Determination of some local anesthetics in human serum by gas chromatography with solid-phase extraction

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.

Voltammetry of local anesthetics: theoretical and practical aspects

Local anesthetics (LAs) are widely used in anesthesiology, ophthalmology, and otolaryngology as well as for treatment of chronic and oncological pain. However, anesthetics can cause adverse effects up to lethal ones. In this work, we cited reviews on chromatographic and spectroscopic methods of local anesthetics determination published earlier, and the main purpose was to review the possibilities and advantages of voltammetric methods used for the LAs determination. The electrochemical behavior, mechanism of LAs transformation on the various working electrodes and analytical parameters of voltammetric methods used for their determination were reviewed in the work. Vast majority of these methods were developed for the most widely used anesthetics in medicine like benzocaine, lidocaine and procaine. Special attention was paid to possible mechanisms of electrochemical oxidation and in some cases reduction of LAs or their derivatives. Voltammetry is used for the determination of LAs in pharmaceutical formulations and in biological fluids. The analytical characteristics in terms of sensitivity, selectivity, reproducibility also were discussed in the article.

Reduced graphene oxide as an efficient sorbent in microextraction by packed sorbent: Determination of local anesthetics in human plasma and saliva samples utilizing liquid chromatography-tandem mass spectrometry

Herein, reduced graphene oxide (RGO) has been utilized as an efficient sorbent in microextraction by packed sorbent (MEPS). The combination of MEPS and liquid chromatography-tandem mass spectrometry has been used to develop a method for the extraction and determination of three local anesthetics (i.e. lidocaine, prilocaine, and ropivacaine) in human plasma and saliva samples. The results showed that the utilization of RGO in MEPS could minimize the matrix effect so that no interfering peaks at the retention times of the analytes or internal standard was observed. The high extraction efficiency of this method was approved by mean recoveries of 97.26-106.83% and 95.21-105.83% for the studied analytes in plasma and saliva samples, respectively. Intra- and inter-day accuracies and precisions for all analytes were in good accordance with the international regulations. The accuracy values (as percentage deviation from the nominal value) of the quality control samples were between -2.1 to 13.9 for lidocaine, -4.2 to 11.0 for prilocaine and between -4.5 to -2.4 for ropivacaine in plasma samples while the values were ranged from -4.6 to 1.6 for lidocaine, from -4.2 to 15.5 for prilocaine and from -3.3 to -2.3 for ropivacaine in human saliva samples. Lower and upper limit of quantification (LLOQ, ULOQ) were set at 5 and 2000 nmol L^-1 for all of the studied drugs. The correlation coefficients values were ≥0.995. The limit of detection values were obtained 4 nmol L^-1 for lidocaine and prilocaine, and 2 nmol L^-1 for ropivacaine.

Enhanced HPLC-MS/MS method for the quantitative determination of the co-administered drugs ceftriaxone sodium and lidocaine hydrochloride in human plasma following an intramuscular injection and application to a pharmacokinetic study

A sensitive HPLC-MS/MS method was established for the quantification of ceftriaxone sodium (CFT) and lidocaine HCl (LDC) in human plasma utilizing cefixime (CFX) and tadalafil (TDA) as internal standards. The analytes were extracted from human plasma by protein precipitation using acetonitrile. Chromatographic separation was performed on Kinetex C₁₈ (50.0 × 4.6 mm, 5 μm particle size) column with methanol-0.01 M ammonium acetate pH 6.4 (70: 30, v/v) as mobile phase. Multiple reaction monitoring involving the transitions 555.10 → 396.20, 235.20 → 86.00, 454.20 → 284.80 and 390.20 → 268.20 was utilized to quantify CFT, LDC, CFX and TDA, respectively, using a triple quadrupole mass spectrometer which was operated in positive ion mode. The method revealed linearity in the concentration range of 3.0-300.0 μg/mL for CFT and 3.0-300.0 ng/mL for LDC. The validation of the method was achieved in accordance to the US Food and Drug Administration guidelines. A pharmacokinetic study was performed on healthy Egyptian volunteers after intramuscular injection of sterile ceftriaxone sodium (1 g CFT dissolved in 3.5 mL of 1% LDC) after approval from the ethics committee. The pharmacokinetic parameters were: C_max 141.15 ± 39.84 (μg/mL) and 55.02 ± 9.36 (ng/mL); t_max (h) 2.50 ± 0.50 and 1.5 ± 0.50; t_½ (h) 7.30 ± 2.98 and 4.23 ± 1.96; and K_el (h^-1 ) 0.10 ± 0.04 and 0.20 ± 0.13 for CFT and LDC, respectively.

Comparison of lidocaine metabolism for different anesthesia techniques in rabbits with liver disease

OBJECTIVE

This study was designed to investigate the serum lidocaine concentrations (SLC) after local infiltration anesthesia (IA) and mandibular anesthesias (MA) in rabbits with carbon tetrachloride (CCl₄)-induced chronic liver damage (CLD).

STUDY DESIGN

Fourteen rabbits were administered CCl₄ in group 1, MA (CLD-MA; n = 7); in group 2, IA (CLD-IA; n = 7); in group 3, MA (H-MA; n = 7); and in group 4, IA (H-IA; n = 6) was performed. SLC were measured.

RESULTS

SLC showed difference over time. At the 10th minute, mean SLC in IA groups were higher than in MA groups. At the 120th minute, the highest mean concentration was found in the CLD-IA group.

CONCLUSIONS

SLC increases in CLD, and serum lidocaine concentration after IA in the mandibular anterior region is higher than it is after MA.

Quantitative mass spectrometric analysis of ropivacaine and bupivacaine in authentic, pharmaceutical and spiked human plasma without chromatographic separation

The present study employs time of flight mass and bupivacaine in authentic, pharmaceutical and spiked human plasma as well as in the presence of their impurities 2,6-dimethylaniline and alkaline degradation product. The method is based on time of flight electron spray ionization mass spectrometry technique without preliminary chromatographic separation and makes use of bupivacaine as internal standard for ropivacaine, which is used as internal standard for bupivacaine. A linear relationship between drug concentrations and the peak intensity ratio of ions of the analyzed substances is established. The method is linear from 23.8 to 2380.0 ng mL(-1) for both drugs. The correlation coefficient was >or=0.996 in authentic and spiked human plasma. The average percentage recoveries in the ranges of 95.39%-102.75% was obtained. The method is accurate (% RE < 5%) and reproducible with intra- and inter-assay precision (RSD% < 8.0%). The quantification limit is 23.8 ng mL(-1) for both drugs. The method is not only highly sensitive and selective, but also simple and effective for determination or identification of both drugs in authentic and biological fluids. The method can be applied in purity testing, quality control and stability monitoring for the studied drugs.

Simultaneous determination of nikethamide and lidocaine in human blood and cerebrospinal fluid by high performance liquid chromatography

Nikethamide and lidocaine are often requested to be quantified simultaneously in forensic toxicological analysis. A simple reversed-phase high performance liquid chromatography (RP-HPLC) method has been developed for their simultaneous determination in human blood and cerebrospinal fluid. The method involves simple protein precipitation sample treatment followed by quantification of analytes using HPLC at 263 nm. Analytes were separated on a 5 microm Zorbax Dikema C18 column (150 mm x 4.60 mm, i.d.) with a mobile phase of 22:78 (v/v) mixture of methanol and a diethylamine-acetic acid buffer, pH 4.0. The mean recoveries were between 69.8 and 94.4% for nikethamide and between 78.9 and 97.2% for lidocaine. Limits of detection (LODs) for nikethamide and lidocaine were 0.008 and 0.16 microg/ml in plasma and 0.007 and 0.14 microg/ml in cerebrospinal fluid, respectively. The mean intra-assay and inter-assay coefficients of variation (CVs) for both analytes were less than 9.2 and 10.8%, respectively. The developed method was applied to blood sample analyses in eight forensic cases, where blood concentrations of lidocaine ranged from 0.68 to 34.4 microg/ml and nikethamide ranged from 1.25 to 106.8 microg/ml. In six cases cerebrospinal fluid analysis was requested. The values ranged from 20.3 to 185.6 microg/ml of lidocaine and 8.0 to 72.4 microg/ml of nikethamide. The method is simple and sensitive enough to be used in toxicological analysis for simultaneous determination of nikethamide and lidocaine in blood and cerebrospinal fluid.

Simultaneous determination of three local anesthetic drugs from the pipecoloxylidide group in human serum by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous analysis of the local anesthetic amide drugs, bupivacaine, mepivacaine and ropivacaine, belonging to the pipecoloxylidide group using a C(18) reversed-phase column (150 x 4.6 mm I.D.) filled with 5-microm particles and attached to a UV detector. The mobile phase was composed of acetonitrile-methanol-30 mM NaH(2)PO(4) (pH 5.6) (100:100:300, v/v/v) and the flow rate was 1ml/min. The absorbance of the eluate was monitored at 210 nm. The retention times of the three compounds were: 4.6 min (mepivacaine), 9.7min (ropivacaine) and 16.4 min (bupivacaine). With this sample preparation method, good and consistent recoveries of the three compounds were obtained: 88-91% for mepivacaine, 87-89% for ropivacaine and 88-91% for bupivacaine. The limit of quantification for three compounds in human serum was 2 ng/ml for mepivacaine, 5 ng/ml for bupivacaine and ropivacaine. This method may be useful in clinical and forensic applications for the determination or identification of the local anesthetic drugs: bupivacaine, mepivacaine or ropivacaine.

Liquid chromatography–electrospray mass spectrometry determination of free and total concentrations of ropivacaine in human plasma

A specific and sensitive liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method was developed for the determination of free and total ropivacaine in human plasma. The work-up procedure involved a simple precipitation of plasma proteins with methanol. Etidocaine served as the internal standard. After microscale equilibrium-dialysis, measurement of free ropivacaine levels was performed after direct injection of the dialysate into the chromatograph. The system used a Zorbax eclipse XD8 C8 analytical column packed with 5 microm diameter particles as the stationary phase. The mobile phase consisted of a 15-min gradient (mobile phase A: 0.05% (v/v) trimethylamine in acetonitrile, mobile phase B: 2mM ammonium formate buffer (pH 3)). Mass spectrometric data were acquired in single ion monitoring mode at m/z 275 for ropivacaine and m/z 277 for etidocaine. The drug/internal standard peak area ratios (plasma) or peak areas (dialysate) were linked via a quadratic relationship to concentrations. Precision ranged from 1 to 7.6% accuracy was between 92.6 and 109%. The lower limits of quantitation were 1 microg/l in plasma and 2 microg/l in the dialysate. This method was found suitable for the analysis of plasma samples collected during a clinical trial performed in 30 infants undergoing epidural anaesthesia or continuous psoas compartment block.

Liquid-phase microextraction combined with high-performance liquid chromatography for the determination of local anaesthetics in human urine

A simple liquid-phase microextraction (LPME) device combined with high-performance liquid chromatography (HPLC) is presented for the simultaneous analysis of local anaesthetics, lidocaine, bupivacaine, and tetracaine, from human urine sample. An organic solvent showed good compatibility with the mobile phase of the HPLC, o-dibutyl phthalate, was selected. Local anaesthetics are extracted from 6 ml of the feed aqueous solution and human urine sample into a water-immiscible organic solvent suspended at the needle tip of the microsyringe, then the organic solvent was directly introduced to a reversed-phase HPLC system. The kind of the organic extraction solvent, the stirring rate, the pH value of the aqueous feed solution, and the extraction time have been discussed. Under the optimized extraction conditions, high enrichment factors (more than 86.0-fold) and significant sample clean-up for all of studied local anaesthetics were achieved within 30 min. The detection limits (lower than 0.05 microg/ml) were comparable with previously reported gas chromatography methods. This method was applied to specimen of patient who was treated with extradural anaesthesia of lidocaine, bupivacaine, and tetracaine, and revealed that simultaneous determination of above three local anaesthetics in human urine was possible.

Sensitive bioassay of bupivacaine in human plasma by liquid-chromatography-ion trap mass spectrometry

A sensitive high-performance liquid chromatography-tandem mass spectrometric (HPLC-MS-MS) method, using an ion trap spectrometer, was developed for quantitation of bupivacaine in human plasma. Bupivacaine and an internal standard (ropivacaine) were extracted in a single step from 100 microL of alkalinized plasma with diethyl-ether. The mobile phase consisted of acetonitrile with 0.1% formic acid (50:50, v/v), and was delivered at a flow rate of 0.3 mL/min. The effluent was detected by MS-MS in positive ion mode. Ionisation was performed, using an electrospray ion source, operating at 200 degrees C. The selected reaction monitoring transitions m/z 289-->m/z 140 and m/z 275-->m/z 126 were chosen for bupivacaine and ropivacaine, respectively. Calibration curves were linear over the concentration range of 3.90-500 microg/L with determination coefficients >0.996. The method is accurate (bias <10%) and reproducible (intra-assay and inter-assay precision <15%), with a quantitation limit of 3.90 microg/L, using only 100 microL of plasma. The high specificity and sensitivity, achieved by this fast method (total run-time <3 min), allowed the determination of bupivacaine plasma levels in pediatric patients, following epidural administration of bupivacaine.