Central Composite Statistical Design Research Articles

Using central composite experimental design to optimize the degradation of black liquor by Fenton reagent

We investigated the advanced oxidation of the black liquor effluent from the pulp and paper industry using the dark Fenton reaction in a lab-scale experiment based on central composite experimental statistical design. The independent variables considered for the optimization of the oxidative process were temperature, H 2O 2 and Fe(II) concentrations, for a black liquor with a chemical oxygen demand (COD) of 628 mg·L −1 O 2 at pH = 3. The response functions were the decrease in COD, aromatic content (UV 254) and lignin content (UV 280). The methodology lets us identify and statistically evaluate the effects and interactions of the study variables and their roles in the efficiency of the treatment process. In the optimization, the correlation coefficients for the model (R 2) were 0.954 for COD, 0.936 for UV 254 and 0.945 for UV 280. Optimum reaction conditions at pH = 3 and temperature = 298 K were [H 2O 2] = 44.1 mM and [Fe(II)] = 4.655 mM. At these optimal conditions, the molar ratio H 2O 2/Fe(II) was 9.5. Under these conditions, 90 min of treatment resulted in a 94.8% decrease in COD, an 80.9% decrease in UV 254 and an 85.6% decrease in UV 280.

Optimization of protoplast yields from the red algae Gracilaria dura (C. Agardh) J. Agardh and G. verrucosa (Huds.) Papenfuss

This study reports on the optimization of protoplast yield from two important tropical agarophytes Gracilaria dura and Gracilaria verrucosa using different cell-wall-degrading enzymes obtained from commercial sources. The conditions for achieving the highest protoplast yield was investigated by optimizing key parameters such as enzyme combinations and their concentrations, duration of enzyme treatment, enzyme pH, mannitol concentration, and temperature. The significance of each key parameter was also further validated using the statistical central composite design. The enzyme composition with 4% cellulase Onozuka R-10, 2% macerozyme R-10, 0.5% pectolyase, and 100 U agarase, 0.4 M mannitol in seawater (30‰) adjusted to pH 7.5 produced the highest protoplast yields of 3.7 ± 0.7 × 106 cells g−1 fresh wt for G. dura and 1.2 ± 0.78 × 106 cells g−1 fresh wt for G. verrucosa when incubated at 25°C for 4–6 h duration. The young growing tips maximally released the protoplasts having a size of 7–15 μm in G. dura and 15–25 μm in G. verrucosa, mostly from epidermal and upper cortical regions. A few large-size protoplasts of 25–35 μm, presumably from cortical region, were also observed in G. verrucosa.

Use of multivariate statistical techniques to optimize the simultaneous separation of 13 phenolic compounds from extra-virgin olive oil by capillary electrophoresis

Characterization of phenolic compounds in olive oil has not been achieved as yet, owing to the complexities of their chemical structures and analytical matrix. The aim of this work is to optimize and validate a method for simultaneous separation and quantification of 13 phenolic compounds from extra-virgin olive oil: tyrosol, hydroxytyrosol, oleuropein glycoside, ferrulic acid, p-coumaric acid, cinnamic acid, p-hydroxybenzoic acid, gallic acid, caffeic acid, luteolin, apigenin, vanillic acid and 3,4-dihydroxybenzoic acid. A statistical central composite design, response surface analysis and the simultaneous optimization method of Derringer and Suich were used to separate all the peaks. These multivariate procedures were efficient in determining the optimal separation condition, using five peak-pair resolutions and runtime as responses. The optimized method employed a fused-silica capillary of 50μm i.d.×60cm effective length with extended light path, 50mmolL−1 boric acid electrolyte, 10.2 pH, 25°C, injection of 50mbar for 25s with application of reverse voltage (−30kV for 5s) before setting the running voltage (+30kV) with detection at 210nm and a run time of 12min. Peak resolutions are found to be very sensitive to pH values outside the 10.15–10.25 range but acceptable electropherograms can be obtained for a wide range of boric acid concentrations within this pH interval.

Development and optimization of solid lipid nanoparticles of amikacin by central composite design

Solid lipid nanoparticles (SLNs) have been studied as a drug-delivery system for the controlling of drug release. These colloidal systems have many important advantages, such as biocompatibility, good tolerability, and ease of scale-up. In the preparation of SLNs, many factors are involved in the characteristics of the particles, such as particle size, drug loading, and zeta potential. In this study, fractional factorial design was applied to examine which variables affect the physicochemical properties of amikacin SLNs. Study was continued by a statistical central composite design (CCD) to minimize particle size and maximize drug-loading efficiency of particles. The results showed that three quantitative factors, including the amount of lipid phase, ratio of drug to lipid, and volume of aqueous phase, were the most important variables on studied responses. The best predicted model for particle size was the quadratic model, and for drug-loading efficiency, was the linear model without any significant lack of fit. Optimum condition was achieved when the ratio of drug to lipid was set at 0.5, the amount of lipid phase at 314 mg, and the volume of aqueous phase at 229 mL. The optimized particle size was 149 ± 4 nm and the drug-loading efficiency 88 ± 5%. Polydispersity index was less than 0.3. The prepared particles had spherical shape, and the drug release from nanoparticles continued for 144 hours (6 days) without significant burst effect.

Dynamic mechanical properties of decorative papers impregnated with melamine formaldehyde resin

Papers impregnated with melamine formaldehyde based resins are widely used in decorative surface finishing of engineered wood based panels for indoor and outdoor applications. For cost-effective production of high-quality impregnated papers it is of great importance to understand the complex interplay between manufacturing conditions and technological property profile. In the present study, three raw papers from different suppliers were impregnated with melamine formaldehyde resin in an industrial scale experiment to study the influence of some important manufacturing variables on the processability of impregnated papers. As numerical factors the resin loading, the final moisture content and the amount of curing catalyst were systematically varied according to a statistical central composite design. The model papers were analyzed for their rheological and thermal properties using the dynamic mechanical method developed by Golombek. As target values flow time, cure time, curing rate and flexibility were used to calculate quantitative models for the processability of the impregnated papers using response surface methodology. It is shown that the relevant rheological and thermal paper parameters are significantly influenced by the supplier of the raw paper as well as the manufacturing variables.

Squalene versus Ergosterol Formation Using Saccharomyces cerevisiae: Combined Effect of Oxygen Supply, Inoculum Size, and Fermentation Time on Yield and Selectivity of the Bioprocess

The dynamics of two wild type strains of Saccharomyces cerevisiae (BY4741 and EGY48) that vary in the ability to produce sterols were compared in batch cultures under different aeration conditions. Poor supply of oxygen enhanced selectivity of the bioprocess in favor of squalene formation. Optimization of inoculum size and fermentation time arranged according to a central composite statistical design revealed significant differences between the strains in terms of yield and productivity. Experimental verification showed that an optimized bioprocess under semianaerobic conditions is competitive with regard to those reported in the literature. Maximum squalene yield and productivity were, respectively, 2967.6 +/- 118.7 microg/L of culture medium and 104 +/- 4.2 microg/Lh for BY4741 and 3129 +/- 109.5 microg/L of culture medium and 155.9 +/- 5.5 microg/Lh for EGY48. The prospect of developing high-purity squalene preparations that meet food safety regulation demands is expected to attract the interest of the food industry.

Experimental Design for the Optimization of Lipid Nanoparticles

Solid lipid nanoparticles (SLN) have been extensively investigated as a promising drug delivery system for controlling the release of therapeutic agents. Currently, there are many manufacturing methods available for SLN, including the high pressure homogenization method and the microemulsion technique. In addition, the solvent diffusion method has been discussed as an alternative technique in the literature, and has attracted great interest due to its simplicity and ease of handling. In order to gain a deeper understanding of this method, a statistical central composite design was applied in this study to examine how the physicochemical properties of the SLN were influenced by the variation of process parameters, including injected solvent, lipid concentration, surfactant concentration, temperature, and stirring speed. Our study showed that lipid concentration and temperature seemed to be the crucial parameters for the particle size of the monostearin SLN prepared by the solvent diffusion method. However, neither of these factors had a significant quadratic relationship with the zeta potential.

Production of organic solvent tolerant lipase by Staphylococcus caseolyticus EX17 using raw glycerol as substrate

AbstractBACKGROUND: In this work we used Plackett–Burman statistical design and central composite design in order to optimize culture conditions for lipase production by Staphylococcus caseolyticus strain EX17 growing on raw glycerol, which was obtained as a by‐product of the enzymatic synthesis of biodiesel. The stability of lipase was verified over several organic solvents, such as methanol, ethanol and n‐hexane.RESULTS: Optimal culture conditions for lipase production were found to be 36 °C, initial pH 8.12, glycerol 30 g L−1, olive oil 3.0 g L−1, and soybean oil 2.5 g L−1, with 145.8 U L−1 of enzyme activity. When commercial glycerol was substituted by the raw glycerol from biodiesel synthesis, lipolytic activity was 127.3 U L−1. Experimental validation of enzyme production matched values predicted by the mathematical model, which was 138.3 U L−1. Stability tests showed that lipase from S. caseolyticus EX17 was stable in methanol, ethanol, and n‐hexane.CONCLUSIONS: Results obtained in this work suggest that raw glycerol can be used for lipase production by S. caseolyticus EX17 and that this enzyme has a potential application in the synthesis of biodiesel. Copyright © 2008 Society of Chemical Industry

Otimização de método para determinação de flavonóis e flavonas em frutas por cromatografia líquida de alta eficiência utilizando delineamento estatístico e análise de superfície de resposta

This work optimized the HPLC conditions for the simultaneous determination of luteolin, apigenin, myricetin, quercetin and kaempferol in aglycone form, as well defined the best conditions for hydrolysis/extraction of these flavonoids in fruits, using the statistical central composite design and response surface analysis. A reverse phase method was developed using a gradient of methanol/water acidified with 0.3% formic acid as mobile phase and a photodiode array detector. The samples were extracted with methanol/water (50:50 v/v) at 90 oC. The optimum time and HCl concentration varied for the different fruits investigated, demonstrating the necessity of optimizing these conditions for each fruit analyzed. Good recovery (87.1 to 96.3%), repeatability and linearity were obtained.

Michael Addition Reaction Kinetics of Acetoacetates and Acrylates for the Formation of Polymeric Networks

2-Ethylhexyl acrylate and ethyl acetoacetate were reacted in a Carbon – Michael addition reaction as a model for subsequent studies of polymer networks. A statistical design of reactions was conducted in the presence of an in-situ ATR FTIR spectrometer to determine the effect of solvent, base, base concentration, and reactant stoichiometry on the observed rate constant. In particular, a central composite statistical design of experiments analysis was performed for model reactions that were catalyzed using either 1,8-diazbicyclo[5.4.0]undec-7-ene (DBU) or K2CO3 at various concentrations. Poly(propylene glycol) bisacetoacetate (PPG BisAcAc) and poly(propylene glycol) diacrylate (PPGDA) networks were then prepared in the absence of solvent at 23°C based on optimized conditions in the presence of DBU and K2CO3. In a similar fashion to model studies, in-situ FTIR spectroscopy was utilized, and observed rate constants were determined. The influence of PPG BisAcAc molecular weight on dynamic mechanical properties was determined and gel fraction analysis was conducted. It appears that the selection of base significantly altered the rate of the reaction, but had an insignificant effect on mechanical properties.

Developement of serum-free media in CHO-DG44 cells using a central composite statistical design

A serum free medium was developed for the production of recombinant antibody against Botulinum A (BoNTA) using dihydrofolate reductase deficient Chinese Hamster Ovary Cells (CHO-DG44) in suspension culture. An initial control basal medium was prepared, which was similar in composition to HAM's F12: IMDM (1:1) supplemented with insulin, transeferrin, selenium and a lipid mixture. The vitamin concentration of the basal medium was twice that of HAM's F12: IMDM (1:1). CHO-DG44 cells expressing S25 antibody grew from 2 x 10(5) cells to maximum cell density of 1.04 x 10(6) cells/ml after 5 days in this control medium. A central composite design was used to identify optimal levels and interaction among five groups of medium components. These five groups were glutamine, Essential Amino Acids (EAA), Non Essential Amino Acids (NEAA), Insulin, Transferrin, Selenium (ITS), and lipids. Fifty experiments were carried out in four batches, with two controls in each batch. There was little effect of ITS and Lipid concentrations over the range studied, and glutamine concentration showed a strong interaction with EAA. The optimal concentrations of the variables studied were 2.5 mM Glutamine, 7.4 mM (2x) EAA, 1.4 mM (0.5x) NEAA, 1x ITS supplement, 0.7x Lipids supplement. The maximum viable cell density attained in the optimized medium was 1.4 x 10(6) cells/ml, a 35% improvement over the control culture, while the final antibody titer attained was 22 +/- 3.4 mug/mL, a 50% improvement.

Enhanced Biosynthesis of Sulfide Oxidase by Arthrobacter Species Using Response Surface Methodology

AbstractResponse surface methodology was used to develop a fermentation medium for the enhanced biosynthesis of a novel sulfide oxidase by Arthrobacter species strain FR‐3. The interactive effect of the medium components – such as glucose as the carbon source, and tryptone and yeast extract as the nitrogen source – was evaluated by a 23‐factorial central composite statistical design. Glucose and yeast extract were found to be the more influential medium constituents compared to tryptone since they had lower coefficients of linear effect, P‐values (< 0.02). The optimal fermentation medium components for the enhanced production of sulfide oxidase were recorded as glucose (8.98 g/L), tryptone (10.62 g/L) and yeast extract (7.3 g/L). Optimization of the medium constituents increased the experimental enzyme yield by 54 % compared to the unoptimized medium. This is the first report on the overproduction of sulfide oxidase by using response surface methodology.

Application of experimental design and optimization to PFC model calibration in uniaxial compression simulation

A new approach has been devised for calibrating contact-bonded particle models using ‘experimental design’ and ‘optimization’ in uniaxial compression simulation. These are applied to calculate an optimum set of microparameters used in generation of models to be tested in uniaxial compression simulations. Sensitivities of microparameters with respect to uniaxial compressive strength (UCS), Young's modulus, and Poisson's ratio (i.e. macroscopic responses of model) were tested by the Plackett–Burman (PB) design method. Then, for each macroscopic response, two microparameters having the largest impacts were singled out and their non-linear relations to macroscopic responses were estimated by statistical Central Composite Design (CCD) method. Using the results from PB design and CCD method, the problem of finding a set of microparameters was solved. Using an optimization method, the optimum set is obtained that gives the best agreement either in quantitative or in qualitative ways between the results both from the bonded particle model simulations and laboratory. The overall procedure was applied to calculate optimum sets of microparameters for generation of bonded particle models for uniaxial compression simulations on different rock types. Results from both simulations and laboratory tests gave fair agreements. The method currently provides adequate solutions and shows relatively fair applicability to simulation of rock materials with their physical properties falling within the following ranges: UCS (40–170 MPa), Young's modulus (20–50 GPa), and Poisson's ratio (0.19–0.25).

Experimental design and response surface modeling applied for the optimisation of pectin hydrolysis by enzymes from A. niger CECT 2088

Optimisation of pectin hydrolysis using pectolytic enzymes produced by Aspergillus niger CECT 2088 was carried out. The effect of enzyme concentration (0.018–0.072%, w/v), substrate concentration (0.004–0.896%, w/v), pH (4.49–5.91), temperature (32.2–67.8 °C) and reaction time (18.2–71.8 min) on the enzymatic process was studied. The experiments were arranged according to a central composite statistical design. Response surface methodology (RSM) was used to assess factor interactions and empirical models regarding four product response variables (i.e., reactor conversion, reducing sugar concentration, endopectolytic productivity and enzymatic depolymerization productivity). Multi-response optimisation was also performed on the reactor and endopectolytic productivity data set of the factorial design. The highest reactor conversion (61%) and endopectolytic productivity (7.2 cSt mg −1 ml −1) were achieved with 1 h reaction time at 46 °C and pH 4.8 at a substrate/enzyme ratio of 11.6.

Process improvement approach to the saponification reaction by using statistical experimental design

The purpose of this study was to determine the effective operating parameters and the optimum operating conditions of a batch saponification process in the frame of the process improvement. Full two-level factorial and face-centered central composite (FCCC) statistical experimental design methods were used successively. Examined parameters were the main and interaction effects of temperature, agitation rate, initial sodium hydroxide (NaOH) and ethyl acetate (EtOAc, CH 3COOC 2H 5) concentrations. Selected process response was the fractional conversion rate of NaOH ( X A). Temperature and agitation rate were found to have no effect on the response at the 10% selected significance level ( α = 0.1). The dependence of response on the NaOH and EtOAc concentrations was illustrated by a linear second-order polynomial model. Examination of the residuals served as a diagnostic check of the model and it was found that the model was good enough to fit the experimental data. Optimum operating conditions at which maximum X A was obtained about 100% were found to be 0.01 mol L −1 NaOH and 0.1 mol L −1 EtOAc by applying response surface method (RSM). With the use of residual analysis and statistical techniques, more reliable and proper results were obtained at the process improvement stage of the saponification process.

Optimization of extrusion conditions for elimination of mesophilic bacteria during thermal processing of animal feed mash

Salmonella and other pathogenic organisms that infect poultry and other livestock can originate from feed and environmental sources. Thus, measures are taken to control Salmonella infection in animals to improve food safety and reduce production losses. The current study was designed to investigate and optimize extrusion conditions for reducing bacterial counts in a surrogate feed matrix. A single-screw extruder was used to process feed artificially inoculated with Bacillus stearothermophilus 12980 (ATCC, Reston, Virginia). Preliminary experiments demonstrated that Salmonella typhimurium ( S. typhimurium NAL r) was eliminated from feed under conditions of moderate extrusion stringency (285 g moisture/kg mash feed, 83 °C extruder barrel exit temperature, 7 s retention time in the extruder barrel) and, therefore, a more thermotolerant organism was required to conduct the study. Spores of B. stearothermophilus 12980 inoculated into a surrogate feed matrix consisting of 600 g maize meal/kg, 300 g soya bean meal/kg and 100 g animal protein blend/kg, respectively, was used to investigate the effect of three extrusion variables on microbial killing. The three variables were extruder barrel exit temperature ( T), mash feed moisture content ( M c), and mean retention time of feed in the extruder barrel ( R t). A rotatable central composite statistical design was used with three independent variables and five levels each. The quadratic response surface model fit to spore count data was used to predict extrusion conditions that maximized bacterial killing. The response surface indicated a stationary point within the design region that was a saddle. An estimated ridge of maximum killing indicated that a maximum reduction of 1.03 log cycles would occur under the following extruder settings: T = 110 °C, M c = 245 g/kg and R t = 11 s. Because the moderate stringency condition ( T = 83 °C, M c = 285 g/kg and R t = 7 s) completely eliminated detectable S. typhimurium in the test feed matrix, it would appear that all S. typhimurium cells and all mesophilic organisms of similar thermal tolerance would be eliminated at most extruder conditions within the central composite design region.

Hydrodynamic and Mass Transfer Parameters in Agitated Reactors Part II: Gas-Holdup, Sauter Mean Bubble Diameters, Volumetric Mass Transfer Coefficients, Gas-Liquid Interfacial Areas, and Liquid-Side Mass Transfer Coefficients

The equilibrium gas solubility (C*), gas-holdup (eG), Sauter mean bubble diameter (dS), volumetric mass transfer coefficient (kLa), gas-liquid interfacial area (a) and mass transfer coefficient (kL) of N2, O2 and air were measured in an agitated reactor operating in surface-aeration (SAR), gas-inducing (GIR) or gas-sparging (GSR) modes in pure toluene and three mixtures of organic liquids (toluene-benzoic acid-benzaldehyde) aimed at simulating the continuous liquid phase toluene oxidation (LPTO) under wide ranges of temperatures (300-453K), pressures (1-15 bar), mixing speeds (13.3-20.0 Hz), superficial gas velocities (0.000-0.004 m/s in the GSR) and liquid heights (0.171-0.268m in the SAR and GIR).C* values of the gases in the organic liquids were calculated using a modified Peng-Robinson Equation-of-State and kLa data were determined using the Transient Physical Absorption technique. The bubble size distributions as well as dS were obtained from the Photographic method, and eG values were measured through the Dispersion Height technique using the reactor’s Jerguson windows. From eG, dS and kLa experimental values, a and kL were calculated under various operating conditions. The Central Composite Statistical Design and analysis technique was used to study the effect of operating conditions on the hydrodynamic and mass transfer parameters.At constant temperature, the equilibrium solubilities (C*) of the three gases in all liquids used appeared to increase linearly with pressure and obey Henry’s Law, however, the values exhibited minima with increasing temperature. The C* values were found to increase with increasing gas molecular weight, and decrease with the addition of benzaldehyde and benzoic acid to pure toluene. A dimensionless form of Arrhenius-type equation, in which the activation energy was dependent of temperature, was developed to predict Henry’s law constant for the three gases in toluene and mixtures with a regression coefficient > 99%.In the SAR, increasing N, T or decreasing H increased eG, a, kL and kLa, and decreased dS, whereas increasing P, decreased eG, a, kL and kLa. In the GIR, increasing N or decreasing H increased eG, a, kL, kLa and dS. Also, increasing T increased and then decreased eG and a; increased kL and kLa; and decreased dS. In addition, increasing P did not affect these hydrodynamic and mass transfer parameters under the operating conditions used. In the GSR, increasing N, T and UG increased eG, a, kL and kLa. Also, increasing N and T, or decreasing UG decreased dS.The addition of benzaldehyde and benzoic acid to pure toluene was found to significantly affect the hydrodynamic parameters (dS and eG), in the GSR and GIR, especially at low temperature due to formation of froth, which led to the enhancement of kLa. The hydrodynamic and mass transfer parameters obtained indicated that the behavior of the SAR was mainly dependent on kL, whereas those of the GSR and GIR were strongly affected not only by kL, but also by a. Statistical correlations were also developed to predict the hydrodynamic and mass transfer parameters obtained in this study with confidence levels > 95%. These correlations could be used to model, design and scale-up the LPTO process in agitated reactors.

Influence of energy input and initial moisture on physical properties of microwave-vacuum dried strawberries

In microwave-vacuum drying, thermal energy is replaced by electric energy for heating the material. The additional application of a sufficient vacuum results in a gentle treatment, and specific product features such as aroma and flavor components, and color can be conserved. A crisp texture results from puffing due to expansion when moisture evaporates within the product, and is related to porosity. Using strawberries, a statistical central composite design was applied to relate specific drying energy and evaporation rate as well as raw and bulk density, and particle size distribution to absorbed microwave power input ranging from 2.4 kW kg−1 to 10.5 kW kg−1 dry matter, and to an initial moisture content of 0.17 kg kg−1 to 0.73 kg kg−1 on dry basis, achieved by convective predrying. A low initial moisture content and high microwave power lead to products with low density, porous structure and optimum puffing effects, but shows disadvantages with respect to moisture evaporation rate and energy utilization. On the other hand, optimum efficiency results from the use of raw materials with a high initial moisture content and from applying a high microwave power input.

Enhancement of transglutaminase-induced protein cross-linking by preheat treatment of cows’ milk: A statistical approach

Optimization of heat treated milk towards protein cross-linking induced by transglutaminase was carried out. Capillary electrophoresis was employed to study the extent of cross-linking under different preheating temperatures (70–90 °C) and times (15–60 min). The experiments were arranged according to a central composite statistical design (32+centre points). Response surface methodology was used to assess factor interactions and empirical models regarding relative peak area (%) of individual protein (αs2-casein, αs1-casein, αs0-casein, κ-casein, β-casein A1, β-casein A2, α-lactalbumin and β-lactoglobulin) and total αs-caseins, total β-caseins and whey proteins (sum of α-lactalbumin and β-lactoglobulin). Multi-response optimization was also performed on the total αs-caseins, total β-caseins, κ-casein and whey proteins data set of the factorial design. The desirability function was the statistical tool employed in this multi-optimization step. The optimum preheating conditions that maximized the cross-linking reactions catalyzed by transglutaminase were achieved within 60 min at 84.5 °C.

Hydrodynamic and Mass Transfer Parameters in Agitated Reactors Part I: Critical Mixing Speed, Induced Gas Flow Rate, and Wavy Surface in SARs and GIRs

The critical mixing speed for gas entrainment (NCRE), for gas induction (NCRI), induced gas flow rate (QGI) as well as the wavy gas-liquid interfacial area (aWave) of N2 and air were measured in pure toluene and three mixtures of organic liquids (toluene-benzoic acid-benzaldehyde mixtures) under wide ranges of temperatures, T (300-453K), pressures, P (1-15 bar), mixing speeds, N (13.3-23.3Hz) and liquid heights, H (0.171-0.268m) using a 4-liter, see-through agitated autoclave operating as a surface-aeration reactor (SAR) and gas-inducing reactor (GIR).NCRE and NCRI as well as aWave were estimated by analyzing the videos taken with an on-line high-speed Phantom camera through the reactor’s Jerguson windows. In the GIR, QGI was determined using a highly sensitive Coriolis mass flow meter. The Central Composite Statistical Design and analysis technique was used to study the effect of operating conditions on these hydrodynamic parameters.NCRE and NCRI appeared to increase with liquid height and decrease with temperature, whereas, the pressure and gas nature did not significantly affect both parameters. The liquid physicochemical properties were found to strongly affect NCRE and NCRI, and QGI. Increasing mixing speed or decreasing liquid height increased QGI. Increasing temperature or decreasing liquid viscosity initially increased and then decreased QGI. Increasing pressure or gas density on the other hand decreased QGI. Increasing mixing speed and temperature or decreasing liquid height significantly enhanced aWave, as compared to the flat liquid surface. At high pressures, however, lower values of aWave were obtained. Empirical and statistical correlations were also developed to accurately predict NCRE, NCRI, QGI and aWave.