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A topic from the subject of Standardization in Chemistry.

  • 11 months ago
  • 6 min read
Use of Certified Reference Materials (CRMs) in Chemical Analysis
Introduction

Certified reference materials (CRMs) are materials with well-characterized chemical compositions. They are used in chemical analysis to calibrate instruments, validate methods, and ensure the accuracy of results.

Basic Concepts

CRMs typically have a matrix similar to the samples being analyzed. This ensures the CRM behaves similarly to the samples during analysis.

A CRM's chemical composition is determined using various analytical techniques. The results are reported on a certificate accompanying the CRM.

Equipment and Techniques

CRMs are used in various chemical analysis techniques, including:

  • Atomic spectroscopy
  • Mass spectrometry
  • Chromatography
  • Electrochemical methods

The equipment and techniques used depend on the specific CRM and analytical method.

Types of Experiments

CRMs are used in various experiments, including:

  • Calibration of analytical instruments
  • Validation of analytical methods
  • Quality control of analytical data
  • Interlaboratory comparisons

The experiment type determines how the CRM is used.

Data Analysis

Data from CRM analysis calculates the accuracy and precision of the analytical method. Accuracy measures how close the results are to the true value, while precision measures how reproducible the results are.

CRM analysis data can also be used to develop quality control procedures for the analytical method.

Applications

CRMs are used in various applications, including:

  • Environmental analysis
  • Food analysis
  • Pharmaceutical analysis
  • Clinical chemistry

CRMs ensure the accuracy and reliability of chemical analysis results in these and other applications.

Conclusion

CRMs are essential tools for chemical analysis, ensuring the accuracy and reliability of results in various applications.

Use of Certified Reference Materials (CRMs) in Chemical Analysis

Introduction:

Certified reference materials (CRMs) are materials with well-established properties and composition that serve as calibration standards for analytical methods. They provide a traceable link to internationally recognized measurement standards, ensuring the accuracy and reliability of analytical results.

Applications of CRMs:

  • Calibration and validation of analytical instruments
  • Quality control and assurance in chemical measurements
  • Assessment of measurement uncertainty
  • Method development and evaluation
  • Interlaboratory comparisons
  • Training and proficiency testing

Types of CRMs:

  • Primary CRMs: Prepared from high-purity materials and characterized using primary measurement methods. These are the highest level of traceability.
  • Secondary CRMs: Calibrated against primary CRMs or other reference materials. They are often more readily available and cost-effective than primary CRMs.
  • Matrix CRMs: Contain analytes in a specific matrix, simulating real-world samples. This helps to account for matrix effects that can influence analytical results.

Selection and Use of CRMs:

CRMs should be carefully selected based on the analytes of interest, their concentration range, the matrix of the sample, and the intended use. The CRM's certified values and associated uncertainties must be appropriate for the analytical method's capabilities. They should be handled and stored according to the manufacturer's instructions to maintain their integrity and prevent contamination or degradation.

Benefits of Using CRMs:

  • Enhance accuracy and precision of analytical results
  • Improve comparability and traceability of measurements
  • Minimize bias and method variations
  • Provide a basis for assessing the performance of analytical methods and laboratories.
  • Facilitate the resolution of disputes related to analytical results.

Conclusion:

CRMs play a crucial role in chemical analysis by providing a reliable and traceable basis for calibration, quality control, and measurement uncertainty assessment. Their use ensures the accuracy, reliability, and comparability of analytical results across different laboratories and over time, contributing significantly to the overall quality and trustworthiness of chemical data.

Use of Certified Reference Materials (CRMs) in Chemical Analysis

Experiment: Determining Lead Concentration in Soil using a CRM

Materials

  • Certified Reference Material (CRM) for soil with a certified lead concentration (e.g., NIST SRM 2711).
  • Soil sample to be analyzed.
  • Inductively Coupled Plasma Mass Spectrometry (ICP-MS) or Atomic Absorption Spectrometry (AAS).
  • Calibration standards of lead with known concentrations.
  • Acid (e.g., nitric acid) for sample digestion.
  • Laboratory glassware (beakers, volumetric flasks).

Procedure

  1. Sample Preparation: Weigh accurately approximately 0.5 g of both the CRM and the soil sample. Digest each in a suitable acid (e.g., HNO3) using microwave digestion or a hot plate. Dilute to a known volume with deionized water.
  2. Calibration: Prepare a calibration curve using the lead calibration standards by measuring their absorbance or intensity using the ICP-MS/AAS. Plot the calibration curve (concentration vs. signal).
  3. Analysis: Analyze the digested CRM and soil sample solutions using the ICP-MS/AAS. Measure the signal intensity for each.
  4. Data Analysis: Use the calibration curve to determine the lead concentration in both the CRM and the soil sample from their respective signal intensities.
  5. Comparison: Compare the measured lead concentration in the CRM to its certified value. Calculate the percent recovery: [(Measured Concentration / Certified Concentration) x 100]%. This indicates the accuracy of the method.

Key Procedures and Considerations

  • Accurate weighing of samples is crucial for accurate results.
  • Complete digestion of the sample is necessary to ensure all lead is available for measurement.
  • Proper calibration of the instrument is essential. Regular checks and maintenance are recommended.
  • Use appropriate blanks to correct for background interference.
  • Perform replicate measurements to assess precision.
  • Consider matrix effects and potential interferences in the sample matrix.

Significance

CRMs are indispensable in chemical analysis. In this experiment, the CRM provides a known lead concentration, allowing for the validation of the analytical method and the assessment of its accuracy and precision. The percent recovery calculated by comparing the measured and certified values indicates the reliability of the results obtained for the unknown soil sample. Using a CRM ensures traceability to internationally recognized standards and enhances the comparability of results across different laboratories.

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