PubMed · 12872241
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Wayne F Patton. 2003. Editorial.. https://doi.org/10.1002/pmic.200390091
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A quantitative and confirmatory method for the analysis of trinexapac (free acid metabolite of trinexapac-ethyl) in wheat is described. Residues were extracted from wheat with acetonitrile in aqueous phosphate buffer (pH 7) overnight. The extract was directly injected into the HPLC system. Chromatographic separation was achieved on an octadecylsilica column, and detection was performed by negative ion electrospray ionization tandem mass spectrometry. The precursor ion of trinexapac [M - H](-) at m/z 223 was subjected to collisional fragmentation with argon to yield two intense diagnostic product ions at m/z 135 and 179, respectively. Accuracy and specificity for routine analysis of trinexapac were demonstrated. The validated concentration range was 10-200 microg/kg based on a 0.10 g/mL wheat sample extract. Recoveries were within the range of 71-94%, with associated relative standard deviations better than 10%. The limit of detection for trinexapac in wheat was estimated at 5 microg/kg. The method has been applied to a survey of 100 samples of wheat. In 46% of the samples analyzed, a quantifiable amount of trinexapac was detected, ranging from 10 to 110 microg/kg. It has been demonstrated that analyses of trinexapac accurately reflect the total amount of residues of the plant growth regulator, trinexapac-ethyl, in the wheat samples following field application. No residues of the parent compound, trinexapac-ethyl, in wheat were detected.
Flue gas and fly ash samples have a complex composition. Thus, thorough extraction and selective cleanup prior to analysis are essential. This paper presents an evaluated method for determining halogenated dibenzo-p-dioxins (PXDD), halogenated dibenzofurans (PXDF), chlorinated biphenyls (PCB), chlorobenzenes (CBz), -phenols (CPh), dibenzo-p-dioxins (DD), dibenzofurans (DF), and polycyclic aromatic hydrocarbons (PAH) in a single sample. Since these combustion byproducts are ubiquitous, harmful environmental contaminants it is very important to obtain reliable assessments of them: especially specific PCDD/F and PCB congeners with Ah-receptor mediated toxicity. The reported method for this purpose includes techniques such as solid-phase extraction, Soxhlet-Dean-Stark extraction, cleanup using open liquid chromatographic columns, and finally GC/MS analysis/determination with quantification by the isotope dilution technique. The validation results presented here show good reproducibility for PXDD/F and PCB and are satisfactory for CPh, CBz, and PAH. An extraction efficiency test revealed that a nonpolar solvent did not completely extract a few analytes, i.e., diCPh and fluorene, which appear to require a more polar extraction agent. To pinpoint and minimize the loss of analytes, specific studies on reductions of their amounts during sample concentration were performed, showing that traditional rotary evaporation and nitrogen blow-down produce equally good results as a novel technique.
Covalent post-synthesis or solid-phase conjugation of peptides to oligonucleotides has been reported as a possible method of delivering antisense oligonucleotides into cells. While synthesis strategies for preparing these conjugates have been widely addressed, few detailed reports on their structural characterization have been published. This paper discusses the negative ion electrospray ionization mass spectrometric (ESI-MS) and liquid chromatography-mass spectrometric (LC-MS) analysis of various peptide-oligonucleotide conjugates ranging from small T(6)-nucleopeptides to large peptide-oligonucleotide phosphorothioate conjugates and ribozyme-peptide hybrids (3-13 kDa). Molecular weight determination with mass errors of 0.1-3.1 amu were conducted, employing on-line IP-RP-HPLC and high m/z range mode to facilitate the analysis of large compounds and difficult modifications.