A water sample or an ablated water sample is drawn directly into a flame, and the atomic vapors formed in the flame absorb the characteristic electromagnetic radiation emitted by the light source. The measured absorbance of the sample is compared with the absorbance of a standard solution to determine the amount of the measured element in the sample.
Operation method
Flame Atomic Absorption
Materials and Instruments
watery Move I. Instrumentation Caveat 1. This method is suitable for the determination of cadmium, copper, zinc and lead in groundwater, surface water and wastewater. The applicable range is related to the characteristics of the instrument and varies with the parameters of the instrument. The concentration ranges of general AAS instruments are shown in Table 1.Table 1 Determination range and minimum detection limit of flame atomic absorption method2. Co-existing ions and compounds in groundwater and surface water do not interfere with the determination at common concentrations. 3.3. Cadmium absorption is inhibited when calcium concentration is higher than 1,000 mg/l, and the signal is inhibited up to 19% when the concentration is 2,000 mg/L. 4.4. under the weak acidic condition, when the content of hexavalent chromium in the sample is more than 30 mg/L, the result of lead determination is low due to the generation of lead chromate precipitation, in this case, it is necessary to add 1% ascorbic acid to reduce hexavalent chromium to trivalent chromium.5. When the content of dissolved silicon in the sample exceeds 20 mg/L, it interferes with the determination of zinc and makes the result low, adding 200 mg/L can eliminate this interference; the content of iron exceeds 100 mg/L, which inhibits the absorption of zinc.6. When the salt content in the sample is very high and the analytical wavelength is lower than 350 nm, non-characteristic absorption (i.e., background absorption) may occur, then you can use the non-characteristic absorption spectral line corresponding to the analytical line or use the automatic background correction device for correction.Correction. For more product details, please visit Aladdin Scientific website.
Hot plate, atomic absorption spectrophotometer, hollow cathode lamp, 200mL rigid beaker or triangular flask, 25mL and 50mL volumetric flasks, 1mL and 5mL pipettes.
II. Reagents
1. Nitric acid, excellent purity.
2. Perchloric acid, superior purity.
3. Metal standard reservoirs.
III. Experimental steps
1. Sample pre-treatment
Take 100 mL of water sample and put it into a 200 mL beaker, add 5 mL of nitric acid, heat the digestion on the hot plate (don't boil), and evaporate it until it reaches about 10 mL, then add 5 mL of nitric acid and 2 mL of perchloric acid, and continue the digestion until it reaches about 1 mL. If the digestion is not complete, add 5 mL of nitric acid and 2 mL of perchloric acid, and vaporize again to about 1 mL. Remove and cool, add water to dissolve the residue, and then dilute with water to 100 mL. At the same time, take 100 mL of 0.2% nitric acid and do the blank test according to the same operation as above.
2. Preparation of mixed standard solutions
Dilute the metal standard stock solution with 0.2% nitric acid to form a mixed standard solution, the concentrations are: cadmium 10.0 mg/L, copper 50.0 mg/L, lead 100.0 mg/L, zinc 10.0 mg/L.
3. Preparation of standard series of solutions for calibration curves
Pipette mixed standard solution 0, 0.50, 1.00, 3.00, 5.00 and 10.00mL, respectively, into six 100 mL volumetric flasks, diluted with 0.2% nitric acid to determine the volume. The concentrations of this standard series of solutions are: cadmium 0, 0.05, 0.10, 0.30, 0.50, 1.00 mg/L; copper 0, 0.25, 0.50, 1.50, 2.50, 5.00 mg/L; lead 0, 0.50, 1.00, 3.00, 5.00, 10.00 mg/L; zinc 0, 0.05, 0.10, 0.30, 0.50, 1.00 mg/L.
(4) On-line measurement
The instrument will be adjusted to the best working condition, with 0.2% nitric acid solution to adjust the zero, the first measurement of the standard series of solutions to draw a calibration curve, and then test the sample under the conditions, the concentration of the sample can be read directly from the instrument.