Trace determination of lead, chromium and cadmium in herbal medicines using ultrasound-assisted emulsification microextraction combined with graphite furnace atomic absorption spectrometry

Indirect Competitive ELISA for the Determination of Total Chromium Content in Food, Feed and Environmental Samples

Background: This study aimed to prepare monoclonal antibodies (mAbs) with high immunoreactivity, sensitivity, and specificity for the chelate (Cr(III)-EDTA) of trivalent chromium ion (Cr(III)) and ethylenediamine tetraacetic acid (EDTA). Further, the study established an indirect competitive enzyme-linked immunosorbent assay (icELISA) for detecting the total chromium content in food, feed, and environmental samples. Methods: Hapten Cr(III)-iEDTA was synthesized by chelating Cr(III) with isothiocyanatebenzyl-EDTA (iEDTA). Immunogen Cr(III)-iEDTA-BSA formed by chelating Cr(III)-iEDTA with bovine serum albumin (BSA), and coating antigen Cr(III)-iEDTA-OVA formed by chelating Cr(III)-iEDTA with ovalbumin (OVA) were prepared using the isothiocyanate method and identified by ultraviolet spectra (UV) and inductively coupled plasma optical emission spectrometry (ICP-OES). Balb/c mice were immunized with the Cr(III)-iEDTA-BSA, and the anti Cr(III)-EDTA mAb cell lines were screened by cell fusion. The Cr(III)-EDTA mAbs were prepared by induced ascites in vivo, and their immunological characteristics were assessed. Results: The immunogen Cr(III)-iEDTA-BSA was successfully synthesized, and the molecular binding ratio of Cr(III) to BSA was 15.48:1. Three hybridoma cell lines 2A3, 2A11, and 3D9 were screened, among which 2A3 was the best cell line. The 2A3 secreted antibody was stable after six passages, the affinity constant (Ka) was 2.69 × 10⁹ L/mol, its 50% inhibition concentration (IC50) of Cr(III)-EDTA was 8.64 μg/L, and it had no cross-reactivity (CR%) with other heavy metal ion chelates except for a slight CR with Fe(III)-EDTA (1.12%). An icELISA detection method for Cr(III)-EDTA was established, with a limit of detection (LOD) of 1.0 μg/L and a working range of 1.13 to 66.30 μg/L. The average spiked recovery intra-assay rates were 90% to 109.5%, while the average recovery inter-assay rates were 90.4% to 97.2%. The intra-and inter-assay coefficient of variations (CVs) were 11.5% to 12.6% and 11.1% to 12.7%, respectively. The preliminary application of the icELISA and the comparison with ICP-OES showed that the coincidence rate of the two methods was 100%, and the correlation coefficient was 0.987. Conclusions: The study successfully established an icELISA method that meets the requirements for detecting the Cr(III)-EDTA chelate content in food, feed, and environmental samples, based on Cr(III)-EDTA mAb, and carried out its preliminary practical application.

Recent innovations of ultrasound green technology in herbal phytochemistry: A review

Ultrasound (US) has become one of the most important techniques in green chemistry and emerging technologies. Many research investigations documented the usefulness of US in a wide range of applications in food science, nanotechnology, and complementary medicine, where effective extraction of natural products is important. However, as with all novel technologies, US has advantages and limitations that require clarification for full adaptation at an industrial scale. The present review discusses recent applications of US in herbal phytochemistry with the emphasis on US effects on chemical structures of bioactive compounds extracted from herbs and their bioactivities. The impact of different US processing conditions such as frequency, intensity, duration, temperature, and pressure on the effectiveness of the extraction process and the properties of the extracted materials are also discussed. Different frequencies and intensities of US have demonstrated its potential applications in modifying, determining, and predicting the physicochemical properties of herbs and their extracts. US has important applications in nanotechnology where it supports the fabrication of inexpensive and eco-friendly herbal nanostructures, as well as acoustic-based biosensors for chemical imaging of the herbal tissues. The application of US enhances the rates of chemical processes such as hydrolysis of herbal fibers, which reduces the time and energy consumed without affecting the quality of the final products. Overall, the use of US in herbal science has great potential to create novel chemical constructions and to be used as an innovative diagnostic system in various biomedical, food, and analytical applications.

Application of liquid-phase microextraction to the analysis of plant and herbal samples

INTRODUCTION

The analysis of plant and herbal samples is a challenging task for analytical chemists due to the complexity of the matrix combined with the low concentration of analytes. In recent years different liquid-phase microextraction (LPME) techniques coupled with a variety of analytical equipment have been developed for the determination of both organic and inorganic analytes.

OBJECTIVE

Over the past few years, the number of research papers in this field has shown a markedly growing tendency. Therefore, the purpose of this review paper is to summarise and critically evaluate research articles focused on the application of LPME techniques for the analysis of plant and herbal samples.

RESULTS

Due to the complex nature of the samples, the direct application of LPME techniques to the analysis of plants has not often been done. LPME techniques as well as their modalities have been commonly applied in combination with other pretreatment techniques, including a solid-liquid extraction technique supported by mechanical agitation or auxiliary energies for plant analysis. Applications and the most important parameters are summarised in the tables.

CONCLUSION

This review summarises the application of the LPME procedure and shows the major benefits of LPME, such as the low volume of solvents used, high enrichment factor, simplicity of operation and wide selection of applicable detection techniques. We can expect further development of microextraction analytical methods that focus on direct sample analysis with the application of green extraction solvents while fully automating procedures for the analysis of plant materials.

Mineral Composition of <I>Connarus (Connarus perrottetii var. angustifolius)</i> and <i>Mansoa (Mansoa alliacea)</I> Species

Background:

This paper provides an overview of mineral composition of the medicinal species Connarus perrottetii var. angustifolius and Mansoa alliacea collected in 2012, 2013 and 2014, using atomic absorption spectrometry as analytical technique.

Methods:

Statistical tests were performed aiming to identify the similarities and the differences between the different sampling years.

Result:

It was found a variation in the content of the elements for the three years of sampling, but with no uniform behavior.

Conclusion:

Connarus perrottetii var. angustifolius and Mansoa alliacea showed low concentrations of metals that may be toxic above specific concentrations (Cr, Ni, As, Pb, Cd and Hg). Accordingly, a regular consumption of these species cannot cause intoxication. On the other hand, we should consider the mineral contribution of other foods on the daily diet.

Determination of cadmium in bread and biscuit samples using ultrasound-assisted temperature-controlled ionic liquid microextraction

BACKGROUND

In the present work, a simple and rapid method was proposed for the preconcentration of cadmium using ultrasound-assisted temperature-controlled ionic liquid microextraction (TC-IL-LPME). The dispersion of the ionic liquid (1-Hmim[PF₆ ]) in the aqueous phase was performed by heating it in an ultrasonic bath, followed by cooling in an ice bath. After centrifugation, the enriched phase was dissolved in 45% (w/w) nitric acid solution to reduce viscosity, and the cadmium content was measured employing electrothermal atomic absorption spectrometry (ET-AAS). The 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol reagent (Br-PADAP) was used as a complexing agent.

RESULTS

Under optimized conditions, the method had a detection limit of 2.0 ng L^-1 and an enrichment factor of 24. The accuracy of the method was evaluated through the analysis of the certified reference material of brown bread (BCR-191). The method was applied to the determination of cadmium in samples of bread and biscuit. The limit of detection of the solid samples was 0.10 μg kg^-1 . The recovery of cadmium in the samples varied between 93% and 107%.

CONCLUSION

The proposed method is presented as a simple, cheap, ecological and a sensitive alternative for the determination of cadmium in bread and biscuit samples. © 2019 Society of Chemical Industry.

Quality assessment of trace Cd and Pb contaminants in Thai herbal medicines using ultrasound-assisted digestion prior to flame atomic absorption spectrometry

A simple, efficient, and reliable ultrasound-assisted digestion (UAD) procedure was used for sample preparation prior to quantitative determination of trace Cd and Pb contaminants in herbal medicines using flame atomic absorption spectrometry. The parameters influencing UAD such as the solvent system, sample mass, presonication time, sonication time, and digestion temperature were evaluated. The efficiency of the proposed UAD procedure was evaluated by comparing with conventional acid digestion (CAD) procedure. Under the optimum conditions, linear calibration graphs in a range of 2–250 μg/L for Cd, and 50–1000 μg/L for Pb were obtained with detection limits of 0.56 μg/L and 10.7 μg/L for Cd and Pb, respectively. The limit of quantification for Cd and Pb were 1.87 μg/L and 40.3 μg/L, respectively. The repeatability for analysis of 10 μg/L for Cd and 100 μg/L for Pb was 2.3% and 2.6%, respectively. The accuracy of the proposed method was evaluated by rice flour certified reference materials. The proposed method was successfully applied for analysis of trace Cd and Pb in samples of various types of medicinal plant and traditional medicine consumed in Thailand. Most herbal medicine samples were not contaminated with Cd or Pb. The contaminant levels for both metals were still lower than the maximum permissible levels of elements in medicinal plant materials and finished herbal products sets by the Ministry of Public Health of Thailand. The exception was the high level of Cd contamination found in two samples of processed medicinal plants.

Methods of liquid phase microextraction for the determination of cadmium in environmental samples

Liquid phase microextraction (LPME) has been widely used in extraction and preconcentration systems as an excellent alternative to conventional liquid phase extraction. In this work, a critical review is presented on liquid phase microextraction techniques used in the determination of cadmium in environmental samples. LPME techniques are classified into three main groups: single-drop liquid phase microextraction (SDME), hollow fiber liquid phase microextraction (HF-LPME), and dispersive liquid-liquid microextraction (DLLME). Methods involving these liquid phase microextraction techniques are described, addressing advantages and disadvantages, samples, figures of merit, and trends.

Fe(III)-based metal-organic framework-derived core-shell nanostructure: Sensitive electrochemical platform for high trace determination of heavy metal ions

A new core-shell nanostructured composite composed of Fe(III)-based metal-organic framework (Fe-MOF) and mesoporous Fe₃O₄@C nanocapsules (denoted as Fe-MOF@mFe₃O₄@mC) was synthesized and developed as a platform for determining trace heavy metal ions in aqueous solution. Herein, the mFe₃O₄@mC nanocapsules were prepared by calcining the hollow Fe₃O₄@C that was obtained using the SiO₂ nanoparticles as the template, followed by composing the Fe-MOF. The Fe-MOF@mFe₃O₄@mC nanocomposite demonstrated excellent electrochemical activity, water stability and high specific surface area, consequently resulting in the strong biobinding with heavy-metal-ion-targeted aptamer strands. Furthermore, by combining the conformational transition interaction, which is caused by the formation of the G-quadruplex between a single-stranded aptamer and high adsorbed amounts of heavy metal ions, the developed aptasensor exhibited a good linear relationship with the logarithm of heavy metal ion (Pb²⁺ and As³⁺) concentration over the broad range from 0.01 to 10.0nM. The detection limits were estimated to be 2.27 and 6.73 pM toward detecting Pb²⁺ and As³⁺, respectively. The proposed aptasensor showed good regenerability, excellent selectivity, and acceptable reproducibility, suggesting promising applications in environment monitoring and biomedical fields.

Simultaneous determination of ultra-low traces of lead and cadmium in food and environmental samples using dispersive solid-phase extraction (DSPE) combined with ultrasound-assisted emulsification microextraction based on the solidification of floating organic drop (UAEME-SFO) followed by GFAAS

Dispersive solid-phase extraction (DSPE) combined with ultrasound-assisted emulsification microextraction (UAEME) for determination of lead and cadmium in food and environmental samples prior to GFAAS.

An ultrasound-assisted ion association dispersive liquid–liquid microextraction coupled with micro-volume spectrofluorimetry for chromium speciation

A micro-volume spectrofluorimetric coupled ultrasound-assisted ion association dispersive liquid–liquid microextraction (USA-IA-DLLME) procedure for the total determination and speciation of chromium(iii & vi) species has been presented.