Chapter 6 Optimization strategies for HPLC and CZE

Analytical Quality by Design (AQbD) Approach to the Development of Analytical Procedures for Medicinal Plants

Scientific regulatory systems with suitable analytical methods for monitoring quality, safety, and efficacy are essential in medicinal plant drug discovery. There have been only few attempts to adopt the analytical quality by design (AQbD) strategy in medicinal plants analysis over the last few years. AQbD is a holistic method and development approach that understands analytical procedure, from risk assessment to lifecycle management. The enhanced AQbD approach reduces the time and effort necessary to develop reliable analytical methods, leads to flexible change control through the method operable design region (MODR), and lowers the out-of-specification (OOS) results. However, it is difficult to follow all the AQbD workflow steps in the field of medicinal plants analysis, such as defining the analytical target profiles (ATPs), identifying critical analytical procedure parameters (CAPPs), among others, because the complexity of chemical and biological properties in medicinal plants acts as a barrier. In this review, various applications of AQbD to medicinal plant analytical procedures are discussed. Unlike the analysis of a single compound, medicinal plant analysis is characterized by analyzing multiple components contained in biological materials, so it will be summarized by focusing on the following points: Analytical methods showing correlations within analysis parameters for the specific medicinal plant analysis, plant raw material diversity, one or more analysis targets defined for multiple phytochemicals, key analysis attributes, and analysis control strategies. In addition, the opportunities available through the use of design-based quality management techniques and the challenges that coexist are also discussed.

Optimized Chromatographic Determination of Naphazoline and Chlorpheniramine in Eye/Nose Drops Using Cation-exchange Column

A simple and efficient liquid chromatographic method has been developed and validated for the simultaneous determination of naphazoline and chlorpheniramine in eye/nose drops, in presence of naphazoline degradation product and naphthalene acetic acid (NAPD). The separation was achieved within 6.0 min, employing a mixture of 53.5% v/v water-acetonitrile containing 78.70 mM/L sodium dihydrogen orthophosphate adjusted to pH 5.30 as isocratic mobile phase, pumped at 1.0 mL/min through a strong cation-exchange column (10 μm particle size), the analytes were monitored at 230 nm. Statistical experimental designs and graphic representations (response surface methodology) were used for optimizing the chromatographic separation. The linearity plots were linear over concentration range up to 125% of the analytes nominal concentrations (100%) with regression coefficients (r) > 0.99, method's accuracy (RSD < 2.0%), repeatability and intermediate precision (RSD < 2.0%) were verified. System suitability parameters were also within the acceptable range. The validated method was successfully employed for the routine analysis of eye/nose drops.

Improvement of biomass production and glucoamylase activity by Candida famata using factorial design

To improve biomass production and glucoamylase activity (GA) by Candida famata, culture conditions were optimized. A 2(3) full factorial design (FFD) with a response surface model was used to evaluate the effects and interactions of pH (X1 ), time of cultivation (X2 ), and starch concentration (X3 ) on the biomass production and enzyme activity. A total of 16 experiments were conducted toward the construction of an empiric model and a first-order equation. It was found that all factors (X1 , X2 , and X3 ) and their interactions were significant at a certain confidence level (P < 0.05). Using this methodology, the optimum values of the three tested parameters were obtained as follows: pH 6; time of cultivation 24 H and starch concentration 7 g/L, respectively. Our results showed that the starch concentration (X3) has significantly influenced both dependent variables, biomass production and GA of C. famata. Under this optimized medium, the experimental biomass production and GA obtained were 1.8 ± 0.54 g/L and 0.078 ± 0.012 µmol/L/Min, about 1.5- and 1.8-fold, respectively, higher than those in basal medium. The (R(2) ) coefficients obtained were 0.997 and 0.990, indicating an adequate degree of reliability in the model. Approximately 99% of validity of the predicted value was achieved.

Enantioselective capillary electrophoretic separation of tryptophane- and tyrosine-methylesters in a dual system with a tetra-oxadiaza-crown-ether derivative and a cyclodextrin

Different dual selector systems containing a cyclodextrin derivative (methyl-beta-cyclodextrin and dimethyl-beta-cyclodextrin) and a new diaza-crown-ether derivative (N-[2-(1,4,10,13-tetraoxa-7,16-diazacyclooctadecan-7-yl)propanoyl]glycine) were studied in the enantioselective separation of tryptophan-methylester and tyrosine-methylester enantiomers. This paper deals with the systematic study of the effects of changing the composition of the background electrolyte on the resolution of the d- and l- forms using an experimental design approach. It was found that the dual systems allowed a better chiral separation of the amino acid derivatives. The experimental design approach also allowed improving the separation compared to the starting conditions (center point of the design), which were adopted from a previous study.

Optimization and validation of a capillary zone electrophoretic method for the simultaneous analysis of four atypical antipsychotics

A capillary zone electrophoretic method has been developed and optimized for separation of four atypical antipsychotics (AAPs): clothiapine (cT), clozapine (cZ), olanzapine (O), and quetiapine (Q). A three-level full-factorial design was applied to study the effect of the pH and molarity of the running buffer on separation. Combination of the studied parameters permitted the separation of the four AAPs, which was best carried out using 80 mM sodium phosphate buffer (pH 3.5). The same system can also be applied for the quantitative determination of these compounds. The method was then validated regarding linearity, precision, and accuracy. Especially, the possibility of simultaneous quantification and identification of the active ingredient in the finished product is very attractive.

Optimization of the chiral separation of some 2-arylpropionic acids on an avidin column by modeling a combined response

The enantiomeric separation of some nonsteroidal antiinflammatory drugs was investigated on an avidin column. An experimental design approach (central composite design) was used to evaluate the effects of three method parameters (pH, concentration of organic modifier, and buffer concentration) on the analysis time and the resolution, as well as to model these responses. This revealed that the organic modifier concentration and sometimes the pH are significant parameters to control because of their influence on both analysis time and resolution. Furthermore, the central composite design results were combined in a multicriteria decision-making approach in order to obtain a set of optimal experimental conditions leading to the most desirable compromise between resolution and analysis time.