I just came across a book about barley-greens, - actually it's more
about dried barley juice (aka Green Magma). It does describe the uses of
chlorophyll and many other constituents of barley juice.
"Green Leaves of Barley: Nature's Miracle Rejuvenator" by Dr Mary Ruth
Swope. (It's not clear whether she is an MD, seems more likely not).
The book is not about growing the sprouts, its more about the benefits
of consuming the juice.
She says that a teaspoon of the powder (2gms) is equivalent to 100gms of
fresh barley leaves.
Note that Green Magma contains small quantities of powdered brown rice
and kelp.

 From a historical perspective, reference is made to the use of
"chlorophyll tablets" and "chlorophyllin" - how these relate to
chlorophyll in fresh juice I do not know. ( When you go into a drug
store/health shop and see bottles of "chlorophyll", its definately NOT
the same, the Magnesium atom has been replaced by Copper, or something
similar. This is to have a stable product, since fresh C~ breaks down
very rapidly.
And another book I have, but haven't relocated yet, is by Dr Yoshihide
Hagiwara: "Green Barley Essence" which describes how he went about
discovering the benefits of chlorophyll, and came to choose Barley.

Lynton