Screening Procedure for Detection of Diuretics and Uricosurics and/or Their Metabolites in Human Urine Using Gas Chromatography-Mass Spectrometry After Extractive Methylation

Reliable quantitative detection of uric acid in urine by surface-enhanced Raman spectroscopy with endogenous internal standard

Abnormal levels of uric acid (UA) in urine serve as warning signs for gout and metabolic cardiovascular diseases, necessitating the monitoring of UA levels for early prevention. However, the current analytical methods employed suffer from limitations in terms of inadequate suitability for home-based applications and the requirement of non-invasive procedures. In this approach, creatinine, a metabolite with a constant excretion rate, was incorporated as an endogenous internal standard (e-IS) for calibration, presenting a rapid, pretreatment-free, and accurate strategy for quantitative determination of UA concentrations. By utilizing urine creatinine as an internal reference value to calibrate the signal fluctuation of surface-enhanced Raman spectroscopy (SERS) of UA, the quantitative accuracy can be significantly improved without the need for an external internal standard. Due to the influence of the medium, UA, which carries a negative charge, is selectively adsorbed by Au@Ag nanoparticles functionalized with hexadecyltrimethylammonium chloride (CTAC) in this system. Furthermore, a highly convenient detection method was developed, which eliminates the need for pre-processing and minimizes matrix interference by simple dilution. The method was applied to the urine detection of different volunteers, and the results were highly consistent with those obtained using the UA colorimetric kit (UACK). The detection time of SERS was only 30 s, which is 50 times faster than UACK. This quantitative strategy of using urinary creatinine as an internal standard to correct the SERS intensity of uric acid is also expected to be extended to the quantitative detection needs of other biomarkers in urine.

Development and validation of a fast ultra-high-performance liquid chromatography tandem mass spectrometry method for determining carbonic anhydrase inhibitors and their metabolites in urine and hair

A new, rapid, sensitive, and comprehensive ultra‐high‐performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS) method for quantifying diuretics (acetazolamide, brinzolamide, dorzolamide, and their metabolites) in human urine and hair was developed and fully validated. Twenty‐five milligrams of hair were incubated with 500‐μl M3® buffer reagent at 100°C for 1 h for complete digestion. After cooling, 1‐μl supernatant was injected onto chromatography system. Urine samples were simply diluted before injection. The chromatographic run time was short (8 min) through a column with a mobile phase gradient. The method was linear (determination coefficients always higher than 0.99) from limit of quantification (LOQ) to 500 ng/ml in urine and from LOQ to 10 ng/mg in hair. LOQs ranged from 0.07 to 1.16 ng/ml in urine and from 0.02 to 0.15 ng/mg in hair. No significant ion suppression due to matrix effect was observed, and process efficiency was always higher than 80%. Intra‐ and inter‐assay precision was lower than 15%. The suitability of the methods was tested with six urine and hair specimens from patients treated with acetazolamide, dorzolamide, or brinzolamide for ocular diseases or systemic hypertension. Average urine concentrations were 266.32 ng/ml for dorzolamide and 47.61 ng/ml for N‐deethyl‐dorzolamide (n = 3), 109.27 ng/ml for brinzolamide and 1.02 ng/ml for O‐desmethyl‐brinzolamide (n = 2), and finally, 12.63 ng/ml for acetazolamide. Average hair concentrations were 5.94 ng/mg for dorzolamide and 0.048 ng/mg for N‐deethyl‐dorzolamide (n = 3), 3.26 ng/mg for brinzolamide (n = 2), and 2.3 ng/mg for acetazolamide (n = 1). The developed method was simple and fast both in the extraction procedures making it eligible in high‐throughput analysis for clinical forensic and doping purposes.

Method Optimization: Analysis of Benzbromarone and Tolfenamic Acid in Citrus Tissues and Soil Using Liquid Chromatography Coupled With Triple-Quadrupole Mass Spectrometry

Herein, an analytical method was developed for extraction and quantification of benzbromarone and tolfenamic acid in citrus and soil matrices using liquid-liquid extraction followed by liquid chromatography-triple quadrupole-tandem mass spectrometry analysis. The compounds were extracted using 0.1% formic acid in 6:4 ethyl acetate and n-hexane solution, and the analytes were separated using a mixture of 0.1% formic acid in ultrapure water and 0.1% formic acid in acetonitrile as mobile phase. A six-point in-matrix calibration curve was constructed providing good linearity with coefficients of determination R ² ≥ 0.98. The limits of detection and quantification for benzbromarone and tolfenamic acid were 3.0 and 10.0 μg/kg in roots, peel, juice, and soil, and 4.0 and 12.0 μg/kg for leaves samples, respectively. The method yielded excellent recoveries between 81.3 and 101.2%, with relative standard deviation ≤9.5% in the matrices. The developed technique provides a simple and sensitive method for the determination of the chemicals and can be applied to agricultural practices.

GC-NICI-MS analysis of acetazolamide and other sulfonamide (R-SO2-NH2) drugs as pentafluorobenzyl derivatives [R-SO2-N(PFB)2] and quantification of pharmacological acetazolamide in human urine

Acetazolamide (molecular mass (MM), 222) belongs to the class of sulfonamides (R-SO₂-NH₂) and is one of the strongest pharmacological inhibitors of carbonic anhydrase activity. Acetazolamide is excreted unchanged in the urine. Here, we report on the development, validation and biomedical application of a stable-isotope dilution GC-MS method for the reliable quantitative determination of acetazolamide in human urine. The method is based on evaporation to dryness of 50 μL urine aliquots, base-catalyzed derivatization of acetazolamide (d₀-AZM) and its internal standard [acetylo-²H₃]acetazolamide (d₃-AZM) in 30 vol% pentafluorobenzyl (PFB) bromide in acetonitrile (60 min, 30 °C), reconstitution in toluene (200 μL) and injection of 1-μL aliquots. The negative-ion chemical ionization (NICI) mass spectra (methane) of the PFB derivatives contained several intense ions including [M]^‒ at m/z 581 for d₀-AZM and m/z 584 for d₃-AZM, suggesting derivatization of their sulfonamide groups to form N,N-dipentafluorobenzyl derivatives (R-SO₂-N(PFB)₂), i.e., d₀-AZM-(PFB)₂ and d₃-AZM-(PFB)₂, respectively. Quantification was performed by selected-ion monitoring of m/z 581 and 83 for d₀-AZM-(PFB)₂ and m/z 584 and 86 for d₃-AZM-(PFB)₂. The limits of detection and quantitation of the method were determined to be 300 fmol (67 pg) and 1 μM of acetazolamide, respectively. Intra- and inter-assay precision and accuracy for acetazolamide in human urine samples in pharmacologically relevant concentration ranges were determined to be 0.3%–4.2% and 95.3%–109%, respectively. The method was applied to measure urinary acetazolamide excretion after ingestion of a 250 mg acetazolamide-containing tablet (Acemit®) by a healthy volunteer. Among other tested sulfonamide drugs, methazolamide (MM, 236) was also found to form a N,N-dipentafluorobenzyl derivative, whereas dorzolamide (MM, 324) was hardly detectable. No GC-MS peaks were obtained from the PFB bromide derivatization of hydrochlorothiazide (MM, 298), xipamide (MM, 355), indapamide and metholazone (MM, 366 each) or brinzolamide (MM, 384). We demonstrate for the first time that sulfonamide drugs can be derivatized with PFB bromide and quantitated by GC-MS. Sulfonamides with MM larger than 236 are likely to be derivatized by PFB bromide but to lack thermal stability.

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The sulfonamide group of acetazolamide was derivatized for the first time with pentafluorobenzyl bromide.

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Other sulfonamides were also derivatized for the first time with pentafluorobenzyl bromide.

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Pentafluorobenzyl derivatives of acetazolamide and other sulfonamides are useful for GC-MS.

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The validated method was used to quantify pharmacological acetazolamide in human urine.

The abuse of diuretics as performance-enhancing drugs and masking agents in sport doping: pharmacology, toxicology and analysis

Diuretics are drugs that increase the rate of urine flow and sodium excretion to adjust the volume and composition of body fluids. There are several major categories of this drug class and the compounds vary greatly in structure, physicochemical properties, effects on urinary composition and renal haemodynamics, and site and mechanism of action. Diuretics are often abused by athletes to excrete water for rapid weight loss and to mask the presence of other banned substances. Because of their abuse by athletes, diuretics have been included on The World Anti-Doping Agency's (WADA) list of prohibited substances; the use of diuretics is banned both in competition and out of competition and diuretics are routinely screened for by anti-doping laboratories. This review provides an overview of the pharmacology and toxicology of diuretics and discusses their application in sports. The most common analytical strategies currently followed by the anti-doping laboratories accredited by the WADA are discussed along with the challenges laboratories face for the analysis of this diverse class of drugs.

Detection of the misuse of steroids in doping control

The list of prohibited substances of the World Anti-Doping Agency (WADA) classifies the administration of several steroids in sports as doping. Their analysis is generally performed using urine specimen as matrix. Lots of the steroids are extensively metabolised in the human body. Thus, knowledge of urinary excretion is extremely important for the sensitive detection of steroid misuse in doping control. The methods routinely used in steroid screening mainly focus on substances, that are excreted unconjugated or as glucuronides. Common procedures include deconjugation using a beta-glucuronidase enzyme. Following extraction and concentration the analytes are submitted to LC-MS(/MS) analysis and/or GC-MS(/MS) analyses. Besides the classical steroids, more and more products appear on the market for "dietary supplements" containing steroids that have never been marketed as approved drugs, mostly without proper labelling of the contents. To cover the whole range of potential products comprehensive screening tools have to be utilised in addition to the classical methods. Endogenous steroids, e.g. testosterone, represent a special group of compounds. As classical chemical methodology is incapable of discriminating synthetic hormones from the biosynthesised congeners, the method of steroid profiling is used for screening purpose. Additionally, based on isotope signatures a discrimination of synthetic and natural hormones can be achieved.

Generic sample preparation combined with high-resolution liquid chromatography-time-of-flight mass spectrometry for unification of urine screening in doping-control laboratories

A unification of doping-control screening procedures of prohibited small molecule substances--including stimulants, narcotics, steroids, beta2-agonists and diuretics--is highly urgent in order to free resources for new classes such as banned proteins. Conceptually this may be achieved by the use of a combination of one gas chromatography-time-of-flight mass spectrometry method and one liquid chromatography-time-of-flight mass spectrometry method. In this work a quantitative screening method using high-resolution liquid chromatography in combination with accurate-mass time-of-flight mass spectrometry was developed and validated for determination of glucocorticosteroids, beta2-agonists, thiazide diuretics, and narcotics and stimulants in urine. To enable the simultaneous isolation of all the compounds of interest and the necessary purification of the resulting extracts, a generic extraction and hydrolysis procedure was combined with a solid-phase extraction modified for these groups of compounds. All 56 compounds are determined using positive electrospray ionisation with the exception of the thiazide diuretics for which the best sensitivity was obtained by using negative electrospray ionisation. The results show that, with the exception of clenhexyl, procaterol, and reproterol, all compounds can be detected below the respective minimum required performance level and the results for linearity, repeatability, within-lab reproducibility, and accuracy show that the method can be used for quantitative screening. If qualitative screening is sufficient the instrumental analysis may be limited to positive ionisation, because all analytes including the thiazides can be detected at the respective minimum required levels in the positive mode. The results show that the application of accurate-mass time-of-flight mass spectrometry in combination with generic extraction and purification procedures is suitable for unification and expansion of the window of screening methods of doping laboratories. Moreover, the full-scan accurate-mass data sets obtained still allow retrospective examination for emerging doping agents, without re-analyzing the samples.

Masking and manipulation

The list of prohibited substances in sports includes a group of masking agents that are forbidden in both in- and out-of-competition doping tests. This group consists of a series of compounds that are misused in sports to mask the administration of other doping agents, and includes: diuretics, used to reduce the concentration in urine of other doping agents either by increasing the urine volume or by reducing the excretion of basic doping agents by increasing the urinary pH; probenecid, used to reduce the concentration in urine of acidic compounds, such as glucuronoconjugates of some doping agents; 5alpha-reductase inhibitors, used to reduce the formation of 5alpha-reduced metabolites of anabolic androgenic steroids; plasma expanders, used to maintain the plasma volume after misuse of erythropoietin or red blood cells concentrates; and epitestosterone, used to mask the detection of the administration of testosterone. Diuretics may be also misused to achieve acute weight loss before competition in sports with weight categories. In this chapter, pharmacological modes of action, intended pharmacological effects for doping purposes, main routes of biotransformation and analytical procedures used for anti-doping controls to screen and confirm these substances will be reviewed and discussed.

Simultaneous analysis of thirteen diuretics residues in bovine milk by ultra-performance liquid chromatography/tandem mass spectrometry

A simple, rapid, sensitive and specific method used to screen and confirm multi-class diuretics residues in whole bovine milk is described. Thirteen drugs of four different classes including carbonic anhydrase inhibitors, loop, thiazide and potassium-sparing diuretics were extracted from whole milk by acetonitrile followed by further purification with hexane. The analytes were separated using an ACQUITY UPLC BEH C18 column and detected by electrospray ionization tandem mass spectrometry (ESI-MS/MS). MS data acquisition was performed by a time-scheduled multiple reaction monitoring program, selecting two ion transitions for each target compound. The overall average recoveries based on matrix-fortified curves fortified with diuretics at three levels ranged from 80.6 to 108.8% with the coefficients of variation ranging from 2.6 to 19.7% (n = 6). The limits of quantitation (LOQs) of diuretics in bovine milk were 5.0 microg/kg for spironolactone and 0.5 microg/kg for other analytes, respectively.

A direct screening procedure for diuretics in human urine by liquid chromatography-tandem mass spectrometry with information dependent acquisition

BACKGROUND

Diuretics are a class of compounds largely used for either therapeutic (edemas, hypertension, etc.) or illegal (doping) purposes. Probably owing to the substantial variety of their chemical structures, which makes them hardly extractable from a biological matrix in a single procedure, a quite short list of screening methods can be retrieved in the literature.

METHODS

This work presents a screening procedure for 24 diuretics based on the direct injection of urine (after 50 folds dilution) in a LC-ESI-MS/MS system (Applied Biosytems 4000 QTrap). Two information dependent acquisitions (IDA), one in positive, one in negative ionization, allowed the acquisition of one selected reaction monitoring transition for each compound, which, when a significant peak was found, triggered the acquisition of the enhanced product ion (EPI) spectrum.

RESULTS AND CONCLUSIONS

EPI spectra were stored in a library and the procedure was able to recognize by library matching various diuretics in real positive samples. The limits of detection were comprised between 0.002 and 0.25 mg/l and ion suppression was not found to significantly influence the analysis.

Requirements for bioanalytical procedures in postmortem toxicology

The application of analytical techniques in postmortem toxicology is often more difficult than in other forms of forensic toxicology owing to the variable and often degraded nature of the specimens and the diverse range of specimens available for analysis. Consequently, analysts must ensure that all methods are fully validated for the particular postmortem specimen(s) used. Collection of specimens must be standardized to minimize site-to-site variability and should if available include a peripheral blood sample and at least one other specimen. Urine and vitreous humor are good specimens to complement blood. In some circumstances solid tissues such as liver are recommended as well as gastric contents. Substance-screening techniques are the most important element since they will determine the range of substances that were targeted in the investigation and provide initial indication of the possible role of substances in the death. While immunoassay techniques are still commonly used for the most common drugs-of-abuse, chromatographic screening methods are required for general unknown testing. These are still predominately gas chromatography (GC) based using nitrogen/phosphorous detection and/or mass spectrometry (MS) detection, although some laboratories are now using time-of-flight MS or liquid chromatography (LC)-MS(MS) to cover a sometimes more limited range of substances. It is recommended that laboratories include a second chromatographic method to provide coverage of acidic and other substances not readily covered by a GC-based screen when extracts do not include all physiochemical types. This may include a gradient high-performance liquid chromatography (HPLC) photodiode array method, or better LC-MS(MS). Substance-specific techniques (e.g., benzodiazepines, opiates) providing a second form of identification (confirmation) are now divided between GC-MS(MS) and LC-MS(MS) procedures. LC-MS(MS) has taken over from many methods for the more polar compounds previously used in HPLC or in GC methods requiring derivatization. Analysts using LC-MS will need to obtain clean extracts to avoid poor and variable sensitivity caused by background suppression of the signal. Isolation techniques in postmortem toxicology tend to favor liquid extraction; however solid-phase extraction and solid-phase microextraction methods are available for many analytes.

Comparison of Urinary On-Site Immunoassay Screening and Gas Chromatography-Mass Spectrometry Results of 111 Patients With Suspected Poisoning Presenting at an Emergency Department

On-site tests based on immunoassay techniques are widely used for toxicologic screening analysis in patients with suspected poisoning. However, such assays usually have been validated using urine samples with known concentrations of the investigated substances. In the present investigation, on-site screening results were evaluated in a clinical setting. This was a retrospective study of patients with suspected poisoning from January to December 2003 in the emergency department of a tertiary urban hospital. Urine samples were analyzed using the Triage 8 panel and gas chromatography-mass spectrometry (GC-MS). A total of 111 patients were included (54 female, 57 male; average age 37.8 +/- 19.7 years). A total of 3.8% of the patients showed no symptoms, 45.2% minor, 24.0% moderate, and 26.9% serious symptoms. In 50 patients (45.0%), Triage 8 results corresponded well with GC-MS results. In 17 patients (15.3%), the Triage 8 results were confirmed by GC-MS, but additional substances were determined that could not be detected by the Triage 8 panel. A completely negative Triage 8 screening result was obtained in 23 patients (20.7%) who showed toxicologically relevant findings in GC-MS. In 21 patients (18.9%), Triage 8 results could not be confirmed by GC-MS. The analysis of the results in view of the patients' medical histories revealed that in 20 patients (18.0%), no relevant toxic substance could be detected. Additionally, 8 patients (7.2%) showed intoxication with alcohol, which could not be detected by the presently applied toxicologic screening investigations. On-site screening results in suspected poisoning were not very helpful in the present study because practically every second patient ingested substances that were not detectable by the Triage 8 device. In addition, every fifth result was not in line with GC-MS findings. On-site test findings should be interpreted very carefully, and in critical cases, a GC-MS screening should be performed.

Mass spectrometry in sports drug testing: Structure characterization and analytical assays

Owing to the sensitive, selective, and unambiguous nature of mass spectrometric analyses, chromatographic techniques interfaced to various kinds of mass spectrometers have become the most frequently employed strategy in the fight against doping. To obtain utmost confidence in analytical assays, mass spectrometric characterization of target analytes and typical dissociation pathways have been utilized as basis for the development of reliable and robust screening as well as confirmation procedures. Methods for qualitative and/or quantitative determinations of prohibited low and high molecular weight drugs have been established in doping control laboratories preferably employing gas or liquid chromatography combined with electron, chemical, or atmospheric pressure ionization followed by analyses using quadrupole, ion trap, linear ion trap, or hyphenated techniques. The versatility of modern mass spectrometers enable specific as well as comprehensive measurements allowing sports drug testing laboratories to determine the misuse of therapeutics such as anabolic-androgenic steroids, stimulants, masking agents or so-called designer drugs in athletes' blood or urine specimens, and a selection of recent developments is summarized in this review.

Demands on scientific studies in clinical toxicology

Scientific case studies in clinical toxicology on single cases or series of similar cases should document sufficient information on the clinical methodology and observations, the medical laboratory methodology and results, the toxicological analyses methodology and results, the source of used reference values for drug/poison concentrations and kinetics with critical discussion of such values, a description and discussion of the toxicodynamic, the toxicological and the kinetic properties of the detected drugs and/or poisons. The data management, statistical analysis and finally the clinical and/or analytical outcomes must also be described and discussed in correlation to already published data. Statistical methods used for evaluation of clinical as well as for analytical data should be described in detail. When possible, quantitative findings should be presented with appropriate indicators of measurement error or uncertainty. Requirements for such studies are discussed.

Fast gas chromatographic/mass spectrometric determination of diuretics and masking agents in human urine

An analytical procedure was developed for the fast screening of 16 diuretics (acetazolamide, althiazide, amiloride, bendroflumethiazide, bumetanide, canrenoic acid, chlorthalidone, chlorthiazide, clopamide, ethacrynic acid, furosemide, hydrochlorthiazide, hydroflumethiazide, indapamide, triamterene, trichlormethiazide) and a masking agent (probenecid) in human urine. The whole method involves three analytical steps, including (1) liquid/liquid extraction of the analytes from the matrix, (2) their reaction with methyl iodide at 70 degrees C for 2 h to form methyl derivatives, (3) analysis of the resulting mixture by fast gas chromatography/electron impact mass spectrometry (fast GC/EI-MS). The analytical method was validated by determining selectivity, linearity, accuracy, intra and inter assay precision, extraction efficiencies and signal to noise ratio (S/N) at the lowest calibration level (LCL) for all candidate analytes. The analytical performances of three extraction procedures and five combination of derivatization parameters were compared in order to probe the conditions for speeding up the sample preparation step. Limits of detection (LOD) were evaluated in both EI-MS and ECNI-MS (electron capture negative ionization mass spectrometry) modes, indicating better sensitivity for most of the analytes using the latter ionization technique. The use of short columns and high carrier gas velocity in fast GC/MS produced efficient separation of the analytes in less than 4 min, resulting in a drastic reduction of the analysis time, while a resolution comparable to that obtained from classic GC conditions is maintained. Fast quadrupole MS electronics allows high scan rates and effective data acquisition both in scan and selected ion monitoring modes.