Poly(ethyleneglycol) column for the determination of acetaminophen,phenylephrine and chlorpheniramine in pharmaceutical formulations

New polar reversed-phase stationary phases in HPLC provide specific selectivities which can help to solve traditional chromatographic problems related to the development of chromatographic methods with widely different retention times for the sample components. One such case is the analysis of pharmaceutical formulations against the common cold. Acetaminophen, phenylephrine and chlorpheniramine, compounds with different polarities, are frequently associated in these drugs. An isocratic and rapid HPLC method for the simultaneous determination of the three compounds, acetaminophen, phenylephrine and chlorpheniramine, in capsules as pharmaceutical formulations, including the separation of impurities (4-aminophenol and 4-chloracetanilide) and excipients, has been developed and validated. The final chromatographic conditions employed a Supelco Discovery HS PEG column poly(ethyleneglycol) 15x0.46 cm, 5 microm. The mobile phase was 20 mM phosphate buffer, pH 7.0-acetonitrile (90:10, v/v) at a flow-rate of 1 ml/min. UV detection was performed at 215 nm for all the compounds except acetaminophen, which was measured at 310 nm. Validation parameters permit us to consider this method suitable.     

High-performance thin-layer chromatographic separation of ranitidine hydrochloride and two related compounds

Ranitidine hydrochloride and its two related compounds, used in the USP TLC purity testing of the drug, were separated on a high-performance thin-layer chromatography (HPTLC) RP-18 WF_254S precoated plate using methanol–3% NH₄OH (4:1, v/v) as the mobile phase. The main advantage of the proposed HPTLC system over the USP TLC system for testing the purity of ranitidine is a better and more efficient separation of these three compounds in a shorter time and with less consumption of solvents. The system is promising from the point of view of the development of a new method for the TLC purity testing of ranitidine hydrochloride. A video system was used for imaging thin-layer chromatograms. Direct UV densitometric quantitation of the three compounds and a model for the calculation of analytical performance parameters is presented in the second part of the paper.     

Rapid group separations of nucleotides and related compounds on silica columns

Nucleosides, bases, and nucleotides can be separated from one another rapidly (10–15 min) on 1-ml silica cartridges. Samples adjusted to 4 mm ammonium borate, 90% acetonitrile are loaded onto 1-ml columns equilibrated with the same solvent. Bases do not absorb to the silica under these conditions. Nucleosides are eluted with 16 ml of 0.5 m acetic acid in 90% acetonitrile. Nucleotides are then eluted with water. The 1-ml silica columns have performed well with samples up to 10 ml in volume. We have found the procedure to be quantitative and the gels to have high capacity (61 μmol Cyd/ml silica). Acid extracts from a large number of cells (10⁸) have been processed on a single cartridge.     

The separation of nucleic acids and related compounds on nucleobase-coupled cellulose

The affinity chromatography on uracil-coupled cellulose was carried out for the separation of nucleosides, nucleotides and oligonucleotides. Adenine derivatives exhibited a high affinity to uracil-cellulose, and sequencial isomers of oligonucleotides containing adenine residue were resolved. Poly(A) was strongly bound to uracil-cellulose and recovered by the elution with 7M urea. This procedure was extended to the isolation of mRNA containing poly(A) sequences.     

Chromatographic separation of vitamins D2 and D3 and related compounds

A reversed-phase chromatographic system is described that is capable of separating vitamin D₂ from vitamin D₃ and ergosterol from 7-dehydro-cholesterol and cholesterol. The method uses Factice, a polymerized and vulcanized soybean oil, as stationary phase and a water/acetone mitxure as mobile phase. In contrast to other previously published techniques capable of separating vitamins D₂ and D₃, the present separation is accomplished without any chemical modification or alteration of the D-vitamins.     

Optimized reverse-phase high-performance liquid chromatographic separation of cinnamic acids and related compounds.

The effect of mobile-phase pH on reverse-phase high-performance liquid chromatographicseparation is studied for a nine-component sample containing cinnamic, ferulic, hydrocinnamic, p-coumaric, caffeic, phenylacetic, vanillic, and β-phenylpyruvic acids and phenylethylamine. A systematic optimization strategy is utilized: Retention times of each component are measured for mobile phases buffered with citric acid at pH's of 3.0, 4.0, 5.0, and 6.0; a mathematical model is fit to the chromatographic data; the model parameters are used to construct a window diagram which provides an estimate of the mobile-phase pH required for optimum separation.     

Chiral HPLC separation and CD spectra of the enantiomers of the alkaloid tacamonine and related compounds.

The HPLC enantiomeric separation of racemic indole alkaloids tacamonine, 17 alpha-hydroxytacamonine, deethyleburnamonine, and vindeburnol was accomplished using Chiralpak AD and Chiralcel OD as chiral stationary phases. Small structural differences affect the enantioselectivity ability of these phases. Single enantiomers of tacamonine and vindeburnol were isolated by semipreparative HPLC and their CD spectra and optical rotations were measured.     

New approaches to synthetic receptors. Studies on the synthesis and properties of macrocyclic C-glycosyl compounds as chiral,water-soluble cyclophanes

In an approach for the preparation of macrocyclic C-glycosyl compounds, the C-glycosyl residue is synthesized by acid-assisted reduction of a cyclic hemiacetal with sodium cyanoborohydride. Macrocycle formation is effected by the reaction of a symmetrical bis(C-glycosyl)derived diamine with a dicarboxylic acid dichloride. The product macrocycles are presented as the first examples of a new type of chiral, water-soluble cyclophane. Molecules of this type are of interest as synthetic receptors for lipophilic substrates.     

Effect of elution modes on protein separation by cross-axis coil planet centrifuge with two different types of coiled columns

Effect of elution modes on protein separation was investigated using cross-axis coil planet centrifuge (cross-axis CPC) with two different types of coiled columns, i.e., eccentric coil and toroidal coil assemblies. Myoglobin and lysozyme were separated with an aqueous two-phase solvent system composed of 12.5% (w/w) polyethylene glycol 1000 and 12.5% (w/w) dibasic potassium phosphate. The substantial effect of elution modes was observed by the toroidal coil, while the negative result was given at the eccentric coil. Using the toroidal coil, higher peak resolution of proteins was attained at the tail to head elution mode. In the outward lower phase mobile elution mode, the satisfactory separation was obtained by both eccentric coil and toroidal coil assemblies. However, in the inward upper phase mobile elution mode, the toroidal coil produced a broad and asymmetric myoglobin peak. The analysis using polyacrylamide gel electrophoresis revealed that the toroidal coil partially separated the components originally present in the myoglobin sample. As the result, a modified equation was devised to express the peak resolution (Rs) using the lysozyme peak. The overall results indicated that the toroidal coil produced better partition efficiency than the eccentric coil under the optimized experimental condition including the direction of the Coriolis force acting on the mobile phase in the toroidal coil.     

New approaches to the problem of generating coherent,reproducible phenotypes

Fundamental, unresolved questions in biology include how a bacterium generates coherent phenotypes, how a population of bacteria generates a coherent set of such phenotypes, how the cell cycle is regulated and how life arose. To try to help answer these questions, we have developed the concepts of hyperstructures, competitive coherence and life on the scales of equilibria. Hyperstructures are large assemblies of macromolecules that perform functions. Competitive coherence describes the way in which organisations such as cells select a subset of their constituents to be active in determining their behaviour; this selection results from a competition between a process that is responsible for a historical coherence and another process responsible for coherence with the current environment. Life on the scales of equilibria describes how bacteria depend on the cell cycle to negotiate phenotype space and, in particular, to satisfy the conflicting constraints of having to grow in favourable conditions so as to reproduce yet not grow in hostile conditions so as to survive. Both competitive coherence and life on the scales deal with the problem of reconciling conflicting constraints. Here, we bring together these concepts in the common framework of hyperstructures and make predictions that may be tested using a learning program, Coco, and secondary ion mass spectrometry.     

New approaches to the treatment of osteoporosis

Under physiological conditions, maintenance of skeletal mass is the result of a tightly coupled process of bone formation and bone resorption. Disease states, osteoporosis included, arise when this delicate balance is disrupted such as in menopause, when estrogen levels decrease dramatically corresponding with the cessation of ovarian function. Current therapies for the treatment of osteoporosis, including estrogen replacement therapy, selective estrogen receptor modulators and bisphosphonates, are primarily based on blunting the resorption component of bone homeostasis. Although selective estrogen receptor modulators offer bone protection without the side effects of estrogen replacement therapy, there are some areas of improvement for the current generation of selective estrogen receptor modulators; particularly in reducing their antagonistic properties in the central nervous system that lead to vasomotor symptoms. There are few therapies that are focused on increasing bone formation, but they offer promising avenues in which to expand the repertoire of drugs to restore bone mass. Selective androgen receptor modulators, parathyroid hormone analogs, oxytocin analogs and statins, all with improved pharmacological properties in bone, are among the potential approaches to eliciting anabolic effects in the skeleton.     

Inhibition of the puromycin reaction with benzamidine and related compounds

Incubation of mouse cells with N-methyl-N′-nitro-N-nitrosoguanidine causes a strong inhibition of DNA replication the extent of which varies with the cell line used. Analysis of the products synthesized in drug-treated cells indicates a particularly severe effect on the joining of replicons while other steps in DNA synthesis like initiation and chain elongation are much less affected. The data indicate that replicon fusion may be extremely sensitive to changes in the topology of DNA induced by the introduction of rare single-strand breaks during repair of N-methylated purines produced by incubation of cells with small amounts of the methylating agent