Derringer's Desirability Function Research Articles

Micellar Electrokinetic Chromatography (MEKC) with Multiresponse Chemometric Optimization for the Determination of Hydrochlorothiazide and Coformulated Antihypertensives in the Presence of Hydrochlorothiazide Major Impurity.

In this work, micellar electrokinetic chromatographic method was developed and optimized for the determination of hydrochlorothiazide (HCT) in the presence of irbesartan (IRB), bisoprolol (BISO) and HCT main impurity. Four factors affecting the separation-sodium dodecyl sulphate (SDS) concentration, buffer concentration, temperature and voltage-were studied. Optimization studies were performed with the aid of a central composite design with six central points. The optimal separation conditions were obtained by applying Derringer's desirability function, and the conditions were borate buffer 17 mM (pH = 9), SDS 5.2 mM, temperature 25°C and voltage 12 kV. HCT, IRB and BISO were successfully determined in their pure form and pharmaceutical formulations with separation in <8 min. Calibration curves (R > 0.999) were prepared and complete method validation was performed according to ICH guidelines. The results obtained were statistically compared with that of the official methods.

Development and validation of an HPTLC method for the simultaneous estimation of Clonazepam and Paroxetine hydrochloride using a DOE approach

The present study examines simultaneous multiple response optimization using Derringer's desirability function for the development of an HPTLC method to detect Clonazepam and Paroxetine hydrochloride in pharmaceutical dosage form. Central composite design (CCD) was used to optimize the chromatographic conditions for HPTLC. The independent variables used for the optimization were the n-butanol content in the mobile phase, the chamber saturation time and the distance travelled. HPTLC separation was performed on aluminium plates pre-coated with silica gel 60 F254 as the stationary phase using n-butanol:glacial acetic acid:water (9:2:0.5% v/v/v) as the mobile phase. Quantification was achieved based on a densitometric analysis of Clonazepam and Paroxetine hydrochloride over the concentration range of 40–240ng/band and 300–1800ng/band, respectively, at 288nm. The method yielded compact and well-resolved bands at Rf of 0.77±0.02 and 0.34±0.02 for Clonazepam and Paroxetine hydrochloride, respectively. The linear regression analysis for the calibration plots produced r2=0.9958 and r2=0.9989 for Clonazepam and Paroxetine hydrochloride, respectively. The precision, accuracy, robustness, specificity, limit of detection and limit of quantitation of the method were validated according to the ICH guidelines. The factors evaluated in the robustness test were determined to have an insignificant effect on the selected responses. The results indicate that the method is suitable for the routine quality control testing of marketed tablet formulations.

Application of multi‐objective fractional factorial design for ultra‐wideband antennas with uniform gain and high fidelity

An efficient design methodology is presented for developing ultra-wideband (UWB) antennas with uniform gain and high fidelity. The major challenge for designing UWB antennas is to simultaneously meet all the frequency-domain and time-domain performance criteria including good impedance matching throughout the operational frequencies, relatively uniform gain over the UWB, and high waveform fidelity on pulse-preserving capabilities. If the framework of Pareto-based evolutionary algorithms is adopted, it may require thousands of tests to find an optimum structure due to the blind-search feature. In this study, all the requirements of UWB antenna design can now be efficiently achieved by the proposed methodology, which integrates the processes of fractional factorial design of experiments and Derringer's desirability functions into a multi-objective optimisation technique. The detailed procedure and its capability are demonstrated by an UWB planar monopole antenna design which comprises nine design parameters. By performing merely 64 predefined simulations, the optimum antenna structure is determined with an excellent impedance matching by 2:1 voltage standing wave ratio and a relatively constant gain (2.48–5.04 dBi) over the frequency band of 3.1–10.6 GHz. Meanwhile, the time-domain distortion is greatly reduced in comparison with the reference design which simply optimises the characteristic of impedance matching.

Application of Sigmoidal Transformation Functions in Optimization of Micellar Liquid Chromatographic Separation of Six Quinolone Antibiotics.

A chemometrics approach has been used to optimize the separation of six quinolone compounds by micellar liquid chromatography (MLC). A Derringer's desirability function, a multicriteria decision-making (MCDM) method, was tested for evaluation of two different measures of chromatographic performance (resolution and analysis time). The effect of three experimental parameters on a chromatographic response function (CRF) expressed as a product of two sigmoidal desirability functions was investigated. The sigmoidal functions were used to transform the optimization criteria, resolution and analysis time into the desirability values. The factors studied were the concentration of sodium dodecyl sulfate, butanol content and pH of the mobile phase. The experiments were done according to the face-centered cube central composite design, and the calculated CRF values were fitted to a polynomial model to correlate the CRF values with the variables and their interactions. The developed regression model showed good descriptive and predictive ability (R(2) = 0.815, F = 6.919, SE = 0.038, [Formula: see text]) and used, by a grid search algorithm, to optimize the chromatographic conditions for the separation of the mixture. The efficiency of prediction of polynomial model was confirmed by performing the experiment under the optimal conditions.

Multiobjective optimization of complex antenna structures using response surface models

A very efficient multiobjective (MO) design technique for complex antenna structures involving a large number of design parameters is presented. This design technique, multiobjective-fractional factorial design (MO-FFD), is very different from conventional Pareto-based MO algorithms, which take a great deal of effort to balance the trade-off between all the design specifications. By performing one single combination of simulations, all the response surface models of design goals are simultaneously built, and Derringer's desirability functions are readily applied to these models so that the optimum structure is obtained. Compared to classical MO algorithms such as Strength Pareto Evolutionary Algorithm 2, nondominated sorting particle swarm optimizer, and cultural MO particle swarm optimization, MO-FFD yields more desirable performances yet the required number of simulations is reduced by 97%. This article thoroughly illustrates the mathematical development of MO-FFD, deriving a novel application of ultrawideband (UWB) antennas because of its MO optimization capability. More explicitly, MO-FFD overcomes all the design challenges of dual band-notched UWB antennas including desired impedance characteristics, enhanced fidelity factors, and uniform peak gains over the passband, which are what conventional Pareto-based algorithms cannot attain. The measured results show that all the performance criteria are met; especially, the time-domain signal distortion is minimized. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:62–71, 2016.

Development of an achiral supercritical fluid chromatography method with ultraviolet absorbance and mass spectrometric detection for impurity profiling of drug candidates. Part II. Selection of an orthogonal set of stationary phases

Impurity profiling of organic products that are synthesized as possible drug candidates requires complementary analytical methods to ensure that all impurities are identified. Supercritical fluid chromatography (SFC) is a very useful tool to achieve this objective, as an adequate selection of stationary phases can provide orthogonal separations so as to maximize the chances to see all impurities.In this series of papers, we have developed a method for achiral SFC-MS profiling of drug candidates, based on a selection of 160 analytes issued from Servier Research Laboratories.In the first part of this study, focusing on mobile phase selection, a gradient elution with carbon dioxide and methanol comprising 2% water and 20mM ammonium acetate proved to be the best in terms of chromatographic performance, while also providing good MS response [1].The objective of this second part was the selection of an orthogonal set of ultra-high performance stationary phases, that was carried out in two steps. Firstly, a reduced set of analytes (20) was used to screen 23 columns. The columns selected were all 1.7–2.5μm fully porous or 2.6–2.7μm superficially porous particles, with a variety of stationary phase chemistries. Derringer desirability functions were used to rank the columns according to retention window, column efficiency evaluated with peak width of selected analytes, and the proportion of analytes successfully eluted with good peak shapes. The columns providing the worst performances were thus eliminated and a shorter selection of columns (11) was obtained. Secondly, based on 160 tested analytes, the 11 columns were ranked again. The retention data obtained on these columns were then compared to define a reduced set of the best columns providing the greatest orthogonality, to maximize the chances to see all impurities within a limited number of runs. Two high-performance columns were thus selected: ACQUITY UPC2 HSS C18 SB and Nucleoshell HILIC.

Development of an achiral supercritical fluid chromatography method with ultraviolet absorbance and mass spectrometric detection for impurity profiling of drug candidates. Part I: Optimization of mobile phase composition

Supercritical fluid chromatography (SFC) is a very useful tool in the purpose of impurity profiling of drug candidates, as an adequate selection of stationary phases can provide orthogonal separations so as to maximize the chances to see all impurities. The purpose of the present work is to develop a method for chemical purity assessment. The first part, presented here, focuses on mobile phase selection to ensure adequate elution and detection of drug-like molecules, while the second part focuses on stationary phase selection for optimal separation and orthogonality.The use of additives in the carbon dioxide – solvent mobile phase in SFC is now commonplace, and enables in particular to increase the number of eluted compounds and to improve peak shapes. The objective of this first part was to test different additives (acids, bases, salts and water) for their chromatographic performance assessed in gradient elution with a diode-array detector, but also for the mass responses obtained with a single-quadrupole mass detector, equipped with an electrospray ionization source (Waters ACQUITY QDa).In this project, we used a selection of one hundred and sixty compounds issued from Servier Research Laboratories to screen a set of columns and additives in SFC with a Waters ACQUITY UPC2 system. The selected columns were all high-performance columns (1.7–1.8μm with totally porous particles or 2.6–2.7μm with superficially porous particles) with a variety of stationary phase chemistries.Initially, eight additives dissolved in the methanol co-solvent were tested on a UPC2 ACQUITY UPC2 HSS C18 SB column. A Derringer desirability function was used to classify the additives according to selected criteria: elution capability, peak shapes, UV baseline drift, and UV and mass responses (signal-to-noise ratios). Following these tests, the two best additives (ammonium acetate and ammonium hydroxide) were tested on a larger number of columns (10) where the two additives appeared to provide very comparable overall scores. However, ammonium acetate was selected for slightly better chromatographic quality.In a second step, we investigated the effects of ammonium acetate concentration (between 0 and 25mM in the methanol co-solvent) on retention and peak efficiency. Two types of silica supports were tested by working with ACQUITY UPC2 HSS C18 SB and BEH columns. 20mM ammonium acetate in methanol with 2% water was finally selected as the best co-solvent composition.

Multi-responses extraction optimization combined with high-performance liquid chromatography-diode array detection–electrospray ionization-tandem mass spectrometry and chemometrics techniques for the fingerprint analysis of Aloe barbadensis Miller

A quality control strategy using high-performance liquid chromatography-diode array detector–electrospray ionization-tandem mass spectrometry (HPLC-DAD–ESI-MS/MS) coupled with chemometrics analysis was proposed for Aloe barbadensis Miller. Firstly, the extraction conditions including methanol concentration, extraction time and solvent-to-material ratio were optimized by multi-responses optimization based on response surface methodology (RSM). The optimum conditions were achieved by Derringer's desirability function and experimental validation implied that the established model exhibited favorable prediction ability. Then, HPLC fingerprint consisting of 27 common peaks was developed among 15 batches of A. barbadensis samples. 25 common peaks were identified using HPLC-DAD–ESI-MS/MS method by their spectral characteristics or comparison with the authentic standards. Chemometrics techniques including similarity analysis (SA), principal components analysis (PCA) and hierarchical clustering analysis (HCA) were implemented to classify A. barbadensis samples. The results demonstrated that all A. barbadensis samples shared similar chromatographic patterns as well as differences. These achievements provided an effective, reliable and comprehensive quality control method for A. barbadensis.

Quality of medicines commonly used in the treatment of soil transmitted helminths and giardia in ethiopia: a nationwide survey.

BackgroundThe presence of poor quality medicines in the market is a global threat on public health, especially in developing countries. Therefore, we assessed the quality of two commonly used anthelminthic drugs [mebendazole (MEB) and albendazole (ALB)] and one antiprotozoal drug [tinidazole (TNZ)] in Ethiopia.Methods/Principal FindingsA multilevel stratified random sampling, with as strata the different levels of supply chain system in Ethiopia, geographic areas and government/privately owned medicines outlets, was used to collect the drug samples using mystery shoppers. The three drugs (106 samples) were collected from 38 drug outlets (government/privately owned) in 7 major cities in Ethiopia between January and March 2012. All samples underwent visual and physical inspection for labeling and packaging before physico-chemical quality testing and evaluated based on individual monographs in Pharmacopoeias for identification, assay/content, dosage uniformity, dissolution, disintegration and friability. In addition, quality risk was analyzed using failure mode effect analysis (FMEA) and a risk priority number (RPN) was assigned to each quality attribute. A clinically rationalized desirability function was applied in quantification of the overall quality of each medicine. Overall, 45.3% (48/106) of the tested samples were substandard, i.e. not meeting the pharmacopoeial quality specifications claimed by their manufacturers. Assay was the quality attribute most often out-of-specification, with 29.2% (31/106) failure of the total samples. The highest failure was observed for MEB (19/42, 45.2%), followed by TNZ (10/39, 25.6%) and ALB (2/25, 8.0%). The risk analysis showed that assay (RPN = 512) is the most critical quality attribute, followed by dissolution (RPN = 336). Based on Derringer's desirability function, samples were classified into excellent (14/106,13%), good (24/106, 23%), acceptable (38/106, 36%%), low (29/106, 27%) and bad (1/106,1%) quality.Conclusions/SignificanceThis study evidenced that there is a relatively high prevalence of poor quality MEB, ALB and TNZ in Ethiopia: up to 45% if pharmacopoeial acceptance criteria are used in the traditional, dichotomous approach, and 28% if the new risk-based desirability approach was applied. The study identified assay as the most critical quality attributes. The country of origin was the most significant factor determining poor quality status of the investigated medicines in Ethiopia.

Second-order calibration for simultaneous determination of pharmaceuticals in water samples by solid-phase extraction and fast high-performance liquid chromatography with diode array detector

A fast high-performance liquid chromatography–diode array detection (HPLC–DAD) approach combined to solid phase extraction (SPE) as a pre-concentration step is developed for simultaneous determination of five selected pharmaceuticals (carbamazepine, naproxen, diclofenac, gemfibrozil and mefenamic acid) in water samples. The effective factors on the efficiency of SPE procedure are optimized using faced-centered central composite design (FCCD). In addition, multi-response optimization by using Derringer's desirability function is used to find the optimum experimental conditions for extraction of analytes from well and river waters. Due to the complexity of water matrices and the presence of different chromatographic issues, new combination of multivariate curve resolution–correlation optimized warping to parallel factor analysis (MCR–COW–PARAFAC) and multivariate curve resolution-alternating least squares with trilinearity constraint (MCR–COW–MCRtril) is proposed for simultaneous determination of five target pharmaceuticals in these samples. This strategy allowed us to overcome matrix effects and to exploit second-order advantage. Recoveries ranging from 80.12% to 102.71% and relative standard deviations below 8.0% for all pharmaceuticals proved the accuracy and precision of the proposed method. In addition, the values of relative error in calibration curves (RE, %) were below 11.24% and 12.19% for MCR–COW–PARAFAC and MCR–COW–MCR, respectively. Furthermore, the values of detection limits (LODs) and quantification limits (LOQs) were between 0.02 to 0.32ngmL−1 and 0.07 to 1.07ngmL−1, respectively. In addition, analytical figures of merit using multivariate approaches were calculated for both methods. In this regard, the values of sensitivity, LOD and LOQ showed an improvement compared to univariate techniques. Inspection of the results showed that due to the efficient correction of elution time shifts using MCR–COW method and preserving trilinear data structure, both MCR–COW–PARAFAC and MCR–COW–MCRtril give similar results. These results confirmed that coupling optimized SPE–HPLC–DAD method with second-order calibration algorithms can be considered as an efficient method for fast, simple and cost effective quantification of pharmaceuticals in highly contaminated samples, such as river and well waters.

Co-Producing Active Carbons and Sodium Silicate from Pyrolyzed Rice Husk by CO&lt;sub&gt;2&lt;/sub&gt; Activation Coupled with NaOH Solution Boiling

Active carbon and sodium silicate were produced simultaneously from pyrolyzed rice husk (PRH) by CO2 activation coupled with NaOH solution boiling. Doehlert matrix and Derringer's desirability function were applied to optimizing the boiling conditions to achieve a large specific surface area, a high silica extraction and low alkali consumption. In terms of this purpose, the optimum condition was determined as boiling CO2-activated char with 1mol/L NaOH solution at a liquid/solid ratio of 9.7 mL/g. Under this condition, the modulus of the sodium silicate and the specific surface area (SSA) of the active carbon were 2.62 and 897 m2/g, respectively. The values both reached their respective commercial levels. The pretreatment of the PRH with CO2 activation can markedly increase the SSA of active carbons.

Constrained Online Optimization Using Evolutionary Operation: A Case Study About Energy‐Optimal Robot Control

Optimization of full‐scale processes during regular production is a challenge that is often encountered in practice, requiring specialized approaches that only introduce small perturbations so that production does not need to be interrupted. Based on a case study, we discuss the potential of Evolutionary Operation (EVOP) derived methods. The case study relates to a badminton robot that has to perform point‐to‐point motions during a fixed time interval, based on two operation modes: time‐optimal motion, which ensures maximum precision but highest energy consumption, and energy‐optimal motion, which decreases the energy consumption, but as a trade‐off also lowers the precision. The current standard mode of operation is the energy‐optimal mode that is constructed from off‐line optimization on simulations. An online EVOP steepest ascent optimization to further reduce the energy consumption by fine‐tuning the implemented energy‐optimal mode was implemented. The constrained nature of the problem, where energy needs to be minimized subject to a time constraint, was transformed to an unconstrained single‐objective optimization using Derringer desirability functions. Two important contributions were made: (i) the online optimization of the energy‐optimal motion lowered the energy consumption by 4.7% while keeping the precision constant and (ii) the more stringent time‐constraints implemented in desirability functions lead to an operation mode with maximum precision and 51.7% less energy consumption than the current time‐optimal motion. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Computer-assisted electrochemical fabrication of a highly selective and sensitive amperometric nitrite sensor based on surface decoration of electrochemically reduced graphene oxide nanosheets with CoNi bimetallic alloy nanoparticles

For the first time, a novel, robust and very attractive statistical experimental design (ED) using minimum-run equireplicated resolution IV factorial design (Min-Run Res IV FD) coupled with face centered central composite design (FCCCD) and Derringer's desirability function (DF) was developed to fabricate a highly selective and sensitive amperometric nitrite sensor based on electrodeposition of CoNi bimetallic alloy nanoparticles (NPs) on electrochemically reduced graphene oxide (ERGO) nanosheets. The modifications were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), energy dispersive X-ray spectroscopic (EDS), scanning electron microscopy (SEM) techniques. The CoNi bimetallic alloy NPs were characterized using digital image processing (DIP) for particle counting (density estimation) and average diameter measurement. Under the identified optimal conditions, the novel sensor detects nitrite in concentration ranges of 0.1–30.0μM and 30.0–330.0μM with a limit of detection (LOD) of 0.05μM. This sensor selectively detects nitrite even in the presence of high concentration of common ions and biological interferents therefore, we found that the sensor is highly selective. The sensor also demonstrated an excellent operational stability and good antifouling properties. The proposed sensor was used to the determination of nitrite in several foodstuff and water samples.

Simultaneous determination of benzothiazoles, benzotriazoles and benzosulfonamides by solid phase microextraction-gas chromatography-triple quadrupole mass spectrometry in environmental aqueous matrices and human urine

This work proposes a new approach for the simultaneous determination of benzothiazoles, benzotriazoles and benzosulfonamides in different environmental matrices and human urine, using solid-phase microextraction coupled with gas-chromatography–triple quadrupole mass spectrometry (SPME-GC–QqQMS). The analytes object of this investigation have been classified as toxic to aquatic organisms and their presence in human urine was reported to occur as result of human exposure to contaminated environment. In this work many of the challenges related to the chemical diversity and polarity of the analytes selected were overcame conducting a multivariate optimization of the working conditions by using the approach of “Experimental design”. Tests performed to assess the performances of five SPME coatings in direct immersion mode revealed the polyacrylate coating to be the most suitable for the extraction of the probe analytes. A central composite design (CCD) was employed to determine the optimal conditions for four factors affecting the solid-phase microextraction process: extraction time, extraction temperature, pH and percentage of sodium chloride. The optimal working condition determined by using Derringer's desirability function were 40min as extraction time, pH 7.1 and 6.0% of NaCl. Since the extraction temperature do not significantly affects the responses for all the analytes considered, analyses were performed at room temperature. A careful evaluation of the matrix effect for all the matrices tested was carried out. The results obtained showed that the proposed method did not significantly influenced by matrix effects in most of the cases tested, and thus allows the use of simplified calibration procedure. Satisfactory values of accuracy and precision were also obtained for all the matrices considered.

Multi-responses extraction optimization based on response surface methodology combined with polarity switching HPLC–MS/MS for the simultaneous quantitation of 11 compounds in Cortex Fraxini: Application to four species of Cortex Fraxini and its 3 confusable species

A novel polarity switching high performance liquid chromatography–electrospray ionization tandem mass spectrometry (HPLC–ESI-MS/MS) approach combining optimization of extraction condition by response surface methodology (RSM) was developed for the simultaneous quantitative analysis of 11 compounds in Cortex Fraxini, a commonly used traditional Chinese medicine. The ultrasonic extraction conditions of the 11 analytes including sample quantity, methanol concentration and extraction time were simultaneously optimized with a Box–Behnken design (BBD) and Derringer's desirability function. Multiple-reaction monitoring (MRM) scanning was employed for quantification with switching electrospray ion source polarity between positive and negative modes in a single run of 16min. Quantitative parameters of the proposed method with respect to limit of detection (LOD), limit of quantification (LOQ), linearity, precision, accuracy and stability were evaluated under optimum conditions, and the results indicated that the method was sensitive, specific and reliable. The developed method was successfully applied to determine the investigated compounds in four species of Cortex Fraxini and three kinds of its confusable species, and significant differences were found between the official and confusable species.

Adsorption of basic red 9 on activated waste Gossypium hirsutum seeds: Process modeling, analysis and optimization using statistical design

Sulfuric acid activated immature Gossypium hirsutum seed was utilized as adsorbent for the batch adsorption of basic red 9. The main and interactive effects of five process factors like, adsorbent dose, initial dye concentration, contact time, pH and temperature were investigated to select the influencing key factors via 25 two-level full factorial design. Box–Behnken statistical design with the selected key factors employed for process optimization. The simultaneous optimization by Derringer's desirability function indicated that 54.27% removal of BR9 could be possible at the optimal conditions. Isotherm and kinetic studies confirmed the chemisorption on homogeneous and heterogeneous patches.

MODEL DEVELOPMENT AND PROCESS OPTIMIZATION FOR SOLVENT EXTRACTION OF POLYPHENOLS FROM RED GRAPES USING BOX–BEHNKEN DESIGN

The objective of the present study is to find out the optimum extraction conditions for extraction of polyphenols from red grapes using Box–Behnken design. Red grapes polyphenols were extracted using acid–ethanol solvent at various extraction temperature (40–60°C), extraction time (20–100 min) and different solid–liquid ratio (1:5–1:15 g:ml). The effect (main and interactive) of extraction conditions on total anthocyanin, phenolic and flavonoid content were studied using Box–Behnken design (three factors at three levels). The results showed that the contribution of the quadratic model was significant for all the responses. Second-order mathematical regression models were developed and were found to fit well with observed data. Derringer's desirability function methodology was performed to find out the optimal conditions based on both individual and combinations of all responses (extraction temperature: 57°C, time: 61 min, and solid–liquid ratio: 1:8.7 g:ml) were established. At this optimal condition, the anthocyanin yield, total phenolic and flavonoid content were 73.92 mg/100 g, 221.4 mg GAE/100 g, and 79.08 mg CE/100 g, respectively. A desirability value of 0.902 was achieved at this point.

Derringer desirability and kinetic plot LC-column comparison approach for MS-compatible lipopeptide analysis

Lipopeptides are currently re-emerging as an interesting subgroup in the peptide research field, having historical applications as antibacterial and antifungal agents and new potential applications as antiviral, antitumor, immune-modulating and cell-penetrating compounds. However, due to their specific structure, chromatographic analysis often requires special buffer systems or the use of trifluoroacetic acid, limiting mass spectrometry detection. Therefore, we used a traditional aqueous/acetonitrile based gradient system, containing 0.1% (m/v) formic acid, to separate four pharmaceutically relevant lipopeptides (polymyxin B1, caspofungin, daptomycin and gramicidin A1), which were selected based upon hierarchical cluster analysis (HCA) and principal component analysis (PCA).In total, the performance of four different C18 columns, including one UPLC column, were evaluated using two parallel approaches. First, a Derringer desirability function was used, whereby six single and multiple chromatographic response values were rescaled into one overall D-value per column. Using this approach, the YMC Pack Pro C18 column was ranked as the best column for general MS-compatible lipopeptide separation. Secondly, the kinetic plot approach was used to compare the different columns at different flow rate ranges. As the optimal kinetic column performance is obtained at its maximal pressure, the length elongation factor λ (Pmax/Pexp) was used to transform the obtained experimental data (retention times and peak capacities) and construct kinetic performance limit (KPL) curves, allowing a direct visual and unbiased comparison of the selected columns, whereby the YMC Triart C18 UPLC and ACE C18 columns performed as best. Finally, differences in column performance and the (dis)advantages of both approaches are discussed.

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.

Separation of Aliphatic and Aromatic Carboxylic Acids by Conventional and Ultra High Performance Ion Exclusion Chromatography.

An ion exclusion chromatography (IELC) comparison between a conventional ion exchange column and an ultra-high performance liquid chromatography (UHPLC) dynamically surfactant modified C18 column for the separation of an aliphatic carboxylic acid and two aromatic carboxylic acids is presented. Professional software is used to optimize the conventional IELC separation conditions for acetylsalicylic acid and the hydrolysis products: salicylic acid and acetic acid. Four different variables are simultaneously optimized including H2SO4 concentration, pH, flow rate, and sample injection volume. Thirty different runs are suggested by the software. The resolutions and the time of each run are calculated and feed back to the software to predict the optimum conditions. Derringer's desirability functions are used to evaluate the test conditions and those with the highest desirability value are utilized to separate acetylsalicylic acid, salicylic acid, and acetic acid. These conditions include using a 0.35 mM H2SO4 (pH 3.93) eluent at a flow rate of 1 mL min-1 and an injection volume of 72 μL. To decrease the run time and improve the performance, a UHPLC C18 column is used after dynamic modification with sodium dodecyl sulfate. Using pure water as a mobile phase, a shorter analysis time and better resolution are achieved. In addition, the elution order is different from the IELC method which indicates the contribution of the reversed-phase mode to the separation mechanism.