**3. Analytical methods for quantification of heavy metals in food and beverages**

The quantification of heavy metals in foods, beverages and other is done by various analytical tools. The estimation of metal content in food stuff and other is dependent on the property of metal and it's concentration on to be examined sample. Pre-treatment of samples *viz.*, sample digestion by concentrated acids like nitric acid, HNO3 and sulfuric acid, H2SO4 etc., dry ash digestion, digestion in acidic medium using microwave etc., prior to perform analytical experiments are needed for samples under investigation [3, 5, 69]. The accurate determination of metals is ensured by choosing an appropriate digestion technique, and it has been demonstrated that specific digestion process affects the determination of metals. Therefore, to get precise results; the adaption of right digestion technique is necessary [70]. The common analytical techniques used for quantitative determination of heavy metals are Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Various digestion methods applicable for samples preparations for analytical quantification are tabulated in **Table 2**.

### **3.1 Flame atomic absorption spectrometry (AAS)**

Due to its simplicity and ability to measure several metals even at trace levels such as Cd, Cr, Ni, Pb, Mn, Cu, Co, Fe, Flame Atomic Absorption Spectrometry (FAAS) is frequently employed for metal identification from food and beverages materials [81, 82]. One of the most effective methods for obtaining trace elements in various sample is chemical vapor generation in combination with atomic absorption spectroscopy, which comprises Hydride Generation Atomic Absorption Spectroscopy (HGAAS) and Cold Vapor Atomic Absorption Spectroscopy (CVAAS). In contrast to CVAAS, is the superior method for mercury analysis from various samples, HGAAS is suitable for hydride-forming metals such as As, Pb, Se, and Sn [70]. Chuachuad et al. employed an intriguing technique for the measurement of Cd in wines by flow injection Cold Vapor AAS (CVAAS) [83] and Pb by HGAAS following wine microwave digestion by combination of HNO3 + H2O2 [84].


**Table 2.**

*Digestion method used for heavy metals determination by various techniques.*

### **3.2 Total reflection X-ray fluorescence (TXRF)**

TXRF is a recognized analytical method for the determination of metals in a wide range of samples; particularly powdered and liquids micro samples are analyzed by this tool [85]. The advantages of TXRF are: it requires very low mass of sample with very low analysis time (100–1000 s). The primary drawbacks are caused by the potential peak overlapping, which may restrict element identification and reduce the *Monitoring Strategies for Heavy Metals in Foods and Beverages: Limitations for Human… DOI: http://dx.doi.org/10.5772/intechopen.110542*

estimation precision [80]. Drinks and beverages make really good liquid samples for TXRF analysis due to the quick and easy preparation process for qualitative analysis, which involves depositing a small amount of sample on a clean quartz-glass carrier and drying it. The noticeable impact for this analytical tools is that the internal standard added at the early state of quantification are free from the original sample at the final stage of quantification [86]. TXRF is recommended by several studies as an appropriate method for elemental analysis of wine with little to no pre-treatment [87, 88]. Direct wine drop deposition on the sample carrier, followed by internal standard deposition [89]. According to the earlier reported, the sample's digestion makes the chemical analysis more precise. In those instances, the samples were digested using a mixture of HNO3 and H2O2 [90].

### **3.3 Inductively coupled plasma-optical emission spectroscopy (ICP-OES)**

ICP-OES, which stands for inductively coupled plasma-optical emission spectrometry, is used to quickly and accurately identify trace elements in a variety of materials and is appropriate for multi-elements analysis. This method uses argon gas-created plasma for atomization and is distinguished by great sensitivity, excellent reproducibility, and minimal matrix influence. It is necessary to digest the sample before injecting it into the device since samples delivered in plasma must be liquid [91].

### **3.4 Inductively coupled plasma-mass spectrometer (ICP-MS)**

ICP-MS, a mass spectrometer paired with inductively coupled plasma ionization, is one of the most sensitive analytical techniques for quick multi-element detection of heavy metals in trace and ultra-trace quantities in various sample matrices [92]. In the present, it is the most appropriate approach for the analysis of trace elements in bulk materials, due to its recent development as a potent technology. Few drawbacks associated with ICP-MS are: significant capital investment and a lack of recognized reference standards [93]. For the majority of elements, ICP-MS gives incredibly low detection limits, ranging from a part per billion (ppb) to a trillion (ppt). In comparison to GF-AAS and ICP-AES, it has lower detection limits and a faster multi-element scanning capabilities over a wider range of masses [92].

### **3.5 Chemical replacement combined with surface-enhanced laser-induced breakdown spectroscopy (CR-SENLIBS)**

Due to its appealing qualities, including quick, simultaneous multi-element detection and in-situ, real-time analysis capabilities, laser-induced breakdown spectroscopy (LIBS) is one of the competitive methods for monitoring water quality [94]. Surfaceenhanced LIBS (SENLIBS), a novel method for the phase transition from liquid to solid, has recently been regarded as a flexible analytical approach for liquid samples, and solid samples [95]. The liquid sample was combined with the powder sample in a viscous mixture. Chemical processing converted the solid sample into the liquid sample. The liquid sample was subsequently dried as a solid layer or applied as a gel-like layer on a surface of the non-absorbent substrate, and LIBS analysis was performed. Up till now, a variety of techniques, including liquid micro extraction [96], chemical replacement [94] have been suggested to further enhance detection sensitivity or the spectrum intensity of SENLIBS [97].
