Table 2.
Sensitivity and linearity of LC-MS MRM assay
| No. | Analyte | LOD (nM) | LOQ (nM) | Regression Line | R2 | Linear Range (nM) | Inter CV (%) | Intra CV (%) |
|---|---|---|---|---|---|---|---|---|
| 1 | Acetic acid | 0.5 | 1.5 | y = 1.13938e−4x + 0.01727 | 0.99842 | 12–6,250 | 6.1 | 8.0 |
| 2 | Propionic acid | 1.5 | 5.0 | y = 1.91767e−4x + 0.00564 | 0.99846 | 10–12,500 | 5.1 | 6.4 |
| 3 | Isobutyric acid | 1.5 | 4.0 | y = 2.97287e−4x + 0.01146 | 0.99848 | 5–6,250 | 1.4 | 5.4 |
| 4 | n-Butyric acid | 0.5 | 2.0 | y = 4.35691e−5x + 0.01852 | 0.99436 | 5–25,000 | 5.2 | 5.0 |
| 5 | n-Valeric acid | 0.5 | 1.5 | y = 1.46422e−4x + 0.02935 | 0.99374 | 5–6,250 | 2.9 | 3.0 |
| 6 | Isovaleric acid | 3.0 | 5.0 | y = 2.07072e−4x − 0.00303 | 0.99654 | 5–12,500 | 2.1 | 3.5 |
| 7 | 2-Methylbutyric acid | 0.5 | 2.0 | y = 2.80818e−4x + 0.04874 | 0.99846 | 5–25,000 | 7.5 | 8.1 |
| 8 | 2-Methylvaleric acid | 3.0 | 5.0 | y = 9.89105e−5x + 0.01038 | 0.99559 | 10–12,500 | 2.2 | 8.7 |
| 9 | 3-Methylvaleric acid | 2.0 | 5.0 | y = 4.94699e−5x + 0.00142 | 0.99892 | 5–6,250 | 3.2 | 5.5 |
| 10 | 4-Methylvaleric acid | 0.5 | 1.5 | y = 1.54437e−4x + 0.00749 | 0.99805 | 2.5–6,250 | 6.4 | 5.2 |
| 11 | Pivalic acid | 0.5 | 2.0 | y = 2.78603e−4x − 0.00476 | 0.99929 | 5–6,250 | 5.0 | 3.1 |
| 12 | 2-Ethylbutyric acid | 2.5 | 6.0 | y = 1.78141e−4x − 0.03671 | 0.99853 | 5–25,000 | 2.1 | 3.0 |
| 13 | 2,2-Dimethylbutyric acid | 3.0 | 6.0 | y = 4.47025e−5x − 0.01838 | 0.99649 | 10–25,000 | 2.7 | 2.5 |
| 14 | 3,3-Dimethylbutyric acid | 2.0 | 5.0 | y = 6.32423e−5x − 0.00411 | 0.99895 | 5–25,000 | 3.4 | 1.8 |
| 15 | Hexanoic acid | 1.0 | 3.0 | y = 1.99559e−4x + 0.00403 | 0.99917 | 5–6,250 | 6.2 | 1.2 |
y = area ratio of DMED/DEEA labeled SCFAs; x = concentration (nM).