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B
rown
et al
.:
J
ournal of
AOAC I
nternational
V
ol
.
97, N
o
. 5, 2014
1327
Materials tested included treated and nontreated powder and
liquid/juice.
Selectivity
There was adequate resolution (Rs > 2.0) of the aloins from
each other as well as from neighboring eluted compounds.
Linearity
All of the standard curves produced throughout the course of
the study appeared linear upon visual inspection. The coefficients
of determination (r
2
) were ≥99.9%, therefore considered linear
and acceptable for quantifying the aloins in the different test
materials. It should be noted that quantification of the treated test
materials (i.e., low level aloin content) was done using a four-
point calibration curve (i.e., 0.3, 0.5, 1, and 5 µg/mL) since linear
regression does not give equal weight to the calibration points
especially at low levels when a seven-point calibration curve is
used. The r
2
for the four-point calibration curve was ≥99.9%.
Alternatively, a weighted least square calibration curve could
have been used using all seven points, which would produce
results comparable to the four-point calibration curve.
LOD and LOQ
By the IUPAC method, the LODs for aloinA and aloin B were
Table 3. Precision results summary of the test materials
Matrix
Analyte
(Aloin)
HorRat (0.3–2.0)
a
Mean
b
RSDr,
%
TM1 – Inner leaf juice dry powder A
A
<LOD
B
<LOD
TM2 – Inner leaf dry juice powder B
A
1.5
6.62
6.33
B
2.0
6.62
8.64
TM3 – Nondecolorized leaf dry juice powder
A
1.4
26.20
4.89
B
1.8
24.80
6.30
TM4 – Decolorized inner leaf dry juice powder
A
<LOD
B
<LOD
TM5 – Powder capsule
A
1.0
4.73
4.44
B
0.6
4.73
2.74
TM6 – Nondecolorized leaf juice
A
0.3
23335
1.21
B
0.3
23265
1.09
TM7 – Decolorized leaf juice
A
<LOQ
B
<LOQ
TM8 – Nondecolorized inner leaf juice
A
1.3
13889
4.92
B
1.2
14000
4.51
TM9 – Decolorized inner leaf juice concentrate
A
<LOQ
B
<LOQ
a
HorRat values between 0.3 and 2.0 are considered acceptable according to AOAC guidelines for SLVs.
b
µg/g For solid samples and µg/mL for liquid samples.
Table 4. Negative control spike recovery results for aloin A and aloin B in a (a) liquid matrix and (b) solid matrix
Level 1
Level 2
Level 3
Aloin A
Aloin B
Aloin A
Aloin B
Aloin A
Aloin B
(a) Liquid matrix
x
Recovery,
a
%
106.26
95.01
104.74
90.17
105.45
92.70
RSDr, %
4.30
1.83
0.75
0.15
0.84
0.57
(b) Solid matrix
x
Recovery, %
108.86
91.50
100.20
84.41
105.71
88.06
RSDr, %
0.98
3.84
3.17
0.23
1.95
1.81
a
x
= Mean value of three replicate samples.