Determination of lead in organic-inorganic compound fertilizer by hydride atomic absorption spectrometry

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Determination of Lead in Organic-Inorganic Compound Fertilizer by Hydride Atomic Absorption Spectrometry

Key words: hydride atomic absorption spectrometry; inorganic compound fertilizer; aesthetic analyzer; AA-1800. The traditional methods for determining lead in organic-inorganic compound fertilizers include flame photometry and graphite furnace techniques. However, flame photometry has a high detection limit, while the graphite furnace method suffers from poor repeatability and lead volatility loss. To address these issues, this study developed a flow injection-hydride generation-atomic absorption spectrometry method, which offers high sensitivity, selectivity, and automation. This technique provides a fast and accurate way to analyze lead content in complex matrices. The experimental setup included an AA-1800C atomic absorption spectrophotometer and a WHC-102A2 flow injection hydride generator. The reagents used were lead standard solution (1000 mg/L), potassium borohydride (20 g/L), iron solution (80 g/L), and nitric acid solution (1+1). The sample preparation involved digesting the fertilizer with aqua regia, followed by dilution and filtration. The hydride generation process was optimized by adjusting parameters such as iron concentration, oxidation time, carrier gas flow rate, and system acidity. Results showed that the optimal conditions for the analysis included using 10 mL of 80 g/L iron solution, 20 minutes of oxidation time, a carrier gas flow rate of 150 mL/min, and a working voltage of 100 V for the quartz tube. The linear range for lead determination was 0–30.0 ng/mL, with a detection limit of 0.2 ng/mL. Interference studies confirmed that common ions such as K⁺, Mg²⁺, Ca²⁺, Fe³⁺, Cu²⁺, Cr³⁺, Zn²⁺, and B³⁺ did not significantly affect the results within a relative error of ±5%. Precision and accuracy tests on four organic-inorganic compound fertilizer samples showed RSD values between 2.6% and 4.6%, with recovery rates ranging from 96.4% to 104.3%. The proposed method is simple, efficient, and suitable for routine analysis in laboratories dealing with complex fertilizer samples. Compared to conventional methods, it offers better anti-interference ability and lower detection limits, making it ideal for direct lead analysis in organic-inorganic compound fertilizers.