Among the industrially utilized elemental analysis processes, atomic absorption spectroscopy (AAS or AA spectroscopy) was among the quickest to be globalized. It is extensively utilized due to its simplicity, accuracy, and standardized functionality. This article considers the process of atomic absorption spectroscopy specifically for the determination of Cadmium.
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What is Atomic Absorption Spectrometry?
AAS is a technique for determining how much of a specific element is present in the specimen under study. The uptake of optical radiation by neutral atoms in the gaseous state is utilized in this process for the quantitative measurement of chemical components.
A Brief Introduction to the Analysis Process
The analysis of AAS results is straightforward, as it follows Beer's law which states that absorption of optical waves is directly proportional to the concentration of the element.
This implies that the amount of the analyte is proportional to the electrical output of the sensor. Using many mixtures of standard concentrations to calibrate the device is one technique for determining the unspecified percentage of an analyte. The standardization curve depicts radiation (amount of light absorbed) vs concentration, and once the specimen is analyzed, the proper amount may be calculated from it.
Do Background Noise Radiation Signals Affect the Results?
Background radiation noise can occur when obtaining absorption spectra because the sensors pick up impulses from other elements in the flame. This does not indicate that the resulting spectrum is not indicative of the sample; rather, it causes a loss of spectroscopic information, such as peak flattening and the emergence of peaks where the specimen does not assimilate.
Strengths and Limitations
The major advantage is the very low cost of analysis when compared to other processes. The extremely high accuracy and easy operational procedure make it a very good choice. The analysis is also unharmed by the cross-element interference. These are the core reasons this process is widely employed in vast industries.
However, there are certain limitations to the process. It does not apply to non-metals; hence, the equipment can only detect metallic elements. The analysis process cost may be low; however, the equipment is quite expensive requiring constant maintenance. Being a destructive testing method, the specimen is disintegrated. All such factors are major obstacles.
Why Cadmium Monitoring is Essential
Cadmium is considered to be one of the most highly hazardous toxic metals. In humans, acute cadmium toxicity causes high blood pressure, renal injury, and red blood cell disintegration. The necessity to analyze cadmium concentrations in the ecological specimen at ever-lower amounts is growing. This necessitates the use of very delicate, simple, quick, and low-cost techniques.
Which Techniques are Useful for its Analysis?
Cadmium is commonly determined using flame atomic absorption spectrometry (FAAS). A liquid specimen is turned to a vapor form in a vaporizer and inhaled into a flame, where it is eventually atomized. Because light travels through the atoms and flame at the same time, the flame acts as a "specimen holder," allowing the absorption of light to be determined.
However, there are certain limitations of the method. In many sediment samples, it has inadequate sensitivity for lower metal concentrations. To address this issue, a number of pre-processing techniques have been developed.
Solvent extraction, electrochemical treatments, ionic membrane movements, and solid-phase extraction have all been employed to determine low-level cadmium ion concentrations in addition to this approach.
Determination of Cadmium in Water Samples
A study published in Water, Air, & Soil provides a pipette tip solid-phase extraction (PT-SPE) approach based on silica nanoparticles (Si-NP) for determining trace levels of cadmium in natural water specimens. The cadmium analyte was determined using slotted quartz tube flame atomic absorption spectrophotometry (SQT-FAAS).
At pH 8.0, the maximum extraction efficiency was obtained. The highest elution performance was obtained at 6.0 M nitric acid, and the signals significantly decreased at higher doses. The maximum absorbance values were found at 15 mL/min, according to the findings.
The complete approach provides a fast, simple, and low-cost solid-phase extraction process for successful cadmium isolation and purification from mineral water specimens. Furthermore, because it does not require huge amounts of harmful toxic solvents, the new approach is compatible with sustainable analytical chemistry.
Electrothermal AAS of Cadmium
Metal levels in gasoline goods and used motor oils must be determined. This is critical for industrial machines. When low-ppb identification is required, the sensitivity attained is restricted, making Electrothermal AAS (ETAAS) and ICP-MS the ideal solutions for this type of application.
A study published in Talanta establishes an integrative technique of dispersive liquid-liquid microextraction with ETAAS as a sensitive and matrix-free analysis method for Cd measurement in combustion fluids and fuel materials.
This combination took use of the benefits of ecologically sustainable miniaturized specimen preprocessing as well as the rapid (less than 3 minutes), inexpensive, and accurate analysis of cadmium. The suggested approach eliminated the need for time-consuming microwave digesting mineralization and resolved all organic matrix issues in ETAAS.
Supramolecular Solvent-Based Microextraction with Thermo-Spray Flame Furnace AAS for Cadmium Analysis
Researchers have developed a novel technique for analyzing the concentration of Cadmium in flaxseed flour centered on ultrasound-assisted extraction, which is then followed by AAS using a thermo-spray flame furnace. The study has been published in the journal Food Chemistry. In terms of detectability, thermo-spray flame furnace atomic absorption spectrometry (TS-FF-AAS) is regarded as a strong approach.
The approach stands out because of its minimal specimen consumption, accessibility, low-cost instrumentation, and nontoxicity, making it a viable replacement for commonly used sample pretreatment processes.
The poor resilience of a large variety of materials might be stated as a constraint of ultrasound-assisted extraction paired with TS-FF-AAS, as the method's effectiveness is dependent on the type of the material and metallic ion.
What Does the Future Hold for AAS?
After British scientist Sir Alan Walsh identified several uses for the innovation, the first commercialized AAS spectrometers were created in the 1950s. Many developments have been achieved since then.
The market is presently worth $470 million, and it is expected to continue to rise as new projects are created. From now until 2024, experts project that the worldwide AAS market will rise at a CAGR of around 6.5 percent, reaching a value of $680 million.
Researchers all over the world are focused on the expansion of AAS methods which has led to the development of Hybrid/fusion RAMAN/LIBS methods. All such innovations would not only improve its effectiveness but also play a vital role in its expected market surge.
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References and Further Reading
Visser , D., 2022. Atomic Absorption Spectroscopy, Principles and Applications. [Online]
Available at: https://www.technologynetworks.com/analysis/articles/atomic-absorption-spectroscopy-principles-and-applications-356829
Girgin, A. et al. (2021) Determination of Cadmium in Mineral Water Samples by Slotted Quartz Tube-Flame Atomic Absorption Spectrometry After Peristaltic Pump Assisted Silica Nanoparticle Based Pipette Tip Solid Phase Extraction. Water Air Soil Pollut 232, 422. Available at: https://doi.org/10.1007/s11270-021-05386-8
Lemes, L. F. R., & Tarley, C. R. T. (2021). Combination of supramolecular solvent-based microextraction and ultrasound-assisted extraction for cadmium determination in flaxseed flour by thermospray flame furnace atomic absorption spectrometry. Food Chemistry, 357, 129695. Available at: https://doi.org/10.1016/j.foodchem.2021.129695
Aguirre, Miguel Ángel, et al. 2020 "Determination of cadmium in used engine oil, gasoline and diesel by electrothermal atomic absorption spectrometry using magnetic ionic liquid-based dispersive liquid-liquid microextraction." Talanta 220. 121395. Available at: https://doi.org/10.1016/j.talanta.2020.121395
Evans, E. Hywel, et al. 2020. "Atomic spectrometry update: review of advances in atomic spectrometry and related techniques." Journal of Analytical Atomic Spectrometry 35(5). 830-851. Available at: https://doi.org/10.1039/D2JA90015G
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