Determination of chlorinated phenols in surface-treated lumber by HPLC

A solution of internal standard in acetonitrile is used to extract samples of wood from lumber which had been commercially treated with chlorinated phenols. The tetrachlorophenol(TCP) and pentachlorophenol( PCP) were analytically separated from each other and from the other wood extractive compounds using a high performance liquid chromatograph (HPLC). The ultraviolet (UV) absorptions of the TCP, PCP, and internal standard were automatically measured as they eluted. The UV absorption peaks were integrated, and the amounts of TCP and PCP present were calculated with a dedicated microcomputer. Compared with the method previously used, this method is faster (up to 144 samples per 48 hours), has the same accuracy and precision, and it is linear over the concentration range used.     

A high-performance liquid chromatographic method for the determination of monofluoroacetate

A simple isocratic high-performance liquid chromatographic (HPLC) method for the quantitative analysis of monofluoroacetic acid (MFA), the toxic substance of Dichapetalum cymosum, in plant material, rumen contents (gastric contents), and liver samples is described. A suitable HPLC column that gives optimum sensitivity, accuracy, precision, and separation of MFA is identified. A C-610 organic acid analysis column at ambient temperature with 0.02M H3PO4 as an eluent and ultraviolet detection at 210 nm is utilized to quantitate MFA. Using this method, the average percentage recovery in plant material, bovine liver, and rumen samples is 94.8%, and a detection limit of 12 microg/L is achievable.     

An algebra of Stein operators

We build upon recent advances on the distributional aspect of Stein's method to propose a novel and flexible technique for computing Stein operators for random variables that can be written as products of independent random variables. We show that our results are valid for a wide class of distributions including normal, beta, variance-gamma, generalized gamma and many more. Our operators are kth degree differential operators with polynomial coefficients; they are straightforward to obtain even when the target density bears no explicit handle. As an application, we derive a new formula for the density of the product of k independent symmetric variance-gamma distributed random variables.