Determination of Vasopressin and Desmopressin in urine by means of liquid chromatography coupled to quadrupole time-of-flight mass spectrometry for doping control purposes

Elucidating important factors and corresponding method optimization for sensitive detection of small peptide drugs in human urine by solid-phase extraction and UPLC-HRMS: The influence of MS scan modes, protein precipitants, and ammonium formate

Small peptide hormones are widely used in sports as performance-enhancing substances, making it crucial to develop sensitive analytical methods for their detection in doping control analysis. Various factors significantly affect analytical sensitivity, such as the selection of ultra-performance liquid chromatography (UPLC) mobile phase, high-resolution mass spectrometry (HRMS) scanning modes, and extraction solvents for pretreatment. Herein, comparative study approach was utilized to investigate the sensitivity of each peptide analyte under both full scan and parallel reaction monitoring (PRM) modes of HRMS and assess the effects of some protein precipitants as a part of extraction solvents on solid-phase extraction (SPE). The results showed that full scan should be selected as the primary scan mode of HRMS, and the combination with PRM mode could effectively compensate for the limitations of full scan, and the addition of protein precipitants would adversely affect the detection of certain small peptide analytes. Meanwhile, influences of ammonium formate in reverse UPLC mobile phase on the charge state distribution of small peptides were investigated and elucidated. Based on these findings, a sensitive and reliable UPLC-HRMS analytical method combining full scan and PRM mode was validated for screening and confirmation of 63 small peptide analytes after SPE, with limits of detection (LODs) ranging between 0.010 and 0.473 ng/ml and limits of identification (LOIs) ranging between 0.015 and 1.512 ng/ml. Additionally, suggestions were provided for the detection of [Arg8]-vasopressin, dermorphin, and its analogues.

Gradient Retention Factor Concept Applied to Method Development for Peptide Analysis by Means of RP-HPLC

Using the van Deemter model, the efficiency of three stationary phase systems in the analysis of a mixture of synthetic peptides was evaluated: (i) monolithic, (ii) packed, and (iii) core-shell columns, and it was shown that the efficiency of the monolithic column is superior to the others, specifically using it, the lowest values of H _min (0.03 and 0.1 mm) were obtained, and additionally its efficiency was not significantly affected by increasing the flow. Using the concept of the gradient retention factor (k*), a method for chromatographic separation of a peptide complex mixture was designed, implemented, and optimized and then transferred from a packed column to a monolithic one. The results showed that it was possible to separate all components of the mixture using both evaluated columns; moreover, the analysis time was reduced from 70 to 10 min, conserving the critical pair resolution (1.4), by the transfer method using the k* concept. The method developed was tested against a mixture of doping peptides, showing that this method is efficient for separating peptides of various natures. This investigation is very useful for the development of methods for the analysis of complex peptide mixtures since it provides a systematic approach that can be extrapolated to different types of columns and instrumentation.

Synthetic Peptides in Doping Control: A Powerful Tool for an Analytical Challenge

Peptides are very diverse molecules that can participate in a wide variety of biological processes. In this way, peptides are attractive for doping, since these molecules can activate or trigger biological processes that can improve the sports performance of athletes. Peptide molecules are found in the official World Anti-Doping Agency lists, mainly in sections S2, S4, and S5. In most cases, these molecules have a very short half-life in the body and/or are identical to natural molecules in the body, making it difficult to analyze them as performance-enhancing drugs. This article reviews the role of peptides in doping, with special emphasis on the peptides used as reference materials, the pretreatment of samples in biological matrices, the instrumentation, and the validation of analytical methodologies for the analysis of peptides used in doping. The growing need to characterize and quantify these molecules, especially in complex biological matrices, has generated the need to search for robust strategies that allow for obtaining sensitive and conclusive results. In this sense, strategies such as solid phase peptide synthesis (SPPS), seeking to obtain specific peptides, metabolites, or isotopically labeled analogs, is a key tool for adequate quantification of different peptide molecules in biological matrices. This, together with the use of optimal methodologies for sample pretreatment (e.g., SPE or protein precipitation), and for subsequent analysis by high-resolution techniques (mainly hyphenated LC-HRMS techniques), have become the preferred instrumentation to meet the analytical challenge involved in the analysis of peptides in complex matrices.

Detection of insulin analogues and large peptides > 2 kDa in urine

Insulin analogues and large bioactive peptides may be used by athletes to enhance performance and are banned by the World Anti-Doping Agency (WADA). In addition to insulin analogues, the large peptides include a structurally diverse set of peptides including analogues of growth hormone releasing hormone (GHRH), insulin-like growth factor-1 (IGF-1), and mechano-growth factor (MGF). Detection of this class of peptides is difficult due to their absorptive losses and presence at very low concentrations in urine. In this report, a high throughput method is described that allows sensitive detection of 4 classes of large peptides in one assay. Sample extraction is performed by ultrafiltration to concentrate the urine followed by solid phase extraction in a 96-well micro-elution plate. Peptides in the urine samples are detected on a triple quadrupole mass spectrometer coupled to standard flow liquid chromatography. The method was validated and evaluated for limit of detection, limit of identification, specificity, precision, carry-over, recovery, matrix interference, and post-extraction stability. The limit of detection for insulin analogues is between 5 - 25 pg/ml and between 5 - 50 pg/ml for the other peptide classes. Specificity was good with no detection of interfering peaks in blank urine samples. Carry-over from a high concentration sample was not observed and the post-extraction stability was between 77 - 107%. The method was able to detect insulin analogues in three diabetic urine samples. Increased screening for this class of peptides will improve detection and deterrence.

Doping control analysis of small peptides in human urine using LC-HRMS with parallel reaction monitoring mode: screening and confirmation

This study described a reliable analytical method, which combines solid-phase extraction (SPE) with liquid chromatography-high resolution mass spectrometry (LC-HRMS) employing the parallel reaction monitoring (PRM) mode, for screening 41 small peptides and 3 non-peptide growth hormone secretagogues in human urine. Additionally 36 small peptides and 3 non-peptide growth hormone secretagogues were also confirmed in the same way. For the whole screening procedure, the PRM mode was applied to the HRMS detection of small peptides, which reduces the background noise from matrix compounds to a large extent and thus improves the selectivity and reliability of the peptide analytes. Meanwhile, competent chromatographic separation was achieved within a total runtime of 14 minutes, indicating an improvement in the detection efficiency. Moreover, the PRM mode could also be applied to the confirmation procedure due to its strong identification power with a low risk of generating false positives or negatives and good selectivity. Validation was performed according to the relevant World Anti-Doping Agency (WADA) criteria, including selectivity and reliability, limit of detection (LOD), limit of identification (LOI), recovery, extraction stability and carryover. The LODs of the peptide analytes ranged between 0.20 ng mL^-1 and 0.92 ng mL^-1 in urine, while their LOIs ranged between 0.20 ng mL^-1 and 2.00 ng mL^-1, which met the corresponding Minimum Required Performance Levels (MRPLs) as defined by WADA. The developed method furnished the rapid and sensitive detection of small peptides in urine for more than 5000 samples with no false-positive or false-negative, indicating that it is an eligible method for doping control analysis.

Enhanced urinary stability of peptide hormones and growth factors by dried urine microsampling

Volumetric absorptive microsampling (VAMS) and dried urine spot (DUS) strategies were applied for the collection of dried microsamples for anti-doping testing of low-stability peptide hormones and growth factors prohibited by the World Anti-Doping Agency (WADA). Drying, storage and transport conditions, as well as pretreatment steps, were optimised before liquid chromatography - tandem mass spectrometry (LC-MS/MS) analysis. The analytical method has been fully validated in terms of sensitivity (limits of quantitation 0.3-10 ng/mL), precision (RSD% < 6.6 %) and extraction yields (78-91 %). Dried microsample stability studies (90 days) have been performed and compared to fluid urine stability. Significantly higher losses have been observed in fluid urine stored at -20 °C (up to 55 %) and -80 °C (up to 29 %) than in dried urine microsamples stored at room temperature (< 19 %). The final microsampling and analysis protocols allow the collection of urine microvolumes, unlikely to be tampered, stably storable and shippable with no particular precautions for possible anti-doping testing of prohibited peptides and hormones.

A target-driven DNA-based molecular machine for rapid and homogeneous detection of arginine-vasopressin

Rapid detection of physiological changes of neuropeptides is of great importance as they are involved in a wide range of physiological processes and behaviors. Abnormalities in their expression level are correlated with various neurological diseases. However, current methods such as radioimmunoassay, enzyme-linked immunosorbent assays and liquid chromatography tandem mass spectrometry relied on cumbersome operation steps and could not rapidly provide the information of their concentration fluctuations. Thus motivated, we developed a target-driven DNA-based molecular machine that could be triggered only in the presence of a specific target neuropeptide. Using arginine-vasopressin (AVP) as a model neuropeptide, we integrated the DNA-based molecular machine with fluorescence signal transduction and amplification technology. The assay was rapid and homogeneous, which offered a linear range of 75-700 pM and a limit-of-detection as low as 75 pM. It holds great potential for further applications in real-time monitoring of the variations of the AVP level in biological samples.

Fully automated dried blood spot sample preparation enables the detection of lower molecular mass peptide and non-peptide doping agents by means of LC-HRMS

The added value of dried blood spot (DBS) samples complementing the information obtained from commonly routine doping control matrices is continuously increasing in sports drug testing. In this project, a robotic-assisted non-destructive hematocrit measurement from dried blood spots by near-infrared spectroscopy followed by a fully automated sample preparation including strong cation exchange solid-phase extraction and evaporation enabled the detection of 46 lower molecular mass (< 2 kDa) peptide and non-peptide drugs and drug candidates by means of LC-HRMS. The target analytes included, amongst others, agonists of the gonadotropin-releasing hormone receptor, the ghrelin receptor, the human growth hormone receptor, and the antidiuretic hormone receptor. Furthermore, several glycine derivatives of growth hormone–releasing peptides (GHRPs), arguably designed to undermine current anti-doping testing approaches, were implemented to the presented detection method. The initial testing assay was validated according to the World Anti-Doping Agency guidelines with estimated LODs between 0.5 and 20 ng/mL. As a proof of concept, authentic post-administration specimens containing GHRP-2 and GHRP-6 were successfully analyzed. Furthermore, DBS obtained from a sampling device operating with microneedles for blood collection from the upper arm were analyzed and the matrix was cross-validated for selected parameters. The introduction of the hematocrit measurement method can be of great value for doping analysis as it allows for quantitative DBS applications by managing the well-recognized “hematocrit effect.”

GC-MS and LC-MS/MS pilot studies on the guanidine (NG)-dimethylation in native, asymmetrically and symmetrically NG-dimethylated arginine-vasopressin peptides and proteins in human red blood cells

Protein-arginine methyltransferases catalyze the methylation of the guanidine (N^G) group of proteinic L-arginine (Arg) to produce monomethyl and dimethylarginine proteins. Their proteolysis releases the free amino acids monomethylarginine (MMA), symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA), respectively. MMA, SDMA and ADMA are inhibitors of the nitric oxide synthase (NOS) activity. High circulating and low urinary concentrations of ADMA and SDMA are considered risk factors in the cardiovascular and renal systems, mainly due to their inhibitory action on NOS activity. Identity, biological activity and concentration of N^G-methylated proteins are largely unknown. The present study addressed these issues by using GC-MS and LC-MS/MS approaches. GC-MS was used to quantify free ADMA released by classical HCl-catalyzed hydrolysis of three synthetic Arg-vasopressin (V) peptides and of unknown endogenous N^G-dimethylated proteins. The cyclic (c) disulfide forms of Arg-vasopressin analogs, i.e., Arg-vasopressin (cV-Arg-Gly-NH₂), asymmetrically N^G-dimethylated vasopressin (cV-ADMA-Gly-NH₂) and symmetrically N^G-dimethylated vasopressin (cV-SDMA-Gly-NH₂) were used as model peptides in quantitative GC-MS analyses of ADMA, SDMA and other expected amino acids from the hydrolyzed Arg-vasopressin analogs. cV-ADMA-Gly-NH₂ and cV-SDMA-Gly-NH₂ were discriminated from cV-Arg-Gly-NH₂ by LC-MS and LC-MS/MS, yet they were indistinguishable from each other. The same applies to the respective open (o) reduced and di-S-acetamide forms of oV-ADMA-Gly-NH₂, oV-SDMA-Gly-NH₂ and oV-Arg-Gly-NH₂. Our LC-MS and LC-MS/MS studies suggest that the Arg-vasopressin analogs form [(M-H)]⁺ and [(M-H)+H]⁺ in the positive ESI mode and undergo in part conversion of their terminal Gly-NH₂ (NH₂, 16 Da) group to Gly-OH (OH, 17 Da). The product ion mass spectra of the di-S-acetamide forms are complex and contain several intense mass fragments differing by 1 Da. cV-ADMA-Gly-NH₂ and cV-SDMA-Gly-NH₂ induced platelet aggregation in platelet-rich human plasma with moderately different initial velocity and maximal aggregation rates compared to cV-Arg-Gly-NH₂. Previous studies showed that human red blood cells are rich in large (>50 kDa) ADMA-containing proteins of unknown identity. Our LC-MS/MS proteomic study identified several membrane and cytosolic erythrocytic N^G-dimethylated proteins, including spectrin-α (280 kDa), spectrin-β (247 kDa) and protein 4.1 (80 kDa). Being responsible for the stability of the erythrocyte membrane, the newly identified main targets for N^G-dimethylation in human erythrocytes should be given a closer look in erythrocytic diseases like hereditary spherocytosis.

An Intact ACTH LC-MS/MS Assay as an Arbiter of Clinically Discordant Immunoassay Results

BACKGROUND

Measurement of plasma adrenocorticotropic hormone (ACTH) is key in the differential diagnosis of hypothalamic-pituitary-adrenal disorders. Two-site sandwich immunoassays dominate clinical testing of ACTH in North America; however, discordant results between manufacturers have been repeatedly reported. To resolve the discrepancy, we developed a liquid chromatography–tandem mass spectrometry (LC-MS/MS) assay for the intended measurand, biologically active intact ACTH (iACTH).

METHODS

The multiple reaction monitoring LC-MS/MS assay was designed to selectively measure full-length iACTH, as well as ACTH analogs and fragments (i.e., ACTH1–24 and ACTH18–39). Epitope assignment of the Roche Elecsys antibodies was performed by MALDI-TOF mass spectrometry. A method comparison between Roche Elecsys and Siemens Immulite ACTH immunoassays was performed and clinically concordant/discordant results identified. In a subset of these samples, the iACTH concentration was determined using the LC-MS/MS method.

RESULTS

The lower limit of the measuring interval of the iACTH LC-MS/MS assay was 9 pg/mL (2 pmol/L). The assay was linear from 9 to 1938 pg/mL (2 to 427 pmol/L). Epitope mapping revealed that the Roche capture and detection antibodies bound residues 9–12 and 36–39 of ACTH, respectively. The iACTH LC-MS/MS analysis demonstrated that for discordant results between 2 immunoassays studied, only the Roche results were highly positively correlated with the iACTH concentration.

CONCLUSIONS

Immunoprecipitation of biologically active ACTH molecules followed by LC-MS/MS analysis enabled selective detection of iACTH and relevant biologically active fragments in plasma. Applied to the investigation of clinically discrepant results, this method can act as an arbiter of the concentration of iACTH present.

Development of a multi-functional concurrent assay using weak cation-exchange solid-phase extraction (WCX-SPE) and reconstitution with a diluted sample aliquot for anti-doping analysis

RATIONALE

In addition to the development of adequate screening methods for multiple compounds, the World Anti-Doping Agency (WADA) requires anti-doping laboratories to analyze prohibited substances and their metabolites from various classes. This task presents a difficult challenge for all agencies and interests involved in the field of doping control.

METHODS

A screening method is reported in which hybrid sample preparation was performed using a combination of weak cation-exchange solid-phase extraction (WCX-SPE) and the 'Dilute and Shoot' strategy in order to take advantage of both the methodologies. Target substances were extracted using a WCX cartridge and reconstituted with a diluted sample aliquot that included 20% of an untreated urine sample. The target substances were further analyzed by high-performance liquid chromatography/triple quadrupole mass spectrometry (LC/MS).

RESULTS

The SPE procedure was optimized using a cartridge-washing step, elution conditions, and elution volume. The cartridge-washing step, which was performed using 10% methanol, improved the overall recovery of target substances. Since the recovery was observed to vary according to the pH of the eluting solution, we applied an elution step using both an acid and a basic organic solvent to achieve complementary recovery. Reconstitution of the diluted aliquot sample was performed to recover the polar substances.

CONCLUSIONS

The method was validated and applied to real samples in accordance with the external quality assessment scheme of WADA and to the previously reported samples that had provided positive test results. This novel method using hybrid sample preparation and LC/MS could be useful to screen multiple classes of the 264 targeted substances in anti-doping analysis.

Highly sensitive assay for the determination of therapeutic peptide desmopressin in human plasma by UPLC-MS/MS

An analytical method based on ultra-performance liquid chromatography with positive ion electrospray ionization (ESI) coupled with tandem mass spectrometry detection (UPLC–MS/MS) was developed and validated for the determination of therapeutic peptide desmopressin in human plasma. A desmopressin stable labeled isotope (desmopressin d₈) was used as an internal standard. Analyte and the internal standard were extracted from 200 µL of human plasma via solid-phase extraction technique using Oasis WCX cartridges. The chromatographic separation was achieved on an Aquity UPLC HSS T3 column by using a gradient mixture of methanol and 1 mM ammonium formate buffer as the mobile phase. The calibration curve obtained was linear (r²≥0.99) over the concentration range of 1.01–200 pg/mL. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. The proposed method was successfully applied to pharmacokinetic studies in humans.

Assay of Desmopressin Acetate in Nasal Spray: Development of Validated Pre Column HPLC-Fluorescence Method

Purpose: Desmopressin acetate (DDAPV), a synthetic analogue of vasopressin, has been recommended to be used in diabetes insipidus, mild forms of hemophilia and Von Willebrand disease. The DDAPV is available for adminstration via different routes viz. oral, parenteral and nasal, however its dose is very less in case of nasal sprays (20 µg) and parenteral route (4 µg) compared to oral route (0.1 to 0.3 mg in tablet). A sensitive and selective method is needed to be developed and validated for assay of low concentrations of DDAPV in its pharmaceutical dosage form i.e. nasal spray.

Methods: Simple and specific HPLC-Fluorescecne method has been proposed for the quantitation of DDAPV at nanogram level in nasal formulations for the first time. DAPV, DDAPV EP impurity-B, chlorobutanol, benzalkonoium chloride were successfully derivatised with Ortho-Phthalaldehyde (OPA) and co-eluted on a C8 (50×2.1 mm, 3.5 µm particle size, 120Å) with mobile phase composed of 0.1% trifluroacetic acid, acetonitrile and Isopropyl alcohol in ratio of 70:25:5. The emission was measured at 450nm and flow rate was 0.8ml/min. The reaction was optimized in the terms of pH, stability of formed fluorophore and time consumed during the reaction.

Results: The maximal fluorescence intensity was reached when the solutions were mixed for 3 min, and remained constant for at least 30 min at 20-25ºC. The calibration curve was found linear from 50 to 5000 ng/ml with weight of 1/X². The limit of detection was 10ng/ml and precision was less than 2.0.

Conclusion: The developed HPLC-fluorescence assay method was successfully applied for quantitation of DDAPV in nasal spray. HPLC-Fluorescence method was specific, sensitive, precise and accurate for determination of DDAPV. The method was able to quantify DDAPV at 50ng/ml with sufficient accuracy and precision. The validated HPLC-Fluorescence was successfully applied.

Simplifying and expanding analytical capabilities for various classes of doping agents by means of direct urine injection high performance liquid chromatography high resolution/high accuracy mass spectrometry

So far, in sports drug testing compounds of different classes are processed and measured using different screening procedures. The constantly increasing number of samples in doping analysis, as well as the large number of substances with doping related, pharmacological effects require the development of even more powerful assays than those already employed in sports drug testing, indispensably with reduced sample preparation procedures. The analysis of native urine samples after direct injection provides a promising analytical approach, which thereby possesses a broad applicability to many different compounds and their metabolites, without a time-consuming sample preparation. In this study, a novel multi-target approach based on liquid chromatography and high resolution/high accuracy mass spectrometry is presented to screen for more than 200 analytes of various classes of doping agents far below the required detection limits in sports drug testing. Here, classic groups of drugs as diuretics, stimulants, β₂-agonists, narcotics and anabolic androgenic steroids as well as various newer target compounds like hypoxia-inducible factor (HIF) stabilizers, selective androgen receptor modulators (SARMs), selective estrogen receptor modulators (SERMs), plasma volume expanders and other doping related compounds, listed in the 2016 WADA prohibited list were implemented. As a main achievement, growth hormone releasing peptides could be implemented, which chemically belong to the group of small peptides (<2kDa) and are commonly determined by laborious and time-consuming stand-alone assays. The assay was fully validated for qualitative purposes considering the parameters specificity, robustness (rRT: <2%), intra- (CV: 1.7-18.4 %) and inter-day precision (CV: 2.3-18.3%) at three concentration levels, linearity (R²>0.99), limit of detection (0.1-25ng/mL; 3'OH-stanozolol glucuronide: 50pg/mL; dextran/HES: 10μg/mL) and matrix effects.

Identification and comparative oridonin metabolism in different species liver microsomes by using UPLC-Triple-TOF-MS/MS and PCA

Oridonin (ORI) is an active natural ent-kaurene diterpenoid ingredient with notable anti-cancer and anti-inflammation activities. Currently, a strategy was developed to identify metabolites and to assess the metabolic profiles of ORI in vitro using ultra-high-performance liquid chromatography-Triple/time-of-flight mass spectrometry (UPLC-Triple-TOF-MS/MS). Meanwhile, the metabolism differences of ORI in the liver microsomes of four different species were investigated using a principal component analysis (PCA) based on the metabolite absolute peak area values as the variables. Based on the proposed methods, 27 metabolites were structurally characterized. The results indicate that ORI is universally metabolized in vitro, and the metabolic pathway mainly includes dehydration, hydroxylation, di-hydroxylation, hydrogenation, decarboxylation, and ketone formation. Overall, there are obvious inter-species differences in types and amounts of ORI metabolites in the four species. These results will provide basic data for future pharmacological and toxicological studies of ORI and for other ent-kauranes diterpenoids. Meanwhile, studying the ORI metabolic differences helps to select the proper animal model for further pharmacology and toxicological assessment.

Structural characterization of arginine-vasopressin and lysine-vasopressin by Fourier- transform ion cyclotron resonance mass spectrometry and infrared multiphoton dissociation

Arginine-vasopressin (AVP) and lysine-vasopressin (LVP) were analyzed by reversed-phase liquid chromatography/mass spectrometry (LC-MS) using Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) electrospray ionization (ESI) in the positive ion mode. LVP and AVP exhibited the protonated adduct [M+H](+) as the predominant ion at m/z 1056.43965 and at m/z 1084.44561, respectively. Infrared multiphoton dissociation (IRMPD), using a CO(2) laser source at a wavelength of 10.6 μm, was applied to protonated vasopressin molecules. The IRMPD mass spectra presented abundant mass fragments essential for a complete structural information. Several fragment ions, shared between two target molecules, are discussed in detail. Some previously unpublished fragments were identified unambiguously utilizing the high resolution and accurate mass information provided by the FT-ICR mass spectrometer. The opening of the disulfide loop and the cleavage of the peptide bonds within the ring were observed even under low-energy fragmentation conditions. Coupling the high-performance FT-ICR mass spectrometer with IRMPD as a contemporary fragmentation technique proved to be very promising for the structural characterization of vasopressin.

LC–MS/MS in endocrinology: what is the profit of the last 5 years?

Currently, chromatography (GC but more commonly HPLC) is the analytical method of choice for several hormones, either because the immunoassays suffer from extensive crossreactivity or because chromatography permits simultaneous measurements of hormones. However, sometimes the conventional detection systems with HPLC methods do not meet desired specificity. With the increase of robust and affordable LC–MS/MS systems, the next step forward in specificity was taken. LC–MS/MS is rapidly being incorporated in the endocrine laboratories. To be useful in the clinical diagnostic practice, it is of utmost importance that methods are both analytically and clinically vaidated, as until now, the majority of applications of LC–MS/MS in the clinical laboratories are ‘home-made’ methods, therefore special case must be taken. This review aims to focus on Clinical and Laboratory Standards Institute or comparable validated LC–MS/MS methods for targeted hormone analysis used for diagnostic purposes in human samples, published in the last 5 years.

Large-molecule quantification: sensitivity and selectivity head-to-head comparison of triple quadrupole with Q-TOF

Background: Bioanalysts are continuously looking for innovative ideas or instruments to increase the sensitivity and selectivity of their assays. Research for better mass spectrometers is becoming crucial with the emerging trend of large-molecule quantification. This study lists the different advantages of high-resolution MS (HRMS) over standard triple quadrupole instruments and proposes basic guidelines on how to use HRMS for large-molecule quantification in a regulated environment. Results: A direct comparison between HRMS and triple quadrupole instruments for the quantification of six different model peptides (desmopressin, calcitonin, enfuvirtide, exenatide, glucagon and somatostatin) was completed. The HRMS instrument, when used specifically for targeted quantification (‘quant/quant’), showed equivalent or better sensitivity for all compounds tested. Conclusion: This paper demonstrates that the use of a HRMS instrument in a regulated environment is a viable technique for quantification of large molecules. The latter was able to allow flexibility and selectivity to adapt the specificity of each assay with sensitivity comparable to the triple quadrupole instrument.

Analytical challenges in the detection of peptide hormones for anti-doping purposes

Although significant progress has been achieved during the past few years with the introduction of new assays and analytical methodologies, the detection and quantification of protein analytes, in particular of peptide hormones, continues to pose analytical challenges for the World Anti-Doping Agency-accredited anti-doping laboratories. In this article, the latest achievements in the application of MS-based methodologies and specific biochemical and immunological assays to detect some of the prohibited substances listed in section S2 of the World Anti-Doping Agency List of Prohibited Substances and Methods are reviewed. In addition, we look towards the future by focusing on some of the most promising analytical approaches under development for the detection of so-called ‘biomarkers of doping’.