def add_dest(df_conc, dest_labware, dest_start=1):
    """Setting destination locations for samples & primers.
    Adding to df_conc:
      [dest_labware, dest_location]
    """
    dest_start = int(dest_start)
    df_conc['dest_labware'] = dest_labware
    dest_end = dest_start + df_conc.shape[0]
    df_conc['dest_location'] = list(range(dest_start, dest_end))
    return df_conc
