Isocratic chromatography automated

Alexander IV, J.N., Poli J.B., and Markides K.E., Evaluation of automated isocratic and gradient nano-liquid chromatography and capillary electrochromatography, Anal. Chem. 71, 2398, 1999. 

High Performance Liquid Chromatography. Tissue extracts were analyzed with a Varian model 5020 liquid chromatograph equipped with a Rheo-dyne model 7120 loop injector valve, a Tracer 970 variable wavelength detector set at 257 nm, an automated Hewlett-Packard 3385A printer-plotter system for determining retention times and peak areas, and a Waters /x Bondapak column (3.9 mm i.d. X 300 mm) for carbohydrate analysis. The buffer was eluted isocratically at 1 mL/min with a 1 4 (v/v) mixture of 0.01 M monobasic sodium phosphate (pH 4.46) and methanol. The minimum amount detectable was 10 ng. 

Weigmann, H. Hiemke, C. Determination of clozapine and its mqjor metabolites in human serum using automated solid-phase extraction and subsequent isocratic high-performance liquid chromatography with ultraviolet detection. J.Chromatogr, 1992, 583, 209-216... 

Use of Automated Column Chromatography, Isocratic Elution and Differential Refractometry... 

Isocratic elution is preferable in batch mode for the separation of closely related analytes to enhance selectivity and allow automation and short injection cycle. Automated injections provide an opportunity for repetitive unattended operation. In isocratic separations, sample injection is often done before the previously injected product elutes from the column, thus reducing cycle time and solvent consumption (Fig. 2). This technique is especially useful in chiral chromatography, where automated processes are used to decrease the required amount of expensive stationary phases, lowering the overall separation expenses. 

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. 

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