NACALAI TESQUE, INC.

COSMOSIL NPE column is a reversed phase column with nitrophenylethyl groups bonded silica packing material. This column provides unique retention characteristics, slightly different from the COSMOSIL PYE column, utilizing both dipole-dipole and π-π interactions.

Selectivity for Dipole

Selectivity for dipole is evaluated based on the separation of 1,5-dinitronaphthalene and 1,8-dinitronaphthalene. Dinitronaphthalenes (peak 1 and 2) were strongly retained on PYE and NPE because of π-π interaction compared with dimethylnaphthalenes. However, there is a slight difference between these two columns. While 1,5-dinitronaphthalene (peak 2) was preferentially retained on PYE, 1,8-dinitronaphthalene (peak 1) was retained longer on NPE. The results with NPE indicate the presence of strong dipole-dipole interaction. The two nitro group dipoles in 1,8-dinitronaphthalene are aligned for a much greater dipolar coupling with the bonded nitrophenyl group in NPE than 1,5-dinitronaphthalene.

Condition
Column Size	4.6 mm I.D. x 150 mm
Mobile Phase	5NPE Methanol : Water = 70 : 30 5PYE Methanol : Water = 90 : 10 5C18-MS-II Methanol : Water = 80 : 20
Flow Rate	1.0 ml/min
Temperature	30°C
Detection	UV 254 nm
Sample	1,8-Dinitronaphthalene 0.21 µg 1,5-Dinitronaphthalene 0.11 µg Naphthalene 0.25 µg 1-Methylnaphthalene 0.35 µg 1,5-Dimethylnaphthalene 0.42 µg

Attention

1. Methanol is recommended as a mobile phase for COSMOSIL NPE column. Acetonitrile is not recommended because it has many π electrons and interferes π-π interactions between a sample and the stationary phase.
2. The stationary phase of COSMOSIL NPE, nitrophenyl group, has a large UV absorption. When the stationary phase detaches from silica gel and elutes, even a slight quantity can be detected and causes baseline noise. In such a case, wash the column with tetrahydrofuran. Detachment of a small amount of the stationary phase does not deteriorate a column?s separation ability.
3. COSMOSIL NPE column is not suitable for gradient analysis.