list posts from a combination of 2 categories

I have established a categories like:
news, department1, department2, department3,(and many others)

And my posts are often connected to 2 categories.

Now I want to create a page with the latest news from each department.

My theme is a child of Twenty Twelve, and I have added the following to functions.php:

add_shortcode('tokat', 'to_kat');

function to_kat($atts) {
	extract(shortcode_atts(array('cata' => '', 'catb' => ''), $atts));
	$category1 = explode(",",$cata);
	$category2 = explode(",",$catb);
	foreach ($category2 as $cat) :
		query_posts( array( 'category__and' => array($category1,$cat), 'posts_per_page' => 1, 'orderby' => 'post_date', 'order' => 'DESC' ) );
		while ( have_posts() ) : the_post();
			get_template_part( 'content', get_post_format() );
		endwhile;
	endforeach;
}

And I have added [tokat cata="1" catb="2,3,4,5,6"] in a Page.

But it doesn’t work.
It might be my interpretation of the “query” or the “LOOP” that is wrong, but what is wrong?