Unusual Temperature-Retention Dependences Observed for Several Benzodiazepines in RP-HPLC Using Different Mobile Phase Compositions

Galaon, Toma; Anghel, Dan F.; David, Víctor; Aboul‐Enein, Hassan Y.

doi:10.1007/s10337-013-2540-5

Cited by 12 publications

(12 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In several cases describing the deviation from linearity of the van't Hoff dependence reported by literature for other retention mechanisms this function showed an maximum point (i.e. an extreme point) situated on the studied temperature interval.…”

Section: Resultssupporting

confidence: 49%

“…Temperature may influence the retention of the analytes separated by HILIC and the chromatographic performances, mainly the peak shape and separation selectivity . The dependence of retention on the column temperature is generally represented by the linear van't Hoff function between the natural logarithm of the retention factor (ln k ) and the inverse value of absolute temperature of the studied column (1/T) :

ln k = - \frac{Δ H^{0}}{R \cdot T} + \frac{Δ S^{0}}{R} + ln φ

…”

Section: Introductionmentioning

confidence: 99%

“…, ΔH 0 is the standard enthalpy for the transfer of the analyte from mobile phase to the stationary phase, ΔS 0 is standard entropy for the same partition process, R is the universal gas constant (8.314 J K −1 mol −1 ), T is the absolute column temperature (namely t + 273.15, t being column temperature in Celsius degree) and ϕ represents the phase volume ratio (the volume of stationary phase to that of the mobile phase). According to this equation the dependence between ln k and 1/T should be linear, but in several circumstances a deviation from this linearity has been observed and explained by various factors that are either column dependent, or due to the complex processes occuring in the mobile phase, or due to the solute molecular characteristics , such as: ‐the phase ratio is not always constant over the temperature interval applied to the chromatographic column used in the retention study ; ‐the existence of secondary equilibria involving analytes, such as, for example, their structural modifications by temperature modification, which may influence their interactions with stationary phase or mobile phase components ; ‐the non‐linear variation of acidic properties of analytes (pK a ) with temperature variation . …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Variability of temperature dependences of the retention of strongly polar compounds under ZIC‐HILIC liquid chromatographic mechanism

Tănase

Bacalum

David

2019

Separation Science Plus

Self Cite

View full text Add to dashboard Cite

The retentions of 13 strongly polar compounds (aminocids; dipeptides, drugs, and other biologically active species) were studied for two SeQuant ZIC‐HILIC (Merck) stationary phases containing a zwitterionic sulfobetaine moiety covalently attached to porous silica (3.5 and 5 μm particle size). Methanol and acetonitrile were used as organic components in the mobile phase composition, whose aqueous phase consisted in buffers of various controled pH values based on acetate‐acetic acid. This study shows various dependences of the retention on the absolute column temperature, some being obeyed to van't Hoff dependence, while others not following this rule. The values of standard enthalpy for the transfer of the analyte from mobile phase to the stationary phase were calculated from linear van't Hoff plots, which were below 10 kJ/mol. From the polynomial regression applied to the experimental retention data that not obeyed to a linear fit, the value of absolute temperature was calculated that corresponds to a maximum retention for studied compounds.

show abstract

Section: Resultssupporting

confidence: 49%

ln k = - \frac{Δ H^{0}}{R \cdot T} + \frac{Δ S^{0}}{R} + ln φ

…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Variability of temperature dependences of the retention of strongly polar compounds under ZIC‐HILIC liquid chromatographic mechanism

Tănase

Bacalum

David

2019

Separation Science Plus

Self Cite

View full text Add to dashboard Cite

show abstract

“…Mobile phase flow-rate was modified between 0.2 and 0.4 mL/ min with a 0.05 increment. The final chosen value was 0.25 mL/min because it allowed both fast separation and good MS sensitivity of the analytes, keeping in mind that ESI ionization is more efficient at lower flow-rates [18].…”

Section: Resultsmentioning

confidence: 99%

Simultaneous Determination of alfa-, beta- and gama-hexabromocyclododecane Diastereoisomers in Sewage Sludge using Liquid Chromatography Tandem Mass Spectrometry

Chiriac¹,

Cruceru²,

Niculescu³

et al. 2017

Rev. Chim.

Self Cite

View full text Add to dashboard Cite

Hexabromocyclododecane (HBCD) is a large-scale usage brominated flame retardant consisting of a mixture of diastereoisomers which has been reported as an ubiquitous environmental contaminant. HBCD has attracted much attention due to its toxicity and increasing levels in waste water sewage sludge. Since November 2014, HBCD was added to the Persistent Organic Pollutants list of the Stockholm Convention which generated a higher concern regarding its presence in the environment. A rapid (8 min) and accurate liquid chromatography electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS) was developed to separate and detect a-, b- and g-HBCD isomers from sewage sludge. Optimization of LC-MS parameters (column temperature, mobile phase composition and flow, collision energy, fragmentor voltage, capillary voltage and drying gas temperature) allowed complete separation of the three isomers and also very good detection sensitivity with instrumental quantitation limits (IQLs) between 0.3 and 0.6 ng/mL. The three isomers were separated on a C18 reversed-phase column, kept at 18�C, using a H2O/ACN/MeOH mobile phase mixture and detected by negative electrospray ionization using MRM mode with two transitions, one for quantitation and one for confirmation. MS detector response was linear in the range 1.0 � 100.0 ng/mL with correlation coefficients (R2) higher than 0.99 for all three isomers. A simple ultrasonic assisted liquid-solid extraction procedure using a solvent mixture was employed to extract HBCD isomers from WWTP sewage sludge. Overall method intra-day and inter-day precision (RSD%) were situated between 7.6 � 9.2% and 10.3 � 14.5%, respectively. LOQs for a-, b- and g-HBCD were 1.4, 0.7 and 1.0 ng/g, comparable and even lower to those reported by similar studies concerning HBCD presence in WWTP sewage sludge. HBCD presence was tested from several WWTP sludge samples. All three isomers were found with 100% detection frequency ranging from 3 to 76 ng/g.

show abstract

“…Нетипичные температурные зави-симости параметров удерживания для некоторых аналитов в ОФ ВЭЖХ и возмож-ные причины их возникновения неоднократно обсуждались в литературе [12][13][14]. Обнаруженная нами инверсия параметров удерживания аналитов с различной лету-честью (ацетона и ДМФА) при изменении температуры (рис.…”

Section: обсуждение результатовunclassified

Влияние Температуры На Закономерности Удерживания Аналитов С Различной Летучестью В ОФ ВЭЖХ С Низким Содержанием Ацетонитрила В Элюенте

Овчинникова¹,

Родинков²

2018

sorpchrom

View full text Add to dashboard Cite

Исследованы закономерности удерживания аналитов с различной летучестью в условиях ОФ ВЭЖХ. Установлено, что независимо от летучести аналитов повышение температуры позволяет в несколько раз повысить эффективность хроматографического процесса, если скорость элюента доста-точно высока. Негативное влияние высокой летучести аналитов проявляется лишь при повышенной температуре и низкой скорости элюента в сочетании с низким содержанием в нем ацетонитрила. По-добное влияние может быть объяснено наличием стационарной газовой фазы в порах гидрофобного сорбента, не смачиваемого подобными элюентами.Ключевые слова: температура, ВЭТТ, закономерности удерживания, органические соедине-ния, влияние летучести, ОФ ВЭЖХ. The effect of temperature on the retention of analytes with different volatility in RP HPLC with a low content of acetonitrile in the eluentOvchinnikova O.K., Rodinkov O.V. Saint-Petersburg State University, Institute of Chemistry, St. PetersburgIt is known that an increase of temperature in RP HPLC can significantly improve the efficiency of the chromatographic process and reduce the content of the organic modifier in the eluent or even use pure water as the latter. However, an increase of the water content in the eluent, the wettability of the hydrophobic silica gel C18 inevitably deteriorates and, as a consequence, the formation of a stationary gas phase (SGP) in the pores of this sorbent occurs. Obviously, the existence of SGF, first of all, will influence the behavior of volatile analytes. The purpose of this work is to study the effect of temperature on the retention of analytes with different volatility at low acetonitrile levels in the eluent, taking into account the possible existence of a gas phase in the pores of the sorbent.Based on the results of the studies performed, it was established that an increase in temperature allows several times to reduce the value of HETP in RP HPLC, regardless of the volatility of the analytes. The negative influence of the high volatility of the analytes begins to appear only at high temperatures and a low rate of elution in the case of a low content of acetonitrile in it or its absence. Such an effect can be explained by the longitudinal diffusion of the analytes in the SGP located in the pores of the hydrophobic sorbent. The existence of SGP is confirmed by temperature dependences of retention parameters of analytes with different volatility: potassium nitrate, dimethylformamide, acetone and acetylene. An increase in temperature is accompanied by an improvement in the wettability of the hydrophobic octadecylsilicagel, an increase in the

show abstract

Unusual Temperature-Retention Dependences Observed for Several Benzodiazepines in RP-HPLC Using Different Mobile Phase Compositions

Cited by 12 publications

References 18 publications

Variability of temperature dependences of the retention of strongly polar compounds under ZIC‐HILIC liquid chromatographic mechanism

Variability of temperature dependences of the retention of strongly polar compounds under ZIC‐HILIC liquid chromatographic mechanism

Simultaneous Determination of alfa-, beta- and gama-hexabromocyclododecane Diastereoisomers in Sewage Sludge using Liquid Chromatography Tandem Mass Spectrometry

Влияние Температуры На Закономерности Удерживания Аналитов С Различной Летучестью В ОФ ВЭЖХ С Низким Содержанием Ацетонитрила В Элюенте

Contact Info

Product

Resources

About