牛奶中萃取前处理检测方案(抽提萃取)
We have utilized an automated acid hydrolysis technology, followed by an abbreviated Soxhlet extraction
technique
to obtain fat from whole milk for the determination of persistent organic pollutants, namely
polychlorinated
dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls. The
process
simply involves (1) pouring the liquid milk into the hydrolysis beaker with reagents and stan-
dards,
(2) drying the obtained fat on a filter paper and (3) obtaining pure fat via the modified Soxhlet
extraction
using 100 mL of hexane per sample. This technique is in contrast to traditional manually intense
liquid-liquid
extractions and avoids the preparatory step of freeze-drying the samples for pressurized
liquid
extractions. Along with these extraction improvements, analytical results closely agree between
the
methods, thus no quality has been compromised. The native spike (n = 12) and internal standard
(n
= 24) precision and accuracy results are within EPA Methods 1613 and 1668 limits. While the median
(n
= 6) Toxic Equivalency Quotient (TEQ) for polychlorinated dibenzo-p-dioxins/polychlorinated diben-
zofurans
and the concentration of the marker polychlorinated biphenyls show a percent difference of 1%
and
12%, respectively, compared to 315 previously analyzed milk samples at the same laboratory using
liquid-liquid
extraction. During our feasibility studies, both egg and fish tissue show substantial promise
using
this technique as well