Polymeric micelle as the pseudostationary phase in electrokinetic chromatography

A Critical Review of Analytical Methods in Pharmaceutical Matrices for Determination of Corticosteroids

Corticosteroids are a class of hormones released by the adrenal cortex, which includes glucocorticoids and mineralocorticoids. Glucocorticoids have an important role in the metabolism of carbohydrates, proteins and calcium and effective anti-inflammatory and immunosuppressive activity. Due to their intense immunomodulatory and anti-inflammatory activity, glucocorticoids are used in the treatment of various inflammatory, malignant, allergic conditions such as rhinitis, asthma, dermatological, rheumatic, ophthalmic and neurological diseases, as well as after organ transplants. They are the most widely prescribed drugs in the world. The objective of this review is to provide an overview of the analytical methods in pharmaceutical matrices for determination of corticosteroids. In this study, the predominance of liquid chromatography methods for the analysis of corticosteroids from pharmaceutical products is evident for both liquid and semisolid dosage forms as well as for solids. The same can be said for topical, oral and parenteral formulations. Methods such as spectrophotometry are also used, but given the advantages of chromatographic methods such as better selectivity and sensitivity, they have become the choice for analysis of these drugs, however, most methods still do not meet the credentials of "green chemistry."

Evaluation of the enantioselectivity of capillary electrokinetic chromatography using ethanediamine-bonded poly (glycidyl methacrylate) microspheres as the pseudostationary phases

In this work, a new capillary electrokinetic chromatography (EKC) approach using ethanediamine-bonded poly (glycidyl methacrylate) (Ami-PGMA) microspheres as pseudostationary phases (PSPs) for enantioseparation with a polysaccharide, chondroitin sulfate E (CSE), as the chiral selector. The CSE@Ami-PGMA EKC system was applied to enantioseparate basic drugs, and distinct improved separations of tested enantiomers were obtained while comparing with the single CSE system (the resolution increased from 0.41 to 1.26 for nefopam, from 1.24 to 2.15 for laudanosine, and from 0.92 to 2.36 for amlodipine). The Ami-PGMA microspheres were fully characterized by scanning electron microscopy (SEM) and Fourier Transform Infrared (FT-IR) spectroscopy, and the results showed Ami-PGMA microspheres were uniform and spherical in size (1 μm). Several principal parameters were systematically investigated, and the optimal chiral separations were obtained with Tris/H₃ PO₄ (20 mM, pH 2.4, and 3.4 for NEF) containing 2.5% (w/v) CSE and 20-μg Ami-PGMA microspheres in 20°C. Subsequently, the concentrations of Ami-PGMA microspheres and CSE were proved to be the dominant factors for the separation in the CSE@Ami-PGMA EKC system by Statistical Product and Service Solutions (SPSS).

The effects of organic modifier on physicochemical and chromatographic characteristics of self-assembled micelle from poly (stearyl methacrylate-co-methacrylic acid) in electrokinetic chromatography

In our previous work, organic solvents, especially 1-butanol, play a key role to separate highly hydrophobic analytes in EKC using the polymeric micelle self-assembled from amphiphilic random copolymer poly (stearyl methacrylate-co-methyl acrylic acid) (P(SMA-co-MAA)) as a novel pseudostationary phase. Herein, the influences of organic solvents on polymeric micelle physicochemical properties including environmental micropolarity and dimension, as well as chromatographic characteristics containing elution window, hydrophobic selectivity and polar group selectivity were investigated in detail. P(SMA-co-MAA) has extremely low CMC of 1.26 × 10(-6) g/mL, and the self-assembled micelles with selective solvent method had regular spherical structure with diameter about 50 nm. The experimental results showed that methanol, isopropanol or acetonitrile molecules could not penetrate into the interior of the polymeric micelles, and mainly affected the properties of surrounding running buffer. Too much these organic solvents led to elution window narrowed down, methylene selectivity and group selectivity weaken, even the micelles collasped. Whereas, addition of 2% 1-butanol did not influence the elution window, instead, improved the hydrophobic selectivity. Furthermore, both better group selectivity and faster migration for relatively hydrophobic analytes could be achieved simultaneously. It indicated that 1-butanol could insert into the polymeric micelle and 2% 1-butanol was enough to modify the structure of the micelles.

Viscoelastic system from mixing cetyltrimethylammonium bromide and poly(styrene-co-methacrylic acid) in aqueous solution

A viscoelastic system was developed by forming hybrid wormlike micelles with poly(styrene-co-methacrylic acid) (P(St-co-MAA)) and cetyltrimethylammonium bromide (CTAB) in aqueous solution.

Physicochemical and chromatographic characteristics of random amphiphilic copolymer aggregation in electrokinetic chromatography

The random amphiphilic polymeric aggregation, self-assembled from poly (methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)), was explored as a novel pseudostationary phase (PSP) in electrokinetic chromatography (EKC) in our previous report. This work focused on physicochemical characteristics and PSP performances of the polymeric aggregations. The physicochemical characteristics of polymeric aggregations, including critical aggregation concentration (CAC), zeta potential, hydrodynamic diameter, and micropolarity were determined. Experimental results showed that polymeric aggregations had much lower CAC, which decreased the usage of copolymer in EKC, weakened ionic strength and shortened analysis time. The monomer molar ratio of the copolymer was a key factor for physicochemical characteristics and PSP performances of the polymeric aggregations. With the increase of the hydrophobic monomer molar ratio, CAC, micropolarity and dimension of polymeric aggregation decreased significantly while zeta potentials were similar. Correspondingly, separation window enlarged and methylene selectivity evaluated with six kinds of n-alkylphenone homologous series enhanced. Linear solvation energy relationships (LSER) analysis found that hydrophobic interaction is the most important interaction between analytes and polymeric PSPs. Compared with SDS micelle, polymeric aggregations owned more types of interactions, such as stronger hydrogen bonding and relative larger dipole interaction, which provided a bigger adjustment room to improve PSP selectivity.