Abstract— An improved method for the measurement of catecholamines in brain parts has been developed, based on reverse‐phase ion‐pair chromatography. The new method offers the advantages of high efficiency microparticulate liquid chromatography packings and the flexibility of ion‐pair chromatography. By this approach norepinephrine and dopamine (DA) have been measured in the hypothalamus and corpus striatum of the rat brain during various stages of development (15, 21, 30 days). Data are reported on the basis of the whole part and per weight of tissue. For the adult animals, the following concentrations (ng/g wet tissue) were observed for the hypothalamus: NE = 2261 ± 274, DA = 440 ± 103, and for the corpus striatum: DA = 11,888 ± 1840. The overall precision of the method was ±5.6% relative s.d. The absolute recovery was 60 ± 5% relative s.d. and was constant over the range of 1 ng to 1 μg of dopamine or norepinephrine per tissue sample. The relative retention behavior of 18 neurologically important catechol derivatives is reported for reverse‐phase chromatography with octyl sulfate as the stationary phase modifier.

A liquid chromatographic method was developed for the analysis of indandione and 4-hydroxycoumarin anticoagulant rodenticides in blood serum and liver. The method enabled the measurement of serum and liver concentrations of eight anticoagulant rodenticides: brodifacoum, bromadiolone, chlorophacinone, coumafuryl, coumatetralyl, diphacinone, difenacoum, and warfarin. Anticoagulants were extracted from serum and liver with acetonitrile. Extracts were applied to solid-phase extraction columns, which contained mixed packings. Column eluates were evaporated to dryness, reconstituted, and subjected to reversed-phase liquid chromatography. Hydroxycoumarins were detected by fluorescence at an excitation wavelength of 318 nm and an emission wavelength of 390 nm. Indandiones were detected by UV absorption at 285 nm. Extraction efficiencies of greater than 75% for serum and greater than 69% for liver were obtained. The within-run precision (CV) ranged from 2.4 to 8.6% for serum and 2.6 to 8.7% for liver. The between-run precision (CV) ranged from 1.5 to 12.2% for serum and from 2.1 to 11.8% for liver. Hydroxycoumarin rodenticides were detected at 1 ng/mL of serum and 1 ng/g of liver. Indandiones were detected at 10 ng/mL of serum and 10 ng/g of liver.

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High-performance liquid chromatography can be combined with hydrodynamic thin-layer electrochemistry for determination of trace amounts of organic constituents in complex samples. With small and inexpensive analyzers based on these two techniques, as little as 1 pg of an electrochemically active component can be detected in a few minutes. Because many of the important low-molecular-weight organic constituents of body fluids— both endogenous metabolites and drugs—undergo electrochemical reactions, it seems reasonable to presume that useful assays might be developed by using the above methodology. Beginning to explore this presumption, we illustrate how uric acid, ascorbic acid, catecholamines, and related tyrosine metabolites might be measured in urine and serum. In some cases, liquid chromatography with electrochemical detection provides better sensitivity, selectivity, and speed than traditional methods, while minimizing the need for analytical reagents. We describe the basic approach and progress to date and suggest future applications.

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