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1.
In support of the efforts to combat smuggling, as well as illegal sale and distribution of cigarettes, an analytical approach for the characterization of tobacco has been proposed and evaluated. It involves aqueous extraction of the filler tobaccos followed by direct analysis of the extracts by electrospray ionization-ion trap mass spectrometry (ESI-ITMS) in the negative mode. Typically, the deprotonated ions, [M - H](-), of organic acids (malic, citric, caffeic, quinic acid) and polyphenols (chlorogenic acid, rutin, scopoletin) were detected. MS/MS spectra of the ion at m/z 191, which is the [M - H](-) of quinic acid, citric acid, and scopoletin, and a fragment ion of chlorogenic acid were acquired. Significant differences in the MS and MS/MS spectra were observed between counterfeit samples and the corresponding authentic brand name cigarettes. Analysis of 25 commercial cigarettes showed that straight Virginia blends were readily distinguished from the blended products containing different tobacco types (Virginia, burley, and Oriental). The former exhibited consistently higher relative abundances of m/z 353 (chlorogenic acid) to m/z 133 (malic acid) in the MS spectra (0.9-1.2 vs 0.4-0.6) and higher intensity ratios of m/z 176 (scopoletin) to m/z 173 (0.4-0.8 vs 0.1-0.3) and of m/z 127 (quinic acid) to m/z 173 (0.7-1.0 vs 0.3-0.5) in the MS/MS spectra. Evidence is presented to demonstrate that the spectral differences were related not only to the tobacco type (Virginia, burley and Oriental) but also to the tobacco part (stem, lamina) used in the manufacture of the cigarettes.  相似文献   

2.
A method for the analysis of T-2 toxin in milk is presented. Ethyl acetate extracts of milk samples which had been spiked with T-2 toxin were purified by thin layer chromatography and derivatized with N,O-bis(trimethylsilyl)acetamide to produce the T-2 toxin trimethylsilyl ether (T-2 toxin-TMS). N,O-bis(trimethylsilyl-d9)acetamide was used to make T-2 toxin d9-trimethylsilyl ether (T-2 toxin-d9 TMS) which was added to the derivatized milk extract as an internal standard. Samples were analyzed by combined gas-liquid chromatography/mass spectrometry using either electron impact ionization or chemical ionization mass spectrometry. In electron impact ionization analyses, simultaneous monitoring of the T-2 toxin-TMS fragment ion at m/z 436 and the T-2 toxin-d9TMS fragment ion at m/z 445 gave a T-2 toxin-TMS detectability estimated at 6 microgram/kg. In chemical ionization analyses, the T-2 toxin-TMS fragment ion at m/z 377 and the T-2 toxin-d9TMS fragment ion at m/z 386 were simultaneously monitored to give a T-2 toxin-TMS detectability estimated at 3 microgram/kg. Average recovery was 85% at 200 microgram/kg and 65% at 20 microgram/kg.  相似文献   

3.
采用固相萃取（SPE）为样品前处理方法,建立了超高效液相色谱-串联四极杆质谱联用（UPLC-MS/MS）检测土壤中咪唑乙烟酸的残留分析方法。土壤样品经0.1 mol.L-1的氯化铵与氨水缓冲液（pH=10）超声提取、C18SPE柱净化后,应用超高效液相色谱串联四级杆质谱仪多离子反应监测（MRM）定量检测,分别以碎片离子m/z 290〉176和m/z 290〉245进行外标法定量。结果表明,在0.01~0.5mg.kg-1添加水平范围内咪唑乙烟酸的平均添加回收率在83.47%~101.70%之间;相对标准偏差在4.15%~5.28%之间;咪唑乙烟酸的定量检出限（LOQ）为0.075μg.kg-1。该方法灵敏度高,操作简单,定量准确,可用于土壤中咪唑乙烟酸的残留分析。  相似文献   

4.
Reactions involved in blue-green discoloration in a mixture of onion (Allium cepa L.) and garlic (Allium sativum L.) were investigated. Vivid-blue color was successfully reproduced by using a defined model reaction system comprising only trans-(+)-S-(1-propenyl)-L-cysteine sulfoxide (1-PeCSO) from onion, S-allyl-L-cysteine sulfoxide (2-PeCSO) from garlic, purified alliinase (EC 4.4.1.4), and glycine (or some other amino acids). Four reaction steps identified and factors affecting the blue color formation were in good agreement with those suggested by earlier investigators. When crude onion alliinase was used in place of garlic alliinase, less pigment was formed. This result was explained by a difference in the amount of thiosulfinates, colorless intermediates termed color developers, yielded from 1-PeCSO by these enzymes.  相似文献   

5.
为分析罗氏海盘车性腺的单甘酯组成,本研究对单甘酯的衍生方法和色谱条件进行优化,并对单甘酯硅烷化衍生物的断裂规律和质谱特征进行分析,同时对罗氏海盘车性腺的单甘酯组成进行分析测定。结果表明,三甲基硅烷化法对单甘酯具有理想的衍生效果,且通过弱极性毛细管柱HP-5MS(30 m×0.25 mm×0.25 μm)对单甘酯硅烷化衍生物取得了理想的色谱分离效果。根据断裂规律和质谱特征,1-单甘酯硅烷化衍生物的特征离子为m/z 73、m/z 205、[M-103]+(基峰离子)和[M-15]+;2-单甘酯硅烷化衍生物的特征离子为m/z 73(基峰离子)、m/z 129、m/z 218、[M+H-162]+和[M-15]+。单甘酯硅烷化衍生物的色谱保留时间具有一定的规律性,其中2-单甘酯衍生物先于1-单甘酯衍生物出峰。同时,从罗氏海盘车中共鉴定出8种单甘酯,以1-单软脂酸甘油酯(1-C16:0-MG)和1-单硬脂酸甘油酯(1-C18:0-MG)等1-单甘酯为主,而2-单甘酯含量较低。本研究结果为单甘酯的衍生、色谱分析和质谱鉴定提供了一定的理论参考。  相似文献   

6.
Abstract

Metolachlor (2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐meth‐oxy‐1‐methylethyl)acetamide) is being considered for control of eastern black nightshade (Solarium ptycanthum Dun.) in cabbage (Brassica oleracea L. var. capitata), broccoli (B. oleracea L. var. Botrytis) and tomato (Lycopersicon esculentum Mill.). We have developed a rapid, sensitive method to determine metolachlor residues in these commodities to ensure its absence in the edible tissue. The crop material was extracted with methanol, the extract partitioned with hexane, then passed through a silica cartridge and analysed for metolachlor by GC/MSD in selected ion mode at m/z 161. Recovery of metolachlor from fortified plant material was greater than 84%. The method detection limit was calculated to be 0.6 ppb for tomato, 1.1 ppb for cabbage, and 4.2 ppb for broccoli. Metolachlor residues were below the detection limit in all commodities harvested from treatments which received 2 or 3 kg metolachlor/ha.  相似文献   

7.
Procyanidins are a class of polyphenols in the plant kingdom. Lotus ( Nelumbo nucifera Gaertn.) seedpods, the inedible part of lotus and a byproduct during the production of lotus seeds, were found to be a new source rich in procyanidins. Detailed information about oligomeric procyanidins in lotus seedpods remains unknown. In this study, lotus seedpods were extracted using 60% aqueous methanol and characterized with phloroglucinolysis and liquid chromatography (mass spectrometry with an electrospray ionization source). The results indicate that the oligomeric and polymeric fraction had a mean degree of polymerization of 3.2 and 15.4, respectively, and consisted of (+)-catechin (m/z 289), gallocatechin or epigallocatechin (m/z 305), quercetin glycoside (m/z 463), quercetin glucuronide (m/z 477), procyanidin dimers (m/z 577.1), proanthocyanidin dimer gallate (m/z 593.3), prodelphinidin dimers (m/z 609.1), procyanidin trimers (m/z 865.1), etc. Quercetin glucuronide was further purified using flash chromatography and identified as quercetin-3-O-β-glucuronide by determining its exact mass using ion-trap time-of-flight mass spectrometry and 1H and 13C nuclear magnetic resonance, 1H-detected heteronuclear single-quantum coherence, and 1H-detected heteronuclear multiple-bond correlation analyses.  相似文献   

8.
Quantitation of ochratoxin A in South African wines   总被引：3，自引：0，他引：3  
The natural occurrence of the carcinogenic mycotoxin ochratoxin A (OTA) in wines sold in local retail outlets in South Africa and Italy was investigated by HPLC analysis with fluorescence detection following cleanup by immunoaffinity column. All 24 local South African wines tested (15 white and 9 red) were found to contain detectable levels (>0.01 microg/L) of OTA, with a mean of 0.16 microg/L in the white wines and a mean of 0.24 microg/L in the red wines. Results were subsequently confirmed by LC-MS analysis using positive ion electrospray ionization with collision-induced dissociation of the protonated molecular ion [M + H](+) at m/z 404 and selected reaction monitoring of the resultant product ions [M + H - H(2)O - CO](+) at m/z 358 and [M + H - H(2)O](+) at m/z 386. Comparison with the fluorescence method gave a significant correlation (r = 0.87; p < 0.01). Although OTA contamination was present in all of the South African samples analyzed, levels were well below the suggested European Union limit of 0.5 microg/kg. The highest level found in a locally purchased wine was 0.39 microg/L in a blend of local and imported Spanish red wine. Of the eight Italian wines analyzed, only two red wines were contaminated above the suggested maximum level.  相似文献   

9.
Selected primitive and modern wheat species were evaluated on the basis of their carotenoid composition and effects of the genotype and environment on lutein using spectrometry and liquid chromatography. Carotenoids in the wheat extracts were identified and confirmed on the basis of their UV/vis and mass spectra compared with those of authentic standards. The protonated molecule (M + 1)+ at m/z 569 was the predominant ion for zeaxanthin compared to the fragment ion at m/z 551 for lutein. A similar carotenoid profile was obtained for the wheat species investigated, but significant differences were observed in the concentration of carotenoids. Einkorn (Triticum monococcum) exhibited the highest level of all-trans-lutein, averaging 7.41 microg/g with small amounts of all-trans-zeaxanthin, cis-lutein isomers, and beta-carotene. Durum, Kamut, and Khorasan (Triticum turgidum) had intermediate levels of lutein (5.41-5.77 microg/g), while common bread or pastry wheat (Triticum aestivum) had the lowest content (2.01-2.11 microg/g). Lutein in einkorn appeared to be influenced significantly by environmental growing conditions.  相似文献   

10.
The butter flavorant diacetyl (2,3-butanedione) is implicated in causing obliterative bronchiolitis in microwave popcorn plant workers. Because diacetyl modifies arginine residues, an immunological basis for its toxicity is under investigation. Reaction products of diacetyl with N-α-acetylarginine (AcArg) were determined as a model for hapten formation, with characterization by mass spectrometry, NMR, and HPLC with UV detection and radiodetection. Four products were identified by LC-MS, each with a positive ion of m/z 303 (diacetyl + AcArg); one pair displayed an additional ion at m/z 217 (AcArg), the other pair at m/z 285 (- H(2)O). Their (1)H-(13)C NMR correlation spectra were consistent with the addition of one or two of the guanidine nitrogens to form aminols. Open-chain pairs interconverted at pH 2, as did the cyclized, but all four interconverted at neutral pH. This is the first structural characterization of the covalent adducts between diacetyl and an arginine moiety.  相似文献   

11.
A new sensitive and selective method has been developed for the quantification of the total coenzyme Q9 (CoQ9) and coenzyme Q10 (CoQ10) concentration in vegetable oil samples. The coenzyme Q fraction is isolated by solid-phase extraction (SPE) on amino phase eluting with a mixture of heptane:ethyl ether. The organic solvent is evaporated under nitrogen, and the residue is dissolved in a mixture of acetonitrile:tetrahydrofuran and finally is analyzed by reverse-phase high-performance liquid chromatography with a mass detector. The sensitivity of the method is based on the high efficient formation of the radical anions [M (-.)] of CoQ9 and CoQ10 by negative atmospheric pressure ionization. Interferences are minimized by using mass detection of the [M (-.)] ions ( m/ z = 797.5 for CoQ9 and m/ z = 862.5 for CoQ10) in selective reaction monitoring mode ( m/ z = 797.5 --> m/ z = 779.5 and m/ z = 862.5 --> m/ z = 847.5) using a triple-quadrupole mass spectrometer. The method was successfully applied to sunflower, soybean, and rapeseed oils, with a limit of quantification of 0.025 mg/kg for both compounds.  相似文献   

12.
Anthocyanins were isolated from male bracts of 10 wild species of bananas (Musa spp. and Ensete spp.) distributed in Thailand. Six major anthocyanin pigments were identified by high performance liquid chromatography (HPLC), mass spectrometry (MS), and tandem mass spectrometry (MS/MS). They are delphinidin-3-rutinoside (m/z 611.2), cyanidin-3-rutinoside (m/z 595.8), petunidin-3-rutinoside (m/z 624.9), pelargonidin-3-rutinoside (m/z 579.4), peonidin-3-rutinoside (m/z 608.7), and malvidin-3-rutinoside (m/z 638.8). On the basis of the types of pigment present, the wild bananas can be divided into 5 groups. The first group comprises M. itinerans, Musa sp. one, Musa sp. two, and M. acuminata accessions, which contain almost or all anthocyanin pigments except for pelargonidin-3-rutinoside, including both nonmethylated and methylated anthocyanins. The second group, M. acuminata subsp. truncata, contains only malvidin-3-rutinoside while the third group, M. coccinea, contains cyanidin-3-rutinoside and pelargonidin-3-rutinoside. The forth group, M. acuminata yellow bract and E. glaucum do not appear to contain any anthocyanin pigment. The fifth group consists of M. balbisiana, M. velutina, M. laterita, and E. superbum which contain only nonmethylated anthocyanin, delphinidin-3-rutinoside, and cyanidin-3-rutinoside. Total anthocyanin content in the analyzed bracts ranged from 0-119.70 mg/100 g bract fresh weight. The differences in the type of anthocyanin and variation in the amounts present indicate that wild bananas show biochemical diversity, which may be useful for identifying specific groups of bananas or for clarifying the evolution of flavonoid metabolism in each banana group.  相似文献   

13.
A procedure has been developed and validated for measuring the concentration of pentobarbital residues in dry, extruded animal feed in the range of 3-200 ng/g (ppb) with an estimated limit of quantitation of 2 ppb. The method was developed for surveillance purposes: to measure the concentration of euthanizing agent which might be present in feeds incorporating rendered products which themselves might include some fraction of euthanized animals. A previously published qualitative procedure was modified by adding isotopically labelled pentobarbital as an internal standard. Dry feed was ground and extracted with methanol. The extract was loaded on a mixed-mode (C-18, anion exchange) solid-phase extraction cartridge designed for barbiturate residues. Pentobarbital was eluted and derivatized for gas chromatography/mass spectrometry in positive ion chemical ionization mode. Quantitation was based on the ratio of dimethyl-pentobarbital MH+ (m/z 255) vs dimethyl-pentobarbital-d(5) (m/z 260) in standards and extracts. Accuracy ranged from 112% at 3 ppb to 96% at 200 ppb, with relative standard deviations ranging from 4% at 3 ppb to 2% at 200 ppb.  相似文献   

14.
This paper describes atmospheric pressure ionization (API) LC-MS-MS determination of urushiols, 3-n-alkenyl- and -alkyl-substituted catechols responsible for poison oak dermatitis. Urushiol was isolated from Western poison oak according to the method of Elsohly et al. (1) (J. Nat. Prod. 1982, 45, 532-538)-the purified preparation contained C(17)- and C(15)-substituted urushiols with zero, one, two, and three double bonds as determined from GC-MS analysis of trimethylsilyl derivatives. Urushiol mixtures were separated on a C(18) reversed phase HPLC column with a methanol-water gradient with urushiols eluting in 100% methanol. Atmospheric pressure chemical ionization (APCI) produced primarily [M - H](-) and MH(+) molecule ions. Electrospray ionization (ESI) yielded [M - H](-) and adduct ions including [M + Cl](-). Daughter ions of [M - H](-) included quinoid radical anions ([M - H - H(2)](-) and m/z 122(-)) and a benzofuran phenate (m/z 135(-)). A suite of hydrocarbon fragments were produced by collision-induced dissociation of MH(+) directly or via an intermediate [MH - H(2)O](+) daughter ion. Six urushiol congeners, one not previously reported in poison oak, were determined by negative ion API-LC-MS-MS with detection limits of approximately 8 pg/microL (ESI) and approximately 800 pg/microL (APCI). API-LC-MS-MS was used to determine urushiol in surface wipes, air samples, and plant materials.  相似文献   

15.
The dynamic changes in thiosulfinate profiles were studied in reaction systems containing a crude onion alliinase, S-alk(en)yl-L-cysteine sulfoxide substrates (1) and preformed thiosulfinates (4). Regioisomeric excesses of one of two possible heterologous 4 species (RS(O)SR', where R does not equal R') could be manipulated under conditions where alliinase, 1, and 4 levels were varied. Regioisomeric excesses could be explained by a thiosulfinate (4)/alkanesulfenic acid (2) trapping mechanism, with the greatest control over product profile governed by the rate of 2 generation in the system. The series of reactions existing in this dynamic reaction system was kinetically modeled with reasonable fits to the experimental data. The application of the 4/2 trapping strategy to manipulate thiosulfinate and related organosulfur product profiles in diluted onion homogenates was demonstrated using exogenous MeS(O)SMe (4a), PrS(O)SPr (4c), and AllS(O)SAll (4d) as the preformed thiosulfinate.  相似文献   

16.
A cDNA clone of 1081 bp encoding a second putative superoxide dismutase (SOD) from diatom Thallassiosira weissflogii was cloned by the polymerase chain reaction technique. The cDNA encodes a protein of 286 amino acid residues. Alignment of the truncated SOD sequence containing 217 amino acid residues with Mn-SODs from Vibrio mimicus and Escherichia coli, as well as two Fe-SODs from E. coli and Photobacterium leiognathi, this SOD showed greater homology to Mn-SOD. The residues required to coordinate the manganese ion were conserved in all reported Mn-SOD. The recombinant SOD has a half life of deactivation of 14.7 min at 65 degrees C. Its thermal inactivation rate constant Kd was 3.21 x 10(-2) min(-1). The enzyme was stable in a broad pH range from 4 to 12. The presence of imidazole (up to 0.8 M) and sodium dodecylsulfate (up to 4%) had little effect on the enzyme's activity. The atomic absorption spectrometric assay showed the presence of 0.3 atom of iron/manganese (2:1) in each SOD subunit. Reconstituted activity suggested that diatom SOD was cambialistic Fe/Mn-SOD.  相似文献   

17.
A rapid LC-MS/MS method was developed for the quantitative determination of grayanotoxins I, II, and III in rumen contents, feces, and urine. The grayanotoxins were extracted from solid samples with methanol. The methanol extract was diluted with water and cleaned up using a reversed phase solid phase extraction column. HPLC separation was performed by reversed phase HPLC using a gradient of water and methanol containing 1% acetic acid. Determination was by positive ion electrospray ionization and ion trap tandem mass spectrometry. Grayanotoxin I quantitation was based on fragmentation of the sodium adduct ion at m/z 435 to a product ion at m/z 375. Grayanotoxins II and III were quantitated on the basis of fragmentation of the ion at m/z 335 to the product ion at m/z 299. The method detection limits were 0.2 microg/g in rumen contents and feces and 0.05 microg/g in urine. Fortifications at the detection limits and 10 times the detection limits of bovine rumen contents, caprine feces, and ovine urine were recovered in the range 80-114%. The diagnostic utility of the method was tested by analyzing samples submitted to the veterinary toxicology laboratory.  相似文献   

18.
Abstract. Crop growth on strongly weathered soils is often limited by soil compaction in addition to aluminium toxicity and/or calcium deficiency. This study examines the effects of subsoiling, lime and gypsum on penetrometer resistance, acidity, aluminium and calcium levels and cotton ( Gossypium hirsutum L.) root growth on soils transitional between Cecil and Appling series (clayey, kaolinitic, thermic Typic Hapludults) in the Piedmont region of Georgia, USA. The main plots were subsoiled to depths of 0.35 or 0.80 m or untreated. Dolomitic limestone (0 or 4.03 t per hectare on subplots) and phosphogypsum (0 or 10 t per hectare on sub-subplots) were incorporated into the surface soil (0.15 m). Deep subsoiling (0.80 m depth) decreased penetrometer resistance at 0.3–0.5 m depth and increased yield in two of three years, but there was no response to shallow subsoiling (0.35 m depth). Lime increased yield when surface soil water pH prior to amendment was less than a Cate-Nelson critical value of 4.6. Gypsum moved downward much more rapidly than lime, increasing soil solution calcium ion activity to a depth of 0.8 m within 5 months of application. There were differences in clay content between replicate plots and calcium movement was faster where the clay content was less. Yield responses to gypsum in 1986 were attributed to increased root growth below 0.2 m resulting from the increased calcium ion activity. Yield response to gypsum in limed sub-subplots was significant only in 1986.  相似文献   

19.
Various Allium hybrids, obtained by the crossbreeding of Allium cepa (onion) as the mother plant and six taxonomically distant wild species obtained by embryo rescue, were investigated with special respect to their individual profiles of cysteine sulfoxides as well as enzymically and nonenzymically formed aroma substances. Alliinase (EC 4.4.1.4) catalyzes the conversion of odorless (+)-S-alk(en)yl-L-cysteine sulfoxides into volatile thiosulfinates. These thiosulfinates were converted to a variety of sulfides by steam distillation. SPME-gas chromatography (GC) and high-performance liquid chromatography (HPLC) used for the analysis of aroma components and their precursors permitted a high sample throughput, so that numerous gene bank accessions and Allium breeding materials were analyzed within a comparatively short time. Cysteine sulfoxides as well as alliinase activity were found in all investigated samples at different levels, but (+)-S-methyl-L-cysteine sulfoxide (methiin) was the most abundant sulfoxide present. (+)-S-(trans-1-Propenyl)-L-cysteine sulfoxide (isoalliin) is typical for onion and was found in all investigated hybrids. The pattern of the other cysteine sulfoxides depended strongly on the parent plants used. The profile of aroma components corresponded with the related pattern of aroma precursors (cysteine sulfoxides). Successful hybridization was proven by randomly amplified polymorphic DNA analysis. Together with these established marker techniques, HPLC and SPME-GC analysis provide support to breeding projects designed to improve the health and aroma properties of Allium hybrids.  相似文献   

20.
We have investigated the capability of direct infusion electrospray ionization mass spectrometry in the negative ion mode, ESI(-)-MS, to differentiate representative samples of artisan cacha?a, a Brazilian sugar cane distillate of large production, aged in four different types of wood casks: amburana (Amburana cearensis), jequitibA (Cariniana estrellensis), balm (Myroxylon peruiferum), and oak (Quercus rubra). The ESI(-)-MS were found to be very characteristic, showing sets of diagnostic ions for each of the four types of samples: amburana (m/z 271, 313, 377), jequitibA (m/z 143, 171, 255), balm (m/z 137, 269, 283, 297), and oak (m/z 197, 301, 307). Furthermore, principal component (PCA) and hierarchical cluster analysis (HCA), applied to the ESI(-)-MS data, divided these samples into four definite categories. The influence of the aging time on the ESI(-)-MS fingerprints of the cacha?a samples stored in oak casks was also established. An inversion in the relative intensity of the diagnostic ions of m/z 307 and 301 is detected in the ESI(-)-MS as the aging time increased from 1 to 2 years. The chemical structures of the major cacha?a components were proposed on the basis of the following: (a) the comparison of the ESI(-)-MS/MS of the diagnostic anions with those of the authentic anions or (b) the interpretation of the fragmentation patterns of the previously unknown diagnostic anions. Hence, direct infusion ESI(-)-MS allows not only a rapid, simple, and accurate way to distinguish among cacha?a samples stored in different wood casks but also monitoring changes in their chemical composition according to the aging time.  相似文献   

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