**4. Detection of POPs at trace level in real environmental samples**

In sections 3 we introduced the SERS method to detect trace amount PCBs. In those experi‐ ments, the PCBs are in acetone solutions, as fundamental study. In this section we introduce some examples in practical trace POPs detection.

ized away. Then, we found PCBs Raman signal with the SERS method described before. Figs 14 (a) and (b) show the SERS spectra of pure white spirit and white spirit with 10-4mol/L PCBs, respectively. One can recognize characteristic Raman peaks of PCBs around 1590,

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49

**Figure 13.** SERS spectra of PCBs in dry soil samples after being treated by acetone: (a) ~10-5mol/L; (b) ~10-6mol/L; (c)

1290, 1240, 1030 and 1000 cm-1 in Fig 14 (b).

~10-7mol/L; (d) ~10-8mol/L.

#### **4.1. Detection of PCBs in dry soil samples**

The polluted soil samples were dried and made into small powers which were acquired from the Nanjing Institute of Soil (China). With a combination of the high-resolution gas chromatography and mass spectrometry techniques, sample I proved to contain about 5 μg/g PCBs and sample II proved to contain about 300 μg/g PCBs. 0.2 g soil sample I was put into 20 mL acetone and was agitated uniformly for about 5 minutes. This suspension was precipitated for 30 minutes and the transparent acetone solution in the upper layer was taken as solution sample A. 0.2 g soil sample I was put into 200 mL acetone and sol‐ ution sample B was obtained through the aforementioned process. 0.2 g soil sample II was put into 20 mL acetone to obtain solution sample C and was put into 200 mL ace‐ tone to obtain solution sample D.

The Ag nanorods SERS substrates were put into the solution samples A, B, C and D, respec‐ tively. After 30 minutes, the Ag nanorods substrates were taken out of the solutions and the acetone on the substrates was blown away using a nitrogen flow. The Raman spectra of these substrates dipped into solution samples were measured by a Renishaw Raman 100 spectrometer using a 633 nm He-Ne laser as the excitation source at room temperature.

Figs 13(a), (b), (c) and (d) show the measured Raman spectrum of the Ag substrates dipped into sample A, B, C and D, respectively. From Figs 13 (a), (b) and (c), one sees peaks at ~1600, 1280, 1240, 1150, 1030 and 1000 cm-1 clearly, demonstrating the common feature of PCBs. The peaks around 1590~1600cm-1 present benzene stretching vibration mode; the peak around 1280cm-1 presents CC bridge stretching vibration mode; the peak around 1030cm-1 presents CH bending in-plane mode; the peak around 1000cm-1 presents trigonal breathing vibration mode; and peaks around 1240~1250cm-1 and 1140~1200cm-1 present the vibration peaks induced by Cl substituent. These characteristic peaks suggest that PCBs in dry soil can be detected by the SERS method by dissolving into acetone. The most widely used PCBs are trichlorobiphenyls and pentachlorobiphenyls, we assumed that the molecular weight of the PCBs in the soil samples is 300, then the concentration of the PCBs acetone solution in solu‐ tion sample A, B, C and D are about 10-5mol/L, 10-5mol/L, 10-6mol/L, 10-7mol/L, and 10-8mol/L, respectively. Thus, with silver nanorod substrates, 5ug/g PCBs in dry soil samples can be detected by the SERS method.

#### **4.2. Detection of PCBs in white spirit**

PCBs in white spirit can also be detected by the SERS method with silver nanorod sub‐ strates. The concentration of PCBs in white spirit is about 10-4mol/L. We put a drop of PCBs "polluted" white spirit on the silver nanorod substrates and made the white spirit volatil‐ ized away. Then, we found PCBs Raman signal with the SERS method described before. Figs 14 (a) and (b) show the SERS spectra of pure white spirit and white spirit with 10-4mol/L PCBs, respectively. One can recognize characteristic Raman peaks of PCBs around 1590, 1290, 1240, 1030 and 1000 cm-1 in Fig 14 (b).

**4. Detection of POPs at trace level in real environmental samples**

some examples in practical trace POPs detection.

**4.1. Detection of PCBs in dry soil samples**

48 Organic Pollutants - Monitoring, Risk and Treatment

tone to obtain solution sample D.

can be detected by the SERS method.

**4.2. Detection of PCBs in white spirit**

In sections 3 we introduced the SERS method to detect trace amount PCBs. In those experi‐ ments, the PCBs are in acetone solutions, as fundamental study. In this section we introduce

The polluted soil samples were dried and made into small powers which were acquired from the Nanjing Institute of Soil (China). With a combination of the high-resolution gas chromatography and mass spectrometry techniques, sample I proved to contain about 5 μg/g PCBs and sample II proved to contain about 300 μg/g PCBs. 0.2 g soil sample I was put into 20 mL acetone and was agitated uniformly for about 5 minutes. This suspension was precipitated for 30 minutes and the transparent acetone solution in the upper layer was taken as solution sample A. 0.2 g soil sample I was put into 200 mL acetone and sol‐ ution sample B was obtained through the aforementioned process. 0.2 g soil sample II was put into 20 mL acetone to obtain solution sample C and was put into 200 mL ace‐

The Ag nanorods SERS substrates were put into the solution samples A, B, C and D, respec‐ tively. After 30 minutes, the Ag nanorods substrates were taken out of the solutions and the acetone on the substrates was blown away using a nitrogen flow. The Raman spectra of these substrates dipped into solution samples were measured by a Renishaw Raman 100 spectrometer using a 633 nm He-Ne laser as the excitation source at room temperature.

Figs 13(a), (b), (c) and (d) show the measured Raman spectrum of the Ag substrates dipped into sample A, B, C and D, respectively. From Figs 13 (a), (b) and (c), one sees peaks at ~1600, 1280, 1240, 1150, 1030 and 1000 cm-1 clearly, demonstrating the common feature of PCBs. The peaks around 1590~1600cm-1 present benzene stretching vibration mode; the peak around 1280cm-1 presents CC bridge stretching vibration mode; the peak around 1030cm-1 presents CH bending in-plane mode; the peak around 1000cm-1 presents trigonal breathing vibration mode; and peaks around 1240~1250cm-1 and 1140~1200cm-1 present the vibration peaks induced by Cl substituent. These characteristic peaks suggest that PCBs in dry soil can be detected by the SERS method by dissolving into acetone. The most widely used PCBs are trichlorobiphenyls and pentachlorobiphenyls, we assumed that the molecular weight of the PCBs in the soil samples is 300, then the concentration of the PCBs acetone solution in solu‐ tion sample A, B, C and D are about 10-5mol/L, 10-5mol/L, 10-6mol/L, 10-7mol/L, and 10-8mol/L, respectively. Thus, with silver nanorod substrates, 5ug/g PCBs in dry soil samples

PCBs in white spirit can also be detected by the SERS method with silver nanorod sub‐ strates. The concentration of PCBs in white spirit is about 10-4mol/L. We put a drop of PCBs "polluted" white spirit on the silver nanorod substrates and made the white spirit volatil‐

**Figure 13.** SERS spectra of PCBs in dry soil samples after being treated by acetone: (a) ~10-5mol/L; (b) ~10-6mol/L; (c) ~10-7mol/L; (d) ~10-8mol/L.

**5. Summary**

**Author details**

Zhengjun Zhang1

**References**

detection via silver nanostructure.

hua University, Beijing, P. R. China

41(6): 589–624.

lyticaChimicaActa, 2005, 531(2): 249–256.

, Qin Zhou1,2 and Xian Zhang1

\*Address all correspondence to: zjzhang@mail.tsinghua.edu.cn

In this chapter, it is introduced that although persistent organic pollutants such as PCBs are difficult to detect at trace amount, they can be detected and recognized rapidly via the SERS technique. Ag nanostructured SERS substrates prepared by the glancing angle deposition method are excellent at detection and their sensitivity can be further improved by tuning the thin underlayer films. With well designed and prepared Ag nanostructured SERS sub‐ strates, pentachlorinated biphenyl molecules are detected and recognized at trace level us‐ ing the SERS method. These series of studies provide a potential method for trace pollutant

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51

1 Advanced Materials Laboratory, Department of Materials Science and Engineering, Tsing‐

2 Institute of nuclear and new energy technology, Tsinghua University, Beijing, P. R. China

[1] Ross G. The public health implications of polychlorinated biphenyls (pcbs) in the en‐

[2] Ohtsubo Y, Kudo T, Tsuda M, et al. Strategies for bioremediation of polychlorinated

[3] Cicchetti D V, Kaufman A S, Sparrow S S. The relationship between prenatal and postnatal exposure to polychlorinated biphenyls (pcbs) and cognitive, neuropsycho‐ logical, and behavioral deficits: a critical appraisal. Psychology in the Schools, 2004,

[4] Hong J E, Pyo H, Park S J, et al. Determination of hydroxy-pcbs in urine by gas chro‐ matography/mass spectrometry with solid-phase extraction and derivatization. Ana‐

[5] Namiesnik J, Zygmunt B. Selected concentration techniques for gas chromatographic analysis of environmental samples. Chromatographia, 2002, 56Suppl. S: S9–S18. [6] Pitarch E, Serrano R, Lopez F J, et al. Rapid multiresidue determination of organo‐ chlorine and organophosphorus compounds in human serum by solid-phase extrac‐

vironment.Ecotoxicology and Environmental Safety, 2004, 59(3): 275–291.

biphenyls. Applied Microbiology and Biotechnology, 2004, 65(3): 250–258.

**Figure 14.** SERS spectra of white spirit without and with PCBs.

#### **4.3. Detection of Melamine in milk**

In the year 2009, milk produced by Sanlu Co. (China) was found to contain amounts of Mel‐ amine in much higher concentrations than usual. Milk with Melamine seems to contain more protein when detecting nitrogen concentration, but it is poisonous to children. With the SERS method with silver nanorods as substrates, we detected Melamine in milk. Figs 15 (a) and (b) show the SERS spectra of pure Melamine and milk with Melamine.

**Figure 15.** SERS spectra of Melamine and trace Melamine in milk.
