Page 505 - Biosystems Engineering

Agricultur e Management 477

Transfer to a liter-measuring flask and fill the flask until you have

a 100-ppm standard solution. Transfer 10 mL of this solution to a
100-mL volumetric flask and dilute to the mark with DTPA extract-

ing solution to have a 10-ppm stock solution. To prepare working
standards, transfer 1, 2, 4, and 6 mL of stock solution (10 ppm) to
a series of clean 100-mL of volumetric flasks and dilute each to the

mark with DTPA extracting solution.
Volume of stock Zn solution taken: 0, 1, 2, 4, and 6 mL
Concentration of Zn now in solution: 0, 0.1, 0.2, 0.4, and
0.6 ppm
Iron standard solution: Dissolve 0.702 g of AR-grade ammonium
ferrous sulphate in 300 mL of distilled water in a beaker. Add 5 mL
1:5 H SO . Transfer to a liter-measuring fl ask and fi ll volume to the
2 4
mark. This is a standard 100-ppm solution. To prepare a working
standard, transfer 1, 2, 4, and 6 mL of stock solution and dilute
each to the mark with DTPA extracting solution volume of a stock
Fe solution.
Volume of stock Fe solution taken: 0, 1, 2, 4, and 6 mL
Concentration of Fe in solution: 0, 1, 2, 4, and 6 ppm
Manganese standard solution: Dissolve 0.288 g potassium perman-
ganate in 300 mL of distilled water in a beaker. Add 20 mL of
concentrated H SO , warm to about 60°C, and add oxalic acid solu-
2 4
tion dropwise to render the solution colorless. Cool and transfer
to a liter-measuring flask and make volume to the work. This is

100-ppm Mn solution. To prepare working standards, transfer 1,
2, 4, 6, and 8 mL of the standard solution to a series of 100-mL
volumetric flasks and dilute each to the mark with DTPA extract-

ing solution.
Volume of stock Mn solution taken: 0, 1, 2, 4, 6, and 8 mL
Concentration of Mn in solution: 0, 1, 2, 4, 6, and 8 ppm
Copper standard solution: Dissolve 0.392 g of copper sulphate in
400 mL of distilled water in a beaker. Transfer to a liter-measuring
flask and fill up to the mark with distilled water. This is a standard

solution containing 100-ppm Cu. To prepare working standards,
transfer 1, 2, 4, and 6 mL of stock solution to a series of clean

100-mL volumetric flasks and dilute each to the mark with DTPA
extracting solution.
Volume of stock Cu solution taken: 0, 1, 2, 4, and 6 mL
Concentration of Cu in solution: 0, 1, 2, 4, and 6 ppm
At least three to four standards and a blank of each micronutrient
cation are used to draw a calibration curve. The blank solution
0 (ppm) is used to determine the zero level of the atomic absorp-
tion spectrophotometer. The standards are then analyzed with
the lowest concentration first and a blank run between standards

to ensure that the line (zero point) has not changed. A graph of