need to avoid duplicates on homepage loop

<!-- Featured is first -->
        <?php $my_query = new WP_Query('category_name=featured&posts_per_page=1');
          while ($my_query->have_posts()) : $my_query->the_post();
          $do_not_duplicate = $post->ID; ?>
            <?php
                // Get the ID of a given category
                $category_id = get_cat_ID( 'Featured' );
                // Get the URL of this category
                $category_link = get_category_link( $category_id );
            ?>
            <article>
                <header>
                    <h1><a href="<?php echo esc_url( $category_link ); ?>">// Featured</a></h1>
                </header>
                <div class="related-thumb">
                    <a href="<?php the_permalink() ?>" rel="bookmark"><?php the_post_thumbnail( 'cat-post-thumb'); ?></a>
                </div>
                <h2><a href="<?php the_permalink() ?>" rel="bookmark"><?php the_title(); ?></a></h2>
                <time datetime="<?php echo the_time('j-m-Y'); ?>" pubdate><?php echo ''.get_the_time('j').' '.''.get_the_time('M').' '.get_the_time('Y').''; ?></time>
                <p><?php the_excerpt(); ?></p>
            </article>
        <?php endwhile; ?>