Beer's law is based on the fact that absorbance is directly proportional to the concentration of a solution.
Therefore, stray light can alter the absorbance results in this type of assay.
Deviations from Beer's Law are caused by:

One of the following may cause a laboratory acquired infection (LAI):

Protein in urine can be confirmed using sulfosalicylic acid (SSA) precipitation. The SSA reagent is added to a small volume of urine. Acidification causes precipitation of protein in the sample, which is subjectively graded as trace, 1+, 2+, 3+ or 4+. SSA reaction will detect albumin, globulins, and Bence-Jones proteins.
Which of the following would be the most appropriate method to confirm a positive protein from a urine dipstick:

Basophilic stippling is the term used to describe red blood cells that contain tiny particles of RNA within their cytoplasm. Basophilic stippling is associated with many conditions, but is strongly associated with lead poisoning.
Multiple small, dark blue particles scattered throughout the cytoplasm of erythrocytes is/are called:

This patient is most likely suffering from sickle cell anemia. This cell, which is sickle-shaped, is indicative of the presence of hemoglobin S. Polychromasia is also commonly observed in sickle cell anemia.
After experiencing crippling pain in her chest, Elizabeth's mother rushes her to the Emergency Room. After a complete blood count and differential are ordered, the hematology technologist views many peripheral cells similar in appearance to those found in the image below. Which condition is most likely present?