Solid phase micro extraction coupled with semi-microcolumn high performance liquid chromatography for the analysis of benzodiazepines in human urine

Carbon and Tin-Based Polyacrylonitrile Hybrid Architecture Solid Phase Microextraction Fiber for the Detection and Quantification of Antibiotic Compounds in Aqueous Environmental Systems

In this study, the detection and quantification of multiple classes of antibiotics in water matrices are proposed using a lab-made solid phase microextraction (SPME) fiber coupled with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The lab-made fiber was prepared using a graphene oxide (G), carbon nanotubes (C), and titanium dioxide (T) composite, namely GCT, with polyacrylonitrile (PAN) as supporting material. The detected antibiotics were enrofloxacin, sulfathiazole, erythromycin, and trimethoprim. The custom-made fiber was found to be superior compared with a commercial C18 fiber. The excellent reproducibility and lower intra-fiber relative standard deviations (RSDs 1.8% to 6.8%) and inter-fiber RSDs (4.5% to 8.8%) made it an ideal candidate for the detection of traces of antibiotics in real environmental samples. The proposed validated method provides a satisfactory limit of detection and good linear ranges with higher (>0.99) coefficient of determination in the aqueous system. Application of the method was made in different real water systems such as river, pond and tap water using the standard spiking method. Excellent sensitivity, reproducibility, lower amount of sample detection and higher recovery was found in a real water sample. Therefore, the extraction method was successfully applied to the detection and quantification of multiple classes of antibiotics in different aqueous systems with satisfactory results.

Improvement of solid phase microextraction fiber assembly and interface for liquid chromatography

Modifications were made on commercial SPME fiber assembly and SPME-LC interface to improve the applicability of SPME for LC. Polyacrylonitrile (PAN)/C18 bonded fuse silica was used as the fiber coating for LC applications because the fiber coating was not swollen in common LC solvents at room temperature. The inner tubing of SPME fiber assembly was replaced with a 457 μm outside diameter (o.d.) solid nitinol rod. And the coated fiber (o.d. 290 μm) was installed onto the nitinol rod. The inner diameter (i.d.) of the through hole of the ferrule in the SPME-LC interface was enlarged to 508 μm to accommodate the nitinol rod. The much larger inner rod protected the fiber coating from being stripped when the fiber was withdrawn from the SPME-LC interface. The system was evaluated in term of pressure test, desorption optimization, peak shape, carryovers, linear range, precision, and limit of detection (LOD) with polycyclic aromatic hydrocarbons (PAHs) as the test analytes. The results demonstrated that the improved system was robust and reliable. It overcame the drawbacks, such as leak of solvents and damage of fiber coatings, associated with current SPME fibers and SPME-LC interface. Another sealing mechanism was proposed by sealing the nitinol rod with a specially designed poly(ether ether ketone) (PEEK) fitting. The device was fabricated and tested for manual use.

Benzodiazepines: sample preparation and HPLC methods for their determination in biological samples

Benzodiazepines (BDZs) belong to a group of substances known for their sedative, antidepressive, muscle relaxant, tranquilizer, hypnotic and anticonvulsant properties. Their determination in biological fluids is essential in clinical assays as well as in forensics and toxicological studies. Researchers focus on the development of rapid, accurate, precise and sensitive methods for the determination of BDZs and their metabolites. A large number of analytical methods using different techniques have been reported, but none can be considered as the method of choice. BDZs are usually present at trace levels (microgram or nanogram per milliliter) in a complex biological matrix and the potentially interfering compounds must be isolated by various extraction techniques before analysis. An extended and comprehensive review is presented herein, focusing on sample preparation (pretreatment and extraction) and HPLC conditions applied by different authors. These methods enable bioanalysts to achieve detection limits down to 1-2 ng/ml using UV/diode array detection, readily available in most laboratories, and better than 1 ng/ml using electron capture detection, which is lower than that obtained using a nitrogen phosphorus detector. MS interfaced with electrospray ionization offered a similar sensitivity, while negative chemical ionization MS or sonic spray ionization MS provided sensitivity down to 0.1 ng/ml.

Strategies for interfacing solid-phase microextraction with liquid chromatography

Solid-phase microextraction (SPME) techniques are equally applicable to both volatile and non-volatile analytes, but the progress in applications to gas-phase separations has outpaced that of liquid-phase separations. The interfacing of SPME to gas chromatographic equipment has been straight-forward, requiring little modification of existing equipment. The requirement of solvent desorption for non-volatile or thermally labile analytes has, however, proven challenging for interfacing SPME with liquid-phase separations. Numerous options to achieve this have been described in the literature over the past decade, with applications in several different areas of analysis. To date, no single strategy or interface device design has proven optimal. During method development analysts must select the most appropriate interfacing technique among the options available. Out of these options three general strategies have emerged: (1) use of a manual injection interface tee; (2) in-tube SPME; and (3) off-line desorption followed by conventional liquid injection. In addition, there has been interest in coupling SPME directly to electrospray ionisation and matrix-assisted laser desorption ionisation (MALDI) for mass spectrometry. Several examples of each of these strategies are reviewed here, and an overview of their use and application is presented.

Combining stir bar sorptive extraction and MEKC for the determination of polynuclear aromatic hydrocarbons in environmental and biological matrices

In this work, stir bar sorptive extraction and liquid desorption was combined with MEKC and diode-array detection (SBSE-LD-MEKC-DAD) for the determination of polynuclear aromatic hydrocarbons (PAHs) in aqueous medium, using biphenyl, fluorene, anthracene, phenanthrene, fluoranthene and pyrene as model compounds. MEKC-DAD conditions and parameters affecting SBSE-LD efficiency are fully discussed. Assays performed on aqueous samples spiked at trace levels, yielded recoveries ranging from 55.5 +/- 6.1% (pyrene) to 70.7 +/- 7.1% (anthracene), under optimized experimental conditions. The methodology proved to be nearly described by the octanol-water partition coefficients (K(PDMS/W) approximately K(O/W)). The analytical performance showed good precision (<12.0%), suitable detection limits (2-11 microg/L) and convenient linear dynamic ranges (r(2)>0.99) from 5 to 25 microg/L for anthracene and 25 to 125 microg/L for the remaining compounds. The application of the proposed methodology to environmental water, sediments and fish bile matrices demonstrated good selectivity and accuracy. SBSE-LD combined with MEKC-DAD was shown to be an easy, reliable and robustness methodology, as well as a good analytical alternative to monitor environmental priority pollutants.

Liquid Chromatography–Tandem Mass Spectrometry for Detection of Low Concentrations of 21 Benzodiazepines, Metabolites, and Analogs in Urine: Method with Forensic Applications

Background: Commonly used methods for detecting benzodiazepines (BZPs) and BZP-like substances, such as zolpidem and zopiclone, may not detect low concentrations of these drugs. We developed a liquid chromatographic–tandem mass spectrometric method for identifying these drugs and their relevant metabolites.

Methods: We extracted BZPs from urine by solid-phase extraction with a mixed-mode phase (OASIS® HLB cartridges). Chromatographic separation was performed with a Waters XTerra MS C18 [150 × 2.1 mm (i.d.); bead size, 5 μm] reversed-phase column with deuterated analogs of the analytes as internal standards (IS). Detection was performed with a triple-quadruple mass spectrometer that monitored 2 specific transitions per compound in the electrospray, positive-ion selected-reaction monitoring mode. We tested this technique on urine samples from 12 healthy volunteers and 1 forensic sample obtained in a case of alleged drug-facilitated sexual assault.

Results: Chromatographic separation was achieved within 18 min. The linear dynamic ranges extended from 0.02 or 0.1 μg/L (depending on the drug or metabolite) to 50 μg/L. Extraction recovery (range) was 77%–110%. Limits of detection were ≤0.05 μg/L. No ion suppression was seen except for alprazolam, for which baseline decreased by almost 20%. In the forensic urine sample, the method detected alprazolam (3.5 μg/L) and its characteristic metabolite, α-hydroxyalprazolam (0.17 μg/L).

Conclusion: This method measured low concentrations of BZPs and BZP-like substances and might be useful for analyses of urine in suspected drug-facilitated sexual assault cases.

Development of immunoaffinity solid phase microextraction probes for analysis of sub ng/mL concentrations of 7-aminoflunitrazepam in urine

We report on the development of solid phase microextraction probes for drug analysis, prepared with antibodies specific for benzodiazepines covalently immobilized to the surface. In the technique, immobilized antibody probes are exposed to a sample containing the drug for 30 min. Extracted drugs are subsequently desorbed from the probes in 500 microL of methanolic desorption solution, which is dried, reconstituted in a small volume of injection solution and analysed by LC-MS/MS. The antibodies were characterized both before and after immobilization, to facilitate the rational selection of antibodies for such analyses. Polyclonal and monoclonal antibodies were compared as was the impact of affinity purification of the polyclonal antibody to isolate the drug-specific fraction. The probes were evaluated for utility in analyzing 7-aminoflunitrazepam at sub ng/mL concentrations in urine, which is expected to be found several days after a single oral dose of 2 mg of flunitrazepam. Such analyses are required in monitoring for abuse of this drug, both in terms of 'club drug' use and in cases of drug-facilitated sexual assault. In these cases drug concentrations in blood and urine are much lower than in chronic abuse cases and are difficult to analyse by conventional methods. The method developed has a limit of detection of 0.02 ng/mL, with accuracy ranging from 1% to 27% and precision (% R.S.D.) ranging from 2% to 10% between the lower and upper limits of quantitation for the analysis of 7-aminoflunitrazepam in urine. The dynamic range of the method is from 0.02 ng/mL, which is limited by the instrument sensitivity, to 0.5 ng/mL, which is approaching the capacity of the probes. This would allow for quantitative analysis of samples at concentrations below that measurable by many other methods for general benzodiazepines analysis from urine, and a highly selective screen for samples at higher concentrations. The method has similar limits of detection to the most sensitive literature methods specifically designed for such analysis but with the advantage of significantly simplified sample preparation. This simplification makes the technique more amenable for use by both professionals and non-professionals.

Monitoring of drugs and metabolites in whole blood by restricted-access solid-phase microextraction coupled to liquid chromatography–mass spectrometry

Robust biocompatible solid-phase microextraction (SPME) devices were prepared using various alkyldiol-silica (ADS) restricted-access materials (RAM) as the SPME coating. The ADS-SPME approach was able to simultaneously fractionate the protein component from a biological sample, while directly extracting diazepam and the major metabolites N-desmethyldiazepam, oxazepam and temazepam, and overcame the present disadvantages of direct sampling in biological matrices by SPME. The devices were interfaced with an LC-MS system and an isocratic mobile phase was used to desorb, separate, and quantify the analytes. The calculated diazepam, nordiazepam, temazepam, and oxazepam detection limits were 20, 20, 30, and 35 ng/ml in heparinized blood, respectively. The method was confirmed to be linear over the range of 50-1000 ng/ml with an average linear coefficient (R2) value of 0.996. The injection repeatability and intra-assay precision of the method were evaluated over ten injections at concentrations of 50, 200, and 500 ng/ml, resulting in a R.S.D. of ca. 10%. The robustness of the ADS-SPME device was evaluated for future use in in vivo studies, providing many direct extractions and subsequent determination of benzodiazepines in blood. For the extraction of the peptides angiotensin I, II, and III from blood, a novel restricted access material with cation exchange properties was evaluated. The ion-exchange diol silica improved the extraction efficiency of peptides relative to the conventional ADS material with reversed phase extraction centers.

Direct injection HPLC method for the determination of selected benzodiazepines in plasma using a Hisep column

A direct plasma injection HPLC method has been developed for the determination of selected benzodiazepines (nitrazepam, clobazam, oxazepam, lorazepam). The method uses an analytical hydrophobic shielded phase (Hisep) column equipped with a Hisep guard column, are easy to perform and requires 20 ul of a filtered plasma sample. The chromatographic run time is less than 15 min using a mobile phase of 15:85 v/v acetonitrile-0.18 M ammonium acetate pH 2.5. The method is good for 175 injections before replacement of the guard column. The method was linear in the range 0.5-18 ug ml(-1) (r>0.99, n=6) for the analytes with R.S.D. less than 10.82%. Interday and intraday variability were found to be less than 14%. The limits of detection and quantitation were 0.16 (s/n>3) and 0.5 ug ml(-1) (s/n>10), respectively, for each of the four benzodiazepines.

Miniaturized sample preparation combined with liquid phase separations

Miniaturized sample preparation methods designed as the sample pretreatment for liquid phase separations, such as liquid chromatography, capillary electrophoresis and capillary electrochromatography, have been reviewed especially for the on-line coupling of the sample preparation process and the separation process. The development of the desorption interfaces for the effective combining of the sample preparation and subsequent liquid phase separations is briefly described along with the applications of the combined analytical systems to the analysis of complex sample mixtures such as biological and environmental matrices. Novel use of fine polymeric filaments as the extraction medium for microscale liquid phase separation methods are investigated and a comparison is made with other sample preparation techniques. Polymer coating onto the fibrous material is also introduced to further develop microscale sample preparation methods with improved extraction performance. Several other microscale sample preparation methods having a potential compatibility to the liquid phase separations are also described for future applications of these techniques.

Coupling solid-phase microextraction and high-performance liquid chromatography for direct and sensitive determination of halogenated fungicides in wine

A solid-phase microextraction (SPME) method coupled to high-performance liquid chromatography with diode array detection (HPLC-DAD) for the analysis of six organochlorine fungicides (nuarimol, triadimenol, triadimefon, folpet, vinclozolin and penconazole) in wine was developed. For this purpose, polydimethylsiloxane-divinylbenzene-coated fibers were utilized and all factors affecting throughput, precision, and accuracy of the SPME method were investigated and optimized. These factors include: matrix influence, extraction and desorption time, percentage of ethanol, pH, salt effect and desorption mode. The performed analytical procedure showed detectability ranging from 4 to 27 microg l(-1) and precision from 2.4 to 14.2% (as intra-day relative standard deviation, RSD) and 4.7-25.7% (as inter-day RSD) depending on the fungicide. The results demonstrate the suitability of the SPME-HPLC-DAD method to analyze these organochlorine fungicides in red wine.

Polymer-coated fibrous extraction medium for sample preparation coupled to microcolumn liquid-phase separations

Polymer-coated fibrous material has been introduced as the extraction medium for a miniaturized sample preparation method being coupled with microcolumn liquid chromatography. The preconcentration and the subsequent liquid chromatographic separation of tricyclic antidepressants (TCAs) drugs, amitriptyline, imipramine, nortriptyline and desipramine, was carried out with the hyphenated system. Several basic experimental parameters, such as extraction and separation conditions, were investigated along with the applicability of the method for the analysis of biological fluids. The results clearly showed that the on-line coupled system could be a powerful tool for the analysis of complex mixtures in biological matrix without a large solvent consumption and specially designed instruments. The lowest limit of quantification was quite acceptable for the analysis of TCAs in clinical and forensic situations.

A SPME-GC procedure for monitoring peppermint flavor in tablets

A method was developed using solid-phase microextraction (SPME) and gas chromatography to monitor the peppermint flavor loss in a taste-masked tablet formulation. This was accomplished by headspace sampling of two major components of peppermint: menthone and menthol. It was found that the excipients from the tablet produced an important matrix effect and that standard addition analysis was necessary for improved accuracy of the determination. The method was shown to be specific and precise. Furthermore, the method produced acceptable results with adequate quantitation limits to determine peppermint flavors in taste-masked tablets. The optimized extraction procedure was successfully used to monitor the stability of peppermint flavor in an oral solid formulation. The accelerated stability studies of the tablet showed that the menthone and menthol was lost in an exponential manner and levels off after several days of heat exposure.

Bio-compatible in-tube solid-phase microextraction capillary for the direct extraction and high-performance liquid chromatographic determination of drugs in human serum

A restricted access material (RAM), alkyl-diol-silica (ADS), was used to prepare a highly bio-compatible solid-phase microextraction (SPME) capillary for the automated and direct in-tube extraction of several benzodiazepines from human serum. The bifunctionality of the ADS extraction phase prevented fouling of the capillary by protein adsorption while simultaneously trapping the analytes in the hydrophobic porous interior. This the first report of a restricted access material utilized as an extraction phase for in-tube SPME. The approach simplified the required apparatus in comparison to existing RAM column switching procedures, and more importantly eliminated the excessive use of extraction solvents. The biocompatibility of the ADS material also overcame the existing problems with in-tube SPME that requires an ultrafiltration or other deproteinization step prior to handling biological samples, therefore further minimizing the sample preparation requirements. The calculated oxazepam, temazepam, nordazepam and diazepam detection limits were 26, 29, 22 and 24 ng/ml in serum, respectively. The method was linear over the range of 50-50 000 ng/ml with an average linear coefficient (R2) value of 0.9998. The injection repeatability and intra-assay precision of the method were evaluated with five injections of a 10-microg/ml serum sample (spiked with all compounds), resulting in an average RSD<7%. The ADS extraction column was robust, providing many direct injections of biological fluids for the extraction and subsequent determination of benzodiazepines.

Determination of delorazepam in urine by solid-phase microextraction coupled to high performance liquid chromatography

An SPME-HPLC-UV method for the determination of delorazepam, a representative benzodiazepine, in spiked human urine samples was developed for the first time. The performances of two commercially available fibers, a carbowax/templated resin (Carbowax/TPR-100) and a polydimethylsiloxane/divinylbenzene (PDMS/DVB), were compared, indicating the latter as the most suitable for urine samples analysis. All the aspects influencing adsorption (extraction time, pH, temperature, salt addition) and desorption (desorption and injection time, desorption solvent mixture composition) of the analyte on the fiber have been investigated. In particular, short extraction times were necessary to reach the equilibrium and very short desorption times were employed. The procedure required simple sample pre-treatment and was able to detect 5 ng/ml in spiked urine, regardless of the complexity of the matrix.

Supercritical fluid extraction of steroids from biological samples and first experience with solid-phase microextraction-liquid chromatography

Modern extraction techniques, supercritical fluid extraction (SFE) and solid-phase microextraction (SPME) were used for isolation of four corticosteroids from biological matrices. SFE was applied for extraction from solid matrices--hydromatrix and pig muscle. The effects of various extraction conditions were studied. Good recoveries of corticosteroids from hydromatrix were obtained under moderate extraction conditions and without modification of carbon dioxide. On the contrary, the best recoveries from spiked pig muscle were obtained with modified carbon dioxide. SPME was used for extraction from liquid samples--water and urine. The eventuality of the use of this fast solvent-free technique in steroid analysis is demonstrated. Several extraction conditions were optimized. Extracted steroids were analyzed by HPLC-UV and a special SPME-HPLC interface was used for combination with SPME.

Direct determination of benzodiazepines in biological fluids by restricted-access solid-phase microextraction

A biocompatible solid-phase microextraction (SPME) fiber was prepared using an alkyl-diol-silica (ADS) restricted-access material as the SPME coating. The ADS-SPME fiber was able to simultaneously fractionate the protein component from a biological sample, while directly extracting several benzodiazepines, overcoming the present disadvantages of direct sampling in biological matrixes by SPME. The fiber was interfaced with an HPLC-UV system, and an isocratic mobile phase was used to desorb, separate, and quantify the extracted compounds. The calculated clonazepam, oxazepam, temazepam, nordazepam, and diazepam detection limits were 600, 750, 333, 100, and 46 ng/mL in urine, respectively. The method was confirmed to be linear over the range of 500-50000 ng/mL with an average linear coefficient (R2) value of 0.9918. The injection repeatability and intraassay precision of the method were evaluated over 10 injections, resulting in a RSD of approximately 6%. The ADS-SPME fiber was robust and simple to use, providing many direct extractions and subsequent determination of benzodiazepines in biological fluids.

Analysis of certain tranquilizers in biological fluids

A review with 282 references is presented that deals with the reported methods of analysis of phenothiazines, thioxanthenes, and benzodiazepine derivatives of pharmaceutical interest. The review includes the methods adapted in biological fluids.

Direct LC analysis of five benzodiazepines in human urine and plasma using an ADS restricted access extraction column

An alkyl-diol-silica (ADS) precolumn was used for the direct and on-line extraction of several benzodiazepines from serum and urine. The protein component of the biological sample was flushed through the ADS column, while simultaneously extracting the benzodiazepine compounds in the pores of the ADS stationary phase. The role of hydrophobic interactions in the extraction mechanism was confirmed. Column switching was employed to elute the extracted analytes from the ADS column into a high-performance liquid chromatography reverse-phase C18 column for the isocratic separation and UV detection of the benzodiazepines. Sample preconcentration via large volume injections was possible, improving the limits of detection. The calculated clonazepam, oxazepam, temazepam, nordazepam and diazepam detection limits were 38.8, 24.2, 31.7, 31.3, 45.0 ng/ml in serum, respectively, and 48.4, 24.5, 31.7, 33.1, 52.9 ng/ml for urine, respectively. The method was linear over the range of 50-10000 ng/ml in both matrices with an average linear coefficient (R(2)) value of 0.9918. The injection repeatability and intra-assay precision of the method were evaluated over ten injections, resulting in a percent relative standard deviation <5%. The ADS extraction column was robust, providing many direct injections of biological fluids for the extraction and subsequent determination of benzodiazepines.

Sample preparation with fiber-in-tube solid-phase microextraction for capillary electrophoretic separation of tricyclic antidepressant drugs in human urine

Solid-phase microextraction (SPME) is a solvent-free sample preparation technique using a thin coating attached to the surface of a fused silica-fiber as the extraction medium, which has been successfully applied to the analysis of a wide variety of compounds by coupling to gas chromatography (GC). In recent years, in-tube SPME using GC capillary column as the extraction medium has also been developed and coupled with liquid chromatography (LC) for the preconcentration of nonvolatile compounds. In this study, an on-line interface between the fiber-in-tube SPME and capillary electrophoresis (CE) has been developed, and the preconcentration and separation of four tricyclic antidepressant (TCA) drugs, amitriptyline, imipramine, nortriptyline, and desipramine, were performed with the hyphenated system. Under the optimized condition, a better extraction performance than conventional in-tube SPME was obtained, even the length of the extraction medium was much shorter. The results clearly indicated that the fiber was working effectively as an extraction medium. For the separation of these four TCAs, capillary electrophoretic separation with beta-cyclodextrin as the buffer additive has been employed and the application of the developed system to the analysis of complex sample mixtures in a biological matrix is also demonstrated.

Identification of a pharmaceutical packaging off-odor using solid phase microextraction gas chromatography/mass spectrometry

The use of a solid phase microextraction (SPME) sampling technique, in conjunction with gas chromatography/mass spectrometry (GC/MS) analysis, to identify an off-odor in a heat-stressed pharmaceutical packaging material is described. The ability of the commercially available polydimethylsiloxane (PDMS) coated microfiber to concentrate a trace volatile compound of interest enabled identification of the odor compound of interest. Despite being present at levels that defied detection using conventional headspace sampling techniques, ethyl-2-mercaptoacetate was determined to be the compound responsible for the offending odor. Formation of the thioester resulted from an unanticipated reaction (either esterification or transesterification) between a common residual solvent (ethanol), present in a commonly used pharmaceutical tablet dispersant, and low-level amounts of reactants or synthetic intermediates of an FDA-approved polyvinyl chloride (PVC)-resin thermal stabilizing agent.