Your sentence
Lo+voy+a+comprar.
Words in this sentence
él
he, him, masculine personal third person subject and disjunctive pronoun (used as a subject and after prepositions); it, masculine non-personal third-person subject and disjunctive pronoun (usually used after prepositions to refer to masculine nouns)
Pronoun
ir
to go (away from speaker and listener); to be suitable or apt for its purpose, to match or suit well (of clothing); to head towards or lead to a place away from the speaker; to extend in time or space, from one point to another; to play; to approach or consider (something) from a specific angle, or to direct attention towards a particular goal; denotes an ongoing action with a sense of progression or movement through space or time; to go on (doing something), to carry on, to keep on; an action or process is beginning to occur or unfold; to grow (dark), get (cloudy); used ironically with certain adjectives or passive participles; used with the past participle of reflexive verbs to indicate being in a state caused by the verb; …
Verb
a
to; by; at; Used before words referring to people, pets, or personified objects or places that function as direct objects: personal a.
Preposition