The Total Starch Kit can be used for liquids containing as little as 200 micrograms per mL with some adjustments of conditions, as below:
 Mix 0.5 mL of sample with 0.5 mL of 100 mM sodium acetate buffer (pH 4.5).  Incubate at 40˚C and add 0.1 mL of Amyloglucosidase and incubate for 30 minutes. Add GOPOD reagent as usual. You will need to run an AMG blank as this enzyme preparation contains a very small amount of glucose.

Product Page (K-TSTA)