Determination of 10 carcinogenic polycyclic aromatic hydrocarbons in mainstream cigarette smoke

Polycyclic aromatic hydrocarbons (PAHs) are one class of chemical compounds that (1) are present at low to trace levels in unburned cigarette filler, and (2) are predominantly generated during combustion. According to a recent report of the International Agency for Research on Cancer, 10 carcinogenic PAHs together with 53 other known carcinogens are present in cigarette smoke. Accurate quantification of these chemicals helps assess public health risk to both smokers and nonsmokers exposed to second-hand smoke. We have developed and validated a specific and sensitive method for measuring these 10 carcinogenic PAHs in the particulate phase of mainstream tobacco smoke. Cigarette smoke particulate, produced using standard machine smoking protocols, was collected on glass fiber Cambridge filter pads. The particulate matter was solvent extracted, purified by solid-phase extraction, and analyzed by liquid chromatography/atmospheric pressure photoionization tandem mass spectrometry using isotopically labeled analogues as internal standards. Our method's limits of detection ranged from 11 to 166 pg and achieved sufficient reproducibility and accuracy to provide useful information on a range of cigarettes having dramatically different machine-smoked tar and nicotine deliveries. The identity of each PAH analyte was established from chromatographic retention time, analyte-specific fragmentation patterns, and relative peak area ratios of the product/precursor ion pairs. This new method provides higher sensitivity, specificity, and throughput than did earlier methods. We found relatively consistent PAH levels among a selection of domestic full-flavor cigarettes. The PAH levels in smoke from highly ventilated light and ultralight cigarettes were low when smoked using ISO (International Organization for Standardization) conditions. However, if highly ventilated cigarettes were smoked under more intense conditions (e.g., larger or more frequent puffs, vents blocked), their PAH levels equaled or exceeded their full-flavor counterparts under ISO conditions.     

The form of nicotine in tobacco. Thermal transfer of nicotine and nicotine acid salts to nicotine in the gas phase

Thermal transfer to nicotine in the gas phase from neat nicotine, from various nicotine carboxylic acid salts, and from endogenous nicotine in Burley, Bright, and Oriental tobacco samples has been examined by thermogravimetric/differential thermal analysis/mass spectroscopy and evolved gas analysis. Under the conditions used in these studies, the peak transfer temperatures of these substances to nicotine in the gas phase are nicotine and nicotine acetate, both ca. 110-125 degrees C; nicotine malates, ca. 110-210 degrees C for nicotine to malic acid ratios of 1:0.56 and 1:1 and ca. 160-210 degrees C for a nicotine to malic acid ratio of 1:2; (S)-nicotine bis[(2R,3R)-hydrogen tartrate] dihydrate, ca. 195-210 degrees C; and tobacco samples, a range of ca. 160-220 degrees C. These results suggest that nicotine is mostly protonated in tobacco leaf. In all cases, the temperature of the transfer of nicotine to the gas phase was found to be many hundreds of degrees below the temperatures observed around the coal of a burning cigarette (smolder, ca. 500-775 degrees C; dynamic smoking, 600 to over 950 degrees C). Within the narrow zone of a puffing cigarette that encompasses an intermediate temperature range (125-250 degrees C), kinetic data suggest that these temperatures are not sufficient to volatilize significant amounts of nonprotonated nicotine, assuming any exists at all, during the short puff duration (2 s). It is concluded that nonprotonated nicotine and protonated nicotine (salts of nicotine with natural tobacco carboxylic acids) will transfer nicotine to smoke with comparable yields and efficiencies during the smoking process.     

Cigarette smoke composition. Part 1. Limitations of FTC method when applied to cigarettes that heat instead of burn tobacco

The design of a new cigarette that heats rather than burns tobacco calls for modifications to the Federal Trade Commission (FTC) method for analytical smoking. These changes include eliminating sample conditioning at 75 degrees F and 60% RH, exercising greater care in lighting cigarettes, and smoking cigarettes to self-extinguishment rather than to a predetermined butt length as a measure of complete consumption. By several gross analytical measures, smoke condensate from the new cigarette differs substantially from that of tobacco-burning cigarettes. This is inferred from the lack of coloration of smoke condensate collected on Cambridge filters. Elemental analysis demonstrates reduced carbon and nitrogen content concurrent with increased hydrogen. Thermogravimetric analysis shows almost quantitative weight loss at Tmax = 220 degrees C. Ultraviolet (UV) spectrophotometric analysis shows greatly reduced levels of tobacco-derived smoke components and qualitative differences in chemical entities being measured. By design, the heat required for smoke formation is supplied by a carbon heat source embedded in the cigarette tip. Tobacco contained in the cigarette is not burned and is exposed to temperature less than 300 degrees C. Thus, it is apparent (1) that smoke from the new cigarette contains little or no "tar" as tar is classically defined, and (2) that the FTC method even as modified to account for cigarette design differences is appropriate only for determination of nicotine and carbon monoxide yielded from this cigarette.     

Cigarette smoke composition. Part 2. Method for determining major components in smoke of cigarettes that heat instead of burn tobacco

A method is described for determining major constituents in the smoke of a cigarette that heats, but does not burn, tobacco. Dual, simultaneous separations are performed in a single gas chromatographic oven to determine water, glycerol, nicotine, and propylene glycol in a rapid and cost-effective manner. A materials balance of new cigarette smoke total particulate matter was attempted from both Cambridge filter and electrostatic precipitation smoke collection data. Serious deficiencies were found when Cambridge filter smoke collection was applied for this purpose. Electrostatic precipitation smoke collection eliminated these problems. The data obtained by electrostatic precipitation smoke collection indicate that water, glycerol, nicotine, and propylene glycol make up about 94% of new cigarette smoke total particulate matter.     

Solid-phase microextraction-based approach to determine free-base nicotine in trapped mainstream cigarette smoke total particulate matter

Characterizing nicotine delivery from tobacco products is important in the understanding of their addictive potential. Most previous studies report total nicotine and have not differentiated between nicotine in its protonated or free-base form. Rather than simply determining total nicotine, the method described in this paper determines the amount of free-base nicotine associated with trapped mainstream smoke particulate matter generated using a standardized smoking machine protocol. This method quantitatively determines volatile free-base nicotine associated with the particulate phase portion of mainstream cigarette smoke using solid-phase microextraction combined with gas chromatography-mass spectrometry. The headspace above total particulate matter from mainstream cigarette smoke trapped on a Cambridge filter pad (CFP) was analyzed for free-base nicotine in 26 cigarette brands. The selected cigarette brands were chosen to cover a wide range of tar and nicotine deliveries as measured under Federal Trade Commission machine smoking conditions. In the CFP's headspace the free-base nicotine levels ranged from 0.01 to 0.08 mg/cigarette. The measured ranges of free-base nicotine were remarkably similar over the different tar and nicotine delivery categories of full-flavored, light, and ultralight cigarette brands.     

Quantitation of flavor-related alkenylbenzenes in tobacco smoke particulate by selected ion monitoring gas chromatography-mass spectrometry

Little is known about the possible health effects associated with inhaling alkenylbenzenes through cigarette smoking, even though these flavor-related compounds have known toxic effects in animals. We developed a rapid and sensitive solid-phase extraction (SPE) method to quantify seven alkenylbenzenes and piperonal in mainstream cigarette smoke particulate. The smoke particulate fraction of a single cigarette was collected on Cambridge filter pads, solvent extracted, concentrated, purified with SPE, and analyzed by selected ion monitoring gas chromatography-mass spectrometry. We positively identified and quantified five alkenylbenzenes compounds (eugenol, isoeugenol, methyleugenol myristicin, and elemicin) and piperonal in the smoke particulate from eight U.S. brands with mean levels (measured in triplicate) ranging from 6.6 to 4210 ng per cigarette. Additionally, complete blocking of nearly invisible ventilation holes in the cigarette filter increased 2- to 7-fold the percent transfer of alkenylbenzenes from tobacco to the particulate fraction of mainstream smoke.     

Characterization of cultivation effects on soil organic matter

Humus properties in various Ap horizons from field plots, that have been cultivated in long-term experiments under different management conditions, were investigated by pyrolysis-field ionization mass spectrometry (Py-FIMS) and ¹³C-NMR spectroscopy. The results of Py-FIMS were evaluated by correlation and principal component analysis from reproducible data sets of bulk soil samples and extracted humic substances, and allowed a distinct discrimination on the basis of humus quality and composition. The chemical subunits suitable for discrimination are the major plant constituents carbohydrates, lignin, and proteinaceous materials as well as their humification products. The contribution of these compound classes to soil organic matter decreased with the intensity of management. CPMAS and solution ¹³C NMR spectra of soils and humic substances demonstrated that with more intense management, both the intensities of the phenolic region (140–160 ppm) and the aromatic region (110–140 ppm) decreased. The combination of both independent methods MS and NMR, together with microbiological and biochemical data, yields the general result that intensive soil management leads to a less active humus.     

Aromatic constituents of humic acids released by na-amalgam reductive cleavage,koh fusion and zinc dust fusion

Eight humic acids showing different degree of humification were treated with HCI (1:1). The hydrolyzed humic acids were subjected to reductive cleavage with Na-amalgam, KOH fusion and zinc dust fusion. The yields of degradation products were determined by colorimetry gas chromatography.

The perimental results Were summarized as follows:

l. The amounts of ether-soluble substances obtained by reductive cleavage with Naamlagan ranged from 21.6% for Kuragari (A type) to 7.8% for Kisokoma B₂ (Rp type). The yields of phenolic substances expressed in terms of vanillic acid content ranged from 3.0% for Kuragari (A type) to 1.8% for Kisokoma B₂ (Rp type). Resorcinol. p.hydroxybenzoic acid, vanillic acid, protocatechuic acid and syringic acid were detected in the gas chromatograms of the ethe-soluble substances and their total yield comprised less than 0.6% of the Kisokoma F (Rp type).

2. The KOH fusion of humic acid yielded a larger amount of degradation products as compared to reductive cleavage. The amount of ether-soluble substances ranged from 42.7% for Kisokoma F (Rp type) to 12.6% for Sochiken 1 (A type). The yields of phenolic substances, expressed in terms of amount of protocatechuic acid, ranged from 10.6% for Kisokoma F (Rp type) to 4.6% for Inogashira (A type). Exept for syringic acid, the same compounds released after ramged from 2.1% for Sochiken 2 (B type) to 0.4% for Sochiken 1 (A type).

3. The amounts of benzene-soluble substances and hydrocarbons obtained from Goshikigahara (P type) by zinc dust fusion were 20.9% and 5.2%, respectively. The yields of the hydrocarbons tended to increase in the order; P type > Rp type ≥ B type. Perylene and 2-methylanthracene were detected in the gas chromatograms of the hydrocarbons fractions and, in the case of Goshikigahara (P type), their yields were 0.031% and 0.010%, respectively.     

Rapid differentiation of three Chamaecyparis species (Cupressaceae) grown in Taiwan using solid-phase microextraction-gas chromatography/mass spectrometry, cluster analysis, and principal component analysis

Three Chamaecyparis species (C. formosensis, C. obtusa, and C. obtusa var. formosana) are difficult to distinguish by the naked eye. Therefore, from the chemotaxonomic point of view, it would be valuable to find a simple and rapid method to differentiate these three Chamaecyparis species. In this study, the chemical compositions of biogenic volatile organic compounds (BVOCs) from mature leaves were analyzed using solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS). Then cluster analysis (CA) and principal component analysis (PCA) were conducted for the BVOC constituents to reveal the differences among these three species. Results from SPME-GC/MS showed that the compositions of BVOCs from the three species were distinctly different. Moreover, these species were clearly differentiated according to the results of CA and PCA. In conclusion, the findings of this study suggest that SPME-GC/MS coupled with CA and PCA is a feasible and rapid technique to differentiate Chamaecyparis species with similar morphological characteristics.     

Polycyclic aromatic hydrocarbons in liquid smoke flavorings obtained from different types of wood. Effect of storage in polyethylene flasks on their concentrations

Smoke flavorings are widely used as an alternative to the traditional smoking techniques. Smoke generation conditions can determine the level of polycyclic aromatic hydrocarbons (PAHs) in the smoke and, consequently, in these preparations. In this paper, the influence of the wood source on the formation of PAHs is studied. For this purpose, five liquid smoke flavorings, obtained from different types of wood, were used. Sample aliquots, including deuterated internal standards, were subjected to an alkaline treatment, extracted by liquid-liquid partition and cleaned up by means of silica tubes, followed by gas chromatography-mass spectrometry analysis. The results reveal that the flavoring obtained from poplar wood presents the highest number and concentrations of both total and carcinogenic PAHs, even though the levels of these latter are very low. It has also been observed that the storage of smoke flavorings in polyethylene flasks reduces the concentration of some PAHs.     

Improved automated extraction and separation procedure for soil lipid analyses

Analysis of soil lipids may contribute to an improved understanding of atmosphere to soil carbon fluxes, soil organic matter source differentiation and pollutant accumulation. Soil lipids, mostly originating from plants and microorganisms, have traditionally been analysed by non‐automated extraction and separation methods, which produce several lipid fractions, operationally defined by polarity. Here we present a combination of fast, automated and reproducible techniques, adopted from organic geochemical studies, for preparative separation of individual soil lipid fractions with increasing polarity. These techniques involve commercially available instruments, including accelerated solvent extraction and a two‐step automated medium‐pressure liquid chromatography procedure. The method yields eight lipid fractions consisting of five fractions fully amenable to gas chromatography/mass spectrometry (GC/MS) (aliphatic hydrocarbons, aromatic hydrocarbons, ketones, alcohols, carboxylic acids), and three fractions of highly polar or high molecular weight compounds (bases, very long‐chain wax esters (C40₊), high polarity compounds) that were not measurable with GC/MS under standard conditions. We tested the method on five agricultural soils. Results show that (i) mass recoveries for the individual fractions are reproducible, (ii) within individual fractions compound distribution patterns are reproducible, as demonstrated for alkanes and carboxylic acids, and (iii) individual fractions represent distinct and clean compound classes, free of interfering substances detectable by GC/MS. Thus, automated separation can be a fast, effective and reproducible procedure for fractionation of complex mixtures of soil lipids into clean compound classes, directly suitable for a variety of molecular (e.g. GC/MS) and isotopic characterizations (e.g. gas chromatography coupled with isotope ratio monitoring mass spectrometry or accelerator mass spectrometry).     

Compound‐specific stable‐isotope (δ13C) analysis in soil science

This review provides current state of the art of compound‐specific stable‐isotope‐ratio mass spectrometry (δ¹³C) and gives an overview on innovative applications in soil science. After a short introduction on the background of stable C isotopes and their ecological significance, different techniques for compound‐specific stable‐isotope analysis are compared. Analogous to the δ¹³C analysis in bulk samples, by means of elemental analyzer–isotope‐ratio mass spectrometry, physical fractions such as particle‐size fractions, soil microbial biomass, and water‐soluble organic C can be analyzed. The main focus of this review is, however, to discuss the isotope composition of chemical fractions (so‐called molecular markers) indicating plant‐ (pentoses, long‐chain n‐alkanes, lignin phenols) and microbial‐derived residues (phospholipid fatty acids, hexoses, amino sugars, and short‐chain n‐alkanes) as well as other interesting soil constituents such as “black carbon” and polycyclic aromatic hydrocarbons. For this purpose, innovative techniques such as pyrolysis–gas chromatography–combustion–isotope‐ratio mass spectrometry, gas chromatography–combustion–isotope‐ratio mass spectrometry, or liquid chromatography–combustion–isotope‐ratio mass spectrometry were compared. These techniques can be used in general for two purposes, (1) to quantify sequestration and turnover of specific organic compounds in the environment and (2) to trace the origin of organic substances. Turnover times of physical (sand < silt < clay) and chemical fractions (lignin < phospholipid fatty acids < amino sugars ≈ sugars) are generally shorter compared to bulk soil and increase in the order given in brackets. Tracing the origin of organic compounds such as polycyclic aromatic hydrocarbons is difficult when more than two sources are involved and isotope difference of different sources is small. Therefore, this application is preferentially used when natural (e.g., C3‐to‐C4 plant conversion) or artificial (positive or negative) ¹³C labeling is used.     

Recovery of Starch and Protein from Wet-Milled Corn Fiber

Physical and chemical methods were used to recover starch and protein from wet-milled corn fiber. A single milling of the fiber produced an 18% yield of mill starch. By separating the mill starch with a starch table, 68% of this material was recovered as starch with a protein contamination of 0.66%. Milling increased fine fiber from 4.5% in the starting material to 11.5% after a single grind. Successive additional milling passes modestly increased the mill starch and fine fiber yields with a corresponding decrease in the coarse fiber yield. Pretreatment with combinations of lactic and sulfurous acids had only a small effect on the distribution and composition of the recovered fractions.     

Rapid isolation and identification of active antioxidant ingredients from Gongju using HPLC-DAD-ESI-MS(n) and postcolumn derivatization

Flos Chrysanthemi (Gongju, GJ) is used to prepare a herbal tea that is commonly consumed as a health beverage in Asia and is believed to contain abundant beneficial antioxidants. To rapidly identify the chemical constituents and to obtain the profile related to antioxidant activity, an online analytical method combining high-performance liquid chromatography-diode-array detector-electrospray ionization-ion-trap time-of-flight mass spectrometry (HPLC-DAD-ESI-IT-TOF-MS(n)) and postcolumn derivatization (PCD) has been applied for a precise and thorough identification of the chemical constituents. Meanwhile, the antioxidant profile has also been characterized by directly measuring the scavenging activity of each compound for the free radical produced by DPPH. As a result, 13 compounds have been identified in GJ, 7 of which account for its antioxidant activity. The established LC-MS(n)-PCD system has proved to offer a useful strategy for correlating the chemical profile with the bioactivities of the components without their isolation and purification, and may be used for multicomponent analysis of active substances in other foods and herbs.     

Chemical composition of Juniperus communis L. fruits supercritical CO2 extracts: dependence on pressure and extraction time

Ground fruits of the common juniper (Juniperus communis L.), with a particle size range from 0.250-0.400 mm, forming a bed of around 20.00 +/- 0.05 g, were extracted with supercritical CO(2) at pressures of 80, 90, and 100 bars and at a temperature of 40 degrees C. The total amount of extractable substances or global yield (mass of extract/mass of raw material) for the supercritical fluid extraction process varied from 0.65 to 4.00% (wt). At each investigated pressure, supercritical CO(2) extract fractions collected in successive time intervals over the course of the extraction were analyzed by capillary gas chromatography, using flame ionization (GC-FID) and mass spectrometric detection (GC-MS). More than 200 constituents were detected in the extracts, and the contents of 50 compounds were reported in the work. Dependence of the percentage yields of monoterpene, sesquiterpene, oxygenated monoterpene, and oxygenated sesquiterpene hydrocarbon groups on the extraction time was investigated, and conditions that favored the yielding of each terpene groups were emphasized. At all pressures, monoterpene hydrocarbons were almost completely extracted from the berries in the first 0.6 h. It was possible to extract oxygenated monoterpenes at 100 bar in 0.5 h and at 90 bar in 1.2 h. Contrary to that, during an extraction period of 4 h at 80 bar, it was possible to extract only 75% of the maximum yielded value of oxygenated monoterpene at 100 bar. Intensive extraction of sesquiterpenes could be by no means avoided at any pressure, but at the beginning of the process (the first 0.5 h) at 80 bar, they were extracted about 8 and 3 times slower than at 100 and 90 bar, respectively. Oxygenated sesquiterpenes were yielded at fast, constant extraction rates at 100 and 90 bar in 1.2 and 3 h, respectively. This initial fast extraction period was consequently followed by much slower extraction of oxygenated sesquiterpenes.     

Extractable components of the aerial parts of Salvia lavandulifolia and composition of the liquid smoke flavoring obtained from them.

The fraction extractable with dichloromethane of the aerial parts of sage (Salvia lavandulifolia) and the liquid smoke obtained from this plant are studied by means of gas chromatography/mass spectrometry and gas chromatography. The extract of the aerial parts of the sage plant contains not only terpene, sesquiterpene hydrocarbons, and their oxygenated derivatives, which are interesting compounds both for their organoleptic properties and for their antioxidant activity, but also a large group of phenolic compounds with abietatriene or related structure, the mass spectra of which are given, many of them having antioxidant, antiviral, and antibacterial properties. The liquid sage smoke obtained is slightly acidic and contains common smoke components in specific proportions, and a large group of aromatic nitrogenated derivatives such as pyrazine and pyridine derivatives in small proportions, together with the main oxygenated terpene derivatives present in the plant; some of the compounds detected in this liquid smoke have not been described as smoke components before.     

Separation and characterization of the constituents of compost and soil humic acids by two-dimensional electrophoresis

To investigate the chemical heterogeneity of humic acids (HAs), we applied two-dimensional (2-D) electrophoresis to HAs from a compost and two types of soils. In this method, HAs are first separated by isoelectric focusing (IEF) and then separated by polyacrylamide gel electrophoresis (PAGE). IEF and PAGE were carried out in the presence of 7?M urea. Upon 2-D electrophoresis of HAs, dark-colored substances were spread out across the gel mainly in the isoelectric point (pI) range of 3.0–4.5. Green fluorescence was observed in the smaller molecular size region of the gel, especially in the pI range of 3.0–4.5, and the most intense fluorescence was found at the moving front. The gels were divided into 36 sections, and then HA constituents were extracted from the individual sections and recovered by precipitation with acid. The distribution of organic carbon (C) among the gel sections coincided with that of the dark-colored substances on the gel. The total C recoveries were only 43–50%, suggesting that a considerable amount of HA constituents was lost during the extraction from the gels and purification. High-performance size-exclusion chromatography confirmed that the constituents of HAs were separated based on their molecular sizes by PAGE. The measurement of diffuse reflectance infrared Fourier transform (DRIFT) spectra indicated that the chemical properties of the HA constituents differed depending on the position on the gels and were affected by the molecular size rather than the pI. The fractions of the compost HA were characterized by higher proportions of aliphatic, proteinous and polysaccharide moieties and by the presence of lignin-derived structures. For the soil HAs, the fractions were characterized by a high proportion of the carboxyl group and a low proportion of aliphatic moieties. The proportion of proteinous and polysaccharide moieties in the fractions of soil HAs decreased with decreasing molecular size. The chemical properties of the green fluorescent substances remained unclear, since there was not enough of the substances to measure the DRIFT spectra. The present study showed that 2-D electrophoresis in the presence of concentrated urea offers an effective method for fractionating and isolating the constituents of HAs.     

Artifact formation during smoke trapping: an improved method for determination of N-nitrosamines in cigarette smoke

Studies in our laboratory revealed artifactual formation of N-nitrosamines during trapping of mainstream and sidestream tobacco smoke by the method of Hoffmann and coworkers (2, 4). Both volatile and tobacco-specific N-nitrosamines were produced. This artifact formation took place on the Cambridge filter, which is part of the collection train used in the previously published procedure. When the filter was treated with ascorbic acid before smoke collection, artifact formation was inhibited. The improved method resulting from these studies was applied to a comparative analysis of N-nitrosamines in smoke from cigarettes that heat, but do not burn, tobacco (the test cigarette) and several reference cigarettes. Concentrations of volatile and tobacco-specific N-nitrosamines in both mainstream and sidestream smoke from the test cigarette were substantially lower than in the reference cigarettes.     

Fractionation of soil humic acids by preparative polyacrylamide gel electrophoresis in the presence of concentrated urea

To separate soil humic acids (HAs) into their constituents and characterize them, polyacrylamide gel electrophoresis (PAGE) was carried out in the presence of 7 M urea using a preparative electrophoresis system. Two types of soil HAs were fractionated into nine fractions by PAGE. The dark-colored constituents were recovered from the electrophoretic fractions by precipitation on acidification, and the brown-colored constituents dissolved in the acidic solution of fast-moving fractions were recovered by adsorption onto DAX-8 resin. High-performance size-exclusion chromatography (HPSEC) confirmed that the constituents of the HAs were separated based on their molecular size by PAGE. The dark-colored constituents exhibited higher degrees of humification than did the corresponding unfractionated HAs, except for the constituents remaining in the electrophoretic gels at the end of electrophoresis. Diffuse reflectance infrared spectroscopy revealed that the chemical properties of the dark-colored constituents changed regularly: the content of carboxyl groups decreased and the proportions of proteinous, aliphatic and polysaccharide moieties increased with increasing molecular size. The humification degrees of the constituents adsorbed onto DAX-8 resin were considerably lower than those of the corresponding unfractionated HAs. The chemical properties of the DAX-8-adsorbed constituents were different from those of the dark-colored constituents. Observation of electrophoretic fractions under blue light (470 nm) and HPSEC with fluorescence detection at an excitation wavelength of 460 nm and an emission wavelength of 520 nm showed that green fluorescent substances were largely concentrated in the smallest molecular size fractions and were partitioned into both the dark-colored precipitates and DAX-8-adsorbed fractions. The proportion of organic carbon recovered by precipitation and adsorption onto DAX-8 resin was 45–63%, indicating that substantial parts of the HA constituents were missing. The unrecovered constituents were considered to be acid-soluble, nearly colorless substances. The dissociation of the acid-soluble constituents from the acid-insoluble dark-colored constituents during the preparative PAGE of soil HAs was ascribed to disruption of hydrogen bonding and hydrophobic interactions caused by concentrated urea.     

Rapid differentiation of tea products by surface desorption atmospheric pressure chemical ionization mass spectrometry

Protonated water molecules generated by an ambient corona discharge were directed to impact tea leaves for desorption/ionization at atmospheric pressure. Thus, a novel method based on surface desorption chemical ionization mass spectrometry (DAPCI-MS) has been developed for rapid analysis of tea products without any sample pretreatment. Under the optimized experimental conditions, DAPCI MS spectra of various tea samples are recorded rapidly, and the resulting mass spectra are chemical fingerprints that characterize the tea samples. On the basis of the mass spectral fingerprints, 40 tea samples including green tea, oolong tea, and jasmine tea were successfully differentiated by principal component analysis (PCA) of the mass spectral raw data. The PCA results were also validated with cluster analysis and supervised PCA analysis. The alteration of signal intensity caused by rough surfaces of tea leaves did not cause failure in the separation of the tea products. The experimental findings show that DAPCI-MS creates ions of both volatile and nonvolatile compounds in tea products at atmospheric pressure, providing a practical and convenient tool for high-throughput differentiation of tea products.