Which acid is used to acidify urine for Ca, Mg, or PHOS testing?

Prepare for the CAMLPR Chemistry Test. Enhance your understanding with interactive quizzes, flashcards, and detailed explanations. Boost your confidence and readiness for exam success!

Acidifying urine is done to keep calcium, magnesium, and phosphate in solution and prevent the formation of insoluble salts that would skew measurements. A strong acid lowers the pH enough to dissolve potential precipitates like calcium phosphate and to stabilize the ions during the assay. Among common acids, hydrochloric acid is preferred because it is strong, provides a non-interfering chloride counterion, and is routinely used in clinical labs for urine acidification. Other acids can introduce interfering ions or cause precipitation or measurement issues: sulfuric acid can lead to calcium sulfate precipitation and interfere with some tests; nitric acid may affect certain colorimetric/oxidation-based assays; acetic acid is too weak to achieve the necessary acidity. So hydrochloric acid is the best choice for acidifying urine for Ca, Mg, or phosphorus testing.