code: public void detachIdentifier(String identifier) {
  		if (!StringUtils.equals(identifier, getIdentifier())) {
  			Sysprop s = CoreUtils.getInstance().getDao().read(getAppid(), identifier);
  			if (s != null && StringUtils.equals(getId(), s.getCreatorid())) {
  				deleteIdentifier(identifier);
  			}
  		}
  	}
docs: Detaches a secondary identifier which is not already used by this user.
  @param identifier an attached identifier