A modified version of the nonlinear iterative Chahine algorithm is presented and applied to the inversion of spectral extinction data for particle sizing. Simulated data were generated in a λ range of 0.2-2 µm,and particle-size distributions were recovered with radii in the range of 0.14-1.4 µm. Our results show that distributions and sample concentrations can be recovered to a high degree of accuracy when the indices of refraction of the sample and of the solvent are known. The inversion method needs no a priori assumptions and no constraints on the particle distributions. Compared with the algorithm originally proposed by Chahine, our method is much more stable with respect to random noise, permits a better quality of the retrieved distributions, and improves the overall reliability of the fitting. The accuracy and resolution of the method as functions of noise were investigated and showed that the retrieved distributions are quite reliable up to noise levels of several rms percent in the data. The sensitivity to errors in the real and imaginary parts of the refraction index of the particles was also examined.

Conflicting findings regarding the boldenone content of bovine faeces suggest it may be synthesized de novo in emitted faeces. We tested this hypothesis by analysing uncontaminated urine, fresh and various forms of dried faeces from 10 calves (not given boldenone) by liquid chromatography/tandem mass spectrometry for 17-and 17-boldenone ( and BOL); 1,4-androstadiene-3,17-dione (ADD); 4-androstene-3,17-dione (AED), testosterone (T) and epitestosterone (ET). Urine contained no BOL, BOL or ADD. The analysed substances were variably present in the rectal faeces, and at generally higher levels in faeces scraped from skin or stall floor. In pooled rectal faeces naturally dried for 13 days, BOL, ADD, AED and ET levels were extremely high (much higher than accounted for by increases due to drying), and BOL and T were absent. It is concluded that de novo synthesis of BOL and metabolites occurs naturally in bovine faeces and only uncontaminated urine should be analysed for illegal boldenone.

Particle-size distribution and the concentration of polystyrene particles suspended in water were accurately recovered from the inversion of spectral extinction data measured with a commercial spectrophotometer. The instrument was modified by placing a spatial filter in the collection optics to prevent low-angle scattered light from affecting the measurement of transmitted power. The data were inverted by use of a nonlinear iterative algorithm. When the extinction coefficient is measured in the lambda range of 0.3-1.1 microm, the particle distributions can be retrieved over a diameter range of 0.6-2.8 microm for a wide interval of sample concentrations. The average diameters are recovered with a precision of better than +/-1% and with accuracies consistent with the uncertainties by which the nominal diameters are known. The relative standard deviations of distributions corresponding to monodisperse samples are +/-5-10%, whereas the accuracy on the measured concentrations is approximately 5%.