In case of using crude enzyme samples, which we knew the properties of the crude enzyme is not pure and heterogenous. Is it better to use the DNS (with rochelle salt before) or use the DNS reagent first and rochelle salt at the end of the reaction?
NaK tartarate or Rochelle Salt is Added to DNS just to increase the shelf life of DNS. If you can freshly prepare the DNS reagent for assessment of reducing sugar you can use the DNS reagent without Rochelle Salt also..
If you add rochelle salt as the paper above suggests you can use the DNS reagent during a period of two years without major trouble....The stability of the moisture is very much increased by Na/K tartarate in such a way that the ready solution can stay at the bench and at room temperature for so long..without loss of the reducing sugars detection efficiency!!