Yunje Kim

Determination of four anabolic steroid metabolites by gas chromatography/mass spectrometry with negative ion chemical ionization and tandem mass spectrometry

A gas chromatography/mass spectrometry method is described which uses negative ion chemical ionization and tandem mass spectrometry for the determination of anabolic steroid metabolites. Four anabolic steroid metabolites to be derivatized by Pentafluoropropionic anhydride (PFPA) were determined using gas chromatography/mass spectrometry (GC/MS) with negative chemical ionization (NCI) and NCI/MS/MS. The repeatability and reproducibility of this procedure were in the range of 5.3-9.7% and 6.1-10.2%, respectively. This method of derivatization with PFPA for NCI and NCI/MS/MS was useful to determine four metabolites of nandrolone, dromostanolone, methenolone and boldenone. The derivatized metabolites of boldenone could be detected to 2 ppb and the other three steroids could be detected to 25 ppb in urine at a signal-to-noise ratio of S/N = 3.

The survey of PCDDs and PCDFs in the ambient air of the urban and industrial sites in Korea, 1998-99.

A comprehensive quality survey for PCDDs/PCDFs in ambient air has been studied in Korea for two years. Monitoring was undertaken at two locations throughout Seoul (urban site) and Incheon (industrial site) in winter and spring. The periods are during 16 to 17 March 1998, 21 to 22 January 1999 and 28 to 29 April 1999 (Seoul) and 25 to 26 March 1998, 18 to 19 January 1999 and 26 to 27 April 1999 (Incheon). The values of PCDDs/PCDFs in ambient air were expressed as concentrations and international TEF values. The contents of PCDDs/PCDFs in urban site (Seoul) were lower than in industrial site (Incheon). The measurements in wintertime were higher than in springtime. The contents of 2,3,4,7,8-PeCDF with half toxicity of 2,3,7,8-TCDD were high. Thus we assumed to have an interest to the contents of 2,3,4,7,8-PeCDF. In this study, sample size was small (sample number was only 18) and sampling period was limited by 24 h. Therefore, we need more widespread and long-term surveys in order to estimate the human exposure by inhalation.

Gas chromatographic-mass spectrometric analysis of mercaptan odorants in liquefied petroleum gas and liquefied natural gas

Abstract A gas chromatographic–mass spectrometric method for the determination of mercaptan odorants (dimethyl sulfide, tert .-butylmercaptan, tetrahydrothiophene) in natural gas has been developed. The gas sample filled in a 5 l Tedlar bag was introduced into the 0.5 ml volume of a sampling loop, separated on a 50 m capillary column coated with 5% phenylmethylsilicone and detected by a mass spectrometer. Natural gas samples collected from 124 sites were analyzed and the concentration of added odorants was found to be between 9.7 and 66.2 ppm (w/w). The detection limit of each odorant was below 1 ppm (w/w). The advantages of the developed technique were lower detection limits, elimination of interference peaks by introducing into the sampling loop system and selected-ion monitoring mode, and reduced total analysis time. The intra-day and inter-day precision of the established method was R.S.D. n =5).

Dietary assessment of human exposure to PBDEs in South Korea

This study was conducted to measure the concentration of PBDEs in various food stuffs from Korea and to estimate levels of PBDE intake from food for the Korean population according to geographical location and age. 20 types of food samples were collected from four heavily populated cities (Seoul, Gwangju, Daejeon, Pusan) and one rural city (Gangneung) and were analyzed for 19 polybrominated diphenyl ether congeners (BDE 15, 17, 28, 33, 47, 49, 66, 71, 85, 99, 100, 119, 126, 138, 153, 154, 183, and 209). No significant differences in total PBDE levels in foods were found among four large cities (Gwangju; 10.91 ng g(-1) wet weight (ww), Seoul; 7.66 ng g(-1)ww, Daejeon; 6.91 ng g(-1)ww, Pusan; 6.87 ng g(-1)ww) and one rural city (Gangneung; 8.72 ng g(-1)ww). Daily dietary intake of PBDEs does not appear to be related to the extent of urbanization. Total dietary intake of PBDE for the average general population was 72.30 ng d(-1) (not detected (ND)=0) which was similar to other countries. In all food groups, the largest contribution to PBDE intake was from fish and shellfish (48.96 ng d(-1)). Total PBDE consumed per kilogram of body weight was estimated to range from 2.70 ng kg(-1)d(-1) for infants 1 through 2 years of age to 0.85 ng kg(-1)d for 65 years and older and was highest in young children and decreased with increasing age.

Determination of the metabolites of gestrinone in human urine by high performance liquid chromatography, liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry.

Gestrinone was studied by high performance liquid chromatography (HPLC) for screening and by gas chromatography/mass spectrometry (GC/MS) for confirmation. When the chromatograms of blank, spiked urine and dosed urine were compared by HPLC, two unknown metabolites were found and these were excreted as the conjugated forms. Metabolites 1 and 2 were tested by LC/MS and LC/MS/MS and both had parent ions at m/z 325. The fragment ion of metabolite 1 was at m/z 263 and ions for metabolite 2 were m/z 307 [MH - H(2)O](+), 289, 279 and 241. LC/MS/MS of m/z 263 as the parent ion of metabolite 1 gave fragment ions at m/z 245 and 217, which were assumed to be [263 - H(2)O](+) and [235 - H(2)O](+), respectively. The trimethylsilyl (TMS)-enol-TMS ether derivative of gestrinone displayed three peaks in its GC/MS chromatogram, formed by tautomerism.

Determination and excretion study of gestrinone in human urine by high performance liquid chromatography and gas chromatography/mass spectrometry

Gestrinone was studied by HPLC for screening and by GC/MS for confirmation. Three unknown peaks were found by HPLC which are probably the metabolites of gestrinone, and conjugated gestrinone in dosed human urine. The metabolites and gestrinone were excreted as the conjugated forms. The total amounts of metabolite 1 and conjugated gestrinone, recovered after 48 h, were 0.20 and 0.32 mg, respectively. When metabolite 1 was tested by LC/MS and LC/MS/MS, the parent ion was m/z 327, [MH](+), and fragment ions were seen at m/z 309 [MH - H(2)O](+), 291 [MH - 2H(2)O](+), 283, 263 and 239. The TMS-enol-TMS ether derivative of gestrinone has three peaks in the GC/MS chromatogram formed by tautomerism. The reproducibility of the derivatization method was stable and recoveries were over 87% when spiked into blank urine.

Thickness effects on magnetic properties and ferromagnetic resonance in Co–Ni–Fe–N soft magnetic thin films

In this study, the magnetic properties and microstructures have been investigated in Co–Ni–Fe–N soft magnetic thin films with various film thicknesses (0.01–1.0 μm). As the film thickness decreases, the coercivity, electrical resistivity, and magnetic anisotropy field of these films increases from 1.1 to 7.9 Oe, 53 to 188 μΩ cm, and 20 to 70 Oe, respectively. In addition, excellent high frequency characteristics were achieved in Co–Ni–Fe–N films with thicknesses less than 0.3 μm, where an effective permeability of, ∼1000 was maintained out to 700 MHz. Analysis results from XRD, TEM, and FMR show that a 0.1-μm-thick film is composed of an amorphous phase. This amorphous phase gradually changes to a crystalline phase with increasing film thickness.

Levels of PCDDs and PCDFs in two kinds of fast foods in Korea

We initiated an attempt to gather preliminary Korean fast food data on the concentrations, whole weight and international toxic equivalent (TEQ), in two kinds of fast foods, hamburger and fried chicken. The levels of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDDs/PCDFs) in hamburgers are detected to be lower than in fried chickens. Total TEQ level of PCDDs in fried chicken is 47.45 times higher than in hamburger. In case of PCDFs, it is 48.61 times. Even though these are compared to the only one brand and three samples each, we think that these high levels of PCDDs/PCDFs in fried chicken are very important data because of the potentially increasing daily intake. If we continue to survey for PCDDs/PCDFs in fast foods more even, especially fried chicken, these data will be useful to calculate the estimated daily intake of TEQ levels of PCDDs/PCDFs in Korea.

PCDD and PCDF exposures in workers and controls living near an industrial waste incinerator

This study measured the levels of 17 congeners of PCDDs/PCDFs in serum to compare the levels between potentially exposed workers at an industrial waste incinerator and any residents with no known exposures. The 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDD were detected in serum of workers but in controls. Likewise, 1,2,3,7,8-PeCDF, 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDF were detected only in serum of workers. The international toxic equivalent (TEQ) levels of PCDDs/PCDFs in sera of workers are much higher than in controls. Among PCDDs, the proportion of total concentration and TEQ level is dominated predominantly by 1,2,3,6,7,8- and 1,2,3,7,8,9-HxCDD. We need extensive studies to estimate human exposure and are continuing this investigation.

The effect of organic solvents on the determination of cyclic boronates of some β-blockers by gas chromatography/mass spectrometry

Formation cyclic boronates for β-blockers, by use of triethylamine (TEA) and pyridine as catalysts, gives more effective product yield. Eleven β-blockers, formed by cyclic boronation with n-butylboronic acid and TEA, produced higher yields than by on-column thermal reaction and seven β-blockers were shown to give the highest yields in the phenyl cyclic boronation with pyridine or TEA by on-column thermal and general reaction. The phenyl cyclic boronate of nadolol produced one peak in the chromatogram and the n-butyl cyclic boronate showed two peaks. On-column derivatization with n-butylboronic acid and pyridine was effective in saving analysis time and for convenience, even though some n-butyl cyclic boronates by cyclic boronation with TEA gave a better yield. In n-butyl cyclic boronation with pyridine by on-column thermal reaction the detection limits were 0.1 to 4 ng/μL in urine with a signal-to-noise ratio of 10:1.