This document specifies a method for optimizing measurements of the total organic carbon (TOC) content in water samples containing high loads of suspended solids (SSs) with particulate organic carbon (POCsusp) (e.g., waste water, storm water, raw water, surface water, and sea water), following a combined ultrasonic and alkaline extraction (CUAL) sample-pretreatment method. The method shall use a turbidity ratio (i.e., NTU5/NTU0) to evaluate the adequacy the pretreatment for samples containing SSs as an evaluation index of sample homogeneity (10.2). The analysis procedure shall be outperformed instrumentally using a differential method (e.g., TC-TIC) to quantify TOC.