A Sensitive and Efficient Method for Determination of Capecitabine and Its Five Metabolites in Human Plasma Based on One-Step Liquid-Liquid Extraction

Table 3

Linearity regression parameters of Cap and its five metabolites.

Analytes	Regression type	Regression equations	LLOQ (ng/mL)	Linear range	Weight	r
Cap	Quadratic	Y = −157.20 ∗ x^2 + 198.88 ∗ x + 0.2^a	20.40	20.4–5100.0	1/x^2	0.995
5’-DFCR	Linearity	Y = 77.69 ∗ x − 0.03	20.00	20.0–5000.0	1/x^2	0.997
5’-DFUR	Linearity	Y = 6.57 ∗ x + 1.08	20.40	20.4–5100.0	1/x^2	0.997
2’-DFUR	Linearity	Y = 4.06 ∗ x + 5.82	22.00	20.6–5150.0	1/x^2	0.995
5-FU	Linearity	Y = 9.08 ∗ x + 0.02	20.60	20.6–5150.0	1/x^2	0.993
FUH2	Linearity	Y = 1.55 ∗ x − 4.98	20.20	20.2–5050.0	1/x^2	0.997

^aQuadratic was selected as the upper limit of response approached by Cap in mass spectrometry detection.