Suh-Jen Jane Tsai

Determination of bile acids in pig liver, pig kidney and bovine liver by gas chromatography-chemical ionization tandem mass spectrometry with total ion chromatograms and extraction ion chromatograms

An effective method has been developed for quantitative determination of six bile acids including lithocholic acid (LCA), deoxycholic acid (DCA), chenodeoxycholic acid (CDCA), hydodeoxycholic acid (HDCA), cholic acid (CA) and ursodeoxycholic acid (UDCA) in biological tissues including pig liver, pig kidney and bovine liver by gas chromatography-chemical ionization/tandem mass spectrometry (GC-CI/MS/MS). Camphor-10-sulphonic acid (CSA) was proposed as effective catalyst for bile acid derivatization. Reactions were accelerated ultrasonically. The effects of different catalysts and reaction times on derivatization efficiency were evaluated and optimized. Bile acids were determined as methyl ester-trimethylsilyl ether and methyl ester-acetate derivatives. The efficiency of trimethylsilylation and acetylation was evaluated. Trimethylsilylation was done with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as the trimethylsilyl donating reagent in a ultrasonic bath for 20 min. Acetylation was done in pyridine with acetic anhydride at 40-45°C for 4 h. The former reaction was faster than the latter. Thus, trimethylsilylation was employed for the quantitative analysis. Negligible interferences from sterols in biological matrices were observed when the biological samples were treated with solid phase extraction before GC-CI/MS/MS. The linearity, reproducibility, detection limit and recovery were evaluated under the optimized conditions. Satisfactory results were obtained when bile acid derivatives of LCA, CDCA, HDCA, and UDCA were determined with total ion chromatograms (TIC) while DCA and CA were determined with extracted ion chromatograms (EIC), respectively. The detection limits (S/N=3) for six bile acids in biological tissues were ranging from 0.40 to 1.6 ng/mL and the recoveries indicated that the proposed method was feasible for the determination of trace bile acids in the biological samples studied. The experimental results for the animal tissues purchased from five different markets were compared. Interestingly, all of the six bile acids were present in pig liver while only the dihydroxy bile acids, DCA, CDCA and HDCA were found in pig kidney. In addition to DCA and CDCA, trihydroxy bile acid, CA, are the major bile acids in bovine liver.

Novel and efficient tag SNPs selection algorithms

SNPs are the most abundant forms of genetic variations amongst species; the association studies between complex diseases and SNPs or haplotypes have received great attention. However, these studies are restricted by the cost of genotyping all SNPs; thus, it is necessary to find smaller subsets, or tag SNPs, representing the rest of the SNPs. In fact, the existing tag SNP selection algorithms are notoriously time-consuming. An efficient algorithm for tag SNP selection was presented, which was applied to analyze the HapMap YRI data. The experimental results show that the proposed algorithm can achieve better performance than the existing tag SNP selection algorithms; in most cases, this proposed algorithm is at least ten times faster than the existing methods. In many cases, when the redundant ratio of the block is high, the proposed algorithm can even be thousands times faster than the previously known methods. Tools and web services for haplotype block analysis integrated by hadoop MapReduce framework are also developed using the proposed algorithm as computation kernels.

Silver and lanthanum as effective modifiers in trace determination of cadmium in nickel-base alloys by electrothermal atomic absorption spectrometry

Abstract Trace cadmium in nickel-base superalloys was determined by a stabilized temperature platform furnace using atomic absorption spectrometry with a deuterium arc background correction system. The volatility of cadmium limits the pyrolysis temperature. This prevents the removal of the interfering alloy matrix at the thermal pretreatment step. Hence, an enormously high background signal has been observed. Chemical modifiers including ammonium citrate, 1-(2-pyridylazo)-naphthol, 4-(2pyridylazo)resorcinol, 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol, Triton-X 100, EDTA, potassium nitrate, palladium nitrate, magnesium nitrate, aluminum chloride, ammonium dihydrogen phosphate, lanthanum oxide, lanthanum chloride and silver nitrate have been studied. Matrix interferences were effectively reduced by silver and lanthanum. The 100–300°C increase in the pyrolysis temperature effectively reduced the non-specific absorption from the alloy matrix. Interferences from foreign ions were also investigated. The merit of the proposed method was increased by the excellent agreement between the certified and the experimental values of Cd in the standard reference material, IN100, and the recovery obtained (100–104%). The precision of six successive replicate measurements was 4.9% with Ag modifier and 2.5% with La modifier, respectively. The results of analysing Tracealloy B were also satisfactory.

Determination of zirconium and molybdenum with 4,5-Dihydroxybenzene-1,3-disulfonic acid disodium salt by ion-pair reversed-phase high-performance liquid chromatography

An analytical process based on reversed-phase high-performance liquid chromatography, with ultraviolet/visible detection at 315 nm, was studied. 4,5-Dihydroxybenzene-1,3-disulfonic acid disodium salt (Tiron) was used as chelating agent. Optimum conditions for the determination of zirconium and molybdenum ions, including the concentration of the buffer, the pH of the chelating medium and the mobile phase, the concentration of Tiron, the time of colour development and the composition of the mobile phase, were investigated. Tiron chelates were eluted within 15 min, with methanol–water (63 + 37) as the mobile phase, which contained acetate buffer (1.5 × 10–3 mol l–1, pH 4.0), Tiron (1.5 × 10–3 mol l–1) and tetrabutylammonium bromide (3 × 10–2 mol l–1). The separation was performed with a C18 reversed-phase column. The proposed method was applied to the determination of ZrIV and MoVI in a relatively complex substance, nickel–base alloy. The precision and accuracy of the method were evaluated. The experimental values obtained from the calibration graphs and by the standard additions method were compared with the certified values. There was good agreement between these values. With five consecutive injections of 100 µl of sample solution, containing 200 ng each of ZrIV and MoVI, the recoveries obtained for Zr and Mo were 97 and 106%, respectively. The detection limits (signal-to-noise ratio = 3) were 9.0 and 3.6 ppb for ZrIV–Tiron and MoVI–Tiron, respectively.

Determination of trace amounts of thallium and tellurium in nickel-base alloys by electrothermal atomic absorption spectrometry

A method is described for determining trace amounts of Tl in nickel-base alloys using pre-treatment with ammonia solution and electrothermal atomic absorption spectrometry. Thallium was coprecipitated when the sample solution of a nickel-base alloy was treated with ammonia solution. Background absorption was effectively eliminated in the new matrix. Nickel worked effectively as a chemical modifier for Te, and raised the charring temperature from 500 to 1000 °C. Therefore, it was possible to determine sub-nanogram levels of Te without any complicated pre-treatment. The accuracy and precision of the proposed method were elucidated through the analysis of two nickel-base alloys: spectroscopic standard certified reference material 346A IN100 Alloy and Standard Reference Material 899 Tracealloy C. There was good agreement between the expected values and the results obtained. For Tl, the results found for IN 100 and Tracealloy C were 1.94 ± 0.09 µg g–1(sr= 5%) and 0.251 ± 0.005 µg g–1(sr= 2%), respectively, the reference value for IN100 being 2 and certified value for Tracealloy C being 0.252 ± 0.003 µg g–1. The recoveries for these alloys were 100 ± 4 and 102 ± 3%, respectively. The detection limit was 15 pg g–1. For Te, the certified values for IN100 and Tracealloy C were 9 ± 1 and 5.9 ± 0.6 µg g–1, respectively. The Te contents determined by the proposed procedure were 9.03 ± 0.09 µg g–1(sr= 1%) and 5.93 ± 0.26 µg g–1(sr= 4%), with recoveries of 98 ± 4 and 97 ± 4%, respectively. The detection limit was 35 pg g–1. Although the addition of Pd modifier gave a better detection limit (18 pg g–1), it led to poorer results in terms of accuracy, precision and recovery.

Quantitative analysis of manganese, chromium and molybdenum by ion-pair reversed-phase high-performance liquid chromatography with pre-column derivatization and UV-visible detection.

An ion-pair reversed-phase high-performance liquid chromatographic method with UV-visible spectrophotometric detection is proposed for the simultaneous determination of manganese, chromium and molybdenum. By using a C18-bonded silica column, 4-(2-pyridylazo)resorcinol (PAR) chelates of Mn(II), Cr(VI) and Mo(VI) were successfully separated and accurately determined at 480 nm. Tetrabutylammonium bromide (TBAB) was used as the ion-pair reagent. Effects of pH, the buffer system, the concentration of buffer, the color developing time, the concentration of chelating reagent and the ion-pair reagent on the resolution were investigated. PAR chelates were eluted within 20 min at a flow-rate of 1.0 ml min(-1) with a methanol aqueous mobile phase, CH3OH-water (20:80, v/v), containing 1.0 x 10(-3) mol l(-1) acetate buffer (pH 6.5), 1.8 x 10(-2) mol l(-1) TBAB and 2.0 x 10(-4) mol l(-1) PAR. The feasibility of the proposed method was verified with the standard reference materials of nickel-based alloys. The nickel-based alloys were analyzed chromatographically after ammonium pretreatment. Under the optimum conditions, the detection limits for the chelates of Mn(II), Cr(VI) and Mo(VI) were 0.31, 4.2 and 4.6 ng with 100 microl injection, respectively. The accuracy of the proposed chromatographic method was verified by good agreement between the values obtained by this method and certified values.

Determination of aluminium in nickel-based alloy samples using a longitudinal Zeeman-effect correction transversely heated graphite atomizer and a deuterium background correction end-heated graphite atomizer in electrothermal atomic absorption spectrometry

A method for the accurate determination of aluminium in nickel-based alloys has been developed. The technique includes the microwave decomposition of samples followed by analysis with electrothermal atomic absorption spectrometry (ETAAS). Longitudinal Zeeman-effect correction with a transversely heated graphite atomizer (Zeeman-THGA) and deuterium background correction with an end-heated graphite atomizer (Deuterium-HGA) were used. The effects of various modifiers including (NH4)2HPO4 , NH4H2PO4 , Mg(NO3)2 , Pd+Mg(NO3)2 , NH4NO3 , AgNO3 , KNO3 , K2Cr2O7 , ethylenediaminetetraacetic acid and Triton X-100 on the atomization of aluminium were studied. Of these, phosphate were relatively more effective than the other modifiers in terms of the optimization of sensitivity and minimization of the background absorption. The proposed methods were evaluated by determining aluminium contents in five certified reference materials of nickel-based alloys with aluminium contents ranging from 0.1127 to 5.5%. The best results were obtained with the (NH4)2HPO4 . Zeeman-THGA and Deuterium-HGA gave comparable accuracy and precision. The characteristic masses for Zeeman-THGA and Deuterium-HGA were 27 and 8.2 pg, respectively. This indicated that Deuterium-HGA was more sensitive than Zeeman-THGA. The detection limits for these two background correction systems were 9.6 and 22 pg, respectively. The precision obtained with both background corrections ranged from 0.7–2.0%.

Electrothermal atomic absorption spectrometric determination of copper in nickel-base alloys with various chemical modifiers☆

Abstract The analytical characteristics of copper in nickel-base alloys have been investigated with electrothermal atomic absorption spectrometry. Deuterium background correction was employed. The effects of various chemical modifiers on the analysis of copper were investigated. Organic modifiers which included 2-(5-bromo-2-pyridylazo)-5-(diethylamino-phenol) (Br-PADAP), ammonium citrate, 1-(2-pyridylazo)-naphthol, 4-(2-pyridylazo)resorcinol, ethylenediaminetetraacetic acid and Triton X-100 were studied. Inorganic modifiers palladium nitrate, magnesium nitrate, aluminum chloride, ammonium dihydrogen phosphate, hydrogen peroxide and potassium nitrate were also applied in this work. In addition, zirconium hydroxide and ammonium hydroxide precipitation methods have also been studied. Interference effects were effectively reduced with Br-PADAP modifier. Aqueous standards were used to construct the calibration curves. The detection limit was 1.9 pg. Standard reference materials of nickel-base alloys were used to evaluate the accuracy of the proposed method. The copper contents determined with the proposed method agreed closely with the certified values of the reference materials. The recoveries were within the range 90–100% with relative standard deviation of less than 10%. Good precision was obtained.

Determination of lead and bismuth in nickel-base alloys by graphite furnace atomic absorption spectrometry using continuum source background correction

Abstract The analysis of trace lead and bismuth in nickel-base alloys using the stabilized temperature platform furnace atomic absorption spectrometry (AAS) with deuterium background correction was investigated. The peak times of lead and bismuth were different in different matrices. Lead was determined directly without any chemical modifier since the background absorption caused by the alloy matrix was compensated by the continuum background corrector. Aqueous standards were used to construct the calibration curves. The high background absorption encountered in the determination of bismuth could not be eliminated by chemical modifiers, neither palladium nor ethylenediaminetetraacetic acid (EDTA). Background absorption was effectively reduced when trace bismuth was separated from the major matrix by coprecipitation with the addition of ammonium before determination by AAS. Hence, subnanogram levels of lead and bismuth in the aqueous solutions of nickel-base alloys were determined precisely with the optimum instrumental conditions established in this work. The accuracy and precision of the proposed methods were evaluated through the analysis of standard reference materials of nickel-base alloys. The experimental results agreed closely with the certified values and the reference values.

Cloud Computing-Based TagSNP Selection Algorithm for Human Genome Data

Single nucleotide polymorphisms (SNPs) play a fundamental role in human genetic variation and are used in medical diagnostics, phylogeny construction, and drug design. They provide the highest-resolution genetic fingerprint for identifying disease associations and human features. Haplotypes are regions of linked genetic variants that are closely spaced on the genome and tend to be inherited together. Genetics research has revealed SNPs within certain haplotype blocks that introduce few distinct common haplotypes into most of the population. Haplotype block structures are used in association-based methods to map disease genes. In this paper, we propose an efficient algorithm for identifying haplotype blocks in the genome. In chromosomal haplotype data retrieved from the HapMap project website, the proposed algorithm identified longer haplotype blocks than an existing algorithm. To enhance its performance, we extended the proposed algorithm into a parallel algorithm that copies data in parallel via the Hadoop MapReduce framework. The proposed MapReduce-paralleled combinatorial algorithm performed well on real-world data obtained from the HapMap dataset; the improvement in computational efficiency was proportional to the number of processors used.