From Merck Co., the reagents including potassium hydroxide, potassium hexaferrocyanide, acetic acid, methanol ethanol (analytical grade), hydrochloric acid (HCl) 37 %, dipotassium hydrogen phosphate (K2HPO4), acetamide (purity ≥ 99 %) (GC grade), acrylamide (purity ≥ 99.9 %), tetrachloroethylene (to conduct GC analysis), potassium hexaferrocyanide (carrez I) and zinc acetate (carrez II), were obtained. From Sigma-Aldrich Co., acetamide (purity ≥ 99 %) and Xanthydrol, were purchased. Agilent 7890A gas chromatographic (Agilent Co., USA) device coupled to an Agilent 5975c Mass selective detector (MSD inert); the column was an Agilent capillary column HP-5 ms (5 % phenyl siloxane/ 95 % methyl polyorganosiloxane; length × I.D.: 30 m × 0.25 mm; df: 0.25 µm).
For preparation of carrez solution I, 10.6 g of potassium hexaferrocyanide was dissolved in distilled water (100 mL). Carrez solution II was prepared by mixing 21.9 g of zinc acetate with acetic acid (3 mL), then was adjusted the volume to 100 mL with distilled water. The primary standard solution of acrylamide and acetamide (2000 μg/mL) was prepared in methanol. To obtain a working solution, the upper standard solution was diluted with methanol. Stock and working solutions were stored at 4 °C.
For preparation of carrez solution I, 10.6 g of potassium hexaferrocyanide was dissolved in distilled water (100 mL). Carrez solution II was prepared by mixing 21.9 g of zinc acetate with acetic acid (3 mL), then was adjusted the volume to 100 mL with distilled water. The primary standard solution of acrylamide and acetamide (2000 μg/mL) was prepared in methanol. To obtain a working solution, the upper standard solution was diluted with methanol. Stock and working solutions were stored at 4 °C.