Accessing cell values in a table

I have check box as one of the columns in my table which uses DataTable plugin. Here I get the selected rows in a array and trying to access the value of the second column of each of these selected like below.

 $('#submit_id').click(function () {
	        var sData = oTable.$('input').serializeArray();
                for(var i=0; i<sData.length; i++){
	             var $selectedRecNo = parseInt(sData[i].value);
	            alert($('td:eq(1)', $('#firstTable-id tbody tr:nth-child(' + $selectedRecNo+ ')')).html()); // undefined 
	       );
            }
	    }); 

I am getting 'undefined' instead of first column's value. I am not sure what is wrong.

I arrived at the above code based on a snippet provided by Allan in the following thread http://datatables.net/forums/discussion/1384/getting-table-cell-values

I have given below the same snippet for easy reference

$('#firstTable-id tbody tr').click( function () {
	    // Alert the contents of an element in a SPAN in the first TD
	    alert( $('td:eq(1) ', this).html() );
	} ); 

Thanks!