Capillary zone electrophoresis with diode-array detection for analysis of local anaesthetics and opium alkaloids in urine samples

Determination of Local Anesthetic Drugs in Human Plasma Using Magnetic Solid-Phase Extraction Coupled with High-Performance Liquid Chromatography

In this work, magnetic tetraethylenepentamine (TEPA)-modified carboxyl–carbon nanotubes were synthesized, characterized, and used as adsorbents to conduct magnetic solid-phase extraction (MSPE) for the preconcentration of seven local anesthetic drugs (procaine, lidocaine, mepivacaine, oxybuprocaine, bupivacaine, tetracaine, and cinchocaine) from human plasma. The separation and determination of analytes were performed on high-performance liquid chromatography with UV detection. Several factors affected the extraction efficiency, such as the amount of adsorbents used, extraction time, sample pH, and optimization of elution conditions. Under optimal conditions, satisfactory linear relationships were obtained in the range of 0.02–5.00 mg/L, with the limits of detection (LOD) ranging from 0.003 mg/L to 0.008 mg/L. The recoveries of analytes for spiked human plasma were in the range of 82.0–108%. Moreover, the precision with intra-day and inter-day RSD values were obtained in the range of 1.5–7.7% and 1.5–8.3%. The results indicated that this method could determine the concentration of seven local anesthetic drugs in human plasma with high precision and repeatability and provide support for the clinical monitoring of the concentration of local anesthetic drugs in human plasma.

A membrane-protected microsolid phase-extraction method based on molecular imprinting and its application to the determination of local anesthetics in cosmetics

As local anesthetics (LAs) that are illegally added into cosmetics are harmful to consumer health, it is necessary to establish an efficient method for detecting these substances. Herein, a molecularly imprinted polymer (bupivacaine) was prepared by bulk polymerization and packed into a hollow fiber for use as an extraction phase to fabricate a membrane-protected microsolid phase-extraction device. The optimal values of the influencing parameters for the microextraction process were as follows: a sample solution pH of 9.0, a loading and washing time of 2 h and an elution time of 32 min. A GC-MS method was established for determination of local anesthetics and coupled with the microextraction method to successfully detect local anesthetics in cosmetic samples. The calibration curve for the proposed method was linear in the range of 0.4∼50 mg/L and showed a good correlation coefficient (r² ). The LODs for local anesthetics were in the range of 0.01∼0.71 mg/L. The molecularly imprinted polymer exhibited good imprinting and selectivity, and the microsolid phase-extraction device was simple and inexpensive and fabrication was reproducible. The combination of molecular imprinting technology, membrane separation and microsolid phase-extraction methods used in this study can potentially be applied to pretreat local anesthetics in cosmetic samples. This article is protected by copyright. All rights reserved.

Development of electrically assisted solvent bar microextraction followed by high performance liquid chromatography for the extraction and quantification of basic drugs in biological samples

In this study, a new extraction procedure is introduced based on electrically assisted solvent bar microextraction. In the first step, the analytes are transferred from sample solution to the hollow fiber supported organic solvent. After that, with the aid of an electrical field, the analytes migrated into the aqueous extractant. The proposed approach was used to extract the three basic drugs (including lidocaine, diltiazem, and propranolol) from the plasma and urine samples. Under the optimized condition, (the supported organic solvent: 1-octanol, stirring rate: 300 rpm, pH of sample solution: 12.0, salt concentration: 2.0% (w/v), extraction time: 15 min, aqueous extractant: (30 µL, 100 mM HCl), back-extraction time: 2 min, back-extraction voltage: 100 V), the proposed procedure presented wide linearities with coefficients of determination more than 0.992 over a concentration range of 5.0-1000 ng mL^-1. The limit of detection was also determined in the range of 0.5 to 5.0 ng mL^-1, repeatability (intra-day) was between 3.3 and 11.1% (n = 4), and reproducibility (inter-day) was between 4.3 and 14.6% (n = 4 days). It was indicated that the proposed approach could effectively extract the analytes from the plasma and urine samples, and the relative recoveries were between 90.2 and 105.6%, indicating the validity of this method.

Determination of bupivacaine tissue concentration in human biopsy samples using high-performance liquid chromatography with mass spectrometry

In the present study, we developed a simple and rapid analytical method for the quantification of bupivacaine hydrochloride in human biopsy samples of adipose, muscle, neural, connective and cartilage tissue using liquid chromatography-mass spectrometry. Anesthetics were extracted from the tissue samples using 0.1% formic acid in acetonitrile for protein denaturation and hexane for removal of lipophilic impurities. Analytes were separated adequately on Phenomenex Luna Omega polar C18 column using a gradient mobile phase 0.1% formic acid in water and 0.1% formic acid in acetonitrile. The lower limits of quantification were ≤ 97 ng g^-1 tissue for all studied tissues. Intra-day recoveries were between 48.2% and 82.1% with relative standard deviations (RSDs) between 1.47% and 14.28%, whereas inter-day recoveries were between 52.2% and 77.6% with RSDs between 2.98% and 14.79%. The calibration curve showed a linear fit with R² higher than 0.99 in the concentration range from 0.16 to 100 μg g^-1 . Lidocaine hydrochloride was tested as internal standard because its recoveries and matrix effects were comparable to bupivacaine hydrochloride. Post-analytical corrections of measured bupivacaine tissue concentrations can accordingly be made based on recovery of lidocaine as internal standard, with recoveries between 51.2% and 86.9% and RSDs between 1.99% and 16.88%. The developed method could be used to study time-dependent spread of bupivacaine locally or to more distant locations across tissue barriers.

Coupling of micro-solid-phase extraction and internal extractive electrospray ionization mass spectrometry for ultra-sensitive detection of 1-hydroxypyrene and papaverine in human urine samples

Quantification of ultra-trace analytes in complex biological samples using micro-solid-phase extraction followed by direct detection with internal extractive electrospray ionization mass spectrometry (μSPE-iEESI-MS) was demonstrated. 1-Hydroxypyrene (1-OHP) and papaverine at attomole levels in human raw urine samples were analyzed under negative and positive ion detection mode, respectively. The μSPE was simply prepared by packing a disposable syringe filter with octadecyl carbon chain (C18)-bonded micro silica particles, which were then treated as the "bulk sample" after the analytes were efficiently enriched by the C18 particles. Under the optimized experimental conditions, the analytes were readily eluted by isopropanol/water (80/20, V/V) at a high voltage of ± 4.0 kV, producing analyte ions under ambient conditions. The limit of detection (LOD) was 0.02 pg/L (9.2 amol) for 1-hydroxypyrene and 0.02 pg/L (5.9 amol) for papaverine. The acceptable linearity (R² > 0.99), signal stability (RSD ≤ 10.7%), spike recoveries (91-95%), and comparable results for real urine samples were also achieved, opening up possibilities for quantitative analysis of trace compounds (at attomole levels) in complex bio-samples. Graphical abstract.

Application of polyacrylamide gel as a new membrane in electromembrane extraction for the quantification of basic drugs in breast milk and wastewater samples

Introducing new membranes with green chemistry approach seems to be a great challenge for the development of a practical method in separation science. In this regard, for the first time, polyacrylamide gel as a new membrane in electromembrane extraction (EME) was used for the extraction of three model basic drugs (pseudoephedrine (PSE), lidocaine (LID), and propranolol (PRO)), followed by HPLC-UV. In comparison with conventional EME, in this method neither organic solvent nor carrier agents were used for extraction of mentioned drugs. Different variables for fabrication of polyacrylamide gel and extraction process were evaluated. Polyacrylamide gel (containing 12% (w/v) acrylamide, and 3.0% (w/w) bisacrylamide) with 2 mm thickness at pH = 1.5 was fabricated as membrane. The drugs were extracted from aqueous samples, through a polyacrylamide gel membrane, to an aqueous acceptor phase on membrane. Under the optimized extraction conditions (Voltage: 85 V, extraction time: 28 min, acceptor phase's pH: 4.0, and donor phase's pH: 7.0) limits of quantification and detection were in the ranges of 1.0-20.0 ng mL^-1 and 0.3-6.0 ng mL^-1, respectively. Applying the proposed method to determine and quantify intended drugs in breast milk, and wastewater samples have revealed acceptable results.

Quantification of bupivacaine hydrochloride and isoflupredone acetate residues in porcine muscle, beef, milk, egg, shrimp, flatfish, and eel using a simplified extraction method coupled with liquid chromatography-triple quadrupole tandem mass spectrometry

In this study, a simple analytical approach has been developed and validated for the determination of bupivacaine hydrochloride and isoflupredone acetate residues in porcine muscle, beef, milk, egg, shrimp, flatfish, and eel using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A 0.1% solution of acetic acid in acetonitrile combined with n-hexane was used for deproteinization and defatting of all tested matrices and the target drugs were well separated on a Waters Xbridge™ C18 analytical column using a mobile phase consisting of 0.1% acetic acid (A) and 0.1% solution of acetic acid in methanol (B). The linearity estimated from six-point matrix-matched calibrations was good, with coefficients of determination ≥0.9873. The limits of quantification (LOQs) for bupivacaine hydrochloride and isoflupredone acetate were 1 and 2ngg^-1, respectively. Recovery percentages in the ranges of 72.51-112.39% (bupivacaine hydrochloride) and 72.58-114.56% (isoflupredone acetate) were obtained from three different fortification concentrations with relative standard deviations (RSDs) of <15.14%. All samples for the experimental work and method application were collected from the local markets in Seoul, Republic of Korea, and none of them tested positive for the target drugs. In conclusion, a simple method using a 0.1% solution of acetic acid in acetonitrile and n-hexane followed by LC-MS/MS could effectively extract bupivacaine hydrochloride and isoflupredone acetate from porcine muscle, beef, milk, egg, shrimp, flatfish, and eel samples.

Resonance Rayleigh scattering technique as a detection method for the RP-HPLC determination of local anaesthetics in human urine

A highly selective and sensitive method of reversed phase high-performance liquid chromatography (RP-HPLC) coupled with resonance Rayleigh scattering (RRS) was developed for the determination of procaine, bupivacaine and tetracaine. Separation of three local anaesthetics was achieved at 35 °C on a C₁₈ column. The mobile phase was 30: 70 (v/v) acetonitrile/triethylamine-phosphoric acid buffer (pH 2.9) at flow rate of 0.3 mL/min. The RRS detection was conducted by taking advantage of the strong RRS enhancement of the local anaesthetics with erythrosine reaction in an acidic medium. Under optimum conditions, the limit of detection (S/N = 3) values were in the range of 2.4-11.2 ng/mL. Recoveries from spiked human urine samples were 95.8%-104.5%. The proposed method applied to the determination of local anaesthetics in human urine achieved satisfactory results. In addition, the mechanism of the reaction is fully discussed. Copyright © 2016 John Wiley & Sons, Ltd.

Chromatographic Determination of Aminoacridine Hydrochloride, Lidocaine Hydrochloride and Lidocaine Toxic Impurity in Oral Gel

Two sensitive and selective analytical methods were developed for simultaneous determination of aminoacridine hydrochloride and lidocaine hydrochloride in bulk powder and pharmaceutical formulation. Method A was based on HPLC separation of the cited drugs with determination of the toxic lidocaine-related impurity 2,6-dimethylaniline. The separation was achieved using reversed-phase column C18, 250 × 4.6 mm, 5 µm particle size and mobile phase consisting of 0.05 M disodium hydrogen phosphate dihydrate (pH 6.0 ± 0.2 adjusted with phosphoric acid) and acetonitrile (55 : 45, v/v). Quantitation was achieved with UV detection at 240 nm. Linear calibration curve was in the range of 1.00-10.00, 13.20-132.00 and 1.32-13.20 µg mL(-1) for aminoacridine hydrochloride, lidocaine hydrochloride and 2,6-dimethylaniline, respectively. Method B was based on TLC separation of the cited drugs followed by densitometric measurement at 365 nm on the fluorescent mode for aminoacridine hydrochloride and 220 nm on the absorption mode for lidocaine hydrochloride. The separation was carried out using ethyl acetate-methanol-acetic acid (65 : 30 : 5 by volume) as a developing system. The calibration curve was in the range of 25.00-250.00 ng spot(-1) and 0.99-9.90 µg spot(-1) for aminoacridine hydrochloride and lidocaine hydrochloride, respectively. The results obtained were statistically analyzed and compared with those obtained by applying the manufacturer's method.

Recent advances in enrichment techniques for trace analysis in capillary electrophoresis

CE is gaining great popularity as a well-established separation technique for many fields such as pharmaceutical research, clinical application, environmental monitoring, and food analysis, owing to its high resolving power, rapidity, and small amount of samples and reagents required. However, the sensitivity in CE analysis is still considered as being inferior to that in HPLC analysis. Diverse enrichment methods and techniques have been increasingly developed for overcoming this issue. In this review, we summarize the recent advances in enrichment techniques containing off-line preconcentration (sample preparation) and on-line concentration (sample stacking) to enhancing sensitivity in CE for trace analysis over the last 5 years. Some relatively new cleanup and preconcentration methods involving the use of dispersive liquid-liquid microextraction, supercritical fluid extraction, matrix solid-phase dispersion, etc., and the continued use and improvement of conventional SPE, have been comprehensively reviewed and proved effective preconcentration alternatives for liquid, semisolid, and solid samples. As for CE on-line stacking, we give an overview of field amplication, sweeping, pH regulation, and transient isotachophoresis, and the coupling of multiple modes. Moreover, some limitations and comparisons related to such methods/techniques are also discussed. Finally, the combined use of various enrichment techniques and some significant attempts are proposed to further promote analytical merits in CE.