2.3. Standard and calibration curve preparation
Five standard solutions were prepared in the range 1.5–36 mg/
mL dissolving histamine dihydrochloride in 10 mL of ultrapure
water. An aqueous solution of 1,7 diaminoheptane 98% was prepared
at the concentration of 7.5 mg/mL and used as internal standard.
The solutions were stored protected by light at 4 C for
3 months.
Five standard materials for the calibration curve (in the range
30–700 mg/kg) were prepared daily adding each histamine aqueous
solution to 5 g of blank matrix.