I heard from a friend, who follows the Hanafi school of law, that when a man shakes hands with a woman his ablution – wudu – is nullified. Is this true?

In the Qur’an Allah tells us about wudu,

O you who believe, when you get ready for prayer, wash your faces and your hands up to the elbows and wipe a part of your head, and feet up to the ankles .… if you have had contact with women, and do not find water, then make Tayamum …. Qur’an 5:6
The Hanafi’s interpret the words ‘contact with women’ to mean any physical contact whatsoever, even shaking hands or brushing past a woman. Thus, one sometimes sees practising Muslims decline to shake the hand proffered by a lady because of being ‘in the state of wudu’.
However, the Imams of the progeny of the Prophet (PBUH) – Ahl al-Bayt w – interpret the words ‘contact with women’ in this ayah to mean ‘intimate sexual intercourse’ which obviously nullifies the state of wudu.
Simple and innocent contacts, such as shaking hands or such contact that is made when brushing past a woman, do not render the state of wudu invalid.