Table 4 Assay and standard addition results of commercial dietary supplement samples using the proposed HPLC method.

From: Dietary supplement mislabelling: case study on selected slimming products by developing a green isocratic HPLC method for their quality control

 

Compound name

Peak purity

Declared amount (mg/tab or Cap)

Found amount (mg/tab or Cap)c

% of label claim

Standard addition

Purity anglea

Threshold angleb

(% Recoveryd)

SD

Sample 1

Caffeine

1.67

3.34

–

115.55

–

99

2.6

Synephrine

2.88

4.8

–

101.76

–

101.11

2.71

Octopamine

3.9

5.8

–

65.8

–

100.11

2.83

Total blend

  

280

283.11

101.11

  

Sample 2

2-phenethyl amine

4.57

8.57

125

126.9

101.52

99.89

1.87

Caffeine

0.96

2.02

80

77.1

96.4

100.16

1.34

Hordenine

8.79

12.64

15

14.85

99

99.95

2.1

Synephrine

21.69

46.74

1

0.98

98

100.49

2.82

Sample 3

Raspberry ketone

24.64

41.43

8

3.81

47.63

100

2

Caffeine

0.36

1.49

200

206.72

103.36

98.78

0.84

Grape extract (resveratrol)

  

100

N.D

N.D

96.67

0.58

Sample 4

Raspberry ketone

10.96

38.2

150

4.42

2.95

100.33

2.08

Caffeine

3.26

6.04

50

48.84

97.68

101.36

1.82

Resveratrol

13.29

53.13

–

0.8

–

101.44

1.71

  1. aPurity angle compares spectrum of each point in the peak to the peak apex spectrum.
  2. bPurity threshold: solvent angle + noise angle.
  3. cAverage of three determinations.
  4. dAverage of three determinations on three concentration levels.
  5. –Ingredients were labeled as proprietary blends without stating the exact amount of each.
  6. N.D. not detected below LOD.
Back to article page