The Existing Problems and Solutions in the Determination of Lead, Cadmium, Copper, and Diaphragm by Atomic Absorption Spectrometry

Question 1: The blank is too high during the test, especially the lead blank in the graphite furnace measurement is too high
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Measures: Blank problems from various aspects, summarized as follows: ① bad deionized water; acid ② high background value; ③ pollution vessel; ④ Injection system contamination and the like
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Impurity of nitric acid and perchloric acid may cause the blank value to be higher, especially the use of perchloric acid, which has a greater impact, so when rushing the acid, try to rush out the perchloric acid to reduce the residue, or use nitric acid and hydrogen peroxide.

Question 2: The sampling system, atomizer, and burner are clogged and dirty
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Measures: Air blowback or cleaning (ultrasonic + 5% HNO ₃ solution)
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Question 3: The absorbance of the standard curve is close to zero during detection
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Measures: Check whether the sampling system is blocked or the position of the injection needle, determine whether the sample is injected, check whether the graphite tube is damaged, whether the hollow cathode lamp is normal, whether the light path is aligned, and adjust accordingly if the problem is found
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Question 4: The flame measurement of high-concentration samples exceeds the range of the curve
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Measures: Rotate the combustion head at a certain angle to form an angle with the optical path to reduce the length of the optical path and reduce the sensitivity.
This is a countermeasure for exceeding the linear range under normal test conditions, because the atoms that can absorb resonance light after deflection Decrease, so that the fineness decreases, so that the standard of higher concentration will not exceed the linear range
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Question 5: The graphite tube is easy to burn out and the number of times of use is small
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Measures: Check whether the air pressure is normal, whether the graphite cap is tightly pressed, whether the cooling water is normal, whether the gas path is blocked, whether the atomization phase is too long, whether the temperature sensor is malfunctioning, whether the temperature is too high, whether the acid is completely driven off, if there is high chlorine Acid residue will accelerate the damage of the graphite tube
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Question 6: The result of flame detection of heavy metal chromium is low
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Measures: Use a rich flame to determine chromium by flame method, adjust the ratio and flow rate of gas and auxiliary gas
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If the total chromium in the soil is determined, hydrofluoric acid must be added for complete digestion, and ammonium chloride can be added as a sensitizer when the volume is constant