Simple and accurate quantitative analysis of seven prohibited threshold substances in human urine by liquid chromatography/tandem mass spectrometry in doping control

Stepwise Frontal Analysis Coupled with Affinity Chromatography: A Fast and Reliable Method for Potential Ligand Isolation and Evaluation from Mahuang-Fuzi-Xixin Decoction

Mahuang-Fuzi-Xixin Decoction (MFXD) is widely used in the treatment of asthma, however, the functional components in the decoction targeting beta2-adrenoceptor (β₂ -AR) remain unclear. Herein, we immobilized the haloalkane dehalogenase (Halo)-tagged β₂ -AR on the 6-chlorocaproic acid-modified microspheres. Using the affinity stationary phase, the interactions of four ligands with the receptor were analyzed by stepwise frontal analysis. The association constants were (4.75±0.28)×10⁴  M^-1 for salbutamol, (2.93±0.15)×10⁴  M^-1 for terbutaline, (1.23±0.03)×10⁴  M^-1 for methoxyphenamine, (5.67±0.38)×10⁴  M^-1 for clorprenaline at high-affinity binding site, and (2.73±0.05)×10³  M^-1 at low-affinity binding site. These association constants showed the same rank order as the radioligand binding assay, demonstrating that immobilized β₂ -AR had capacity to screen bioactive compounds binding to the receptor while stepwise frontal analysis could predict their binding affinities. Application of the immobilized receptor in analysis of MFXD by chromatographic method revealed that ephedrine, aconifine, karakoline, and chasmanine were the bioactive compounds targeting β₂ -AR. Among them, ephedrine and chasmanine exhibited association constants of (2.94±0.02)×10⁴ M^-1 and (4.60±0.15)×10⁴  M^-1 to the receptor by stepwise frontal analysis. Molecular docking analysis demonstrated that ephedrine, chasmanine, and the other two compounds interact with β₂ -AR through the same pocket involving the key amino acids such as Asn312, Asp113, Phe289, Trp286, Tyr316, and Val114. As such, we reasoned that the four compounds dominate the therapeutic effect of MFXD against asthma through β₂ -AR mediating pathway. This work shed light on the potential of immobilized β₂ -AR for drug discovery and provided a valuable methodology for rapid screening.

Rapid and sensitive SERS detection of opioids in solutions based on the solid chip Au-coated Si nano-cone array

Rapid and flexible detection or accurate recognition of trace drugs is of great importance in cracking down on drug crimes, but it remains to be expected. Here, a solid chip is presented for the efficient detection and recognition of trace opioids (typically morphine) in aqueous solutions based on surface-enhanced Raman spectroscopy (SERS). Firstly, a Au-coated Si nano-cone array (Au-SNCA) is designed and fabricated via Si-based organic colloidal template etching and Au deposition. This Au-SNCA shows three-dimensional nanostructure with high densities of nanotips and deep nanogaps as well as high structural consistency, which exhibits strong SERS activity to morphine and outstanding stability. Then, such Au-SNCA is used as solid SERS chip to detect morphine in aqueous solutions. It has been demonstrated that using such solid chip, trace morphine in solutions could be recognized and detected within 1 min, and the detection limit is 10^-5 mg/mL (∼10 ppb), showing rapid and sensitive detection, which is much better than the previous reports. Meanwhile, the Au-SNCA chip also can be utilized to detect trace morphine in tap water and reservoir water, the recoveries range from 90.4% to 102.4%. Such excellent SERS performance of this Au-SNCA chip is attributed to its special structure which enhances not only local electromagnetic field but also molecular adsorption. The experimental results about the effects of immersion time and concentration show that the adsorption behavior of morphine molecules on such Au-SNCA chip can be explained by the pseudo-second-order kinetic model and Freundlich adsorption mode. Moreover, the Au-SNCA chip is also suitable for the identification of morphine homologues and the broad-spectrum detection of various common drugs. This study presents a practical solid chip and a simple approach for the efficient SERS detection and recognition of trace drugs in solutions. This is of significance to on-site detect drugs in forensic science.

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.

Urinary profiling of tryptophan and its related metabolites in patients with metabolic syndrome by liquid chromatography-electrospray ionization/mass spectrometry

Tryptophan (Trp) is an essential amino acid that plays an important role in protein synthesis and is a precursor of various substances related to diverse biological functions. An imbalance in Trp metabolites is associated with inflammatory diseases. The accurate and precise measurement of these compounds in biological specimens would provide meaningful information for understanding the biochemical states of various metabolic syndrome-related diseases, such as hyperlipidemia, hypertension, diabetes, and obesity. In this study, we developed a rapid, accurate, and sensitive liquid chromatography-tandem mass spectrometry-based method for the simultaneous targeted analysis of Trp and its related metabolites of the kynurenine (Kyn), serotonin, and tryptamine pathways in urine. The application of the developed method was tested using urine samples after protein precipitation. The detection limits of Trp and its metabolites were in the range of 0.01 to 0.1 μg/mL. The method was successfully validated and applied to urine samples from controls and patients with metabolic syndrome. Our results revealed high concentrations of Kyn, kynurenic acid, xanthurenic acid, and quinolinic acid as well as a high Kyn-to-Trp ratio (KTR) in patients with metabolic syndromes. The levels of urine Kyn and KTR were significantly increased in patients under 60 years old. The profiling of urinary Trp metabolites could be a useful indicator for age-related diseases including metabolic syndrome. ᅟ.

Applications and challenges in using LC–MS/MS assays for quantitative doping analysis

LC–MS/MS is useful for qualitative and quantitative analysis of ‘doped’ biological samples from athletes. LC–MS/MS-based assays at low-mass resolution allow fast and sensitive screening and quantification of targeted analytes that are based on preselected diagnostic precursor–product ion pairs. Whereas LC coupled with high-resolution/high-accuracy MS can be used for identification and quantification, both have advantages and challenges for routine analysis. Here, we review the literature regarding various quantification methods for measuring prohibited substances in athletes as they pertain to World Anti-Doping Agency regulations.

Bioanalytical techniques in discrimination between therapeutic and abusive use of drugs in sport

The discrimination between therapeutic and abusive use of drugs in sports is performed using threshold concentrations or reporting levels, and the detection of the substances in a sample is only reported as an adverse analytical finding when the concentration exceeds the threshold or the reporting level. In this paper, the strategies of discrimination and the analytical methods used for the main groups of substances where the distinction is needed (β-2 agonists, ephedrines, glucocorticoids and morphine) will be reviewed. Nowadays, LC–MS is the method of choice for the analysis of these substances and, in most of the cases, a simple dilution of the urine sample is performed before the chromatographic analysis.

Simultaneous analysis of 210 prohibited substances in human urine by ultrafast liquid chromatography/tandem mass spectrometry in doping control

RATIONALE

Doping analysis is a two-step process consisting of a screening step for prohibited substances and a confirmation step to verify the presence of specific substances found during the screening. The entire process must be performed within a limited time period, but traditional screening procedures commonly employ separate analytical methods for each class of prohibited substances being screened and thus require a great deal of human resources and instrumentation. A single simple and rapid multiresidue analytical method that could accommodate multiple classes of prohibited substances would be extraordinarily useful in doping analyses.

METHODS

Urine samples were extracted via two consecutive liquid-liquid extractions at different pH values following enzymatic hydrolysis. Analyses were performed by ultrafast liquid chromatography/triple-quadrupole mass spectrometry with polarity switching and time-dependent selected reaction monitoring.

RESULTS

We developed a rapid multiresidue screening and confirmation method for efficient high-throughput doping analyses. The present method was validated with regard to the limits of detection (0.01-100.0 ng/mL for screening analyses and 0.2-500.0 ng/mL for confirmation assays), matrix effects (48.9-118.9%), recovery (20.6-119.7%) and intra- (0.6-17.6%) and inter-day (4.0-20.0%) precision.

CONCLUSIONS

A multiresidue analytical method was developed and validated for screening and confirming the presence of performance-enhancing drugs. A total of 210 substances from diverse classes of prohibited substances were successfully identified with an analytical run time of 10 min.