Perhaps you should try some spelling variations:
pair chromatography » paper chromatography, planar chromatography, layer chromatography
2 chromatography » 7 chromatography, 5 chromatography, 9 chromatography
think pair » thin pair, think fair, things pair

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (( link ((_ chromatography) OR (2 chromatography)) ) OR ( think pair chromatography )).
• Adding a wildcard symbol may retrieve word variants: (( link ((_ chromatography) or (2 chromatography)) ) or ( think pair chromatography ))*.