Ninhydrin-type sorbent obtainable by a method for producing a ninhydrin-type sorbent, the method comprising the steps of: i) providing a monomer of general formula: wherein the monomers of general formula is of general formula (li), of general formula (Ip), or of general formula (In) wherein: Q is -H or -CH 3; h' and h" are each independently absent or chosen from a halogen and -H; X' and X" are each independently chosen from a halogen, -H, =O, =N-(CH 2) n -H, - O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -(CH 2) n -H, and -N(-[CH 2] n -H) 2, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, R' and R" are each independently chosen from a halogen, -H, -OH, -O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -N(-[CH 2] n H) 2, and -(CH 2) n -H, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, or wherein R' and R" together form a bridging moiety selected from -CH 2 -, =CH-, -C(=O)-, -C(-OH) 2 -, -C(-OH) 2 -C(-OH) 2 -, -O-, -NH-, and -C(h′′′)(X′′′)-, wherein h′′′ is independently chosen as defined for h' or is -NH-C(=O)-NH 2; X′′′ is independently chosen as defined for X'; or wherein X′′′ is -OH and h′′′ and one of h' or h" together form a bridging moiety -NH-C(=O)-NH-; ii) polymerizing the provided monomer to obtain a polymer; and iii) converting polymerized monomers of general formula that are not ninhydrin-type monomers into ninhydrin-type monomers, wherein the sorbent has a urea binding capacity of more than 2.20 mmol urea per gram of sorbent, wherein the urea binding capacity is the capacity that can be determined after incubation of a sorbent with an excess of urea in a solution at 70 °C for 24 hours. i) providing a monomer of general formula: wherein the monomers of general formula is of general formula (li), of general formula (Ip), or of general formula (In) wherein: Q is -H or -CH 3; h' and h" are each independently absent or chosen from a halogen and -H; X' and X" are each independently chosen from a halogen, -H, =O, =N-(CH 2) n -H, - O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -(CH 2) n -H, and -N(-[CH 2] n -H) 2, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, R' and R" are each independently chosen from a halogen, -H, -OH, -O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -N(-[CH 2] n H) 2, and -(CH 2) n -H, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, or wherein R' and R" together form a bridging moiety selected from -CH 2 -, =CH-, -C(=O)-, -C(-OH) 2 -, -C(-OH) 2 -C(-OH) 2 -, -O-, -NH-, and -C(h′′′)(X′′′)-, wherein h′′′ is independently chosen as defined for h' or is -NH-C(=O)-NH 2; X′′′ is independently chosen as defined for X'; or wherein X′′′ is -OH and h′′′ and one of h' or h" together form a bridging moiety -NH-C(=O)-NH-; wherein the monomers of general formula is of general formula (li), of general formula (Ip), or of general formula (In) wherein: Q is -H or -CH 3; h' and h" are each independently absent or chosen from a halogen and -H; X' and X" are each independently chosen from a halogen, -H, =O, =N-(CH 2) n -H, - O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -(CH 2) n -H, and -N(-[CH 2] n -H) 2, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, R' and R" are each independently chosen from a halogen, -H, -OH, -O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -N(-[CH 2] n H) 2, and -(CH 2) n -H, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, or wherein R' and R" together form a bridging moiety selected from -CH 2 -, =CH-, -C(=O)-, -C(-OH) 2 -, -C(-OH) 2 -C(-OH) 2 -, -O-, -NH-, and -C(h′′′)(X′′′)-, wherein h′′′ is independently chosen as defined for h' or is -NH-C(=O)-NH 2; X′′′ is independently chosen as defined for X'; or wherein X′′′ is -OH and h′′′ and one of h' or h" together form a bridging moiety -NH-C(=O)-NH-; Q is -H or -CH 3; h' and h" are each independently absent or chosen from a halogen and -H; X' and X" are each independently chosen from a halogen, -H, =O, =N-(CH 2) n -H, - O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -(CH 2) n -H, and -N(-[CH 2] n -H) 2, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, R' and R" are each independently chosen from a halogen, -H, -OH, -O-(CH 2) n -H, -O-C(CH 3) 3, -O-CH(CH 3) 2, -N(-[CH 2] n H) 2, and -(CH 2) n -H, wherein any -H may be optionally replaced by a halogen, wherein each instance of n is independently chosen from 0, 1, 2, 3, or 4, or wherein R' and R" together form a bridging moiety selected from -CH 2 -, =CH-, -C(=O)-, -C(-OH) 2 -, -C(-OH) 2 -C(-OH) 2 -, -O-, -NH-, and -C(h′′′)(X′′′)-, wherein h′′′ is independently chosen as defined for h' or is -NH-C(=O)-NH 2; X′′′ is independently chosen as defined for X'; or wherein X′′′ is -OH and h′′′ and one of h' or h" together form a bridging moiety -NH-C(=O)-NH-; ii) polymerizing the provided monomer to obtain a polymer; and iii) converting polymerized monomers of general formula that are not ninhydrin-type monomers into ninhydrin-type monomers,