Food Analysis I: Dry Ashing Practical Considerations

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What is the purpose of reducing the volume of the sample on the hot plate during wet ashing?

To increase the temperature of the sample

To accelerate the ashing process

To allow for easy final transfer (correct)

To remove excess water from the sample

What is the recommended temperature for ashing in a furnace during the modified dry-wet ashing method?

600°C

525°C (correct)

700°C

400°C

What is the purpose of adding HNO3 to the ash during the modified dry-wet ashing method?

To dissolve the ash (correct)

To neutralize the ash

To remove excess carbon

To increase the pH of the ash

Why may some potassium be lost during the modified dry-wet ashing method?

Due to the repeated ashing process (B) Signup and view all the answers

What is the final step in the modified dry-wet ashing method?

Dissolving the ash in HNO3 (A) Signup and view all the answers

What is the purpose of evaporating the sample in a microwave drying oven during the modified dry-wet ashing method?

To remove excess water from the sample (C) Signup and view all the answers

What is the purpose of extracting or burning off high-fat samples prior to dry ashing?

To prevent the sample from spattering (D) Signup and view all the answers

What is the effect of using glycerin, alcohol, and hydrogen in dry ashing?

It accelerates the ashing process (A) Signup and view all the answers

Why is it necessary to use an appropriate blank determination when using an alcoholic solution of magnesium acetate to accelerate ashing of cereals?

To ensure the accuracy of the results (D) Signup and view all the answers

What is a major disadvantage of dry ashing?

It requires a long duration (A) Signup and view all the answers

What is the purpose of wet ashing?

To remove the organic matrix surrounding the minerals (B) Signup and view all the answers

What is a common problem associated with dry ashing at high temperatures?

The loss of volatile minerals (C) Signup and view all the answers

What is the primary benefit of using microwave instrumentation for ashing?

Reduced sample preparation time (B) Signup and view all the answers

What is the primary consideration in deciding between an open- or closed-vessel microwave system for wet ashing?

Amount of sample and required temperatures (B) Signup and view all the answers

What is the maximum sample size that can be processed in an open-vessel microwave system?

10 g (D) Signup and view all the answers

What is the purpose of condensers in open-vessel microwave systems?

Reflexing the sample (A) Signup and view all the answers

What type of vessels are used in open-vessel microwave systems?

Teflon, quartz, or Pyrex vessels (B) Signup and view all the answers

How many samples can be processed in an open-vessel microwave system?

Up to 6 samples (A) Signup and view all the answers

What is the primary function of the vacuum pump in the microwave muffle furnace process?

To evacuate the glass chamber (A) Signup and view all the answers

What is a major advantage of the microwave muffle furnace method over other methods?

Less chance of losing trace elements by volatilization (C) Signup and view all the answers

What is the primary purpose of adding a small amount of oxygen to the glass chamber in the microwave muffle furnace process?

To facilitate the breakdown of organic matter (D) Signup and view all the answers

Which of the following is a disadvantage of the microwave muffle furnace method?

Relatively expensive equipment (A) Signup and view all the answers

What is the purpose of measuring the alkalinity of ash in food analysis?

To determine the acidity or alkalinity of the food (B) Signup and view all the answers

Which of the following methods is used to analyze the surface contamination of fruits and vegetables?

Ash insoluble in acid (C) Signup and view all the answers

What is the purpose of adding a reagent to the solution in precipitation?

To form an insoluble complex with a known chemical formula (D) Signup and view all the answers

What is the principle behind quantifying mineral content using a spectrophotometer?

Measuring the absorbance of the solution at a specific wavelength (B) Signup and view all the answers

What is the role of EDTA in complex formation?

Forming strong complexes with multivalent metallic ions (D) Signup and view all the answers

What is the purpose of choosing an indicator-mineral complex?

To make it much weaker than the EDTA-mineral complex (D) Signup and view all the answers

What is the result of the reaction between the reagent and the mineral in precipitation?

Formation of an insoluble complex (A) Signup and view all the answers

What is the purpose of calibration curves in spectrophotometry?

To compare the absorbance of the solution with a known standard (D) Signup and view all the answers