Centre for Atmospheric Chemistry

A new IC-ESI-MS/MS method, with simple sample preparation procedure, has been developed for quantification and confirmation of perchlorate (ClO 4 − ) anions in water, fresh and canned food, wine and beer samples at low part-per-trillion (ng l −1 ) levels. To the best of our knowledge, this is the first time an analytical method is used for determination of perchlorate in wine and beer samples. The IC-ESI-MS/MS instrumentation consisted of an ICS-2500 ion chromatography (IC) system coupled to either an API 2000 TM or an API 3200 TM mass spectrometer. The IC-ESI-MS/MS system was optimized to monitor two pairs of precursor and fragment ion transitions, i.e., multiple reaction monitoring (MRM). All samples had oxygen-18 isotope labeled perchlorate internal standard (ISTD) added prior to extraction. Chlorine isotope ratio ( 35 Cl/ 37 Cl) was used as a confirmation tool. The transition of 35 Cl 16 O 4 − (m/z 98.9) into 35 Cl 16 O 3 − (m/z 82.9) was monitored for quantifying the main analyte; the transition of 37 Cl 16 O 4 − (m/z 100.9) into 37 Cl 16 O 3 − (m/z 84.9) was monitored for examining a proper isotopic abundance ratio of 35 Cl/ 37 Cl; and the transition of 35 Cl 18 O 4 − (m/z 107.0) into 35 Cl 18 O 3 − (m/z 89.0) was monitored for quantifying the internal standard. The minimum detection limit (MDL) for this method in de-ionized water is 5 ng l −1 (ppt) using the API 2000 TM mass spectrometer and 0.5 ng l −1 using the API 3200 TM mass spectrometer. Over 350 food and beverage samples were analyzed mostly in triplicate. Except for four, all samples were found to contain measurable amounts of perchlorate. The levels found ranged from 5 ng l −1 to 463.5 ± 6.36 g kg −1 using MRM 98.9 → 82.9 and 100 l injection.

Modern determination techniques for pesticides must yield identification quickly with high confidence for timely enforcement of tolerances. A protocol for the collection of liquid chromatography (LC) electrospray ionization (ESI)-quadruple linear ion trap (Q-LIT) mass spectrometry (MS) library spectra was developed. Following the protocol, an enhanced product ion (EPI) library of 240 pesticides was developed by use of spectra collected from two laboratories. A LC-Q-LIT-MS workflow using scheduled multiple reaction monitoring (sMRM) survey scan, information-dependent acquisition (IDA) triggered collection of EPI spectra, and library search was developed and tested to identify the 240 target pesticides in one single LC-Q-LIT MS analysis. By use of LC retention time, one sMRM survey scan transition, and a library search, 75-87% of the 240 pesticides were identified in a single LC/MS analysis at fortified concentrations of 10 ng/g in 18 different foods. A conventional approach with LC-MS/MS using two MRM transitions produced the same identifications and comparable quantitative results with the same incurred foods as the LC-Q-LIT using EPI library search, finding 1.2-49 ng/g of either carbaryl, carbendazim, fenbuconazole, propiconazole, or pyridaben in peaches; carbendazim, imazalil, terbutryn, and thiabendazole in oranges; terbutryn in salmon; and azoxystrobin in ginseng. Incurred broccoli, cabbage, and kale were screened with the same EPI library using three LC-Q-LIT and a LC-quadruple time-of-flight (Q-TOF) instruments. The library search identified azoxystrobin, cyprodinil, fludioxinil, imidacloprid, metalaxyl, spinosyn A, D, and J, amd spirotetramat with each instrument. The approach has a broad application in LC-MS/MS type targeted screening in food analysis.

ABSTRACT The trihydrate of alendronate sodium (MK-0217) is an important bisphosphonate drug for the treatment of a variety of bone diseases. Determination and characterization of this compound in dosage formulations is challenging since it has no chromophore, and as a highly polar and thermally labile compound, it is not amenable to electron impact mass spectrometry. Ion chromatography coupled with an ion spray mass detector (IC-ISP-MS) in the negative ionization mode was developed and applied to the characterization of this compound. Under these conditions alendronate (m/z 248, [M - H]−, M = parent alendronic acid) was readily observed. The anion can form cluster anions with acid molecules including that of the alendronic acid in the gas phase, which is a distinguishing feature of the IC-ISP-MS spectrum. IC-ISP-MS-MS study of the anion shows that cleavage of the C-P bond(s) is the dominant fragmentation pathway(s) of the anion, characteristic of its structure.

The use of a hybrid triple quadrupole-linear ion trap (QqQ LIT ) mass spectrometer system for a comprehensive study of fragmentation mechanisms is described. The anxiolytic drug, buspirone, was chosen as a model compound for this study. With the advent of a QqQ LIT instrument, both the traditional quadrupole and the new linear ion trap scans (LIT) could be performed in a single LC run. In the past, a sample had to be run on two different instruments, namely, a triple quadrupole instrument (QqQ) and a 3D ion trap (3D IT) to obtain similar information. With the new QqQ LIT technology, collision-induced dissociation (CID) occur in a quadrupole collision cell, q2, and fragment ions are trapped and analyzed in Q3 operated in LIT mode. In this work, high-sensitivity product ion spectra of buspirone were obtained from the one-stage 'Enhanced Product Ion' scan (EPI) with rich product ions and no low mass cut-off. Furthermore, detailed fragmentation pathways were elucidated by further dissociation of each of the fragment ions in the EPI spectrum using MS 3 mode in the same run. The MS 3 scan was performed by incorporating CID in q2, and trapping, cooling, isolation, and resonance-excitation in Q3 when operating in LIT mode. This approach allowed unambiguous assignment of all fragment ions quickly with fewer experiments and easier interpretation than the previous approach. The overall sensitivity for obtaining complete fragment ion data was significantly improved for QqQ LIT as compared with that of QqQ and 3D IT mass spectrometers. This is beneficial for structure determination of unknown trace components. The method allowed structure determination of metabolites of buspirone in rat microsomes at 1 µM concentration, which was a 10-fold lower concentration than was needed for QqQ or 3D IT instruments. The QqQ LIT instrument provided a simple, rapid, sensitive and powerful approach for structure elucidation of trace components.

The activity of many transcriptional regulators is significantly altered by posttranslational modifications of specific sites. For example, the activity of the muscle-restricted transcription factor family myocyte enhancer factor 2 (MEF2) is tightly controlled by phosphorylation. This modification is responsible for either an increase or a decrease in transcriptional activity, depending on the specific amino acid residues that are phosphorylated by signal-dependent kinases. Although mass spectrometry-based methods, such as precursor ion and neutral loss scans, are extremely useful for identifying unknown phosphopeptides from a complex mixture, they do not take advantage of any prior knowledge about the protein being investigated. Quite often a significant amount of information is available. This may include the primary sequence, type of phosphorylation (serine/threonine vs. tyrosine), or predicted phosphoacceptor sites (consensus peptide that is targeted by a kinase). This informati...

The ARCHITECT functional sensitivity (20% CV, 95% CI) ranged from 16.0 to 21.8 ng/mL. The total %CVs were 7.5-11.1% at 87.5 ng/ mL, 6.6-14.3% at 411 ng/mL, and 5.2-10.7% at 916 ng/mL. The following results were obtained in patient correlation studies: ARCHITECT CsA vs. LC/MS/MS yielded a Spearman r value of 0.99, a regression equation of y = 1.10x − 7.1, and an average bias of 30.7 ng/mL; ARCHITECT CsA vs. Dimension Xpand yielded a range of Spearman r values of 0.93 to 0.98, slopes of 0.69 to 1.08, y-intercepts of − 20.1 to 26.1 ng/mL, and an average bias range of − 76.2 to − 6.7 ng/mL (4 sites). Conclusion: The ARCHITECT CsA assay has reduced CsA metabolite interference relative to Dade Dimension.

We report on the transformation of tamoxifen at 378C in synthetic gastric fluid as studied by high-performance liquid chromatography with triple quadrupole mass spectrometry. The major transformation products detected were (E)-isomer of tamoxifen, metabolite D, and several unidentified components having m /z 404. Addition of pepsin to the gastric fluid inhibited formation of all of these products. We analyzed several urine samples from breast cancer patients undergoing tamoxifen treatment. Metabolite D was identified in the urine samples and in the gastric fluid digest at a retention time of 22.0 min eluting from a reversed-phase HPLC column. Although several metabolites were found in all the urine samples of patients, some metabolites were detected in one sample but not others, suggesting tamoxifen metabolism varies in patients.

To analyze the naphthenic acid content of environmental waters quickly and efficiently, we have developed a method that employs differential mobility spectrometry (DMS) coupled to mass spectrometry (MS). This technique combines the benefits of infusion-based MS experiments (parallel, on-demand access to individual components) with DMS's ability to provide liquid chromatography-like separations of isobaric and isomeric compounds in a fraction of the time. In this study, we have applied a DMS-MS workflow to the rapid gas-phase separation of naphthenic acids (NAs) within a technical standard and a real-world oil sands process-affected water (OSPW) extract. Among the findings provided by this workflow are the rapid characterization of isomeric NAs (i.e., same molecular formulas) in a complex OSPW sample, the ability to use DMS to isolate individual NA components (including isomeric NAs) for in-depth structural analyses, and a method by which NA analytes, background ions, and dimer s...

erchlorate has received widespread attention as an environmental pollutant over the past several years. Perchlorate was most recently monitored for occurrence in drinking waters under U.S. EPA’s first Unregulated Contaminated Monitoring Rule (UCMR) using an ion chromatography (IC) suppressed conductivity detection technique according to the procedural requirements of EPA Method 314.0. Based on the monitoring data collected during UCMR, the U.S. EPA proposed a regulatory limit for perchlorate in drinking water of 1 mg/L. In addition, new methods capable of reliable determination of perchlorate safely below this limit have been developed by U.S. EPA, including Methods 314.1, 331.0, and 332.0. Method 332.0 relies on an IC separation with either mass spectrometry (MS) or tandem mass spectrometry (MS-MS) for detection and quantitation. This application note demonstrates the use and advantages of IC–MS-MS per Method 332.0 (1).

To analyze the naphthenic acid content of environmental waters quickly and efficiently, we have developed a method that employs differential mobility spectrometry (DMS) coupled to mass spectrometry (MS). This technique combines the benefits of infusion-based MS experiments (parallel, on-demand access to individual components) with DMS's ability to provide liquid chromatography-like separations of isobaric and isomeric compounds in a fraction of the time. In this study, we have applied a DMS-MS workflow to the rapid gas-phase separation of naphthenic acids (NAs) within a technical standard and a real-world oil sands process-affected water (OSPW) extract. Among the findings provided by this workflow are the rapid characterization of isomeric NAs (i.e., same molecular formulas) in a complex OSPW sample, the ability to use DMS to isolate individual NA components (including isomeric NAs) for in-depth structural analyses, and a method by which NA analytes, background ions, and dimer species can be characterized by their distinct behaviors in DMS. Overall, the profiles of the NA content of the technical and OSPW samples were consistent with published values for similar samples, such that the benefits of DMS technology do not detract from the workflow's accuracy or quality.

We report on the transformation of tamoxifen at 378C in synthetic gastric fluid as studied by high-performance liquid chromatography with triple quadrupole mass spectrometry. The major transformation products detected were (E)-isomer of tamoxifen, metabolite D, and several unidentified components having m /z 404. Addition of pepsin to the gastric fluid inhibited formation of all of these products. We analyzed several urine samples from breast cancer patients undergoing tamoxifen treatment. Metabolite D was identified in the urine samples and in the gastric fluid digest at a retention time of 22.0 min eluting from a reversed-phase HPLC column. Although several metabolites were found in all the urine samples of patients, some metabolites were detected in one sample but not others, suggesting tamoxifen metabolism varies in patients.