Philo and canon of Old Testament
Philo Judaeus (c. 20 BC to 50 AD), was Jewish philosopher, writer and a leader of Jewish community in Alexandria, Egypt. As Greek speaking Jew he obviously knew Septuagint or LXX (translation of Jewish Scripture into Greek). Did he already recognize three-fold division of Jewish Scripture (Law, Prophets and Writings) and never quote from deuterocanonical books (this means his copy of LXX did not have deuterocanonical books)? In one of his works Philo wrote about Jewish ascetic sect, Therapeutae. Ascetics are those who dedicate their life to a pursuit of contemplative ideals and practices extreme self denial of worldly pleasure or self-mortification for religious reasons:
And in every house there is a sacred shrine which is called the holy place, and the monastery in which they [Therapeutae] retire by themselves and perform all the mysteries of a holy life, bringing in nothing, neither meat, nor drink, nor anything else which is indispensable towards supplying the necessities of the body, but studying in that place the laws and the sacred oracles of God enunciated by the holy prophets, and hymns, and psalms, and all kinds of other things by reason of which knowledge and piety are increased and brought to perfection.
Philo, On the Contemplative Life, 3(25)
C.D. Yonge: The Works of Philo, Hendrickson Publishers, page 700
What Philo wrote is the practice of a Jewish sect (not that of the Jews in Alexandria) and the text does not give clear evidence they recognized three (or more) divisions of their scripture. While in all his extant works Philo did not quote from deuterocanonical books, neither did he quote from Ezekiel, Song of Songs, Ruth, Lamentation, Ecclesiastes, Esther and Daniel (source: P.R. Ackroyd and C.A. Evans: The Cambridge History of the Bible. From the Beginnings to Jerome, page 148 and The New Schaff-Herzog Encyclopedia of Religious Knowledge, Vol. 2, page 117. Refer also to the scripture index in C.D. Yonge: The Works of Philo, pages 913-918). Note that except Ezekiel the rest belong to the Writings. There is also evidence that Philo quoted other books as attested in his other work:
This is what the lawgiver in one passage says, while declaring the will of God, that, “thou shall complete the number of thy days,” . . . . This is what enigmatically implied in other expressions, where the holy writer says that such a man “shall deserve blessings both at his coming in and going out;” . . .
Philo, On Rewards and Punishments, 19(111,113)
C.D. Yonge: The Works of Philo, Hendrickson Publishers, page 675