Which preposition to use with impeccable

in Occurrences 3%

The compilations began with the great geographical encyclopaedia of Ku Yen-wu (1613-1682), and attained their climax in the gigantic eighteenth-century encyclopaedia T'u-shu chi-ch'eng, scientifically impeccable in the accuracy of its references to sources.

as Occurrences 1%

Great as he was as sculptor, painter, architect, he was only perfect and impeccable as draughtsman.

Which preposition to use with  impeccable