Table I.

Comparison of the BPdG levels measured in DNA from BP-treated MCF-7 cells by BPDE–DNA SCIA and ³²P-postlabelling

Purification methods	SCIAa, mean ± SD adducts per 108	Mean % CV1 (within-day)	Mean % CV2 (inter-day)	32P-postlabellingb, mean ± SD adducts per 108	Mean % CV1 (within-day)	Mean % CV2 (Inter-day)	Ratioc	P1	P2
Phenol extraction	1162 ± 256	20.7	8.9	1682 ± 496	27.0	26.3	0.7	0.11	0.27
Qiagen columns	871 ± 92	10.25	6.5	2048 ± 340	40.3	15.7	0.4	<0.01	<0.01
Salting out	799 ± 104	11.95	9.3	1712 ± 308	16.3	12.8	0.5	<0.01	0.05

%CV1 refers to the within-day coefficient of variance for adduct levels measured by either method in independently extracted DNA samples, while %CV2 refers to the inter-day coefficient of variance of the same samples analysed twice or three times on different days; P1: P value for independent t-test for the inter-day mean adducts levels obtained by the two methods; P2: P value for paired t-test.

^aTriplicate DNA samples were extracted by the three methods and assayed independently twice.

^bTriplicate DNA samples were extracted by the three methods and assayed independently three times.

^cRatio of adduct levels measured by SCIA to those measured by ³²P-postlabelling.