Determination of plant mineral elements by atomic absorption
Plant mineral elements are essential for plant growth, and most of them are involved in metabolic activities as necessary components of coenzymes or cofactors. Lack of essential mineral elements will lead to metabolic disorders in plants, which may induce diseases or even death in serious cases. Therefore, the determination of the content of mineral elements in plant tissues plays an important role in the study of plant growth and development, the improvement of crop yield and quality, and environmental protection. The purpose of this experiment is to master the operation of atomic absorption spectrophotometer and its principle, and to familiarize with the method of determining potassium, calcium and other mineral elements.
Principle
The basic principle of Atomic Absorption Determination of Plant Mineral Elements is that all mineral elements in plant tissues can be dissolved in a certain concentration of nitric acid solution, so its content can be determined by Atomic Absorption Spectrophotometry. The plant sample ashing, with dilute nitric acid in a low-temperature furnace heating extraction, in the process of nitric acid temperature rise, the ash in the various metal elements will gradually dissolve in nitric acid. Then, with the atomic absorption spectrophotometer, using different metal cathode lamps can be measured in the sample concentration of a variety of metal elements.
Operation method
Determination of plant mineral elements by atomic absorption
Principle
The basic principle of Atomic Absorption Determination of Plant Mineral Elements is that all mineral elements in plant tissues can be dissolved in a certain concentration of nitric acid solution, so its content can be determined by Atomic Absorption Spectrophotometry. The plant sample ashing, with dilute nitric acid in a low-temperature furnace heating extraction, in the process of nitric acid temperature rise, the ash in the various metal elements will gradually dissolve in nitric acid. Then, with an atomic absorption spectrophotometer, the concentration of various metal elements in the sample can be measured by using different metal cathode lamps. Potassium and calcium are two important essential mineral elements in plants. The plant samples were burned at 550 °C to make the carbohydrates decompose and evaporate, while potassium, calcium and other mineral elements remained in the ash, and the potassium and calcium in the ash were dissolved by hot HCI solution, and then the content could be determined by atomic absorption spectrophotometry.
Materials and Instruments
Material: plant material. Move The basic process of determining plant mineral elements by atomic absorption can be divided into the following steps: 1. Ashing of the material: Take the plant material, wash it with tap water and then rinse it once with convulsive water, absorb the water, put it in an enameled tray and dry it in an oven at 105 ℃. The material was dried in an oven at 105 °C. Weigh about 2 g of the dried sample in the porcelain Kankan, with a high-temperature furnace heated to 550 ℃ burn 2 h, until the material becomes gray-white. 2. 2. Dissolution and filtration: Add 5 mL of hot 5.8 mol・L-1 HCI solution to the above plant ash sample to dissolve the ash, filter, and collect the filtrate in a 100 mL volumetric flask. Wash the crucible with 0.5% HCI solution for several times, filter it into a 100 mL volumetric flask, and then dilute it with 0.5% HCI solution to 100 mL. 3. 3. Atomic absorption spectrophotometry: (1) According to the operating procedures for the use of the instrument, adjust the conditions of the atomic absorption spectrophotometer. (2) Determine the content of potassium and calcium in plant samples by standard curve method. Take six 100 mL volumetric flasks and add 0.0, 0.2, 1.0, 2.0, 3.0, 4.0 mL of standard K masterbatch and 0.0, 0.2, 0.4, 1.0, 1.6, 2.0 mL of standard Ca masterbatch; add 10 mL of 3% LaCl3 solution into each volumetric flask, and then set the volume with 2% HCI, which is a mixed standard solution of potassium and calcium. Take 10 mL of the liquid to be measured into a 100 mL volumetric flask, add 10 mL of 3% LaCl3 solution and then 2% HCI solution. Wash the burner with deionized water, then measure the No. 1 standard solution (blank) to adjust 0, and then measure the No. 6 standard solution to adjust the absorbance of 0.90 or so. Re-spray clean the burner, and then measure the No. 1-6 standard solution, record the absorbance value, plot the standard curve or linear regression equation. Pipette 10 times diluted solution to be measured, measurement, record the absorbance value, from the standard curve or regression equation to find the K, Ca content. 4. 4. Calculation of experimental results: Caveat 1. Use the Atomic Absorption Spectrophotometer in accordance with operating procedures. 2. When ashing, put the cover diagonally over the snail, leaving a small slit. For more product details, please visit Aladdin Scientific website.
Reagents:
① 5. 8 mol・L
-① 5. 8 mol・L
HCI solution: 11.6 mol・L
① 5. 8 mol・L -1 HCI solution: 11.6 mol・L -1
① 5.8 mol・L -1 HCI solution: 11.6 mol・L -1 HCI and deionized water are mixed 1:1 (V:V).
② 0.5% HCI solution: 5 mL of concentrated HCI with deionized water to 1 L.
③ 1 mol・L
-1 mol・L
HCI solution.
④ 500 mg・L
④ 500 mg・L -1
K standard master batch: accurately weigh 4 g of KCI 0.953 dried at 105 ℃ for 5 h, and then dilute to 1 L with deionized water.
⑤ 500 mg・L
⑤ 500 mg・L -1
⑤ 500 mg・L -1 Ca standard mother liquor: accurately weigh the CaCO
3
1.248 5 g dissolved in 1 mol・L-1 Ca standard mother liquor.
1 mol・L -1
HCI solution to drive away CO
2
After that, the volume was fixed to 1 L.
(vi) 3% LaCl
3
solution: weigh 30 g of analytically pure LaCl
3
Dissolve it and then set the volume to 1 L with deionized water.
⑦ 0.1% EDTA.
Equipment:
① Electronic balance
② High-temperature electric furnace
③ Enameled disk
④ Oven
⑤ Porcelain Bowl
⑥ Volumetric flask
⑦ Bottle washing
⑧ funnel
⑨ Pipette
⑩ Atomic absorption spectrophotometer
⑪ Potassium and calcium hollow cathode lamps