Gas Chromatography-mass Spectrometry-selected Ion Monitoring Research Articles

Analysis of Polycyclic Aromatic Hydrocarbons Using Magnetic Three-Dimensional Graphene Solid-Phase Extraction Coupled with Gas Chromatography–Mass Spectrometry

In this study, a composite material consisting of three-dimensional graphene aerogel and iron oxide nanoparticles (3DG/Fe3O4) was created and utilized for the purpose of magnetic solid-phase extraction (MSPE) of thirteen polycyclic aromatic hydrocarbon (PAH) compounds via gas chromatography–mass spectrometry/selected ion monitoring (GC-MS/SIM) analysis. The synthesized adsorbent underwent a range of characterization techniques, including scanning electron microscopy, vibrating sample magnetometry, Raman spectroscopy, X-ray diffraction, Brunauer–Emmett–Teller, Fourier transform-infrared spectroscopy, and Barrett–Joyner–Halenda techniques, to examine its properties and morphology. The synthesized adsorbent integrates the benefits of superior adsorption capacity from modified graphene oxide (GO) with the magnetic separability of magnetite microparticles, resulting in a high adsorption capacity with easy separation from sample solutions. The efficiency of the proposed method was optimized and modeled using a central composite design (CCD), which considered the primary factors influencing it. The optimal conditions were obtained as the adsorbent dosage of 10 mg, the extraction time of 4 min, and the salt concentration of 3% w/v. The limit of detection for the target PAHs was established to range from 0.016 to 0.2 ng mL−1 in optimal conditions, exhibiting a signal-to-noise ratio of 3. The linear dynamic range spanned from 5 to 100 ng mL−1, with determination coefficients (R2) ranging from 0.9913 to 0.9997. The intra- and inter-day precisions were calculated as relative standard deviations (RSDs) equal to 3.9% and 4.7%, respectively. The proposed method was successfully applied to the determination of PAHs in water samples (tap, river, and rainwater), and recoveries in the range of 71–110% (RSDs < 5.2%, n = 3) were obtained.

Molecular analysis of black coatings and anointing fluids from ancient Egyptian coffins, mummy cases, and funerary objects

Black organic coatings and ritual deposits on ancient Egyptian coffins and cartonnage cases are important and understudied sources of evidence about the rituals of funerary practice. Sometimes, the coatings were applied extensively over the surface of the coffin, resembling paint; in other cases, they were poured over the mummy case or wrapped body, presumably as part of a funerary ritual. For this study, multiple samples of black coatings and ritual liquids were taken from 20 Egyptian funerary items dating to a specific time period (c. 943 to 716 BC). Multiple sampling from each object enabled several comparisons to be made: the variability of the black coating within one application, the variability between two applications on one object, and the variability from object to object. All samples were analyzed for lipids using gas chromatography-mass spectrometry (GC-MS), and 51 samples from across the 20 items were further analyzed for the presence of bitumen using solid phase separation followed by selected ion monitoring GC-MS. The majority of the black substances were found to comprise a complex mixture of organic materials, including bitumen from the Dead Sea, conifer resin, and Pistacia resin, providing evidence for a continuation in international trade between Egypt and the eastern Mediterranean after the Late Bronze Age. Both the coating and the anointing liquid are very similar to mummification balms, pointing to parallels with Egyptian embalming rituals and raising questions about the practical aspects of Egyptian funerary practice.

Serum 4\u03b2-hydroxycholesterol increases during fluconazole treatment

PurposeThe antifungal drugs ketoconazole and itraconazole reduce serum concentrations of 4β-hydroxycholesterol, which is a validated marker for hepatic cytochrome P450 (CYP) 3A4 activity. We tested the effect of another antifungal triazole agent, fluconazole, on serum concentrations of different sterols and oxysterols within the cholesterol metabolism to see if this inhibitory reaction is a general side effect of azole antifungal agents.MethodsIn a prospective, double-blind, placebo-controlled, two-way crossover design, we studied 17 healthy subjects (nine men, eight women) who received 400 mg fluconazole or placebo daily for 8 days. On day 1 before treatment and on day 8 after the last dose, fasting blood samples were collected. Serum cholesterol precursors and oxysterols were measured by gas chromatography-mass spectrometry-selected ion monitoring and expressed as the ratio to cholesterol (R_sterol).ResultsUnder fluconazole treatment, serum R_lanosterol and R_24,25-dihydrolanosterol increased significantly without affecting serum cholesterol or metabolic downstream markers of hepatic cholesterol synthesis. Serum R_4β-, R_24S-, and R_27-hydroxycholesterol increased significantly.ConclusionFluconazole inhibits the 14α-demethylation of lanosterol and 24,25-dihydrolanosterol, regulated by CYP51A1, without reduction of total cholesterol synthesis. The increased serum level of R_4β-hydroxycholesterol under fluconazole treatment is in contrast to the reductions observed under ketoconazole and itraconazole treatments. The question, whether this increase is caused by induction of CYP3A4 or by inhibition of the catabolism of 4β-hydroxycholesterol, must be answered by mechanistic in vitro and in vivo studies comparing effects of various azole antifungal agents on hepatic CYP3A4 activity.

Operon Construction Containing alsS, ilvC, ilvD and kivd Genes in Esch-erichia coli for Isobutanol Production from Glucose

Isobutanol is a biofuel considered to be a potential gasoline substitute. However, isobutanol production is difficult because there is no native organism that can produce isobutanol. A biosynthetic pathway to produce isobutanol had been designed to utilize pyruvate produced from glucose breakdown by glycolysis in Escherichia coli (E. coli). This biosynthetic pathway con-sists of acetolactate-synthase (ALS), ketol-acid reductoisomerase (KARI), dihydroxy-acid dehydratase (DHAD), alpha-ketoisovalerate decarboxylase (KDC) and alcohol dehydrogenase (ADH) enzymes. Since E. coli does not have ALS and KDC, the genes coding for the protein is needed to be cloned and overexpressed in E. coli. KARI and DHAD were overexpressed to increase the accumulation of keto acid to increase isobutanol production. Plasmid contains an operon controlled by lac pro-moter and lac operator consisting of alsS (coded ALS from Bacillus subtilis), ilvC (coded KARI from E. coli MG1655) and ilvD (coded DHAD from E. coli MG1655) genes, obtained from previous research, and operon sequences have been confirmed by DNA sequencing. kivd gene (coding KDC from Lactococcus lactis) was obtained from iGEM 2013 kit. kivd was amplified by PCR and inserted into pJET 1.2 blunt. kivd gene was then added into 3’ end of previous operon using restriction-ligation tech-nique. The plasmid constructed was then transfered into E. coli DH5α using heat shock. The recombinant genes were expressed using IPTG (isopropyl-β-D-1-thiogalactopyranoside) induction. The SDS PAGE results were inconclusive, however isobutanol was detected by Gas Chromatography Mass Spectrometry – Selected Ion Monitoring (GC-MS-SIM) from 48 hours fermenta-tion culture at 30 oC (1,17%). An operon regulated by the lac promoter-operator containing four genes for the biosynthesis of isobutanol has been constructed and cloned in E. coli. The isobutanol production was not optimal due to weak expression and repression by glucose, which was used as substrate.

Application of Selected Ion Monitoring-Gas Chromatography Mass Spectrometry (SIM-GCMS) for Quantification of Poly Aromatic Hydro Carbons in Surface Water from Sarawak, Mambong River (Malaysia)

Background: Increasing activities have led to serious environmental problems due to Pullution caused by toxic materials such as poly aromatic carbons whose levels are rising in the environment.
 Objective: The study presented here carried out the ultra-trace Quantification of Poly Aromatic Hydro carbons in surface water using Selected Ion Monitoring with optimization Gas Chromatography Mass Spectrometry parameter.
 Methods: A Shimadzu QP 2010 Plus GCMS equipped with an auto-injector AOC-20i, 30 m x 0.25 mm x 0.25 um of BP-X5 capillary column (SGE, USA) was used to obtain the result of poly aromatic hydrocarbons to separate and quantify the PAH compounds as well as to identify the Polyromantic Hydrocarbon using USEPA.
 Results: The amount of polycyclic aromatic hydrocarbons (PAHs) at ultra-trace level in the surface water samples was estimated. Sixteen Poly Aromatic Hydro carbons were identified among which Naphthalene Pyrene (45.7 ng/L), Chrysene (59.38 ng/L), Benzo (g, h, i) perylene (40.35 ng/L) as the major pollutants in the water surface of Mambong River water. Total Poly Aromatic Hydro carbons (PAHs) concentrations ranged from 2.0 to 40 ng L-1 was detected in the river water.
 Conclusion: The Selected Ion Monitoring -Gas Chromatography Mass Spectrometry (SIM-GCMS) can be considered as sensitive and robust method to analyse PAHs contamination in environmental samples. Thus, help the researchers to uncover the critical areas of environmental pollution at ultra-trace level that many researchers were not able to explore.

Bio-based succinic acid sample preparation and derivatization procedure optimisation for gas chromatography-mass spectrometry analysis

This study focused on bio-based succinic acid sample preparation and derivatization conditions optimization using GC-MS analytical method. Succinic acid, the precursor of a wide range bio-compounds, especially it is important in accumulation of mitochondrial metabolite succinate (citric acid cycle) and during ischemia controls reperfusion injury through mitochondrial reactive oxygen production. Accurate determination of analytes is the key in metabolomics to use as low molecular biomarkers in case to improve diagnostic methods. Methods. Gas chromatography-mass spectrometry (GC-MS) method. For the quantitative determination of the succinic acid applied derivatization process by silylation using -bis- (trimethylsilyl) -trifluoroacetamide (BSTFA). Results. The derivatization agent BSTFA, the derivatization time of 3-4 hours and derivatization temperature at 70 °C were selected as the optimal derivatization condition for quantification of succinic acid by GС/MS in biological samples. The results show that GC-MS SIM method with evaporation was the most effective to quantify succinate in biological samples after ischemia/reperfusion injury. Selected ion monitoring (SIM) allowed to monitor a subset of fragments with their related mass values in a certain retention time (RT) range for a set of targets. Conclusions. DC – MS has several advantages for measurements of succinate concentration in small kidney tissue samples (lyophilized mitochondria). The method can be applied in small pieces of tissue - biopy samples, tissues from various organs

Determination of trace water contents of organic solvents by gas chromatography-mass spectrometry-selected ion monitoring

This paper describes the development of a novel gas chromatography-mass spectrometry-selected ion monitoring (GC/MS-SIM) method for the determination of trace water contents of organic solvents, using the characteristic m/z 18, m/z 17, and m/z 16 ions of H2O as the qualitative ion and the m/z 18 ion as the quantifier ion. The accuracy and precision of this method were validated. An excellent linear correlation was obtained for trace water contents between 0 and 0.5217 wt%, with a correlation coefficient (R2) of 0.9999, in addition to spike recoveries of 82.6–112.6%, and relative standard deviations (n = 6) of 0.4–7.2%. The limit of detection (S/N = 3) and limit of quantitation (S/N = 10) for the trace water contents of organic solvents were 0.0005% wt% and 0.0016% wt%, respectively.The analytical results confirmed that this method was useful for determining the trace water contents of organic solvents, because it has a low detection limit and wide linear range. It requires only small amounts of the samples and enables sample batch analysis. It is very environmentally friendly and saves reagents.

Occupational exposure to bisphenol A (BPA) in a plastic injection molding factory in Malaysia.

The purpose of this study has been to assess ambient bisphenol A (BPA) levels in workplaces and urine levels of workers and to establish a BPA database for different populations in Malaysia. Urine samples were collected from plastic factory workers and from control subjects after their shift. Air samples were collected using gas analyzers from 5 sampling positions in the injection molding unit work area and from ambient air. The level of BPA in airborne and urine samples was quantified by the gas chromatography mass spectrometry - selected ion monitoring (GCMS-SIM) analysis. Bisphenol A was detected in the median range of 8-28.3 ng/m³ and 2.4-3.59 ng/m³ for the 5 sampling points in the plastic molding factory and in the ambient air respectively. The median urinary BPA concentration was significantly higher in the workers (3.81 ng/ml) than in control subjects (0.73 ng/ml). The urinary BPA concentration was significantly associated with airborne BPA levels (ρ = 0.55, p < 0.01). Our findings provide the first evidence that workers in a molding factory in Malaysia are occupationally exposed to BPA. Int J Occup Med Environ Health 2017;30(5):743-750.

Determination of cembrenediols in tobacco by gas chromatography—mass spectrometry-selected ion monitoring with precolumn derivatization

An efficient and sensitive analytical method based on precolumn derivatization and gas chromatography—mass spectrometry—selected ion monitoring (GC—MS—SIM) was proposed and validated for analysis of two cembrenediols (CBDs) which are α-cembrenediol and β-cembrenediol in tobacco samples. CBDs in tobacco samples were extracted by sonication with 50 mL dichloromethane for 10 min before derivatized with 2:3 (v/v) bis(trimethylsilyl)trifluoroacetamide (BSTFA)—pyridine at 20 °C for 100 min. CBDs’ level in tobacco samples was analyzed by GC—MS—SIM and quantified by the internal standard method. The linear range for α-CBD and β-CBD was 13.6–554.6 μg mL−1 and 4.11–162.6 μg mL−1, and the correlation coefficients of both were 0.9998. The limit of detection (LOD) and limit of quantification (LOQ) of α-cembrenediol and β-cembrenediol were 0.40 μg g−1 and 1.34 μg g−1, and 0.27 μg g−1 and 0.90 μg g−1, respectively. Average recoveries of α-CBD and β-CBD were 94.4–99.9% and 91.9–98.2% while the relative standard deviations (RSDs, n = 5) were ranged from 2.67 to 5.6% and 2.04 to 4.22%, respectively. This proposed analytical method has been successfully applied to analyze CBDs in tobacco samples.

Endogenous hormone concentrations correlate with fructan metabolism throughout the phenological cycle in Chrysolaena obovata.

Chrysolaena obovata, an Asteraceae of the Brazilian Cerrado, presents seasonal growth, marked by senescence of aerial organs in winter and subsequent regrowth at the end of this season. The underground reserve organs, the rhizophores, accumulate inulin-type fructans, which are known to confer tolerance to drought and low temperature. Fructans and fructan-metabolizing enzymes show a characteristic spatial and temporal distribution in the rhizophores during the developmental cycle. Previous studies have shown correlations between abscisic acid (ABA) or indole acetic acid (IAA), fructans, dormancy and tolerance to drought and cold, but the signalling mechanism for the beginning of dormancy and sprouting in this species is still unknown. Adult plants were sampled from the field across phenological phases including dormancy, sprouting and vegetative growth. Endogenous concentrations of ABA and IAA were determined by GC-MS-SIM (gas chromatography-mass spectrometry-selected ion monitoring), and measurements were made of fructan content and composition, and enzyme activities. The relative expression of corresponding genes during dormancy and sprouting were also determined. Plants showed a high fructan 1-exohydrolase (EC 3.2.1.153) activity and expression during sprouting in proximal segments of the rhizophores, indicating mobilization of fructan reserves, when ABA concentrations were relatively low and precipitation and temperature were at their minimum values. Concomitantly, higher IAA concentrations were consistent with the role of this regulator in promoting cell elongation and plant growth. With high rates of precipitation and high temperatures in summer, the fructan-synthesizing enzyme sucrose:sucrose 1-fructosyltransferase (EC 2.4.1.99) showed higher activity and expression in distal segments of the rhizophores, which decreased over the course of the vegetative stage when ABA concentrations were higher, possibly signalling the entry into dormancy. The results show that fructan metabolism correlates well with endogenous hormone concentrations and environmental changes, suggesting that the co-ordinated action of carbohydrate metabolism and hormone synthesis enables C. obovata to survive unfavourable field conditions. Endogenous hormone concentrations seem to be related to regulation of fructan metabolism and to the transition between phenophases, signalling for energy storage, reserve mobilization and accumulation of oligosaccharides as osmolytes.

Analysis of Cembranoids in Flue‐cured Tobacco by Accelerated Solvent Extraction and Gas Chromatography‐Mass Spectrometry‐Selected Ion Monitoring

AbstractAn efficient and sensitive analytical method based on accelerated solvent extraction (ASE) and gas chromatography‐mass spectrometry‐selected ion monitoring (GC‐MS‐SIM) was developed and validated for analysis of cembranoids in flue‐cured tobacco leaves. Extraction efficiency of different pretreatment methods including liquid‐solid extraction (LSE), ultrasound‐assisted extraction (UAE), Soxlet extraction and accelerated solvent extraction (ASE) was compared and ASE was chosen as the optimal extraction method. During ASE procedure, effect of four parameters on extraction efficiency was considered and the experimental conditions were selected as follows: extraction solvent: dichloromethane; oven temperature: 50 °C; static time: 5 min and number of cycles: 2. Working standards of cembranoids were isolated by silica gel column chromatography and the identification was performed by mass spectrometry. Performance characteristics such as linearity, limit of detection (LOD), limit of quantitation (LOQ), precision and recovery were studied. The LOD and LOQ values were ranging from 5.0 × 10−3 to 6.9 × 10−3 μg/mL and 1.7 × 10−2 to 2.3 × 10−2 μg/mL for all analytes. At three different spiked levels, recoveries for CBT‐ol, α‐CBT‐diol and β‐CBT‐diol were 94.6%‐105.1%, 93.0%‐97.2% and 88.7%‐107.5% while the relative standard deviations (RSDs) were in the ranges of 3.9%‐6.2%, 1.8%‐8.7% and 1.7%‐6.0%, respectively. The proposed analytical methodology was successfully applied in the analysis of cembranoids in tobacco samples.

Polyhydroxyalkanoate production from unexplored sugar substrates

Industrial-scale production of biopolymers is restricted by its elevated production costs in comparison with those associated with synthetic (no-biodegradable and no-biocompatible) polymers. In this study we tested for the first time two low-cost carbon substrates (i.e. carob pulp and fique juice) for lab-scale production of polyhydroxyalkanoate (PHA) with Bacillus megaterium. PHA detection and quantification was conducted by gas chromatography/mass spectrometry-selected ion monitoring (GC/MS-SIM). The results suggest that PHA production using carob pulp (from Hymenaea courbaril) may be as high as with sugar cane molasses. Moreover, it could serve for the synthesis of the most commercialized type of PHA (i.e. polyhydroxybutyrate; PHB) and/or other varieties (e.g. polyhydroxy-butyrate-co-valerate; PHBV) with different properties and potential applications.

Direct determination of flavor relevant and further branched-chain fatty acids from sheep subcutaneous adipose tissue by gas chromatography with mass spectrometry

4-Methyloctanoic acid, 4-ethyloctanoic acid and 4-methylnonanoic acid are key-flavor compounds of sheep and goat. Yet, the low amounts of these volatile branched-chain fatty acids (vBCFAs) in the fat of the ruminants hampered their determination on a routine basis. In this work we developed a gas chromatography/mass spectrometry selected ion monitoring (GC/MS-SIM) method for the direct determination of the vBCFAs as methyl esters, which were obtained after transesterification of subcutaneous adipose tissue of sheep. The excellent sensitivity of the GC/MS-SIM method (limit of quantification, LOQ, 3.6–4.8μg/g; limit of detection, LOD, 1.1–1.4μg/g for 4-Me-8:0, 4-Et-8:0 and 4-Me-9:0) enabled us to determine the three vBCFAs without an enrichment step. Subcutaneous adipose sheep tissue of three different breeds contained 23–88μg/g 4-methyloctanoic acid, 13–26μg/g 4-ethyloctanoic acid and ∼2.9–18μg/g 4-methylnonanoic acid. Since all fatty acids were present in the FAME fraction, the samples could be screened for further branched-chain FAMEs. After elimination of unsaturated fatty acids by hydrogenation (the presence of some unsaturated fatty acids could be verified by this measure), additional measurements in SIM and full scan modes of methyl esters and picolinyl esters enabled the determination of further 97 saturated fatty acids in the samples with eight to 20 carbons. The method is suited for routine analysis and may be useful to investigate the reasons for the abundance/absence of 4-methyloctanoic acid, 4-ethyloctanoic acid and 4-methylnonanoic acid and further branched-chain fatty acids in sheep and goat.

The relationships of phytosterols and oxyphytosterols in plasma and aortic valve cusps in patients with severe aortic stenosis

Phytosterols such as campesterol and sitosterol are susceptible to oxidation by reactive oxygen species. We hypothesize that the plant sterols (PS) campesterol and sitosterol and their 7-oxygenated metabolites (POPs) correlate within and between human plasma and aortic valve cusps tissues. Plasma and tissue concentrations of PS and POPs were analyzed by gas chromatography–mass spectrometry-selected ion monitoring. Prior to analysis valve cusps tissue was mechanically separated from the calcified parts. PS and POP levels per dry cusps tissue weight were significantly higher compared with the concentrations in the calcified part. Against our hypothesis we found that despite the fact that there is a high correlation between plant sterols in and between plasma and valves cusps tissue, as well as a high correlation between plant sterols and oxyphytosterols and oxyphytosterols themselves within the valve cusps tissue, there was hardly any correlation in the amount of oxyphytosterols in plasma and between plasma and valves. Because plasma samples are easily accessible for large scale population based studies, we have to understand in more detail what the analysis of POPs implies in terms of CVD risk for the future.

Fast Determination of Pyrethroid Pesticides in Tobacco by GC-MS-SIM Coupled with Modified QuEChERS Sample Preparation Procedure

An analytical method was developed for the extraction and determination of pyrethroid pesticide residues in tobacco. The modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method was applied for preparing samples. In this study, methyl cyanide (MeCN)-saturated salt aqueous was used as the two-phase extraction solvent for the first time, and a vortex shaker was used for the simultaneous shaking and concentration of the analytes. The effects of experimental parameters on extraction and clean-up efficiency were investigated and optimized. The analytes were determined by gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM). The obtained recoveries of the analytes at three different fortification levels were 76.85-114.1% and relative standard deviations (RSDs) were lower than 15.7%. The limits of quantification (LOQs) were from 1.28 to 26.6 μg kg(-1). This method was also applied to the analysis of actual commercial tobacco products and the analytical results were satisfactory.

Determination of Listeria Monocytogenes in Agricultural Products by-High Resolution Pyrolysis Gas Chromatography-Mass Spectrometry

A method was developed for the qualitative determination of Listeria monocytogenes in the agricultural products by high resolution pyrolysis gas chromatography-mass spectrometry-selected ion monitoring(HPRGC/MS-MIS) technology.The method was accurate,highly sensitive and easy to operate.The operation conditions of HRPGC/MS system were as follows: pyrolysis conditions were as follows: starting temperature was 50 ℃,heating rate was 20 ℃/min,the temperature of the pyrolysis room was 230 ℃,and pyrolysis temperature was 650 ℃ for 10 s.Gas chromatography was accomplished with a carrier gas of helium at a flow rate of 0.9 mL/min.The GC column was a DB-WAXTER capillary column.The GC column temperature initially was kept at 45 ℃ for 4 min,then programmed to 100 ℃ at 6 ℃/min,200 ℃ at 10 ℃/min,250 ℃ at 12 ℃/min and held for 25 min.The total flow rate was spilt at ratio of 50 to 1.EI was used as ion source.The retention time of 19.056 min was selected for SIM,the ions of m/z were 54,98.L.monocytogens,two kinds of agricultural products with and without L.monocytogens samples were evaluated by this method according to the characteristics of the selected ion of L.monocytogens.An expected result was observed using the HRPGC/MS to detect L.monocytogens in different kinds of food,cucumber and beef.This method does not need the complex pre-treatment,the analysis time was comparatively short,and handing is easy for the operator.Retention time and mass spectra were used for qualitative analysis at the same time to eliminate the interference of different kinds of agricultural product impurities.The accurateness,good selectivity and reproducibility of the results demonstrate that HRPGC/MS is a useful method for rapid detection of L.monocytogens in agricultural products.

식품공전 분석법 미설정 농약의 잔류분석법 확립(I) -Chlorthal-dimethyl, Clomeprop, Diflufenican, Hexachlorobenzene, Picolinafen, Propyzamide-

수입 농식품에 대하여 국내에 등록되지 않아 식품공전 상의 분석법이 미확립된 chlorthal-dimethyl, clomeprop, diflufenican, hexachlorobenzene, picolinafen, propyzamide등 6종의 농약에 대해 GC-ECD로 다성분 동시분석법을 확립하였고, GC/MS로 확인하였다. 대상작물은 현미와 오렌지 2종을 선정하였고, 분석법은 식품의약품안전청에서 고시한 다종농약다성분 동시분석법을 적용하였다. 시료의 추출은 acetonitrile을 사용하였고 Florisil SPE 정제과정을 거쳤다. 분석법의 정량한계는 0.02~0.05 mg/kg 이었고, 직선성은 0.05~10.0 mg/kg 범위에서 <TEX>$R^2$</TEX> >0.999였다. 평균회수율은 정량한계 수준에서 74.4~110.3%, 정량한계 수준의 10배에서 77.8~118.4%였으며, 변이계수는 전체시료에서 8.8% 이하로 잔류농약 분석기준인 회수율 70~120%와 10% 이내의 변이계수 조건을 충족시켰다. 이와 같이 확립된 6종의 다성분 분석법은 수입농산물 분석에 적용이 가능할 것으로 판단된다. BACKGROUND: For the safety of imported agricultural products, the study was conducted to develop the analytical method of unregistered pesticides in domestic. The analytical method of 6 pesticides, chlorthal-dimethyl, clomeprop, diflufenican, hexachlorobenzene, picolinafen, and propyzamide, for a fast multi-residue analysis were established for two different type crops, orange and brown rice by GC-ECD and confirmed by mass spectrometry. METHODS AND RESULTS: The analytical method was evaluated to limit of quantification, linearity and recoveries. The crop samples were extracted with acetonitrile and performed cleanup by liquid-liquid partition and Florisil SPE to remove co-extracted matrix. The extracted samples were analyzed by GC-ECD with good sensitivity and selectivity of the method. The limits of quantification (LOQ) range of the method with S/N ratio of 10 was 0.02~0.05 mg/kg for orange and brown rice. The linearity for targeted pesticides were <TEX>$R^2$</TEX> >0.999 at the levels ranged from 0.05 to 10.0 mg/kg. The average recoveries ranged from 74.4% to 110.3% with the percentage of coefficient variation in the range 0.2~8.8% at two different spiking levels (0.02 mg/kg and 0.2 mg/kg, 0.05 mg/kg and 0.5 mg/kg) in brown rice. And the average recoveries ranged from 77.8% to 118.4% with the percentage of coefficient variation in the range 0.2~6.6% at two different spiking levels (0.02 mg/kg and 0.2 mg/kg, 0.05 mg/kg and 0.5 mg/kg) in orange. Final determination was by gas chromatography/mass spectrometry/selected ion monitoring (GC/MS/SIM) to identify the targeted pesticides. CONCLUSION: As a result, this developed analytical method can be used as an official method for imported agricultural products.

Determination of siloxanes in silicone products and potential migration to milk, formula and liquid simulants

A pressurised solvent extraction procedure coupled with a gas chromatography–mass spectrometry–selective ion monitoring (GC–MS–SIM) method was developed to determine three cyclic siloxanes, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6) and three linear siloxanes, octamethyltrisiloxane (L3), decamethyltetrasiloxane (L4), dodecamethylpentasiloxane (L5), in silicone products. Additionally, two different extraction methods were developed to measure these siloxanes migrating into milk, infant formula and liquid simulants (50 and 95% ethanol in water). The limits of quantification (LOQs) of the six siloxanes ranged from 6 ng/g (L3) to 15 ng/g (D6). Silicone nipples and silicone bakewares were extracted using pressurised solvent extraction (PSE) and analysed using the GC–MS–SIM method. No linear siloxanes were detected in the silicone nipple samples analysed. The three cyclic siloxanes (D4, D5 and D6) were detected in all silicone nipple samples with concentrations ranging from 0.5 to 269 µg/g. In the bakeware samples, except for L3, the other five siloxanes were detected with concentrations ranging from 0.2 µg/g (L4) to 7030 µg/g (D6). To investigate the potential migration of the six siloxanes from silicone nipples to milk and infant formula, a liquid extraction and dispersive clean-up procedure was developed for the two matrices. The procedure used a mix of hexane and ethyl acetate (1 : 1, v/v) as extraction solvent and C18 powder as the dispersive clean-up sorbent. For the liquid simulants, extraction of the siloxanes was achieved using hexane without any salting out or clean-up procedures. The recoveries of the six siloxanes from the milk, infant formula and simulants fortified at 50, 100, 200, 500 and 1000 µg/l ranged from 70 to 120% with a relative standard derivation (RSD) of less than 15% (n = 4). Migration tests were performed by exposing milk, infant formula and the liquid simulants to silicone baking sheets with known concentrations of the six siloxanes at 40°C. No siloxanes were detected in milk or infant formula after 6 h of direct contact with the silicone baking sheet plaques, indicating insignificant migration of the siloxanes to milk or infant formula. Migration tests in the two simulants lasted up to 72 h and the three cyclic siloxanes were detected in 50% ethanol after an 8-h exposure and after 2 h in 95% ethanol. The highest detected concentrations of D4, D5 and D6 were 42, 36 and 155 ng/ml, respectively, indicating very limited migration of D4, D5 or D6 into the two simulants.

Simultaneous Identification of the Enantiomers and Diastereomers of N,O-Di-trifluoroacetylated Ephedrine and Norephedrine in Blood Plasma using Chiral Capillary Gas Chromatography-Mass Spectrometry with Selected Ion Monitoring

A method for identifying the enantiomers of N,O-di-trifluoroacetylated ephedrine (EP) and norephedrine (NE) and the enantiomers of pseudoephedrine (PEP) and pseudonorephedrine (PNE) in plasma was developed using chiral capillary gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM). N,O-Di-trifluoroacethyl (TFA) derivatization was accomplished in a dried hydrochloride extract of plasma (minimum quantity of 0.2 mL). An SIM GC-MS method with a β-cyclodextrin chiral capillary column allowed the successful and simultaneous detection of each TFA-derivatized stereoisomer of EP, NE, PEP, PNE, and an internal standard (IS; S-(+)-ethylamphetamine). Each TFA-drivatized stereoisomer was identified using four mass fragment ions (m/z 140, 154, 168, and 230). The TFA-derivatized stereoisomers of EP, NE, PEP, PNE, and IS were separated completely and were detected with sufficient sensitivity. The assay allowed the stereoisomers to be determined in a linear range of 12.5-1250 ng/mL for the EP stereoisomers and a linear range of 5-1250 ng/mL for the PEP, NE, and PNE stereoisomers. The detection limits were 7.5 ng/mL for the EP stereoisomers and 2.5 ng/mL for the PEP, NE, and PNE stereoisomers. The intra- and interday precisions were less than 5.9% and 8.2%, respectively. This chiral capillary SIM GC-MS method was sufficiently effective in the analysis of plasma from users of over-the-counter cold medicines and was also fully applicable to the plasma analysis of guinea pigs following their treatment with racemic EP.

The mammalian metabolism of R-(-)-m-synephrine

The metabolism of R-(-)-m-synephrine (administered orally and by inhalation in man and intraperitoneally in rats) was studied quantitatively by a gas chromatography-mass spectrometry-selected ion monitoring (g.c.-m.s.-s.i.m.) method using deuterated internal standards. When m-synephrine hydrochloride was administered orally to humans in normal dosage regimens four main metabolites were excreted in urine: (i) unconjugated m-hydroxymandelic acid (MHMA, 30%), (ii) m-hydroxyphenylglycol (MHPG) sulphate (6%), (iii) m-synephrine sulphate (47%) and (iv) m-synephrine glucuronide (12%). The comparable figures after inhalation of the drug were 24, 6, 56 and 5%. Intraperitoneal injection of m-synephrine into rats gave: unconjugated MHMA (5%), MHPG sulphate (35%), unconjugated m-synephrine (7%) and conjugates of m-synephrine (9%:4% as the glucuronide and 5% as the sulphate).