Maybe using the QUECHERs method to do the extraction.

Dear Sir. Concerning your issue about the determination of vitamins B content in bread with HPLC. Standard stock solution for vitamin B1 (thiamine HCl) was prepared by dissolving 26.7 mg of thiamine hydrochloride in 25 ml of double distilled water. Standard stock solution for vitamin B2 (riboflavin) was prepared by dissolving 6.9 mg of riboflavin in 100 ml of extraction solution because the extraction solution has limit to dissolve 7 mg of riboflavin. Standard stock solution for vitamin B3 (nicotinamide) was prepared by dissolving 41.5 mg of nicotinamide in 25 ml of double distilled water. Standard stock solution for vitamin B5 (calcium salt of pantothenic acid) was prepared by dissolving 21.4 mg of calcium d-pantothenate in 25 ml of double distilled water. Standard stock solution for vitamin B6 (pyridoxine HCl) was prepared by dissolving 20.8 mg of pyridoxine hydrochloride in 25 ml of double distilled water. The working standards were prepared as follows: i) For B1, 1.068 mg/ml and 562 µl was taken in 10 ml volumetric flask, ii) B2, 0.069 mg/ml and 5.1 ml was taken in 10 ml volumetric flask, iii) B3, 1.66 mg/ml and 60.5 µl was taken in 10 ml volumetric flask, iv) B5, 0.856 mg/ml and 292 µl was taken in 10 ml volumetric flask, v) and for B6, standard 0.832 mg/ml and 72.2 µl was taken in 10 ml volumetric flask. Calibration curve was made by using mix standards in mobile phase with five point calibrations, analyzed independently by HPLC and a standard curve was plotted between concentration and peak area. I think the following below links may help you in your analysis:

http://www.ajol.info/index.php/ajb/article/viewFile/58989/47302

http://tigerprints.clemson.edu/cgi/viewcontent.cgi?article=2745&context=all_theses

http://digitalknowledge.cput.ac.za/jspui/bitstream/11189/3500/1/Van%20Wyk_J_Dolley_L_Mshicileli_N.pdf

Thanks

http://www.ajol.info/index.php/ajb/article/viewFile/58989/47302