An improved hollow fiber solvent-stir bar microextraction for the preconcentration of anabolic steroids in biological matrix with determination by gas chromatography–mass spectrometry

Determination of steroid profile in hair by liquid chromatography tandem mass spectrometry

The simultaneous determination of a large number of steroids (a.k.a. steroid profile) is a powerful tool that provides useful information about the status of steroid hormones. Steroid profile evaluated in matrices such as urine, saliva and plasma provide one-off moment information about the hormonal status and is highly affected by different factors such as circadian rhythm or apprehension to needles. In contrast, the determination of the steroid profile in hair would provide information about the chronic status of the steroid hormones. The objective of the current research was to develop and validate a liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodology for the determination of 11 steroids in hair, including 6 hormones and 5 metabolites. We have optimized different parts of the analytical procedure such as (i) hair shredding, (ii) hair amount, (iii) extraction from hair, (iv) extraction time, (v) required extractions and (vi) analytes preconcentration. MS parameters such as the inclusion of ESI- transitions were also evaluated. The optimization of these parameters was found to be critical to achieve the required sensitivity for the determination of steroids in hair. The method was validated with appropriate linearity in the endogenous range, intra- and inter-assay accuracies and matrix effect between 80% and 120% and intra- and inter-assay precisions below 20% for all analytes. Most of the analytes showed to be stable up to 10 months at room temperature. The suitability of the method was evaluated by obtaining the endogenous concentration range of steroids in 30 healthy volunteers. Results agreed with the scarce data previously reported for some steroids. For others, endogenous concentration ranges in hair were reported for the first time. Additionally, the method was used to compare intraindividual levels of steroids in beard and hair. Results revealed that with the exception of testosterone, beard is a suitable alternative to the hair determination of the steroid profile. In summary, the present strategy to evaluate the steroid profile in hair may be a useful tool with a high potential for a wide range of clinical purposes.

Hollow fiber liquid-phase microextraction based on the use of a rotating extraction cell: A green approach for trace determination of rhodamine 6G and methylene blue dyes

In this work, a novel mode of hollow fiber liquid-phase microextraction (HF-LPME) technique namely rotating extraction cell solvent bar microextraction (REC-SBME) was introduced. The proposed method was applied for the preconcentration of methylene blue (MB) and rhodamine 6G (RG) in some real samples, including soft drink, lipstick, environmental water, and wastewater samples. In the extraction setup, two pieces of hollow fibers were fixed on a mechanical support and immersed in a rotating extraction cell containing the sample solution during the extraction process. The rotation of the extraction cell by using an electric motor led to an enhancement in the mass transfer of the dyes from the sample solution into the organic acceptor phase. In the developed procedure, the UV-Vis spectrophotometry and HPLC-UV/Vis were employed as detection methods for the analysis of the acceptor phase and the obtained results were compared. Optimization of the extraction factors affecting the method, including organic solvent type, sample solution pH, extraction time, rotational rate, the volume of sample and acceptor solutions, salt addition, and temperature was performed in order to obtain the best preconcentration factor. Linear dynamic range obtained by HPLC-UV/Vis and spectrophotometry was observed in the ranges of 2.5-1200 ng mL^-1 for RG and 1.6-600 ng mL^-1 for MB with R² more than 0.9971. Also, relative standard deviation (RSD) values (n = 3) less than 3.8% were obtained. The good conformity of the obtained results makes UV-Vis spectrophotometric method an ideal tool for routine analysis of trace dyes in the complex matrices after REC-SBME.

Solvent stir bar microextraction technique with three-hollow fiber configuration for trace determination of nitrite in river water samples

In this work, trace determination of nitrite in river water samples was studied using solvent stir bar microextraction system with three-hollow fiber configuration (3HF-SSBME) as a preconcentration step prior to UV-Vis spectrophotometry. The obtained results showed that the increase in the number of solvent bars can improve the extraction performance by increasing the contact area between acceptor and sample solutions. The extraction process relies on the well-known oxidation-reduction reaction of nitrite with iodide excess in acidic donor phase to form triiodide, and then its extraction into organic acceptor phase using a cationic surfactant. Various extraction parameters affecting the method were optimized and examined in detail. Detection limit of 1.6 μg L^-1 and preconcentration factor of 282 can be attained after an extraction time of 8 min under the optimum conditions of this technique. The proposed method showed a linear response up to 1000 μg L^-1 (r² = 0.996) with relative standard deviation values less than 4.0%. The accuracy of the developed method was assessed using the Griess technique. Finally, the proposed method was successfully employed for quantification of nitrite in river water samples (Ghezelozan, Zanjan, Iran).

Opportunities for green microextractions in comprehensive two-dimensional gas chromatography / mass spectrometry-based metabolomics - A review

Microextractions have become an attractive class of techniques for metabolomics. The most popular technique is solid-phase microextraction that revolutionized the field of modern sample preparation in the early nineties. Ever since this milestone, microextractions have taken on many principles and formats comprising droplets, fibers, membranes, needles, and blades. Sampling devices may be customized to impart exhaustive or equilibrium-based characteristics to the extraction method. Equilibrium-based approaches may rely on additional methods for calibration, such as diffusion-based or on-fiber kinetic calibration to improve bioanalysis. In addition, microextraction-based methods may enable minimally invasive sampling protocols and measure the average free concentration of analytes in heterogeneous multiphasic biological systems. On-fiber derivatization has evidenced new opportunities for targeted and untargeted analysis in metabolomics. All these advantages have highlighted the potential of microextraction techniques for in vivo and on-site sampling and sample preparation, while many opportunities are still available for laboratory protocols. In this review, we outline and discuss some of the most recent applications using microextractions techniques for comprehensive two-dimensional gas chromatography-based metabolomics, including potential research opportunities.

Hollow fiber-stir bar sorptive extraction and microwave assisted derivatization of amino acids in biological matrices

A kind of solid phase microextraction configuration combining the principles of hollow fiber solid phase microextraction (HF-SPME) and stir bar sorptive extraction (SBSE) is presented. The main feature of HF-SBSE is the use of microporous hollow fiber acting as the carrier and filter, while a thin stainless steel wire and silica microspheres in the lumen of hollow fiber respectively acting as the magnetic stirrer and the dispersed sorbents for the collection and extraction of the target analytes, thus affording extraction process like SBSE. Moreover, the prepared hollow fiber stir bar was applied to direct microextraction and microwave assisted derivatization with N,O-Bis(trimethylsilyl)trifluroacetamide (BSTFA) of four amino acids in rats' urine and cerebrospinal fluid followed by gas chromatography mass spectrometric analysis. The limits of detection for four amino acids were found to be in the range of 0.0003-0.017μgmL^-1, and all the analytes did not exhibit any lack of fit. The extraction recoveries using HF-SBSE techniques ranged from 71.8% to 102.3%. The results indicated that hollow fiber stir bar sorptive extraction was a promising technique for the enrichment and direct derivatization of analytes extracted from biological matrices without sample clean-up.

Development of the fast, simple and fully validated high performance liquid chromatographic method with diode array detector for quantification of testosterone esters in an oil-based injectable dosage form

Counterfeit steroids are available on the black market, ultimately to consumers who believe they are buying a legitimate pharmaceutical item from the labeled company. In many cases, counterfeit steroids can contain lower doses or some products can be overdosed. This can unwittingly expose users to a significant health risks. The mixture of testosterone propionate, phenylpropionate, isocaproate and decanoate in an oil-based injectable dosage form belongs to the one of the most misused illicit drugs by a variety of athletes. This study developed a new, fast, simple and reliable HPLC method combined with a simple sample preparation step to determine testosterone propionate, phenylpropionate, isocaproate and decanoate in an oil-based injectable dosage form without the use of sophisticated and expensive instrumentation. The developed analytical procedure provides high throughput of samples where LC analysis takes only 6min and sample preparation of oil matrix in one step takes approximately 10min with precision ranging from 1.03 to 3.38% (RSD), and accuracy (relative error %) within ±2.01%. This method was found to be precise, linear, accurate, sensitive, selective and robust for routine application in screening of commercial pharmaceutical products based on content of mentioned testosterone esters in their oil-based injectable dosage form for counterfeit drugs. This method was successfully applied to the analysis of nine samples of commercial testosterone mixtures purchased from various sources and will be further used as an effective screening method for determination of previously mentioned testosterone esters in samples confiscated by Institute of Forensic Science (Slovakia) during the illegal trade.

Development of a new version of homogenous liquid–liquid extraction based on an acid–base reaction: application for extraction and preconcentration of aryloxyphenoxy-propionate pesticides from fruit juice and vegetable samples

In this paper, a new version of HLLE based on an acid–base reaction combined with DLLME followed by GC-FID has been developed for the extraction and determination of aryloxyphenoxy-propionate pesticides in fruit juice and vegetable samples.

Deltamethrin Binding to Triatoma infestans (Hemiptera: Reduviidae) Lipoproteins. Analysis by Solvent Bar Microextraction Coupled to Gas Chromatography

The binding of deltamethrin (DLM) to the hemipteran Triatoma infestans (Klug) hemolymph lipoproteins was evaluated in vitro. After DLM incubation with the insect hemolymph, lipoproteins were fractioned by ultracentrifugation. DLM binding was analyzed by a microextractive technique-solvent bar microextraction-a solventless methodology to extract DLM from each lipoprotein fraction. This is a novel use of the technique applied to extract an insecticide from an insect fluid. Capillary gas chromatography with microelectron capture detection was used to detect DLM bound by the T. infestans hemolymph lipoproteins and to identify the preferred DLM carrier. We show that Lp and VHDLp I lipoproteins are mainly responsible for DLM transport in T. infestans, both in DLM-resistant and DLM-susceptible bugs. Our results also indicate that DLM amounts transported are not related to DLM susceptibility.

Sensitive, fast, and specific immunoassays for methyltestosterone detection

An indirect competitive enzyme-linked immunosorbent assay (icELISA) and an immunochromatographic strip assay using a highly specific monoclonal antibody, were developed to detect methyltestosterone (MT) residues in animal feed. The optimized icELISA had a half-inhibition concentration value of 0.26 ng/mL and a limit of detection value of 0.045 ng/mL. There was no cross-reactivity with eight analogues, revealing high specificity for MT. Based on icELISA results, the recovery rate of MT in animal feed was 82.4%–100.6%. The results were in accordance with those obtained by gas chromatography-mass spectrometry. The developed immunochromatographic strip assay, as the first report for MT detection, had a visual cut-off value of 1 ng/mL in PBS, 2.5 ng/g in fish feed, and 2.5 ng/g in pig feed. Therefore, these immunoassays are useful and fast tools for MT residue detection in animal feed.

Microextraction in urine samples for gas chromatography: a review

Since the complexity origin of biological samples, the research trends have been directed to the development of new miniaturized sample preparation techniques. This review provides a comprehensive survey of past and present microextraction methods followed by GC analysis for preconcentration and determination of various analytes in urine samples. These techniques have been classified in three general groups, including liquid-, solid- and membrane-based techniques. The principal of different microextraction methods that are located in each general group as well as their various extraction modes and the recent developments introduced for them has been presented. Subsequently, a comparison survey has been carried out among different microextraction techniques and finally a future perspective has been predicted based on the existing literature.

Simultaneous determination of imperatorin and its metabolite xanthotoxol in rat plasma by using HPLC-ESI-MS coupled with hollow fiber liquid phase microextraction

The objective of the present study was to develop a new method for the simultaneous quantitation of imperatorin and its metabolite xanthotoxol in rat plasma. The samples were prepared with hollow fiber liquid phase microextraction (HF-LPME). The optimized extraction procedure was acquired by assessing extraction solvent, length of the fiber, agitation rate, extraction temperature and time. A comparison of sample pretreatment ways between HF-LPME and deproteinization with methanol was performed, which demonstrated less ion suppression and better sensitivity of HF-LPME. Analytes were separated on a C18 column with a gradient elution consisted of methanol and water containing 1mmol/L ammonium acetate. The detection was accomplished by electrospray ionization (ESI) source operating in the positive ionization mode. Selected-multiple-reaction monitoring (SMRM) scanning was employed, which guaranteed a higher sensitivity compared with MRM mode. Calibration curves were linear over investigated ranges with correlation coefficients greater than 0.9979. Precision varied from 0.26% to 14%, and the accuracy varied within ±5.5%. The developed method was successfully applied to the pharmacokinetic research of imperatorin and its metabolite xanthotoxol after oral administration of imperatorin to rats.

Role of microextraction sampling procedures in forensic toxicology

The last two decades have provided analysts with more sensitive technology, enabling scientists from all analytical fields to see what they were not able to see just a few years ago. This increased sensitivity has allowed drug detection at very low concentrations and testing in unconventional samples (e.g., hair, oral fluid and sweat), where despite having low analyte concentrations has also led to a reduction in sample size. Along with this reduction, and as a result of the use of excessive amounts of potentially toxic organic solvents (with the subsequent environmental pollution and costs associated with their proper disposal), there has been a growing tendency to use miniaturized sampling techniques. Those sampling procedures allow reducing organic solvent consumption to a minimum and at the same time provide a rapid, simple and cost-effective approach. In addition, it is possible to get at least some degree of automation when using these techniques, which will enhance sample throughput. Those miniaturized sample preparation techniques may be roughly categorized in solid-phase and liquid-phase microextraction, depending on the nature of the analyte. This paper reviews recently published literature on the use of microextraction sampling procedures, with a special focus on the field of forensic toxicology.