The Identity Algorithm: How the Most Popular Electron Ionization Mass Spectral Library Search Engine Actually Works.

The Identity algorithm implemented in the MS Search (NIST) software is widely used for library searches of gas chromatography/mass spectrometry data against electron ionization mass spectral databases. It has been available to researchers since 1993, with the release of MS Search 1.5a.

A general procedure for finding potentially erroneous entries in the database of retention indices.

Background: The NIST retention index database is one the most widely used sources of retention indices. In both untargeted analysis and machine learning studies filtering for potential errors is rather lacking or nonexistent. According to our estimates about 80% of the compounds from both NIST 17 and NIST 20 retention index databases have only one RI value per stationary phase, which makes searching for erroneous values with statistical methods impossible.

How searching against multiple libraries can lead to biased results in GC/MS-based metabolomics.

Rationale: Databases of electron ionization mass spectra are often used in GC/MS-based untargeted metabolomics analysis. The results of the library search depend on several factors, such as the size and quality of the database, and the library search algorithm. We found out that the list of considered m/z values is another important parameter.

Multivariate Prognostic Model for Predicting the Outcome of Critically Ill Patients Using the Aromatic Metabolites Detected by Gas Chromatography-Mass Spectrometry.

A number of aromatic metabolites of tyrosine and phenylalanine have been investigated as new perspective markers of infectious complications in the critically ill patients of intensive care units (ICUs). The goal of our research was to build a multivariate model for predicting the outcome of critically ill patients regardless of the main pathology on the day of admission to the ICU. Eight aromatic metabolites were detected in serum using gas chromatography-mass spectrometry.

A general procedure for rounding m/z values in low-resolution mass spectra.

It was revealed that nominal mass spectra extracted from the same NetCDF file using different gas chromatography/mass spectrometry (GC/MS) software products are not identical. This phenomenon is caused by differences in algorithms used for rounding floating-point m/z values to integers. It was found that all programs under consideration (AMDIS, ChemStation, ChromaTOF, MS Search, OpenChrom) use different procedures.

Preparation of W-C-Co Composite Micropowder with Spherical Shaped Particles Using Plasma Technologies.

The possibility of obtaining composite micropowders of the W-C-Co system with a spherical particle shape having a submicron/nanoscale internal structure was experimentally confirmed. In the course of work carried out, W-C-Co system nanopowders with the average particle size of approximately 50 nm were produced by plasma-chemical synthesis. This method resulted in the uniform distribution of W, Co and C among the nanoparticles of the powder in the nanometer scale range.

Structure and Properties of Heat-Resistant Alloys NiAl-Cr-Co- ( La, Mo, Zr, Ta, Re) and Fabrication of Powders for Additive Manufacturing.

The NiAl-Cr-Co- alloys were produced by centrifugal self-propagating high-temperature synthesis (SHS) casting. The effects of dopants = La, Mo, Zr, Ta, and Re on combustion, as well as the phase composition, structure, and properties of the resulting cast alloys, have been studied. The greatest improvement in overall properties was achieved when the alloys were co-doped with 15% Mo and 1.

Urine S-Adenosylmethionine are Related to Degree of Renal Insufficiency in Patients with Chronic Kidney Disease.

Objective: To determine whether urine S-adenosylmethionine (SAM) might be an indicator of chronic kidney disease (CKD).

Methods: We investigated urine levels of SAM and related metabolites (S-adenosylhomocysteine and homocysteine cysteine) in 62 patients (average age, 65.9 years) with CKD (stages II-V).

Predicting the absence of an unknown compound in a mass spectral database.

Only a small subset of known organic compounds (amenable for gas chromatography/mass spectrometry) is present in the largest mass spectral databases (such as NIST or Wiley). Nevertheless, library search algorithms available in the market are not able to predict the absence of a compound in the database. In the present work, we have tried to implement such prediction by means of supervised classification.

Systematic Study of the Behavior of Different Metal and Metal-Containing Particles under the Microwave Irradiation and Transformation of Nanoscale and Microscale Morphology.

In recent years, the application of microwave (MW) irradiation has played an increasingly important role in the synthesis and development of high performance nanoscale catalytic systems. However, the interaction of microwave irradiation with solid catalytic materials and nanosized structures remains a poorly studied topic. In this paper we carried out a systematic study of changes in morphology under the influence of microwave irradiation on nanoscale particles of various metals and composite particles, including oxides, carbides, and neat metal systems.

Spectral skewing in gas chromatography-mass spectrometry: Misconceptions and realities.

In the field of gas chromatography-mass spectrometry, linear quadrupole instruments remain the most popular. Quadrupole mass spectrometers are scanning instruments. It means that ions with different m/z values pass through the quadrupole sequentially.

Evaluation of mass spectral library search algorithms implemented in commercial software.

Performance of several library search algorithms (against EI mass spectral databases) implemented in commercial software products ( acd/specdb, chemstation, gc/ms solution and ms search) was estimated. Test set contained 1000 mass spectra, which were randomly selected from NIST'08 (RepLib) mass spectral database. It was shown that composite (also known as identity) algorithm implemented in ms search (NIST) software gives statistically the best results: the correct compound occupied the first position in the list of possible candidates in 81% of cases; the correct compound was within the list of top ten candidates in 98% of cases.

Distinguishing by principal component analysis of o-xylene, m-xylene, p-xylene and ethylbenzene using electron ionization mass spectrometry.

The possibility of distinguishing between o-, m-, p-xylene and ethylbenzene on the basis of only their 70 eV electron ionization (EI) mass spectra has been investigated. These four isomers were distinguished by principal component analysis (PCA) of respective EI mass spectra (recorded under identical conditions). Considered mass spectra contained either eleven or five m/z values, which had intensity greater than 5% or 10% of base peak, respectively.