Scanwave: a new approach to enhancing spectral data on a tandem quadrupole mass spectrometer

Simultaneous Quantification of Steroid Hormones Using hrLC-MS in Endocrine Tissues of Male Rats and Human Samples

Steroid hormones play a vital role in the regulation of cellular processes, and dysregulation of these metabolites can provoke or aggravate pathological issues, such as autoimmune diseases and cancer. Regulation of steroid hormones involves different organs and biological compartments. Therefore, it is important to accurately determine their levels in tissues and biofluids to monitor changes after challenge or during disease. In this work, we have developed and optimized the extraction and quantification of 11 key members of the different steroid classes, including androgens, estrogens, progestogens and corticoids. The assay consists of a liquid/liquid extraction step and subsequent quantification by high-resolution liquid chromatography coupled time-of-flight mass spectrometry. The recoveries range between 74.2 to 126.9% and 54.9 to 110.7%, using a cell culture or urine as matrix, respectively. In general, the signal intensity loss due to matrix effect is no more than 30%. The method has been tested in relevant steroidogenic tissues in rat models and it has also been tested in human urine samples. Overall, this assay measures 11 analytes simultaneously in 6 min runtime and it has been applied in adrenal gland, testis, prostate, brain and serum from rats, and urine and extracellular vesicles from humans.

Advances in the analytical methods for the determination of fluorinated aromatic carboxylic acids in aqueous matrices: A review

Fluorobenzoic acids are critically important chemical tracers in hydrothermal, geothermal, leaching, and oilfield applications. Particularly in oilfield applications, these tracers are used to investigate fluid flow paths between injector wells and producer wells, providing valuable information about the enhanced oil recovery process of the oil reservoirs. The detection limit of tracers is a vital subject in field reservoir work because the amount of chemical tracer that must be injected into the injector well is directly related to the amount detected at the producer well after migration and diffusion. The popularity of fluorinated benzoic acids as the tracers is due to their non-toxicity over radioactive tracers and low detection limit, which is determined using analytical techniques. This review focuses on the improvements/developments in extraction techniques such as solid-phase extraction and determination techniques such as gas chromatography coupled with mass spectrometry, liquid chromatography with mass spectrometry, isotope dilution gas chromatography-mass spectrometry, high-performance liquid chromatography, ion chromatography coupled with electrospray mass spectrometry, and so on for the analysis of fluorinated benzoic acids to achieve the lowest possible limit of concentration.

Proton Transfer Accounting for Anomalous Collision-Induced Dissociation of Proton-Bound Hoogsteen Base Pair of Cytosine and Guanine

To understand the anomalous collision-induced dissociation (CID) behavior of the proton-bound Hoogsteen base pair of cytosine (C) and guanine (G), C:H⁺∙∙∙G, we investigated CID of a homologue series of proton-bound heterodimers of C, 1-methylcytosine, and 5-methylcytosine with G as a common base partner. The CID experiments were performed in an energy-resolved way (ER-CID) under both multiple and near-single collision conditions. The relative stabilities of the protonated complexes examined by ER-CID suggested that the proton-bound complexes produced by electrospray ionization in this study are proton-bound Hoogsteen base pairs. On the other hand, in contrast to the other base pairs, CID of C:H⁺∙∙∙G exhibited more abundant productions of C:H⁺, the fragment protonated on the moiety with a smaller proton affinity, than that of G:H⁺. This appeared to contradict general prediction based on the kinetic method. However, further theoretical exploration of potential energy surfaces found that there can be facile proton transfers in the proton-bound Hoogsteen base pairs during the CID process, which makes the process accessible to an additional product state of O-protonated C for C:H⁺ fragments. The presence of an additional dissociation channel, which in other words corresponds to twofold degeneracy in the transition state leading to C:H⁺ fragments, effectively doubles the apparent reaction rate for production of C:H⁺. In this way, the process gives rise to the anomaly, the observed pronounced formation of C:H⁺ in the CID of the proton-bound Hoogsteen base pair, C:H⁺∙∙∙G. Graphical Abstract ᅟ.

2,4-D and IAA Amino Acid Conjugates Show Distinct Metabolism in Arabidopsis

The herbicide 2,4-D exhibits an auxinic activity and therefore can be used as a synthetic and traceable analog to study auxin-related responses. Here we identified that not only exogenous 2,4-D but also its amide-linked metabolite 2,4-D-Glu displayed an inhibitory effect on plant growth via the TIR1/AFB auxin-mediated signaling pathway. To further investigate 2,4-D metabolite conversion, identity and activity, we have developed a novel purification procedure based on the combination of ion exchange and immuno-specific sorbents combined with a sensitive liquid chromatography-mass spectrometry method. In 2,4-D treated samples, 2,4-D-Glu and 2,4-D-Asp were detected at 100-fold lower concentrations compared to 2,4-D levels, showing that 2,4-D can be metabolized in the plant. Moreover, 2,4-D-Asp and 2,4-D-Glu were identified as reversible forms of 2,4-D homeostasis that can be converted to free 2,4-D. This work paves the way to new studies of auxin action in plant development.

A fast method for the quantitation of key metabolites of the methionine pathway in liver tissue by high-resolution mass spectrometry and hydrophilic interaction ultra-performance liquid chromatography

We developed an assay for the extraction and simultaneous quantitation of five key metabolites of the methionine metabolic pathway in liver tissue. The metabolites included were 5'-methylthioadenosine, methionine, homocysteine, S-adenosyl-L-homocysteine, and S-adenosyl-L-methionine. The metabolites were extracted using a bead-based homogenization method, and quantitation was carried out using hydrophilic interaction chromatography and time-of-flight mass spectrometry. The extraction procedure was optimized by testing the effect of various solvent combinations. The chromatographic method was optimized for peak shape, signal intensity, and carry-over. With a total chromatographic run time of 5 min, this assay is suitable for the analysis of large sample sets. Time-of-flight mass spectrometry provided high mass accuracy which, combined with isotope pattern matching and use of chemical standards, guarantees high specificity. Moreover, by operating the mass spectrometer in enhanced duty cycle mode the signal strength for the analytes increased three- to tenfold in comparison with the generic full-scan mode. For quantitation, a matrix-spiked calibration method was used. The lowest analyte levels detected and quantified using our method were within the range of concentrations found in the liver. The inter-day coefficients of variance for the analytes were between 5 and 15% in pooled tissue samples. Interestingly, the CVs between individual liver tissue aliquots were about twice as high. Additional experiments suggested that this higher variability was caused by uneven distribution of the analytes within the liver. In conclusion, an optimized and robust assay is now available for the extraction and quantification of key metabolites in the methionine metabolic pathway.

A new approach for cytokinin isolation from Arabidopsis tissues using miniaturized purification: pipette tip solid-phase extraction

BACKGROUND

We have developed a new analytical approach for isolation and quantification of cytokinins (CK) in minute amounts of fresh plant material, which combines a simple one-step purification with ultra-high performance liquid chromatography-fast scanning tandem mass spectrometry.

RESULTS

Plant tissue samples (1-5 mg FW) were purified by stop-and-go-microextraction (StageTip purification), which previously has only been applied for clean-up and pre-concentration of peptides. We found that a combination of two reverse phases and one cation-exchange phase, was the best tool, giving a total extraction recovery higher than 80%. The process was completed by a single chromatographic analysis of a wide range of naturally occurring cytokinins (bases, ribosides, O- and N-glucosides, and nucleotides) in 24.5 minutes using an analytical column packed with sub-2-microne particles. In multiple reaction monitoring mode, the detection limits ranged from 0.05 to 5 fmol and the linear ranges for most cytokinins were at least five orders of magnitude. The StageTip purification was validated and optimized using samples of Arabidopsis thaliana seedlings, roots and shoots where eighteen cytokinins were successfully determined.

CONCLUSIONS

The combination of microextraction with one-step high-throughput purification provides fast, effective and cheap sample preparation prior to qualitative and quantitative measurements. Our procedure can be used after modification also for other phytohormones, depending on selectivity, affinity and capacity of the selected sorbents.

Comparison of the quantification of a therapeutic protein using nominal and accurate mass MS/MS

Background: The quantification of proteins and peptides in in vivo samples is a critical part of supporting the drug development process for biotherapeutics. LC–MS/MS using tandem quadrupole mass spectrometers is well established as the technology of choice for the quantification of small-molecule drugs and their metabolites in biological fluid. The application of accurate mass MS for quantification in a DMPK environment has attracted considerable interest in recent years. Materials & Methods: In this article we describe and compare the application of LC–high-resolution MS and LC–selected reaction monitoring (SRM) for the quantification of a therapeutics proteins. Results: The accurate mass instrumentation showed acceptable linearity and sensitivity to quantify the protein therapeutic to the level of 10 ng/ml. The accurate mass instrument was operated in accurate mass SRM using high resolution (SRM-HR), the assay was demonstrated to be linear over three orders of magnitude. By narrowing the mass window from 100 mDa to 40 mDa and then to 20 mDa the assay specificity was significantly improved, hence increasing the S/N and improving the assay sensitivity. Conclusion: The high-resolution instrument was demonstrated to be reproducible over the course of the assay. The accurate mass method sensitivity was determined to be within one order of magnitude of that obtained with a tandem quadrupole MS/MS assay.

Addressing the challenge of limited sample volumes in in vitro studies with capillary-scale microfluidic LC–MS/MS

Miniaturization of chromatographic separation systems provides a means of greatly increasing sensitivity in LC–MS. In this article, we demonstrate the use of an integrated microfluidic chromatographic device for the LC–MS/MS investigation of the in vitro microsomal metabolism of the model drug propranolol using a sample volume of 1 µl of a 1-µM incubation. With such samples the system was capable of obtaining high-quality MS and MS/MS data from the injection of test drug substance containing sufficient information to correctly derive the structure of the drug metabolites. The analytical column was tolerant to the injection of a large percentage of organic solvent in the sample and still delivered a high-quality separation. The data suggest that these types of micro-LC–MS/MS devices are robust enough for routine applications and well suited to the analysis of small samples. Other potential applications include the generation of pharmacokinetic profiles from the reduced sample volumes obtained from serially bled small rodent studies, or the facilitation of analysis of limited-volume samples from neurological studies.

Pulsed multiple reaction monitoring approach to enhancing sensitivity of a tandem quadrupole mass spectrometer

Liquid chromatography (LC)-triple quadrupole mass spectrometers operating in a multiple reaction monitoring (MRM) mode are increasingly used for quantitative analysis of low-abundance analytes in highly complex biochemical matrixes. After development and selection of optimum MRM transitions, sensitivity and data quality limitations are largely related to mass spectral peak interferences from sample or matrix constituents and statistical limitations at low number of ions reaching the detector. Herein, we report on a new approach to enhancing MRM sensitivity by converting the continuous stream of ions from the ion source into a pulsed ion beam through the use of an ion funnel trap (IFT). Evaluation of the pulsed MRM approach was performed with a tryptic digest of Shewanella oneidensis strain MR-1 spiked with several model peptides. The sensitivity improvement observed with the IFT coupled in to the triple quadrupole instrument is based on several unique features. First, ion accumulation radio frequency (rf) ion trap facilitates improved droplet desolvation, which is manifested in the reduced background ion noise at the detector. Second, signal amplitude for a given transition is enhanced because of an order-of-magnitude increase in the ion charge density compared to a continuous mode of operation. Third, signal detection at the full duty cycle is obtained, as the trap use eliminates dead times between transitions, which are inevitable with continuous ion streams. In comparison with the conventional approach, the pulsed MRM signals showed 5-fold enhanced peak amplitude and 2-3-fold reduced chemical background, resulting in an improvement in the limit of detection (LOD) by a factor of ∼4-8.