Penentuan MDL & LoQ Titrimetri Khlorida | ISO/IEC 17025 Series #35

Summary

This video discusses the determination of the Mercury Detection Limit (MDL) and Limit of Quantification (LOQ) using argentometric titration for chloride analysis. It explains the titration process, including calculating the MDL based on repeated measurements, standard deviations, and recovery rates. The script emphasizes the importance of blank titration, precise measurements, and meeting regulatory standards. The MDL of 0.5 mg/L for chloride was confirmed to comply with Indonesian water quality standards, ensuring the method’s accuracy and reliability in environmental testing.

Takeaways

• 😀 The script discusses the process of determining the Minimum Detection Limit (MDL) and Limit of Quantification (LOQ) in chloride detection through argentometric titration.
• 😀 MDL is defined as the smallest amount of titrant that can cause a detectable chemical change at the equivalence point during a titration.
• 😀 To determine MDL, a key step is ensuring that the titration is reproducible with 5 to 10 drops to reach the equivalence point, with the buret size influencing the volume per drop.
• 😀 A standard buret size of 25 mL is used in the experiment, where each drop equals 0.05 mL, crucial for calculating MDL accurately.
• 😀 The MDL formula involves calculating standard deviation (SD) from multiple trials, multiplying by 3.143 to determine the detection limit.
• 😀 LOQ is also mentioned but is not as central to the discussion as MDL, which focuses more on precise titrations and consistency in results.
• 😀 Chloride ion concentration is calculated using the volume of titrant, its normality, and the atomic mass of chloride, alongside volume adjustments.
• 😀 Three trials were conducted with varying amounts of titrant to assess recovery percentages, and results are compared to ensure method accuracy.
• 😀 The script also describes how to calculate percent recovery to ensure results fall within acceptable limits (90-110%).
• 😀 The results obtained through the titration method were validated based on regulatory standards and the method was found to meet the required specifications.

Q & A

What is the purpose of determining the Mercedes Detection Limit (MDL) and Limit of Quantification (LOQ)?

The purpose of determining MDL and LOQ is to evaluate the sensitivity and accuracy of the titrimetric method used for detecting chloride ions. These parameters help to define the smallest detectable and quantifiable amounts of the analyte within a given method.

What method is used for chloride detection in this analysis?

The method used for chloride detection is argentometric titration, where silver ions react with chloride ions in a neutral or slightly basic solution to form silver chloride (AgCl) precipitates.

How is the MDL calculated in this titrimetric analysis?

MDL is calculated using the formula MDL = 3.143 * SD, where SD is the standard deviation from seven replicate measurements. This gives the minimum detectable limit of chloride concentration in the sample.

What is the significance of the 5-10 drop range mentioned in the transcript?

The 5-10 drop range refers to the volume of titrant (silver nitrate solution) needed to achieve an equivalent point in the titration. This range helps assess the repeatability and precision of the method during the detection process.

How is the accuracy of the method evaluated?

Accuracy is evaluated by calculating the percent recovery of spiked samples. The recovery should fall within the acceptable range, typically between 90% and 110%, to ensure the method is both accurate and reliable.

What role does the standard deviation (SD) play in determining MDL?

The standard deviation (SD) reflects the variability or precision in the measurement process. A lower SD indicates greater precision. The MDL is directly proportional to SD, meaning higher SD values lead to a higher MDL.

What is the formula for calculating the chloride concentration in the solution?

The chloride concentration is calculated using the formula: (Volume of standard - Volume of titrant) * Normality of titrant * Atomic weight of chloride * 1000 / Volume of sample.

Why is it necessary to perform multiple repetitions in the experiment?

Multiple repetitions are required to ensure the reliability and consistency of the results. They help assess the precision of the titrimetric method under varying environmental and experimental conditions.

What is the importance of the meniscus in titration?

The meniscus is crucial for accurate volume measurement during titration. The proper reading of the meniscus ensures precise and consistent titrant delivery, which is essential for reliable results.

How is the limit of acceptance for the method determined?

The limit of acceptance is determined by evaluating the recovery percentage (percent R). If the recovery falls within 90-110% and the relative standard deviation (RSD) is under 10%, the method is considered acceptable for use.