Silica gradient separation

FIG U RE 1.13 Gradient separation of polypeptides on silica rod column and particle-packed columns. Mobile phase velocity 4mm/s, gradient 5%-60% ACN in the presence of TFA, gradient time 5min, columns (a) silica rod column, (b) Capcellpak SG (5 pm), (c) LiChrospher WP 300 RP-18e (5 pm), (d) nonporous NPS-ODS-1 HPLC column (1.5pm) (e) polymer-based TSKgel Octadecyl-NPR (2.5pm). (Reprinted from Minakuchi, H. et al., J. Chromatogr. A, 828, 83, 1998. Copyright 1998, with permission from Elsevier.)... 

E. Step gradient separation—silica cartridge Evaluation... 

HP-NPC can be performed on unmodified silica that separates analytes according to their intrinsic polarity. HP-NPC can also be operated in isocratic, step gradient, or gradient elution mode, where the retaining mobile... 

Figure 6, Gradient separations of PNA s on fused silica 66 cm X 250 m, 5 fjm Vydac 201 TP particles packed column. Mobile phases (A) 65% acetonitrile, 35% water (B) 80% acetonitrile, 207. dimethoxyethane. Sample components (ng injected) 1 naphthalene (20), 2 acenaphthylene (AO), 3 acenaphthlene (20), A fluo-rene (A), 5 phenanthrene (2), 6 anthracene (2), 7 fluoranthene (A), 8 pyrene (2), 9 benz(a)anthracene (2), 10 chrysene (2),...

Figure 2. Gradient separation of Epikote 1001 on a micro packed fused-silica column. Pump Micro Feeder. ColumnrSC-01, 50 cm X 0.22 mm i.d. Mobile phase (A)acetonitrile-water=85 15 (B)acetonitrile-tetrahydrofuran=90 10, gradient profile as indicated. Flow-rate .4 yl/min. Seimple 0.16 yg of Epikote 1001. Wavelength 225 nm. Reproduced with the permission from Ref.7 Copyright 1983, Huethig.

As mentioned in Chapter 3, protein separations typically require specialized columns packed with wide-pore polymer supports or silica materials with extra-low silanol activity. Figure 7.23 shows an example of an RPC gradient separation of a protein mixture using a column packed with Vydac C4 bonded... 

Feng, W. Geng, X. Studies on silica-bonded monoclonal antibody packing material for separation of recombinant interferon by high performance immunoafflnity chromatography. Biomed.Chromatogr., 1993, 7, 317-320 [column was anti-interferon monoclonal antibody bonded to silica gradient]... 

Figure 1 Separations on silica IDA columns with different elution protocols. (A) Isocratic separation of four metal ions on a 100mmX4mm column packed with 5pm IDA silica. Eluent, lOmmoll nitric acid. Detection, PAR postcolumn reaction at 510nm. (Unpublished work, Nesterenko PN and Jones P.) (B) Isocratic separation of five metal ions on a 250 mm x 4 mm column packed with 5 pm IDA silica. Eluent, 0.5 mol I KCI, 20mmoll picolinic acid, and 12.5mmoll" nitric acid. Detection, PAR postcolumn reaction at 510 nm. (Unpublished work, Nesterenko PN and Jones P.) (C) Step gradient separation of Mn(ll), Cd(ll), Co(ll), Zn(ll), and Pb(ll). Eluent conditions 0.1 mol r NaCI (pH 2.6) switched to 0.1 mol 1 NaCI (pH 1.6) at time = 3 min prior to standard injection. Column, 250mm X 4 mm, packed with 8 pm silica IDA. Detection, PAR postcolumn reaction at 495 nm. (Reprinted with permission from Bashir W and Pauli B (2002) Ionic strength, pH and temperature effects upon selectivity for transition and heavy metal ions when using chelation ion chromatography with an iminodiacetic acid bonded silica get column and simple eluents. Journal of Chromatography 942 73-82 Elsevier.)...

New stationary phases were synthesized by binding substituted aromatic groups to silica. Their separation capacity was determined by using various native CDs and CD dal-vatives. The mobile phase for the gradient elution consisted of a mixture of MeCN, H2O, and formic acid. CDs were detected with a refractive index detector and ELSD. The measurements indicated that the N-(4-nitrophenyl)-carbamide group-bonded silica was the most effective. ... 

Separation of C oand C70 can be achieved by HPLC on a dinitroanilinopropyl (DNAP) silica (5pm pore size, 3(X)A pore diameter) column with a gradient from H-hexane to 50% CH2CI2 using a diode array detector at wavelengths 330nm (for C q) and 384nm (for C70). [J Am Chem Soc 113, 2940, 1991.]... 

Protein mixtures were well resolved on poly(aspartic acid)-silica columns using 0.05 mol/1 phosphate buffer, pH 6.0 and a gradient of sodium chloride from 0 to 0.6 mol/1. The columns displayed a high capacity and selectivity. Figure 3 shows the separation of several standard proteins with isoelectric points ranging from 4.7 to over 11. Peaks are sharp and show minimal tailing. The poly(aspartic acid) coating was quite stable the columns lasted for hundreds of hours of use without decrease in efficiency and capacity. 

The submitters mixed active anhydrous silica gel with water (12% v>/w) and stored it in a sealed container for at least 24 hours prior to use. A ratio of 60-80 g. of silica gel per gram of crude product was used for column chromatographic separations, and a column was chosen that would give a 10 1 height diameter ratio of adsorbent. Columns were wet-packed with distilled petroleum ether (b.p. 60-68c), and after the crude product had been applied a step-gradient was run rapidly through 2% vjv ether in petroleum ether, 5% ether, and 10% ether. The column was then eluted with 20% vjv ether in petroleum ether until the bromohydrin acetate was obtained. 

Chromatography. A number of HPLC and TLC methods have been developed for separation and isolation of the brevetoxins. HPLC methods use both C18 reversed-phase and normal-phase silica gel columns (8, 14, 15). Gradient or iso-cratic elutions are employed and detection usually relies upon ultraviolet (UV) absorption in the 208-215-nm range. Both brevetoxin backbone structures possess a UV absorption maximum at 208 nm, corresponding to the enal moeity (16,17). In addition, the PbTx-1 backbone has an absorption shoulder at 215 nm corresponding to the 7-lactone structure. While UV detection is generally sufficient for isolation and purification, it is not sensitive (>1 ppm) enough to detect trace levels of toxins or metabolites. Excellent separations are achieved by silica gel TLC (14, 15, 18-20). Sensitivity (>1 ppm) remains a problem, but flexibility and ease of use continue to make TLC a popular technique. 

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