Recent Advances in Analytical Techniques

Solid dosage forms are the most common drug delivery systems because they provide reproducible and convenient delivery and they are cost effective. It is possible to use immediate, controlled or extended release systems for therapy using solid dosage form such as tablets, capsules, powders, suppositories and lozenges. Solid dosage forms depend on physical properties of the active substance and excipients. To design an effective system and to enlighten the effectiveness, it is important to determine the critical parameters both in pharmacopeia analysis and scientific studies. These critical parameters are various from active substance stability and purity to its in vivo profile in dosage form. The primary objective to identify these parameters is developing a fast and fully validated method. Liquid chromatographic techniques are very suitable and accurate way to determine the content of a pharmaceutical ingredient and its stability both in in vitro and in in vivo systems. Mobil phase composition, flow rate & column choice directly affect the quality of separation in pharmaceutical analysis. In validation of chromatographic methods, validation parameters should be reported in detail. In this chapter, we will discuss solid dosage forms analyses using high performance chromatographic techniques, in terms of their validation parameters and system suitability tests.

Recently, pharmaceutical companies have been driven to create cheaper, simpler, more novel, and more efficient tools for the discovery, development, delivery, and monitoring of pharmaceutical active ingredients. In this contest, the development of sensitive, rapid, and more effective chromatographic methods is vital for analytical quality control and R&D laboratories. Liquid chromatography (LC) with different kinds of detection modes are widely used in the pharmaceutical analysis area for the quantification and identification of active pharmaceutical ingredients in varied matrices. A completely new version of LC design with improved technology has been developed, namely ultra-high performance liquid chromatography (UHPLC), which has evolved from conventional HPLC. UHPLC can be regarded as a new direction for LC. It is a rather new technique providing new possibilities in liquid chromatography, especially reducing solvent consumption and decreasing the run times. UHPLC improves three areas of LC — namely the speed, efficiency, and sensitivity of analysis by using sub 2 μm particles as a stationary phase. The system is designed as stable in order to overcome high system pressures while the analysis is performed with no negative influence on either the analytical column or the other components of the system. During these days, the quality control of pharmaceutical preparations in industry is moving one step forward with transferring their methods from HPLC to UHPLC. The application of UHPLC methods in the pharmaceutical industry introduces a powerful tool not only for routine analysis but also for clinical approaches. Due to the high throughput investigation like therapeutic drug monitoring studies, special attention is paid to the various detection possibilities. In this chapter, the principles, differences, advantages, and disadvantages of UHPLC are discussed in detail. As a consequence, pharmaceutical applications via UHPLC are also summarized, based on a survey of the literature written since 2012.

Recent developments in column packing materials have improved analysis of a broad range of chemical groups with better chromatographic results in terms of peak shape, capacity factor etc. Hydrophilic interaction liquid chromatography (HILIC) has achieved significant progress especially on the analysis of polar molecules. The technique is analogous to normal-phase chromatography and an alternative approach to effectively separate small polar compounds. Researches focusing on applications of HILIC are increasing due to their unique application in targeted and untargeted metabolomic profiling, which enable the analysis of a wide range of metabolites from multiple metabolic pathways. Accordingly, improved profiling leads to individualized and predictive disease information for personalization of treatment. Combined application of advanced spectroscopic and separation technique is essential for metabolomic studies. This chapter reviews the reference information on the application of HILIC and MS related to separation of metabolites and its effect on various parameters.

The study of oxidative stress (OS) phenomena is very relevant for many disciplines including chemistry, biochemistry, physiology and pharmacology. Unfortunately, it is known that no universal test exists for the measurement of OS and different methods should be used for its evaluation in vitro, ex vivo and in vivo. This chapter reviews the recent in vitro methods for the evaluation OS. Firstly, the determination of lipid, protein and DNA oxidation products as biomarkers of exposure to reactive oxygen species (ROS) and how a battery of biomarkers would increase the efficiency and prevent the limitations of a single test which can end up in overestimation as well as underestimations were discussed. In detection of free radicals in biological samples by electron paramagnetic resonance (EPR) part, properties of EPR for the direct detection and identification of free radicals (paramagnetic species) in biological systems were explained. This was followed by the evaluation of fluorescent assays for the detection of ROS and reactive nitrogen species in biological systems. Description of voltammetric methods for low molecular weight antioxidants and significant advantage over the standard spectroscopic tests was discussed. Finally, measurement of OS in bacteria by stating direct and indirect probe-based measurement of the ROS and measurement of the oxidative damage to biomolecules as well as assessment of the antioxidant enzymes activities. This chapter will give an overview of the processes of in vitro methods for the evaluation of OS and touch briefly the most favored methods and techniques.

Structural polymorphism of active pharmaceutical ingredients (APIs) is a common phenomenon being a subject of continuous investigation. Depending on the crystalline or amorphous form, APIs may have different physicochemical properties, including solubility, which ultimately affects the various concentrations of the tested polymorphic forms of the drug in body fluids. Currently, the different scanning calorimetry and X-ray diffraction are the methods of choice in studies of structural polymorphism of drugs. Three vibrational spectroscopic techniques namely: Fouriertransform infrared, Attenuated total reflection and Raman spectroscopy may be indicated as alternative, non-destructive, fast and cheap methods. In addition, the theoretical approach based on quantum-chemical calculations and chemometrics solutions is considered an important support in identification of various polymorphic forms of drugs by determination of positions of bands and their intensities in analyzed samples. In the first part of this chapter, we will focus on description of the differences in the structure of crystalline and amorphous forms of APIs, their pharmaceutical implications and characteristic of vibrational techniques that can be used in studies on polymorphism of drugs. In the second part, we will present the most important examples of the application of the above mentioned vibrational techniques to identify polymorphic and amorphous forms of APIs with different profiles of pharmacological activity and conventional and innovative excipients. Finally, the advantages and limitations of vibrational spectroscopy to study the structural polymorphism of drugs will be indicated and discussed.

Biosensors are a very important subject in the contemporary analytics, mainly in biomedical area. This chapter describes biosensors built with the use of conductive polymers. Conductive polymers provide electrical conductivity of the forming layer, they may function as mediators in red-ox processes and they can enable the immobilization of a biological agent on their surface. Nowadays, in the center of attention are composite materials in which, next to conductive polymers, nanostructured materials such as graphene, carbon nanotubes and quantum dots are applied. In the chapter, the basic modes of biosensors of the first, the second and the third generation, are described. The examples of different enzymatic and affinity biosensors are presented.

Recently, carbon nanotubes (CNT) and graphene have been chosen as electrode material due to their unique mechanical, optical and electrical properties. These carbon-based materials are used to facilitate electrode reaction and produce an electrocatalytic effect. Moreover, a plethora of literature has emerged concerning CNT and graphene being employed to obtain a more selective and sensitive analysis. This chapter reviews this emerging literature focusing on drug analysis from pharmaceutical dosage forms and biological matrices. To achieve this, first, there is a summary of the basic properties, synthesis, characterization, electrode preparation and advantages/limitations of these materials, and then a selection of the literature from 2010 to 2017 is presented, which summarizes the type of electrode, electrochemical techniques, peak potential of drug compounds and the limit of detection values.

Biosensors can combine both modern electronic techniques and selectivity properties of biological or synthetic molecules for the applications in pharmaceutical analyses. Electrochemical biosensors can be defined as analytical devices that are combining receptors such as cells, cell receptors, antibodies, enzymes, microorganism tissues, nucleic acids and DNA or other synthetic compounds with a physicochemical transducer especially electrical/electrochemical-based ones. Electrochemical biosensors are the most used biosensors for analysis of drugs or other analytes in pharmaceutical area being those based on nanomaterials (called also nanobiosensors), the emerging ones in the last decade. Electrochemical biosensors have found an important place due to their high sensitivity, selectivity, and characteristics such as simplicity, the ease of mass production, the low cost and availability of instrumentation. Up to now, various electrochemical technique such as voltammetry; cyclic voltammetry, step and pulse voltammetry, stripping voltammetry, conductometry, potentiometry and mainly amperometry have been used in electrochemical biosensors. In this chapter, electrochemical nanobiosensors employed in pharmaceutical analyses of various pharmacological groups are discussed.

Similarly to the sense of taste or smell, which is derived from triggering multiple different signals in receptors of human tongue or in the nasal cavity, also arrays of cross-reactive sensors give a rise to a characteristic response pattern specific for each different analytes. While the artificial receptors and sensors are rarely selective, the fingerprint-like response pattern is analyte specific and substitutes the sensor selectivity. Thus, the sensing of a particular analyte or a group of analytes using cross-reactive sensor arrays eliminates the need for analyte-specific sensors, which are difficult to design and synthesize. Response patterns from optical sensor arrays can be utilized in the development of low-cost analytical methods suitable for on-site analyses with high sensitivity, which is especially useful in pharmaceutical and biomedical areas that require the detection of very low concentration of analytes in complex biological samples. This chapter focuses on the use of optical sensor arrays in pharmaceutical and biomedical analyses and pattern recognition, and quantitative analysis of the results using chemometric methods.

The ionic liquids are very important solvents in chemical science. These are termed as melts, designer solvents, electrolytes, ionic glasses, fused salts, ionic fluid, and green solvents. The ionic liquids are being used in the different research and industrial areas of chemical science. The most important applications of the ionic liquids in the chemical science include extraction, separation, electro-analysis and spectroscopic studies. This chapter describes the utility of the ionic liquids in the chemical science. Besides, the efforts were made to highlight the toxicity and future of the ionic liquids.

Enantioanalysis became very important in pharmaceutical field due to the different pathways of the enantiomers of the same chiral compound. Therefore, development of reliable methods for enantioanalysis was considered necessary. The utilization of enantioselective electrodes for enantioanalysis simplified enantioanalysis and improved tremendously its reliability. This chapter shows the role and new trends of enantioselective electrodes for pharmaceutical enantioanalysis, the design of these electrodes and their applications in enantioanalysis.