What does a refractometer measure in a laboratory setting?

A refractometer is an optical instrument used to measure the refractive index of a solution, which directly correlates to the concentration of dissolved solids in that solution. In a veterinary laboratory context, this is commonly utilized to determine total solids in biological fluids, such as blood or urine. A refractometer can help assess hydration status, kidney function, and other health indicators based on the concentration of solutes present.

The measurement of total solids is particularly crucial because it provides insights into various physiological conditions, such as dehydration or overhydration, allowing for proper diagnosis and treatment planning. The other options, while relevant to laboratory analysis, are not direct measurements obtained using a refractometer. For instance, pH levels are measured using a pH meter, specific gravity also relates to density comparison and can be gauged by other methods, and the concentration of electrolytes requires specific chemical analyses that do not utilize a refractometer.