Determination of lead, cadmium and copper in water - Master's thesis - Dissertation

WIFI test head can be customized for other specifications

Test - lowercase jpg

Kaixin micro test

This study presents a novel approach for determining lead, cadmium, and copper in water samples using a two-hole injection graphite furnace atomic absorption spectrometer. The method involves the digestion of samples with nitric acid and hydrogen peroxide, followed by analysis using peak height mode. The results show excellent linearity with correlation coefficients of 0.9999, 0.9993, and 0.9994 for lead, cadmium, and copper, respectively. The relative standard deviation (RSD) was within 1.17%–1.93%, and the recovery rates ranged from 90.8% to 100%. This technique offers high sensitivity, precision, and accuracy, making it suitable for trace metal analysis in various water sources.

As industrialization expands and urban areas grow, heavy metal pollution becomes more prevalent in soil, air, and water environments. Heavy metals such as lead, cadmium, and copper often enter water bodies through industrial waste, mining activities, agricultural runoff, and domestic garbage. These pollutants are non-degradable and can combine with other toxins to form even more harmful substances. They tend to accumulate in living organisms, posing serious threats to aquatic life and human health. For instance, lead can damage brain cells, cadmium is linked to hypertension and kidney issues, and copper may cause liver and neurological problems. Therefore, accurate and efficient methods for detecting heavy metals in water are essential for environmental monitoring and public safety.

Figure 1. a Double-hole graphite tube, b sample image

The two-hole injection system uses a specially designed graphite tube (Figure 1a), allowing the autosampler to continuously aspirate and inject samples into the graphite tube. As shown in Figure 1b, the sample is evenly distributed across the two holes, ensuring uniform heating during the process. This design reduces the risk of sample bumping and shortens the heating time. Additionally, the increased injection volume (up to 100 μL) enhances detection sensitivity, especially for ultra-trace samples. This combination of features makes the method highly effective for precise and rapid heavy metal analysis in water samples.

The proposed method has been successfully applied to determine lead, cadmium, and copper levels in both park lake water and tap water. It is also applicable for the rapid detection of these metals in surface water, groundwater, and industrial wastewater, offering a versatile solution for environmental monitoring.

Experimental Part

Instruments and Reagents

Hitachi ZA3000 atomic absorption spectrometer; hollow cathode lamps for lead, cadmium, and copper (from China Nonferrous Metal Research Institute); Barnstead ultrapure water system; Gdana HT-300 electric hot plate; VITLAB glassware.

Standard solutions of lead, cadmium, and copper (1000 μg/mL) were obtained from the National Standards Center and diluted to appropriate concentrations during the experiment. Ammonium dihydrogen phosphate (1%), nitric acid (ultra-pure grade), park lake water, tap water, and ultrapure water were used as reagents and samples.

Sample Preparation

100 mL of water sample was transferred to a 200 mL beaker, 5 mL of nitric acid was added, and the mixture was heated on a hot plate until reduced to about 10 mL. Then, 5 mL of nitric acid and 10 mL of hydrogen peroxide were added, and the digestion continued until the volume was reduced to approximately 1 mL. After cooling to room temperature, the sample was diluted to 100 mL in a volumetric flask.

The analytical conditions are listed in Table 1.

Table 1. Instrument Analysis Conditions

Temperature Program

Table 2. Temperature Program Settings

Results and Discussion

Standard Curve Preparation

Lead (0.0–30.0 μg/L), cadmium (0.0–2.5 μg/L), and copper (0.0–15.0 μg/L) standard solutions were prepared. The resulting standard curves (Figures 1–3) showed good linearity with correlation coefficients of 0.9999, 0.9993, and 0.9994, respectively. Data are presented in Tables 3–5.

Figure 2. Lead (Pb) Standard Curve

Table 3. Lead (Pb) Standard Curve Data

Figure 3. Cadmium (Cd) Standard Curve

Table 4. Cadmium (Cd) Standard Curve Data

Figure 4. Copper (Cu) Standard Curve

Table 5. Copper (Cu) Standard Curve Data

Sample Analysis

Lead, cadmium, and copper contents in park lake water and tap water were analyzed according to the above procedure. Results are summarized in Table 6.

Table 6. Test Results of Lead, Cadmium, and Copper in Samples

The permissible limits for lead, cadmium, and copper in surface water (GB3838-2002) are listed in Table 7. The experimental data were compared with these standards, revealing that all measured values met Class I or II water quality requirements. This indicates that the water quality in the park and tap water is safe for use and meets environmental protection standards.

Table 7. Permissible Limits for Lead, Cadmium, and Copper in Surface Water (GB3838-2002)

Precision and Spike Recovery

Lead, cadmium, and copper in park lake water were analyzed six times consecutively, yielding an RSD of 1.17%–1.93%. A spike recovery experiment was conducted, with results shown in Table 8.

Table 8. Recovery of Each Element

Summary

The developed method for detecting lead, cadmium, and copper in water using two-hole injection graphite furnace atomic absorption spectrometry demonstrates high precision, good linearity, and acceptable recovery rates. It is simple, fast, and suitable for various water environments, including surface water, groundwater, and industrial wastewater. This technique provides a reliable and efficient alternative for trace metal analysis in environmental testing.