Development of a method for the determination of sedatives in bovine and porcine urine and kidneys by liquid chromatography-tandem mass spectrometry

Introduction

Sedatives have been used for a long time as animal tranquillisers to prevent stress and weight loss during their transportation. The proper determination of these substances in food of animal origin is essential for consumer safety.

Material and Methods

A 1 g portion of pig or cow urine or homogenised kidney was mixed with acetonitrile, sodium chloride was added, and the solution was further mixed and then centrifuged. The supernatant was transferred to a new centrifuge tube with primary and secondary amine, octadecylsilane and ZrO2, and mixed rapidly. The filtered solution was evaporated under a nitrogen stream. The residue was dissolved in 200 μL of acetonitrile, centrifuged with filters and then transferred to vials. Samples were analysed by high-performance liquid chromatography-tandem mass spectrometry.

Results

The decision limit for confirmation was calculated at 2.5 μg kg-1 for all sedatives with relative standard deviation repeatability and reproducibility below 20%.

Conclusion

The validation results showed that this method meets the pertinent EU criteria for such methods and is suitable for sedative analysis in urine and kidney matrices.

Ultrasound-assisted electromembrane extraction with supported semi-liquid membrane

Electromembrane extraction (EME), involving the migration of charged analytes across a supported liquid membrane (SLM) with an external power supply, is a promising sample preparation method in analytical chemistry. However, the presence of boundary double layers at the SLM/solution interfaces often restricts extraction efficiency. To avoid this, the current work proposed an ultrasound-assisted EME (UA-EME) method based on a novel type of supported semi-liquid membrane (SsLM). The characterizations showed that the SsLM was stable under ultrasound conditions. Ultrasound was found to reduce the boundary double layers and thus increase the mass transfer. Major operational parameters in UA-EME including ultrasound power density, temperature, applied voltage and extraction time were optimized with haloperidol, fluoxetine, and sertraline as model analytes. Under the optimal conditions, extraction recoveries of model analytes in water samples were in the range of 66.8%-91.6%. When this UA-EME method was coupled with LC-MS/MS for detection of the target analytes in human urine samples, the linear range of the analytical method was 10-1000 ng mL^-1, with R² > 0.997 for all analytes. The limits of detection (LOD) and limits of quantification (LOQ) were in the range of 1.7-2.1 ng mL^-1 and 5.7-6.7 ng mL^-1, respectively. The UA-EME expands the application field of ultrasound chemistry and will be very important in development of stable and fast sample preparation systems in the future.

Development of Sensitive and High-Throughput Liquid Chromatography-Tandem Mass Spectrometry Method for Quantification of Haloperidol in Human Plasma with Phospholipid Removal Pretreatment

Haloperidol, butyrophenone derivative, is a typical antipsychotic drug used in the treatment of schizophrenia, manic phase of bipolar disorder, and acute psychomotor agitations. According to the recent guidelines for therapeutic drug monitoring, it is strongly recommended to measure plasma level during the therapy with haloperidol. The objective of this study was to develop and validate a simple liquid chromatography-tandem mass spectrometry-based method to quantitate haloperidol in human plasma. After one-step extraction procedure using OSTROTM plate, gradient elution on Acquity UPLC BEH C18 (50 ×2.1mm, 1.7μm) column over 3.2 min was performed. The detection was conducted on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring mode in positive ionization mode with transitions at m/z 376.29 → 165.14 and m/z 380.28 → 169.17 for haloperidol and haloperidol-d4 (used as an internal standard), respectively. The method was fully validated to cover wide concentration range of 0.05-80 ng/mL in human plasma and meets the criteria for the selectivity, linearity and lower limit of detection, precision and accuracy, matrix effect, extraction recovery, carryover, dilution integrity and stability. The extraction recovery was nearly 100%, and no significant matrix effects were observed. Therefore, the method is applicable to routine therapeutic drug monitoring in patients' plasma.

Highly sensitive and selective method for the rapid determination and preconcentration of haloperidol by using a magnetite-molecularly imprinted polymer

A sensitive and selective method based on the determination of haloperidol with the usage of magnetite-molecularly imprinted polymer and high-resolution liquid chromatography has been developed. This novel method is rapid as the detection procedure for haloperidol can be completed within a total time of 1 h. The same imprinted polymer can be used for the determination of haloperidol at least 20 times. The proposed method has been succesfully applied to synthetic urine and serum samples and the recoveries of the spiked samples were in the range of 94.7-100.7%. The limit of detection and limit of quantification of the method were 2.25 and 7.50 μg/L, respectively. Linearity of the calibration graph was observed within the range of 10-250 μg/L. By combining the high capacity, high selectivity, and reusability of the magnetic adsorbent with the dynamic calibration range, high sensitivity and high resolution of liquid chromatography with quadrupole time-of-flight mass spectrometry, the proposed method is an ideal method for the determination and preconcentration of trace levels of haloperidol. A magnetite-molecularly imprinted polymer has been used for the first time as a selective adsorbent for the determination of haloperidol.

Present state and applications of single drop microextraction for the determination of harmful organic compounds and pollutants

Single drop microextraction (SDME) nowadays earns an increasing attention by scientists due to its simplicity, low cost and the need for only common laboratory equipment. This microextraction technique combines sample cleanup and pre-concentration of analytes in one step. Furthermore, a significant reduction in the amount of organic solvents needed comparing to standard LLE techniques places SDME into the position of environmental friendly extraction techniques. SDME is a straightforward technique in which a micro-drop of solvent is suspended from the tip of a conventional micro-syringe and then it is in a direct contact with a sample solution in which it is immiscible or it could be suspended in the headspace above the sample. The paper overviews developments of the state-of-the-art SDME techniques for the extraction of harmful organic compound and pollutants from environmental, food and biological matrices. Key extraction parameters essential for SDME performance were described and discussed.

High-Throughput Determination of Octanol-Water Partition Coefficients by Ultrasound-Assisted Liquid-Phase Microextraction

A method of high-throughput determination, which is based on ultrasound-assisted liquid-phase microextraction, was developed to measure directly the partition coefficients of n-octanol-water. In ultrasound-assisted liquid-phase microextraction, ultrasonic energy can facilitate the mass transfer process of six or more microextractors simultaneously. Therefore, high-throughput determination of n-octanol-water partition coefficients can be performed favorably, and the equilibrium time of each microextractor can be decreased effectively. Several experimental parameters including ultrasonic power and frequency, centrifugation conditions, extractant volume and sample concentration were analyzed and optimized at 25°C. Under the optimum conditions, it only takes 2 min to reach extraction equilibrium, and the solutions of sample can be separated by centrifugation in 4 min. After centrifugation, the concentrations in n-octanol phases are analyzed with gas chromatography. The method was further evaluated with eight reference compounds and the findings demonstrated that this method is suitable to determine the partition coefficients of organic compounds accurately and quickly. Next, the method was exploited to measure the partition coefficients of n-octanol-water containing 20 organic compounds, which cover the [Formula: see text] values from 0.05 to 4.36, with comparatively low relative standard deviation (RSD) directly. The results of this study illustrated that the RSD (n = 6) was under 3%.

Multivariate optimization of surfactant-assisted directly suspended droplet microextraction combined with GC for the preconcentration and determination of tramadol in biological samples

In this work, a novel procedure based on surfactant-assisted directly suspended droplet microextraction for the determination of tramadol prior to GC with flame ionization detection is proposed. In this technique, a free microdroplet of solvent is transferred to the surface of an immiscible aqueous sample containing Triton X-100 and tramadol while being agitated by a stirring bar placed on the bottom of the sample vial. After the predetermined time, the microdroplet of solvent is withdrawn by a syringe and analyzed. The effective parameters such as the type of organic solvent, extraction time, microdroplet volume, salt content of the donor phase, stirring speed, the source phase pH, concentration of Triton X-100, and extraction temperature were optimized. For this purpose, a multivariate strategy was applied based on an experimental design in order to screen and optimize the significant factors. This method requires minimal sample preparation, analysis time, solvent consumption, and represents significant advantages over customary analytical methods. The linearity ranged from 10 to 2000 μg/L with RSDs (n = 5) of 7.3-10. Preconcentration factors and the LODs were 391-466 and 2.5-6.5 μg/L, respectively. Finally, this method was applied to the analysis of biological samples and satisfactory results were obtained.