Determination of the fatty acid composition of saponified vegetable oils using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

This is the first report of an application of collisionally induced fragmentation of amino acids (AA) and their derivatives by MALDI TOF/TOF tandem mass spectrometry (MS). In this work, we collected the data on high-energy fragmentation reactions of a large group of protonated amino acids and their derivatives with the goal of determining which product ions are analyte specific and if yields of these fragment could be used for quantitative analysis. From 34 different amino acids (20 ␣-amino acids, ␤-amino acids, homocysteine, GABA, and modified AA Met sulfone and sulfoxide, hydroxyproline, etc.) we observed that high yields of the target specific immonium ions and fragmentation patterns are most similar to EI or FAB CID on sector instruments. The major exceptions were two highly basic amino acids, Arg and Orn. It is noted that neither ␤-, ␥-, nor ␦-amino acids produce immonium ions. As might be predicted from high-energy CID work on peptides from the sectors and TOF/TOF, the presence of specific indicator ions in MALDI tandem MS allows distinguishing isomeric and isobaric amino acids. These indicator ions, in combination with careful control of data acquisition, ensure quantitative analysis of amino acids. We believe our data provide strong ince their introduction in the late 1980s, the soft-ionization techniques, electrospray ionization (ESI) and matrix-assisted laser desorption/ ionization (MALDI), have became the major ionization methods for the analysis of biological molecules. While analysis of large biopolymers is successfully performed by both techniques, analysis of low molecular weight (LMW) molecules such as amino acids, pharmaceuticals, hormones, etc. is predominantly performed by ESI mass spectrometry with quadrupole mass analyzers. The major reasons not to use MALDI have been the abundance of matrix ions in the low mass region (100 to 600 u) and the lack of reasonable precursor selection in a MALDI tandem instrument. Also, until recently, MALDI was not considered to be a technique capable of providing robust quantitative data. Current developments in MALDI hardware [1,2] and increased attention paid to sample preparation have changed the situation. A number of recent publications describe application of MALDI TOF for quantitative studies [3][4][5][6][7][8], including favorable comparisons of MALDI TOF with the more traditional ESI LC/MS quantitation schemes [9 -11]. When installed on QqQ instruments, a MALDI source demonstrated good comparability with an ESI source on the same instrument in quantitative analysis of LMW compounds [12].Amino acid analysis (AAA) is one of the areas where ESI LC/MS/MS was successfully applied. ESI LC/ MS/MS has become a standard analytical tool in the analysis of low molecular weight physiological or therapeutic molecules of interest [13][14][15][16].We decided to examine if the combination of highenergy collision and prompt ion detection characteristic for MALDI TOF MS/MS could be applied for AAA. The proposed application of MALDI TOF for AAA contains some advantages o...

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MALDI TOF/TOF tandem mass spectrometry as a new tool for amino acid analysis

Gogichaeva

Williams

Alterman

2007

“…For this reason, different matrix substances, such as porphyrins [12,13], inorganic material [14 -17], fullerene [18,19], and porous silicon [20], have also been used to eliminate matrix ion interference. Recently, carbon nanotubes as an alternative to conventional organic matrices were utilized successfully for low molecular mass analytes of peptides, organic compounds, and ␤-cyclodextrin [21].…”

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confidence: 99%

Immobilized carbon nanotubes as matrix for MALDI-TOF-MS analysis: Applications to neutral small carbohydrates

Ren

Zhang

Cheng

et al. 2005

161

132

In this work, we reported on the advantages of immobilized carbon nanotubes as a novel MALDI-matrix. Recently, carbon nanotubes have been reported to be an effective MALDI matrix for small molecules (Anal. Chem. 2003, 75, 6191), as it can eliminate the interfering matrix peaks as well as form a web morphology to fully disperse the analyte and allow strong ultraviolet absorption for enhanced pulsed laser desorption and ionization. In our study, to overcome the problem that the carbon nanotube matrix may fly off from the target, a type of polyurethane adhesive, NIPPOLAN-DC-205, is introduced to immobilize carbon nanotubes on the target, which enables widespread application of carbon nanotubes as matrix for MALDI-MS analysis. At the same time, the properties of the carbon nanotubes as an efficient matrix remained after immobilization. The presence of NIPPO-LAN-DC-205 increases the time for analysis at a particular desorption spot by minimizing the time-consuming search for "hot spots" and facilitating experiments such as post source decay (PSD) which need longer-lasting signals. Moreover, NIPPOLAN-DC-205 produces no interference peaks and can easily be cleaned with acetone. Fast evaporation technology may be used to enhance signal reproducibility in MALDI analysis using carbon nanotubes as matrix. Consequently, the applicability of the carbon nanotube as matrix for matrixassisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of low molecular mass analytes is highly improved. The feasibility of the method employing polyurethane is demonstrated by comparison of the results produced from the carbon nanotube matrix with and without immobilization. In addition, neutral small carbohydrates, which are difficult to be ionized normally, can be cationized with high efficiency by MALDI-TOF-MS using the immobilized carbon nanotube matrix. The method was further applied to analyze peptides and detect urine glucose successfully. (J Am Soc Mass Spectrom 2005, 16, 333-339)

“…However, the application of MALDI-TOF-MS in small molecules analysis has been limited, mainly due to ion interference originating from matrices in the low molecule weight region (Ͻ500 Da) [10,11]. To overcome this problem, several alternative matrices, such as high mass molecules [12,13] There has been a great deal of interest in ordered mesoporous materials due to their regular pore sizes in the mesoporous range, high surface areas, high pore volumes, and easy functionalization since they were first reported in 1992 [23,24]. Recently, there have been significant advances in the preparation and modification of mesoporous materials, which allows their utilization in various applications, such as adsorbents [25], catalyst supports [26], nano-templates [27], and nanomaterials [28] for advanced electronics.…”

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“…However, the application of MALDI-TOF-MS in small molecules analysis has been limited, mainly due to ion interference originating from matrices in the low molecule weight region (Ͻ500 Da) [10,11]. To overcome this problem, several alternative matrices, such as high mass molecules [12,13], surfactant suppressed matrix [14], inorganic materials [15], and C 60 [16] have been investigated. Recent developments, which are often referred to as nanoscience, have enabled significant advances in the understanding of matrix materials at the molecular level and have revealed the importance of the nanometer-scale properties of matrices, such as pore size, surface functional groups, and compositions in their consequent matrix performances.…”

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MALDI-TOF-MS analysis of small molecules using modified mesoporous material SBA-15 as assisted matrix

Kim

et al. 2009

Mesoporous silica, SBA-15 was successfully functionalized with quinoline moiety, and was applied as a matrix in the MALDI-TOF-MS analysis of small molecules. The modified SBA-15 material propoxy) quinoline, SBA-15-8QSi] was obtained by using calcined SBA-15 and 8-hydroxy quinoline. The structure of the functionalized mesoporous material was systemically characterized by TEM, the N 2 adsorption-desorption isotherm technique and FT-IR spectra. Compared with DHB and SBA-15, SBA-15-8QSi demonstrated several advantages in the analysis of small molecules with MALDI-TOF-MS, such as less background interference ions, high homogeneity, and better reproducibility. Based on these results, the various analytical parameters were optimized. The ideal operating conditions were (1) methanol used as the dissolving solvent; (2) sample first dropping method; (3) a ratio between the analyte and the matrix of 3.5:10. Under these optimization conditions, a low detection limit (8 pmol for L-Arginine-HCl) and high reproducibility (Յ29%) were obtained. This technique was successfully applied to the analysis of various types of small molecules, such as saccharides, amino acids, metabolites, and natural honey. [7], and synthetic polymers [8,9]. However, the application of MALDI-TOF-MS in small molecules analysis has been limited, mainly due to ion interference originating from matrices in the low molecule weight region (Ͻ500 Da) [10,11]. To overcome this problem, several alternative matrices, such as high mass molecules [12,13] There has been a great deal of interest in ordered mesoporous materials due to their regular pore sizes in the mesoporous range, high surface areas, high pore volumes, and easy functionalization since they were first reported in 1992 [23,24]. Recently, there have been significant advances in the preparation and modification of mesoporous materials, which allows their utilization in various applications, such as adsorbents [25], catalyst supports [26], nano-templates [27], and nanomaterials [28] for advanced electronics. In general, the pore surfaces of mesoporous silica materials are covered with a layer of silanol groups (Si-OH), which can act as the binding sites for desired functional groups via covalent grafting on the surfaces. Hu et al. reported on titanium (IV) immobilized mesoporous silica particles which were used as an enriching trap for small molecules (phosphorylated peptides), determined with MALDI-TOF-MS [29]. In addition, mesoporous silica materials have the advantage of optical transparency in the visible region [30].Herein, we successfully functionalized the mesoporous silica, SBA-15 with an 8-hydroxy quinoline group (SBA-15-8QSi hereafter), and applied the functional material as a matrix for MALDI-TOF-MS analysis. The SBA-15-8QSi material exhibited less ion backAddress reprint requests to Dr.