scholarly journals Thermodynamic and Extrathermodynamic Studies of Enantioseparation of Imidazolinone Herbicides on Chiralcel OJ Column

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Wenjian Lao
Keyword(s):  
High Performance Liquid Chromatography ◽  
Chiral Separation ◽  
Mobile Phase ◽  
High Performance ◽  
Chromatographic Peak ◽  
Chiral Column ◽  
Higher Temperature ◽  
Lower Temperature ◽  
The Moment ◽  
Imidazolinone Herbicides

A homologous series of chiral imidazolinone herbicide was previously resolved on Chiralcel OJ column in high performance liquid chromatography. However, the mechanism of the chiral separation remains unclear. In this study, chromatographic behaviors of five chiral imidazolinone herbicides were characterized by thermodynamic and extrathermodynamic methods in order to enhance the understanding of the chiral separation. Thermodynamic parameters of this study were derived from equilibrium constant () that was estimated from the moment analysis of the chromatographic peak. Van't Hoff plots of ( versus ) were linear at a range of 15–50°C, only nonlinear at a range of 5–15 °C with n-hexane (0.1%, trifluoroacetic acid)-2-propanol 60/40 (v/v) mobile phase. The enantiomer retention on the chiral column was entropy-driven at a lower temperature (5°C) and enthalpy-driven at a higher temperature (10 to 50°C). Enantioseparations of four of the five imidazolinone herbicides were enthalpy-driven, only entropy-driven for imazaquin. Enantioseparation mechanisms were different in between 5–10°C and 15–50°C probably due to the conformational change of the OJ phase. Enthalpy-entropy compensation showed similar mechanisms in retention and chiral separation for the five or enantiomers. Several extrathermodynamic relationships were able to be extracted to address additivity of group contribution.

scholarly journals Direct Enantiomeric Separation and Determination of Hexythiazox Enantiomers in Environment and Vegetable by Reverse-Phase High-Performance Liquid Chromatography

2020 ◽  
Vol 17 (10) ◽  
pp. 3453
Author(s):  
Ping Zhang ◽  
Sheng Wang ◽  
Dongmei Shi ◽  
Yangyang Xu ◽  
Furong Yang ◽  
...  
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Mobile Phase ◽  
High Performance ◽  
Enantiomeric Separation ◽  
Reverse Phase ◽  
Column Temperature ◽  
Resolution Factor ◽  
Phase Temperature ◽  
Lower Temperature

In the present study, the direct enantiomeric separation of hexythiazox enantiomers on Lux cellulose-1, Lux cellulose-2, Lux cellulose-3, Lux cellulose-4, Lux amylose-1 and Chirapak IC chiral columns were carefully investigated by reverse-phase high-performance liquid chromatography (RP-HPLC). Acetonitrile/water and methanol/water were used as mobile phase at a flow rate of 0.8 mL·min−1. The effects of chiral stationary phase, temperature, thermodynamic parameters, mobile phase component and mobile phase ratio on hexythiazox enantiomers separation were fully evaluated. Hexythiazox enantiomers received a baseline separation on the Lux cellulose-3 column with a maximum resolution of Rs = 2.09 (methanol/water) and Rs = 2.74 (acetonitrile/water), respectively. Partial separations were achieved on other five chiral columns. Furthermore, Lux amylose-1 and Chirapak IC had no separation ability for hexythiazox enantiomers when methanol/water was used as mobile phase. Temperature study indicated that the capacity factor (k) and resolution factor (Rs) decreased with column temperature increasing from 10 °C to 40 °C. The enthalpy (ΔH) and entropy (ΔS) involved in hexythiazox separation were also calculated and demonstrated the lower temperature contributed to better separation resolution. Moreover, the residue analytical method for hexythiazox enantiomers in the environment (soil and water) and vegetable (cucumber, cabbage and tomato) were also established with reliable accuracy and precision under reverse-phase HPLC condition. Such results provided a baseline separation method for hexythiazox enantiomers under reverse-phase conditions and contributed to an environmental and health risk assessment of hexythiazox at enantiomer level.

scholarly journals Chiral Separation and Determination of Etoxazole Enantiomers in Vegetables by Normal-Phase and Reverse-Phase High Performance Liquid Chromatography

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3134
Author(s):  
Ping Zhang ◽  
Yuhan He ◽  
Sheng Wang ◽  
Dongmei Shi ◽  
Yangyang Xu ◽  
...  
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Chiral Separation ◽  
Mobile Phase ◽  
High Performance ◽  
Normal Phase ◽  
Reverse Phase Hplc ◽  
Reverse Phase ◽  
Normal Phase Hplc ◽  
Chiralpak Ic

The chiral separation of etoxazole enantiomers on Lux Cellulose-1, Lux Cellulose-3, Chiralpak IC, and Chiralpak AD chiral columns was carefully investigated by normal-phase high performance liquid chromatography and reverse-phase high performance liquid chromatography (HPLC). Hexane/isopropanol, hexane/n-butanol, methanol/water, and acetonitrile/water were used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase component, mobile phase ratio, and temperature on etoxazole separation were also studied. Etoxazole enantiomers were baseline separated on Lux Cellulose-1, Chiralpak IC, and Chiralpak AD chiral columns, and partially separated on Lux Cellulose-3 chiral column under normal-phase HPLC. However, the complete separation on Lux Cellulose-1, Chiralpak IC, and partial separation on Chiralpak AD were obtained under reverse-phase HPLC. Normal-phase HPLC presented better resolution for etoxazole enantiomers than reverse-phase HPLC. Thermodynamic parameters, including ΔH and ΔS, were also calculated based on column temperature changes from 10 °C to 40 °C, and the maximum resolutions (Rs) were not always acquired at the lowest temperature. Furthermore, the optimized method was successfully applied to determine etoxazole enantiomers in cucumber, cabbage, tomato, and soil. The results of chiral separation efficiency of etoxazole enantiomers under normal-phase and reverse-phase HPLC were compared, and contribute to the comprehensive environmental risk assessment of etoxazole at the enantiomer level.

Analysis of organic impurities of besifloxacin hydrochloride by high performance liquid chromatography with isocratic and gradient elution.

2019 ◽  
Vol 16 ◽  
Author(s):  
Joanna Wittckind Manoel ◽  
Camila Ferrazza Alves Giordani ◽  
Livia Maronesi Bueno ◽  
Sarah Chagas Campanharo ◽  
Elfrides Eva Sherman Schapoval ◽  
...  
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Mobile Phase ◽  
High Performance ◽  
Gradient Elution ◽  
Pharmaceutical Product ◽  
Raw Material ◽  
Isocratic Elution ◽  
Organic Impurities ◽  
Elution Method

Introduction: Impurity analysis is an important step in the quality control of pharmaceutical ingredients and final product. Impurities can arise from drug synthesis or excipients and even at small concentrations may affect product efficacy and safety. In this work two methods using high performance liquid chromatography (HPLC) were developed and validated for the evaluation of besifloxacin and its impurity synthesis, with isocratic elution and another with gradient elution. Method: The analysis by HPLC in isocratic elution mode was performed using a cyano column maintained at 25 °C. The mobile phase was composed by 0.5% triethylamine (pH 3.0): acetonitrile (88:12 v/v) eluted at a flow rate of 1.0 ml/min with detection at 330 nm. The gradient elution method was carried out with the same column and mobile phase components only modifying the rate between organic and aqueous phase during analysis. The procedures have been validated according to internationally accepted guidelines, observing results within acceptable limits. Results: The methods presented were found to be linear in the 140 to 260 µg/ml range for besifloxacin and 0.3 to 2.3 µg/ml for an impurity named A. The limits of detection and quantification were respectively 0.07 and 0.3 µg/ml for impurity A, with a 20 µL injection volume. The precision achieved for all analyses performed provided RSD inter-day equal to 6.47 and 6.36% for impurity A with isocratic elution and gradient, respectively. The accuracy was higher than 99% and robustness exhibited satisfactory results. In the isocratic method an analysis time of 25 min and 15 min was obtained for gradient. For impurity A, the number of theoretical plates in the isocratic mode was about 5000 while in the gradient mode it was about 45000, hence, it made the column more efficient by changing the mobile phase composition during elution. In besifloxacin raw material and in pharmaceutical product used in this study, other related impurities were present but but impurity A was searched for and not detected Conclusion: The proposed methods can be applied for quantitative determination of impurities in the analysis of the besifloxacin raw material, as well as in ophthalmic suspension of the drug, considering the quantitation limit.

Separation and Determination of Some Aromatic Sulfones by Reversed-Phase High-Performance Liquid Chromatography

1994 ◽  
Vol 59 (3) ◽  
pp. 569-574 ◽  
Author(s):  
Josef Královský ◽  
Marta Kalhousová ◽  
Petr Šlosar
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Mobile Phase ◽  
High Performance ◽  
Reversed Phase ◽  
Uv Spectra ◽  
Optimum Conditions ◽  
Linear Calibration ◽  
Technical Grade

The reversed-phase high-performance liquid chromatography of some selected, industrially important aromatic sulfones has been investigated. The chromatographic behaviour of three groups of aromatic sulfones has been studied. The optimum conditions of separation and UV spectra of the sulfones and some of their hydroxy and benzyloxy derivatives are presented. The dependences of capacity factors vs methanol content in mobile phase are mentioned. The results obtained have been applied to the quantitative analysis of different technical-grade samples and isomer mixtures. For all the separation methods mentioned the concentration ranges of linear calibration curves have been determined.

4-Nitrophenol in 4-nitrophenyl phosphate, a substrate for alkaline phosphatase, as measured by paired-ion high-performance liquid chromatography.

1977 ◽  
Vol 23 (12) ◽  
pp. 2288-2291 ◽  
Author(s):  
P H Culbreth ◽  
I W Duncan ◽  
C A Burtis
Keyword(s):  
Alkaline Phosphatase ◽  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Flow Rate ◽  
Mobile Phase ◽  
High Performance ◽  
Reversed Phase ◽  
Nitrophenyl Phosphate ◽  
Phase Column ◽  
Reversed Phase Column

Abstract We used paired-ion high-performance liquid chromatography to determine the 4-nitrophenol content of 4-nitrophenyl phosphate, a substrate for alkaline phosphatase analysis. This was done on a reversed-phase column with a mobile phase of methanol/water, 45/55 by vol, containing 3 ml of tetrabutylammonium phosphate reagent per 200 ml of solvent. At a flow rate of 1 ml/min, 4-nitrophenol was eluted at 9 min and monitored at 404 nm; 4-nitrophenyl phosphate was eluted at 5 min and could be monitored at 311 nm. Samples of 4-nitrophenyl phosphate obtained from several sources contained 0.3 to 7.8 mole of 4-nitrophenol per mole of 4-nitrophenyl phosphate.

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