Fast isocratic methods

Eight BDZs among the most frequently encountered in forensic toxicology (clonazepam, desal-kylflurazepam, diazepam, flunitrazepam, lorazepam, midazolam, nordiazepam and oxazepam) were determined in whole blood after solvent extraction with butyl chloride and fast isocratic separation using a C18 (100 x 4.6 mm x 5 (tm) column [61]. The mobile phase was composed of phosphate buffer (35mM, pH 2.1) and acetonitrile (70 30, v/v) and the flow rate was 2mL/min. Within less than 4 min of analysis time, the analytes could be successfully determined starting from therapeutic concentrations. Using HPLC coupled with APCI-MS-MS, Rivera et al. [62] set up a method for the detection of 18 BDZ and metabolites after butyl chloride extraction at alkaline pH in 0.5mL... 

Final methods are developed for transfer to operational quality control (QC) laboratories for the release testing of production batches. Additionally, the methods are intended to be applied during Registration Stability studies and for the release of the DP or DS validation batches during the pre-approval development stage. The analytical methods should last for the entire product lifetime therefore, the aim of final method development is to generate fast, robust, reliable, and transferable HPLC methods (preferably isocratic and at low cost). 

Guillarme, D. et al., Method transfer for fast liquid chromatography in pharmaceutical analysis Application to short columns packed with small particle. Part I Isocratic separation, Eur. J. Pharm. Biopharm., 66(3), 475, 2007. 

Therefore, if a fast, automated, routine method for the measurement of multi-species/elements is the desired analytical goal, it is often best to attempt an isocratic separation method first, because of the complexity of method development and the low sample throughput of gradient elution methods. In fact, a simultaneous method for the separation of As, Cr, and Se species in drinking water samples was demonstrated by Neubauer and coworkers they developed a method to determine inorganic forms of arsenic (As, As+ ), chromium (Cr , Cr ), and selenium (Se, Se and SeCN ) by reverse-phase ion-pairing chromatography with isocratic elution. Details of the HPLC separation parameters/conditions they used are shown in Table 18.2. 

A sensitive, selective, and fast LC-MS/MS method and a simple sample treatment were proposed for the analysis of amprolium in food samples. Hydrophilic interaction liquid chromatography allowed the retention of this cationic coccidiostat. The method provided an efficient chromatographic analysis in less than 3 min using isocratic elution mode (118). 

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