Comparison and evaluation of analysis procedures for the quantification of (2-methoxyethoxy)acetic acid in urine

Several extraction and derivatization procedures were evaluated for the quantification of (2-methoxyethoxy)acetic acid (MEAA) in urine. MEAA is a metabolite and a biomarker for exposure to 2-(2-methoxyethoxy)ethanol, a glycol ether with widespread use in various industrial applications and the specific use as an anti-icing additive in the military jet fuel formulation JP-8. Quantification of glycol ether biomarkers is an active area of analytical research. Various sample preparation procedures were evaluated: liquid–liquid extraction (LLE) using ethyl acetate yielded the highest recovery, and solid-phase extraction (SPE) gave low recovery of MEAA. Two derivatization procedures were thoroughly investigated and validated, namely, silylation of MEAA with N-methyl-N-(tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA), and esterification of MEAA using ethanol. Quantification was performed by gas chromatography (GC) with a mass spectrometer as detector and using a polydimethylsiloxane (HP-1) capillary column. Deuterated 2-butoxyacetic acid (d-BAA) was used as an internal standard. Recovery studies of spiked human urine demonstrated the accuracy and precision of both procedures. The limit of detection (LOD) and other figures of merit for both derivatization procedures will be discussed in detail. Applications of these analysis procedures are also discussed. Disclaimers Mention of company names and/or products does not constitute endorsement by the Centers for Disease Control and Prevention (CDC). The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.     

A high-frequency titration apparatus

A high-frequency titrimeter which responds to either effective capacitance or to effective conductance changes in the titration cell circuit is described. The instrument is simple, inexpensive and reliable. An easy, yet accurate, method of measuring effective capacitance changes is used. Typical titration curves are given. Some novel methods of temperature control are presented including the use of the electrodes themselves as a means of regulating the temperature of the solution.     

THE EFFECT OF PHOSPHORYLATION UNCOUPLERS AND ELECTRON TRANSPORT INHIBITORS UPON SPECTRAL SHIFTS AND DELAYED LIGHT EMISSION OF PHOTOSYNTHETIC BACTERIA

Abstract— Delayed light emission (measured 4 msec after excitation) and the light-induced red shifts of the bacteriochlorophyll and carotenoid absorption bands of chromatophores of Rhodopseudomonas spheroides were inhibited by a variety of reagents. These included anti-mycin A, NQNO, CCCP, desaspidin, quinacrine, chlorpromazine, 2,4-dinitrophenol, gramicidin D, Triton X-100 and valinomycin in the presence of potassium, cesium or ammonium ions. Delayed light emission was enhanced by orthophenanthroline, ethanol, succinate and glutathione.
Delayed light emission from chromatophores of Rhodospirillum rubrum was attenuated during photophosphorylation but restored approximately to its initial value in the presence of oligomycin. Since the delayed light and band shifts are inhibited under conditions which tend to deplete or block the formation of high energy phosphorylation intermediate, it is suggested that the presence of a high energy intermediate is a prerequisite for the appearance of each of the three phenomena.     

Lipid imaging in the zebra finch brain with secondary ion mass spectrometry

Lipids have diverse functions in the nervous system, but the study of their anatomical distributions in the intact brain is rather difficult using conventional methodologies. Here we demonstrate the application of high resolution time-of-flight (ToF) secondary ion mass spectrometry (SIMS) to image various lipid components and cholesterol across an entire brain section prepared from an adult zebra finch (Taeniopygia guttata), with a spatial resolution of 2.3 μm, resulting in the formation of 11.5 megapixel chemical images. The zebra finch is a songbird in which specific neural and developmental functions have been ascribed to discrete “song control nuclei” of the forebrain. We have observed a relative increase of palmitic acid C16:0 and oleic acid C18:1 in song control nuclei versus the surrounding tissue, while phosphate (PO₃⁻), representative of phospholipids, was lower in these regions. Cholesterol was present at a high level only in the white matter of the optic tectum. More diffuse distributions were observed for stearic, arachidonic, linolenic, and palmitoleic acids. The presented results illustrate that SIMS imaging is a useful approach for assessing changes in lipid content during song circuit development and song learning.     

Production of π0 mesons and charged hadrons in\bar v neon and ν neon charged current interactions

The average multiplicities of charged hadrons and of π⁺, π^? and π⁰ mesons, produced in \(\bar v\) Ne and νNe charged current interactions in the forward and backward hemispheres of theW ^±-nucleon center of mass system, are studied with data from BEBC. The dependence of the multiplicities on the hadronic mass (W) and on the laboratory rapidity (y _Lab) and the energy fraction (z) of the pion is also investigated. Special care is taken to determine the π⁰ multiplicity accurately. The ratio of average π multiplicities \(\frac{{2\left\langle {n_{\pi ^O } } \right\rangle }}{{[\left\langle {n_{\pi ^ + } } \right\rangle + \left\langle {n_{\pi ^ - } } \right\rangle ]}}\) is consistent with 1. In the backward hemisphere \(\left\langle {n_{\pi ^O } } \right\rangle \) is positively correlated with the charged multiplicity. This correlation, as well as differences in multiplicities between \(\mathop v\limits^{( - )} \) and \(\mathop v\limits^{( - )} \) , \(\mathop v\limits^{( - )} \) scattering, is attributed to reinteractions inside the neon nucleus of the hadrons produced in the initial \(\mathop v\limits^{( - )} \) interaction.     

Elucidation of PEGylation site with a combined approach of in-source fragmentation and CID MS/MS

Poly(ethylene glycol) (PEG)ylation of peptides and proteins creates significant challenges for detailed structural characterization, such as PEG heterogeneity, site of addition and number of attached PEGylated moieties. Recently, we published a novel LC/MS methodology with a post-column addition of amines to obtain accurate masses of PEGylated peptides and proteins. The accurate masses can be used to assign the structures and number of attached PEGs [15], but the PEGylation site remains unclear in situations where multiple potential attachments are involved. Here, we present a methodology combining in-source fragmentation (ISF) with CID-MS/MS to elucidate the PEGylated sites in PEGylated products. All PEGylated samples, either prepared in acidic solution, or collected from a RP-HPLC stream, were first ionized via ISF to produce products containing small PEG fragment attachment, and then those fragment ions obtained were sequenced via CID MS/MS to deduce the PEGylation site. The methodology was successfully applied to PEGylated glucagon and IgG4 antibody light chain, which demonstrated that the small PEG fragments attached were stable during the CID activation.     

On the Coherence of Inversion

In this paper, I shall evaluate a strategy recently used to try to demonstrate the impossibility of behaviorally undetectable spectrum inversion. After showing that the impossibility proof proves too much, I shall identify where it goes wrong. In turn, I shall explain why someone attracted to functionalist and representationalist assumptions might rightly remain agnostic about the possibility of inversion.