Table 2.

Calibration parameters, sensitivity, recovery, accuracy and precision of the optimized LC-QqQ/MS method.

Compound	Calibration range	LLOD (ng/ mL)	LLOQ (ng/ mL)	Linear dynamic range	R2	Spiked amount (ng/ mL)	Accuracy (%)	Precision (%)	Recovery (%)
GA	Low	0.35	1.02	5.100–2040	0.998	200	−3.82	4.38	115 (8.82)
	High			2040–6120	0.995	2000	−17.1	6.53	121 (10.2)
3,4-diHBA	Low	0.62	2.55	2.560–2040	0.998	200	3.31	3.21	92.0 (7.41)
	High			2040–6120	0.999	2000	7.49	3.65	102 (5.32)
3,4-diHPAA	Low	1.23	5.01	2.652–2080	0.999	200	−15.5	8.96	108 (12.0)
	High			2080–6240	0.996	2000	−17.7	4.13	116 (6.34)
4-HBA	Low	0.29	0.97	1.325–1060	0.999	200	–	–	–
	High			1060–6360	0.998	2000	−9.23	4.55	102 (1.87)
( + )-c	Low	0.41	1.32	1.325–1060	0.999	200	4.57	9.69	91.2 (2.78)
	High			1060–6360	0.996	2000	2.89	4.54	95.0 (6.44)
3,4-diHPPA	Low	0.51	2.60	5.204–1040	0.998	200	−8.75	12.2	110 (9.43)
	High			1040–6240	0.997	2000	−20.8	3.16	117 (6.56)
HA	Low	0.42	1.29	2.505–1002	0.999	200	–	–	–
	High			1002–6012	0.998	2000	−3.57	3.77	114 (9.02)
VA	Low	0.75	2.36	2.602–1040	0.999	200	5.82	0.98	104 (2.84)
	High			1040–6240	0.999	2000	2.21	4.05	102 (8.04)
CA	Low	0.25	1.08	2.464–980.1	0.999	200	−11.0	9.55	102 (2.90)
	High			980.1–6020	0.997	2000	−7.81	4.44	108 (4.15)
( − )-EC	Low	0.51	1.60	1.275–1020	0.999	200	12.6	5.81	93.6 (4.59)
	High			1020–6120	0.998	2000	14.3	5.35	91.1 (7.18)
HVA	Low	0.63	1.62	2.700–2160	0.999	200	−3.28	5.90	100 (5.83)
	High			2160–6480	0.999	2000	−6.48	1.58	106 (2.62)
3-HBA	Low	1.25	3.75	2.452–1020	0.999	200	−0.67	5.12	108 (5.42)
	High			1020–6120	0.998	2000	−1.96	2.81	102 (2.25)
3-HPAA	Low	0.74	2.07	2.718–1040	0.999	200	−3.10	4.33	106 (6.78)
	High			1040–6240	0.999	2000	−1.85	1.76	94.6 (4.10)
diHCA	Low	2.05	8.11	10.80–1080	0.997	200	−15.9	4.70	112 (5.45)
	High			1080–6480	0.995	2000	−19.9	2.19	116 (4.73)
p-CA	Low	0.22	0.69	1.245–996	0.999	200	−1.24	1.89	101 (5.14)
	High			996–5976	0.996	2000	−5.74	4.22	100 (3.45)
FA	Low	0.50	1.51	1.374–1080	0.999	200	4.96	4.67	96.6 (5.80)
	High			1080–6480	0.999	2000	6.04	7.84	93.6 (5.15)
3-HPPA	Low	0.31	2.65	5.306–1060	0.999	200	–	–	–
	High			1060–5360	0.998	2000	4.27	3.19	90.2 (4.94)
4-HPVA	Low	0.76	2.61	2.607–1040	0.999	200	6.20	3.40	94.4 (4.13)
	High			1040–5240	0.996	2000	8.25	2.93	96.8 (2.20)
trans-Cinnamic acid-d7 (I.S.)		0.23	0.71	1.272–1018	0.999	–	–	–	–

Data are expressed as means of six independent replicates. Standard deviations for Recoveries (%) were shown in parentheses.

Abbreviations are the same as in Table 1. LLOD, lower limit of detection; LLOQ, lower limit of quantification.

Calibration concentrations were divided into two ranges (low, ca. 1.25–1000 ng/mL and high, ca. 1000–6000 ng/mL), with optimum fit-to-line linear response. Some values for the 200 ng/mL spiked samples were null (−) due to the high response from the amount of the compounds existing endogenously.