الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Chapter I: Introduction includes two subsection for two different
types of food contaminants, the first contaminant is Aflatoxin M1 (AFM1) as
one of the almost common in dairy and animal products and the second
contaminant type is phthalates as one the most persistent food contact
materials in food. The introduction detailed with the two food contaminants
types to include sources, chemical and physical properties, toxicity,
occurrence, geographic distribution, legislations, methods of analyses and
surveys.
(2) Chapter II: Includes the experimental part which includes reagents,
reference standard solutions, calibration solutions, equipments, apparatus,
preparation test sample, quality control tools, HPLC/GC components and
conditions, sampling and validation process.
(3) Chapter III: Results and discussion which divided into two parts
according to the two types of contaminants:
The two parts involve the method development and optimization which
includes the following points:
Development of the method extraction technique.
Sample preparation scheme.
Development of the method clean up technique.
Presentation for contaminants chromatograms in standard and
real samples.
Development of the method chromatographic technique.
This part involves also the method validation which is the process used to
confirm that the analytical procedure employed for a specific test is suitable
for its intended use where CODEX guidelines and Eurachem guidelines were
followed in performing the different validation parameters. This part can be
stated in the following points:
Limit of detection (LOD) & Limit of quantitation (LOQ).
The lowest level for AFM1 (nearby the LOQ) measured is found to be
(0.01 μg/kg) and (0.05 μg/kg) for fluid milk and other commodities (powder
milk, cheese, yogurt and egg), respectively. The limit of detection of AFM1
was theoretically estimated and found to be 0.002 and 0.01 μg/kg fluid milk
and other commodities (powder milk, cheese, yogurt and egg), respectively.
The phthalates method LOQ covered the European Union specific migration
limits for phthalates represented in EU directive (EU 10/2011) on plastic
materials and articles intended to come into contact with food. The LOQ
values of phthalates were from 0.125 to 1.25 mg/kg. The Limit of Detection
(LOD) is estimated between 0.018 to 0.200 mg/kg.
Test recovery.
The average recoveries of aflatoxin M1 for milk at levels of
0.01, 0.05 and 0.2 μg/L are varied between 90.9% and 98.7%. The
average recoveries of aflatoxin M1 for other matrices at the three
different levels 0.05, 0.1, and 0.5 μg/kg are varied between 87% and
98%. For phthalates method, the overall average recovery varied between
86.8% and 95.8% at the three different levels 0.125, 0.5, and 15 mg/kg.
Linearity which includes the standard and method linearity.
AFM1 method is linear from the limit of quantification 0.01 up
to 0.2 μg/kg levels for milk and from 0.05 to 0.5 μg/kg for other
matrices. For phthalates, Method linearity was established by the
regression between three average replicates recoveries for the levels of
0.125, 0.5 and 15.0 mg/kg for (DMP, DEP, DIBP, DBP, BBP, DEHP, and
DOP) and 1.25, 5.0 and 25 mg/kg for DIDP. Method was found to be linear
from the limit of quantitations 0.125 up to 15 mg/kg for the first seven
phthalates and 1.25 up to 25 mg/kg for DIDP with a strong correlation
coefficient varied between 0.99947 and 0.9999.
Accuracy (expressed as Trueness).
The two methods for AFM1 and phthalates determination showed
reliable and accurate results located in accepted certified reference material
ranges from FAPAS schemes. The trueness was tested with bias calculations
over three fortification levels and proficiency tests that revealed accepted zscore
ranged between +2 and -2.
Precision (include repeatability and reproducibility).
The two most common precision (repeatability and reproducibility)
determined. For AFM1, repeatability relative standard deviation found to be
4% for fluid milk and for egg was found to be 9%. Within-laboratory
reproducibility was found to be 5% for fluid milk and for egg was found to
be 11%. For phthalates determination, it was found that the repeatability and
reproducibility which were in the average of 10% and 17%, respectively.
Measurement uncertainty.
In estimating the overall uncertainty, it may be necessary to take each
source of uncertainty and treat it separately to obtain the contribution of each
source. Each of the separate contributions to uncertainty is referred to as an
uncertainty component. AFM1 uncertainty was found to be in the range of ±
22.6% for fluid milk and ± 33.0% for other matrices. Phthalates uncertainty
estimated to be ± 52.4%.
The results and discussion ended with the application of proposed
analytical methods into the commercial samples located at the different
districts markets.
The surveillance data on commercial products revealed that AFM1 is
not detected in all 25 egg samples collected from different districts and
yogurt is the least commodity has been contaminated with levels (8% of 25
total samples) exceeding the national ML. The other presented survey of
phthalates revealed that DEHP is the most distributed phthalates compound
in sunflower seed oil and only one sample have been exceeded the European
Union SML for DEHP with concentration (1.610 mg/kg) and there is no
samples exceeding the overall migration limit (60 mg/kg).