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 0.1-30.0 μM and 30.0-330.0 μM with a limit of detection (LOD) of 0.05 μM. 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.

In silico modeling of in situ fluidized bed melt granulation

Fluidized bed melt granulation has recently been recognized as a promising technique with numerous advantages over conventional granulation techniques. The aim of this study was to evaluate the possibility of using response surface methodology and artificial neural networks for optimizing in situ fluidized bed melt granulation and to compare them with regard to modeling ability and predictability. The experiments were organized in line with the Box-Behnken design. The influence of binder content, binder particle size, and granulation time on granule properties was evaluated. In addition to the response surface analysis, a multilayer perceptron neural network was applied for data modeling. It was found that in situ fluidized bed melt granulation can be used for production of spherical granules with good flowability. Binder particle size had the most pronounced influence on granule size and shape, suggesting the importance of this parameter in achieving desired granule properties. It was found that binder content can be a critical factor for the width of granule size distribution and yield when immersion and layering is the dominant agglomeration mechanism. The results obtained indicate that both in silico techniques can be useful tools in defining the design space and optimization of in situ fluidized bed melt granulation.

Comparison of extraction methods for the identification and quantification of polyphenols in virgin olive oil by ultra-HPLC-QToF mass spectrometry

In this work, liquid-liquid extraction (LLE) and solid phase extraction (SPE), of polyphenols from a VOO sample were optimised by a Plackett-Burman experimental design; then the two extraction techniques capabilities were compared. By using HPLC-DAD, the extraction ability of SPE with the diol phase and LLE were similar. The two methods were further evaluated with ultra HPLC-ESI QToF in negative ion mode by recoveries of standards and matched comparison of the peak area of 40 identified and 27 unidentified compounds. Conclusions indicate that LLE gives better recoveries for highly polar, non-polar, and some polyphenols suspected to contain a nitrogen atom, while for the others the two methods seem to be equally suitable. The presence of nitrogen-containing polyphenols was confirmed in positive ionisation mode in LLE extract, whereas in the SPE extract they were not present. One of them was tentatively identified as a compound containing tyrosine and methyl-decarboxymetyl-eleanoic acid moieties.

Fosetyl-Al photo-Fenton degradation and its endogenous catalyst inhibition

Interferences from many sources can affect photo-Fenton reaction performance. Among them, catalyst inhibition can be caused by the complexation and/or precipitation of iron species by the organic matter and salts present in the reaction media. This is the case of the oxidation of effluents containing organophosphorous fosetyl-Al. The degradation of this fungicide generates phosphate anions that scavenge iron and hinder Fe(II) availability. Experimental design was applied to artificially enlighten photo-Fenton reaction, in order to evaluate fosetyl-Al degradation. The performed experiments suggested how iron inhibition takes place. The monitoring of photo-Fenton reaction over a mixture of fosetyl-Al with other two pesticides also showed the interferences caused by the presence of the fungicide on other species degradation. Solar empowered photo-Fenton was also essayed for comparison purposes. Artificial and solar light photo-Fenton reactions were revealed as effective treatments for the elimination of tested fungicide. However, the phosphate ions generated during fosetyl oxidation decreased iron availability, what hampered organic matter degradation.

Optimization of the combined ultrasonic assisted/adsorption method for the removal of malachite green by gold nanoparticles loaded on activated carbon: experimental design

The present study was aimed to experimental design optimization applied to removal of malachite green (MG) from aqueous solution by ultrasound-assisted removal onto the gold nanoparticles loaded on activated carbon (Au-NP-AC). This nanomaterial was characterized using different techniques such as FESEM, TEM, BET, and UV-vis measurements. The effects of variables such as pH, initial dye concentration, adsorbent dosage (g), temperature and sonication time on MG removal were studied using central composite design (CCD) and the optimum experimental conditions were found with desirability function (DF) combined response surface methodology (RSM). Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Kinetic models such as pseudo -first order, pseudo-second order, Elovich and intraparticle diffusion models applicability was tested for experimental data and the second-order equation and intraparticle diffusion models control the kinetic of the adsorption process. The small amount of proposed adsorbent (0.015 g) is applicable for successful removal of MG (RE>99%) in short time (4.4 min) with high adsorption capacity (140-172 mg g(-1)).

Optimization of the ultrasonic assisted removal of methylene blue by gold nanoparticles loaded on activated carbon using experimental design methodology

The present study was focused on the removal of methylene blue (MB) from aqueous solution by ultrasound-assisted adsorption onto the gold nanoparticles loaded on activated carbon (Au-NP-AC). This nanomaterial was characterized using different techniques such as SEM, XRD, and BET. The effects of variables such as pH, initial dye concentration, adsorbent dosage (g), temperature and sonication time (min) on MB removal were studied and using central composite design (CCD) and the optimum experimental conditions were found with desirability function (DF) combined response surface methodology (RSM). Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Analysis of experimental adsorption data to various kinetic models such as pseudo-first and second order, Elovich and intraparticle diffusion models show the applicability of the second-order equation model. The small amount of proposed adsorbent (0.01 g) is applicable for successful removal of MB (RE>95%) in short time (1.6 min) with high adsorption capacity (104-185 mg g(-1)).

Docetaxel Loaded PEG-PLGA Nanoparticles: Optimized Drug Loading, In-vitro Cytotoxicity and In-vivo Antitumor Effect

In this study a 3-factor, 3-level Box-Behnken design was used to prepare optimized docetaxel (DTX) loaded pegylated poly lactide-co-glycolide (PEG-PLGA) Nanoparticles (NPs) with polymer concentration (X1), drug concentration (X2) and ratio of the organic to aqueous solvent (X3) as the independent variables and particle size (Y1), poly dispersity index (PDI) (Y2) and drug loading (Y3) as the responses. The cytotoxicity of optimized DTX loaded PEG-PLGA NPs was studied in SKOV3 tumor cell lines by standard MTT assay. The in-vivo antitumor efficacy of DTX loaded PLGA-PEG NPs was assessed in tumor bearing female BALB/c mice. The optimum level of Y1, Y2 and Y3 predicted by the model were 188 nm, 0.16 and 9% respectively with perfect agreement with the experimental data. The in-vitro release profile of optimum formulation showed a burst release of approximately 20% (w/w) followed by a sustained release profile of the loaded drug over 288 h. The DTX loaded optimized nanoparticles showed a greater cytotoxicity against SKOV3 cancer cells than free DTX. Enhanced tumor-suppression effects were achieved with DTX-loaded PEG-PLGA NPs. These results demonstrated that optimized NPs could be a potentially useful delivery system for DTX as an anticancer agent.

Optimization of solvent bar microextraction combined with gas chromatography for preconcentration and determination of methadone in human urine and plasma samples

In this study, solvent bar microextraction combined with gas chromatography-flame ionization detector (GC-FID) was used for preconcentration and determination of methadone in human body fluids. The target drug was extracted from an aqueous sample with pH 11.5 (source phase) into an organic extracting solvent (1-Undecanol) located inside the pores and lumen of a polypropylene hollow fiber as a receiving phase. To obtain high extraction efficiency, the effect of different variables on the extraction efficiency was studied using an experimental design. The variables of interest were the organic phase type, source phase pH, ionic strength, stirring rate, extraction time, concentration of Triton X-100, and extraction temperature, which were first investigated by Plackett-Burman design and subsequently by central composite design (CCD). So that the optimum experimental condition was obtained when the sodium chloride concentration was 5% (w/v); stirring rate, 700 rpm; extraction temperature, 20 °C; extraction time, 45 min and pH of the aqueous sample, 11.5. Under the optimized conditions, the preconcentration factors were between 275 and 300. The calibration curves were linear in the concentration range of 10-1500 μg L(-1). The limits of detection (LODs) were 2.7-7 and relative standard deviations (RSDs) of the proposed method were 5.9-7.3%. Ultimately, the applicability of the current method was evaluated by the extraction and determination of methadone in different biological samples.

Influence of the operation conditions on CO2 capture by CaO-derived sorbents prepared from synthetic CaCO3

In this work, a statistical experimental design is performed in order to prepare CaCO3 materials for use as CaO-based CO2 sorbent precursors. The influence of different operational parameters such as synthesis temperature (ST), stirring rate (SR) and surfactant percent (SP) on CO2 capture is studied by applying Response Surface Methodology (RSM). The samples were characterized using different analytical techniques including X-ray diffraction, N2 adsorption isotherm analysis and Scanning Electron Microscopy-X-ray Energy Dispersive Spectroscopy (SEM-EDX). CO2 capture capacity was determined by means of a thermogravimetric analyzer which recorded the mass uptake of the samples when these were exposed to a gas stream containing diluted (15%) CO2. The statistical approach used in this work provides a rapid way of predicting and optimizing the main preparation variables of CaO-derived sorbents for CO2 sorption. The results obtained clearly indicate that four parameters statistically influence CO2 uptake: SR, the square of SR, its interaction with SP and the square of SP.

Experimental design approach to evaluate the impact of oak chips and micro-oxygenation on the volatile profile of red wines

A chemometric strategy based on combining an experimental design approach and response surface methodology was applied to gain further knowledge on the influence of chip maceration and micro-oxygenation related factors (oxygen doses, chip doses, wood origin, toasting degree and maceration time) on the volatile profile of red wines during the accelerated ageing process. The results obtained indicated that the volatile profile of wines could be modulated by applying different combinations of factor conditions. Thus, these results would be used to obtain wines with specific volatile profiles that would lead to particular olfactory attributes according to consumers' preferences. Moreover, it was shown that combining wood from different origins helped enhance the quality of the elaborated wines. To the best of our knowledge, this is the first time that an experimental design methodology has been applied to simultaneously evaluate the influence of five different ageing parameters on the volatile profile of red wines.

High performance liquid chromatography tandem mass spectrometry determination of perfluorinated acids in cow milk

A new and sensitive liquid chromatography/electrospray-tandem mass spectrometric (LC/ESI-MS/MS) method for the determination of 12 perfluorinated compounds (PFCs) in cow milk is described. Milk samples were extracted with acetone and cleaned-up by a graphitized carbon black solid-phase extraction cartridge, optimizing the entire procedure by using a screening experimental design. LC/ESI-MS/MS was performed in negative ion mode using multiple reaction monitoring mode. The performance of the method was evaluated under the optimized conditions in terms of matrix effects, range of linearity, accuracy, and repeatability. For all compounds, linearity in matrix was observed in the range LOQ-10μgL(-1), and coefficients of determination R(2) ranged from 0.9982 to 0.9999. The analytical recoveries, relative to the isotopic internal standard, measured at 10 and 50ngL(-1) were in the range of 91-105%, with relative standard deviations below 6% and method detection limit, based on the blank value +3 times the standard deviation of the blank, ranged from 0.5 to 3ngL(-1). The final method developed was used to determine the concentration of PFCs in 15 retail milk samples. None of these compounds were detected in cow milk analyzed samples.

Repeated randomization and matching in multi-arm trials

Cluster randomized trials with relatively few clusters have been widely used in recent years for evaluation of health-care strategies. The balance match weighted (BMW) design, introduced in Xu and Kalbfleisch (2010, Biometrics 66, 813-823), applies the optimal full matching with constraints technique to a prospective randomized design with the aim of minimizing the mean squared error (MSE) of the treatment effect estimator. This is accomplished through consideration of M independent randomizations of the experimental units and then selecting the one which provides the most balance evaluated by matching on the estimated propensity scores. Often in practice, clinical trials may involve more than two treatment arms and multiple treatment options need to be evaluated. Therefore, we consider extensions of the BMW propensity score matching method to allow for studies with three or more arms. In this article, we propose three approaches to extend the BMW design to clinical trials with more than two arms and evaluate the property of the extended design in simulation studies.

Quality by Design approach in the development of a solvent-modified micellar electrokinetic chromatography method: finding the design space for the determination of amitriptyline and its impurities

A solvent-modified micellar electrokinetic chromatography method was set up for the simultaneous determination of the tricyclic antidepressant amitriptyline (AMI) and its main impurities. The method was developed following Quality by Design (QbD) principles according to ICH Guideline Q8(R2). QbD approach made it possible to find the design space (DS), where quality was assured. After a scouting phase, aimed at selecting a suitable capillary electrophoresis pseudostationary phase, risk assessment tools were employed to define the critical process parameters (CPPs) to be considered in a screening phase (applied voltage, concentration and pH of the background electrolyte, concentration of the surfactant sodium dodecyl sulphate, of the cosurfactant n-butanol and of the organic modifiers acetonitrile and urea). The effects of the seven selected CPPs on critical quality attributes (CQAs), namely resolution values between critical peak pairs and analysis time, were investigated throughout the knowledge space by means of a symmetric screening matrix. Response surface study was then carried out on four selected CPPs by applying a Doehlert Design. Monte-Carlo simulations were performed in order to estimate the probability of meeting the desired specifications on CQAs, and thus to define the DS by means of a risk of failure map. Additional points at the edges of the DS were tested in order to verify the requirements for CQAs to be fulfilled. A control strategy was implemented by defining system suitability tests. The developed method was validated following ICH Guideline Q2(R1), including robustness assessment by Plackett-Burman design, and was applied to the analysis of real samples of amitriptyline coated tablets.

Removing lead from metallic mixture of waste printed circuit boards by vacuum distillation: factorial design and removal mechanism

The lead removal from the metallic mixture of waste printed circuit boards by vacuum distillation was optimized using experimental design, and a mathematical model was established to elucidate the removal mechanism. The variables studied in lead evaporation consisted of the chamber pressure, heating temperature, heating time, particle size and initial mass. The low-level chamber pressure was fixed at 0.1 Pa as the operation pressure. The application of two-level factorial design generated a first-order polynomial that agreed well with the data for evaporation efficiency of lead. The heating temperature and heating time exhibited significant effects on the efficiency, which was validated by means of the copper-lead mixture experiments. The optimized operating conditions within the region studied were the chamber pressure of 0.1 Pa, heating temperature of 1023 K and heating time of 120 min. After the conditions were employed to remove lead from the metallic mixture of waste printed circuit boards, the efficiency was 99.97%. The mechanism of the effects was elucidated by mathematical modeling that deals with evaporation, mass transfer and condensation, and can be applied to a wider range of metal removal by vacuum distillation.

Statistical reporting deficiencies in environmental toxicology

Null hypothesis significance testing is one of the most widely used forms of statistical testing in environmental toxicology. In this short communication, the authors show that the reporting of statistical information when using null hypothesis significance testing is frequently inadequate in environmental toxicology research. The authors demonstrate this by analyzing the statistical information reported for papers employing t tests or analyses of variance in the Environmental Toxicology section of Environmental Toxicology and Chemistry in 2010, which comprised 68% of papers published by this journal in that year. Of these papers, 60% fail to report exact p values, 85% fail to provide degrees of freedom, and 90% fail to report critical effect sizes. Statistical power was reported in only <2% of the published papers. The insufficient provision of statistical information makes interpretation of study results by reviewers and readers difficult. Consistently reporting exact p values with degrees of freedom, considering and explicitly stating biologically relevant critical effect sizes, and reporting statistical power associated with nonsignificant results would be easy to implement and would promote scientific progress in environmental toxicology through increased statistical transparency.

A simple, robust and highly efficient transient expression system for producing antibodies

Transient expression systems in mammalian cells have become the method of choice for producing research quantities of antibodies. Both the speed and yield of the available transient systems and the natural posttranslational modifications favor these systems above expression in lower eukaryotes, prokaryotes or stable cell lines. We describe an optimized mammalian transient expression system, capable of producing up to 400mg/L of native secreted antibodies in less than a week. The system is composed of commercially available components and is based on expression in the fast growing suspension cell line, FreeStyle™ 293-F (HEK-293F). The method depends on an optimal combination of a gene transfer method, an expression vector and cotransfection with expression enhancing plasmids, encoding the large T antigen of the SV40 virus and the cell cycle inhibitors p21 and p27. Optimization of all components of the expression system, by experimental design techniques, yielded maximal expression levels (including antibody isotypes IgG1, 2, 3, 4 and Fab fragments of various species). Expression volumes were scalable from 0.1 ml up to 1.2L in a simple shaker flask system in animal component free, low protein medium, enabling consistent production of relatively high amounts of a large number of native antibodies.

More ecological ERA: incorporating natural environmental factors and animal behavior

We discuss the importance of selected natural abiotic and biotic factors in ecological risk assessment based on simplistic laboratory bioassays. Although it is impossible to include all possible natural factors in standard lower-tier ecotoxicological testing, neglecting them is not an option. Therefore, we try to identify the most important factors and advocate redesigning standard testing procedures to include theoretically most potent interactions. We also point out a few potentially important factors that have not been studied enough so far. The available data allowed us to identify temperature and O2 depletion as the most critical factors that should be included in ecotoxicity testing as soon as possible. Temporal limitations and fluctuations in food availability also appear important, but at this point more fundamental research in this area is necessary before making decisions on their inclusion in risk assessment procedures. We propose using specific experimental designs, such as Box-Behnken or Central Composite, which allow for simultaneous testing of 3 or more factors for their individual and interactive effects with greater precision and without increasing the effort and costs of tests dramatically. Factorial design can lead to more powerful tests and help to extend the validity of conclusions. Finally, ecological risk assessment procedures should include information on animal behavior, especially feeding patterns. This requires more basic studies, but already at this point adequate mechanistic effect models can be developed for some species.

Intending to adhere or to not adhere: results from an experiment in healthy subjects testing illness perceptions and behavioral intentions in asthma

BACKGROUND

Although illness perceptions have been theorized to predict medication adherence, evidence has been limited to cross-sectional studies.

OBJECTIVE

This study evaluated the impact of illness identity, consequence, cause and personal control on medication adherence intentions in healthy subjects exposed to a scenario describing asthma-related illness perceptions.

METHODS

An experimental design (2×2×2×2 factorial design) was used to create 16 asthma patient scenarios. University students with no asthma experience were recruited for the study. The Medication Adherence Report Scale for Asthma (MARS-A) was modified as intention statements consistent with the scenarios. Also, a medication adherence intention statement was included. Factor analysis was used to assess the construct validity of the modified MARS-A. Three intentions to adhere measures were identified: (1) intention to adhere related to symptoms, (2) intention to adhere in general, and (3) intention to not adhere. Each of these three intention measures served as dependent variables in multiple regression analysis with the illness perception constructs.

RESULTS

There were 149 completed responses. Personal control (β = 0.43) and illness consequence (β = 0.14) significantly predicted intention to adhere in general (adjusted R(2) = 0.26). Personal control (β = -0.25) and illness consequence (β = -0.23) significantly predicted intention to not adhere (adjusted R(2) = 0.11).

CONCLUSION

Researchers are advised to consider intention to not adhere and intention to adhere to medication as distinct constructs. This has practical and research implications.

On the limitations of biological knowledge

Scientific knowledge is grounded in a particular epistemology and, owing to the requirements of that epistemology, possesses limitations. Some limitations are intrinsic, in the sense that they depend inherently on the nature of scientific knowledge; others are contingent, depending on the present state of knowledge, including technology. Understanding limitations facilitates scientific research because one can then recognize when one is confronted by a limitation, as opposed to simply being unable to solve a problem within the existing bounds of possibility. In the hope that the role of limiting factors can be brought more clearly into focus and discussed, we consider several sources of limitation as they apply to biological knowledge: mathematical complexity, experimental constraints, validation, knowledge discovery, and human intellectual capacity.

Multivariate optimization of capillary electrophoresis methods: a critical review

In this article a review on the recent applications of multivariate techniques for optimization of electromigration methods, is presented. Papers published in the period from August 2007 to February 2013, have been taken into consideration. Upon a brief description of each of the involved CE operative modes, the characteristics of the chemometric strategies (type of design, factors and responses) applied to face a number of analytical challenges, are presented. Finally, a critical discussion, giving some practical advices and pointing out the most common issues involved in multivariate set-up of CE methods, is provided.

The effect of polymer and CaCl2 concentrations on the sulfasalazine release from alginate-N,O-carboxymethyl chitosan beads

In this study, pH-sensitive blended polymeric beads were prepared by ionic gelation of mixed alginate and N,O-carboxymethyl chitosan (NOCC) solutions in aqueous media containing calcium chloride. To prepare drug-loaded beads, sulfasalazine (SA) as a model drug was added to the initial aqueous polymer solution. These beads were characterized and evaluated in vitro as potential carriers for colon-specific drug delivery. A 3² full factorial experimental design was employed to evaluate the effect of polymer and CaCl₂ concentrations on swelling and drug release behavior of the beads in simulated gastrointestinal tract fluid. It was found that the rate of swelling and drug release decreased significantly with increasing polymer and CaCl₂ concentrations, but polymer concentration was more effective than CaCl₂ concentration. The beads prepared using 4.5% polymer concentration and 4% CaCl₂ concentration retained approximately 60% of the loaded drug before approaching the simulated colonic fluid. Based on the results, the alginate-NOCC beads prepared with high polymer concentration could be potentially suitable polymeric carriers for colon-specific delivery of SA.

Influence of the experimental design of gene expression studies on the inference of gene regulatory networks: environmental factors

The inference of gene regulatory networks gained within recent years a considerable interest in the biology and biomedical community. The purpose of this paper is to investigate the influence that environmental conditions can exhibit on the inference performance of network inference algorithms. Specifically, we study five network inference methods, Aracne, BC3NET, CLR, C3NET and MRNET, and compare the results for three different conditions: (I) observational gene expression data: normal environmental condition, (II) interventional gene expression data: growth in rich media, (III) interventional gene expression data: normal environmental condition interrupted by a positive spike-in stimulation. Overall, we find that different statistical inference methods lead to comparable, but condition-specific results. Further, our results suggest that non-steady-state data enhance the inferability of regulatory networks.

Systematical approach in evaluation of LC method for determination of raloxifene hydrochloride and its impurities employing experimental design

Method validation presents a detailed investigation of analytical method and provision of the evidence that the method, when correctly applied, produces results that fit to the purpose. In order to achieve the method validation scope efficiently, experimental design presents a very useful tool. The greatest benefits of such approach could be seen in robustness testing through the provision of very useful data about the control of the chromatographic system during the routine application. In this paper, robustness testing of the LC method proposed for the determination of raloxifene hydrochloride and its four impurities was done employing Plackett-Burman design. Applying this design, the effect of five real factors (acetonitrile content, sodium dodecyl sulfate content, column temperature, pH of the mobile phase and flow rate) on the corresponding resolution factors was investigated through twelve experiments. Furthermore, the insignificance intervals for significant factors were calculated and the parameters for system suitability tests were defined. Eventually, the other validation parameters were tested and the effectiveness of the proposed analytical method with a high degree of accuracy was confirmed.

Experimental design of medium optimization for invertase production by Pichia sp

The culture medium requirement for invertase production by Pichia sp. was optimized and identified by initial screening method of Plackett-Burman. Furthermore, optimum concentrations of medium components, which were selected by in initial screening by Plackett-Burman, were determined by the Box-Behnken and its representative three-factor response-surface method. The regression models showed significantly high R (2) values of 97% for invertase activities, indicating that they are appropriate for predicting relationships between yeast extract, peptone and sucrose concentration with invertase production. According to the model the optimal concentrations of sucrose, yeast extract and peptone were 40, 5 and 4 g/ml, respectively. These predicted conditions were verified by validation experiments. In the optimized medium Pichia sp. produced invertase with activity of 38.71 U/ml, which is 4 times higher than that produced in original medium. Thus, this statistical approach enabled rapid identification and integration of key medium parameters for Pichia sp. BCCS M1, resulted the high invertase production.

Optimization of forced degradation using experimental design and development of a stability-indicating liquid chromatographic assay method for rebamipide in bulk and tablet dosage form

A novel stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of rebamipide in bulk and tablet dosage form. Rebamipide (drug and drug product) solutions were exposed to acid and alkali hydrolysis, thermal stress, oxidation by hydrogen peroxide and photodegradation. Experimental design has been used during forced degradation to determine significant factors responsible for degradation and to obtain optimal degradation conditions. In addition, acid and alkali hydrolysis was performed using a microwave oven. The chromatographic method employed the HiQ sil C-18HS (250 × 4.6 mm; 5 μm) column with mobile phase consisting of 0.02 M potassium phosphate (pH adjusted to 6.8) and methanol (40:60, v/v) and the detection was performed at 230 nm. The procedure was validated for specificity, linearity, accuracy, precision and robustness. There was no interference observed of excipients and degradation products in the determination of the active pharmaceutical ingredient. The method showed good accuracy and precision (intra and inter day) and the response was linear in a range from 0.5 to 5 μg mL(-1). The method was found to be simple and fast with less trial and error experimentation by making use of experimental design. Also, it proved that microwave energy can be used to expedite hydrolysis of rebamipide.