Variation in growth rate, carbon assimilation, and photosynthetic efficiency in response to nitrogen source and concentration in phytoplankton isolated from upper San Francisco Bay.

Six species of phytoplankton recently isolated from upper San Francisco Bay were tested for their sensitivity to growth inhibition by ammonium (NH4+ ), and for differences in growth rates according to inorganic nitrogen (N) growth source. The quantum yield of photosystem II (Fv /Fm ) was a sensitive indicator of NH4+ toxicity, manifested by a suppression of Fv /Fm in a dose-dependent manner. Two chlorophytes were the least sensitive to NH4+ inhibition, at concentrations of >3,000 µmoles NH4+  · L-1 , followed by two estuarine diatoms that were sensitive at concentrations >1,000 µmoles NH4+  · L-1 , followed lastly by two freshwater diatoms that were sensitive at concentrations between 200 and 500 µmoles NH4+  · L-1 . At non-inhibiting concentrations of NH4+ , the freshwater diatom species grew fastest, followed by the estuarine diatoms, while the chlorophytes grew slowest. Variations in growth rates with N source did not follow taxonomic divisions. Of the two chlorophytes, one grew significantly faster on nitrate (NO3- ), whereas the other grew significantly faster on NH4+ . All four diatoms tested grew faster on NH4+ compared with NO3- . We showed that in cases where growth rates were faster on NH4+ than they were on NO3- , the difference was not larger for chlorophytes compared with diatoms. This holds true for comparisons across a number of culture investigations suggesting that diatoms as a group will not be at a competitive disadvantage under natural conditions when NH4+ dominates the total N pool and they will also not have a growth advantage when NO3- is dominant, as long as N concentrations are sufficient.

Determination of heroin and basic impurities for drug profiling by ultra-high-pressure liquid chromatography.

Rapid, precise, accurate, and reproducible methodology using ultra-high-pressure liquid chromatography (UHPLC) for the analysis of heroin and basic impurities is described. The determination of heroin, morphine, O3-monoacetylmorphine, O6-monoacetylmorphine, codeine, acetylcodeine, noscapine, and papaverine is accomplished using reversed-phase chromatography (RPC), employing a 1.7 µm Acquity UPLC BEH C18 column (2.1 mm × 150 mm) with a phosphate buffer (pH 1.6)-acetonitrile gradient and PDA detection. The target analytes are well resolved from each other and most adulterants in less than 20 min. For the few instances when adulterants interfere with target analytes, a 1.7 µm Acquity CSH Fluoro-Phenyl (2.1 mm × 150 mm) column is utilized with the same gradient conditions. The reported methodology can detect impurities as low as 0.02% relative to heroin, and is well suited for heroin profiling.