Mobile Phase Composition For Separation Research Articles

Determination of aromatic amines in environmental water samples using solid-phase extraction modified with sodium dodecyl sulphate and micellar liquid chromatography

ABSTRACTExtraction and determination of seven aromatic amines in environmental water samples were performed with solid-phase extraction (SPE) and micellar liquid chromatography (MLC) using experimental design. Extraction of aromatic amines was carried out with a C18 cartridge modified with sodium dodecyl sulphate (SDS). The washing solution and elution solvent for extraction of aromatic amines were aqueous solution containing 5% (v/v) acetonitrile and 5% (v/v) acetone and 3 mL methanol, respectively. The chemometrics approach was applied for the separation optimisation of these compounds using MLC. Different mobile phase compositions were used for modelling based on retention times to obtain the best separation using central composite design. The optimum mobile phase composition for separation and determination of analytes in water samples was 69 mM SDS, 9% v/v 1-propanol and pH = 6.4. Recoveries were between 84.8–93.5% with relative standard deviation (RSD) less than 5.8% (n = 5). Limits of detection and linear range were 1–4.5 and 3.1–125.0 µg/L, respectively. The proposed method was applied to determine the aromatic amines in real samples (river and well waters). Amount of 4-nitroaniline and 3-nitroaniline in river water sample were 2.15 and 1.91 µg/L, respectively.

Separation optimization of aniline and seven 4‐substituted anilines in high‐submicellar liquid chromatography using empirical retention modeling and Derringer's desirability function

The separation optimization of aniline and seven 4-substituted derivatives in high-submicellar LC was performed using an interpretive optimization strategy and Derringer's desirability function. Description of the retention of solutes was carried out through several hyperbolic and logarithmic retention models using the retention data of five mobile phases of SDS (0.06-0.12 M) and methanol (50-70% v/v) at pH 3. Among the investigated models, a logarithmic retention model logk=c0+c1φ+c2[S]+c12φ[S]+d12(φ[S])0.5 showed the best prediction capability and was used to predict the solute retention factors. A grid search program was used to calculate the retention times of each solute, based on the best retention model, for all combinations of SDS and methanol concentrations in the factor space. Two different chromatographic goals, analysis time and retention differences between adjacent peaks, were evaluated simultaneously using Derringer's desirability function for each mobile phase conditions in the grid search. Optimal mobile phase composition for separation of eight anilines was found to be 0.119 M SDS and 53% v/v methanol. Under these conditions, full resolutions with a reasonable analysis time (22 min) were obtained. At the optimal condition, a good agreement was observed between predicted and experimental values of the retention times.

Multi-criteria decision making for simultaneous optimization of resolution and analysis time of aromatic diamines in high-submicellar liquid chromatography

Multi-criteria decision making was used to simultaneous optimization of resolution and analysis time of five aromatic diamines in high-submicellar liquid chromatography. The factors studied were the concentration of sodium dodecyl sulfate [SDS], and volume percentage of methanol. The experiments were performed according to a face-centered cube central composite design to map the chromatographic response surface. The chromatographic response functions (CRFs) were formed using two sigmoidal desirability functions and were considered as the responses of design. The sigmoidal functions were used to transform the optimization criteria, resolution and analysis time into the desirability values. The qualities of the obtained chromatograms in each experiment were evaluated using CRF. Then, multiple linear regression (MLR) was used to correlate the obtained CRFs to the experimental factors and their interactions. The obtained MLR model showed good descriptive and predictive ability (R2 = 0.9492 and F = 14.99). The optimum mobile phase composition for separation of interested aromatic diamines using a C18 column was 0.15 M SDS and 59 % (v/v) methanol. Proper resolutions with a reasonable analysis time were obtained under the optimum condition.

OPTIMIZATION OF SEPARATION OF FLAVONOIDS IN MICELLAR LIQUID CHROMATOGRAPHY USING EXPERIMENTAL DESIGN AND DERRINGER'S DESIRABILITY FUNCTION

Derringer's desirability function was used to simultaneous optimization of resolution and analysis time of five flavonoids myricetin, quercetin, hesperetin, naringenin, and apigenin in MLC. The factors studied were the concentration of sodium dodecyl sulfate [SDS], alkyl chain length of the alcohol (N), volume percentage of alcohol (Vm), volume percentage of acetic acid (AcOH) in mobile phase, and flow rate. The experiments were performed according to a face-centered cube half fractional central composite design to map the chromatographic response surface. The chromatographic response functions (CRFs) were formed using two sigmoidal desirability functions and were considered as the responses of design. The qualities of the obtained chromatograms in each experiment were calculated using CRF and model was built by the use of multiple linear regression (MLR) to correlate the obtained CRFs to the experimental factors and their interactions. The developed MLR model showed good descriptive and predictive ability (R2 = 0.9530 and F = 21.88). The optimum mobile phase composition for separation of interested flavonoids using a C18 column was [SDS] = 0.040 mol L−1; 11.2 % v/v butanol, 1.4 % v/v AcOH with flow rate of 1.1 mL/min. The efficiency of prediction of polynomial model was confirmed by performing the experiment under the predicted optimal conditions.

Separation optimization of quercetin, hesperetin and chrysin in honey by micellar liquid chromatography and experimental design

The chemometrics approach was applied for the separation optimization of flavonoid markers (quercetin, hesperetin and chrysin) in honey using micellar liquid chromatography (MLC). The investigated method combines SPE of flavonoids from honey using C(18) cartridge and their separation and quantification by micellar liquid chromatography. A two level full factorial design was carried out to evaluate the effect of four experimental factors including concentration of SDS, alkyl chain length of the alcohol used as the organic modifier (N), volume percentage of the organic modifier (V(m)) and volume percentage of acetic acid (AcOH) in mobile phase on analytes retention times. Experiments for analytes retention times modeling and optimization of separation were performed according to central composite design. Multiple linear regression method was used for the construction of the best model based on experimental retention times. Pareto optimal method was used to find suitable compatibility between resolution and analysis time of analytes in honey. The optimum mobile phase composition for separation and determination of analytes in honey were [SDS]=0.124 mol/L; 7.8% v/v ethanol and 5.0% v/v AcOH. Limits of detection and linear range of flavonoid markers were 0.0079-0.0126, 0.05-50.0 mg/L, respectively.

Optimization of mobile phase for separation of carbohydrates in honey by high performance liquid chromatography using a mixture design

A mixture design was used to optimize the mobile phase composition for separation of carbohydrates in honey by High Performance Liquid Chromatography. Nine ternary acetronitrile, water and ethyl acetate mobile phases corresponding to a simplex centroid design with axial points were test to separate those carbohydrates most frequently encountered in honey samples. The results suggest that a special cubic model accurately describes changes in the proportions of these solvents in the mobile phase close to the region of optimal peak separation. The addition of a third solvent, ethyl acetate, to binary mobile phase of water and acetonitrile permitted a significant improvement in carbohydrate separation that can be applied to the quantitative analysis of these compounds in honey.

Analysis of Dns-amino acids by liquid chromatography : I. Selection of optimum mobile phase composition for separation of Dns-amino acids on polyvinyl acetate gel

The separation of a mixture of ten Dns-amino acids (Dns-Gly, -Ala, -Val, -Leu, -Pro, -Hypro, -Met, -Ser, -Asn and -Gln) was carried out by liquid chromatography by using macroreticular polyvinyl acetate gel as a packing material. Different mobile phase systems were investigated, based mainly on mixtures of n-hexane with ethanol, methanol, chloroform, acetone, methyl ethyl ketone, ethyl acetate, dioxane and tetrahydrofuran. The solvent composition was fixed so as to elute all of the components of the sample mixture in a practical period of 2 h. Satisfactory separation of the ten components was obtained with the n-hexane-ethanol (90:10) system. The presence of methanol as a modifier in the n-hexane was effective in reducing the elution time, but the separation was not as satisfactory. Chloroform or dioxane was useful only for the separation of Ser, Asn and Gln. Acetone, methyl ethyl ketone, ethyl acetate and tetrahydrofuran were not suitable for practical separations of Dns-amino acids.