Simultaneous determination of azelaic and benzoic acids in topical preparations by liquid chromatography

Summary An isocratic, reversed-phase liquid chromatographic (LC) method has been developed for the simultaneous determination of azelaic and benzoic acids in pharmaceutical creams. The compounds were separated on a C₁₈ column (4 μm particles); the mobile phase was methanolwater, 40∶60, containing 10mm ammonium acetate and with the pH adjusted to 5.0. Detection was performed at 220 nm. The method was validated for accuracy, linearity, precision, and selectivity. Recoveries at levels corresponding to 80% to 120% of the declared content of the creams ranged from 99.5 to 101.8% and from 100.4 to 102.1% for azelaic and benzoic acids, respectively. The calibration graphs were linear in the ranges 20–1400 μg mL⁻¹ for azelaic acid (correlation coefficient,r ₁>0.99999), and 0.1–7.0 μg mL⁻¹ for benzoic acid (r>0.99998).     

Determination of benzoic acid in milk by solid-phase extraction and ion chromatography with conductivity detection

A simple, fast, precise and eco-friendly method, based on ion chromatography (IC) with a suppressed conductivity detector, was proposed for the determination of benzoic acid (BA) inmilk in this paper. The chromatographic separation was accomplished by using an anion exchange column eluted with 3.2 μmol/L aqueous Na2CO3 and 1.0 mmol/L aqueous NaHCO3 at a flow-rate of 0.7 mL/min. Themethod validation experiment provided excellent results with respect to linearity (correlation coefficient up to 0.9997), limit of detection (0.1 μg/L), recovery values (ranging from 88.0% to 93.0%) and relative standard deviation (RSD) (below 2.2%, n = 7).     

Determination of gas-liquid partition coefficients by automatic equilibrium headspace-gas chromatography utilizing the phase ratio variation method

Summary The new phase ratio variation method is described which represents a convenient way for the determination of gas-liquid partition coefficients for practical purposes, utilizing equilibrium headspace-gas chromatography (EHS-GC). This method is based on the relationship between reciprocal peak area and the phase ratio in the vial containing the sample solution; it involves regression analysis of the EHS-GC measurements of a number of sample vials containing the same sample solution but with a wide variation of phase ratios. Examples are given for both aqueous systems and systems consisting of a stationary (liquid) phase used as the solvent; comparison of the measured values with results obtained by other methods shows satisfactory agreement. A critical discussion of the conditions influencing the accuracy of the analytical results is given.Symbols which specifically refer to gas chromatography (GC), to equilibrium headspace sampling (EHS) and to EHS-GC are marked by the corresponding acronym.     

食品中苯甲酸和山梨酸的气相色谱法分离分析

用毛细管气相色谱法对食品中的防腐剂苯甲酸和山梨酸进行了分离分析。样品用乙醚萃取，萃取物蒸发至干，残渣用氯仿溶解后直接进行色谱分析，FFAP石英毛细管柱，柱温220℃，邻苯二甲酸二甲酯为内标物。两种化合物在0.25mg/mL-4.00mg/mL范围内具有良好的线性关系。     

高效液相色谱法同时测定食品中安赛蜜、糖精、苯甲酸、山梨酸和咖啡因

用KromasilC1 8柱 ,以甲醇 :0 .5g/L柠檬酸铵 (42 5 :5 75 )为流动相 ,在波长 2 1 5nm ,柱温 40℃下测定了食品中的安赛蜜、糖精、苯甲酸、山梨酸和咖啡因。方法RSD 0 .6 2 %～ 1 48% ,回收率 1 0 0 .7%～ 1 0 3 % ,相关系数r>0 .9998;应用于可乐、汽水、果奶等测定。     

Porous polymers coated with stationary phases. Contribution of the support to retention behaviour in gas chromatography. Chromosorb 102 coated with ethofat 60/25, squalane and fractonitril VI. Calculation of the experimental partition constants

Summary Following previous work on the solute-stationary phase-adsorbent interaction phenomena associated with the use of Chromosorb 101 support in gas chromatography, the retention of different polarity compounds on columns of Ethofat, squalane and Fractonitril VI on Chromosorb 102 has been studied. The experimental partition coefficients in these three liquid phases have been compared with those ones obtained earlier on Chromosorb 101 and Chromosorb P. The values have been related to the geometry of the support surface and the different coating of the liquid phases by scanning electron microscopy.     

胆固醇基键合相-反相高效液相色谱法测定正辛醇/水分配系数

通过反相高效液相色谱法系统地考察了中性和弱酸性化合物在新型胆固醇基键合相色谱柱（Cholester柱）上的保留行为。以甲醇和乙腈为有机调节剂,建立了保留因子（k）与有机调节剂比例（φ）间的关系,并外推获取100%水相为流动相时的log k_w;同时进一步建立并验证了不同流动相下正辛醇/水分配系数的对数（log K_ow）和log k_φ（log k_w）间的模型,并预测了部分化合物的log K_ow。结果表明,使用Cholester柱测定log K_ow时,甲醇比乙腈更适合作为有机调节剂;对中性化合物和中性状态的酸性化合物,可以用任意甲醇比例下获取的log k_φ预测log K_ow;对存在离解的酸性化合物,依然用外推方式获取的log k_w预测log K_ow。将采用Cholester柱与文献中采用C₁₈柱、C₈柱建立的log K_ow-log k_φ模型进行对比,结果表明化合物与胆固醇基键合相存在特别的作用。     

Comparison of the performance of conventional, temperature-controlled, and ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction combined with high-performance liquid chromatography in analyzing pyrethroid pesticides in honey samples

This research paper presents a comparative study of the performance of conventional, ultrasound-assisted (UA), and temperature-controlled (TC) ionic liquid (IL) dispersive liquid-phase microextraction (IL-DLLME). Various parameters that affect extraction efficiency, such as type and volume of extraction and disperser solvent, centrifugation time, salt addition, effect of temperature on TC-IL-DLLME, and effect of sonication time on UA-IL-DLLME, were evaluated. UA-IL-DLLME was found to provide the best extraction efficiency. Under optimized conditions, great enrichment factors (506-515) and good recoveries (101.2-103.0%) were obtained by analyte extraction in real samples. The limit of detections (LODs) ranged from 0.21 to 0.38 μg L(-1). Good linearity was obtained in the range of 0.5-200 μg L(-1) for ethofenprox and tetramethrin, and 1-200 μg L(-1) for meperfluthrin and alpha-cypermethrin. Based on optimized conditions, the UA-IL-DLLME method was applied and combined with high-performance liquid chromatography with diode array detection (HPLC-DAD) to determine the presence of ethofenprox, tetramethrin, meperfluthrin, and alpha-cypermethrin in honey samples.     

Solubility of benzoic acid in acetone, 2-propanol,acetic acid and cyclohexane: Experimental measurement and thermodynamic modeling

In this study the solubility of benzoic acid in acetone, 2-propanol, acetic acid and cyclohexane was experimentally determined over the temperature range of (277–346) K at around 5 K intervals by employing a gravimetric method. The experimental results showed that acetone had the best solubility for benzoic acid followed by 2-propanol, acetic acid and cyclohexane and the solubility in acetic acid had the strongest positive temperature dependency. The newly measured solubility data was also compared with the available literature data. Several commonly used thermodynamic models, including the empirical Van’t Hoff equation, the λh equation, the Wilson, NRTL and UNIQUAC equations, were applied to correlate the experimental solubility data. The adjustable parameters for each model were optimized by fitting the solubility data measured in this work. It was found that the three-parameter NRTL equation could give the best correlation results. Better predictions of the solubility of benzoic acid in acetic acid at higher temperature were observed using the Wilson and UNIQUAC equations than the other three equations which all gave underestimations.     

Determination of partition coefficient and analysis of nitrophenols by three‐phase liquid‐phase microextraction coupled with capillary electrophoresis

A three‐phase hollow fiber liquid‐phase microextraction method coupled with CE was developed and used for the determination of partition coefficients and analysis of selected nitrophenols in water samples. The selected nitrophenols were extracted from 14 mL of aqueous solution (donor solution) with the pH adjusted to pH 3 into an organic phase (1‐octanol) immobilized in the pores of the hollow fiber and finally backextracted into 40.0 μL of the acceptor phase (NaOH) at pH 12.0 located inside the lumen of the hollow fiber. The extractions were carried out under the following optimum conditions: donor solution, 0.05 M H₃PO₄, pH 3.0; organic solvent, 1‐octanol; acceptor solution, 40 μL of 0.1 M NaOH, pH 12.0; agitation rate, 1050 rpm; extraction time, 15 min. Under optimized conditions, the calibration curves for the analytes were linear in the range of 0.05–0.30 mg/L with r²>0.9900 and LODs were in the range of 0.01–0.04 mg/L with RSDs of 1.25–2.32%. Excellent enrichment factors of up to 398‐folds were obtained. It was found that the partition coefficient (K_a/d) values were high for 2‐nitrophenol, 3‐nitrophenol, 4‐nitrophenol, 2,4‐dinitrophenol and 2,6‐dinitrophenol and that the individual partition coefficients (K_org/d and K_a/org) promoted efficient simultaneous extraction from the donor through the organic phase and further into the acceptor phase. The developed method was successfully applied for the analysis of water samples.     

高效液相色谱法分离和测定酒石酸和马来酸

１引言 酒石酸（２,３一二羟基丁二酸）和马来酸（顺丁烯二酸）都是重要的有机化工原料,它们被广泛地应用于有机合成和其它化工生产领域［１］． 酒石酸的制备常用钨酸作为催化剂,由马来酸识水溶液与过氧化氢进行环氧化反应再经水解精制而成,其中常含有微量的没有反应的马来酸,因此,建立有效的分离和测定酒石酸和马来酸的方法,对于酒石酸生产条件的选择与控制,以及产品的质量检测等都有十分重要的意义． 目前尚未发现有关同时分离和测定酒石酸和马来酸的文献报道．我们首次采用反相高效液相色谱法,跟踪监测了酒石酸生产过程中的物…     

短分离柱胶束液相色谱法同时测定酱油和食醋中的苯甲酸和山梨酸

建立了胶束液相色谱同时测定酱油和食醋中苯甲酸和山梨酸的检测方法。样品经过简单的稀释和过滤后直接注入高效液相色谱仪进行分析。分析柱使用两根串联的色谱保护柱(Zorbax Extend-C₁₈ 柱, 12.5 mm×4.6 mm, 5 μm),胶束流动相为含有2%(体积分数)异丙醇的0.01 mol/L十二烷基硫酸钠-0.01 mol/L醋酸钠(pH 4.9),检测器为二极管阵列检测器,检测波长为235 nm。苯甲酸和山梨酸在3.5 min内完全分离。检测的线性范围为10~100 μ g/mL,相关系数(r)为0.9999。检出限(S/N=3)和定量限(S/N=10)分别为0.04和0.14 μ g/mL。批间和批内精密度均不高于5.2%,高、中、低3个水平的加标回收率为90.5%~103.8%。该方法简单、快速,适用于食品质量监测的日常检测。     

High pressure vapor–liquid equilibrium measurements of carbon dioxide with naphthalene and benzoic acid

High pressure vapor–liquid equilibrium data for binary systems of carbon dioxide with naphthalene and benzoic acid were measured at three different temperatures for each system. Experimental temperatures and pressures ranged from 373 to 458 K and 0 to 22 MPa, respectively. Dew points were also measured for naphthalene in the CO₂ rich region. The data measured provides valuable solubility information and is used to derive gas–solvent group interaction parameters for the predictive Soave–Redlich–Kwong equation of state.     

A linear relationship between partition ratio and composition of a binary mobile phase in reversed-phase liquid chromatography using chemically bonded stationary phases

A simple linear relationship which enables the effect of the composition of a binary mobile phase on the retention of a solute to be assessed in reverse phase liquid chromatography using a bonded stationary phase has been derived. The equations have been tested using published experimental data.     

Degradation of benzoic acid and its derivatives in subcritical water

In this research, the stability of benzoic acid and three of its derivatives (anthranilic acid, salicylic acid, and syringic acid) under subcritical water conditions was investigated. The stability studies were carried out at temperatures ranging from 50 to 350 °C with heating times of 10–630 min. The degradation of the benzoic acid derivatives increased with rising temperature and the acids became less stable with longer heating time. The three benzoic acid derivatives showed very mild degradation at 150 °C. Severe degradation of benzoic acid derivatives was observed at 200 °C while their complete degradation occurred at 250 °C. However, benzoic acid remained stable at temperatures up to 300 °C. The degradation products of benzoic acid and the three derivatives were identified and quantified by HPLC and confirmed by GC/MS. Anthranilic acid, salicylic acid, syringic acid, and benzoic acid in high-temperature water underwent decarboxylation to form aniline, phenol, syringol, and benzene, respectively.     

Equilibrium and kinetic solid-phase microextraction determination of the partition coefficients between polychlorinated biphenyl congeners and dissolved humic acid

A conventional solid-phase microextraction (SPME) method combined with liquid–liquid extraction was applied under equilibrium and nonequilibrium conditions to determine the partition coefficients (K_doc) of 25 polychlorinated biphenyl congeners (PCBs) between Sigma–Aldrich humic acid (HA) and water. The values of log K_doc determined with equilibrium SPME were linearly correlated with the logarithm of the octanol–water partition coefficients (K_ow) for PCB congeners at log K_ow < ∼7.2, but the trends were disrupted for log K_ow from ∼7.2 to 8.18. In addition, short-term (5 min to 4 days) and long-term (5–44 days) uptake profiles of PCBs were established, from which a pseudo-equilibrium for sorption of PCBs was revealed at ∼4 days of extraction. To understand this phenomenon, the uptake profiles were fitted with two equations (one equation is often used for pure water samples and the other one is applicable for samples containing complex matrices) derived from a first-order kinetics model. Subsequently, K_doc values obtained through kinetic approaches were compared with those acquired from equilibrium SPME. The comparison of K_doc values indicated that the pseudo-equilibrium was caused by the slow desorption of PCBs from HA rather than the biphasic desorption mechanism.     

硅胶基质固定相离子对反相液相色谱法测定强离解化合物的正辛醇/水分配系数

反相液相色谱(RPLC)是测定正辛醇/水分配系数(log P)的有效方法,但由于缺少同类型模型化合物,RPLC在测定强离解化合物的log P时遇到挑战.该文在硅胶基质C18色谱柱上,采用离子抑制反相液相色谱(IS-RPLC)和离子对反相液相色谱(IP-RPLC)分别对中性化合物、酚酸、羧酸、磺酸及部分两性化合物的保留行...     

An efficient isolation and purification of broad partition coefficient range ginsenosides from roots of Panax quinquefolium L. by linear gradient counter-current chromatography coupled with preparative high-performance liquid chromatography

As a famous health food, roots of Panax quinquefolium L. possessed immune regulation and enhancement of the central nervous system, in which ginsenosides are the main active component with different numbers and positions of sugars, causing different chemical polarities with a challenge for the separation and isolation. In this study, a fast and effective bilinear gradient counter-current chromatography was proposed for preparative isolation ginsenosides with a broad partition coefficient range from roots of Panax quinquefolium L. In terms of the established method, the mobile phases comprising n-butanol and ethyl acetate were achieved by adjusting the proportion. Coupled with the preparative HPLC, eleven main ginsenosides were successfully separated, including ginsenoside Rg₁ ( 1 ), Re ( 2 ), acetyl ginsenoside Rg₁ ( 3 ), Rb₁ ( 4 ), Rc ( 5 ), Rg₂ ( 6 ), Rb₃ ( 7 ), quinquefolium R₁ ( 8 ), Rd ( 9 ), gypenoside X VII ( 10 ) and notoginsenoside Fd ( 11 ), with purities exceeding 95% according to the HPLC results. Tandem mass spectrometry and electrospray ionization mass spectrometry were adopted for recognizing the isolated compound architectures. Our study suggests that linear gradient counter-current chromatography effectively separates the broad partition coefficient range of ginsenosides compounds from the roots of Panax quinquefolium L. In addition, it can apply to active compound isolation from other complicated natural products.     

One‐step isolation of carnosic acid and carnosol from rosemary by centrifugal partition chromatography

Carnosic acid and carnosol are the main bioactive components responsible for the significant antioxidant activity of Rosmarinus officinalis . Nevertheless, they are known for their instability in solutions. Separation of both compounds from crude rosemary extract was successfully achieved by one‐step centrifugal partition chromatography without any degradation. A two‐phase solvent system, hexane/ethyl acetate/methanol/water (3:2:3:2 v/v) was run on a preparative scale applying the elution–extrusion technique in descending mode. A 900 mg quantity of the crude extract containing 39.7% carnosic acid and 12.3% carnosol was loaded onto a 500 mL column, rotating at 1800 rpm. Carnosic acid and carnosol were obtained at purities of 96.1 ± 1% and 94.4 ± 0.9%, with recoveries of 94.3 ± 4.4% and 94.8 ± 2.3%, respectively. The compounds were identified by mass spectrometry, tandem mass spectrometry, and comparison with authentic standards.