SIM Method Research Articles

A novel approach to transforming a non-targeted metabolic profiling method to a pseudo-targeted method using the retention time locking gas chromatography/mass spectrometry-selected ions monitoring

Non-targeted metabolic profiling is the most widely used method for metabolomics. In this paper, a novel approach was established to transform a non-targeted metabolic profiling method to a pseudo-targeted method using the retention time locking gas chromatography/mass spectrometry-selected ion monitoring (RTL-GC/MS-SIM). To achieve this transformation, an algorithm based on the automated mass spectral deconvolution and identification system (AMDIS), GC/MS raw data and a bi-Gaussian chromatographic peak model was developed. The established GC/MS-SIM method was compared with GC/MS-full scan (the total ion current and extracted ion current, TIC and EIC) methods, it was found that for a typical tobacco leaf extract, 93% components had their relative standard deviations (RSDs) of relative peak areas less than 20% by the SIM method, while 88% by the EIC method and 81% by the TIC method. 47.3% components had their linear correlation coefficient higher than 0.99, compared with 5.0% by the EIC and 6.2% by TIC methods. Multivariate analysis showed the pooled quality control samples clustered more tightly using the developed method than using GC/MS-full scan methods, indicating a better data quality. With the analysis of the variance of the tobacco samples from three different planting regions, 167 differential components (p<0.05) were screened out using the RTL-GC/MS-SIM method, but 151 and 131 by the EIC and TIC methods, respectively. The results show that the developed method not only has a higher sensitivity, better linearity and data quality, but also does not need complicated peak alignment among different samples. It is especially suitable for the screening of differential components in the metabolic profiling investigation.

Evaluation of IPPSE, an alternative method for sequential population PKPD analysis

The aim of this study is to present and evaluate an alternative sequential method to perform population pharmacokinetic-pharmacodynamic (PKPD) analysis. Simultaneous PKPD analysis (SIM) is generally considered the reference method but may be computationally burdensome and time consuming. Evaluation of alternative approaches aims at speeding up the computation time and stabilizing the estimation of the models, while estimating the model parameters with good enough precision. The IPPSE method presented here uses the individual PK parameter estimates and their uncertainty (SE) to propagate the PK information to the PD estimation step, while the IPP method uses the individual PK parameters only and the PPP&D method utilizes the PK data. Data sets (n = 200) with various study designs were simulated according to a one-compartment PK model and a direct Emax PD model. The study design of each dataset was randomly selected. The same PK and PD models were fitted to the simulated observations using the SIM, IPP, PPP&D and IPPSE methods. The performances of the methods were compared with respect to estimation precision and bias, and computation time. Estimated precision and bias for the IPPSE method were similar to that of SIM and PPP&D, while IPP had higher bias and imprecision. Compared with the SIM method, IPPSE saved more computation time (61%) than PPP&D (39%), while IPP remained the fastest method (86% run time saved). The IPPSE method is a promising alternative for PKPD analysis, combining the advantages of the SIM (higher precision and lower bias of parameter estimates) and the IPP (shorter run time) methods.

HPLC/ESI‐MSn and ESI‐MS studies on the Aconitum alkaloids in three Chinese medicinal herbs

Aconitum lipo-alkaloids (LDAs) peaks in the previous HPLC studies have shown overlapping behavior, making it impossible to identify the total retention behavior of LDAs. The structural diversity of LDAs in Radix Aconiti, Radix Aconiti Kusnezoffii and Radix Aconiti Lateralis Preparata makes it difficult to synthesize and quantify each of them. Therefore, this study has been devoted to develop a HPLC/ESI-MS(n) method with good resolution of Aconitum alkaloids especially LDAs and then set up a fast ESI-MS SIM method to quantify the total contents of specific skeleton LDAs in the three herbs via in-source CID and the capability of mass separation. As a result, the retention behavior of LDAs was summarized based on an optimized chromatographic separation; 32 alkaloids from the three herbs of Aconitum genus were separated and identified according to their fragmentation pathways by using HPLC/ESI-MS(n). In addition, a fast quantitative analysis ESI-MS SIM method was successfully applied to the quantification of the total contents of specific skeleton LDAs in the three herbs.

Simultaneous determination of androstenedione, 11β-hydroxyandrostenedione, and testosterone in human plasma by stable isotope dilution mass spectrometry

This study describes a GC–MS method for the simultaneous determination of androstenedione (AD), 11β-hydroxyandrostenedione (11β-OHAD), and testosterone (TS) in human plasma. [19,19,19- 2H 3]Androstenedione (AD- 2H 3), 11β-hydroxy-[1,2,4,19- 13C 4]androstenedione (11β-OHAD- 13C 4), and [1,16,16,17- 2H 4]testosterone (TS- 2H 4) were used as internal standards. Pentafluoropropionic (PFP) derivatization with good GC behavior was employed for the GC–MS analysis of the three steroids. The detection limit of the present GC–MS–SIM method was found to be 1 pg per injection for AD (S/N ratio = 4.5), 5 pg for 11β-OHAD (S/N ratio = 5.0), and 1 pg for TS (S/N ratio = 4.4), respectively. Calibration curves were linear from 0.22 to 2.80 ng/mL ( r = 0.9998) for AD, from 0.56 to 3.19 ng/mL ( r = 0.9996) for 11β-OHAD, and from 2.05 to 10.3 ng/mL ( r = 0.9996) for TS. The intra- and inter-day assay reproducibilities in the amounts of the three androgens determined were in good agreement with the actual amounts added, the relative errors (R.E.) were −3.1 to 2.4%. The inter-assay relative standard deviation (R.S.D.) was less than 5.3%. The present method provides a sensitive and reliable technique for the simultaneous determination of AD, 11β-OHAD, and TS in plasma. The method can be applied to pharmacokinetic and metabolic studies of androgens with a particular interest in evaluating the conversion of AD to 11β-OHAD and the interconversion of AD and TS in humans.

Multiresidue Analysis of Pesticides in Agricultural Products by GC/MS Coupled with Database Software

We evaluated a multiresidue method for determination of pesticides in agricultural products by SCAN mode GC/MS coupled with three kinds of database for 253 pesticides: relative retention time, mass spectra and calibration curve (SCAN method). Twenty-six pesticides, a total of 131 pesticides were detected in samples by the SCAN method. The detection results agreed closely with those of the SIM mode GC/MS method using calibration standards (SIM method). The ratios of the SCAN method to the SIM method ranged from 0.3 to 3.1 with SD values of 0.63. It was judged that the SCAN method could be applied to the screening analysis of pesticide residues in agricultural products, provided that the sample preparation method makes it possible to effectively remove sample matrixes with minimal loss of analytes.

Transformation of Petroleum Saturated Hydrocarbons during Soil Bioremediation Experiments

This paper presents transformations of saturated hydrocarbons of petroleum type pollutants during ex situ bioremediation of soil on the pilot heap (halde), during a period of 6 months, within the grounds of Petroleum Refinery Pancevo (Serbia). Samples for analysis were taken in time intervals of 2 weeks (P1–P12 samples). Organic substance was extracted by Soxhlet’s method and quantified. Isoprenoid aliphatics, in particular pristane and phytane, and polycyclic aliphatics of sterane and triterpane types in saturated hydrocarbon fractions were analysed by GC-MS (SIM method). Significant amounts of n-alkanes have not been detected. The MS-chromatogram revealed only marginal amounts of pristane and phytane in sample P1. Pristane and phytane occurred in sample P8, and in even higher quantities in the final sample P12. The proceeding bioremediation process was accompanied by the decrease of the relative amounts of pentacyclic terpanes of hopane type, compared to tri- and tetracyclic terpanes. In the initial sample P1 the distribution of steranes and hopanes follows a pattern, which is characteristic for crude oils. However, their identification by SIM method was not possible in samples P8 and P12 because of the reduced concentration. The observed changes in the alkane fractions’ compositions may be considered as atypical, referring to the fact that during oil biodegradation under natural conditions, decomposition of isoprenoids occurs much easier and faster than decomposition of polycyclic alkanes of tri-, tetra- and pentacyclic terpane, sterane and diasterane types, after the decomposition of n-alkanes has been almost completed.

Simulation of Nakagami Fading Channels With Arbitrary Cross-Correlation and Fading Parameters

Nakagami fading model is widely used in modeling wireless communication systems. In this paper, we present methods to generate Nakagami fading signals with arbitrary cross-correlation and fading parameters by taking the square root of correlated Gamma random variables (RVs) with the corresponding shape parameters. To generate correlated Gamma RVs with different noninteger values of m-parameters, two methods, namely the decomposition method and Sim's method, are proposed. The former is more flexible and efficient. The latter is mathematically exact but carries constraints on the permissible simulation parameters. Simulations show that both methods produce outputs that match well with the specifications.

Indoor air pollution by alkylphenols in Tokyo.

The purposes of this study were to develop an analytical method for airborne alkylphenols (APs) using the gas chromatography/mass spectrometry (GC/MS)-SIM method and to investigate airborne C4-C9 APs pollution in houses, offices, and outdoor points in Tokyo. In addition, to identify APs emission sources in a newly built house, migration tests of APs from interior surfaces to solid extraction disks were performed. Air samples were collected from houses, offices, and outdoor points. The recovery of APs from air samples was increased by addition of ascorbic acid to the filters. 4-tert-butylphenol (4-t-BP), 4-tert-octylphenol (4-t-OP), and 4-nonylphenol (4-NP) were detected in both indoor and outdoor air. Their concentrations and detection frequencies were higher in indoor air than outdoor air. The maximum levels of 4-t-BP, 4-t-OP, and 4-NP in indoor were 387, 45.7, and 680 ng/m(3), respectively. 4-t-BP and 4-NP were detected with high frequencies (more than 97%) in indoor air samples. The concentrations of 4-t-BP, 4-t-OP, and 4-NP in indoor air were significantly correlated with room temperature (P < 0.01), and tended to be higher in newly built houses. The migration rates of APs from the floor, wall, and ceiling in the newly built house were higher in polyvinyl chloride coverings than in other materials. Practical Implications Alkylphenol ethoxylate (APE) are widely used surfactants in both industrial and domestic detergents. When these detergents are released into the environment, APE are biodegraded to the smaller chain ethoxylates and alkylphenols (APs). There are many reports about APs in aquatic environments because of their estrogenic effect on wildlife. In building materials, APs are used as antioxidant for polymer resins such as wall or floor coverings. Although APs has a lower vapor pressure, these agents are released into indoor air from the surface of polymer resins. This study surveyed concentrations of airborne AP in indoor air and outdoor air in Tokyo. In addition, to identify APs emission sources in a newly built house, migration tests of APs from interior surfaces to solid extraction disks were performed. Alkylphenol ethoxylate (APE) are widely used surfactants in both industrial and domestic detergents. When these detergents are released into the environment, APE are biodegraded to the smaller chain ethoxylates and alkylphenols (APs). There are many reports about APs in aquatic environments because of their estrogenic effect on wildlife. In building materials, APs are used as antioxidant for polymer resins such as wall or floor coverings. Although APs has a lower vapor pressure, these agents are released into indoor air from the surface of polymer resins. This study surveyed concentrations of airborne AP in indoor air and outdoor air in Tokyo. In addition, to identify APs emission sources in a newly built house, migration tests of APs from interior surfaces to solid extraction disks were performed.

SIM--simultaneous inverse filtering and matching of a glottal flow model for acoustic speech signals.

A new method "simultaneous inverse filtering and model matching" (SIM) is proposed that allows one to calculate voice source measures without any user interaction. It is based on the discrete all-pole modeling (DAP) technique for inverse filtering (IF), which is modified to include a model of the glottal flow as integral part [LF model, Fant et al., STL-QPSR (Stockholm) 4/1985, 1-13 (1986)]. As the correct LF parameters are initially unknown, they are estimated in an iterative procedure using multi-dimensional optimization techniques that are initialized according to the results of an exhaustive search. The error criteria applied reflect how well the IF is performed after the spectral contribution of the glottal flow has been removed. The resulting optimal LF parameter constellation serves as the basis to calculate 11 voice source measures. The performance was evaluated using synthesized signals and recordings of natural utterances. For the synthesized signals, the accuracy to reproduce the original parameters was high (correlations exceeding 0.88) for measures where the starting point of the glottal cycle did not enter explicitly. Errors were smaller compared to conventional estimation methods where the measures were estimated from the IF signal. The analysis of natural utterances indicates that problems still exist with regard to robustness, but that under advantageous conditions the open quotient, the speed quotient, the closing quotient, the parabolic spectral parameter, and the negative peak amplitude of the glottal flow derivative can indeed be determined automatically by the SIM method.

Simultaneous determination of endogenous and 13C-labelled cortisols and cortisones in human plasma by stable isotope dilution mass spectrometry

This study describes a capillary GC–MS method for the simultaneous determination of endogenous cortisol and cortisone and their 13C-labelled analogues, [1,2,4,19-13C4]cortisol (cortisol-13C4) and [1,2,4,19-13C4]cortisone (cortisone-13C4), in human plasma. [1,2,4,19-13C4,1,1,19,19,19-2H5]Cortisol (cortisol-13C4,2H5) and [1,2,4,19-13C4,1,1,19,19,19-2H5]cortisone (cortisone-13C4,2H5) were used as analytical internal standards. A double derivatization (bismethylenedioxy-pentafluoropropionate, BMD-PFP) with good GC behavior was employed for the GC–MS analysis of cortisol and cortisone. Quantitation was carried out by selected-ion monitoring of the molecular ions ([M]+·) of the BMD-PFP derivatives of cortisol and cortisone. The sensitivity limit of the present GC–MS–SIM method was found to be 150 pg per injection for cortisol (s/n=5.0) and 50 pg for cortisone (s/n=8.1). The within-day reproducibility in which the amounts of unlabelled and labelled cortisols and cortisones determined were in good agreement with the actual amounts added, the relative errors being less than 3.07%. The inter-assay coefficients of variation (C.V.) were less than 1.80% for unlabelled and labelled cortisols and cortisones.

Simultaneous determination of artemether and its major metabolite dihydroartemisinin in plasma by gas chromatography–mass spectrometry-selected ion monitoring

A sensitive, selective, and reproducible GC–MS–SIM method was developed for determination of artemether (ARM) and dihydroartemisinin (DHA) in plasma using artemisinin (ART) as internal standard. Solid phase extraction was performed using C 18 Bond Elut cartridges. The analysis was carried out using a HP-5MS 5% phenylmethylsiloxane capillary column. The recoveries of ARM, DHA and ART were 94.9±1.6%, 92.2±4.1% and 81.3±1.2%, respectively. The limit of quantification in plasma was 5 ng/ml (C.V.≤17.4% for ARM and 15.2% for DHA). Calibration curves were linear with R 2≥0.988. Within day coefficients of variation were 3–10.4% for ARM and 7.7–14.5% for DHA. Between day coefficients of variations were 6.5–15.4% and 7.6–14.1% for ARM and DHA. The method is currently being used for pharmacokinetic studies. Preliminary data on pharmacokinetics showed C max of 245.2 and 35.6 ng/ml reached at 2 and 3 h and AUC 0–8h of 2463.6 and 111.8 ngh/ml for ARM and DHA, respectively.

Catalytic Activity of Reduced MoO3/α-Al2O3 for Hexanes Reforming: I. Preparation, Characterization, and X-Ray Photoelectron Spectroscopy Studies

Different MoO3/α-Al2O3 catalyst samples have been prepared using two preparation methods for a MoO3 deposit, the first one consisting of aqueous impregnation with sodium molybdate and the second one starting from MoO3 by an equilibrium adsorption in slurry MoO3/water (called the SIM method: slurry impregnation or solvent assisted spreading method). The α-alumina support was obtained by heating γ-alumina at 1150°C. γ-alumina partially transformed to α-alumina by heating is used as catalyst support. For each kind of preparation two catalyst samples with different MoO3 loadings were prepared: 0.08 (around 0.04 equivalent monolayer) and 5.4 wt% (around 2.5 equivalent monolayers) and 1.2 (around 0.6 equivalent monolayer) and 5.2 wt% (around 2.4 equivalent monolayer) MoO3, respectively. They were characterized by X-ray diffraction, temperature programmed reduction, and X-ray photoelectron spectroscopy (XPS) measurements. In situ XPS measurements as afunction of reduction time and temperature were performed and compared on the 5.4% MoO3/α-Al2O3 and 1.2% MoO3/α-Al2O3 catalyst samples. The original oxidic form of each catalyst sample, before any reduction treatment, shows only the presence of Mo(VI) surface species. For high molybdenum concentrations, the complete disappearance of Mo(VI) into Mo(V) and Mo(IV) has been observed after treatment for 9 h under hydrogen at 350°C. After reduction for 5 h at 450°C, Mo(0) appeared. For concentrations close to the monolayer, treatments for 10 h under hydrogen at 450°C are necessary to reduce completely Mo(VI) into Mo(V) and Mo(IV); in that case, even a reduction at 700°C is insufficient to observe Mo(0) and only Mo(IV) and Mo(II) surface species are detected. Thus, increasing MoO3 loading results in an increase of the catalyst reducibility. No Al2(MoO4)3 seems to be present before and after reduction steps. Interaction of molybdenum oxide with alumina is discussed, depending on the molybdenum oxidic contents and on the preparation of the catalysts.

Determinations of PCB within a project to develop cleanup methods for PCB-containing elastic sealant used in outdoor joints between concrete blocks in buildings.

Determinations of PCB were carried out as part of a project aimed at developing cleanup methods for PCB-containing elastic sealant used in outdoor joints between concrete blocks. The goals of the project were to develop methods, which minimise the spread of PCB to the outdoor environment and to indoor air, and which keep the PCB levels as low as reasonably possible in the workplace environment whilst removing the elastic sealant. The following PCB determinations were carried out: (1) concentration in the elastic sealant; (2) concentration in the concrete close to the sealant; (3) concentration in soil; (4) concentration in the indoor air; and (5) concentration in the air in the workplace environment. The cleanup process consisted of a number of different steps: (1) cutting the elastic sealant with an oscillating knife; (2) grinding the concrete with a mechanical machine; (3) sawing the concrete with a mechanical saw and (4) cutting the concrete with a mechanical chisel. In all these different steps a high capacity vacuum cleaner connected to the machines was used. The elastic sealant contained 4.7 to 8.1% total PCB of a technical product with a composition most similar to Clophene A40. The concrete close to the sealant (first 2 mm) contained 0.12 and 1.7% total PCB at two different places. The pattern of the PCB in the concrete resembled that of the sealant. PCB concentrations in the soil from the ground close to the building were 0.1 and 0.3 ppm at two different places before the remedial action. The source of the PCB in the soil is most likely the sealant as the PCB pattern is similar for the two materials. The PCB levels in the workplace air at the beginning of the project, when the techniques were not fully developed, were generally above the occupational exposure limit of 10 micrograms m-3 (up to 120 micrograms m-3). Later when the techniques were optimised to better take care of dust and gases produced during the cutting and grinding etc., the levels were below or close to 10 micrograms m-3. The pattern of the PCB in the workplace air was different from that of the sealant and contained higher levels of lighter components. The PCB concentrations in the indoor air were measured before and during the remedial process. The levels were around 600 ng m-3 and there was no significant increase during the removal of the sealant. The PCB level after the remedial action will be measured later. The pattern of the PCB in the indoor air was different from that of the sealant as well as from that of the workplace air. Higher levels of the lighter PCB were present indoors compared to the composition in both workplace air and in sealant. Extracts of PCB were analysed by GC-MS with a SIM method (selected ion monitoring). Standard procedures were used for extraction of solid materials. For the air samples an OVS tube was used with XAD-2 as adsorbent. The filter and adsorbent were extracted with toluene. This work shows that it is important to perform remedial action of PCB-containing elastic sealant as: (1) there is a spread of PCB to the indoor air giving high enough concentrations to make this the main PCB load on humans living in the apartments studied in this project; (2) large amounts are spread to the soil from these sealants; and (3) many of the PCB-containing elastic sealants used need to be changed from a functional perspective.

Comparison of three methods for determining prostate gland volume in anticipation of conformal radiation treatment planning

With the advent of 3-dimensional computed axial tomography simulators (CT sim), more sophisticated conformal radiation treatment planning is possible. In order to estimate the accuracy of prostate volumes calculated by CT sim, the volumes obtained by CT sim and ultrasound (US) and diagnostic CT were compared. From April 1989 to December 1992, 212 prostate cancer patients were treated with conformal techniques guided by diagnostic CT. Fifty of them had their prostate volume determined by transrectal ultrasound (US). The prostate volumes calculated using diagnostic CT and US were compared. From April 1993 to May 1994, 186 patients were treated with conformal technique guided by CT sim. Eighty-three of them had their prostate volumes determined by ultrasound. The prostate volumes were determined using the ellipsoid model for each of the imaging methods (ultrasound, diagnostic CT, CT simulator). An additional integral method was available for determining volume with the CT simulator. The median ellipsoid model volume of the prostate gland was 40.3 cc by US and 54.4 cc by diagnostic CT. Correlation coefficient (r2) was 0.608 (P < 0.001). CT sim: The corresponding median ellipsoid model volumes were 37 cc by US, and 49.8 cc using the ellipsoid model by CT sim. The CT sim volume was 38.1 cc using the integral method. The r2 of the prostate volumes by US and CT sim (integral method) was 0.803 (P < 0.001). The prostate volume calculated using the integral method by CT sim was similar to the volume obtained using the ellipsoid model with US. The ellipsoid model method of calculation was significantly different from the ultrasound volume for both the diagnostic and CT sim method. The ellipsoid model calculation for US and the integral volume calculation for CT sim most closely approximates true gland size. Radiat Oncol Invest 1996;4:74–79. © 1996 Wiley-Liss, Inc.

Comparison of three methods for determining prostate gland volume in anticipation of conformal radiation treatment planning

With the advent of 3-dimensional computed axial tomography simulators (CT sim), more sophisticated conformal radiation treatment planning is possible. In order to estimate the accuracy of prostate volumes calculated by CT sim, the volumes obtained by CT sim and ultrasound (US) and diagnostic CT were compared. From April 1989 to December 1992, 212 prostate cancer patients were treated with conformal techniques guided by diagnostic CT. Fifty of them had their prostate volume determined by transrectal ultrasound (US). The prostate volumes calculated using diagnostic CT and US were compared. From April 1993 to May 1994, 186 patients were treated with conformal technique guided by CT sim. Eighty-three of them had their prostate volumes determined by ultrasound. The prostate volumes were determined using the ellipsoid model for each of the imaging methods (ultrasound, diagnostic CT, CT simulator). An additional integral method was available for determining volume with the CT simulator. The median ellipsoid model volume of the prostate gland was 40.3 cc by US and 54.4 cc by diagnostic CT. Correlation coefficient (r2) was 0.608 (P < 0.001). CT sim: The corresponding median ellipsoid model volumes were 37 cc by US, and 49.8 cc using the ellipsoid model by CT sim. The CT sim volume was 38.1 cc using the integral method. The r2 of the prostate volumes by US and CT sim (integral method) was 0.803 (P < 0.001). The prostate volume calculated using the integral method by CT sim was similar to the volume obtained using the ellipsoid model with US. The ellipsoid model method of calculation was significantly different from the ultrasound volume for both the diagnostic and CT sim method. The ellipsoid model calculation for US and the integral volume calculation for CT sim most closely approximates true gland size. Radiat Oncol Invest 1996;4:74–79. © 1996 Wiley-Liss, Inc.

Application of selective ion monitoring to the analysis of molecular species of vegetable oil triacylglycerols separated by open‐tubular column GLC on a methylphenylsilicone phase at high temperature

AbstractAnalyses of the molecular species of authentic triacylglycerols and of soybean triacylglycerols, which were separated on a fused silica open‐tubular column coated with a methylphenylsilicone gum stationary phase, were carried out by selective ion monitoring mass spectrometry. It was determined that peak assignments could be made by selecting certain characteristic ions with the same retention time on the SIM profile, that is, three ions of the type RCO+ corresponding to the fatty acyl residues (R1CO+, R2CO+ and R3CO+) and the corresponding three M‐acyl ions ([M‐OCOR1]+, [M‐OCOR2]+ and [M‐OCOR3]+ instead of the molecular ion. The yield of [RCO‐1]+ and [RCO‐2]+ and relating these to the unsaturated fatty acyl residues is inconvenient for an exact peak assignment. The SIM method was further applied to the peak assignment of the triacylglycerols from palm, cottonseed and safflower oils and certain new fatty acid combinations are proposed.

Determination of tributyltin compounds in fish by gas chromatography with ECD or mass spectrometry.

Gas chromatographic methods with 63Ni electron capture detection (GC-ECD) or mass spectrometry (selected ion monitoring, SIM) was investigated for the determination of tributyltin compounds in fish. Tributyltin compounds in a homogenized flesh sample of fish were extracted as tributyltin chloride (TBTC) with a hydrochloric acid-methanol mixture and transferred to a hexane solution. The extract was charged to an alumina column and eluted stepwise with ethyl acetate followed by hexane-ethanol (4 : 1, v/v) mixture. TBTC eluted with the latter solvent was transferred to a hexane layer by liquid-liquid extraction, and the hexane layer was concentrated by a rotary evaporator. The concentrate was subjected to gas chromatographic separation on a 10% KOCL-Sn column. The calibration curves were linear in the range of 0.1-2 μg/ml with GC-ECD and in the range of 0.05-1 μg/ml with SIM, respectively. The detection limit of TBTC was 0.005 μg/g in sample by the SIM method. Eleven samples of fish were analyzed by the GC-ECD and SIM methods, and the determined values by both the methods were in good agreement.

Revised method for the quantitative determination of 5-hydroxytryptamine in human plasma by gas chromatography—mass spectrometry—selected ion monitoring

To estimate the 5-hydroxytryptamine level in human plasma by gas chromatography—mass spectrometry—selected ion monitoring (GC—MS—SIM), a recovery method from plasma and derivatization conditions with pentafluoropropionic anhydride were investigated. By heating 5-hydroxytryptamine at 140°C for 4 h in the presence of pentafluoropropionic anhydride the peak intensity of derivatized 5-hydroxytryptamine increased more than three times in comparison with the reported method. There was a marked difference in the plasma levels of 5-hydroxytryptamine obtained using the GC—MS—SIM method compared to those obtained using fluorometric assay.