Standardization of the Romanowsky-Giemsa stain: the influence of staining time on the RG-staining pattern

In this paper the influence of staining time on the staining pattern of Romanowsky-Giemsa (RG) type stains is investigated. Smears of rabbit bone marrow and of human venous blood were stained with azure B-eosin Y, azure A-eosin Y and with the cationic dyes alone under varying conditions of staining time and dye concentration. The stained smears were investigated by integrating microdensitometry. DNA-polyacrylamide (PAA) model films were stained with azure A-eosin Y, the extinction of the stained model films was determined by spectrophotometry. With increasing staining time the color of the cell nuclei changed from blue to an intense purple, the texture of the nuclear chromatin became more prominent. Prolonged staining resulted in over-staining of the cell nuclei with loss of a distinct chromatin texture. Besides such factors as dye concentration and pH of the staining solution standardization of staining time may be considered necessary for the reproducibility of the RG staining pattern.