The concentrations of 35 trace elements in the UNS-SpS glass sand reference material have been determined by instrumental neutron activation analysis involving short- and long-term irradiations. For analysis, the so-called absolute monostandard method was used, i.e. the concentrations were calculated from the measured gamma-activity and not by comparison with a reference sample of known composition. The results of up to 25 independent determinations are compared with the values given by UNS and other investigators. Most element contents agree well with the published values expecting K, Ga, and La, which will be discussed. Trace element contents for Cl, As, Br, Dy, and Au are reported for the first time.