If you wish to scale down the GOPOD assay you should proportionally decrease all volumes used in the assay: samples, glucose standard and GOPOD Reagent volumes.
Please note that the limit of detection will also decrease. While using 3 mL of GOPOD Reagent you can measure up to 100 μg of glucose. If the glucose concentration in your sample is higher, it should be diluted accordingly prior to the incubation with GOPOD Reagent. When you decrease the volume of GOPOD Reagent 3-fold to 1 mL, you can measure up to 33 μg of glucose.