Question

your lab technician performed the phenol-h2so4 analysis on food samples for total carbohydrates but the results showed low precision, and the values seemed a little high. the technician had used new test tubes (they had never been used, and were taken right from the cardboard box). what most likely caused these results? why? describe what happened.

Answer 1

The low precision and elevated results in the phenol-H2SO4 analysis for total carbohydrates are likely due to contamination from residues on new test tubes, which had not been cleaned before use.

Step-by-step explanation:

If the phenol-H2SO4 analysis on food samples for total carbohydrates showed low precision and the values appeared to be high, a likely cause for these results could be contamination of the test tubes. New test tubes often have manufacturing residues on their surfaces, which can interfere with chemical reactions. In this case, the new test tubes taken directly from the cardboard box might have had residues that reacted with the phenol and sulfuric acid, leading to falsely elevated carbohydrate readings.

Before use in a sensitive procedure like the phenol-H2SO4 test, new test tubes should be thoroughly washed, rinsed with distilled water, and dried. This is critical, as even small traces of contaminants can lead to significant errors in analytical chemistry, particularly when measuring the concentration of substances such as carbohydrates in food samples.