Evaluation of GC-ICP-MS/MS as a New Strategy for Specific Heteroatom Detection of Phosphorus, Sulfur, and Chlorine Determination in Foods.

For the first time in the literature, application of a GC-ICP-MS/MS method for the selective and sensitive detection of specific heteroatoms of phosphorus, sulfur, and chlorine has been accomplished. As a proof of concept, organophosphorus, organosulfur, and organochlorine pesticides in various food matrices have been studied. For the detection of organophosphorus and organosulfur pesticides, oxygen was used in the collision reaction cell (CRC) to convert P (m/z 31) to PO(+) (m/z 47) and S (m/z 32) to SO(+) (m/z 48). Similarly, ClH2(+) (m/z 37) was monitored after the reaction of Cl (m/z 35) with hydrogen in the CRC for the determination of organochlorine pesticides. Real food samples (baby food purees, fresh vegetables, loose tea) were screened for their pesticide content, following preparation of triplicate extracts using QuEChERS (quick, easy, cheap, effective, rugged, and safe). Excellent linearity with correlation coefficients R ≥ 0.997 was achieved, and the lowest detection limits obtained for the organophosphorus, organosulfur, and organochlorine pesticides were 0.0005, 0.675, and 0.144 µg/kg, respectively.

Studying protein phosphorylation in low MW CSF fractions with capLC-ICPMS and nanoLC-CHIP-ITMS for identification of phosphoproteins.

An initial study of protein phosphorylation in human cerebral spinal fluid (CSF) is described. CSF is an important body fluid for study of proteins and metabolites and may lead to the ultimate development of molecular markers to predict neurological diseases or their complications, such as in the case of hemorrhagic stroke. The use of capillary liquid chromatography coupled to inductively coupled plasma mass spectrometry (capLC-ICPMS) for screening using (31)P as the internal elemental tag atom at ultratrace levels, in combination with molecular mass spectrometry using Spectrum Mill and MASCOT database search engines for peptide identification, is a novel approach in its application to CSF relevant phosphopeptides and phosphorylated proteins. CapLC-ICPMS combined with nano liquid chromatography electrospray ionization, ion trap mass spectrometry (nanoLC-CHIP/ITMS), was utilized for initial experiments with CSF. Specific low-level screening for (31)P containing compounds is accomplished, and nanoLC-CHIP/ITMS provided the corresponding peptide information and subsequent protein identifications. The fractions containing (31)P from screening by the capLC-ICPMS were collected offline and analyzed separately with nanoLC-CHIP/ITMS. Synthetic phosphopeptides were used to test the method and to estimate lowest quantifiable limits for phosphorus. Tryptically digested beta-casein was then used to demonstrate the viability of the methodology for the complex CSF matrix from hemorrhagic stroke patients while also analyzing for native phosphopeptides in the CSF.

A preliminary study of metalloproteins in CSF by CapLC-ICPMS and NanoLC-CHIP/ITMS.

Cerebrospinal fluid (CSF) has frequently been studied to explore the total metal concentrations in patients with neurodegenerative diseases. Some examples of neurologic diseases include but are not limited to intracerebral hemorrhage, intraventricular hemorrhage, traumatic brain injury, subarachnoid hemorrhage and hydrocephalus. In this study, however, a comprehensive approach was begun using metallomics methods. First, two molecular weight cutoff filters were used to separate CSF constituents by molecular weight. The remaining CSF was then separated with capillary liquid chromatography/normal bore liquid chromatography and analyzed with inductively coupled mass spectrometry (ICPMS). With this ICPMS screening, a possible iron associated protein was suggested by nanoliquid chromatography-CHIP/ion trap mass spectrometry (nanoLC-CHIP/ITMS) identification in conjunction with a Spectrum Mill database search. In this preliminary study, three different types of pooled CSF were partially characterized by their metal (Pb, Mg, Zn, Fe and Cu) containing species with suggestions for fuller studies. Chemical 'differences' in the CSF and metal constituents suggests some utility in this analysis for understanding some of the complications observed following subarachnoid hemorrhage.