LC Separation and Determination of Five Diester-Diterpenoid Alkaloids in the Unprocessed and Processed Aconite Roots

A reliable liquid chromatographic method with photodiode array detector (DAD) was developed and validated for simultaneous separation and determination of five diester-diterpenoid alkaloids in the aconite roots. The separation was successfully performed on a Zorbax Extend-C₁₈ column with a mobile phase gradient prepared from methanol and ammonia solution at a flow rate of 1.0 mL min⁻¹. Good linearity (r > 0.999) was observed over the concentration ranges investigated, and intra-day and inter-day precision were high. The mean recoveries of five components ranged from 90.45 to 102.63% and relative standard deviations were always <5%. The validated method was successfully used for simultaneous determination of the five diester-diterpenoid alkaloids of unprocessed and processed aconite roots. The quantitative method provided a scientific basis for safety assurance and clinical application of aconite roots.

     

Combined use of carbon nanotubes and ionic liquid to improve the determination of antidepressants in urine samples by liquid chromatography

Antidepressants are widely used for the treatment of psychiatric disorders and therefore their monitoring in biological fluids is quite important taking into account that they can produce dangerous biochemical imbalances in toxic doses. A method for the determination of antidepressants in urine samples is presented using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. Home-made cartridges containing 30 mg multiwall carbon nanotubes are employed for isolation of the analytes from the sample, allowing also the preconcentration of the analytes prior to the HPLC analysis. Chromatographic separation was achieved in a reversed-phase C₈ column using the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate as silanol activity suppressor, which enhances peak symmetry and chromatographic resolution. Limits of detection were 12.3 ng mL⁻¹ for trazodone and 90.1 ng mL⁻¹ for fluoxetine. The repeatability of the proposed method expressed as RSD (n = 11) varied between 3.4% (fluoxetine) and 5.0% (desipramine and mianserine). Thus, the method is suitable for the therapeutic monitoring of antidepressants in urine samples.     

LC Separation and Determination of Five Diester-Diterpenoid Alkaloids in the Unprocessed and Processed Aconite Roots

A reliable liquid chromatographic method with photodiode array detector (DAD) was developed and validated for simultaneous separation and determination of five diester-diterpenoid alkaloids in the aconite roots. The separation was successfully performed on a Zorbax Extend-C₁₈ column with a mobile phase gradient prepared from methanol and ammonia solution at a flow rate of 1.0 mL min^?1. Good linearity (r > 0.999) was observed over the concentration ranges investigated, and intra-day and inter-day precision were high. The mean recoveries of five components ranged from 90.45 to 102.63% and relative standard deviations were always <5%. The validated method was successfully used for simultaneous determination of the five diester-diterpenoid alkaloids of unprocessed and processed aconite roots. The quantitative method provided a scientific basis for safety assurance and clinical application of aconite roots.     

Non-aqueous capillary electrophoresis of biological samples after at-line solid-phase extraction

Summary Solid-phase extraction (SPE) was coupled at-line to capillary electrophoresis (CE) for the determination of a series of basic test compounds (i. e. tricyclic antidepressants). The analysis was performed using a non-aqueous CE buffer, which resulted in baseline separation of all test compounds. This is in marked contrast with CE using aqueous buffers where hardly any separation was obtained either with or without micelles. The SPE procedure was used to remove simultaneously most of the water from the sample, because no direct analysis of aqueous samples is possible when a non-aqueous CE buffer is used. With the present method the antidepressants can be determined in both urine and serum. Analyte detectability is increased up to 10-fold due to trace enrichment during the extraction process; the limits of detection (LODs; UV 214 nm) are 30–300 ng mL⁻¹ in urine and 300–1000 ng mL⁻¹ in serum. TheRSD values (n=5) of the within-day and between-day precision are below 9% and 11% respectively. Therefore, the present procedure can be used for drug monitoring.     

Statistical Optimization Applied to Simultaneous Determination of Maprotiline, Desipramine, and Moclobemide by Capillary Zone Electrophoresis

Summary. A method of Capillary Zone Electrophoresis (CZE) for separation of three most-frequently prescribed antidepressants in the market: maprotiline, desipramine, and moclobemide was developed. The proposed method is fully validated for a ternary laboratory mixture but it is also suitable for individual determination of the investigated components in pharmaceutical dosage forms. Since the preliminary investigations did not show complete separation because of close migration time of desipramine and maprotiline, a complete set, 2³ experimental design was applied. All the factors that affect separation as well as their mutual interactions were investigated. Voltage, temperature of capillary and the pH of phosphate buffer were independent variables or factors to be investigated in two levels. Applying response surface methodology, from experimental points the appropriate graphs were constructed and optimal chromatographic conditions for the separation were defined. The optimum conditions were: running voltage of 20 kV, phosphate buffer (pH = 2.35), temperature 25°C, and UV detection at 200 nm. An uncoated (fused silica) capillary (50 μm i.d.) with a total length of 50 cm and a distance of 47 cm between the injection and detection points was used.     

Cloud-point extraction and reversed-phase high-performance liquid chromatography for the determination of carbamate insecticide residues in fruits

A cloud-point extraction (CPE) method using Triton X-114 non-ionic surfactant was developed for the extraction and preconcentration of carbamate insecticide residues (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) in fruit samples. The optimum conditions of CPE were 1.5% (w/v) Triton X-114, 7.0% (w/v) NaCl and 20 min equilibrated at 45 °C. The surfactant-rich phase was then analyzed by reversed-phase high-performance liquid chromatography with ultraviolet detection at 270 nm, under gradient separation using methanol and 0.1% (v/v) acetic acid. Under the study conditions, six carbamate insecticides were successfully separated within 27 min. Good reproducibility was obtained with the relative standard deviation of <3% for retention time and <9% for peak area. Limits of detection in the studied fruit samples were in the range of 0.1–1.0 mg kg⁻¹. No carbamate insecticides were detected in the studied fruit samples. The high recoveries of the spiked fruit samples were obtained in the range 80.0–107%. The CPE method has been shown to be a potential useful methodology for the preconcentration of the target analytes, with a preconcentration factor of 14. Moreover, the method is simple, has high sensitivity, consumes much less solvent than traditional methods, and is environmental friendly.     

超高效液相色谱-串联质谱法同时测定中成药和保健品中9种抗抑郁药物

建立了同时测定中成药和保健品中9种抗抑郁药物的超高效液相色谱-串联质谱（UPLC-MS/MS）分析方法。以甲醇为提取溶剂,超声提取,离心后取上清液,使用Waters ACQUITY UPLC BEH C₁₈色谱柱（100 mm×2.1 mm,1.7 μm）进行分离,以乙腈和0.1%（v/v）甲酸水为流动相对目标物进行梯度洗脱。在电喷雾正离子模式下,采用多反应监测（MRM）模式进行定性和定量分析。结果表明,9种抗抑郁药物在0.04~20 μg/L范围内线性关系良好,线性相关系数（R²）均大于0.998;目标物的检出限为0.0068~0.034 μg/L;在0.5、1、5 μg/L 3个添加水平下的平均回收率为77.7%~100.8%,相对标准偏差为0.9%~9.1%。本方法准确、简便、快速,可用于中成药和保健品中抗抑郁药物的检测。     

LC–MS/MS method for simultaneous determination of flavonoids and physalins in rat plasma: Application to pharmacokinetic study after oral administration of Physalis alkekengi var. franchetii (Chinese lantern) extract

A rapid and sensitive liquid chromatography with tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the simultaneous determination of luteolin, luteolin‐7‐O ‐β ‐D‐glucopyranoside, physalin A, physalin D and physalin L in rat plasma. Scutellarein and dexamethasone were used as the internal standards (IS). Plasma samples were prepared by liquid‐liquid extraction with ethyl acetate. The five constituents were separated on an Acquity UPLC BEH C₁₈ column (100 mm × 2.1 mm, 1.7 μm). A gradient elution procedure was used with acetonitrile (A)‐0.1% aqueous formic acid (B). Mass spectrometric detection was performed in negative ion multiple reaction monitoring mode with an electrospray ionization (ESI) source. This method showed good linearity (r ² > 0.997) over a concentration range of 2.0–500 ng/mL with a lower limit of quantification of 2.0 ng/mL for all five compounds. The inter‐ and intra‐day accuracy ranged from 91.7 to 104%, and precisions (RSD) were <6.46% for all analytes. The extraction recoveries of all analytes were >85%. This validated method was successfully applied for the first time to the pharmacokinetic study of five ingredients after oral administration of 70% ethanol extract of Chinese lantern in rats.     

High‐performance liquid chromatography tandem mass spectrometry method for quantification of endothelin receptor antagonist drug,ambrisentan, in human plasma and its application in a pharmacokinetic study

A simple and sensitive liquid chromatography tandem mass spectrometry method has been developed for the quantification of ambrisentan (AMB) in human plasma using midazolam (MID) as an internal standard (IS). Chromatographic separation was performed using a Beta Basic‐8 (50 × 4.6 mm, 5 µm) column with an isocratic mobile phase. AMB and MID were detected with proton adducts at m/z 379.09 → 303.12 and 326.15 → 291.14 in multiple reaction monitoring‐positive mode, respectively. A solid‐phase extraction method was used for extraction of the analyte and IS from the plasma samples. The method was shown to be reproducible and reliable with within‐run precision <11%, between‐run precision <14% and linear concentration range from 10.0 to 2000.2 ng/mL, with a correlation coefficient (r²) of >0.995. The method was successfully applied to a pharmacokinetic study of oral administration of AMB (10 mg) in 24 healthy Indian male human volunteers under fasting conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Nonaqueous CE ESI‐IT‐MS analysis of Amaryllidaceae alkaloids

The Amaryllidaceae are widely distributed medical plants. Lycorine, lycoramine, lycoremine, and lycobetaine are the major active alkaloids in Amaryllidaceae plants. A nonaqueous CE ESI‐IT‐MS method for separation, identification, and quantification of the Amaryllidaceae alkaloids has been developed. The MS^1–3 behavior has been studied and the fragmentation pathways of main fragment ions have been proposed. The effects of several factors such as composition and concentration of buffer, applied voltage, composition, and flow rate of the sheath liquid, nebulizing gas pressure, flow rate, and temperature of drying gas were investigated. Under the optimal conditions, the linear concentration range of these compounds was wide with the correlation coefficient (R²) >0.99. RSDs of migration time and peak areas were <10%. The LODs were <240 ng/mL. The proposed method can be successfully applied to the determination of the related alkaloids in the Lycoris radiata roots.     

Development of an HPLC‐DAD method for the determination of five alkaloids in Stephania yunnanensis Lo and in rat plasma after oral dose of Stephania yunnanensis Lo extracts

For the rational utilization and the quantitative quality control of the Stephania yunnanensis Lo, an HPLC‐DAD method was developed for the quantitative and simultaneous determination of five alkaloids in rat plasma (stepharine, sinomenine, palmatine, isocorydine and tetrahydropalmatine), which were the main active chemical constituents of this plant and belong to four kinds of isoquinoline‐type alkaloids (protoberberine, morphine, aporphine and protaporphine alkaloids). The contents of five alkaloids ranged from 0.09 to 2.32% (w/w). The method validation was tested for the linearity (r² > 0.9975), precision (intra‐day RSD < 4.8% and inter‐day RSD < 4.9%), extraction recovery (85.49 ± 2.29% to 99.21 ± 1.48%) and stability (98.5 ± 5.3% to 101.2 ± 3.4%). We developed an HPLC‐DAD method to simultaneously measure these alkaloids in rat plasma after oral administration of the extract of this plant to rats. The results supported the hypothesis that isoquinoline alkaloids were the compounds responsible for the main pharmacological activities for anti‐inflammatory and analgesic.     

Fast separation of selective serotonin reuptake inhibitors antidepressants in plasma sample by nonaqueous capillary electrophoresis

A simple, fast, and sensitive liquid–liquid extraction method followed by nonaqueous capillary electrophoresis (LLE/NACE) was developed and validated for simultaneous determination of four antidepressants (fluoxetine, sertraline, citalopram and paroxetine) in human plasma. Several experimental separation conditions using aqueous and nonaqueous media separation were tested by varying the electrolyte pH value (for aqueous medium) and the ionic strength concentration considering the similar mobility of the compounds. High-resolution separation was achieved with a mixture of 1.25 mol L⁻¹ of phosphoric acid in acetonitrile. The quantification limits of the LLE/CE method varied between 15 and 30 ng mL⁻¹, with a relative standard deviation (RSD) lower than 10.3%. The method was successfully applied in therapeutic drug monitoring and should be employed in the evaluation of plasma levels in urgent toxicological analysis.     

Poly(dimethylsiloxane) microchip capillary electrophoresis with electrochemical detection for rapid measurement of acetaminophen and its hydrolysate

Poly(dimethylsiloxane) microchip capillary electrophoresis with amperometric detection has been used for rapid separation and determination of acetaminophen and its hydrolysate, i.e. p-aminophenol. A Pt ultramicroelectrode with a diameter of 10 m positioned at the outlet of the separation channel was used as a working electrode for amperometric detection. Factors influencing separation and detection were investigated and optimized. Results show that acetaminophen and p-aminophenol can be well separated within 35 s with RSD<1% for migration time and <7% for detection current for both analytes. Detection limits for both analytes are estimated to be 5.0 mol L^–1 (approximately 0.1 fmol) at S/N=3. This method has been successfully applied to the detection of traces of p-aminophenol in paracetamol tablets.     

Determination of Polyvinyl Alcohol Using Gel Filtration Liquid Chromatography

Gel filtration chromatography using a TSKgel G2000 SW column coupled with differential refractive index detection was used to analyse five grades of polyvinyl alcohol. Limits of detection and quantification for the assay were 0.14 mg mL^–1, 0.47 mg mL^–1 respectively. The inter and intra-day co-efficient of variance were both <7%. There was a significant difference (p<0.05, n=5) between the calibration curves across the five grades of PVA due to a refractive index range of 13.0790 –1.3181 (n=3). The assay accuracy was 98.99% ± 8.97% (n=5) and 90.60% ± 7.87% (n=5) of a spiked PVA sample was recovered from a commercial formulation.     

Preconcentration and determination of five antidepressants from human milk and urine samples by stir bar filled magnetic ionic liquids using liquid–liquid–liquid microextraction-high-performance liquid chromatography

A sensitive and straightforward liquid–liquid–liquid microextraction method was developed to preconcentrate and cleanup antidepressants, including mirtazapine, venlafaxine, escitalopram, fluoxetine, and fluvoxamine, from biological samples before analyzing with high-performance liquid chromatography. The essential novelty of this study is using magnetic ionic liquids as the extraction phase in the lumen of hollow fiber and preparing a liquid magnetic stir bar. In this method, polypropylene hollow fiber was utilized as the permeable membrane for the analyte extraction. Six magnetic ionic liquids consisting of the transition metal and rare earth compounds were synthesized and then hollow fiber lumen was injected as acceptor phase to extract the antidepressants. Besides, 3-pentanol as a water-immiscible solvent was impregnated in the hollow fiber wall pores. The effective factors in the method were optimized with the central composition design. The resultant calibration curves were linear over the concentration range of 0.8–400.0 ng mL⁻¹ (R² ≥ 0.996). The method displayed the proper detection limit (0.11–0.24 ng mL⁻¹), the reasonable limit of quantification (≤0.79 ng mL⁻¹), wide linear ranges, high preconcentration factors (≥294.3), and suitable relative standard deviation (2.31–5.47%) for measuring antidepressant medications. Analysis of human milk and urine samples showed acceptable recoveries of 96.5–103.8% with excellent relative standard deviations lower than 5.95%.     

Simultaneous HPLC Determination of Five Flavonoids in Flos Inulae

A simple and accurate reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed for simultaneous determination of five flavonoids, spinacetin, quercetin, luteolin, 6-methoxyluteolin, and isorhamnetin, in an extract of the flowers of Inula britannica L., an important Traditional Chinese Medicine (TCM). Samples were extracted with 80% ethanol. Optimum separation and detection were achieved on an ODS-3 column with a methanol–acetonitrile gradient containing 0.49% (v/v) citric acid as mobile phase. The flow rate was 1.0 mL min⁻¹ and detection was at 360 nm. All calibration plots revealed linearity was good (r ² = 0.999) within the concentration ranges tested. Repeatability was evaluated by performing intra-day and inter-day assays; relative standards deviations (RSD) were less than 2.8%. Recovery of the five flavonoids was between 91.5 and 103.6%, with RSD less than 6.5%. The method was successfully used for analysis of seven samples of Flos Inulae from different parts of China and was found to be simple and efficient.     

Rapid Determination of Creatinine in Human Urine by Microchip Electrophoresis with LED Induced Fluorescence Detection

In clinical medicine, urine creatinine concentration is an important marker in the evaluation of renal function and muscular dysfunctions. Herein, we reported a novel method for rapid determination of creatinine in urine by microchip electrophoresis with light-emitting diode induced fluorescence detection. Creatinine was derivatized by fluorescein isothiocyanate, and then quantitatively detected by the developed microchip LED induced fluorescence detection system. The excitation and emission wavelengths were 490 and 523 nm, respectively. The urine samples were analyzed after centrifuge and filtration. A baseline separation was obtained in <30 s using 10 mM borate buffer (pH 9.0, containing 45 mM sodium dodecylsulfate), with separation voltage of 1.5 kV. Good linearity was obtained (r ² = 0.9978) in the concentration range of 10.0–2.00 × 10³ μM, and the limit of detection was 2.87 μM (S/N = 3). The recovery was 96.0–107 %, and the interday precision was <4.5 % (n = 6). To validate assay results, we compared the present method with the Jaffe’s colorimetric assay by measuring real urine samples. The method was reliable, sensitive, high-speed, low-cost and suitable for the routine analysis of creatinine in biofluids.

     

Sodium desoxycholate‐assisted capillary electrochromatography with methacrylate ester‐based monolithic column on fast separation and determination of coumarin analogs in Angelica dahurica extract

A rapid and sensitive CEC method with methacrylate ester‐based monolithic column has been developed for separation and determination of five coumarins (byakangelicin, oxypeucedanin hydrate, xanthotoxol, 5‐hydroxy‐8‐methoxypsoralen and bergapten) in Angelica dahurica extract. Surfactant sodium desoxycholate (SDC) was introduced into the mobile phase as the pseudostationary to dynamically increase the selectivity of analytes instead of increasing the hydrophobicity of stationary phase. In addition, other factors, pH of phosphate buffer, ACN content and applied voltage, for instance, have also an obvious effect on the resolution but little on the retention time. Satisfactory separation of these five coumarins was achieved within 6 min under a 30:70 v/v ACN–buffer containing 20 mM sodium dihydrogen phosphate (NaH₂PO₄) and 0.25 mM SDC at pH 2.51. The RSDs of intraday and interday for relative peak areas were less than 3.0% and 4.7%, respectively; and the recoveries were between 87.5% and 95.0%. The LODs were lower than 0.15 μg/mL and the LOQs were lower than 0.30 μg/mL, respectively, while calibration curves showed a good linearity (r² > 0.9979). Finally, five target coumarins from the crude extracts of A. dahurica were separated, purified, and concentrated by D‐101 macroporous resin, and were successfully separated and quantitatively determined within 6 min.     

Simultaneous Determination of Five Nonsteroidal Anti-Inflammatory Drugs and Two Glucocorticoids in Adulterated Traditional Herbal Medicines for the Treatment of Rheumatism

The adulteration of traditional herbal medicines (THMs) with synthetic drugs is prevalent and represents a serious risk for public health. A rapid and novel reversed-phase high-performance liquid chromatography (HPLC) method was established and validated for the simultaneous determination of five nonsteroidal anti-inflammatory drugs (NSAIDs) and two glucocorticoids in THMs for rheumatoid treatment. Glipizide was used as the internal standard (IS). The separation was completed on a C₁₈ column with a mobile phase consisting of methanol and a buffer solution containing 10 mM ammonium acetate and 0.1% formic acid with a gradient elution. All calibration curves showed good linear regression (r ² > 0.9996), and the recoveries of the seven analytes were in the range of 96.94%–105.37%. A liquid chromatography-mass spectrometry (LC-MS) method was developed to confirm the identity of the adulterants. The proposed method was applied to identify and determine the five NSAIDs and two glucocorticoids in THMs for rheumatism.     

Meropenem and ciprofloxacin in complicated gastric surgery for cancer patients: A simple SPE–UHPLC–PDA method for their determination in human plasma

A simple and rapid ultra‐high‐performance liquid chromatographic (UHPLC) for the simultaneous determination of meropenem and ciprofloxacin in human plasma was developed and validated. All of the analytes were separated in <5 min. A solid‐phase extraction method was applied from sample preparation. Analytical separation was performed on a Poroshell SB C₁₈ column (50 × 2.1 mm, 2.7 μm particle size) with photodiode array (PDA) detection. Meropenem and ciprofloxacin were determined at wavelengths of 300 and 277 nm, respectively. The mobile phase was a mixture of acetonitrile–10 mm ammonium acetate–methanol in gradient elution. The method has been validated for both drugs in gastric surgery for cancer patients. The method showed good linearity with correlation coefficients, r² = 0.994 for the two drugs, as well as high precision (RSD < 10.5% in each case); accuracy ranged from ?5.8 to +6.0%. The limit of quantitation of the two drugs was established at 0.02 and 0.01 μg/mL, respectively. Meropenem, ciprofloxacin and the internal standard were extracted from human plasma with a mean recovery ranging from 92.5 to 98.6%. The method was applied to quantify the drugs dosage in complicated gastric surgery patients.