Preparasi sampel untuk alat Atomic Absorption Spectrofotometry (AAS)

Summary

This video outlines the step-by-step process for preparing samples for spectrophotometry or ashing. It covers important procedures, including bringing samples to room temperature before weighing, diluting with nitric acid, and heating the sample until clear fumes form. For dry ashing, samples are heated to create ash, then treated with nitric acid and filtered. The final stages involve diluting samples with water and preparing them for analysis using an Atomic Absorption Spectrophotometer. The process emphasizes flexibility in the use of nitric acid based on sample behavior during heating and the importance of filtering to avoid blockages in the equipment.

Takeaways

• 😀 Ensure the sample reaches room temperature before starting any preparation if it was stored in the refrigerator.
• 😀 Weigh the sample carefully before transferring it to the acid room for further processing.
• 😀 For wet ashing, dilute the sample with 20 mL of nitric acid and heat until clear white vapor appears. Adjust nitric acid volume based on sample behavior during heating.
• 😀 If the sample volume decreases or the color remains brown during wet ashing, add another 10 mL of nitric acid to ensure proper digestion.
• 😀 In dry ashing, heat the sample until white smoke dissipates and the sample turns to ash. Then, place it in a furnace at 550°C for 3 hours to turn it into white ash.
• 😀 After cooling, dilute the dry-ashed sample with concentrated nitric acid, heat to just below boiling point, and then allow it to cool.
• 😀 After ashing and digestion, filter the sample with distilled water (100 mL) to remove any residual solids and prevent clogging in the Atomic Absorption Spectrophotometer.
• 😀 Calibration of the Atomic Absorption Spectrophotometer should be done with standard solutions to ensure accurate results during analysis.
• 😀 Atomic Absorption Spectrophotometry (AAS) readings provide the necessary data to calculate the concentration of elements in the sample.
• 😀 The final concentration of elements is determined by applying formulas to the AAS readings, which can then be used for further analysis or reporting.

Q & A

What is the first step in sample preparation before weighing?

Before weighing the sample, make sure that the sample, taken from the refrigerator, has reached room temperature.

What is the next step after the sample is weighed?

After weighing, the sample is brought to an acid room where it is treated, particularly if it is a wet sample, by diluting it with 20 ml of nitric acid.

How long should the sample be heated with nitric acid?

The sample should be heated for approximately 15 minutes until the vapor turns white and clear.

What should be done if the sample reduces in volume and still has a brown color during heating?

If the sample shows a reduction in volume and remains brown, additional nitric acid (10 ml) can be added to the sample.

Is the addition of nitric acid a fixed amount?

No, the amount of nitric acid added is flexible and should be adjusted based on changes observed in the sample during heating.

How is a dry ashing sample prepared?

For dry ashing, the sample is heated for approximately 15 minutes until the white smoke disappears, and the sample becomes charcoal.

What happens after the sample becomes charcoal in the dry ashing process?

After the sample becomes charcoal, it is placed in a furnace at 550°C for three hours until the sample turns into white ash.

What is done after the dry ashing sample turns to white ash?

After cooling for a few minutes, the white ash sample is diluted with nitric acid and then heated again until just before boiling. Afterward, it is cooled.

What is the next step after cooling and diluting the ash with nitric acid?

The next step is to dilute all the test samples with 100 ml of distilled water (aquades) and then filter them to prevent any sediment from blocking the Atomic Absorption Spectrophotometer.

What is the purpose of standardization in this procedure?

Standardization is performed by adding a specified reagent, such as gym V&C, to ensure accurate and consistent measurements.