Table 1.

Mass isotopomer distribution of short chain fatty acid standards intra- and inter- days assays

		Formate	Acetate	Propionate	Butyrate	Pentanoate
Day 1 (n=6, mean%±SD)	M1	1.22±0.004	2.35±0.003	3.01±0.016	4.64±0.016	5.77±0.018
	M2	NA	0.44±0.002	0.47±0.001	0.50±0.001	0.54±0.002
	M3	NA	NA	0.016±0.001	0.019±0.001	0.023±0.002
Day 2 (n=6, mean%±SD)	M1	1.19±0.078	2.30±0.020	3.69±0.113	4.56±0.014	5.65±0.031
	M2	NA	0.42±0.013	0.46±0.008	0.49±0.001	0.53±0.005
	M3	NA	NA	0.01±0.001	0.02±0.002	0.02±0.002
Day 3 (n=6, mean%±SD)	M1	1.18±0.045	2.30±0.011	3.79±0.062	4.55±0.018	5.64±0.021
	M2	NA	0.42±0.009	0.45±0.004	0.49±0.003	0.53±0.002
	M3	NA	NA	0.02±0.001	0.02±0.001	0.03±0.001
Inter-day average (n=3, mean%±SD)	M1	1.206±0.019	2.32±0.024	3.50±0.347	4.59±0.042	5.69±0.060
	M2	NA	0.42±0.010	0.46±0.005	0.49±0.007	0.54±0.005
	M3	NA	NA	0.015±0.0002	0.021±0.002	0.024±0.001
Theoretical value* (%)	M1	1.20	2.34	3.48	4.62	5.76
	M2	NA	0.42	0.44	0.48	0.54
	M3	NA	NA	0.014	0.019	0.025
Accuracy (%)	M1	99.4	98.9	100.5	99.2	98.7
	M2	NA	102.1	103.5	102.1	100.1
	M3	NA	NA	109.4	109.5	98.9

NA: Not assayed.

^*Theoretical values are from NIST data.