Samples/standards/QC Changes Retention time Response
pH 2.81 COV REC (%) COV4
Camu powder   0.075 102.13 2.42
 ;Tropical juice   0.094 98.94 0.62
Mix berry juice   0.635 96.83 1.90
Pressed orange juice   0.099 102.48 1.42
Distilled water/acetonitrile/formic acid (80.9: 19: 0.1, v/v/v)2
QC (60 µg/mL)   0.33 99.92 0.73
Camu powder   0.12 103.56a 2.03
Onion   4.64 99.47 3.89
Column temperature: 20°C3
Camu powder   0.33 102.61 1.51
10 µg/mL L-AA standard   0.27 100.25 1.09
20 µg/mL L-AA standard   0.20 98.93 2.64
50 µg/mL L-AA standard   0.29 99.44 1.88
100 µg/mL L-AA standard   0.01 97.16 3.08
Column temperature: 26°C
5 µg/mL L-AA standard   0.29 101.31 2.30
20 µg/mL L-AA standard   0.78 97.59 2.97
50 µg/mL L-AA standard   2.13 97.83 2.56
100 µg/mL L-AA standard   0.05 96.06 3.48
125 µg/mL L-AA standard   0.07 97.86 1.34
QC sample (60µg/mL)   0.18 99.83 0.72
camu powder   0.26 101.71 1.00
1Optimized HPLC method at pH 2.6. 2Mobile phase composition for optimized method: distilled water/acetonitrile/formic acid (99: 0.9: 0.1, v/v/v). 3Column temperature of optimized method: 23°C.
4Precision of assay performed at optimal conditions and with variations. aSignificantly (p<0.05) higher recovery obtained with modified mobile phase
Table 4: Evaluation of the robustness of the HPLC method for L-AA determination.