Table 1.

Absolute quantification of TcdA and TcdB in small samples using MS^E.

		Amounts of TcdA and TcdB studied (ng)
Digested (ng)*	63	125	250	500	1,000	2,000
Expected (ng)**	1.25	2.5	5	10	20	40
TcdA
Exp1***	0	0	3.08	8.7	16.46	31.7
Exp2	0	0	3.2	6.5	18.4	30.2
Exp3	0	0	3.4	6.3	16.3	32.7
Average	0	0	3.23	7.17	17.05	31.53
Stdev	0	0	0.16	1.33	1.17	1.26
TcdB
Exp1***	0.84	1.1	2.05	7.9	14.1	36.05
Exp2	0.83	1.1	2.5	4.6	13.04	33.4
Exp3	0.83	1.2	3.4	4.6	13.7	26.4
Average	0.83	2.23	2.65	5.7	13.61	31.95
Stdev	0.01	0.06	0.69	1.91	0.54	4.99

Three samples each of purified toxin were serially diluted by a factor of 2 and digested with trypsin.

Each sample was analyzed three times using MSE. The numbers represent the amounts of toxin digested and the obtained values.

The minimum amounts of digested TcdA and TcdB in buffer that can be loaded on the nUPLC column and still detected were respectively 5 ng (1.6 μg/mL) and 1.25 ng (0.43 μg/mL).

*Values were estimated from the theoretical concentration based on values provided by the manufacturer.

**Amounts expected on column based on values provided by the manufacturer.

***Experimental values on column.