Rapid determination of methyl salicylate, a plant-signaling compound, in tomato leaves by direct sample introduction and thermal desorption followed by GC-MS

Many plants infested by herbivores or viruses can rapidly produce and accumulate a plant-signaling compound, methyl salicylate (MeSA), in their leaves to activate disease resistance. In the present work, a simple, rapid, and sensitive method was developed for the determination of MeSA in tomato leaves by direct sample introduction and thermal desorption followed by GC-MS. Results show that the proposed method has a low detection limit (0.08 ng mg(-1)) and good precision (RSD = 8.9%). The present method was applied to the investigation of tomato plant defense response to tobacco mosaic virus (TMV) by rapid analysis of volatile compounds in plant leaves. It was found that tomato plants can produce large amounts of MeSA as a defense response to TMV. This indicates that MeSA may be a plant-signaling compound in tomato plant defense response to TMV.     

Investigation of Tomato Plant Defence Response to Tobacco Mosaic Virus by Determination of Methyl Salicylate with SPME-Capillary GC-MS

Headspace SPME was applied to investigation of tomato plant defence response to tobacco mosaic virus (TMV) by determination of compounds emitted from tomato plants at the extraction conditions of 25 °C and 15 min. It was found that TMV-inoculated tomato plant released large amount of methyl salicylate (MeSA) as response to TMV and MeSA concentration changed dramatically with time after inoculation. Gaseous MeSA as a signaling compound could induce in surrounding tomato plants to produce salicylic acid (SA) and synthesize and release MeSA. These results show that MeSA might be an airborne plant-signalling molecule in tomato plant response to TMV. The present method provided low detection limit of 2.0 ng L^–1 and needed little sample preparation time (15 min), so the method makes it easy to find the critical times of tomato plant response to TMV by fast determination of MeSA released from tomato plant.     

Simultaneous capillary GC-MS determination of triazines and amides in water

Summary A simultaneous capillary Gas Chromatographic-Mass Spectrometric (GC-MS) method is described for the determination of thirteen pesticides belonging to the triazine and amide families in water. The sample is extracted in liquid-liquid mode (dichloromethane) and then the determination of the residues is carried out by capillary gas chromatography with mass spectrometric detection in the Selected-Ion Monitoring mode (SIM). The average recoveries of spiked compounds are in the 78.4–135.4% range between the relative low level (0.100 g L^–1) and the relative high level (10.0 g L^–1). The limits of detection (LOD) are in the 0.009–0.128 g L^–1 range.     

Microdetermination of ascorbic acid and tryptophan by colorimetry

Summary Ascorbic acid reacts with 2,3,5-triphenyltetrazolium chloride in alkaline medium giving pink color having 5g/ml as visual limit of identification. This color reaction has been utilized for the colorinietric determination of ascorbic acid from pharmaceutical preparations in minute quantities. The maximum tolerable amount of other vitamins, sugars and organic compounds during determination of ascorbic acid is reported.Tryptophan reacts with hexamine to give yellow color having 5g/ml as limit of identification. The color reaction provides the basis of a new method for colorimetric determination of tryptophan. The maximum tolerable amount of various amino acids and vitamins is reported. The mechanism of the color reaction is not clear.

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Zusammenfassung Ascorbinsäure reagiert mit 2,3,5-Triphenyrtetrazoliumchlorid in alkalischem Milieu unter Rosafärbung. Erfassungsgrenze: 5g/ml. Diese Farbreaktion wurde zur kolorimetrischen Bestimmung kleiner Mengen Ascorbinsäure in pharmazeutischen Präparaten verwendet. Die tolerierbare Höchstmenge an anderen Vitaminen, Zuckern und organischen Verbindungen wurde angegeben. Tryptophan reagiert mit Hexamin unter Gelbfärbung. Erfassungsgrenze: 5g/ml. Die Farbreaktion dient als neue Methode zur kolorimetrischen Tryptophanbestimmung. Die nicht störenden Höchstmengen an anderen Aminosäuren und Vitaminen sind angegeben. Der Reaktionsmechanismus ist nicht geklärt.

     

Preparation of μ-(η5:η5-Fulvalene)-di-μ-hydrido-bis(η5-cyclopentadienyltitanium) by the reduction of Cp2TiCl2 with LiAlH4 in aromatic solvents

Summary -(⁵:⁵-Fulvalene)-di--hydrido-bis(⁵-cyclopentadienyltitanium) (1) can be prepared by the reduction of Cp₂TiCl₂ with LiAlH₄ in methylbenzenes and in tetralin at their boiling temperatures in yields greater than 90%. The reduction proceedsvia the bis(⁵-cyclopentadienyl)titanium(III) chloride dimer which is further transformed into the unstable [Cp₂TiH] species. Thermal decomposition of the latter accompanied by hydrogen evolution gives rise to (1). -(⁵:⁵-Fulvalene)--hydrido--chloro-bis(⁵-cyclopentadienyltitanium), the first fulvalene containing compound observed in the system is formed by hydrido-chloro exchange of (1) with (Cp₂TiCl)₂ and aluminium chlorohydrides.     

Chromatographic determination of D-amino acids as native constituents of vegetables and fruits

Summary Free D-amino acids (D-AA) were detected as native constituents in juices of vegetables (cultivars of cabbage, tomato, carrot, garlic) and fruits (organes, clementine, grapefruit, lemon, apples, pear, grapes) using gas chromatography (GC) or high-performance liquid chromatography (LC). For investigation by GC, AA enantiomers were converted into theirN(O)-pentafluoropropionyl 2-propyl esters and resolved on a Chirasil-L-Val capillary column. For determination by LC, precolumn derivatization of AA enantiomers usingo-phthaldialdehyde together with the chiral thiolsN-isobutyryl-L-cysteine orN-isobutyryl-D-cysteine and fluorescence detection of the diastereomeric isoindole derivatives, resolvable on an octadecylsilyl stationary phase, were used. D-Ala (0.6–3.8%) was detected in all freshly pressed plant juices usually in the highest relative amounts. Other D-AA detected were D-Asx (0.1–1.9%), D-Glx (0–1.3%), D-Ser (0–1.7%), D-Arg (0.4–1.2%, in grapes, orange, grapefruit, and clementine) and D-Leu and D-Val (1% in cabbage). Absolute amounts of native D-AA were totally 28–57 mol L^–1 in fruit juices, 14.5 mol L^–1 in a tomato juice and 8.5 mol L^–1 in a carrot juice.Presented in part as lecture at 3rd International Congress on Amino Acids, Peptides and Analogues, August 23–27, 1993, Vienna; and as posters at 31st Scientific Meeting of German Society of Nutrition, Giessen, March 17th and 18th, 1994 [19]; and at Analytica Conference, April 19–22, 1994, Munich [20].     

Determination of fluorine in standard rocks by photon activation analysis

A highly sensitive determination of fluorine in standard rocks by photon activation using the¹⁹F(,n)¹⁸F reaction combined with pyrohydrolysis for the separation of¹⁸F has been reported. The irradiation energy was operated at 20 MeV to avoid the interference from Na, because Na is one of the major element in rocks and¹⁸F is also produced from Na via²³Na(,n)¹⁸F reaction above its threshold energy, 20.9 MeV. After irradiation, fluorine was extracted by pyrohydrolysis and separated as LaF₃ precipitate. It was ascertained that the average recovery of fluorine in standard rocks was about 90% and the precipitate was of high radiochemical purity. This method was applied to the analysis of ten GSJ rock reference samples and two USGS standard rocks issued by the Geological Survey of Japan and the United States Geological Survey, respectively. The detection limit of this method was 0.02 g/g, and the results obtained by this method were in good agreement with the recommended values. This method was easily applied to the determination of a few ppm level of fluorine in rock samples, such as ultrabasic rock and feldspar.     

Spectrophotometric determination of phosphorus as phosphate in organic compounds and materials of biological origin using a flow-injection manifold with a mixing chamber

Summary A flow-injection manifold with mixing chamber has been developed for the determination of phosphate by reaction with molybdate and crystal violet. The insoluble blue dye salt is kept in colloidal solution with poly(vinyl alcohol) and measured at 560 nm. The injection rate is 100 h^–1. The detection limit is 0.01 g PO ₄ ^3– /ml based on 250 l injection volumes. The system has been applied to the determination of phosphate in serum samples and after appropriate mineralisation to organic compounds and to plant materials.     

Analysis of the Aerial Parts of Verbena officinalis L. by Micellar Electrokinetic Capillary Chromatography

A micellar electrokinetic capillary chromatography (MECC) method was developed for the qualitative and quantitative determination of five marker compounds (iridoid glycosides, flavonoids and phenylethanoids) in Verbena officinalis. Optimum separation was achieved using a 50 mM sodium borate solution (pH 9.3), containing 50 mM sodium dodecylsulfate (SDS) as surfactant, at an applied voltage of 25 kV and a temperature of 30 °C, respectively. Because of their different absorption maxima, the compounds were detected either at 205 or 235 nm. Calibration data confirmed linearity of the detector response within the concentration range injected (R² from 0.997 to 0.999), and revealed detection limits ranging from 5.0 g mL^–1 (verbascoside) to 13.6 g mL^–1 (hastatoside). The five markers were readily assignable in several samples of Verbena.     

Effect of Cu(II) on the electrochemically initiated reaction of thiols with<Emphasis Type="Italic"> N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diethyl-<Emphasis Type="Italic">p</Emphasis>-phenylenediamine: methodology for the indirect voltammetric determination of Cu(II)

The effect of Cu(II) on the determination of homocysteine via its electrochemically initiated reaction with N,N-diethyl-p-phenylenediamine is examined. The presence of copper inhibited the detection process for homocysteine owing to a complexation reaction occurring. This provided an indirect route for the sensitive and selective determination of Cu(II), which produced a linear response over the range from 2.5 to 500 M and a limit of detection of 2.5 M. The detection pathway was examined in the presence of metallic and inorganic ions, with negligible interference observed.     

A Large Volume Injection Procedure for GC-MS Determination of PAHs and PCBs

A simple on-column injection system for large volume of liquid samples for the GC-MS determination of traces of PAHs and PCBs has been investigated. A deactivated fused silica capillary 20 m × 0.53 mm I.D. and 2 meters of an HP5 column (0.53 mm,1 m film thickness) were used as retention gaps. Injection volumes of 80 L for PAHs and 90 L for PCBs, allow determination of 5–50 ng L^–1 PAHs and 11–44 ng L^–1 PCBs in hexane solution with an RSD of < 10%. The method has been used for the determination of PCBs and PAHs in soil sample.     

Use of a stopped-flow technique for investigation and determination of thiourea and its <Emphasis Type="Italic">N</Emphasis>-methyl derivatives as inducers of the iodine–azide reaction

A stopped-flow technique has been used to investigate the behaviour of 2-thiourea, 1-methyl-2-thiourea, 1,3-dimethyl-2-thiourea, and 1,1,3,3-tetramethyl-2-thiourea in the induced iodine–azide reaction. This technique enables the progress of the reaction to be followed by monitoring the decrease in the absorbance of the iodine–starch complex at 595 nm. The effect of the concentration of the reagents on the rate of the reaction was investigated and a kinetic method for determination of the compounds is proposed. 2-Thiourea, 1-methyl-2-thiourea, and 1,3-dimethyl-2-thiourea can be determined in the range 3–75 mol L^–1 and 1,1,3,3-tetramethyl-2-thiourea in the range 2–200 mol L^–1.     

20-Hydroxyecdysone from Stemmacantha uniflora Subsp. satzyperovii

The dynamics of 20-hydroxyecdysone content in vegetative and generative organs of Stemmacantha uniflora subsp. satzyperovii (Soskov) Dittrich, which is distributed over Primorskii Krai, were investigated. A high content of 20-hydroxyecdysone during the plant vegetative period is characteristic of growing organs. The amount is maximal for young leaves during development of racemes (7.8 g/mg) and for ripe achenes (11.15 g/mg).     

A comparison of methods for the determination of the dating-nuclides210Pb and226Ra

Lead-210 is often used to date recent (100 y) environmental samples. Three different methods for its determination are compared:²¹⁰Pb -counting with a low level proportional counter,²¹⁰Pb -spectroscopy and²¹⁰Po -spectroscopy. Agreement within analytical errors was found for the three methods in two sediment cores from Lake Zurich, Switzerland and in IAEA SD-A-1 deep sea reference material. For²¹⁰Po -spectroscopy, the detection and determination limit is an order of magnitude lower than these for the other methods. Methods for the determination of²²⁶Ra are also discussed. Measurements on low level proportional counters are difficult to interpret and not suitable for routine work. A better way to measure²²⁶Ra is -spectroscopy of colloidal Ba(Ra)SO₄.     

Headspace Solid-phase Microextraction–Gas Chromatographic–Mass Spectrometric Analysis of the Essential Oils of Two Traditional Chinese Medicines, Angelica pubescens and Angelica sinensis

Angelica pubescens and Angelica sinensis belong to the Umbelliferae family and both are used as traditional Chinese medicines. In the present study, headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS) was used for the analysis of the volatile constituents present in their roots. Eighty-seven compounds in Angelica pubescens and thirty-six compounds in Angelica sinensis were identified by GC-MS. Their relative contents were calculated by the peak area ratio. HS-SPME was compared to steam distillation (SD) by analyzing the volatile constituents of Angelica sinensis root. A good agreement between results obtained with both techniques was found. As a conclusion, HS-SPME is a powerful tool for determining the volatile constituents present in the TCMs.     

Determination of pyrimethanil and kresoxim-methyl in soils by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A method using headspace solid-phase microextraction (HS-SPME) then gas chromatography–mass spectrometry with selected ion monitoring (GC–MS, SIM) has been developed for determination of trace amounts of the fungicides pyrimethanil and kresoxim-methyl in soil and humic materials. Both fungicides were extracted on to a fused-silica fibre coated with 85 m polyacrylate (PA). Response-surface methodology was used to optimise the experimental conditions. For soil samples the linear dynamic range of application was 0.004–1.000 g g^–1 for pyrimethanil and 0.013–1.000 g g^–1 for kresoxim-methyl. The detection limits were 0.001 g g^–1 and 0.004 g g^–1 for pyrimethanil and kresoxim-methyl, respectively. HP-SPME–GC–MS analysis was highly reproducible—relative standard deviations (RSD) were between 6.7 and 12.2%. The method was validated by analysis of spiked matrix samples and used to investigate the presence of pyrimethanil and kresoxim-methyl above the detection limits in soil and humic materials.     

Flow injection-spectrophotometric determination of cresol compounds in water by reaction withp-aminophenol

A spectrophotometric method has been developed for the simultaneous determination ofo-cresol andm-cresol in water by reaction withp-aminophenol (PAP). Three different methodologies have been assayed; (i) batch analysis, after reaction in an alkaline medium in the presence of dissolved molecular oxygen as oxidizing agent, (ii) a stopped-flow procedure, carried out in the presence of KIO₄ and (iii) a flow injection method based on the same approach. The batch procedure requires 22 min for the full development of colour witho-cresol and 12 min form-cresol. In the stopped-flow mode, using KIO₄ and a reaction time of 12 min, better sensitivity can be obtained for both compounds and limits of detection of 10 g 1^–1 foro-cresol and 30 g 1^–1 form-cresol were found. The flow injection method has a lower sensitivity but permits more than 80 injections per hour. Based on the different maximum absorbance wavelengths obtained for the reaction products of PAP witho-cresol (614 nm) andm-cresol (632 nm), both compounds can be simultaneously determined in water samples and recoveries of 90 to 115% were found in spiked water samples of different types.     

Determination of benzidine in urine using capillary gas chromatography and negative-ion chemical ionisation mass spectrometry

Summary A highly sensitive and specific gas chromatographic-mass spectrometric (GC-MS) assay for the determination of benzidine in urine is reported. It is based on the solvent extraction of the hydrolysed benzidine conjugates, together with the deuterium-labelled benzidine-d₈ added as an internal standard, and a two-phase derivatisation procedure using pentafluoropropionic anhydride (PFPA) in the presence of pyridine as the phase-transfer catalyst. The reaction is complete within 5 min at room temperature. The pentafluoropropyl derivatives are quantified through capillary column GC-MS using selected ion monitoring (SIM) in the negative-ion chemical ionisation mode (NICI). The lower limit of detection for benzidine was 0.5 g/l and the calibration plot showed linearity between 2 g/l and 200 g/l. The recovery of the analyte added to pooled urine was above 82%. Analysis of 20 urine samples from un-exposed persons and 20 urine specimens of workers employed in a polyurethane-making plant using this procedure showed no substances likely to manifest false positive results in the range of interest.     

High-performance liquid chromatographic determination of saponins fromHedera helix L. using a light-scattering detector

Summary A high-performance liquid chromatographic method for the simultaneous determination of bidesmosidic and monodesmosidic saponins from the leaves ofHedera helix L. using a light-scattering detector is proposed.A satisfactory separation of the bidesmosidic and monodesmosidic saponins is obtained in 25 min on a reversed phase RP18 using an acetonitrile-water mixture as eluant. Hederasaponin C and -hederin were found to be the major saponins of the leaves. The linearity of response, repeatability and reproducibility of the proposed method were tested. The detection limits for hederasaponin C and -hederin were 0,1 and 0.05 g/20 l respectively.     

Spectrophotometric determination of nitrite in environmental waters using column preconcentration on biphenyl

Column preconcentration methods have been established for the spectrophotometric determination of trace nitrite with sulfanilic acid (SA) orp-aminoacetophenone (AAP) as the diazotizable aromatic amine andN, N-dimethylaniline (DMA) or 1-aminonaphthalene (AN) as the coupling agent, using differention-pairs co-precipitated with biphenyl. Nitrite ion reacts with SA in the pH range 2.0–3.0 and AAP in the pH range 1.7–3.0 in HCl medium to form water-soluble colourless diazonium cations. These cations are subsequently coupled with DMA in the pH range 3.7–6.1 for the SA-DMA system and AN in the pH range 1.7–2.3 for the AAP-AN system to be retained on microcrystalline biphenyl packed in a column. The solid mass is dissolved out from the column with 5 ml of DMF and the absorbance is measured by a spectrophotometer at 420 nm for the SA-DMA system and at 517 nm for the AAP-AN system. The calibration was linear over the concentration ranges 0.3–6.0 g of nitrite in 5 ml of DMF solution (i.e., 0.02–0.40 g/ml in the sample solution) for the SA-DMA system and 0.5–7.0 g of nitrite in 5 ml of DMF solution (i.e., 0.03–0.47 g/ml in the sample solution) for the AAP-AN system. The molar absorptivity and Sandell's sensitivity were respectively 2.63 × 10⁴lmol^–1cm^–1 and 1.75 × 10^–3 g cm^–2 for SA-DMA and 3.28 × 10⁴lmol^–1 cm^–1 and 1.40 × 10^–3 g cm^–2 for AAP-AN. The concentration factors were 4 and 16 for SA-DMA and AAP-AN, respectively. The detection limits were 0.0138 and 0.0175 g/ml NO₂ ^– for SA-DMA and AAP-AN, respectively. Seven replicate determinations of a solution containing 3.5 g of nitrite gave mean absorbances of 0.410 and 0.500 with relative standard deviations of 0.51 and 0.55% for SA-DMA and AAP-AN, respectively. Interference from various foreign ions has been studied and the methods have been applied to the determination of nitrite in environmental samples.