Sample comminution for mycotoxin analysis: dry milling or slurry mixing?

A comparison was made between dry milling and slurry mixing as a comminuting step preceding mycotoxin analysis. Sample schemes of up to 30 kg are mandated by European Commission legislation. Cocoa, green coffee, almonds and pistachio samples of 10 kg were milled by a Romer analytical sampling mill and all three subsamples were analysed for aflatoxin B1 or ochratoxin A content. The homogenization process was evaluated in terms of the analytical results, coefficients of variation for different mills and particle size distributions. Coefficients of variation for the comminuting step were higher for dry milling than for slurry mixing. This difference was explained based on measured particle size distributions for both milling types. Measurements also showed slight differences in mycotoxin content of samples based on milling procedures. This might lead to lots being wrongly accepted or rejected based on an erroneous subsample result. It was concluded that sample comminution was best performed by slurry mixing, which produced smaller particles and, consequently, homogeneous samples with lowest coefficients of variation. Additional data are given on analytical results in 10-kg subsamples that originate from the aggregate 30-kg sample as described in Commission Directive 98/53/EC.

[Development of computer software in ramp slope controller for treadmill ergometer].

We developed computer software to produce a treadmill ramp protocol through which oxygen uptake (VO2) is increased in a linear fashion, thus enabling subjects to walk until the end of exercise. The developed software simulates the increases in speed and grade of the treadmill displayed on a personal computer screen, and produces the ramp protocol by arbitrarily determining the variables of the following formula: 1) Increments of VO2 = a1t+a2 (ml/min/kg) [t = exercise time (min)] 2) Predicted VO2 by speed (S) and grade (G) = a3S2 + a4G2 + a5SG + a6S + a7G + a8 (ml/min/kg) [S = speed (km/hr); G = grade (%)] 3) Speed suitable for desired exercise time (S or S2) = a9t2 + a10t + a11 (km/hr) 4) Grade suitable for desired exercise time (G or G2) = a12t2 + a13t + a14 (%) In this study, the increment of VO2 was determined by considering the subject's exercise capacity (VO2 = 4t + 7 ml/min/kg), using the Ito's formula (VO2 = 0.067S2 + 0.289SG + 7.73 ml/min/kg). The formula of grade was determined following the formula arbitrarily (G2 = 25t + 5%). The formula of speed for exercise time was calculated automatically. The new ramp protocol, which was applied to 10 healthy subjects (mean age: 24.8 +/- 4.8 years old), disclosed a similar linear relationship between the predicted VO2 and the measured VO2.