Slurry packing reproducibility

Figure 4.9 Up-fill slurry packing apparatus. (Reproduced with perslssion from Micromeritics Instruments Coirp.)...

AA and IAA simultaneously Orange juice Filtration to remove suspended material dilution with 1% acetic acid Analytical Phenylpropanolamine-coated silica (150 X 4.6 mm, 5 fim slurry-packed in-house). Isocratic methanol + 1 % acetic acid (70 + 30 v/v). 1.0 ml/min. UV absorbance 244 nm. External standardization. Linear range = 7-28 /zg/ml (r = 0.998). Reproducibility CV 3.77% (n = 5). 

Fig. 7.6. Capacity factor as a function of reversed phase chain length in methanol-water (60 40). Chromatographic conditions columns, all columns (300 mm X 4.6 mm I.D.) were slurry packed with bonded phases attached to 10 ftm SI 100 silica particles mobile phase, methanol-water (60 40) temperature, 27.5 C detection, refractive index. Reproduced from Berendsen and De Galan (1980), with permission...

Wu et al. described the design of injection valves and separation reproducibility, and the use of a carbon dioxide-enhanced slurry packing method on the capillary scale for the separation of some benzodiazepines, herbicides, and various pharmaceutical compounds [43,50]. Tolley et al. modified a commercially available HPLC system to operate at 17,500 psi and used 22 cm long capillaries packed with 1.5 pm... 

For example for the preparation of a 15 cm long, 4.6 mm i.d. stainless tube column, 2.5 g of octadecyl-bonded silica gel was suspended in 25 ml of hexanol-methanol mixture, and kept in an ultrasonic bath for a few minutes to remove air. After the reservoir was filled with the slurry, methanol was pumped in at 10 ml min -1 under constant pressure, 45 MPa (450 bar). After the replacement of slurry solvent by methanol, the flow was stopped and the pressure allowed to drop. When 0 MPa was reached the reservoir was removed. Then, 20 ml of water was added and methanol was again pumped in under the same conditions as before. Again, the flow was stopped and the pressure allowed to drop until it reached 0 MPa. The pre-column was removed and the analytical column closed. The maximum pressure that can be applied in the filling stage is based on the pore size, particle shape, and purity of the silica gel. This reproducible packing procedure is performed at constant temperature by using a water bath (60-BO °C). 

Reproducibility during column preparation is a significant problem in CEC. Preparation methods involving pumped slurries were all found to produce generally highly efficient (> 200,000 plates/m for 3-pm ODS particles), but within a batch of columns packed by the same method, the relative standard deviation (RSD) of EOF, and migration time and retention factor of a standard were [23], respectively, 7-14%, 5-22%, and 9-30%. These values are particularly relevant to considerations of the transfer of HPLC methods to CEC. 

The separation columns are fabricated from standard type 316 stainless steel tubing that is either 0.22 or 0.62 cm ID (depending upon whether it is an advanced miniaturized system or an earlier model) and 150 cm long. A 1 in. OD stainless steel heating jacket surrounds the column. The ion exchange resin is packed into the column as a thick slurry using a dynamic loading technique which provides reproducible... 

The rapid development of HPLC columns for example was due to three major technical achievements the ability to manufacture micro-particulate silicas, the invention of air elutriation technique as sizing technology and progress in the slurry technique for packing HPLC columns. However, it took more than ten years to build up sufficient know-how to produce stable, robust and reproducible HPLC columns that satisfied the continuously increasing demands of the chemical and pharmaceutical industry (Fig. 1.2). 

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