33 / 71
Pang et al.:
J
ournal of
AOAC I
nternational
V
ol.
98, N
o.
5, 2015
1429
1704 GC/MS/MS results (3.8%), and 57 outlier results
out of 2957 LC/MS/MS results (1.9%), representing
0.98, 0.98, and 0.86%, respectively, of the 6638
results generated in the study. Analysis with the
AOAC statistical software package also confirmed
that the method is rugged, and average recovery,
average concentration, RSD
r
, RSD
R
, and HorRat
values all meet recovery and reproducibility criteria
for use in multiple laboratories. The Study Director is
recommending this method for adoption as an AOAC
First Action
Official Method
SM
.
T
ea is considered to be one of the three most consumed
beverages in the world and is enjoyed by over 2.0 billion
people from more than 160 countries and regions
in the world (1). It is reported that in 2011 alone, more than
50 countries around the globe grew tea, with tea plantation
areas covering about 3.2 million hectares with an annual output
of 4.7 million tons. China, India, Kenya, Sri-Lanka, and Turkey
are the world’s five largest tea producers, and their tea output
makes up about 76% of the total world production (2). Tea
grows mostly in warm temperate zones and subtropical regions
and is subject to threats from diseases and pest infestations, so
pesticides are widely used and hence the potential threat from
pesticide residue contamination. At present, 17 countries and
international organizations, including the Codex Alimentarius
Commission, the European Union (EU), Germany, Holland,
Switzerland, Hungary, Israel, Italy, China, Japan, Korea,
United States, Australia, India, Kenya, and South Africa (until
2006), have established maximum residue limits (MRLs)
for over 800 pesticide residues (3). With growing awareness
of the effect of food contamination on consumer health, an
increasing demand to move to organic farming practices, and
the capability of today’s analytical laboratories to detect lower
and lower levels of contamination in foods, it is imperative that
high throughput multiclass, multianalyte methods be available
to monitor residues of pesticides and other contaminants in
a high-production food like tea. It is for this reason that this
method was developed.
There are over 1000 listed pesticides and chemical
contaminants used around the world for agricultural purposes. In
the early 2000s, the author’s team focused on the development
of sensitive analytical methods and have published a series of
papers (4–9) covering the study of the persistence of between
400 and 500 pesticide residues in 20 agricultural and fishery
products including fruits and vegetables (10, 11), grains (12, 13),
teas (14, 15), Chinese medicinal herbs (16, 17), edible
fungi (mushrooms; 18, 19), animal tissues (20, 21), aquatic
products (22, 23), raw milk and milk powders (24, 25), honey,
fruit juices and fruit wines (26–28), and potable water (29).
Since 2009, the authors have developed analytical methods
for the determination and confirmation of 653 pesticide residues
in tea and used the method to conduct some pivotal studies in an
attempt to obtain a better understanding of the fate, distribution,
and persistence of pesticide residues in tea. The method was
used to conduct:
(
1
)
a 3-month stability study for 460 pesticides in six
different types of solutions
(
2
)
a 3-month stability study for 345 pesticides in tea
(
3
)
a 3-month detection study on deviation ratios of 275
pesticides in Youden paired tea samples
(
4
)
a 3-month study of the ruggedness of the method
(
5
)
a 3-month study on the degradation kinetics for 227
pesticides in aged tea samples
(
6
)
a 3-month verification study of the applicability
of EU performance criteria standard (EU Document
No. SANCO/10684/2009) (30) in an AOAC collaborative study
(
7
)
a 3-month experimental field study on the degradation
patterns and stability of pesticides in incurred tea samples
Most recently (2011–2012), the method was used in a
comparative study to evaluate the influence of tea hydration on
the extraction efficiency of the pesticide multiresidue method
to extract pesticide residues from tea (31). The extensive
research conducted over almost 4 years has generated over
500 000 test results. The research results, at different stages,
were presented and discussed at four AOAC Annual Meetings
from 2009 to 2012, and a series of related papers were
published subsequently (32–35). This AOAC collaborative
study was conducted to complete the requirements for final
consideration under the AOAC
Official Methods
SM
process.
Thirty laboratories from 11 countries and regions participated
in the collaborative study. A total of 560 samples were
analyzed using GC/MS, GC/MS/MS, and/or LC/MS/MS.
Three categories of samples were included: fortified green tea,
fortified oolong tea, aged samples from oolong tea, and incurred
samples from green tea. This paper describes the results of the
collaborative study.
Collaborative Study Protocol
Need/Purpose
The purpose of this collaborative study was to evaluate the
reproducibility of the single-laboratory validated analytical
method for the determination and confirmation of 653 multiclass
pesticide residues in tea and determine whether it meets the
criteria for consideration as an AOAC First Action
Official
Method
.
Scope/Applicability
This method is applicable for the qualitative, quantitative, and
confirmatory analysis of 653 pesticides and chemical pollutant
residues in tea (green tea, black tea, oolong tea, and puer tea).
The LOQs for 490 pesticides determined by GC/MS ranged
between 1.0 and 500 μg/kg and between 0.03 and 4820 μg/kg
for 448 pesticides determined by LC/MS/MS. This method was
also demonstrated to be suitable for the regulatory monitoring
of pesticide residues in tea in some countries where there are
applicable MRLs.
Materials and Matrixes
Design of the validation plan for the multilaboratory
collaborative study:
(a)
Scope of analytes to include in the collaborative
study.
—It would be unimaginably difficult in terms of
resources, time, and personnel for each collaborator to
participate in a collaborative study on a method such as
this one that covers residues of 653 pesticides and chemical