This invention relates to spotting solutions for the production of assay articles with uniform spot size and morphology for the detection of biopolymers, comprising N-lauroyl sarcosine in a buffered solution. Optionally the spotting solution may further comprise a fluorophore or a dye. This invention further provides means for non-destructive quality control of the production of said assay articles. This invention further provides means for non-destructive quality control of the production of said assay articles.