A new approach to the analysis of nicarbazin and ionophores in eggs by HPLC/MS/MS.

An HPLC/MS/MS method has been developed and validated for the quantification and confirmation of nicarbazin and ionophores (lasalocid, monensin, salinomycin, and narasin) in eggs. Nicarbazin is determined in the negative electrospray mode with a basic mobile phase that supports creation of negative ions. Consequently, our ability to maintain instrument sensitivity over time has significantly improved. The analysis of the ionophores is done in the positive electrospray mode using ammonium buffer for HPLC separation. Monitoring ammonium adduct parent ions resulted in enhanced sensitivity and better reproducibility of the ionophore analysis. The validation of this improved HPLC/MS/MS method for the detection of nicarbazin and the ionophores demonstrated excellent precision of below 10% RSD and lower LOD values (microg/kg) for nicarbazin (0.018), lasalocid (0.015), monensin (0.015), salinomycin (0.033), and narasin (0.039).

Dynamic cytotoxic response to microcystins using microelectronic sensor arrays.

Microcystins are bioactive metabolites produced by cyanobacteria in water. These cyclic heptapeptides have caused public health concern worldwide. By interfering with cellular phosphorylation and signaling, microcystins can cause acute and chronic liver diseases. Therefore, the World Health Organization (WHO) has set the provisional drinking water guideline value at 1.0 microg/L for microcystin-LR (free plus cell-bound). Microcystins do not readily cross cell membranes in in vitro cell-based assays, except for those using freshly isolated hepatocytes. However, the sensitivity of in vitro cell-based assays is not adequate for testing samples at low environmental concentrations. Hence, there is a need to develop a sensitive and stable cytotoxicity assay for use in environmental studies. On the basis of the observation that microcystin-LR can be transported by the liver-specific members of the organic anion transporting polypeptides (OATPs), we investigated the potential of using an OATP1B3-expressing cell line in a cytotoxicity assay for microcystins. Using a novel cell electronic sensing system (RT-CES), we were able to monitor the real-time, dynamic cytotoxic response to microcystins at microgram per liter concentrations. We demonstrated that the cytotoxicity of the most common microcystins, -LR, -YR, -RR, -LF, and -LW, was mediated by OATP1B3 transporters. Microcystin-LF is the most potent toxin among the five congeners. In conclusion, we have established a highly automated, real-time, sensitive, and stable assay for measuring microcystin cytoxicity.

Determination of polychlorinated biphenyl congeners in human milk by gas chromatography-negative chemical ionization mass spectrometry after sample clean-up by solid-phase extraction.

This paper describes a simple and efficient procedure for measuring 25 congeners of polychlorinated biphenyls in human milk. The limit of quantitation was 0.1 ng/ml for five less chlorinated congeners (PCB 70, 74, 87, 99,101), and 0.01 ng/ml for the remaining 20 congeners (PCB 77, 105, 118, 126, 128, 138, 151, 153, 156, 169, 170, 180, 183, 187, 191, 194, 205, 206, 208 and 209). Solid phase extraction technology was applied to extract the analytes from the matrix and to remove lipids. Three columns were used sequentially, and they were a Bond Elut C(18), a Sep-Pak Plus NH2 and a Bond Elut PCB cartridge. The instrumental method was gas chromatography-mass spectrometry with negative chemical ionization, and selected ion monitoring mode was used.

Analysis of pesticides and PCB congeners in serum by GC/MS with SPE sample cleanup.

This paper describes a simple procedure for the quantitative analysis of 25 polychlorinated biphenyl congeners (PCB) in serum. They are PCB 70, 74, 77, 87, 99, 101, 118, 126, 128, 138, 151, 153, 156, 169, 170, 180, 183, 187, 191, 194, 205, 206, 208 and 209. In addition, 15 pesticides are analyzed in the same extract: aldrin, p,p'-DDE, p,p'-DDT, dieldrin, endrin, endosulfan I, heptachlor, hexachlorobenzene, alpha-hexachlorocyclohexane, beta-hexachlorocyclohexane, lindane, methoxychlor, mirex, pentachlorobenzene, and 1,2,3,4-tetrachlorobenzene. The procedure involved sample cleanup using a combination of C18 and NH(2) solid phase extraction cartridges. The instrumental technique was gas chromatography/mass spectrometry with both electron ionization and negative chemical ionization in the selected ion monitoring mode. Concentration of sub-ng/ml level was attainable with 2 ml of serum sample.