Ink for ink-jet recording, ink cartridge, and ink-jet recording apparatus

An ink for ink-jet recording may contain a coloring agent and a marker. The coloring agent may contain a pigment. The marker may have a detector absorption peak for detecting the marker at a wavelength that is different from a wavelength of the maximum absorption peak of the coloring agent. The coloring agent and the marker may be contained in the ink in amounts that satisfy the following conditions (I) to (III): (I) about 1.2 A2/A3; (II) color difference ( E) about 3; and (III) about 1 A2 about 10 in terms of a measurement optical path length of 1 mm, where A2 denotes an absorbance at the wavelength of the detector absorption peak of the marker, A3 denotes a baseline absorbance at the wavelength of the detector absorption peak of the marker.