is a very attractive area of interest in the assay of drugs of abuse.

Results:

This review was prepared to have a comprehensive study on applications of sensitivity enhancing methods on the determination of drugs of abuse especially from 2007 to present. The sample preconcentration approaches almost address all methods from online preconcentration (both electrophoretic and chromatographic-based methods) to offline preconcentration. Furthermore, detection system modification and capillary column fabrications were investigated in order to increase the detection sensitivity of complex samples in CE.

Conclusion:

The present review summarizes the most recent developments in the detection of drugs of abuse using CE. Although CE still has a limitation in sensitive detection, several publications in recent years have proposed valuable methods to overcome this problem.

An integrated microfluidic device for solid-phase extraction and spectrophotometric detection of opium alkaloids in urine samples

A novel lab-on-chip integrated microfluidic device for solid-phase extraction (SPE) and spectrophotometric detection of morphine (MOR), codeine (COD), and papaverine (PAP) was developed. The extracted analytes were analyzed with a miniature UV-Vis spectrophotometer. The SPE adsorptive phase composed of polyurethane/polyaniline (PU/PANI) nanofibers was fabricated by electrospinning and in situ oxidative polymerization techniques. The sorbent was characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The main factors of extraction such as desorption conditions, pH, salt effect, and extraction time were investigated. The partial least square (PLS) regression was applied to improve the quantification of analytes. The linear dynamic ranges (LDRs) for MOR, COD, and PAP were 4-240, 4-210, and 1-150 ng mL^-1, respectively. Finally, the proposed method was successfully applied for the determination of MOR, COD, and PAP in human urine samples and the extraction recoveries were obtained in the range of 66.7-85.0% with RSDs < 8.3%.

Developing a miniaturized setup for in-tube simultaneous determination of three alkaloids using electromembrane extraction in combination with ultraviolet spectrophotometry

Herein, electromembrane extraction was combined with ultraviolet spectrophotometry using a customized manifold for preconcentration and simultaneous determination of morphine, codeine, and papaverine in water and human urine samples. Absorption spectra of the extracts were recorded inside the lumen of the hollow fiber using two fiber optics connected to a miniature spectrophotometer. Partial least squares regression was applied to resolve the overlapped spectra of the analytes. Performance of the model was validated by an independent test set. Central composite design was applied to optimize the extraction parameters. The optimized extraction conditions are as follows; supporting liquid membrane: 2-nitrophenyl octyl ether containing 15% v/v bis(2-ethylhexyl) phosphate, applied voltage: 80 V, donor pH: 3.0, acceptor pH: 1.0, extraction time: 20 min. Finally, the optimized extraction method was validated for determination of the mentioned alkaloids in human urine samples. The method showed good linearity (R²  > 0.995) for all of the mentioned alkaloids. The limits of detection for morphine, codeine, and papaverine in diluted human urine were found to be 0.6, 1.1, and 0.6 ng/mL, respectively with acceptable relative standard deviations. Enrichment factors of 104, 108, and 102 were achieved for morphine, codeine, and papaverine, respectively.

Recent advances in microextraction procedures for determination of amphetamines in biological samples

Amphetamine and its related derivatives have stimulant and hallucinogenic properties. Illegal use of these drugs is an increasing global problem resulting in significant public health and legal problems. Deaths have been reported after intake of these drugs due to overdose. It is important to determine the type and concentration of illicit drugs in biological samples. These compounds are found in complex matrices at low concentration levels. The microextraction techniques are dominant sample preparation procedure and they are widely accepted as the most labor-intensive part of the bioanalytical process. For this purpose, a survey of recent published advances in microextraction procedures for quantification of amphetamines in biological samples found in the different databases from 2008 to date will be conducted.

Current direction and advances in analytical sample extraction techniques for drugs with special emphasis on bioanalysis

Analytical techniques may not be compatible or sufficiently sensitive to the analytes, unless it undergoes a specific sample extraction procedure. Sample extraction can be considered as one of the key steps in analysis. Analysis of a poorly treated sample may produce inferior quality of analytical data. Continuous advancement and development of newer sample extraction techniques such as solid phase microextraction, ultrasound, magnetically and microwave assisted magnetic extraction; electro-membrane extraction and dried blood spotting are to address the shortcomings of the existing techniques and to provide more automation, minimizing preparation time and make them high throughput. This review summarizes the suitability of application of the advanced sample preparation techniques available for chemical and bioanalysis in a comprehensive manner. This review also provides a scientific guidance for selecting the appropriate sample extraction technique based on sample type.

Determination of d-amphetamine and diphenhydramine in beagle dog plasma by a 96-well formatted liquid-liquid extraction and capillary zone electrophoresis with field-amplified sample stacking

This paper describes a method for quantification of d-amphetamine and diphenhydramine in beagle dog plasma by organic solvent field-amplified sample stacking (FASS)-capillary zone electrophoresis (CZE), using amlodipine as the internal standard. The separation was carried out at 25 °C in a 40.2 cm × 75 μm fused-silica capillary with an applied voltage of 20 kV using 25 mM phosphate-18.75 mM borate (pH 3.5). The detection wavelength was 200 nm. Clean-up and preconcentration of plasma biosamples were developed by 96-well formatted liquid- liquid extraction (LLE). In this study, the peak areas of d-amphetamine, diphenhydramine and amlodipine in the plasma sample increased by the factor of 48, 67 and 43 compared to the CZE without sample stacking. The method was suitably validated with respect to stability, specificity, linearity, lower limit of quantitation, accuracy, precision and extraction recovery. The calibration graph was linear from 2 to 500 ng/ml for d-amphetamine and 2-5000 ng/ml for diphenhydramine. All the validation data were within the required limits. Compared with the LC/MS/MS method that we previously established, there was no significant difference between the two methods in validation characteristics, except the LLOQs. The developed method was successfully applied to the evaluation of pharmacokinetic study of the Quick-Acting Anti-Motion Capsules (QAAMC) in beagle dogs.

Determination of Vancomycin in Human Serum by Cyclodextrin-Micellar Electrokinetic Capillary Chromatography (CD-MEKC) and Application for PDAP Patients

A simple and sensitive cyclodextrin-micellar electrokinetic capillary chromatography (CD-MEKC) method with UV detection was developed and validated for the determination of vancomycin (VCM) in serum. The separation was achieved in 14 min at 25 °C with a fused-silica capillary column of 40.2 cm × 50 mm i.d. (effective length 30.2 cm) and a run buffer containing 25 mM borate buffer with 50 mM sodium dodecylsulfonate (SDS) (pH 9.5) and 2% sulfobutyl-β-cyclodextrin (sulfobutyl-β-CD). Under optimal conditions for biological samples, good separations with high efficiency and short analysis time were achieved. Several parameters affecting the drug separation from biological matrices were studied, including buffer types, concentrations, and pHs. The methods were validated over the range of 0.9998-99.98 µg/mL. Calibration curves of VCM also showed good linearity (r² > 0.999). Intra- and interday precisions (relative standard deviation, RSD) were less than 5.80% and 7.38%, and lower limit of quantification (LLOQ) were lower than 1.0 μg/mL. The mean recoveries ranged between 84.03% and 91.69%. The method was successfully applied for monitoring VCM concentrations in serum of patients with peritoneal dialysis-associated peritonitis (PDAP). The assay should be applicable to pharmacokinetic studies and routine therapeutic drug monitoring of this drug in serum.

Sensitive determination of methadone in human serum and urine by dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet followed by HPLC-UV

Dispersive liquid-liquid microextraction based on solidification of floating organic droplet was developed for the extraction of methadone and determination by high-performance liquid chromatography with UV detection. In this method, no microsyringe or fiber is required to support the organic microdrop due to the usage of an organic solvent with a low density and appropriate melting point. Furthermore, the extractant droplet can be collected easily by solidifying it at low temperature. 1-Undecanol and methanol were chosen as extraction and disperser solvents, respectively. Parameters that influence extraction efficiency, i.e. volumes of extracting and dispersing solvents, pH, and salt effect, were optimized by using response surface methodology. Under optimal conditions, enrichment factor for methadone was 134 and 160 in serum and urine samples, respectively. The limit of detection was 3.34 ng/mmL in serum and 1.67 ng/mL in urine samples. Compared with the traditional dispersive liquid-liquid microextraction, the proposed method obtained lower limit of detection. Moreover, the solidification of floating organic solvent facilitated the phase transfer. And most importantly, it avoided using high-density and toxic solvents of traditional dispersive liquid-liquid microextraction method. The proposed method was successfully applied to the determination of methadone in serum and urine samples of an addicted individual under methadone therapy.

Application of hollow fiber liquid phase microextraction and dispersive liquid–liquid microextraction techniques in analytical toxicology

The recent developments in hollow fiber liquid phase microextraction and dispersive liquid –liquid microextraction are reviewed. Applications of these newly emerging developments in extraction and preconcentration of a vast category of compounds including heavy metals, pesticides, pharmaceuticals and abused drugs in complex matrices (environmental and biological matrices) are reviewed and discussed. The new developments in these techniques including the use of solvents lighter than water, ionic liquids and supramolecular solvents are also considered. Applications of these new solvents reduce the use of toxic solvents and eliminate the centrifugation step, which reduces the extraction time.

In-line coupling of single-drop microextraction with capillary electrophoresis-mass spectrometry

Single-drop microextraction (SDME) was in-line coupled with capillary electrophoresis-mass spectrometry to provide sample cleanup and enrichment simultaneously. Since there is no outlet vial in a conventional capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) configuration, it is not easy to hang a single drop in the capillary inlet for extraction. We overcame the difficulty of coupling SDME and CE-MS by using a temporary outlet reservoir. Basic drugs such as methamphetamine, amphetamine, phenethylamine, methoxyphenamine, and mephentermine were extracted from a basic sample solution to an acidic acceptor drop covered with a thin octanol layer formed at the capillary inlet tip. Compared to the CE-MS method in the multiple reaction monitoring (MRM) mode, the in-line SDME-CE-MS/MS technique showed 130∼150-fold enrichment in 10 min. The relative standard deviations (RSDs) of peak height ranged from 9 to 13 %. RSDs can be reduced from 4 to 6 % using mephentermine as an internal standard. We examined the pretreatment of sample with and without SDME from human urine under the full-scan mode, which confirmed that many metabolites were cleaned up by the selective extraction method of SDME. Even if the analytes from human urine were analyzed under the MRM mode used as a mass filter, there was an isobaric compound causing a disturbance to the analysis. However, in-line SDME-CE-MS/MS made it possible to perform a sample cleanup as well as sample enrichment. The research is extremely advantageous in that it is rapid, convenient, and highly sensitive for the analysis of biological samples using a commercially available instrument.

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.

Detection limit enhancement of antiarrhythmic drugs in human plasma using capillary electrophoresis with dispersive liquid–liquid microextraction and field-amplified sample stacking method

Background: A new capillary zone electrophoresis (CZE) with ultraviolet detection method has been developed and validated for the analysis of four antiarrhythmic drugs in human plasma samples. Methods: In this study, a dispersive liquid–liquid microextraction (DLLME) coupled with field-amplified sample stacking (FASS) was employed for biological samples clean-up and sensitivity enhancement in CZE. Results: Under optimum DLLME-FASS-CZE conditions, enhancement factors were in the range of 157–314. The method was validated over the concentration range of 20–800 ng/ml in human plasma. Inter- and intra-day precision and the accuracy were less than 20%; the detection limits ranged from 2.5 to 4.7 ng/ml. Furthermore, the validated method was successfully applied to the detection of studied drugs in patients’ plasma samples.

Sensitive determination of atorvastatin in human plasma by dispersive liquid-liquid microextraction and solidification of floating organic drop followed by high-performance liquid chromatography

A novel and sensitive dispersive liquid-liquid microextraction method based on the solidification of the floating organic drop combined with high-performance liquid chromatography and ultraviolet detection was used for the determination of atorvastatine in blood serum samples. The chromatographic separation of atorvastatin was carried out using methanol as the mobile phase organic modifier. Various parameters affecting the extraction efficiency were optimized, such as the kind and volume of extraction solvent (1-undecanol) and disperser solvent (acetonitrile), pH, and the extraction time. The calibration curve was linear in the range of 0.2-6000 μg/L of atorvastatin (r(2) = 0.995) with a limit of detection of 0.07 μg/L. The relative standard deviation for 100 μg/L of atorvastatin in human plasma was 8.4% (n = 4). The recoveries of plasma samples spiked with atorvastatin were in the range of 98.8-113.8%. The obtained results showed that the proposed method is fast, simple, and reliable for the determination of very low concentrations of atorvastatin in human plasma samples.

Analysis of fentanyl in urine by DLLME-GC-MS

Fentanyl is a synthetic narcotic anesthetic ∼80-100 times more potent than morphine. Owing to the potential for its abuse, the drug may be included in a forensic toxicology work-up, which requires fast, precise and accurate measurements. Here, the stability of fentanyl was assessed when stored at three different temperatures (-20, 4 and 25°C) in synthetic urine. Stability at those three temperatures was demonstrated over 12 weeks upon analysis by gas chromatography-mass spectrometry with a deuterated internal standard (fentanyl-D5) utilizing three different extraction techniques: liquid-liquid extraction (LLE), solid-phase extraction and dispersed liquid-liquid microextraction (DLLME). The DLLME method was then optimized before use in the analysis of fentanyl in urine samples obtained from autopsy cases at the El Paso County Coroner's Office. Accuracy of the DLLME method was assessed by completing spike and recovery studies at three different fortification levels (10, 100 and 250 ng/mL) with excellent recovery (89.9-102.6%). The excellent comparability between DLLME and LLE is demonstrated (Bland-Altman difference plot with a mean difference of 4.9 ng/mL) and the use of this methodology in the analysis of forensically relevant samples is discussed.

Multi-target screening of biological samples using LC–MS/MS: focus on chromatographic innovations

Multi-target screening of biological fluids is a key tool in clinical and forensic toxicology. A complete toxicological analysis encompasses the sample preparation, the chromatographic separation and the detection. The present review briefly covers the new trends in sample preparation and detection and mainly focuses on the chromatographic stage, since a lot of technical improvements have been proposed over the last years. Among them, columns packed with sub-2 μm fully porous particles and sub-3 μm core-shell particles allow for significant improvements of resolution and higher throughput. Even if reversed-phase LC remains the most widely used chromatographic mode for toxicological screening, hydrophilic interaction chromatography and supercritical fluid chromatography appear as promising alternatives for attaining orthogonal selectivity, retention of polar compounds, and enhanced MS sensitivity.

Rapid extraction and determination of amphetamines in human urine samples using dispersive liquid-liquid microextraction and solidification of floating organic drop followed by high performance liquid chromatography

A novel, rapid, simple and sensitive dispersive liquid-liquid microextraction method based on the solidification of floating organic drop (DLLME-SFO) combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) was used to determine amphetamine and methamphetamine in urine samples. The factors affecting the extraction efficiency of DLLME-SFO such as the kind and volume of the extraction and the disperser solvents, effect of concentration of K2CO3 and extraction time were investigated and the optimal extraction conditions were established. Under the optimum conditions (extraction solvent: 30.0μl 1-undecanol; disperser solvent: 300μl acetonitrile; buffer concentration: 2% (w/v) K2CO3 and extraction time: 1min), calibration curves are linear in the range of 10-3000μgl(-1) and limit of detections (LODs) are in the range of 2-8μgl(-1). The relative standard deviations (RSDs) for 100μgl(-1) of amphetamine and methamphetamine in diluted urine are in the range of 6.2-7.8% (n=7). The method was successfully applied for the determination of amphetamine and methamphetamine in the actual urine samples. The relative recoveries of urine samples spiked with amphetamine and methamphetamine are 87.8-113.2%. The obtained results show that DLLME-SFO combined with HPLC-UV is a fast and simple method for the determination of amphetamine and methamphetamine in urine.

Salt-assisted LLE combined with field-amplified sample stacking in CE for improved determination of beta blocker drugs in human urine

Background: A simple and sensitive CE method was developed and validated for the analysis of some beta blockers in human urine. Methods: In this study, salting-out assisted LLE combined with field-amplified sample stacking method was employed for biological sample clean-up and sensitivity enhancement in CE. Results: Under the optimal conditions good linearity (r2 ≥0.998) was obtained, within 0.025–1 µg/ml for propranolol and metoprolol, and within 0.05–1 µg/ml for carvedilol in urine samples. LODs and LLOQs ranged from 0.005 to 0.015 µg/ml, and from 0.025 to 0.05 µg/ml, respectively. The RSDs of intra- and inter-day analysis of examined compounds were less than 4.0%. The recoveries were in the range of 98–119%. Conclusion: The validated method is successfully applied to determine propranolol, metoprolol and carvedilol in human urine samples obtained from the patients who received these drugs.

Non-aqueous capillary electrophoresis for the analysis of acidic compounds using negative electrospray ionization mass spectrometry

Non-aqueous capillary electrophoresis (NACE) is an attractive CE mode, in which water solvent of the background electrolyte (BGE) is replaced by organic solvent or by a mixture of organic solvents. This substitution alters several parameters, such as the pKa, permittivity, viscosity, zeta potential, and conductivity, resulting in a modification of CE separation performance (i.e., selectivity and/or efficiency). In addition, the use of NACE is particularly well adapted to ESI-MS due to the high volatility of solvents and the low currents that are generated. Organic solvents reduce the number of side electrochemical reactions at the ESI tip, thereby allowing the stabilization of the ESI current and a decrease in background noise. All these features make NACE an interesting alternative to the aqueous capillary zone electrophoresis (CZE) mode, especially in combination with mass spectrometry (MS) detection. The aim of this work was to evaluate the use of NACE coupled to negative ESI-MS for the analysis of acidic compounds with two available CE-MS interfaces (sheath liquid and sheathless). First, NACE was compared to aqueous CZE for the analysis of several pharmaceutical acidic compounds (non-steroidal anti-inflammatory drugs, NSAIDs). Then, the separation performance and the sensitivity achieved by both interfaces were evaluated, as were the impact of the BGE and the sample composition. Finally, analyses of glucuronides in urine samples subjected to a minimal sample pre-treatment ("dilute-and-shoot") were performed by NACE-ESI-MS, and the matrix effect was evaluated. A 20- to 100-fold improvement in sensitivity was achieved using the NACE mode in combination with the sheathless interface and no matrix effect was observed regardless of the interfaces.