Which method would generally be preferred for measuring low concentrations of substances accurately?

Instrumental methods are typically preferred for measuring low concentrations of substances due to their high sensitivity, precision, and ability to detect minute quantities of analytes. Techniques such as HPLC (High-Performance Liquid Chromatography), mass spectrometry, and spectrophotometry fall under this category. These methods often employ sophisticated technology that can distinguish between small changes in concentration, ensuring accurate measurements at trace levels.

The capability of instrumental methods to automate processes also minimizes human error and enhances reproducibility, making them ideal for analytical scenarios that require the detection of low concentration levels. Furthermore, these methods often have built-in calibration systems that allow for more accurate and reliable quantification compared to traditional methods.

For example, colorimetry, while useful for certain applications, may not reach the sensitivity of advanced instrumental techniques. Similarly, titration and gravimetric analysis, although valuable for quantitative analysis, may not offer the same level of sensitivity for trace analysis as instrumental methods do. Thus, when it comes to accurately measuring very low concentrations, instrumental methods are the clear choice.