Methods for measuring pH of gel, paste, colloid, and aqueous solutions, such as a consumer product, a food product, a pet food product, a beverage product, a pharmaceutical product, and/or a medical product, are provided. The method may include preparing a calibration curve of a chemical species including or having an acid dissociation constant. Preparing the calibration curve may include plotting a chemical shift of the chemical species relative to pH. The method may also include determining a chemical shift of a gel, paste, and colloid, aqueous solutions, such as a consumer product, a food product, a pet food product, a beverage product, a pharmaceutical product, and/or a medical product, including the chemical species. The method may further include determining the pH of the gel, paste, colloid, and aqueous solutions, such as a consumer product, a food product, a pet food product, a beverage product, a pharmaceutical product, and/or a medical product, with the chemical shift of the product and the calibration curve.