[Pulmonary tissue regeneration -- a hope for the future].
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
J C Wolff
Publications and source records attributed to J C Wolff.
Sulfur-specific detection of impurities in cimetidine drug substance using liquid chromatography coupled to high resolution inductively coupled plasma mass spectrometry and electrospray mass spectrometry.
The use of liquid chromatography coupled to sector field inductively coupled plasma mass spectrometry (SF-ICP-MS) for the specific detection of sulfur-containing compounds is described. In the sulfur-containing drug substance cimetidine, structurally related impurities well below the 0.1% mass fraction level relative to the main drug substance could easily be detected. The structure of most of the impurities was confirmed by electrospray mass spectrometry (ESI-MS), and thus, the complementarity of the two techniques for drug analysis is shown. The limit of detection by SF-ICP-MS for cimetidine in solution was approximately 4-20 ng x g(-1), but it was blank-limited.
Chromatography, Liquid↗
Accurate mass liquid chromatography/mass spectrometry on quadrupole orthogonal acceleration time-of-flight mass analyzers using switching between separate sample and reference sprays. 2. Applications using the dual-electrospray ion source.
A new electrospray dual sprayer, LockSpray, was developed for accurate mass measurements on a quadrupole orthogonal acceleration time-of-flight mass spectrometer (oa-Q-ToF). With the dual-sprayer ion source, both sprays are orthogonal to each other. A mechanism similar to the one employed on the multiplexed electrospray source (MUX) allows switching between reference and sample sprayer. The reference sprayer is optimized for low flow rates, whereas the sample sprayer is a conventional Z-spray type sprayer. Earlier work using a modified MUX ion source on an orthogonal acceleration time-of-flight instrument showed promising results. In this paper, examples obtained with the LockSpray, specifically designed for accurate mass measurements on an oa-Q-ToF, are presented. The examples include results obtained for the identification of impurities in drug substances such as cimetidine and rosiglitazone, using accurate mass tandem mass spectrometry in both positive and negative ion electrospray modes. Good mass accuracies, i.e., within 2 mDa of the theoretical value, were obtained in MS and MS/MS operation.
Calibration↗
Preliminary investigation of the application of on-line membrane extraction of trifluoroacetic acid as an aid to improvement of negative ion electrospray mass spectrometry data.
We have recently investigated the biodegradation of a number of acidic aromatic compounds that give excellent chromatography using trifluoroacetic acid (TFA) based HPLC methods. Unfortunately HPLC methods using TFA are not usually compatible with detection by negative ion mass spectrometry as TFA suppresses ionisation of the analyte during the electrospray process. We present a preliminary investigation of the use of an anion-exchange micro-membrane suppressor to remove TFA on-line post column with the aim of improvement of mass spectral data using an aromatic acid as an example, Thus LC-MS using a TFA based HPLC method with negative ion mass spectral detection is shown to be possible with good sensitivity.
Chromatography, High Pressure Liquid↗
The use of particle beam mass spectrometry for the measurement of impurities in a nabumetone drug substance, not easily amenable to atmospheric pressure ionisation techniques.
Liquid chromatography/particle beam mass spectrometry (LC/PB-MS) was used for the structural elucidation of some impurities in nabumetone as this compound poorly ionises by atmospheric pressure ionisation (API) techniques. PB-MS was optimised for nabumetone and a sensitivity study was carried out. To obtain full scan electron ionisation spectra a minimum of 100 ng of compound on column was needed. By using 20 mg/mL solutions of nabumetone, impurities at levels of about 250 ppm mass fraction relative to nabumetone could be detected. Results were compared with LC/API-MS and previous GC/MS.
Anti-Inflammatory Agents, Non-Steroidal↗
Aerobic biotransformation of 4-fluorocinnamic acid to 4-fluorobenzoic acid.
The biotransformation of 4-fluorocinnamic acid (FCA) using non-acclimated industrial activated sludge was investigated. FCA is a common intermediate in organic synthesis, and it is often present in aqueous waste streams. Hence, the biotransformation reactions this compound undergoes when exposed to activated sludge micro-organisms should be understood before waste streams are sent to biological wastewater treatment plants (WWTPs). FCA biotransformation was monitored using a wide range of analytical techniques. These techniques were used to monitor not only FCA disappearance, but also the formation of degradation products, in order to propose the metabolic pathway. FCA was biotransformed to 4-fluorobenzoic acid via the formation of 4-fluoroacetophenone. The removal of FCA up to 200 mg L(-1) followed first order kinetics. The half-lives for removal of FCA from the test solutions supplied with 200 mg L(-1), 100 mg L(-1), and 50 mg L(-1) were 53, 18, and 5 hours respectively.
Aerobiosis↗
Accurate mass liquid chromatography/mass spectrometry on orthogonal acceleration time-of-flight mass analyzers using switching between separate sample and reference sprays. 1. Proof of concept.
This paper describes the use of two separate electrosprays for introducing sample and reference for accurate mass liquid chromatography/mass spectrometry (LC/MS) on an orthogonal acceleration time-of-flight mass analyzer. This is carried out using an adaptation of the multiplexed electrospray ion source in which only two of the sprays are utilized. Results are shown for the positive ion detection of trace-level components in complex matrixes and good mass accuracies are obtained, even for very low level components. An example of accurate mass measurements obtained using negative ion LC/MS is also shown. To obtain additional structural information, an example of cone voltage fragmentation is included and shows that good mass accuracy can be obtained for both precursor and fragment ions.
Chromatography, Liquid↗
New ultraviolet signal actuated switching valve for the measurement of low level impurities by liquid chromatography/mass spectrometry.
A new ultraviolet (UV) signal actuated switching valve for diverting the main matrix compound to waste, preventing it entering the ion source of the mass spectrometer is described. Sensitivity for trace impurities eluting after the drug substance cimetidine or related compounds could be enhanced by a factor of 4-5. The increase in sensitivity was dependent on the type of ion source which interfaced the mass spectrometer. The benefit of the switching valve was greater with a line of sight type source than with an orthogonal one. The detection limit for a trace compound in a matrix compound was improved by up to a factor of 10 with the line of sight type source but only by a factor of 5 with the orthogonal source.
Cimetidine↗
Traceable values for nitrate in water samples by isotope dilution analysis using a small thermionic quadrupole mass spectrometer.
An isotope dilution mass spectrometric procedure was developed for the determination of nitrate in water samples. The isotope dilution experiments were carried out using the Institute for Reference Materials and Measurements's 15N-enriched nitrate spike reference material IRMM-627. Nitrate was isolated from the matrix by precipitating it as nitron nitrate, from which emission of negative thermal NO2-ions was found to be best. The ions were produced in the ion source of a small, low-cost, easy-to-handle thermionic quadrupole mass spectrometer equipped with a secondary electron multiplier coupled to an ion counter. The procedure developed was applied to the measurement of nitrate in a certified reference material (stimulated rainwater, CRM 409 from Community Bureau of Reference), in sparkling mineral water, and in tap water. Results were compared with those obtained using ion chromatography. Good agreement (within 1%) was found between the concentration determined by isotope dilution mass spectrometry, the values from ion chromatography, and the certified value. The procedure developed allowed accurate and traceable determinations of nitrate in water samples, with an expanded uncertainty (coverage factor k = 2) of 2-5%, and the detection limit was found to be 2 mumol kg-1.
Chromatography, Ion Exchange↗
The University of Kentucky SAMA summer program in health careers.
Explore the source record for details and available documents.
Health Occupations↗