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Maharashtra College of Pharmacy Khamari, Gondia 441601.
The ICP-OES method, which stands for Inductively Coupled Plasma Optical Emission Spectroscopy, helps find out how much of certain elements are in a sample. It does this by using a high-temperature argon plasma to excite the elements. When the atoms get excited, they release light at certain wavelengths. The brightness of this light shows how much of each element is present, making it possible to analyze many types of samples like liquids, solids, and organic materials. This video goes over the main idea behind ICP-OES, including how samples are introduced and what the plasma torch does: Heavy metal contamination in herbal dietary supplements presents serious health risks for consumers. This study aims to create and confirm a strong analytical method using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) to measure toxic heavy metals (Pb, Cd, As, Hg, Cu, Zn, Cr, Ni) in herbal supplements sold in stores. The research seeks to fill important gaps in quality control standards and regulatory requirements for herbal products in the pharmaceutical industry. Theoretical Framework: The validation of this method is based on ICH Q2(R1) guidelines and standards from pharmacopoeias like USP, BP, and IP. ICP-OES works by using atomic emission spectroscopy principles; it excites sample atoms in argon plasma at temperatures over 6000K. This process creates unique emission patterns that help identify and measure different elements. The technique provides high sensitivity, can analyze multiple elements at once, and has a broad linear dynamic range, making it suitable for testing heavy metals in complicated herbal mixtures.
METHODOLOGY
1. Sample Collection and Preparation
- Sample Selection: Gather 30 different herbal dietary supplements that are available for sale in local stores and online, covering a range of herbal types (single herb, blends of herbs, standardized extracts).
- Sample Homogenization: Use a mortar and pestle to grind the samples into a fine powder (≤180 mesh) and keep them in a desiccator.
- Digestion Protocol: Perform microwave-assisted acid digestion using a mixture of nitric acid (HNO?) and hydrogen peroxide (H?O?) in a 3:1 volume ratio.
- Weigh 0.5 grams of the sample in PTFE vessels.
- Add 6 mL of concentrated HNO? and 2 mL of H?O?.
- Run the microwave digestion program for 15 minutes at 200°C, then hold for an additional 20 minutes.
- Allow it to cool down, then dilute to 25 mL with ultrapure water.
2. Instrumental Parameters
- ICP-OES Configuration: Set up the instrument in axial view mode for better sensitivity.
- Operating Conditions:
- RF Power: 1150 W
- Plasma gas flow: 15 L/min
- Auxiliary gas flow: 1.5 L/min
- Nebulizer gas flow: 0.75 L/min
- Sample uptake rate: 1.5 mL/min
- Analytical Wavelengths: Choose wavelengths that do not have interferences for each element based on the spectral database.
3. Method Validation Parameters
3.1 Specificity and Selectivity
- Test blank samples as well as matrix blanks.
- Check for spectral interferences using interference equations.
- Evaluate matrix effects using the standard addition technique.
3.2 Linearity and Range
- Create calibration standards ranging from 0.1 to 50 mg/L for each element.
- Analyze three times for each standard, then plot concentration against response.
- Calculate the correlation coefficient (r² should be ≥ 0.995).
- Establish the working range based on anticipated concentration levels.
3.3 Accuracy and Recovery
- Perform spike-recovery tests at three different concentration levels (50%, 100%, and 150% of expected amounts).
- Test certified reference materials like NIST SRM 1515 Apple Leaves and NIST SRM 1573a Tomato Leaves.
- Calculate the percentage recovery, aiming for an acceptable range between 80% and 120%.
3.4 Precision
Repeatability: Perform six tests on the same sample in one day.
Intermediate Precision: Conduct tests on three different days with various analysts.
Calculate the relative standard deviation (RSD ≤ 10%).
3.5 Detection and Quantification Limits
Find the limits of detection (LOD) and quantification (LOQ) using the signal-to-noise ratio method (S/N = 3:1 for LOD, 10:1 for LOQ).
Confirm results by analyzing a blank sample (n=20).
3.6 Robustness
Test how the method performs under different conditions:
- Change digestion temperature by ±10°C
- Adjust digestion time by ±5 minutes
- Vary plasma power by ±50 W
- Alter sample introduction systems
4. Quality Control Measures
Test quality control samples after every 10 samples.
Watch for instrument drift using internal standards (Y, Sc).
Use laboratory control samples and method blanks.
Create control charts for ongoing monitoring.
5. Statistical Analysis and Data Interpretation
Use ANOVA to compare methods in studies.
Apply a t-test to check for bias.
Calculate measurement uncertainty according to ISO/IEC 17025 guidelines.
Set acceptance criteria based on regulatory limits from WHO, FDA, and ICH.
6. Documentation and Reporting
Expected Outcomes
The validated method will accurately, precisely, and reliably measure heavy metals in herbal supplements, ensuring safety for consumers and meeting regulations. This method will act as a reference standard for quality control labs and help create consistent testing guidelines for assessing the safety of herbal products.
REFERENCES
Mangeshkumar Lilhare*, Jagruti Shiwankar, Jugnoo Chaudhari, Sindhu Wairagade, Swati Katre, Analytical Method Validation for Heavy Metal Detection in Commercially Available Herbal Dietary Supplements Using ICP-OES, Int. J. of Pharm. Sci., 2025, Vol 3, Issue 12, 287-291 https://doi.org/10.5281/zenodo.17787575
10.5281/zenodo.17787575