Applicability of microwave acid digestion to sample preparation of biological materials for analysis by particle-induced X-ray emission (PIXE)

A microwave acid digestion method for the preparation of biological samples for PIXE analysis is presented. The precision and accuracy of the entire PIXE analytical procedure, including the micro-wave digestion step, were evaluated by analyzing eight certified reference materials. For elements heavier than K, and for concentration levels from 2 μg/g upward, the total random error of a single analysis is in the range of 2–5%. The accuracy is better than 5%. The detection limits are down to 0.3 μg/g.

     

Direct extract derivatization for determination of amino acids in human urine by gas chromatography and mass spectrometry

The purpose of this study was to develop a simple and accurate analytical method to determine amino acids in urine samples. The developed method involves the employment of an extract derivatization technique together with gas chromatography-mass spectrometry (GC-MS). Urine samples (300 microl) and an internal standard (10 microl) were placed in a screw tube. Ethylchloroformate (50 microl), methanol-pyridine (500 microl, 4:1, v/v) and chloroform (1 ml) were added to the tube. The organic layer (1 microl) was injected to a GC-MS system. In this proposed method, the amino acids in urine were derivatized during an extraction, and the analytes were then injected to GC-MS without an evaporation of the organic solvent extracted. Sample preparation was only required for ca. 5 min. The 15 amino acids (alanine, aspartic acid, cysteine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, tyrosine, tryptophan, valine) quantitatively determined in this proposed method. However, threonine, serine, asparagine, glutamine, arginine were not derivatized using any tested derivatizing reagent. The calibration curves showed linearity in the range of 1.0-300 microg/ml for each amino acid in urine. The correlation coefficients of the calibration curves of the tested amino acids were from 0.966 to 0.998. The limit of detection in urine was 0.5 microg/ml except for aspartic acid. This proposed method demonstrated substantial accuracy for detection of normal levels. This proposed method was limited for the determination of 15 amino acids in urine. However, the sample preparation was simple and rapid, and this method is suitable for a routine analysis of amino acids in urine.     

Gas chromatographic method with mass-selective detection for the determination of 2-isopropoxyphenol in human urine

Human metabolism of the insecticide propoxur yields 2-isopropoxyphenol (IPP) which is excreted conjugated in urine. In this publication a sensitive and selective analytical method is described which permits the determination of IPP as a suitable parameter for biomonitoring. The clean-up of the hydrolysed urine samples consisted of steam distillation and solid-phase extraction using a reversed-phase column. IPP and the internal standard 2-ethoxyphenol were converted to their pentafluorobenzyl ethers. Excess of the derivatisation reagent was removed using deactivated silica gel. Separation and quantitative analysis was carried out by capillary gas chromatography and mass selective detection. Coefficients of variation were below 5% for concentrations from 6 to 300 μg/l. The detection limit was 0.5 μg/l. The method was checked by analysing six urine samples from pest controllers after indoor application of propoxur. The IPP concentrations ranged from 45 to 306 μg/g creatinine. IPP was not detected in urine specimens from 10 non-exposed persons. The sensitivity of the developed method permits the detection of latent exposure to propoxur.     

Concentrations of selected trace elements in human milk and in infant formulas determined by magnetic sector field inductively coupled plasma-mass spectrometry

Magnetic sector field inductively coupled plasma-mass spectrometry (ICP-MS) was applied to the reliable determination of the 8 essential trace elements cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), selenium (Se), and vanadium (V) as well as the 7 nonessential and toxic elements silver (Ag), aluminum (Al), arsenic (As), gold (Au), platinum (Pt), scandium (Sc), and titanum (Ti) in 27 transitory and mature human milk samples and in 4 selected infant formulas. This advanced instrumentation can separate spectral overlaps from the analyte signal hampering significantly the determination of many trace elements by conventional ICP-MS. Moreover, superior detection limits in the picogram per liter range can be obtained with such magnetic sector field instruments. Therefore, this is the first study to report the concentrations of the elements Ag, Au, Pt, Sc, Ti, and V in human milk and in infant formulas. Concentrations of Ag (median: 0.41 μg/L; range: <0.13–42 μg/L) and Au (median: 0.29 μg/L; range 0.10–2.06 μg/L) showed large variations in human milk that might be associated with dental fillings and jewelry. Pt concentrations were very low with most of the samples below the method detection limit of 0.01 μg/L. Human milk concentrations of Co (median: 0.19 μg/L), Fe (380 μg/L), Mn (6.3 μg/L), Ni (0.79 μg/L), and Se (17 μg/L) were at the low end of the corresponding reference ranges. Concentrations of Cr (24.3 μg/L) in human milk were five times higher than the high end of the reference range. For Al (67 μg/L), As (6.7 μg/L), and V (0.18 μg/L), most of the samples had concentrations well within the reference ranges. All elemental concentrations in infant formulas (except for Cr) were approximately one order of magnitude higher than in human milk.     

Determination of 235U and 238U in urine samples using sector field inductively coupled plasma mass spectrometry

The high sensitivity of SF-ICP-MS (sector field inductively coupled plasma mass spectrometry) using a torch with the "guard-electrode" (capacitive decoupled plasma) allows the determination of 238U (isotope abundance 99.2%) and 235U (0.8%) and their isotope ratio in human urine samples down to the physiological level of <10 ng/l total uranium. For sample preparation UV photolysis was used. Some quality criteria like for the detection limit, the reproducibility, recovery and the isotope ratio are given. The method can be applied in occupational as well as in environmental medicine because of its outstanding detection power.     

Liquid chromatographic method for detection and quantitation of STI-571 and its main metabolite N-desmethyl-STI in plasma, urine, cerebrospinal fluid, culture medium and cell preparations

An isocratic online-enrichment HPLC-assay was developed allowing for the simple and fast separation and quantitation of STI-571 and its main metabolite N-desmethyl-STI (N-DesM-STI) in plasma, urine, cerebrospinal fluid (CSF), culture media and cell preparations in various concentrations using UV-detection at 260 nm. The analytical procedure consists of an online concentration of STI-571 and N-DesM-STI in the HPLC system followed by the elution on a ZirChrom-PBD analytical column. Time of analysis is 40 min including the enrichment time of 5 min. The detection limit is 10 ng/ml in plasma, CSF, culture medium (RPMI) and 25 ng/ml in urine for both STI-571 and N-DesM-STI. The intra-day precision, as expressed by the coefficient of variation (CV), in plasma samples ranges between 1.74 and 8.60% for STI-571 and 1.45 and 8.87% for N-DesM-STI. The corresponding values for urine measurements are 2.17-7.54% (STI-571) and 1.31-9.51% (N-DesM-STI). The inter-day precision analyzed over a 7-month time period was 8.31% (STI-571) or 6.88% (N-DesM-STI) and 16.45% (STI-571) or 14.83% (N-DesM-STI) for a concentration of 1000 ng/ml in plasma and 750 ng/ml in urine, respectively. Moreover, we demonstrate that with an alternative, but more time and labor consuming sample preparation and the implementation of electrochemical detection, a detection limit < 10 ng/ml can be achieved. The method described was used to perform pharmacokinetic measurements of STI-571 and N-desmethyl-STI in patient samples and for kinetic measurements of intracellular STI-571 and N-DesM-STI following in vitro incubation.     

High-performance liquid chromatographic determination of the magnetic resonance imaging contrast agent Gadocoletate ion in human plasma, urine and faeces

Gadocoletate ion is a new paramagnetic intravascular contrast agent for magnetic resonance imaging (MRI). An high-performance liquid chromatographic method for assaying Gadocoletate ion in human plasma, urine and faecal samples is described. The analysis is based on the reversed-phase chromatographic separation of Gadocoletate ion from the endogenous components of the biological matrices and its detection during elution by ultraviolet light absorption at 200 nm. The selectivity of the method was satisfactory. The mean absolute recovery during the analytical sample preparation was greater than 87%. The precision, expressed as coefficient of variation (CV%) ranged from 0.29 to 5.90% and the accuracy, expressed as mean relative error (R.E.%) of the analytical method ranged from -3.7 to +7.1%. The detection limit in plasma and urine was 2.01 and 10.0 microg/mL (0.00203 and 0.0101 micromol/mL), respectively. The detection limit in homogenized faecal samples was 17.7 microg/g (0.0179 micromol/g). Stability studies were performed in human plasma and urine samples during the analytical cycle. Gadocoletate ion was shown to be stable in human plasma and in human urine when stored at about +4 degrees C for up 24 h, and after three freeze-thaw cycles. In addition, it was shown to be stable in samples of processed plasma and in diluted urine at about +4 degrees C for 48 h, and at room temperature for at least 24 h. As regards the long-term stability of Gadocoletate ion, the results of dedicated studies showed that Gadocoletate ion is stable in human plasma samples when stored at +4 degrees C for up to 30 days and at -80 degrees C for up to 90 days. Gadocoletate ion is stable in samples of human urine when stored at +4 degrees C for up to 30 days, and when stored at -20 degrees C and at -80 degrees C for up to 90 days. The method has been successfully validated in human plasma, urine and faeces and it has been shown to be precise, accurate and reliable.     

Determination of dopamine and methoxycatecholamines in patient urine by liquid chromatography with electrochemical detection and by capillary electrophoresis coupled with spectrophotometry and mass spectrometry

The applicability of capillary electrophoresis (CE) with UV and mass spectrometric (MS) detection for the determination of dopamine and methoxycatecholamines in urine was evaluated in comparison with the liquid chromatography-electrochemical detection (LC-EC) method widely used in catecholamine analysis. The catecholamines in urine were deconjugated with acid or enzyme hydrolysis, purified by cation exchange (CEX) or solid-phase extraction (SPE) with a copolymer of N-divinylpyrrolidone and divinylbenzene and analyzed by LC-EC, CE-UV, and CE-MS. Acid hydrolysis was more effective in the deconjugation than enzymatic hydrolysis with Helix pomatia. However, the recoveries of HMBA, DA and NMN from spiked samples were less than 30% after acid hydrolysis and SPE purification. The CEX purification was more efficient than SPE in removing matrix compounds from the urine samples. The limits of detection were lower in LC-EC analysis than in CE-UV or CE-MS. Many factors in the analytical procedure caused deviations in the concentrations measured for urinary dopamine and methoxycatecholamines. The recovery of HMBA, which was used as the internal standard, was poor after acid hydrolysis and SPE purification. The purification methods were validated in conjunction with the analytical methods and therefore cross analysis was unsuccessful. The LC-EC method was the most sensitive, but CE-UV and CE-MS were sensitive enough for the determination of dopamine and methoxycatecholamines even in healthy patient urine. The EC and MS detections were superior to the UV detection in specificity since, after acid hydrolysis, some matrix compounds were migrating close to I.S., DA and 3MT.     

A novel Real Time micro PCR based Point-of-Care device for Salmonella detection in human clinical samples

Our POC (Point of Care) device is intended to be a diagnostic tool for routine use in the clinical sector. The validation of the whole procedure, including bacterial genomic DNA isolation and the Real Time detection of Salmonella spp., was conducted on 29 clinical stool samples that had been diagnosed with Salmonella spp. by a routine culture technique. The entire process was achieved in a single microfluidic chip within 35 min. In comparison to the culture reference method that is used in the clinical laboratories, this new device performed well in regards to the analytical parameters of sensitivity, specificity and accuracy. Therefore, the POC device reported in this study proved to be very appropriate for the fully integrated analysis system. To the best of our knowledge, this is the first work to report the sample preparation and followed by Real Time PCR (Polymerase Chain Reaction) on a single 2.5 μl chamber chip for the detection of Salmonella spp. bacteria in stool samples.     

High-sensitivity capillary electrophoresis determination of inorganic anions in serum and urine using on-line preconcentration by transient isotachophoresis

Concentrations of inorganic anions, both as individual species and biotransformation products, in physiological fluids are of strong concern in clinical studies. To date, analytical methodologies have either required different analytical procedures to determine these analytes in plasma and urine, or extensive sample preparation, or unconventional and often expensive detection schemes, or both. A simple and sensitive capillary electrophoresis (CE) method with direct UV detection was developed for the simultaneous determination of iodide, bromide and nitrate in human plasma and urine, with a special focus on reliable quantification of the trace serum iodide. With the latter objective, the method incorporates a transient isotachophoresis (tITP) procedure enabling an efficient on-line preconcentration of iodide (limit of detection, 1.4 microg l(-1)) as well as other moderately mobile analytes that fall into the tITP range. The analyses of both types of biofluids were performed using an acidic electrolyte system composed of 0.25 mol l(-1) sodium chloride and 7.5 mmol l(-1) cetyltrimethylammonium chloride at pH 2.2 and 0.5 mol l(-1) 2-(N-morpholino)ethanesulfonate (pH 6.0) as terminating electrolyte. Relative standard deviations (R.S.D.) below 3.0% and 9.2% were obtained for within-day and between-day precision, respectively. Resolution and quantification of oxalic acid was also feasible under optimized tITP-CE conditions. Sample preparation required only ultrafiltration (serum) and dilution (urine). A number of plasma and urine samples were evaluated with this assay and the iodide, bromide and nitrate concentrations were in the expected clinical concentration ranges.     

Quantification of riboflavin in human urine using high performance liquid chromatography-tandem mass spectrometry

We developed a selective method to measure riboflavin in human urine. Sample preparation involved solid phase extraction and concentration of the target analyte in urine. The urine concentrate was analyzed using high performance liquid chromatography-tandem mass spectrometry. Riboflavin concentrations were quantified using an isotopically labeled internal standard. The limit of detection was 11 ng/mL, and the linear range was 4.4-20,000 ng/mL. The relative standard deviation at 100, 1000, and 5000 ng/mL was 17%, 17%, and 12%, respectively. The accuracy was 90%. On average, 100 samples, including calibration standards and quality control samples, were prepared per day. Using our method, we measured concentrations of riboflavin in human urine samples that were collected from participants in a study where riboflavin was used as a surrogate chemical to simulate exposure to an environmental toxicant.     

Quantification of 3,4-methylenedioxymetamphetamine and its metabolites in plasma and urine by gas chromatography with nitrogen–phosphorus detection

A gas chromatographic method with nitrogen–phosphorus detection involving a solid–liquid extraction phase was developed and validated for the simultaneous quantification of 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) in plasma. A modification of this method was validated for the analysis of MDMA, MDA, 4-hydroxy-3-methoxymethamphetamine (HMMA) and, 4-hydroxy-3-methoxyamphetamine (HMA) in urine. Under the analytical conditions described, the limits of detection in plasma and urine were less than 1.6 μg/l and 47 μg/l, respectively, for all the compounds studied. Good linearity was observed in the concentration range evaluated in plasma (5–400 μg/l) and urine (100–2000 μg/l) for all compounds tested. The recoveries obtained from plasma were 85.1% and 91.6% for MDMA and MDA, respectively. Urine recoveries were higher than 90% for MDMA and MDA, 74% for HMMA, and 64% for HMA. Methods have been successfully used in the assessment of plasma and urine concentrations of MDMA and its main metabolites in samples from clinical studies in healthy volunteers.     

Determination of endogenous thiols and thiol drugs in urine by HPLC with ultraviolet detection

Analysis of urine for endogenous thiols and thiol drugs content by HPLC with ultraviolet detection is addressed. Other methodologies for detection and determination of thiols in urine are only mentioned. Outline of metabolism, role of main biological thiols in physiological and pathological processes and their reference concentrations in urine are presented. In particular, urine sample preparation procedures, including reduction of thiol disulfides, chemical derivatization and reversed-phase HPLC separation steps are discussed. Some experimental details of analytical procedures for determination of endogenous thiols cysteine, cysteinylglycine, homocysteine, N-acetylcysteine, thioglycolic acid; and thiol drugs cysteamine, tiopronin, d-penicillamine, captopril, mesna, methimazole, propylthiouracil and thioguanine are reviewed.     

Measurement uncertainty from physical sample preparation of moss samples: Estimation of mechanical cleaning vs. rinsing

Next to sampling, the physical sample preparation step is a second large source of uncertainty. To assess the level of uncertainty from sampling, sample preparation and analysis of moss material, 27 combined and duplicate samples of moss species Pleurozium schreberi (Brid.) Mitt were collected and prepared for analysis using two different treatment methods After sampling had been done, samples were dried at an ambient temperature and then each primary and duplicate sample was divided into two sub-samples for preparation. The first sub-sample was manually cleaned whereas the second one was triple rinsed with deionized water and left to dry. Subsequently, the samples were milled and digested in a close microwave system with 8 mL of HNO₃ (1:1) and 1 mL of 30% H₂O₂. In all samples Cu, Fe and Zn were determined using GFAAS and FAAS techniques. Each sample was analyzed twice. Sampling, sample preparation and analytical uncertainty were calculated using ANOVA, RANOVA, modified RANOVA and range statistics methods. Sampling and sample preparation uncertainty varied from 3.8 to 19.8% and from 3.6 to 11.2%, respectively. For all the elements examined analytical uncertainty was below 1.1%. The comparison of element concentrations in manually cleaned and rinsed samples showed that rinsed samples were enriched in Cu and Zn, as opposed to manually cleaned that in turn displayed raised levels of Fe. However, except for Zn, these differences were not statistically significant.     

Preliminary investigation of using volatile organic compounds from human expired air, blood and urine for locating entrapped people in earthquakes

A preliminary investigation on the possibility of using volatile organic compounds (VOCs) determination of expired air, blood and urine, for the early location of entrapped people in earthquakes, has been carried out. A group of 15 healthy subjects has been sampled. The identification of a common "core" of substances might provide indications of human presence that can be used for the development of a real time field analytical method for the on site detection of entrapped people. Expired air samples have been analyzed by thermal desorption GC/MS and VOCs from blood and urine by headspace SPME-GC/MS. Acetone was the only compound found common in all three matrices. Isoprene was found in both expired air and blood samples. Acetone and isoprene along with a number of saturated hydrocarbons were among the major constituents identified in expired air analysis. Various ketones (2-pentanone, 4-heptanone, 2-butanone) were also determined over urine specimens. Using the techniques and methods of field analytical chemistry and technology appears to be the proper approach for applying the results of the present study in real situations.     

Determination of cadmium in blood, plasma, and urine by electrothermal atomic absorption spectrophotometry after isolation by anion-exchange chromatography

The determination of cadmium in whole blood, urine, or plasma by atomic absorption using electrothermal atomization is described. In preparation for atomic absorption analysis, cadmium was concentrated on an anion-exchange column, significantly lowering the limit of detection and allowing for the first time the accurate and precise determination of plasma cadmium concentrations in persons/animals with low-level cadmium exposures. Recovery of 109Cd from spiked whole blood, plasma, and urine into supernatants of nitric acid-deproteinated samples averaged 99, 100, and 95%, respectively. Anion-exchange isolation of the anionic chlorocadmium complex removed 99.8% of the major elements associated with a deproteinated whole blood sample. The recovery of 109Cd from the anion-exchange column was 92.2 +/- 0.9% (mean +/- SE, N = 35). The separation of cadmium from constituents in blood, urine, or plasma in this manner allowed comparison of unknown samples to aqueous standards with a defined acid matrix using commercially available acids. The mean intra-assay coefficient of variation (CV) was 12 +/- 3% (mean +/- SE, N = 6) for blood, plasma, and urine samples having cadmium concentrations of 0.1-0.8 microgram/liter. The interassay CV was 13% (N = 7) for a blood sample containing 0.6 microgram Cd/liter. The recovery of known amounts of cadmium added to blood, plasma, and urine in the range of 0.2 to 5.0 micrograms Cd/liter was 97 +/- 6% (mean +/- SE, N = 4).     

A new automated method for isolation of Chlamydia trachomatis from urine eliminates inhibition and increases robustness for NAAT systems

Chlamydia trachomatis is a leading cause of sexually transmitted infection. Diagnostic methods with easy non-invasive sample collection are important to increase testing and hence to reduce the spread of this infection. To enable more use of urine samples in C. trachomatis diagnostics, automation is an absolute requirement since obtaining high-quality DNA from urine specimens involves extensive processing.

Here, we present a study in which a new automated sample preparation method, BUGS'n BEADS™ STI (BnB STI), was used up-front of the BDProbeTec™ ET end point analysis and compared with the full BDProbeTec™ ET method to analyze C. trachomatis in 1002 urine samples.

The BnB STI system represents a new concept within magnetic sample preparation in which bacteria are first isolated from the sample material followed by purification of bacterial nucleic acid using the same magnetic particles. Similar sensitivity and specificity were obtained with both methods. None of the samples processed with BnB STI inhibited the BDProbeTec™ ET test whereas 1.8% showed inhibition when processed according to the manual BDProbeTec™ ET DNA preparation method. Moreover, the average MOTA scores obtained with the BnB STI system were 48% higher for all amplification controls and 57% higher for positive samples, compared to the manual sample preparation. Based on these results and the significant reduction in hands-on-time for urine sample processing, the automated BnB STI sample preparation method was implemented for routine analysis of C. trachomatis from urine samples.     

Rapid screening method for determination of Ecstasy and amphetamines in urine samples using gas chromatography-chemical ionisation mass spectrometry

The need for analytical screening tests more reliable and valid to detect amphetamine and related "designer drugs" in biological samples is becoming critical, due to the increasing diffusion of these drugs on the European illegal market. The most common screening procedures based on immunoassays suffer a number of limitations, including low sensitivity, lack of specificity and limited number of detectable substances. This paper describes a screening method based on gas-chromatography-mass-spectrometry (GC/MS) using positive chemical ionisation (PCI) detection. Methanol was used as reactant gas in the ionisation chamber. Molecular ions of different compounds were monitored, allowing a sensitivity of 5-10 ng/ml with high selectivity. The sensitivity of the method gives positive results in samples taken 48-72 h after intake of one dose of 50-100 mg. The method is simple and rapid. Sample preparation was limited to one liquid-liquid extraction, without any hydrolysis and derivatisation. Hydrolysis is critical to identify metabolites excreted as conjugates. Blank urine samples spiked with known amounts of amphetamine (AM), methylamphetamine (MA), methylenedioxyamphetamine (MDA), methylenedioxymethylamphetamine (MDMA), methylenedioxyethylamphetamine (MDEA) and methylenedioxyphenyl-N-methyl-2-butanamine (MBDB) were analysed. The method was successfully tested on real samples of urine from people, whose use of amphetamine was suspected, and results were compared with results obtained with immunoassays.     

Matrix interferences in the analysis of benzene in urine

The analysis of benzene in urine of the general population or of exposed workers can be performed with different methods using the ‘purge and trap’ or ‘solid-phase microextraction’ techniques in combination with gas chromatographic analysis and photoionisation or mass spectrometric detection. The published results, however, are deeply conflicting. Differences in sample preparation by different research groups and our own preliminary observations prompted us to investigate pre-analytical and analytical factors potentially capable of modifying the urinary benzene quantification results. Benzene concentrations were measured in 20 urine samples in relation to different conditioning conditions (at 24, 40 and 80°C) and at basic or acid pH. Urinary protein concentrations were measured in the same samples. Urine heating at 80°C yields benzene concentrations on average five times higher than at 24°C. On acidification of urine, the benzene released increases up to 28-fold in comparison to that obtained at uncorrected ‘physiological’ pH. Despite a widely scattered data distribution, a statistically significant linear correlation was found between ‘heat-released’ and ‘acid-labile’ benzene values. There was no correlation between total urinary proteins present in ‘physiological’ concentrations (between 12 and 110 mg/l) and the different kinds of benzene in urine. Our results could perhaps be explained if it is supposed that part of the benzene in urine is absorbed onto sediment, or bound to specific proteins, or derived from parent molecules and is released with pH modification or heat administration. Our observations may also help to explain why the urinary benzene concentrations reported by different investigators vary considerably even when environmental levels are comparable.     

Quantification of cyanuric acid residue in human urine using high performance liquid chromatography–tandem mass spectrometry

Concern has increased about the resulting health effects of exposure to melamine and its metabolic contaminant, cyanuric acid, after infants in China were fed baby formula milk products contaminated with these compounds. We have developed a selective and sensitive analytical method to quantify the amount of cyanuric acid in human urine. The sample preparation involved extracting free-form cyanuric acid in human urine using anion exchange solid phase extraction. Cyanuric acid was separated from its urinary matrix components on the polymeric strong anion exchange analytical column; the analysis was performed by high performance liquid chromatography–tandem mass spectrometry using negative mode electrospray ionization interface. Quantification was performed using isotope dilution calibration covering the concentration range of 1.00–200 ng/mL. The limit of detection was 0.60 ng/mL and the relative standard deviations were 2.8–10.5% across the calibration range. The relative recovery of cyanuric acid was 100–104%. Our method is suitable to detect urinary concentrations of cyanuric acid caused by either environmental exposures or emerging poisoning events.