Abstract: A method for analyzing one or more nitrogen-containing compounds is disclosed. In the method, a ninhydrin-containing composition is irradiated with UV light in an activation zone to produce a ninhydrin reagent containing hydrindantin. The ninhydrin reagent is passed to a reaction zone. In the reaction zone the ninhydrin reagent is contacted with the nitrogen-containing compounds.

Abstract: A method for preparing a ninhydrin reagent for use in the analysis of nitrogen-containing compounds is provided, the method comprising irradiating a ninhydrin-containing composition with UV light. An apparatus for preparing a ninhydrin reagent for use in the analysis of nitrogen-containing compounds is also provided, the apparatus comprising a conduit having an inlet for receiving a ninhydrin-containing composition and an outlet for discharging a ninhydrin reagent; and a light source for irradiating the ninhydrin-containing composition within the conduit with UV light. A method for analysing one or more nitrogen-containing compounds comprises irradiating a ninhydrin-containing composition with UV light in an activation zone to produce a ninhydrin reagent; and contacting the ninhydrin reagent with the nitrogen-containing compounds in a reaction zone.

Abstract: A method for analyzing 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 is provided. In the method ninhydrin is contacted with one or more reducing agents in a heating zone at a first elevated temperature to produce a hydrindantin-containing mixture. The hydrindantin-containing mixture is introduced into the contact zone and contacted with the nitrogen-containing compounds at a second elevated temperature. The method is particularly suitable for the analysis by visualization of amino acids.

Abstract: A ninhydrin reagent for use in a method for analyzing nitrogen-containing compounds, in particular visualizing nitrogen-containing compounds by a color forming reaction, is provided. The ninhydrin reagent contains ninhydrin; an aqueous buffer; and a temperature-dependent reducing agent, which agent is inactive in the reduction of ninhydrin at a first temperature and active in reducing ninhydrin to hydrindantin at a second temperature, wherein the second temperature is higher than the first temperature. The reagent is particularly useful in the analysis of amino acids.

Abstract: 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 is provided, the method comprising contacting ninhydrin with one or more reducing agents in a heating zone at a first elevated temperature to produce a hydrindantin-containing mixture; and introducing the hydrindantin-containing mixture into the contact zone and contacting the hydrindantin-containing mixture with the nitrogen-containing compounds at a second elevated temperature. The method is particularly suitable for the analysis by visualisation of amino acids.

Abstract: A ninhydrin reagent for use in a method for analysing nitrogen-containing compounds, in particular visualising nitrogen-containing compounds by a colour forming reaction, is provided, the ninhydrin reagent comprising ninhydrin; an aqueous buffer; and a temperature-dependent reducing agent, which agent is inactive in the reduction of ninhydrin at a first temperature and active in reducing ninhydrin to hydrindantin at a second temperature, wherein the second temperature is higher than the first temperature. The reagent is particularly useful in the analysis of amino acids.