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|Inner Diameter||4.6 mm|
|Particle Size||5.0 µm|
|Product Brand Name||Quasar|
In recent years there has been an increase in interest regarding 'AQ' columns due to their ability to retain polar analytes reproducibly under high aqueous conditions and with no phase collapse as a traditional C18 column would exhibit. There are two general approaches to the bonded phase chemistry of AQ columns. The first is to employ a polar or hydrophilic end-capping. The second method is to incorporate polar-embedded groups within the alkyl chains. These two methods provide a high degree of polar character to the final alkyl bonded phase, allowing full interaction with the alkyl chains upon wetting the silica surface with water. Additionally, the added polar functionality introduces a secondary separation mechanism (dipole-dipole interactions) to facilitate alternative selectivity for polar compounds. This application brief describes the use of Quasar™ C18, AQ and AQ Plus columns for the analysis of polar compounds, outlining the benefits of stationary phases offering alternative selectivity.
The aerobic mold which yielded cephalosporin C was found in the sea near a sewage outfall nearby Cagliari harbour, Sardinia, by the Italian pharmacologist Giuseppe Brotzu in July 1945. Since their discovery and subsequent commercialization in 1964, the cephalosporins today are broad-spectrum ß-lactam antibiotics used for the treatment of a number of bacterial conditions including septicaemia, pneumonia and meningitis. The pharmacology of cephalosporins is similar to that of the penicillin class of compounds. This application brief describes use of a Quasar biphenyl column in the analysis of several cephalosporins, a mixture of first and second generation ß-lactam antibiotics.
Indoxyl sulfate is one of the most extensively studied solutes that accumulates in the plasma when the kidneys fail. Originally called "indican", it was first isolated by Obermayer and Popper in 1911. High concentrations of indoxyl sulfate in blood plasma are known to be associated with the development and progression of a number of pathological conditions including chronic kidney disease and vascular disease. The scientific literature documents the use of older generation C18 columns, using type A silicas. This application brief will illustrate the application of a new generation C18 column, based on type B silica, for the analysis of indoxyl sulfate, Figure 1, as part of a research study to measure the total levels in a simulated blood serum environment.
Today, Warfarin is the most widely used anticoagulant in the world, used to thin the blood and prevent clots.1 It was discovered by chance when in the 1920’s cattle in the US were found to be bleeding to death having eaten mouldy hay from sweet clover crops.2 However, the exact identity of the substance causing the haemorrhaging was to remain unknown for many years. Over the coming years studies of the spoiled hay eventually led to the extraction of a compound which was later named dicoumarol. It was observed that this dicoumarol could not act as an anticoagulant on its own. It was only after it was metabolised byfungi that it exhibited anticoagulant properties. This explained why only spoiled hay caused the outbreak in the cattle. After further research, the synthesis of a more potent anticoagulant from dicoumarol, warfarin, was produced. Warfarin first commercial use was as a rat poison in 1948, followed by license for human use in 1953. This application brief illustrates the analysis of warfarin, Figure 1, using the Quasar AQ liquid chromatography phase.
Salbutamol (also known as albuterol) is a bronchodilating agent which is ubiquitously used in the treatment of asthma and chronic obstructive pulmonary disorder (COPD). It is a polar hydrophilic compound (see Figure 1) which can be problematic when analyzing using reverse phase HPLC. Polar compounds can elute very close to the solvent front. It is therefore ideal for an eluting compound to have a capacity factor (k) between 1 and 10. Polar compounds with poor retention can have k values close to zero. Analyses with this level of retention are not reproducible and so it is important to increase the affinity that polar compounds have for the stationary phase. The technical note investigates the impact on retention of salbutamol by changing the chemistry of the stationary phase. When analyzing salbutamol in accordance with the British Pharmacopeia, the monograph stipulates the use of 'end-capped octadecylsilyl silica gel for chromatography (5 µm)'. This definition does not specify the type of end capping giving scope to the evaluation of different stationary phase whilst still adhering to BP requirements. Salbutamol sulfate was analyzed according to the British Pharmacopeia monograph: Salbutamol Pressurised Inhalation, Suspension. This analysis was performed on four Quasar columns: C18, AQ, AQ Plus and SPP C18/PFP in order to obtain the maximum improvement in the retention of salbutamol.