Loop through parent pages

Hi all,

I am looking for a way of looping through each of the parent pages in my wordpress site?

I have this static code which i would like to convert to dynamic using this loop:

<ul class="menu_list">
                    <li><a href="/">Home</a><span>|</span></li>
                    <li><a href="About">About PRM</a><span>|</span></li>
                    <li><a href="Safety-Services">Services</a><span>|</span></li>
                    <li><a href="Contact-Us">Contact Us</a><span>|</span></li>
                    <li><a href="/wp-admin/">Log In</a></li>
</ul>

Thanks very much for help with this.