To ensure proper development, infants must receive the right amount of nutrients. Since their intake of minerals and trace elements in the first four months comes solely from mother milk or formula, valuable information about the uptake can derived by analyzing their excretion (in the form of feces or urine). Previous studies have used this approach but required convoluted collection of excretion before analysis.

This study investigates methods for non-invasive mineral uptake determination in babies, through measurement of minerals and trace elements in used diapers based on two analytical techniques, instrumental neutron activation analysis (INAA) and inductively coupled plasma optical emission spectroscopy (ICP-OES). This study compares the applicability of both techniques for different types of diapers. Furthermore, the representativeness of subsampling of diapers is investigated, and the elements that can be measured by the proposed methods are identified.

This study finds that Large Sample INAA (LSNAA) can be used to investigate used cloth diapers, assuming it is possible to measure cloth diapers individually. This method is able to measure potassium and probably sodium in urine, as well as potassium and potentially sodium, iron, and zinc in feces. The proposed method is as follows: The used diaper is dried and thereafter placed in the pot, with the empty space filled with cotton sheets. The samples are irradiated for 100 hours with a flux of 3.00 *1012 ± 0.02*1012 cm2s-1, followed by measuring the diapers after 2.5 and 19 days after irradiation. To determine the minerals in excretion, the minerals measured in the blank diaper are subtracted, which are determined by irradiating three blank diapers, with the same settings as the used diapers, and taking the average and standard deviation.

Furthermore, this study finds that ICP-OES can be used to measure potassium in disposable diapers containing urine. The proposed method is as follows: the area where the urine is located is dissolved using 6 mL nitric acid (65%) per 200 mg. The same area is dissolved three times for a blank diaper. The samples are filtered and diluted ± 8 times. Thereafter, the samples are measured using the ICP-OES device. To determine the minerals in urine, the measurements of the blank diaper are subtracted from the measurements of diaper with urine. Internal standards are used to compensate for differences between matrices. This approach assumes that differences between different sizes of diaper pieces are the result of matrix differences. The results from this study provide no conclusive evidence for the best dissolution method for a disposable diaper.