Let R be a ring and $mathcal{Q}$ be a quiver. In this paper we give another definition of purity in the category of quiver representations. Under such definition we prove that the class of all pure injective representations of $mathcal{Q}$ by R-modules is preenveloping. In case $mathcal{Q}$ is a left rooted semi-co-barren quiver and R is left Noetherian, we show that every cotorsion flat representation of $mathcal{Q}$ is pure injective. If, furthermore, R is $n$-perfect and $mathcal{F}$ is a flat representation $mathcal{Q}$, then the pure injective dimension of $mathcal{F}$ is at most $n$.