HunterLab have a number of products popular for use in this market. Many customers prefer the UltraScan PRO or UltraScan VIS, for their unmatched ability to measure both liquid and powder samples, especially with UV and fluorescent optical brighteners. If your product does not contain these brighteners, then the robust ColorQuest XE will be a very suitable instrument. For measuring only for cleaning power, the LabScan XE is a very popular choice, because of its large 50 mm sample viewing diameter. For portability, look at the MiniScan EZ.