Direct Inlet Research Articles

On-line monitoring of traces of aromatic-, phenolic- and chlorinated components in flue gases of industrial scale incinerators and cigarette smoke by direct-inlet laser ionization-mass spectrometry (REMPI-TOFMS)

The combination of laser induced resonance-enhanced multiphoton ionization (REMPI) and time-of-flight mass spectrometry (TOFMS) represents a highly selective as well as sensitive analytical technique, well suited for species selective real-time, on-line monitoring of trace-gases. Results presented are obtained with a newly designed, mobile REMPI-TOFMS instrument, optimized for field applications. The mobile REMPI-TOFMS device either is equipped with a compact excimer laser (KrF, λ = 248 nm) or a small Nd:YAG laser (forth harmonic frequency, λ = 266 nm). A special effusive molecular beam inlet system was used, which allows direct inlet of flue gases from e.g. waste incinerators without memory effects for compounds of a molecular weight of up to 260–280 amu. Detection sensitivities in the sub-ppb region are achieved under field measurement conditions. Applications concerning on-line monitoring of combustion byproducts and fuel components are presented. This includes on-line analysis of polycyclic aromatic hydrocarbons (PAH) in the flue gas of a 0.5 MW waste incineration pilot plant, headspace analysis of wood gasification products and crude oil composition (fuel analysis) as well as highly time resolved (single puff resolution) on-line analysis of cigarette smoke. The application of the on-line REMPI-TOFMS monitor for continuous analysis of dioxin indicators in the flue gas of e.g. hazardous waste incinerators is discussed.

On-Line Mass Spectrometry: A Faster Route to Process Monitoring and Control

A critical review of on-line mass spectrometry is presented, illustrating instrumentation, data treatment, and applications drawn from both control and research environments. Both direct and membrane inlets are included. The discussion of instrumentation focuses on commercially available options, although some research options that offer promise for future process applications are also mentioned briefly. Special considerations attendant upon the high-precision measurements needed for simultaneous analysis and continuous process control are emphasized. Applications illustrate a range of problems benefitting from rapid, simultaneous analysis of volatiles.

Numerical method and software package for prediction of pressure pulsation in centrifugal ventilators

A numerical method and software package was developed for designers and researchers in the field of vibration and noise problems in centrifugal ventilators. The numerical procedure is based on a representation of unsteady compressible liquid flow as a form of vortex (pseudo-sound) and acoustic mode superposition. It gives a possibility to determine absolute amplitudes of pressure pulsation in the ventilator casing induced by unsteady interaction between nonuniform flow outgoing from a centrifugal impeller volute tongue or diffuser vanes, so-called blade passing tones. Inupt data includes 2-D ventilator geometry and operation mode. Acoustic impedance boundary conditions can be defined with a circuit specification or by direct inlet and outlet specific complex impedance definition. It is possible to take into account local wall-specific complex impedance to study a coating effect on reduction of pressure pulsation. Output data represents: unsteady pressure map in the ventilator casing; amplitude distribution map for any selected harmonic; pressure versus time curves with accompanied spectrum information at any point selected by user; total vibration load vectors acting on the ventilator volute casing; and static pressure, velocity, and vorticity distribution in the centrifugal impeller. Validation of the software was completed on the centrifugal pump air model with more than 400 measuring points for two different radial gaps. The mismatch with experimental data is mostly 1.5–2.0 dB of unsteady pressure amplitude. Effects of radial clearance, number and form of impeller blades, exit and wall impedance are considered as well. The successful validation of the numerical method shows a good prospect in optimizing centrifugal ventilator geometry with improving vibration and noise characteristics at the draft stage and reducing refinement costs.

Furfuraldehyde resin pyrolysis in a closed system

The pyrolysis of two insoluble resins obtained by acid catalysis from furfuraldehyde and furfuraldehyde-dimethylketone was carried out in a closed system at 400 °C. The products of the pyrolysis were extracted under their vapor pressure. The compositions of the pyrolyzates were analyzed by mass spectrometry using a direct inlet probe technique under an electron impact of 70 eV. Thus, the main structural sequences of both resins were determined. Trifurylic sequences are the main component for the furfuraldehyde resin but the furfuralde-hydedimethyl ketone resin has two types of structural units: furfurylidene and furylmethylene.

Thermal degradation of plastisols. Effect of some additives on the evolution of gaseous products

Direct inlet mass spectrometry (DIMS) has been applied to some combinations based on a PVC resin (Vestolit 7021, HULS), one plasticizer (DEHP) and two stabilizers (Ba-Zn stearate and octadecyl-3-(3,5- tert-butyl-hydroxyphenyl)-propionate). Two different resin/plasticizer ratios and five different stabilizer concentrations have been studied. A comparative study of TIC curves and mass spectra between those different formulations has been developed. A wide peak at low temperatures corresponding to plasticizer vaporization has been observed, and the dehydrochlorination peak has been quantified in order to know the evolved products, mainly HCl. Benzene and alkyl-aromatics have also been observed and quantified for every formulation. In addition, some typical peaks corresponding to additives have been identified, and these have been used to know the stabilization behavior of every compound. When octadecyl-3-(3,5-tert-butyl-hydroxyphenyl)-propionate is used as stabilizer, it appears to be a better product to stabilize plastisols (dehydrochlorination peaks are lower). Hence we can conclude that this metal carboxylate (known for its environmental toxicity) could be replaced by new products that are better environmentally.

Preparation of Some Toxic Metabolites of Disulfoton, Phorate, and Terbufos, Their Separation by Thin-Layer Chromatography and Confirmation by Electron Impact Mass Spectrometry

Milligram quantities of sulfoxides, sulfones, and oxygen analogue (oxon) sulfones of the insecticides disulfoton, phorate, and terbufos were prepared by selective oxidation. Pure insecticides or acetone extracts of granular formulations served as reactants. Structures of 9 compounds were confirmed by comparing their electron impact mass spectra (EI-MS), obtained by the direct inlet system with published data. Thin-layer chromatography (TLC) on silica gel was used to screen oxidation products and to purify products. Products were detected by spraying plates with PdCl2 reagent and exposing to iodine vapors. An esterase inhibition technique gave low detection limits, which are promising for residue analysis.

Analytical characterization of the persistent residues after microbial degradation of mineral oils.

The residual fractions remaining after microbial degradation of diesel fuel, different deparaffinized raffinates and extracts from long-term contaminated soils were analyzed by liquid chromatography, gas chromatography, infrared spectrometry and mass spectrometry. The quantity of saturated hydrocarbons decreased after the microbial treatment, whereas the portion of polar compounds increased. The total content of aromatics changed only insignificantly. n-Paraffins < C26 were found to be no longer present in mineral oils degraded to exhaustion. Infrared spectrometry revealed oxygen compounds in the residues, mainly ketones, fatty acids and esters. Elementary analysis confirms the presence of nitrogen, oxygen and sulphur compounds in the degraded products. The gas chromatograms of high boiling oils, as well as of residues and extracts, consist mainly of a large base "envelope" (about 95% of the total area); thus gc/ms coupling reaches the limits of its applicability. However, mass spectrometry with direct inlet gives valuable information regarding hydrocarbon type analysis. The results revealed the preferable degradation of alkanes, 1-ring aliphatics and benzenes and an enrichment of condensed cycloaliphatics and aromatics. The latter compounds are known to be resistant to microbial attack.

Characterization of organic matter in an interlayer clay-organic complex from soil by pyrolysis methylation-mass spectrometry

The composition of organic matter in clay-organic complexes isolated from a New Zealand Spodosol has been investigated using the novel analytical combination of (a) labscale (500 mg) off-line pyrolysis, (b) direct inlet (5 mg) off-line methylation with tetramethylammonium hydroxide (TMAH) and pyrolysis-field ionization mass spectrometry (Py-FIMS), and (c) Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) with off-line and conventional on-line derivatisation with TMAH. In complex I the organic matter was associated with both external and interlayer surfaces of a swelling clay. Complex II was obtained by removing the external portion with H 2O 2 leaving the interlayer organic matter essentially intact. For both complexes, a high proportion of the carbon (64–86%) and nitrogen (76–91%) was volatilized during pyrolysis. Analysis of the pyrolysates showed mono- and dicarboxylic acids, alkanes, alkenes, n-alkylmonoesters, and N-containing compounds to be major constituents. Thermal methylation of the material, prior to (off-line) and during (on-line) pyrolysis gave rise to a wide range (between C 6 and C 35) of methyl esters of aliphatic and aromatic acids, methoxy derivatives of phenols and phenolic acids. In accord with previous 13C-nuclear magnetic resonance (NMR) spectroscopic measurements, the organic matter in both complexes was highly aliphatic in composition. Although there was little difference between complex I and complex II in the composition of the aliphatic constituents, complex II was greatly depleted in lignin-derived aromatics. In addition, the interlayer material in complex II had a relatively low thermal stability.

Mass spectrometry of crown ethers

The mass spectra of benzo-15-crown-5 and benzo-l8-crown-6 were investigated by mass spectrometry with different inlet systems, such as direct introduction, gas chromatography and liquid chromatography inlets. Different ionisation methods such as electron impact, chemical ionisation, electron capture or negative ion chemical ionisation were also studied. The results and the specific problems encountered for this group of substances are discussed based on the spectra obtained.

Determination of s-Triazine Metabolites: A Mass Spectrometric Investigation

The s-triazine herbicides have highly polar metabolites that often cannot be analyzed directly by gas chromatography−mass spectrometry (GC-MS). Chemical derivatization may be necessary to improve identification and quantitative analytical methods. The analysis of eight suspected metabolites of two s-triazine herbicides, atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and ametryn [2-(methylthio)-4-(ethylamino)-6-(isopropylamino)-s-triazine], was performed in the electron-impact mode by direct inlet system−mass spectrometry (DIS-MS) and by GC-MS, after sample derivatization. So far, previous derivatization procedures were either difficult or yielded a mixture of derivatives. By using N-methylbis[trifluoroacetamide] (MBTFA), we obtained only one derivative of each metabolite, and the method easily detected microbial degradation-derived metabolites. Moreover, we identified some frequently present ions that can be used in the analysis of complex samples. Keywords: Atrazine; ametryn; herbicides...

Rapid detection of high-molecular-mass dienes in beeswax

A rapid procedure for the detection of high-molecular-mass dienes in waxes, using a combination of chromatographic separations and direct inlet mass spectrometric determinations, allowed the determination of the presence of and the approximate relative concentrations on C 31-C 35 dienes in some beeswaxes.

A comparative study of the effects of fire retardants on the pyrolysis of cellulose and Pinus halepensis pine-needles

Differential scanning calorimetry (DSC) and direct inlet mass spectrometry (DI-MS) were used for studying the effects of fire retardants on the pyrolysis of cellulose and Pinus halepensis pine-needles. The compounds (NH 4) 2HPO 4 and (NH 4) 2SO 4 were used as fire retardants at various concentration levels. DSC showed that the addition of the fire retardants results in a shift to lower pyrolysis temperatures for cellulose and in an increase in the pyrolysis residues for both cellulose and pine-needles. DI-MS was used for monitoring the evolution rate of various pyrolysis products and for the identification of the various pyrolysis phases.

Studies on urine and tissues of rats, guineapigs and mice exposed to sulphur mustard using mass spectrometry

Urine and tissues (brain, liver, kidney, fat and triceps muscles) from rodents (rats, guinea pigs and albino mice) treated with sulphur mustard percutaneously were examined for the presence of sulphur mustard and/or metobolites using electron impact direct inlet and GC-mass spectrometry. Sulphur mustard and thiodiglycol sulphoxide were not detected in these samples even after application of massive doses. However, thiodiglycol was identified in urine only

Distribution of cyclized units present in isoprene oligomers synthesized by cationic oligomerization

AbstractThe structure of isoprene oligomers synthesized by cationic oligomerization in the presence of the BF3 · H2O complex as an initiator in a hexane solution at 40°C was investigated. These oligomer fractions obtained with the degree of polymerization (DP) in the range 5‐12, and the completely hydrogenated oligomers were examined using the direct inlet system‐mass spectrometry (DIS‐MS) technique. The distribution of the cyclic and linear structures in the oligomers was obtained by integrating the selected ion current of the different hydrogenated products. The results obtained were interpreted by means of a statistical simulation based on a step‐by‐step competition between cyclization and monomer addition reaction. The value of the probability of cyclization was found to be very high for low‐molecular‐weight oligomers and to decrease with increasing molecular weight of the oligomers.

Mass Spectrometric Studies of Flavonoids

Abstract Flavonoids are substances of vegetal origin, some of which are used as pharmaceutical compounds. We investigated the mass spectrometric behaviour of five flavonoids: silybinin, isosilybinin, silicristin, silidianin and taxifolin. Direct inlet system (DIS), LC-MS and fast atom bombardment (FAB) analyses were done on the parent compounds and other DIS and GC-MS analyses were run on derivatized flavonoids, to clarify their mass spectrometric behaviour. Deuterated derivatives were also used to confirm the major fragmentation pathways.

GC‐MS analysis of n‐phosphonomethylglycine (glyphosate) samples through derivatization with a perfluoroanhydride and trifluoroethanol: Identification of by‐products

Glyphosate (N‐phosphonomethyl‐glycine) herbicide samples were analysed qualitatively using gas chromatography‐mass spectrometry (GC‐MS) through derivatization with pentafluoropropionic anhydride plus trifluoroethanol. Besides the expected glyphosate perfluoroacetylated derivative, other compounds were observed and identified using this technique and MS alone with the direct inlet system (DIS). Three processes are probably involved in the formation of these products: 1) incomplete derivatization; 2) glyphosate degradation during the reaction; 3) traces of chemical impurities in the pesticide sample.

Resolution of complex mixtures of flavonoid aglycones by analysis of gas chromatographic-mass spectrometric data

Forty-nine flavones, flavonols, flavanones and chalcones were analysed without derivatization by GC and GC-MS using an OV-1 capillary column. Retention times are affected by the number, position and type of the substituents. The mass spectra show the same typical fragmentation pattern as obtained by the direct inlet method. The effectiveness of the proposed method is demonstrated by the GC and GC-MS analysis of a plant extract in which 21 different flavonoid aglycones could he identified.

Formation of 3,N4-ethenocytidine, 1,N6-ethenoadenosine, and 1,N2-ethenoguanosine in reactions of mucochloric acid with nucleosides.

Mucochloric acid, a genotoxic hydroxyfuranone found in chlorinated drinking water, was reacted with cytidine, adenosine, guanosine, and uridine. HPLC analyses with UV detection at 290 nm showed that one major product peak was formed in the reactions of cytidine, adenosine, and guanosine. The products formed in reactions carried out at 90 degrees C for 24 or 45 h were isolated by HPLC and characterized by 1H and 13C NMR spectroscopy, direct inlet chemical ionization mass spectrometry, and UV absorbance spectroscopy. The structures of the products were assigned to 3,N4-ethenocytidine, 1,N6-ethenoadenosine, and 1,N2-ethenoguanosine. In reactions performed at 37 degrees C and pH 7.0 the same compounds were detected after a reaction time of 7 days. No observable reaction took place between mucochloric acid and uridine.

Characterization of triacylglycerols in the seeds ofAquilegia vulgaris by chromatographic and mass spectrometric methods.

A combination of analytical techniques is generally necessary to properly characterize complex lipid materials. Chromatographic separation in conjunction with spectroscopic characterization was utilized for the analysis of the triacylglycerols in the seeds ofAquilegia vulgaris. Reversed-phase high-performance liquid chromatography (HPLC), micropacked argentation supercritical fluid chromatography (SFC), and combinations of the two techniques were used. The fatty acid profile was determined by gas chromatography/mass spectrometry of the picolinyl esters and by gas chromatography/flame-ionization detection of the methyl esters. The major components were also identified by direct inlet mass spectrometry. The excellent selectivity of packed fused silica argentation SFC for the separation of triacylglycerols was demonstrated.

Photodegradation of the herbicide goal

Photodegradation products of the herbicide Goal active ingredient were obtained with a xenon lamp and analyzed using direct inlet mass spectrometry, MS/MS and GC/MS. A number of products were identified and their generation pathways were established to be mainly Ar—O bond cleavage, dechlorination and photocyclisation. The latter process gives chlorinated and unchlorinated dibenzofurans some of which may be toxic.