Patent ID: 9250191
Filing Date: 2016-02-02
CPC Classification: B01D,G01N,Y10T

Claim Text:
1. A method for analysing one or more nitrogen-containing compounds, in which the one or more nitrogen-containing compounds are contacted with hydrindantin at an elevated temperature in a contact zone, the method comprising: contacting ninhydrin with one or more reducing agents in a heating zone for a reaction time in the heating zone at a first elevated temperature to produce a hydrindantin-containing mixture, wherein the ninhydrin and the one or more reducing agents are provided in the form of a ninhydrin reagent, said ninhydrin reagent being essentially free from hydrindantin, the ninhydrin reagent comprising: ninhydrin; an aqueous buffer, the ninhydrin reagent having a pH, wherein the buffer maintains the pH at a value between 4.5 to 5.5; and a temperature-dependent reducing agent present in a concentration, which agent is inactive in the reduction of ninhydrin at a first temperature, wherein the first temperature is no greater than 30° C., and active in reducing ninhydrin to hydrindantin at a second temperature, wherein the second temperature is higher than the first temperature and is at least 100° C., and wherein the second temperature is equal to or greater than said first elevated temperature; and introducing the hydrindantin-containing mixture into the contact zone and contacting the hydrindantin-containing mixture with the nitrogen-containing compounds for a reaction time in the contact zone at a second elevated temperature.