Determining the metal content of cotton

Metal content of cotton is of increasing importance to cotton processors both because of effects on processing and product qualities and because of potential environmental concerns and constraints. Metals can contribute to problems that occur in yarn manufacturing, fabric production, bleaching and dyeing processes. Disposal of both liquid and solid wastes containing certain metals must be carefully monitored and controlled. Cottons varying in growth area, variety and harvest season were analyzed for potassium, magnesium, calcium, sodium, iron, copper, manganese, zinc, lead and cadmium contents by atomic absorption spectroscopy. Metal contents varied significantly between years and between growth areas. Potassium was the dominant metal (2000-6500 ppm) followed by magnesium and calcium (400-1200 ppm), sodium (100-300 ppm), iron (2090 ppm) and zinc, manganese and copper (1-10 ppm). Lead and cadmium were not detectable in any of the cottons at test sensitivity limits of about one ppm.