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. Author manuscript; available in PMC: 2009 Apr 1.
Published in final edited form as: J Liq Chromatogr Relat Technol. 2008 Jan 1;31(9):1346–1357. doi: 10.1080/10826070802019913

Fig. 2.

Fig. 2

DNP-amino acid separation with a moderately hydrophobic two-phase solvent system by improved spiral tube assembly Experimental conditions: Apparatus: Type-J coil planet centrifuge with 10 cm revolution radius; spiral tube assembly: cross-pressed, radial-groove compressed, and embedded in PEG3500 with 12 spiral layers of 1.6 mm I.D. PTFE (polytetrafluoroethylene) tubing with a total capacity of 100 ml. Each spiral layer consists of 4 spiral channels with a 1.6 cm spiral pitch; solvent system: hexane/ethyl acetate/methanol/0.1M HCl (1:1:1:1, v/v/v/v); samples: DNP-L-glutamic acid, DNP-β-alanine, and DNP-L-alanine each 0.1 mg in 0.1 ml upper phase; Revolution: 800 rpm; detection: 280 nm. SF: retention of stationary phase. Symbols for elution modes are defined in the text.