Ion-pair Chromatographic Method Research Articles

Isocratic ion pair chromatography for estimation of novel combined inhalation therapy that blocks coronavirus replication in chronic asthmatic patients

A rapid and sensitive isocratic ion-pair chromatographic method was developed for the accurate analysis of ternary mixtures of formoterol, tiotropium, and ciclesonide in their novel combined inhalation that is widely used for the symptomatic treatment of patients with chronic obstructive disease. Analytical separation was performed using a C8 column and ion pair mobile phase composed of acetonitrile: acidified deionized water (55: 45% v/v) containing 0.025% sodium dodecyl sulfate. The pH was adjusted to 3.0 using orthophosphoric acid and eluted isocratically at 2.0 mL/min and 40 °C applying UV detection at 237 nm. The calibration ranges were found to be 0.3–9.0 µg/mL for formoterol, 0.45–13.5 µg/mL for tiotropium, and 10.0–300.0 µg/mL concerning ciclesonide. The proposed method exhibited good repeatability, accuracy, and sensitivity (R.S.D. < 2.0%). The approach is rapid (run time does not exceed 15 min) and achieves satisfactory resolution (resolution factors = 7.45 and 5.3 between formoterol and tiotropium and tiotropium and ciclesonide respectively). The sensitivity and the efficiency of the proposed method permit their successful estimation with a recovery percentage ± SD of 99.33% ± 0.43 for formoterol, 99.15% ± 0.60 for tiotropium, and 99.90% ± 0.41 for ciclesonide.

Development and Validation of a Novel HPLC Method for the Determination of Ephedrine Hydrochloride in Nasal Ointment

A simple, precise, and cost-effective reverse phase ion pair chromatographic (RP-IP-HPLC) method was developed and validated for the determination of Ephedrine Hydrochloride in a nasal ointment. A simple and fast extraction protocol was developed for the effective recovery of the analyte, and for this purpose, Bromhexine Hydrochloride was used as the internal standard. The mobile phase consisted of MeOH, Sodium Lauryl Sulfate (SLS) 49.8 mM, triethylamine (ET3N) in the ratio of 65:34.6:0.4%, respectively, with pH = 2.20. The detection of the compounds was carried out at 206 nm, and we used a PDA detector. A short run time was achieved with retention times of 6.3 min and 9.8 min for ephedrine hydrochloride and the internal standard, respectively. The proposed method was validated according to ICH guidelines. Linearity was confirmed in the range of 50–150 μg/mL. Recoveries results were within the range of 98–102% and precision &lt; 2% for the analyte in spiked blank matrix. Robustness testing was conducted via a fractional factorial experimental design. The method was found to fulfill the required specifications for specificity and stability for both standard solutions and samples, as well and applied to the determination of ephedrine hydrochloride in nasal ointments produced by the Greek Military Pharmaceutical Laboratories.

Analytical methods for estimation of Budesonide in bulk and in Pharmaceutical dosage forms: A Review

Budesonide is a potent glucocorticoid with a high local anti-inflammatory effect and low systemic bioavailability. The inhaled form is used in the long-term management of asthma and chronic obstructive pulmonary disease. Several analytical methods including UV, HPLC, LC-MS techniques has been developed for Budesonide alone and in combination with others. Methods indicating HPLC bioanalytical method, stability indicating HPLC method, ion pairing chromatographic method and chemometrics assisted HPLC methods are also described for Budesonide. For qualitative and quantitative estimation of Budesonide these analytical methods can be used. The following study describes reported analytical methods of Budesonide.

Development of Ion pair Chromatography Method for Assay of Telaprevir by Response Surface Methodology

Response surface methodology approach has been utilized for the assay of Telaprevir in pure and formulation using ion-pair chromatography. In this, A risk assessment approach (Control-Noise-Experiment) has been used for identifying the risk factors, i.e. Percentage of Organic Modifier (% Acetonitrile), Buffer’s pH and flow rate of the method. The Central Composite design was applied to optimize the critical method parameters (CMPs) and to find out the Design space (DS) of the method. The coefficient of correlation (R2),%CV and Lack of fit are utilized for the evaluation of method responses (Retention time and Asymmetric factor Evaluation of model is justified by two diagnostic plots (normal probability plot of residuals and plot of residuals vs predicted values). The mobile phase is Acetate Buffer (20mM) pH 4.4: Acetonitrile (35:65) with 0.9 ml/min of Flow rate. The separation has taken placed in the Eclip Plus C-18 column (250 × 4.6 mm, 5μm) at 268 nm. The retention time of Boceprevir was found to be 4.6 min. The validation of the optimized method has performed according to ICH guideline. The method has been successfully used for routine analysis of the Telaprevir throughout the life cycle of the product.

Updating the European Pharmacopoeia impurity profiling method for terazosin and suggesting alternative columns

This work was motivated by the demand of European Directorate for the Quality of Medicines and HealthCare (EDQM). A new liquid chromatographic (LC) method was developed for terazosin impurity profiling to replace the old European Pharmacopoeia (Ph. Eur.) method. This new method is published as part of the new Ph. Eur. monograph proposal of terazosin in Pharmeuropa issue 32.2.The aim of the method renewal was to cut the analysis time from 90 min (2 × 45 min) down to below 20 min. The Ph. Eur. monograph method is based on two different chromatographic separations to analyze the specified impurities of terazosin. The reason for the two methods is that two of the impurities are not sufficiently retained in reversed phase (RP) conditions, not even with 100% water as eluent. Therefore, next to RP, an ion-pair (IP) chromatographic method has to be applied to analyze those two impurities.With our new proposed method it was possible to appropriately increase the retention of the two critical compounds using alternative stationary phases (instead of a C18 phase which is suggested by the Ph. Eur. method). Applying a pentafluoro-phenyl (PFP) stationary phase, it was feasible to separate and adequately retain all the impurities. The detection wavelength was also changed compared to the Ph. Eur. method and is now appropriate for the detection and quantification of all impurities using perchloric acid in the mobile phase at low pH.Another goal of the present study was to develop a generic workflow and to evaluate the chromatographic resolution in a wide range of method variables and suggest some replacement columns for terazosin impurity profiling. Retention modeling was applied to study the chromatographic behavior of the compounds of interest and visualize resolution for the different columns, where a given criterion is fulfilled. A zone (set of chromatographic conditions) of a robust space could be then quickly identified by the overlay of the individual response surfaces (resolution maps).It was also demonstrated that two columns from different providers (Kinetex F5 and SpeedCore PFP) can be used as replacement columns, providing sufficient resolution at the same working point and a high degree of robustness.

Monolithic Column Ion-Pair Chromatography with Indirect Ultraviolet Detection for the Determination of Three Acid Radical Anions Containing Fluorine in Ionic Liquids

A rapid ion-pair chromatographic method was developed on a monolithic column for the determination of trifluoroacetate, trifluoromethanesulfonate, and tetrafluoroborate. The three anions were successfully detected using indirect ultraviolet detection. These analyte anions were separated using a tetrabutylammonium hydroxide - p-toluenesulfonic acid – acetonitrile mobile phase on a silica-based monolithic column with an octadecyl functional group. The effects of detection wavelength, mobile phase, column temperature and flow rate on the retention of the anions were investigated. The chromatographic conditions were optimized and the retention properties were evaluated. Under the selected optimal conditions, the successful separation of the anions was achieved within 3.5 min. The detection limits were less than 1.0 mg/L for trifluoroacetate, trifluoromethanesulfonate, and tetrafluoroborate. The relative standard deviations for five repeated measurement of retention time and peak area were no more than 0.2%. The linear ranges extended across two orders of magnitude. The three anions in synthetic ionic liquid samples were successfully separated and detected by this method. The results show that the recoveries of this method were between 94.0% and 99.0%. The method was rapid, simple, and easy to use.

Multiple analytical methods for determination of formoterol and glycopyrronium simultaneously in their novel combined metered dose inhaler

One of the major causes of mortality all over the world is chronic obstructive pulmonary disease (COPD). Recently approved combined inhaler of formoterol fumarate (FF) and glycopyrronium bromide (GLY) has been used in very low concentrations (µg level/actuation) doses in COPD patients. The first spectrophotometric and advanced highly sensitive liquid chromatography has been achieved successfully throughout this study, permitting validated analysis of dual combined inhaler in raw material as well as pharmaceutical inhaled dosage form. Three sensitive analytical methods were carried out for the simultaneous assay of FF and GLY in their novel combined Metered dose inhaler (MDI). The first method depends on measuring the first derivative amplitudes at 208.27 nm for FF and at 213.27 nm and 239.86 nm for GLY, respectively. The second method depends on measurement of the first derivative of the ratio spectra at 214 or 229 nm for FF and 240 or 259 nm for GLY, respectively. For the spectrophotometric methods, the linearity ranges were 0.48–9.6 µg/mL for FF and 0.9–18 µg/mL for GLY. For the third method, valid ion-pairing chromatographic method was carried out applying C18 column and isocratic mobile phase of 60% v/v acetonitrile and 40% v/v deionized waster (pH 3.0) enclosing 0.025% sodium dodecyl sulfate, using UV detection adjusted to 210 nm and flow rate of 1.2 mL/min. For the ion-pairing chromatographic method, the linearity ranges were 0.048–4.8 µg/mL for FF and 0.09–9.0 µg/mL for GLY. The developed methods are reproducible, valid and offer efficient resolution between formoterol and glycopyrronium using spectrophotometric methods and highly sensitive and precise chromatographic method. The percent recoveries of the inhaled drugs in their MDI were good. The method was successfully established for the quantitative analysis of FF and GLY in their combined pharmaceutical inhaler capsules to validate the therapeutic efficiency of the combined drugs in quality control labs.

Development and Validation of a Novel Stability-Indicating Reversed-Phase Ion-Pair Chromatographic Method for the Quantitation of Impurities in Marbofloxacin Tablets

A stability-indicating isocratic reversed-phase ion-pair chromatographic method was designed for the separation of impurities in the presence of degradation products. Marbofloxacin tablets and a placebo were exposed to the stress conditions of oxidative, acid, base, humidity, thermal, and photolytic degradation. Significant and moderate degradation was observed in acidic and oxidative stress conditions, respectively. The degradation products were well resolved from the main peak and its impurities, thus proving the stability-indicating analytical method. The method was developed by using an XTerra RP18 3.5 μm (150 × 4.6 mm) column, with the mobile phase containing a mixture of buffer (pH 2.5)-methanol-glacial acetic acid (77 + 23 + 0.5, v/v). The flow rate of the mobile phase was 1.2 mL/min, with a column oven temperature of 40°C and a detection wavelength of 315 nm. The proposed method met Veterinary International Conference on Harmonization requirements and was successfully used for impurity quantitation in marbofloxacin tablets.

Validated ion pair chromatographic method for simultaneous determination and in vitro dissolution studies of indacaterol and glycopyrronium from inhaled capsule dosage form

A rapid, and highly sensitive analytical method were developed for the simultaneous determination of indacaterol maleate (IND) and glycopyrronium bromide (GLY) in their inhaler capsules. Valid ion-pairing chromatographic (IPC) method was performed for separation of GLY in presence of IND using C18 column and mobile phase consisting of acetonitrile: acidified deionized water (60:40% v/v) containing 0.02% sodium dodecyl sulfate (SDS) adjusted to pH 3.0 using OPA (orthophosphoric acid) isocratically eluted at 2.0 mL/min. Quantitation was achieved with UV detection at 210 nm. Cyproheptadine was used as an internal standard. The retention times were 1.9 and 2.5 min for IND, and GLY, respectively. For the IPC method, the calibration graphs were linear in the range of 0.66–66.0 μg/mL for IND and 0.3–30.0 μg/mL for GLY. The proposed method are rapid, reproducible (R.S.D. <2.0%) and achieves satisfactory resolution between IND and GLY (resolution factor = 4.23). The mean recoveries of the analytes in their inhaler capsule were satisfactory. It was applied successfully to in vitro dissolution testing using Franz diffusion cell and extended to a content uniformity test consistent with the United States Pharmacopoeia (USP) guidelines and were found to be precise and accurate for the capsules studied with acceptance value of 4.53 and 1.39 for IND and GLY, respectively.

Study of chromium species release from metal implants in blood and joint effusion: Utilization of HPLC-ICP-MS

The objective of this study was to develop and validate a novel analytical procedure for determination of total chromium and Cr(III) and Cr(VI) species released from metal implants into whole blood and joint effusion. Firstly, the ion-pair chromatographic method employing reversed-phase high-performance liquid chromatography inductively coupled plasma mass spectrometry (ICP-MS) for analysis of species was developed. Secondly, all samples, protein and low molecular fractions were analyzed for their total chromium content using ICP-MS. This new measurement procedure was validated by the following parameters: limit of detection (0.13 μg L-1 for Cr(III), 0.14 μg L-1 for Cr(VI)), linearity of calibration, trueness (recovery 84–92%), intermediate precision (RSD < 5%). We determined statistically significantly higher chromium levels in joint effusion samples obtained from patients in comparison with a control group. On the other hand, no relevant difference among the concentrations of both species and total chromium in blood was observed. Our results show that the majority of chromium is present in the trivalent form and bound to proteins. This speciation study is rare in the field of speciation analysis in clinical samples. It is characterized by very fast and simple sample preparation without any changes in distribution or stability of both Cr forms and efficient simultaneous analysis of Cr species.

Reversed phase ion-pair chromatographic separation of sugar alcohols by complexation with molybdate ion

In this study, we developed a simple and sensitive reversed phase ion-pair chromatographic method for the analysis of C4-C6 sugar alcohols. The method is based on the on-line complexation of sugar alcohols with molybdate ion. The resulting dinuclear anionic complexes can be separated on a reversed-phase C18 column using tetrabutylammonium chloride as an ion-pairing reagent. The mobile phase (pH 3.1) consisted of 0.1 mM disodium molybdate, 1 mM hydrochloric acid and 0.4 mM tetrabutylammonium chloride – 10% v/v methanol. By complexing with molybdate ion, sugar alcohols can be detected by their UV absorption at 247 nm with high resolution and sensitivity. The quantification limits of the examined sugar alcohols calculated at S/N = 10 were 0.1 mM for erythritol and xylitol and 0.01 mM for arabitol, sorbitol, mannitol and dulcitol. The detector response was linear over three orders of magnitude of sugar alcohol concentration. The proposed method was successfully applied to measure sugar alcohols in health drinks, eyedrops and mouthwashes.

Analysis of a variety of inorganic and organic additives in food products by ion-pairing liquid chromatography coupled to high-resolution mass spectrometry.

A reversed-phase ion-pairing chromatographic method was developed for the detection and quantification of inorganic and organic anionic food additives. A single-stage high-resolution mass spectrometer (orbitrap ion trap, Orbitrap) was used to detect the accurate masses of the unfragmented analyte ions. The developed ion-pairing chromatography method was based on a dibutylamine/hexafluoro-2-propanol buffer. Dibutylamine can be charged to serve as a chromatographic ion-pairing agent. This ensures sufficient retention of inorganic and organic anions. Yet, unlike quaternary amines, it can be de-charged in the electrospray to prevent the formation of neutral analyte ion-pairing agent adducts. This process is significantly facilitated by the added hexafluoro-2-propanol. This approach permits the sensitive detection and quantification of additives like nitrate and mono-, di-, and triphosphate as well as citric acid, a number of artificial sweeteners like cyclamate and aspartame, flavor enhancers like glutamate, and preservatives like sorbic acid. This is a major advantage, since the currently used analytical methods as utilized in food safety laboratories are only capable in monitoring a few compounds or a particular category of food additives. Graphical abstract Deptotonation of ion pair agent in the electrospray interface.

Development and Validation of an Analytical Method for Related Substances in N-acetyl–L-cysteine Effervescent Tablets by RP-HPLC

Background: The reported chromatographic methods for N-acetyl cysteine [NAC] are reverse phase HPLC and ion pair chromatography [IPC] for related substances test in bulk and in formulations. No reported stability indicating methods for the estimation of related substances in NAC effervescent formulation was found in literature. Objective: The present work was aimed at developing a selective, sensitive and reproducible stability indicating high-performance liquid chromatographic method for the quantitative determination of known, unknown impurities, degradation impurities and processrelated impurities of NAC effervescent formulation. Method: A reversed phase ion pair chromatographic method was developed employing Cadenza C18 column as the stationary phase and 0.01M octane sulphonate [pH 2.20], methanol and acetonitrile in the ratio 90:8:2 as the mobile phase. A gradient programme was followed with a run time of 55 minutes. 0.3 M hydrochloric acid was selected as the optimum diluent. The performance of the method was validated according to the ICHQ2R1 guidelines. Results: The method was found to be linear from 1.5 to 25μg/ml for impurities A, C and D and from 2.0 to 25 μg/ml for impurity B. The official impurities C and D were mapped in all stress conditions. Additionally, impurity B was also seen in acidic conditions. Conclusion: The results from the study demonstrate that the method is suitable for evaluating the stability of NAC effervescent tablet.

Simultaneous Determination of Formoterol Fumarate and Budesonide Epimers in Metered Dose Inhaler Using Ion-Pair Chromatography.

A simple, accurate and valid ion-pairing chromatographic method was developed for the simultaneous determination of formoterol fumarate (FF) and budesonide (BUD) epimers in metered dose inhaler. The separation was performed on C-18 column using mobile phase consisting of acetonitrile:0.05 M sodium acetate buffer (40:60% v/v) containing 0.03% sodium dodecyl sulfate adjusted to pH 3.1 using increasing volumes of either TEA or orthophosphoric acid isocratically eluted at 1.0 mL/min. Quantitation was achieved with UV detection at 214 nm. The retention times were 3.22, 6.41 and 6.91 min for formoterol fumarate, budesonide epimers B and A, respectively. The linearity range was 0.05-5.0 μg/mL for formoterol fumarate and 0.5-50.0 μg/mL for budesonide. The method was validated for, linearity; lower limit of quantification, lower limit of detection accuracy and precision. The proposed method is rapid (7 min), reproducible (RSD < 2.0%) and achieves satisfactory resolution between FF and BUD B (resolution factor = 12.07). The mean recoveries of the analytes in metered dose inhaler (99.97 and 99.83% for FF and BUD, respectively) were satisfactory.

An Efficient Ion-Pair Liquid Chromatographic Method for the Determination of Some H2 Receptor Antagonists.

A simple, efficient and reliable ion-pair chromatography (IPC) method was developed and validated for the determination of some H2 receptor antagonists including ranitidine (RAN), nizatidine (NIZ) and famotidine (FAM). The use of IPC separations provided improved peak resolution with good peak shape in short analysis time and augmented method selectivity compared with the frequently used RP-C18 methods. A simple isocratic mode with mobile phase containing acetonitrile and 20 mM acetate buffer (50 : 50, v/v) containing 20 mM sodium dodecyl sulfate was used for separation. The flow rate was set at 1.0 mL min(-1), and the effluent was monitored by UV detector at 280 nm FAM and 320 nm for NIZ and RAN. The method was validated in accordance with International Conference on Harmonization guidelines and shown to be suitable for intended applications. The limits of detections and quantitations were 0.008-0.011 and 0.025-0.033 µg mL(-1), respectively. The proposed IPC method was successfully applied for the determination of pharmaceutical dosage forms without prior need for separation. Additionally, the developed method was applied for the determination of RAN in rabbit plasma using NIZ as the internal standard. The method entailed direct injection of the plasma samples after deproteination using methanol. Finally, the proposed IPC method was applied successfully in a pharmacokinetic study for RAN in rabbits after a single oral dose of RAN.

A sensitive and reliable method for therapeutic monitoring of α1-blockers in rabbit plasma by ion-pair chromatography with enhanced fluorescence detection

A sensitive, reliable and reproducible ion-pair chromatographic (IPC) method with enhanced fluorescent detection suitable for therapeutic drug monitoring was developed and validated for the determination of α1-blockers. The chromatographic and fluorescence enhancement conditions were optimized for maximum sensitivity and selectivity. Sodium dodecyl sulfate (SDS) has a dual role in the newly developed IPC method as an ion pair reagent as well as enhancement of the native fluorescence of the studied drugs. Additionally, a simple isocratic separation mode with mobile phase containing acetonitrile and 20mM phosphate buffer (pH6.3) (60:40, v/v) containing 25mM SDS was the best for separation. The flow rate was set at 0.8mLmin−1 and the effluent was monitored by a fluorescence detector and the wavelengths at emission wavelength of 389nm after excitation at =250nm. The developed IPC method provided rapid separation of α1-blockers with good peak resolution compared with conventional reversed phase (RP-C18) methods. The method was validated in accordance with the requirements of USP-FDA guidelines and shown to be suitable for intended applications. The linearity range for the developed IPC method in rabbit plasma obtained was 0.5–20ngmL−1 with correlation coefficients of more than 0.9985. The limits of detection (S/N=3) and quantification (S/N=10) were 0.16–0.71ngmL−1 and 0.53–2.14ngmL−1, respectively. The inter-day and intra-day precision % RSD was 1.14–3.91 and accuracy of 9.06–102.3%. The proposed IPC–FL method was successfully applied for the bioequivalence study of two formulations for terazosin from different brands in rabbits by a randomized, two-way, single-dose, crossover study and proved to be bioequivalent.

A quantitative LC/MS method targeting urinary 1-methyl-4-imidazoleacetic acid for safety monitoring of the global histamine turnover in clinical studies

Anaphylaxis is a potentially life-threatening condition triggered mainly by the release of inflammatory mediators, notably histamine. In pharmaceutical research, drug discovery, and clinical evaluation, it may be necessary to accurately assess the potential of a compound, event, or disorder to promote the release of histamine. In contrast to the measurement of plasma histamine, determination of the stable metabolite 1-methyl-4-imidazoleacetic acid (tele-MIAA) in urine provides a noninvasive and more reliable methodology to monitor histamine release. This study presents a repeatable high-performance liquid chromatography coupled to electrospray mass spectrometry (LC-ESI-MS) method where tele-MIAA is baseline separated from its structural isomer 1-methyl-5-imidazoleacetic acid (pi-MIAA) and an unknown in human urine. The ion-pairing chromatography method, in reversed-phase mode, based on 0.5 mM tridecafluoroheptanoic acid demonstrated high repeatability and was applied in a clinical development program that comprised a large number of clinical samples from different cohorts. The inter- and intra-run precision of the method for tele-MIAA were 8.4 and 4.3%, respectively, at the mean urinary concentration level, while method accuracy was between -16.2 and 8.0% across the linear concentration range of 22-1,111 ng mL(-1). Overall, method precision was greater than that reported in previously published methods and enabled the identification of gender differences that were independent of age or demography. The median concentration measured in female subjects was 3.0 μmol mmol(-1) of creatinine, and for male subjects, it was 2.1 μmol mmol(-1) of creatinine. The results demonstrate that the method provides unprecedented accuracy, precision, and practicality for the measurement of tele-MIAA in large clinical settings.

RAPID METHOD FOR DETERMINATION OF HOMOLOGUE IMIDAZOLIUM IONIC LIQUID CATIONS BY ION-PAIR CHROMATOGRAPHY USING A MONOLITHIC COLUMN

A fast and gradient ion-pair chromatographic method was developed for determination of five homologue imidazolium ionic liquid cations using a silica-based monolithic column and ultraviolet detection. Chromatographic separations were performed on a Chromolith Speed ROD RP-18e column with 1-heptanesulfonic acid sodium aqueous solution (pH adjusted by citric acid)–acetonitrile as the mobile phase. The effects of chromatographic column, mobile phase, flow rate, and column temperature on retention and separation of the cations were investigated. The retention rules of homologue imidazolium cations were discussed. The results showed that the analysis time could be significantly reduced owing to the application of monolithic column. Simultaneous and fast separation of five imidazolium cations was achieved under the optimum chromatographic conditions. Detection limits (S/N = 3) for the cations were 0.26–1.61 mg/L. Relative standard deviations (n = 5) for peak areas and retention times were less than 0.8%. The method has been successfully applied to the determination of two ionic liquids synthesized by chemistry lab. Recoveries of the cations after spiking were 96.8–101.9%.

Determination of ionic liquid anions of trifluoroacetate, thiocyanate, tetrafluoroborate and trifluoromethanesulfonate by ion-pair chromatography with direct conductivity detection

An ion-pair chromatographic method with direct conductivity detection was established on a reversed-phase silica-based column for the simultaneous determination of ionic liquid anions of trifluoroacetate, thiocyanate, tetrafluoroborate and trifluoromethanesulfonate. The analytes were separated using a mobile phase of ion pair reagent-malic acid-acetonitrile on the Diamonsil C18 column. The effects of mobile phase composition and column temperature on the retention of the anions were investigated. The optimized chromatographic conditions were as follows: 0.15 mmol/L tetrabutylammonium hydroxide-0.099 mmol/L malic acid-20% (v/v) acetonitrile aqueous solution (pH 6.5) as mobile phase, a column temperature of 25 degrees C. Under the optimal conditions, the baseline separation of trifluoroacetate, thiocyanate, tetrafluoroborate and trifluoromethanesulfonate was achieved without any interference by other ordinary anions (fluoride, chloride, bromide, nitrate, sulfate). The detection limits (S/N = 3) were 0.21, 0.07, 0.36 and 0.12 mg/L for trifluoroacetate, thiocyanate, tetrafluoroborate and trifluoromethanesulfonate, respectively. The method has been applied to the determination of the four anions in ionic liquids. The spiked recoveries of the anions were from 95.0% to 104.6%. The results demonstrate that the convenience, rapidity, sensitivity and accuracy are fit for the requirements of quantitative analysis of trifluoroacetate, thiocyanate, tetrafluoroborate and trifluoromethanesulfonate in ionic liquids.

Determination of antazoline hydrochloride in rat plasma and excreta by reversed‐phase ion‐pair chromatography and its application to pharmacokinetics

A reversed-phase ion pair chromatography method with liquid-liquid extraction analytical method was developed and validated for the determination of antazoline hydrochloride in plasma and excreta of rat. The aim of our study was to characterize the preclinical pharmacokinetics and excretion profiles of antazoline hydrochloride in rats after intravenous injection at the dose of 10 mg/kg. Plasma and excreta samples were extracted with ethyl acetate, and phenacetin was used as the internal standard. The result showed that the method is suitable for the quantification of antazoline hydrochloride in plasma and excreta samples. Analysis of accuracy (90.89-112.33%), imprecision (<7.1%) and recovery (>82.5%) showed adequate values. After a single intravenous administration at 10 mg/kg to rats, plasma concentration profile showed a relative fast elimination proceeding with a terminal elimination half-life of 3.53 h. Approximately 61.8 and 14.2% of the administered dose were recovered in urine and bile after 72 and 24 h post-dosing respectively; 5.9% of the administered dose was recovered in feces after 72 h post-dosing. The above results show that the major elimination route is urinary excretion.