• Analytical Science and Technology
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• v.12 no.6
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• pp.550-557
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• 1999

This Analysis was conducted for 13 toxic-PCBs having TEF value among 209 PCBs isomers in sediment by isotope dilution HRGC/HRMS method. From the result, the recovery of surrogate standard was in the range of 71~99%. The concentration range for 13 toxic-PCBs in sediment was found to be 0.84~2.49 ng/g, among them the concentration levels of 2,2',3,3',4,4',5-HpCB(IUPAC No. 170) and 2,2',3,4,4',5,5'-HpCB(IUPAC No. 180) represented almost 50% of total concentrarion and that of 2,3,4,4,5-PeCB(IUPAC No. 114) showed over 10%. The TEQ concentration levelwas in the range of 0.38~2.63 pg-TEQ/g and 3,3',4,4',5-PeCB(IUPAC No. 126) concentration represented over 50% of total TEQ concentration.

• Journal of the Korean Chemical Society
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• v.63 no.5
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• pp.387-391
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• 2019

• Mass Spectrometry Letters
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• v.5 no.2
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• pp.52-56
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• 2014

Glycated hemoglobin (HbA1c) is used as an index of mean glycemia over prolonged periods. This study describes an optimization of enzyme digestion conditions for quantification of non-glycated hemoglobin (HbA0) and HbA1c as diagnostic markers of diabetes mellitus. Both HbA0 and HbA1c were quantitatively determined followed by enzyme digestion using isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) with synthesized N-terminal hexapeptides as standards and synthesized isotope labeled hexapeptides as internal standards. Prior to quantification, each peptide was additionally quantified by amino acid composition analysis using ID-LC-MS/MS via acid hydrolysis. Each parameter was considered strictly as a means to improve digestion efficiency and repeatability. Digestion of hemoglobin was optimized when using 100 mM ammonium acetate (pH 4.2) and a Glu-C-to-HbA1c ratio of 1:50 at $37^{\circ}C$ for 20 h. Quantification was satisfactorily reproducible with a 2.6% relative standard deviation. These conditions were recommended for a primary reference method of HbA1c quantification and for the certification of HbA1c reference material.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.205-209
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• 2001

Uniformly-doped silicon thin films were fabricated by ion beam sputter deposition. The thin films had four levels of copper dopant concentration ranging between 1 ${\times}$1019 and 1 ${\times}$ 1021 atoms/cm3 . Concentrations of Copper dopants were determined by the isotope dilution inductively coupled plasma mass spectrometry (ICP-MS) to provide certified reference data for the quantitative surface analysis by secondary ion mass spectrometry (SIMS). The copper-doped thin films were dissolved in a mixture of 1 M HF and 3 M HNO3 spiked with appropriate amounts of 65 Cu. For an accurate isotope ratio determination, both the detector dead time and the mass discrimination were appropriately corrected and isobaric interference from SiAr molecular ions was avoided by a careful sample pretreatment. An analyte recovery efficiency was obtained for the Cu spiked samples to evaluate accuracy of the method. Uncertainty of the determined copper concentrations, estimated following the EURACHEM Guide, was less than 4%, and detection limit of this method was 5.58 ${\times}$ 1016 atoms/cm3.

• Mass Spectrometry Letters
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• v.1 no.1
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• pp.29-32
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• 2010

Cross reacting antibodies can cause an overestimation of the results of immunoassays. Therefore, alternative methods are needed for the accurate quantification of steroids. Gas chromatography combined with isotope-dilution mass spectrometry (GC-IDMS) is developed to quantify urinary active androgens, testosterone, epitestosterone and dihydrotestosterone, which are clinically relevant androgens to both hair-loss and prostate diseases. The method devised involves enzymatic hydrolysis with $\beta$-glucuronidase, solid-phase extraction, liquid-liquid extraction using methyl tert-butyl ether and subsequent conversion to pentafluorophenyldimethylsilyl-trimethylsilyl (flophemesyl-TMS) derivatives for sensitive and selective analysis in selected-ion monitoring mode. Flophemesyl-TMS derivatization not only eliminates matrix interference but also has a good peak resolution within a 6 min-run. A selective and sensitive GC technique with flophemesyl-TMS derivatives also allows accurate quantitative analysis of three active androgens when combined with IDMS. The limit of quantification of the three analytes was <50 pg/mL, and extraction recoveries ranged from 91.9 to 102.1%. The precision and accuracy were 1.2~6.5% and 89.0~106.7%, respectively. This GC-IDMS method can be useful for evaluating the drug efficacy and monitoring the biological processes responsible for male-pattern baldness and prostate diseases.

• Bulletin of the Korean Chemical Society
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• v.31 no.11
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• pp.3228-3232
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• 2010

Malachite green (MG) has been used world-widely in aquaculture as a parasiticide or fungicide. Although MG performed successfully, it has not been permitted for use in aquaculture from European Union, USA, and Canada because of its carcinogenicity and mutagenicity. We developed a sensitive and specific method to determine MG and its principal metabolite, leucomalachite green (LMG), respectively by isotope dilution liquid chromatography mass spectrometry (ID-LC/MS). To enhance the extraction recovery of MG and LMG from fish tissue, an additional step, saponification, was introduced in sample preparation process to remove fat in sample extract, which hampered the performance of SPE columns. The residue of MG and LMG in fish was analyzed using liquid chromatography mass spectrometry in the selected ion monitoring (SIM) mode by monitoring at m/z 329 and 334 for MG and $d_5$-MG and at m/z 331 and 337 for LMG and $^{13}C_6$-LMG, respectively. This method was validated by comparing with the value of the reference material provided by Laboratory Government Chemistry (LGC). The results agreed within the measurement uncertainty and the accuracy was much improved than the provided reference value by LGC.

• Analytical Science and Technology
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• v.27 no.6
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• pp.269-276
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• 2014

A short study for the uncertainty of post column isotope dilution method has been performed for the analysis of Selenomethionine in HPLC-ICP/MS. Major error sources studied were concentration and the flow rate of Se isotope solution, atomic weights of Se in spike and sample, and isotope ratio measured for the spiked sample. Uncertainties were obtained for each factor and the contribution for the total concentration uncertainty was 54.4% and 0.61%, 0.0072% and 0.018%, and 45.0%, respectively. The biggest contribution factor was concentration of the spike solution and the second was the isotopic ratio measured for the spiked sample solution. The mass flow rate of spike and atomic weights did not show much contribution. The calculated total uncertainty was $1.46ng{\cdot}g^{-1}$ for the standard SeMet ($126.30ng{\cdot}g^{-1}$). The experimental result was $127.09{\pm}1.46ng{\cdot}g^{-1}$ and the relative uncertainty was 1.20%.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.363-367
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• 2009

An isotope-dilution flow-injection electrospray/mass spectrometric method was developed for the accurate determination of glucosamine contents in pharmaceutical formulations. Samples were extracted by methanol. After spiking glucosamine-1-$^{13}C_1$ as an internal standard, the extracts were then analyzed by flow-injection ESI/MS in a selected ion monitoring (SIM) mode to detect [M+H]$^+$ ions of the analyte and its isotope analogue at m/z 180 and m/z 181, respectively. Confirmatory measurements were made by selectively monitoring the collisionally induced dissociation channels of m/z 180 $\rightarrow$ m/z 72 and m/z 181 $\rightarrow$73, respectively, to test the possibility of bias in the SIM method due to matrix interferences, but any significant bias in the SIM mode was not observed. Repeatability and reproducibility studies showed that the flow-injection ESI/MS method is a reliable and reproducible method which can provide a typical method precision of 1.0 %. Other results for the method validation are reported.

• The Journal of the Petrological Society of Korea
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• v.10 no.3
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• pp.190-201
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• 2001

Isotope Dilution Mass Spectrometry(IDMS) is one of the analytical method which uses enriched isotope spikes and analyzes the abundance of element by comparison of the spectrum between spiked mass and non-spike mass. Especially, the Thermal Ion Mass Spectrometry with isotope dilution technique (in general ID-TIMS) is the most accurate method of the chemical analysis, which enables us to obtain the data better than 1% in accuracy and precision. In IDMS, enriched isotope spike is one of the most important factor in order to obtain the best data. For rare earth elements, in general, a mixture of /sup 138/La, /sup 142/Ce, /sup 145/Nd, /sup 149/Sm, /sup 151/Sm, /sup 151/Eu, /sup 157/Gd, /sup 163/Dy, /sup 167/Er, /sup 171/Yb, and /sup 176/Lu is used as composite spike. IDMS is very useful in geochronology and REE geochemistry. Especially, it is very effective in studying the “tetrad effect” of rare earth elements in natural samples.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3663-3667
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• 2010

Acetaminophen (N-acetyl-p-aminophenol) is one of the most popular analgesic and antipyretic drugs. An isotope dilution mass spectrometric method based on LC/MS was developed as a candidate reference method for the accurate determination of acetaminophen in pharmaceutical product. After spiking an isotope labeled acetaminophen (acetyl-$^{13}C_2$, $^{15}N$-acetaminophen) as an internal standard, tablet extracts were analyzed by LC/MS in a selected reaction monitoring (SRM) mode to detect ions at m/z $152{\rightarrow}110$ and m/z $155{\rightarrow}111$ for acetaminophen and acetyl-$^{13}C_2$, $^{15}N$-acetaminophen, respectively. The repeatability and reproducibility of the developed ID/LC-MS method were tested for the validation and assessment of metrological quality of the method.