A method for determining the reproductive status of mammals involves the steps of obtaining at periodic time intervals mucus samples from the cervix of a mammal, obtaining nuclear magnetic resonance spectra of the samples using a narrow line nuclear magnetic resonance spectrometer, determining the nuclear magnetic resonance ratios from the spectra on the basis of the relationship ##EQU1## and thereafter evaluating the reproductive status of the mammal from such ratios.

A method for monitoring pregnancy in a milk-producing domestic animal comprises determining the concentration of oestrogen conjugates, especially oestrone sulphate, contained in a sample comprising, or derived from, the milk of the animal and comparing this concentration with the average concentration of oestrogen conjugates in the milk of a non-pregnant similar animal of the same species. There is also provided a method for monitoring foetal well-being during the later stages of pregnancy which comprises, in addition, comparing the measured oestrogen conjugate concentration with that expected during a normal pregnancy.

A pipettable detector comprises an aqueous suspension of particles which are essentially insoluble in a sample of a body fluid containing at least one target ion analyte of interest, the particles having uniformly distributed therein target and indicator ionophores which may be present in the same molecule or separate molecules. The indicator ionophore is capable of giving rise to a detectable signal following complexation of the target ionophore with the target ion from the sample. In a method of detecting an ionic analyte of interest in the sample of a bodily fluid, the sample is contacted with the detector. The indicator ionophore gives rise to a detectable signal following complexation of the target ionophore with the target ion from the sample, and the signal is then detected.