Table 1.

Recovery and Matrix Effect of SCFAs from Fecal Extracts Spiked with Different Concentration of SCFAs Standards by Different Quantitation Methods^a

GC-MS propyl esterification method
compounds	spiked amount (μg/mL)	amount recovered (μg/mL)	% recovery	% RSD	% matrix effect
acetic acid	10	6.7 ± 1.0	66.9	14.9	76.3
	100	108.3 ± 15.0	108.3	13.9	94.4
	250	254.5 ± 16.3	101.8	5.9	92.7
propionic acid	10	7.2 ± 1.2	72.3	16.9	74.2
	100	100.2 ± 17.6	100.2	17.5	84.2
	250	244.5 ± 36.6	97.8	15.0	92.7
butytic acid	10	6.7 ± 1.1	67.0	11.2	77.7
	100	99.4 ± 20.4	99.4	20.6	88.2
	250	249.7 ± 38.1	99.8	15.3	97.4

GC-MS acidified water method
compounds	spiked amount (μg/mL)	amount recovered (μg/mL)	% recovery	% RSD	% matrix effect
acetic acid	10	7.5 ± 1.9	74.8	25.1	116.8
	100	108.7 ± 14.9	108.7	13.7	95.7
	250	226.1 ± 19.2	90.4	8.5	76.2
	10	7.5 ± 1.2	75.4	16.0	95.1
propionic acid	100	106.3 ± 10.7	106.3	10.1	80.3
	250	297.2 ± 23.1	118.9	7.8	76.2
	10	5.2 ± 0.4	52.2	6.8	89.6
butyric acid	100	87.6 ± 17.0	87.6	20.6	76.2
	250	291.7 ± 24.3	116.7	8.3	79.7

1H NMR quantitation relative to TSP method
compounds	spiked amount (μg/mL)	amount recovered (μg/mL)	% recovery	% RSD	% matrix effect
acetic acid	10	8.4 ± 0.4	83.7	4.2	90.6
	100	97.7 ± 4.3	97.7	4.4	118.5
	250	271.7 ± 16.0	108.7	5.9	111.7
	10	10.1 ± 0.6	101.4	6.0	107.2
propionic acid	100	116.6 ± 5.5	116.6	4.7	116.1
	250	332.1 ± 15.3	132.8	4.6	104.8
	10	5.4 ± 0.8	54.2	14.7	64.1
butyric acid	100	92.9 ± 4.6	92.9	5.0	118.1
	250	263.2 ± 14.7	105.3	5.6	106.8

1H NMR quantitation with calibration curve method
compounds	spiked amount (μg/mL)	amount recovered (μg/mL)	% recovery	% RSD
acetic acid	10	8.6 ± 0.4	85.6	4.2
	100	98.7 ± 5.1	98.7	5.2
	250	277.9 ± 16.3	111.2	5.9
	10	8.0 ± 0.48	80.2	6.0
	10	5.4 ± 0.8	54.1	14.7
butyric acid	100	92.0 ± 4.7	92.0	5.1
	250	263.0 ± 14.7	105.2	5.6

^aValues are expressed as mean ± SD. n = 6 per group.