Biomedical subjects

Kang Tian

Publications and source records attributed to Kang Tian.

8 recordsLinked to original sources

PubMed2006

Development of an extraction method for perchlorate in soils.

Perchlorate originates as a contaminant in the environment from its use in solid rocket fuels and munitions. The current US EPA methods for perchlorate determination via ion chromatography using conductivity detection do not include recommendations for the extraction of perchlorate from soil. This study evaluated and identified appropriate conditions for the extraction of perchlorate from clay loam, loamy sand, and sandy soils. Based on the results of this evaluation, soils should be extracted in a dry, ground (mortar and pestle) state with Milli-Q water in a 1 ratio 1 soil ratio water ratio and diluted no more than 5-fold before analysis. When sandy soils were extracted in this manner, the calculated method detection limit was 3.5 microg kg(-1). The findings of this study have aided in the establishment of a standardized extraction method for perchlorate in soil.

Chromatography, Ion Exchange↗

PubMed2006

Assessment of pathogens and toxicants in New Orleans, LA following Hurricane Katrina.

Storm surge associated with Hurricane Katrina and the breach of levees protecting New Orleans, Louisiana allowed floodwaters from Lake Pontchartrain to inundate 80% of the city. Environmental samples were collected during September 16-18, 2005 to determine immediate human and wildlife health hazards from pathogens and toxicants in the floodwaters. Baseline information on potential long-term environmental damage resulting from contaminants in water and sediments pumped into Lake Pontchartrain was also collected. Concentrations of aldrin, arsenic, lead, and seven semivolatile organic compounds in sediments/soils exceeded one or more United States Environmental Protection Agency (USEPA) thresholds for human health soil screening levels and high priority bright line screening levels. High numbers of Aeromonas spp., pathogenic Vibrio spp., and other coliform bacteria were found in floodwater samples. Alligator and snake tissues did not contain excessive toxicant concentrations. Initial findings suggest numerous environmental contaminants are present in New Orleans and support the need for further evaluation of the extent of those threats.

Animals↗

PubMed2006

Liquid chromatography/electrospray ionization tandem mass spectrometry analysis of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX).

A quantitative liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method was developed for the analysis of the explosive, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). In negative ionization mode, HMX forms an acetate adduct ion [M + CH(3)COO](-), m/z 355, in the presence of a small amount of acetic acid in the mobile phase. The ESI collision-induced dissociation (CID) spectrum of m/z 355 was acquired and the transitions m/z 355 --> 147 and m/z 355 --> 174 were chosen for the determination of HMX in samples. Using this quantification technique, the method detection limit was 1.57 microg/L and good linearity was achieved in the range 5-500 microg/L. This method will help to unambiguously analyze environmentally relevant concentrations of HMX.

Azocines↗

PubMed2005

Optimization of operating conditions for the determination of perchlorate in biological samples using preconcentration/preelution ion chromatography.

Perchlorate originates as a contaminant in the environment from the use of salts in the manufacture of solid rocket fuels and munitions. Monitoring potential perchlorate contamination in the environment is of interest, however, very few analytical methods have been developed for perchlorate determination in biological samples. Analysis of complex samples by ion chromatography is complicated by matrix components that can interfere with perchlorate determination. However, a recently developed preconcentration/preelution (PC/PE) ion chromatography method has demonstrated the capability to analyze certain complex samples such as high salinity water, milk, and hydroponic fertilizers. The ability of this method to reduce sample background and lower detection limits in ion chromatography for various biological samples was evaluated in this study. The PC/PE method was applicable to the analysis of kidneys, livers, zebrafish, quail eggs, lettuce, and urine. Optimal operating conditions were determined for each matrix. Ranges of optimal wash volumes were shorter when 15 mM NaOH prewash solutions were used compared with 10mM and good recovery was achieved for most matrices with an injection period > or =60s. Prewash solution concentration did not appear to significantly affect matrix background. The PC/PE method was capable of reducing sample background when compared to EPA Method 314.0, which resulted in detection limits, with the exception of zebrafish and urine, that were two-fold lower than those achieved with EPA Method 314.0.

Animals↗

PubMed2005

Perchlorate and iodide in dairy and breast milk.

Perchlorate inhibits iodide uptake and may impair thyroid and neurodevelopment in infants. Recently, we unambiguously identified the presence of perchlorate in all seven brands of dairy milk randomly purchased from grocery stores in Lubbock, TX. How widespread is perchlorate in milk? Perchlorate in 47 dairy milk samples from 11 states and in 36 human milk samples from 18 states were measured. Iodide was also measured in a number of the samples. Perchlorate was detectable in 81 of 82 samples. The dairy and breast milk means were, respectively, 2.0 and 10.5 microg/L with the corresponding maximum values of 11 and 92 microg/L. Perchlorate is present in virtually all milk samples, the average concentration in breast milk is five times higher than in dairy milk. Although the number of available measurements are few at this point, for breast milk samples with a perchlorate content greater than 10 microg/L, the iodide content is linearly correlated with the inverse of the perchlorate concentration with a r2 of >0.9 (n = 6). The presence of perchlorate in the milk lowers the iodide content and may impair thyroid development in infants. On the basis of limited available data, iodide levels in breast milk may be significantly lower than it was two decades ago. Recommended iodine intake by pregnant and lactating women may need to be revised upward.

Animals↗

PubMed2005

The origin of naturally occurring perchlorate: the role of atmospheric processes.

Perchlorate, an iodide uptake inhibitor, is increasingly being detected in new places and new matrices. Perchlorate contamination has been attributed largelyto the manufacture and use of ammonium perchlorate (the oxidizer in solid fuel rockets) and/or the earlier use of Chilean nitrate as fertilizer (approximately 0.1% perchlorate). However, there are regions such as the southern high plains (Texas Panhandle) where there is no clear historical or current evidence of the extensive presence of rocket fuel or Chilean fertilizer sources. The occurrence of easily measurable concentrations of perchlorate in such places is difficult to understand. In the southern high plains groundwater, perchlorate is better correlated with iodate, known to be of atmospheric origin, compared to any other species. We show that perchlorate is readily formed by a variety of simulated atmospheric processes. For example, it is formed from chloride aerosol by electrical discharge and by exposing aqueous chloride to high concentrations of ozone. We report that perchlorate is present in many rain and snow samples. This strongly suggests that some perchlorate is formed in the atmosphere and a natural perchlorate background of atmospheric origin should exist.

Atmosphere↗

PubMed2003

Perchlorate in milk.

Perchlorate was unambiguously detected by ion chromatography-suppressed conductivity (IC-CD) and/or ion chromatography-electrospray mass spectrometry (IC-MS) in seven of seven supermarket milk samples bought randomly in Lubbock, TX. Quantitation by IC-MS and IC-suppressed conductivity detection in conjunction with a preconcentration-preelution method provided comparable results. With a sample cleanup procedure that involved protein removal by ethanol and sequential passage though activated alumina and C-18 silica, the limit of detection for perchlorate in milk was 0.5 microg/L. The levels found ranged from 1.7 to 6.4 microg/L. An evaporated milk sample contained perchlorate at 1.1 +/- 0.6 microg/L level, while we did not find detectable levels in a reconstituted powdered milk sample.

Animals↗

PubMed2003

Determination of trace perchlorate in high-salinity water samples by ion chromatography with on-line preconcentration and preelution.

A simple, automated system for the determination of trace perchlorate by ion chromatography (IC) with an online preconcentration technique is reported. The sample is preconcentrated, and less strongly held ions preeluted before the analyte is transferred to the principal separation system. This approach provides low limits of detection (LOD) and is particularly robust toward the effect of high concentrations of common anions, such as those present in groundwater samples. It compares favorably with currently promulgated EPA method 314.0. The LOD (S/N = 3) is 0.77 microg/L for a 2-mL reagent water sample and decreases more-or-less proportionately with increasing sample volume, at least up to 20 mL. Even with a sample of conductivity 14.7 mS/cm (approximately that of 0.1 M Na2SO4), the recovery of added perchlorate at the 25.0 microg/L level was still 92%. The concentration of added perchlorate in the range of 1-400 microg/L was linearly correlated to the peak area, with an r2 value of 0.9997. The recovery of perchlorate from artificial samples with different conductivity by the present method compares favorably with those from the currently recommended EPA Method. The ability of this approach to remove matrix interferences suggests that it would be also promising for perchlorate analysis in other challenging samples.

Fresh Water↗