the present invention relates to methods of quality control of manufactured nucleic acid arrays . fluorescence detection is used to evaluate the quality of a printed nucleic acid array without the need to add or otherwise link a fluorescent compound or dye to the nucleic acid . nucleic acid arrays suitable for this method are those where the spots of the array are formed by printing a solution that contains the nucleic acid in an ion containing solution . printing quality may be evaluated by measuring the intensity of fluorescence at the location of each printed sample , and / or by measuring the “ morphology ” of the printed sample . printed spots can be “ imaged ” by measuring fluorescence across a spotted sample in two dimensions . the resulting image of a printed spot can be compared with a reference printed image expected for the printing equipment and solid phase used .