Estimation of heavy metals in Tea and Coffee powder using Shimadzu inductively-coupled- plasma-mass spectrometry

Significance of the topic

Tea and coffee rank among the world’s most consumed non-alcoholic beverages, valued for their nutritional and stimulatory properties.
However, they can accumulate trace and heavy metals through soil and processing, posing potential health risks.
Reliable methods for quantifying these elements are vital for consumer safety, quality control, and regulatory compliance.

Objectives and Study Overview

The study aimed to evaluate the performance of the Shimadzu ICPMS-2030 system for determining essential and toxic metals in commercial tea and coffee powders.
Specific goals included assessing method linearity, accuracy, precision, and compliance with FSSAI permissible limits.

Methodology

Sample Preparation

• Weighed 0.05 g of tea or coffee powder, added ultrapure water, HNO3, and HCl, then performed microwave-assisted digestion under a two-step temperature program.
• After cooling, digests were diluted to 50 mL with ultrapure water.
• Recovery studies were carried out by spiking samples at LOQ and 10× LOQ levels before digestion.

Calibration

• Certified reference solutions (1000 ppm) were diluted to generate seven calibration levels for each element based on FSSAI maximum residual limits.
• Limit of quantification was set at 20% of the maximum allowable concentration.

Instrumentation Used

Shimadzu ICPMS-2030 coupled with the AS-10 autosampler was operated with a mini torch, RF power of 1.2 kW, and optimized plasma, auxiliary, and carrier gas flows.
Collision cell technology with helium gas removed polyatomic interferences.
Yttrium and bismuth served as internal standards; gold was added to stabilize mercury.

Main Results and Discussion

Calibration curves demonstrated excellent linearity (R² ≥ 0.999) across all target elements.
Spike recoveries ranged from 88% to 103% at LOQ and 10× LOQ with RSD values below 6%.
All measured concentrations in the real tea and coffee samples were below the limits of quantification, except zinc in tea at 20.5 ppm, which remained within the FSSAI threshold.

Benefits and Practical Applications

The validated method offers high sensitivity, throughput, and accuracy for routine monitoring of trace metals in tea, coffee, and related products.
Its application supports quality control at multiple production stages and ensures products free from toxic metal contamination.

Future Trends and Potential Applications

Advances may include automated high-throughput workflows, integration with speciation analysis, greener sample digestion protocols, and portable MS platforms for on-site screening.
Combining ICP-MS data with machine learning could further enhance risk assessment and quality assurance capabilities.

Conclusion

The Shimadzu ICPMS-2030 system, coupled with microwave digestion, provides a robust and reliable approach for quantifying essential and toxic metals in tea and coffee powders.
The method meets regulatory requirements and supports effective quality and safety management in the beverage industry.

References

• Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2011
• AOAC Official Method 2015.01