〓〓英語上級者専用　質問スレッド！ Part7〓〓

The followings are excerpts appearing in a scientific paper:

Sample mixes included 5 μl of 10x reaction buffer,
5 to 50 ng of pDDS711 as a double-standed DNA tamplete,
125 ng of each primer, and its complement,
1μl of deoxynucleoside triphosphate (dNTP) mix,
double-distilled water to a final volume of 50 μl, and 2.5 U of Pfu Turbo DNA polymerase,
all overlaid with 50 μl of mineral oil as described in the protocol provided.


Which do you think is the word "included" in the first line, a simple past or a past participle?

(I'd like to presume its simply a past, though a "The" should be added
to the extreme top because "Sample mixes" are all the mixes used in the
experiments...and "included" should be replaced with "contained" preferably.
A "mix" is a sum of the ingredients, NOT an ingredient)