Multiple development bivariate

Other variations have been described by Szepesi and Nyiredy (1996) and Nyiredy (1996). Incremental multiple development (IMD) (Szabady et al., 1995 and 1997) involves rechromatography with the same composition mobile phase for distances that increase, usually by the same amount (linearly). If development occurs in the same direction with the same distance but different mobile phases having distinctive strength and selectivity, the method is termed gradient multiple development (GMD) this method most significantly increases the separation capacity of the system. In bivariate multiple development, the development distance and mobile phase composition are varied simultaneously for successive runs this method, which is effective for samples of differing polarity, has been used especially for preparative layer chromatography plates. 

Multiple development may also be performed in the same direction and development distance with different mobile phases gradient multiple development (GMD)). It is also possible to develop preparative plates, especially 0.5 mm layers, with the bivariate multiple development (BMD)... 

Bivariate MD (BMD) is the most complex multiple development technique, where the development distance and the mobile phase composition are varying simultaneously (D, Sj], 5/ri -> Dy Sjs, Sfi) during the successive chromatographic runs (see Figure 6). 

Effects of maternal blood lead at 36 weeks and birth, and of umbilical cord lead, upon trend of development in the first 30 days of life, as measured by the Brazelton Neonatal Behavioural Assessment Scale, were assessed by multiple regression techniques. Much of the significant bivariate effect of cord lead upon abnormal reflex trend could be accounted for by control variables. However, the difference between maternal lead at birth and cord lead remained significant in the multivariate model, accounting for 6.2% additional variance in outcome. Change in maternal lead between 36 weeks and birth was a significant predictor of abnormal reflex trend and trend in regulation of states. 

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