Preliminary investigation of the simultaneous detection of sugars,ascorbic acid,citric acid,and sodium benzoate in non-alcoholic beverages by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the simultaneous detection of sugars, ascorbic acid, citric acid, sodium and/or potassium benzoate in non-alcoholic beverages, with meso-tetrakis(pentafluorophenyl)porphyrin (MW 974) as a matrix. Using potassium hydroxide as dopant, fructose/glucose was detected as the potassiated molecule at m/z 219, whereas potassiated sucrose, [Sucrose. K](+), was detected at m/z 381. Using sodium hydroxide as dopant, the fructose and sucrose ions were detected at m/z 203 and 365, respectively. Citric acid generated multiple ions at m/z 269, 307, and 345, which were assigned to [Citricbond;H+2K](+), [Citricbond;2H+3K](+), and [Citricbond;3H+4K](+), respectively. However, a stored methanolic solution of citric acid produced additional ions at m/z 283, 297, and 321, which were attributed to [Citricbond;2H+CH(3)+2K](+), [Citricbond;3H+2CH(3)+2K](+), and [Citricbond;3H+CH(3)+3K](+), respectively, due to esterification that took place during storage. The limits of detection in water were: ascorbic acid, 0.30 wt%; citric acid, 0.5 wt%; and sodium benzoate, 0.001 wt%. In the beverage formulations, the limits of detection were: ascorbic acid 0.3 wt%, citric acid 0.3 wt%, and sodium benzoate 0.02 wt%. Spiking a water or beverage solution that contained ascorbic and/or citric acid with less than 0.6 wt% of tartaric acid lowered the detection limits of ascorbic and citric acids to 0.2 wt%. This study demonstrates the potential for using MALDI-TOFMS in the quality control analyses of non-alcoholic beverages, particularly with regard to the detection of low molecular weight organic acids in commercial beverage formulations.     

Mass spectrometric profiling of N-linked oligosaccharides and uncommon glycoform in mouse serum with head and neck tumor

N-linked oligosaccharides obtained from total serum of mice with implanted head and neck tumors were analyzed and compared with those from control samples of healthy mice. Methods used include a combination of a derivatization procedure with phenylhydrazine (PHN) and analysis by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Oligosaccharides were enzymatically released from total serum with PNGaseF and purified by high-performance liquid chromatography (HPLC) on a reversed-phase column. Mass spectra contained ion peaks of labeled oligosaccharides and MS/MS experiments provided useful data for the structural elucidation of these compounds. More than 40 N-glycans with compositions characteristic of high-mannose, hybrid, complex, neutral, and sialylated structures were identified in the serum of tumoral mice. Significant differences between samples were observed with respect to the abundances of high mannose and hybrid glycans. These oligosaccharides showed higher relative intensities in the spectra obtained from the cancer sera. Complex sialylated oligosaccharides had similar abundances in both types of sera, with the exception of fucosylated biantennary disialylated oligosaccharide, which was mostly detected with lower abundance in control samples. In the MALDI spectra, several minor species corresponded to uncommon carbohydrates. These structures have been investigated in detail by MS/MS. Among these novel glycoforms, a few sialylated oligosaccharides without a free reducing end were identified. Also, glycans with an extra 60 u were observed and likely feature the presence of a 2-acetamido-2-deoxyoctose residue attached on antennae of 3- or 6-linked mannose.     

Negative ion laser desorption ionization time-of-flight mass spectrometry of nitrated polycyclic aromatic hydrocarbons

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are widespread environmental pollutants that are generated by incomplete combustion and by atmospheric transformation of polycyclic aromatic hydrocarbons (PAHs). Many nitro-PAH compounds are potent genotoxins and some are direct acting mutagens. Detection of nitro-PAHs in aerosols is complicated by small sample sizes and nitro-PAH abundances that are 1–2 orders of magnitude less than analogous unsubstituted PAHs. Selective detection of several nitro-PAHs by using laser desorption ionization time-of-flight mass spectrometry in negative ion mode has been achieved. Desorption and ionization of nitro-PAHs were effected by using pulsed UV radiation at 266 and 213 ran. Intense molecular anions were observed in addition to fragments identified as CN^? and NO ₂ ^? , which were characteristic indicators of the presence of nitro-PAHs. Selective detection of nitro-PAHs in negative ion mode was demonstrated in the analysis of a diesel particulate sample.     

Simultaneous Determination of Tobacco Alkaloids,Tobacco-Specific Nitrosamines,and Solanesol in Consumer Products Using UPLC–ESI-MS/MS

The US Alcohol and Tobacco Tax and Trade Bureau (TTB) is responsible for collecting Federal excise taxes on tobacco products. Tobacco products in the USA may fall into several taxable categories including cigars, cigarettes, snuff, chewing tobacco, pipe tobacco, and roll-your-own. The existence of these taxable categories means that the TTB is also responsible for the determination of proper tax classification. Not only does proper classification determine the amount of tax owed, but comprehensive classification procedures must also determine if a consumer product is subject to the tobacco excise tax. Since a product must contain tobacco to be subject to the excise tax, laboratory methods that test for the presence of tobacco can provide useful information to ascertain the taxable status of a product. To test for the presence of chemical markers associated with tobacco, an analytical method was developed that permits the simultaneous determination of nicotine and related alkaloids, tobacco-specific nitrosamines (TSNA), and solanesol in methanolic extracts of tobacco. The method utilizes ultra performance liquid chromatography with electrospray ionization–tandem mass spectrometric detection (UPLC–ESI-MS/MS) and was optimized for the analysis of nicotine, cotinine, nornicotine, anatabine, myosmine, anabasine, isonicoteine, nornicotyrine, nicotyrine, N-nitrosoanatabine (NAT), N-nitrosoanabasine (NAB), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N′-nitrosonornicotine (NNN) and solanesol. The analytical method was designed to attenuate the instrument response of nicotine, which is overwhelming, to permit simultaneous analysis of all analytes.     

Determination of nitrated polycyclic aromatic hydrocarbons in diesel particulate-related standard reference materials by using gas chromatography/mass spectrometry with negative ion chemical ionization

Gas chromatography/mass spectrometry (GC/MS) with negative ion chemical ionization (NICI) detection was utilized for quantitative determination of nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in diesel particulate-related standard reference materials (SRMs). Prior to GC/MS analysis, isolation of the nitro-PAHs from the complex diesel particulate extract was accomplished using solid phase extraction (SPE) and normal-phase liquid chromatographic (LC) fractionation using an amino/cyano stationary phase. Concentrations of eight to ten mononitro-PAHs and three dinitropyrenes were determined in three diesel particulate-related SRMs: SRM 1650a Diesel Particulate Matter, SRM 1975 Diesel Particulate Extract, and SRM 2975 Diesel Particulate Matter (Industrial Forklift). The results from GC/MS NICI using two different columns (5% phenyl methylpolysiloxane and 50% phenyl methylpolysiloxane) were compared to each other and to results from two other laboratories for selected nitro-PAHs. 1-Nitropyrene was the most abundant nitro-PAHs in each of the diesel particulate SRMs (19.8+/-1.1 micro g g(-1) particle in SRM 1650a and 33.1+/-0.6 micro g g(-1) particle in SRM 2975). Three dinitropyrene isomers were measured in SRM 1975 at 0.5-1.4 micro g g(-1) extract and in SRM 2975 at 1-3 micro g g(-1) particle.     

Matrix-assisted laser desorption/ionization on-target method for the investigation of oligosaccharides and glycosylation sites in glycopeptides and glycoproteins

The significance of glycoproteins in living systems instigates the ceaseless expansion of new techniques and procedures for the analysis of biological samples. Many of these applications are focused on improving the detection limit of analyzed material. In a previous study, we described a procedure for the detection of oligosaccharides cleaved from tryptic glycopeptides. Treatment of deglycosylated fractions with phenylhydrazine gave rise to peaks consistent with labeled glycans, and both types of compounds--deglycosylated peptides and oligosaccharides--were recorded from one spot and observed in one matrix-assisted laser desorption/ionization (MALDI) mass spectrum for the first time. Here, we added an additional step to this simple procedure of deglycosylating glycopeptides directly from the target spot of the first analyzed glycosylated peptides. For the purpose of this new study, a mixture of 2-aza-2-thiothymine and phenylhydrazine hydrochloride showed to be an excellent matrix for glycopeptides, oligosaccharides, deglycosylated peptides and moreover it allowed PNGaseF to be active enough to cleave oligosaccharides from peptides. The efficiency of this procedure is demonstrated on a series of intact glycoproteins and on the analysis of tryptic peptides obtained from IgG and total mouse serum. This one-step on-target deglycosylation method with subsequent derivatization on the same spot makes MALDI-MS analyses of glycopeptides fast, simple and accessible for biological samples, where classical procedures cannot produce useful results.