A method for detecting a metabolite in a sample, the method comprising: contacting a sample comprising a metabolite and a compound of Formula or: wherein the metabolite and the compound of Formula or react to form an adduct; and detecting the adduct; wherein: each instance of R 1 and R 2 is independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, -C(=O)R A, -C(=O)OR A,-C(=O)N(R A) 2, or an amino protecting group, or R 1 and R 2 are joined to form a substituted or unsubstituted heterocyclic ring; each instance of R A is independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, an oxygen protecting group when attached to an oxygen atom, or a nitrogen protecting group when attached to a nitrogen atom, or two R A groups are joined to form a substituted or unsubstituted heterocyclic ring; R 3 is hydrogen; R 5 and R 6 are independently selected from -OR B, -N(R B) 2, and a group of Formula (i): provided at least one of R 5 and R 6 is a group of Formula (i); each instance of R B is independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, an oxygen protecting group when attached to an oxygen atom, or a nitrogen protecting group when attached to a nitrogen atom, or two R B groups are joined to form a substituted or unsubstituted heterocyclic ring; each instance of R 4 is independently substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or an amino protecting group, or two R 4 groups are joined to form a substituted or unsubstituted heterocyclic ring; n is 1, 2, 3, 4, 5, or 6; and X - is a counter anion. contacting a sample comprising a metabolite and a compound of Formula or: wherein the metabolite and the compound of Formula or react to form an adduct; and detecting the adduct; each instance of R 1 and R 2 is independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, -C(=O)R A, -C(=O)OR A,-C(=O)N(R A) 2, or an amino protecting group, or R 1 and R 2 are joined to form a substituted or unsubstituted heterocyclic ring; each instance of R A is independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, an oxygen protecting group when attached to an oxygen atom, or a nitrogen protecting group when attached to a nitrogen atom, or two R A groups are joined to form a substituted or unsubstituted heterocyclic ring; R 3 is hydrogen; R 5 and R 6 are independently selected from -OR B, -N(R B) 2, and a group of Formula (i): provided at least one of R 5 and R 6 is a group of Formula (i); each instance of R B is independently hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, an oxygen protecting group when attached to an oxygen atom, or a nitrogen protecting group when attached to a nitrogen atom, or two R B groups are joined to form a substituted or unsubstituted heterocyclic ring; each instance of R 4 is independently substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted carbocyclyl, substituted or unsubstituted heterocyclyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or an amino protecting group, or two R 4 groups are joined to form a substituted or unsubstituted heterocyclic ring; n is 1, 2, 3, 4, 5, or 6; and X - is a counter anion.