Ultraperformance Liquid Chromatography–Tandem Mass Spectrometry Method for Profiling Ketolic and Phenolic Sex Steroids Using an Automated Injection Program Combined with Diverter Valve Switch and Step Analysis

Online Charge-Generation Derivatization by Electrochemical Radical Cations of Thianthrene: Mass Spectrometry Imaging of Estrogens in Biological Tissues

Estrogens play a significant role in endocrinology and oncology. Although separation methods coupled with mass spectrometry (MS) have emerged as a powerful tool for studying estrogens, imaging the spatial distributions of estrogens is crucial but remains challenging due to its low endogenous concentration and poor ionization efficiency. Charge-generation derivatization, such as N-alkylpyridinium quaternization and S-methyl thioetherification, represents a method wherein neutral molecules involving analytes and derivatization reagents undergo chemical reactions to establish permanent charges directly onto the analytes to improve detection sensitivity. Here, we developed a novel derivatization reagent, thianthrene (TT), which enabled oxidization to radical cations ([TT]•+) using an electrochemical method and completed the online charge-generation derivatization of estrogens on a mass spectrometry imaging platform. In this strategy, [TT]•+ can efficiently and selectively derivatize estrogens via an electrophilic aromatic substitution reaction. Results indicated that derivatization with [TT]•+ can significantly enhance imaging sensitivity (3 orders of magnitude), enabling the visualization of estrogen and its metabolites in ovarian and breast tissues. Furthermore, a higher mass intensity of these estrogens was captured in breast para-cancerous tissues than in cancerous tissues, which might provide estrogens spatial dimension information for further research on the initiation and progression of breast cancer.

Automated sample preparation with 6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate and iodoacetamide derivatization reagents for enantioselective liquid chromatography tandem mass spectrometry amino acid analysis

Enantioselective amino acid analysis is gaining increasing importance in pharmaceutical, biomedical and food sciences. While there are many methods available for enantiomer separation of amino acids, the simultaneous analysis of all chiral proteinogenic amino acids by a single method with one column and a single condition is still challenging. Herein, we report an enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS) assay using Chiralpak QN-AX as chiral column. With 6-aminoquinolyl-N-hydrosysuccinimidyl carbamate (AQC) as derivatization reagent, efficient enantioselective separation of D- and L-amino acids using HPLC has become possible. Thiol-containing amino acids like Cys are alkylated prior to AQC-labelling. A protocol for automated sample preparation including both derivatization step and calibrator preparation is presented. For compensating matrix effects, u-13C15N-labelled internal standards (IS) were employed. The method was validated and applied to the enantioselective analysis of amino acids in a bacterial fermentation broth.

Lithium ion adduction enables UPLC-MS/MS-based analysis of multi-class 3-hydroxyl group-containing keto-steroids

Steroids that contain a 3-hydroxyl group (3-OH steroids) are widely distributed in nature. During analysis with ESI-MS, they easily become dehydrated while in the protonated form, resulting in the production of several precursor ions and leading to low sensitivity of detection. To address this analytical challenge, here, we developed a method for the quantitation of 3-OH steroids by LC-MS/MS coupled with post-column addition of lithium (Li) ions to the mobile phase. The Li ion has a high affinity for the keto group of steroids, stabilizing their structures during ionization and permitting detection of analytes exclusively as the lithiated form. This not only improved the intensities of the precursor ions, but also promoted the formation of typical lithiated fragment ions. This improvement made the quantitation by multiple reaction monitoring more sensitive and reliable, as evidenced by 1.53-188 times enhanced detection sensitivity of 13 steroids that contained at least one keto and two hydroxyl groups or one keto and one 5-olefinic double bond, among 16 different 3-OH steroids. We deployed our newly developed method for profiling steroids in mouse brain tissue and identified six steroids in one tissue sample. Among these, 16-hydroxyestrone, tetrahydrocorticosterone, and 17α-hydroxypregnenolone were detected for the first time in the mouse brain. In summary, the method described here enables the detection of lithiated steroids by LC-MS/MS, including three 3-OH steroids not previously reported in the mouse brain. We anticipate that this new method may allow the determination of 3-OH steroids in different brain regions.

Detection of biogenic amines in pet food ingredients by RP-HPLC with automated dansyl chloride derivatization

The detection of biogenic amines is of significant interest to the food industry, as they can be used as indicators of food spoilage and they are potentially toxic. Because of their importance, there is a need for automated methods suitable for industry use that can detect a wide range of biogenic amines at sufficient levels for food analysis. In this work, optimized conditions for the automated determination of biogenic amines (histamine, putrescine, cadaverine, spermine, spermidine, tyramine, and tryptamine) derivatized with dansyl chloride are presented. Limits of detection below 0.2 ppm were achieved for seven biogenic amines and percentage recoveries were between 80 and 109% for the seven analytes spiked into meat meal samples. The method is simple and compared well to an existing method for the detection of biogenic amines in pet food ingredients.

Detection and Identification of Estrogen Based on Surface-Enhanced Resonance Raman Scattering (SERRS)

Many studies have shown that it is important to consider the harmful effects of phenolic hormones on the human body. Traditional UV detection has many limitations, so there is a need to develop new detection methods. We demonstrated a simple and rapid surface-enhanced resonance Raman scattering (SERRS) based detection method of trace amounts of phenolic estrogen. As a result of the coupling reaction, there is the formation of strong SERRS activity of azo compound. Therefore, the detection limits are as low as 0.2 × 10-4 for estrone (E1), estriol (E3), and bisphenol A (BPA). This method is universal because each SERRS fingerprint of the azo dyes a specific hormone. The use of this method is applicable for the testing of phenolic hormones through coupling reactions, and the investigation of other phenolic molecules. Therefore, this new method can be used for efficient detection.

Photochemical device for selective detection of phenol in aqueous solutions

We demonstrate that a lab-on-a-chip device (hereafter termed a photochemical phenol sensor) that integrates a photocatalytic long-period fiber grating (PLPFG), fiber Bragg grating (FBG), polymer membrane, ultraviolet (UV) visible light, and microchannels can be exploited to selectively detect phenol in aqueous solutions. The novel PLPFG consisted of a thinned long-period fiber grating (LPFG) and a UV-visible-light-driven Er3+:YAlO3/SiO2/TiO2 (EYST) coating. The polymer membrane with high phenol permselectivity was synthesized using PEBA2533 doped with β-cyclodextrin and was wrapped around the EYST surface, thus forming a microchannel between the membrane and PLPFG to enable the injection and outflow of standard analytes. Subsequently, a Z-shaped microchannel in a PMMA plate was fabricated and employed as a storage chamber for phenol analytes. To realize the EYST photocatalyst, UV-visible-light was irradiated using a tapered UV optical array. Thereafter, to eliminate the effect of temperature on the device, a FBG sensor as a temperature-compensating element was presented. To demonstrate the sensitivity and selectivity of the proposed device, we investigated the effects of the EYST coating's thickness, phenol-based analytes and temperature on the sensitivity and accuracy of the device for measuring phenol concentrations. The results of our present study suggest that the photochemical sensor is effective over a wide range of concentrations (7.5 μg L-1 to 100 mg L-1), pH values (2.0 to 14.0), and temperatures (10 to 48 °C) for selective detection of phenol in aqueous solutions. Thus, the proposed lab-on-a-chip device may be useful for accurate determination of phenol concentrations in real samples.

A sensitive approach for simultaneous quantification of carbonyl and hydroxyl steroids using 96-well SPE plates based on stable isotope coded-derivatization-UPLC-MRM: method development and application

Steroid hormones are crucial substances that mediate a wide range of vital physiological functions. Because of the important biological significance of steroids, this paper presents a new targeted metabolic method based on adding stable isotope tags to hydroxyl containing and carbonyl containing steroid hormones with two pairs of synthesized derivatization reagents: deuterium 4-(dimethylamino)-benzoic acid (D₄-DMBA), and D₅-Girard P (D₅-GP) using of ultra performance liquid chromatography-multiple reaction monitoring (UPLC-MRM). Firstly, an Oasis PRiME hydrophilic-lipophilic balance (HLB) 96-well solid phase extraction plate was used to pretreat a number of biological samples simultaneously. Secondly, hydroxyl and carbonyl steroids were labeled using two pairs of synthetic reagents, namely DMBA and D₄-DMBA, and GP and D₅-GP, respectively. Thirdly, the mixed products were detected using UPLC-MRM and the mass spectroscopy conditions were optimized. Methodology development showed that the sensitivity was enhanced 1 to >500-fold. Finally, the new method was applied to analysis of urine samples of healthy males, females and rats. The results revealed that the method can be sensitive and reliable for simultaneous quantification of steroid hormones containing hydroxyl and carbonyl groups in 12 min in a single run. This method provided a powerful tool for studying the metabolic mechanism of steroids and contributed to the development of targeted metabolomics.

Steroid hormones are crucial substances that mediate a wide range of vital physiological functions.

Quantitative profiling of carbonyl metabolites directly in crude biological extracts using chemoselective tagging and nanoESI-FTMS

The extensive range of chemical structures, wide range of abundances, and chemical instability of metabolites present in the metabolome pose major analytical challenges that are difficult to address with existing technologies. To address these issues, one approach is to target a subset of metabolites that share a functional group, such as ketones and aldehydes, using chemoselective tagging. Here we report a greatly improved chemoselective method for the quantitative analysis of hydrophilic and hydrophobic carbonyl-containing metabolites directly in biological samples. This method is based on direct tissue or cells extraction with simultaneous derivatization of stable and labile carbonylated metabolites using N-[2-(aminooxy)ethyl]-N,N-dimethyl-1-dodecylammonium (QDA) and 13CD3 labeled QDA. We combined innovations of direct quenching of biological sample with frozen derivatization conditions under the catalyst N,N-dimethyl-p-phenylenediamine, which facilitated the formation of oxime stable-isotope ion pairs differing by m/z 4.02188 while minimizing metabolite degradation. The resulting oximes were extracted by HyperSep C8 tips to remove interfering compounds, and the products were detected using nano-electrospray ionization interfaced with a Thermo Fusion mass spectrometer. The quaternary ammonium tagging greatly increased electrospray MS detection sensitivity and the signature ions pairs enabled simple identification of carbonyl compounds. The improved method showed the lower limits of quantification for carbonyl standards to be in the range of 0.20-2 nM, with linearity of R2 > 0.99 over 4 orders of magnitude. We have applied the method to assign 66 carbonyls in mouse tumor tissues, many of which could not be assigned solely by accurate mass and tandem MS. Fourteen of the metabolites were quantified using authentic standards. We also demonstrated the suitability of this method for determining 13C labeled isotopologues of carbonyl metabolites in 13C6-glucose-based stable isotope-resolved metabolomic (SIRM) studies.

Mass-spectrometry-based lipidomics

Lipids, which have a core function in energy storage, signalling and biofilm structures, play important roles in a variety of cellular processes because of the great diversity of their structural and physiochemical properties. Lipidomics is the large-scale profiling and quantification of biogenic lipid molecules, the comprehensive study of their pathways and the interpretation of their physiological significance based on analytical chemistry and statistical analysis. Lipidomics will not only provide insight into the physiological functions of lipid molecules but will also provide an approach to discovering important biomarkers for diagnosis or treatment of human diseases. Mass-spectrometry-based analytical techniques are currently the most widely used and most effective tools for lipid profiling and quantification. In this review, the field of mass-spectrometry-based lipidomics was discussed. Recent progress in all essential steps in lipidomics was carefully discussed in this review, including lipid extraction strategies, separation techniques and mass-spectrometry-based analytical and quantitative methods in lipidomics. We also focused on novel resolution strategies for difficult problems in determining C=C bond positions in lipidomics. Finally, new technologies that were developed in recent years including single-cell lipidomics, flux-based lipidomics and multiomics technologies were also reviewed.

Simultaneous determination of three estrogens in human saliva without derivatization or liquid-liquid extraction for routine testing via miniaturized solid phase extraction with LC-MS/MS detection

Accurate quantitation of estrogens (i.e, estrone (E1), estradiol (E2) and estriol (E3)) is valuable for clinical assessment of human health and disease. Alterations in estrogen levels have been implicated in numerous pathological conditions. However, inadequacies in sensitivity and specificity, cumbersome sample preparation and invasive specimen collection hamper the usability of available methods for clinical applications. Herein, a simple, rapid, highly sensitive and specific LC-MS/MS method was developed and validated for the simultaneous determination of three estrogens in human saliva providing a non-invasive alternative to conventional blood samples. For the first time, a 96-well hydrophilic-lipophilic-balanced (HLB) microplate was employed for clean-up and enrichment of estrogens in a single extraction without the requirements of derivatization, evaporation, liquid-liquid extraction and online extraction. A rapid LC chromatographic separation with a turnaround time of 5.0min was achieved on a BEH C18 XP column. The use of 0.1mM ammonium fluoride (NH₄F) as LC additive, and integration of summated and scheduled multiple reaction monitoring (MRM) transitions substantially improved the sensitivity to 1pg/mL, allowing the accurate quantitation of trace levels of three estrogens in one run. The assay was fully validated with good performance for extraction efficiency (67.0-85.6%), matrix effect (89.6-100.2%), linearity (from 1.0pg/mL up to 1000pg/mL), accuracy (98.9-112.4%) and precision (≤7.4%). Additionally, the assay was unaffected by 34 structurally-similar, potentially interfering substances tested at high clinical concentrations. The applicability of the assay was demonstrated by assessing the reference intervals of authentic saliva samples from healthy adult males, pre- and post-menopausal females. The easy sample preparation, fast LC and multi-analyte MS/MS detection utilizing noninvasive saliva as a specimen delivers a simple, practical, sensitive and accurate tool suitable for the high throughput measurement of E1, E2 and E3 in clinical laboratories.

A UHPLC-MS/MS method for profiling multifunctional steroids in human hair

It is important to profile steroids in many physiological and pathological processes. Recently, hair has been used for the long-term measurement of endogenous steroid hormones. Analyzing hair has advantages of being noninvasive and time sequential compared with other bio-specimens. Liquid chromatography-mass spectrometry (LC-MS) techniques have been widely used over the past decades; however, it is challenging to profile estrogens in hair by LC-MS, and more comprehensive steroid profiling is required. In this paper, an ultra high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed to simultaneously profile 28 multifunctional steroids, including corticosteroids (n = 6), estrogens (n = 13), androgens (n = 5) and progestogens (n = 4), in human scalp hair in a single run. To optimize the sample preparation procedure, we evaluated extraction time, post-incubation purification and hair fragment length; 30 mg hair samples were washed with hexane, cut into 5 mm pieces and incubated in methanol for 18 h at 25 °C. Methanol extraction derivatized using Girard P and dansyl chloride reagent was analyzed within 25 min using an automated injection program combined with a diverter valve switch and step analysis (AIDSA). The method was well validated in terms of linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, matrix effect and recovery, and was successfully applied to a steroid profile from male and female hairs. Significant differences were observed between genders. In addition, steroids showed a declining trend from the proximal to more distal hair segments; thus, care should be taken when obtaining hair samples for analysis to account for this difference in steroid levels along the length of hair. Graphical Abstract The workflow of the estabished UHPLC-MS/MS method.