# Atomic Spectroscopy-Based Analysis of Heavy Metals in Seaweed Species
## 2 Atomic Spectroscopy-Based Heavy Metal Analysis Methods for Seaweed
### Atomic Absorption Spectrometry (AAS) Techniques
#### 2.2.2 Graphite Furnace Atomic Absorption Spectrometry (GFAAS)  
Graphite furnace atomic absorption spectrometry (GFAAS), in which a graphite furnace atomizes a sample, is a conventional technology for measuring elements at the sub-ppb concentration range utilizing microliter-sized sample volumes. Traditionally, samples are fed into the graphite furnace as solutions; however, direct solid and slurry sampling are now possible. Most often, calibration (even for slurry samples) is established with aqueous standards. The programmable temperature-control feature of GFAAS instruments allows the solvent and matrix to be separated from the analyte as a function of boiling point. The stabilized temperature platform furnace in GFAAS atomizes the analyte isothermally, which results in matrix modification for analyte stabilization and rapid furnace heating. Although this technique is a versatile and highly sensitive tool for the analysis of a wide range of sample types, it measures fewer analytes than FAAS and is much slower [35; 36]. Vaporization of a large amount of solid in the graphite tube can lead to matrix effects. The presence of uncharred organic material may affect the volatility of some elements, increase background levels, and build up carbonaceous material in the furnace. To improve these problems, the application of chemical modifiers can stabilize volatile elements in heated furnaces. In addition, background correction methods, such as the Zeeman or Smith-Hieffje methods, should be considered. The use of an oxygen or air ashing step in the furnace program or the addition of H\({}_{2}\)O\({}_{2}\) to the slurry diluent have been found to be effective in removing carbonaceous material [61; 62; 63; 64]. A methodology was developed by [PERSON] et al. in which a flame atomic absorption spectrometer (FAAS) was used to measure Cu and Zn, while graphite furnace atomic absorption spectroscopy (GFAAS) was utilized for the analysis of Cd, Cr, and Pb [14]. Seaweed specimens of 0.7 g of _U. lactuca_ (_Sea Lettuce_) from the eastern coasts of Algeria were mineralized in a microwave oven with HNO\({}_{3}\) (6 mL) and H\({}_{2}\)O\({}_{2}\) (2 mL). Phosphate monoammonium NH\({}_{4}\)H\({}_{2}\)PO\({}_{4}\) (10%), the phosphate PO\({}_{4}\) (0.2 mg), and magnesium nitrates Mg(NO\({}_{3}\))\({}_{2}\) were used as matrix modifiers for Cd, Pb, and Cr determination, respectively. Certified reference materials, CRM 279 (sea lettuce) and ERM CE 278 (muscle tissue), were used to validate the accuracy of the analytical procedure. Depending on the heavy metals, collection sites, and sampling seasons, significant correlations were determined for the different species studied. The accumulation sequence at all sites was found to be Zn > Cr > Cu, and the lowest concentration was observed for Pb. The authors observed that the accumulation of elements in seaweeds was closely related to thallus morphology and growth strategy. Filamentous and sheet-like macroalgae, exhibiting a higher surface area for element absorption, accumulated higher contents of elements than coarsely branched and thick-leathery macroalgae. The study confirmed that seaweeds are good biomonitoring tools of trace metal contamination in Mediterranean marine areas. Quantities of 5 g of ashed brown seaweed (_Fucus vesiculosus_) from coastal sites of Northeast England were mixed with 20 mL aqua regia for 48 h, refluxed on a hot plate, and diluted to 50 mL with DI for heavy metal analysis by FAAS and GFAAS [65]. The precision and recovery of the procedures were checked using NIES No. 9 Sargasso seaweed certified standard reference materials. The concentration sequence of the most abundant elements was found to be Fe > Mn > Zn > Cu, with Cd and Ag being the least abundant elements. The heavy metal load of seaweed at the sites investigated was similar to that of other polluted areas of the British coastline. Ag accumulation in seaweed was more prominent at sites affected by past mining activities. The presence of Cu, Pb, and Zn in the seaweed species _E.