The absorption spectra and emission spectra in aqueous solution of three types of phthalocyaninesulfonates of aluminum are compared: IA, a trisulfonate formed by sulfonation of aluminum phthalocyanine, shows no evidence for dimerization in water with changing pH or ionic strength. IIA, a tetrasulfonate prepared by metalation of the tetrasulfonated free base using Al(acac)3, when added to water immediately shows spectra characteristic of a "contact dimer". IIIA, a tetrasulfonate prepared by condensation of sulfophthalic acid around A1C13, also shows dimer-like spectral changes, but they develop over 4 h. This "slow-forming dimer", like the "contact dimer", shows no emission but has a sharper red band. Comparison is made to similarly prepared phthalocyaninesulfonates of zinc: IZ, IIZ, IIIZ. Again, there is little dimer formation by IZ, although somewhat more than by IA. The zinc phthalocyaninetetrasulfonates, IIZ and IIIZ, show large amounts "contact dimer" but no "slow-forming dimer" spectrum, which is attributed to formation of a binuclear µ aluminum phthalocyaninetetrasulfonate.

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Preservation of chemical analytes in drinking water samples is necessary to obtain accurate information concerning contaminant occurrence. Sample preservation to prevent biodegradation is important for most samples and analytes. With the unique demands of environmental methods, it is not always possible to kill all microorganisms without having undesirable effects. To find a suitable preservative, the sample, analysis, and preservation needs should be considered. During method development of U.S. Environmental Protection Agency (EPA) Methods 526 (for unstable semivolatile compounds) and 532 (for phenylurea pesticides), a number of studies were conducted to identify compatible microbial inhibitors. Copper sulfate was successfully used in Method 532 and is an excellent firstchoice antimicrobial agent for many applications. Copper sulfate can catalyze hydrolysis reactions for some pesticides such as those analyzed in Method 526. Under these conditions, a nonmetal compound of antimicrobial activity must be considered. During the development of Method 526, a survey of alternate organic based antimicrobial compounds found that diazolidinyl urea worked well in the method. Several other candidate microbial inhibitors were identified that could have application to other environmental methods. A general approach to selecting antimicrobial compounds in future environmental methods in water matrixes is discussed.

The United States Environmental Protection Agency's Office of Ground Water and Drinking Water has developed a single-laboratory quantitation procedure: the lowest concentration minimum reporting level (LCMRL). The LCMRL is the lowest true concentration for which future recovery is predicted to fall, with high confidence (99%), between 50% and 150%. The procedure takes into account precision and accuracy. Multiple concentration replicates are processed through the entire analytical method and the data are plotted as measured sample concentration (y-axis) versus true concentration (x-axis). If the data support an assumption of constant variance over the concentration range, an ordinary least-squares regression line is drawn; otherwise, a variance-weighted least-squares regression is used. Prediction interval lines of 99% confidence are drawn about the regression. At the points where the prediction interval lines intersect with data quality objective lines of 50% and 150% recovery, lines are dropped to the x-axis. The higher of the two values is the LCMRL. The LCMRL procedure is flexible because the data quality objectives (50-150%) and the prediction interval confidence (99%) can be varied to suit program needs. The LCMRL determination is performed during method development only. A simpler procedure for verification of data quality objectives at a given minimum reporting level (MRL) is also presented. The verification procedure requires a single set of seven samples taken through the entire method procedure. If the calculated prediction interval is contained within data quality recovery limits (50-150%), the laboratory performance at the MRL is verified.