# Atomic Spectroscopy-Based Analysis of Heavy Metals in Seaweed Species
## 2 Atomic Spectroscopy-Based Heavy Metal Analysis Methods for Seaweed
### Atomic Emission Spectroscopy
#### 2.3.1 Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES)  
Sample analysis with ICP-OES is usually safer than FAAS due to the use of inert argon gas as an atomizer instead of a flammable gas, such as acetylene. Not requiring a lamp for each element, simultaneous multi-elemental analysis, and low ppb detection limits are among the advantages that make ICP-OES the favored technique for elemental determination in many industries, including the food industry. Additionally, heavy workloads of analysis created the need for a fast analysis technique and the ability to measure multiple elements in many samples. ICP-OES takes less than one minute to measure the concentration of up to 74 elements in a sample. In addition, samples that contain very high percent levels of total dissolved solids (TDSs) or suspended solids are easier to analyze using ICP-OES due to the high temperature of the plasma. However, unlike GFAAS, ICP-OES cannot reach sub-ppb and ppt detection ranges; therefore, it is not a suitable technique for measuring trace elements; however, the use of axially viewed ICP/OES systems has narrowed the gap [70,71]. ICP/OES provides a linear dynamic range of five orders of magnitude or greater (compared with two orders of magnitude for AAS) that makes both macro- and microanalysis of samples possible. The introduction of charge transfer device (CTD) detectors provides more flexibility in analytical line selection, and the use of several lines of the same element extends the dynamic range and reduces possible matrix effects or spectral interferences [72]. The combination of sample injection into an air carrier stream with a low sample consumption system has been evaluated for the analysis of microsamples through ICP/OES [73]. Reports of heavy metal analysis in seaweeds using ICP-OES are presented in the following sections, and the measured concentrations are depicted in Table 3.  
In a study by [PERSON] et al., fresh seaweed samples of _Eucheuma cottoni_ were collected from three major seaweed farms in East and West Malaysia [24]. A quantity of 0.5 g of dried sample was digested in a Teflon vessel with 10 mL of HNO\({}_{3}\) and 3 mL of HCl at 100 \({}^{\circ}\)C for 2 h. The elements Ag, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were analyzed with ICP-OES. Instrument calibration was carried out with a multi-element calibration standard solution diluted to the concentration range of 10 mg/L to 100 mg/L. The NIST standard reference material SRM 1400 and the NMIJ certified reference material CRM 7405-a were used to validate the results, which showed over 96% recovery values for all of the analyzed metals. Measurement data for the essential mineral elements, such as Fe, Mn, and Zn, were consistent with the literature data, suggesting that the seaweed is a good source of nutrients. The daily estimated intakes of most metals (calculated with measured values, consumption rates, and average body weight) were within the recommended daily dietary allowance levels. However, upon considering the health hazards of the potentially toxic elements, the authors concluded that the cumulative carcinogenic risk (calculated based on lifetime period of exposure to the ingested metals) was non-negligible. In addition, the total hazard index (HI), which represents non-carcinogenic chemical risk, was found to be 4.38, indicating a level of major concern [24]. In another study, samples from each of the three seaweed types (_Sargassum_ sp.-Phaeophyta, _Ulva fasciata_-Chlorophyta, and _Gracilaria_ sp.-Rhodophyta) were obtained  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & **S seaweed Farms** & **Coastal Regions** & **Canary Islands,** & **Wandoor Area of** & **Abandoned Intertidal Cu** & **Zhejiang,** & **Southeast Coast** \\  & **in Malaysia [24]** & **of Sri Lanka [26]** & **Spain [5]** & **S  
from four sites in the coastal regions of Sri Lanka [26]. A quantity of 0.25 g of dried sample was microwave-digested with 4 mL concentrated HNO\({}_{3}\) and 1 mL H\({}_{2}\)O\({}_{2}\).