We recently reported the determination of niacin in
cereals, meat and selected foods by autoclaving the food
with saturated calcium hydroxide solution at 121C for
2 h followed by solid phase extraction (SPE) and using
either capillary electrophoresis (CE) or high performance
liquid chromatography (HPLC) as the determinative
step (Ward & Trenerry, 1997). Under these
conditions, any nicotinamide present in the sample, as
well as the bound niacin, was converted to nicotinic
acid. Solid phase extraction (SPE) with the C18 and
SCX cartridges produced a suitable extract for CE and
HPLC analysis. Nicotinic acid was well separated
from interfering compounds in the resulting electropherograms
and chromatograms. CE was the preferred
technique as the peak shapes were better and the run
times much shorter.
The alkali extraction procedure determined the total
amount of niacin in the food. It is generally considered
that only the acid-hydrolysable forms of niacin are
fully bioavailable for humans; thus if the nutritive
value is to be determined, an acid hydrolysis is preferred.
Also, tryptophan can be converted to niacin in
the body, and therefore the total niacin activity of a
food can be determined only if the contribution of
tryptophan is taken into account (Green®eld & Southgate,
1992).
This paper describes a method for the determination
of niacin in raw and cooked meat and ®sh and a limited
range of other foods using an acid extraction followed
by SPE clean-up and determination by CE. The samples
were also analysed by HPLC using a procedure based
on that described by Tyler and Shrago (1980). Previously
unpublished data on the levels of niacin in fruits