Determination of chloramphenicol in aquatic products by graphene‐based SPE coupled with HPLC‐MS/MS

An effective analytical protocol using graphene‐based SPE coupled with HPLC‐MS/MS for determination of chloramphenicol (CAP) in aquatic products has been developed. In the present work, graphene was evaluated as SPE sorbents for the analytes enrichment and clean up. The target analytes were quantified by a triple‐quadrupole linear ion trap MS in multiple‐reaction monitoring mode. In addition, the proposed method was validated according to Commission Decision 2002/657/EC. The calibration curve was linear over the range of 0.5–100 ng/mL. The mean values of RSD of intra‐ and interday ranging from 1.48 to 4.29% and from 3.25 to 7.42% were obtained, respectively. In the three fortified levels, the recoveries of CAP ranging from 92.3 to 103.4% with RSDs ≤ 5.58% were obtained. The proposed method has been successfully applied to the analysis of CAP in several aquatic product samples, indicating that graphene was a potential SPE sorbent for the enrichment of trace residues in food samples.     

Retention behaviour of some high-intensity sweeteners on different SPE sorbents

The objective of this paper is to provide information about application of solid-phase extraction (SPE) for isolation of nine high-intensity sweeteners (acesulfame-K, alitame, aspartame, cyclamate, dulcin, neotame, saccharin, sucralose and neohesperidin dihydrochalcone) from aqueous solutions. The influence of several types of LC-MS compatible buffers (different pH values and compositions) on their recovery has been studied and discussed. A number of commercially available SPE cartridges, such as Chromabond C18ec, Strata-X RP, Bakerbond Octadecyl, Bakerbond SDB-1, Bakerbond SPE Phenyl, Oasis HLB, LiChrolut RP-18, Supelclean LC-18, Discovery DSC-18 and Zorbax C18 were tested in order to evaluate their applicability for the isolation of analytes. Very high recoveries (better than 92%) of all studied compounds were obtained using formic acid-N,N-diisopropylethylamine buffer adjusted to pH 4.5 and C₁₈-bonded silica sorbents. Behaviour of polymeric sorbents strongly depends on their structure. Strata-X RP behaves much like a C₁₈-bonded silica sorbent. Recoveries obtained using Oasis HLB were comparable with those observed for silica-based sorbents. The only compound less efficiently (83%) retained by this sorbent was cyclamate. Bakerbond SDB-1 shows unusual selectivity towards aspartame and alitame. Recoveries of these two sweeteners were very low (26 and 42%, respectively). It was also found that aspartame and alitame can be selectively separated from the mixture of sweeteners using formic acid-triethylamine buffer at pH 3.5.     

Quantification of bile acids directly from urine by MALDI–TOF–MS

The ability to quantify mixtures of bile acids using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry directly from urine has been demonstrated. Six cholic acid derivatives were selected for analysis: taurocholic acid (TCA), taurochenodeoxycholic acid (TCDCA), taurolithocholic acid (TLCA), glycocholic acid (GCA), glycochenodeoxycholic acid (GCDCA), and glycolithocholic acid (GCDCA). Urine samples were pre-concentrated and purified using solid-phase extraction (SPE) columns. The method was optimized to eliminate suppression effects, and proved to be reproducible from day to day. Calibration curves averaged from three days were obtained for the bile acids directly from urine, and then tested for their ability to accurately determine concentrations from one measurement. In summary, a simple, rapid method has been developed for the quantification of bile salts from urine with SPE clean-up by MALDI-MS.     

Analysis of Pterins in Urine by HILIC

Pterins are a class of compounds excreted in urine. Levels of the pterins are found to be significantly elevated in a variety of diseases. A new method involving hydrophilic interaction chromatography with fluorescence detection has been developed for analysis of neopterin, biopterin, and isoxanthopterin in urine samples. Separation of these pterins on an aminopropyl hydrophilic interaction column was achieved by isocratic elution. The effects of the organic modifier content, ionic strength, and pH of the mobile phase on the hydrophilic behavior of the pterins were studied and the mechanism of their separation was also investigated. Under the optimum chromatographic conditions the linearity (r ≥ 0.9995) and repeatability (relative standard deviation < 4.0%) of the method are good. Compared with reversed-phase high-performance liquid chromatography, the method is simple and convenient. The method was applied to the analysis of pterins in urine samples with satisfactory results.     

Monodisperse, hypercrosslinked polymer microspheres as tailor-made sorbents for highly efficient solid-phase extractions of polar pollutants from water samples

In this detailed analytical study, we have evaluated in-house synthesised polymeric solid-phase extraction (SPE) sorbents in the form of monodisperse, hypercrosslinked polymer microspheres with diameters in the low micrometre range (approximately 4 microm). More specifically, their performance in the on-line SPE of a group of polar pollutants has been investigated thoroughly. The novel hypercrosslinked materials were compared with satisfactory results to commercial SPE sorbents with similar chemical and morphological properties, albeit that the commercial materials had higher particle sizes and broader particle size distributions. The on-line SPE method developed using these novel particles as packing material was applied successfully to ultrapure, mineral, tap and Ebre river water samples, with near total recoveries of all the analytes studied when 500 ml samples were percolated through the sorbents. Method validation with river water samples demonstrated good linearity, low detection limits as well as satisfactory precision in terms of repeatability and reproducibility, with values of relative standard deviation (%RSD) lower than 6.7 and 8.7%, respectively.     

Determination of rimantadine in human urine by HPLC using a monolithic stationary phase and on‐line post‐column derivatization

In the present study, we propose the first HPLC method coupled to postcolumn derivatization for the determination of rimantadine in human urine samples. The analyte and amantadine (internal standard) were isocratically separated using an RP monolithic stationary phase (100 × 4.6 mm id) with a mobile phase consisting of CH₃OH/phosphate buffer (25 mmol/L, pH 3.0) at a volume ratio of 50:50. Postcolumn derivatization involved on‐line reaction with o‐phthalaldehyde (20 mmol/L) and N‐acetyl‐cysteine (5 mmol/L) at alkaline medium (100 mmol/L borate pH 11.0). Spectrofluorimetric detection at λ_ex/λ_em = 340/455 nm enabled the selective and sensitive determination of rimantadine in urine samples at a range of 50–500 ng/mL with an LOD of 5 ng/mL. Human urine samples were analyzed successfully after SPE using hydrophilic‐lipophilic balanced RP cartridges (30 mg/mL, Oasis HLB). Recoveries ranged between 89.7 and 102.7%.     

Determination of aliphatic amines by cation‐exchange chromatography with suppressed conductivity detection after solid phase extraction*

A sensitive method for the determination of underivatized aliphatic amines based on cation exchange chromatography coupled with suppressed conductivity detection scheme and solid phase extraction (SPE) procedure has been developed. A surface modified styrene divinylbenzene polymeric sorbent, based on a reversed‐phase (RP) and strong cation exchange (SCX) mixed mode was used as an active material for the SPE of amines. The conductometric capabilities of several aliphatic mono‐ and polyamines, expressed in terms of molar sensitivity (nS/μM), were determined. The LODs, obtained without the SPE treatment, ranged between 20 and 65 nM for putrescine and 2‐butylamine, respectively. The resulting calibration plots for the aliphatic amines were generally linear over about three orders of magnitude, with correlation coefficients >0.98. The LODs of amines decreased generally by one factor when SPE procedure, using BaCl₂/H₂SO₄ eluents, has been adopted. The proposed SPE procedure, seems to offer good results in terms of preconcentration, recoveries and cleanup of samples. The proposed methodology was successfully tested for the quantitative determination of some biogenic amines in beer and tuna.     

Ultrasound‐assisted solid‐phase extraction coupled with photodiode‐array and fluorescence detection for chemotaxonomy of isoflavone phytoestrogens in Trifolium L. (Clover) species

Detailed chemotaxonomic studies were undertaken to establish the qualitative profile and real amounts of the pharmacologically active isoflavone aglycones genistein, daidzein, formononetin, and biochanin A in aerial parts of thirteen Trifolium L. (clover) species, native to Poland. A newly elaborated micropreparative technique – SPE – on BakerBond octadecyl, cyclohexyl, and phenyl cartridges was used in combination with ultrasound‐assisted extraction for isolation of isoflavone aglycones from hydrolyzed samples. The effectiveness of all three SPE sorbents in the purification of plant extracts was compared and very high recoveries (>96%) were documented for four isoflavones. Classical photodiode‐array and very sensitive fluorescence detection, coupled with reversed‐phase high‐performance liquid chromatography (RP‐HPLC), were employed to obtain the most reliable qualitative and quantitative results. Chemotaxonomic differences combined with flower color variability were demonstrated within thirteen clover species. Concentration levels of particular isoflavones in ten Trifolium species possessing flowers with white, pink, or purple‐red corolla ranged from ∼︁3 to ∼︁3300 μg/g dry weight, while in three yellow flowering clovers (T. aureum, T. dubium, and T. campestre) isoflavone compounds have not been detected at all. RSD values, determined for intra‐ and inter‐day precision of the quantitative results, were not higher than 6.2% and 7.1%, respectively.     

SPE coupled with dispersive liquid–liquid microextraction followed by GC with flame ionization detection for the determination of ultra‐trace amounts of benzodiazepines

SPE combined with dispersive liquid–liquid microextration was used for the extraction of ultra‐trace amounts of benzodiazepines (BZPs) including, diazepam, midazolam, and alprazolam, from ultra‐pure water, tap water, fruit juices, and urine samples. The analytes were adsorbed from large volume samples (60 mL) onto octadecyl silica SPE columns. After the elution of the desired compounds from sorbents with 2.0 mL acetone, 0.5 mL of eluent containing 40.0 μL chloroform was injected rapidly into 4.5 mL pure water. After extraction and centrifugation, 2 μL of the sedimented phase was injected into a GC equipped with a flame ionization detector. Several parameters affecting this process were investigated and optimized. Under the optimal conditions, LODs ranged from 0.02 to 0.05 μg/L, a linear dynamic range of 0.1–100 μg/L and relative SDs in the range of 4.4–10.7% were attained. Very high preconcentration factors ranging from 3895–7222 were achieved. The applicability of the method for the extraction of BZPs from different types of complicated matrices, such as tap water, fruit juices, and urine samples, was studied. The obtained results reveal that the proposed method is a good technique for the extraction and determination of BZPs in complex matrices.     

Development and reproducibility of a novel high‐performance liquid‐chromatography monolithic column method for the detection and quantification of trans‐indolyl‐3‐acryloylglycine in human urine

Elevated levels of trans‐indolyl‐3‐acryloylglycine (IAcrGly) have been reported in the urine of people with various conditions including pervasive developmental disorders (PDDs) such as autism and Asperger syndrome. Reversed‐phase high‐performance liquid chromatography with ultra‐violet detection using traditional particle silica‐based columns subsequent to solid‐phase extraction (SPE) has been the preferred assay method; requiring long analytical run times, high flow rates and high solvent usage. Recent developments in monolithic HPLC column technology facilitated the development of a novel analytical method, for the detection and quantification of urinary IAcrGly. The revised method eliminates the requirement for SPE pre‐treatment, reduces sample run‐time and decreases solvent volumes. Five urine samples from people diagnosed with PDD were run in quadruplicate to test the intra‐ and inter‐day reliability of the new method based on retention time, peak area and peak height for IAcrGly. Detection was by UV with IAcrGly confirmation by MS/MS‐MS. Relative standard deviations showed significant improvement with the new method for all parameters. The new method represents a major advancement in the detection and quantification of IAcrGly by reducing time and cost of analysis whilst improving detection limits and reproducibility. Copyright © 2009 John Wiley & Sons, Ltd.     

Separation, pre-concentration, and HPLC analysis of methylxanthines in urine samples

An SPE method, using RP18 phases, for the simultaneous extraction of caffeine, theobromine, theophylline, paraxanthine, 1-methylxanthine, 3-methylxanthine, 7-methylxanthine, 1-methyluric acid, 1,3-dimethyluric acid, 1,7-dimethyluric acid, and 1,3,7-trimethyluric acid from urine has been developed. Besides a gradient HPLC system for the analysis of the compounds of interest on a LiChrosorb RP-18 (7 microm) column with mobile phase containing 0.05% aq. solution of trifluoroacetic acid and acetonitrile has been elaborated. The procedure has been successfully applied to the analysis of methylxanthines and methyluric acids in urine of patients with chronic asthma treated with theophylline and in urine of healthy subjects.     

Development of a molecularly imprinted solid‐phase extraction sorbent for the selective extraction of telmisartan from human urine

A novel molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed for the selective extraction of telmisartan from human urine. Molecularly imprinted polymers were prepared by a noncovalent imprinting approach through UV‐radical polymerization using telmisartan as a template molecule, 2‐dimethylamino ethyl methacrylate as a functional monomer, ethylene glycol dimethacrylate as a cross‐linker, N,N‐azobisisobutyronitrile as an initiator, chloroform as a porogen. Molecularly imprinted polymers and nonimprinted control polymer sorbents were dry‐packed into solid‐phase extraction cartridges, and eluates from cartridges were analyzed using a spectrofluorimeter. Limit of detection and limit of quantitation values were 11.0 and 36.0 ng/mL, respectively. A very high imprinting factor (16.1) was achieved and recovery values for the telmisartan spiked in human urine were in the range of 76.1–79.1%. In addition, relatively low within‐day (0.14–1.6%) and between‐day (0.11–1.31%) precision values were obtained. Valsartan was used to evaluate the selectivity of sorbent as well. As a result, a sensitive, selective, and simple molecularly imprinted solid‐phase extraction with spectrofluorimetry method has been developed and successfully applied to the direct determination telmisartan in human urine.     

Preconcentration of indapamide from human urine using molecularly imprinted solid‐phase extraction

A simple, sensitive, and selective molecularly imprinted solid‐phase extraction and spectrophotometric method has been developed for the clean‐up and preconcentration of indapamide from human urine. Molecularly imprinted polymers were prepared by a non‐covalent imprinting approach using indapamide as a template molecule, 2‐(trifluoromethyl) acrylic acid as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, N,N‐azobisisobutyronitrile as a thermal initiator and acetonitrile as a porogenic solvent. A non‐imprinted polymer was also prepared in the same way, but in the absence of template. Molecularly imprinted polymer and non‐imprinted polymer sorbents were dry‐packed into solid‐phase extraction cartridges. Eluates from cartridges were analyzed using a spectrophotometer for the determination of indapamide by referring to the calibration curve in the range 0.14–1.50 μg/mL. Preconcentration factor, limit of detection, and limit of quantification were 16.30, 0.025 μg/mL, and 0.075 μg/mL, respectively. A relatively high imprinting factor (9.3) was also achieved and recovery values for the indapamide spiked into human urine were in the range of 80.1–81.2%. In addition, relatively low within‐day (0.17–0.42%) and between‐day (1.1–1.4%) precision values were obtained as well. The proposed molecularly imprinted solid‐phase extraction and spectrophotometric method was successfully applied to selective extraction, preconcentration, and determination of indapamide from human urine samples.     

Solid phase extraction for removal of matrix effects in lipophilic marine toxin analysis by liquid chromatography-tandem mass spectrometry

The potential of solid phase extraction (SPE) clean-up has been assessed to reduce matrix effects (signal suppression or enhancement) in the liquid chromatography-tandem mass spectrometry (LC–MS/MS) analysis of lipophilic marine toxins. A large array of ion-exchange, silica-based, and mixed-function SPE sorbents was tested. Polymeric sorbents were found to retain most of the toxins. Optimization experiments were carried out to maximize recoveries and the effectiveness of the clean-up. In LC–MS/MS analysis, the observed matrix effects can depend on the chromatographic conditions used, therefore, two different HPLC methods were tested, using either an acidic or an alkaline mobile phase. The recovery of the optimized SPE protocol was around 90% for all toxins studied and no break-through was observed. The matrix effects were determined by comparing signal response from toxins spiked in crude and SPE-cleaned extracts with those derived from toxins prepared in methanol. In crude extracts, all toxins suffered from matrix effects, although in varying amounts. The most serious effects were observed for okadaic acid (OA) and pectenotoxin-2 (PTX2) in the positive electrospray ionization mode (ESI⁺). SPE clean-up on polymeric sorbents in combination with the alkaline LC method resulted in a substantial reduction of matrix effects to less than 15% (apparent recovery between 85 and 115%) for OA, yessotoxin (YTX) in ESI⁻ and azaspiracid-1 (AZA1), PTX2, 13-desmethyl spirolides C (SPX1), and gymnodimine (GYM) in ESI⁺. In combination with the acidic LC method, the matrix effects after SPE were also reduced but nevertheless approximately 30% of the matrix effects remained for PTX2, SPX1, and GYM in ESI⁺. It was concluded that SPE of methanolic shellfish extracts can be very useful for reduction of matrix effects. However, the type of LC and MS methods used is also of great importance. SPE on polymeric sorbents in combination with LC under alkaline conditions was found the most effective method.     

CE‐ECL detection of gatifloxacin in biological fluid after clean‐up using SPE

A simple, rapid and sensitive CE method has been proposed for the determination of gatifloxacin in biological fluid. This method is based on the ECL reaction of gatifloxacin and tris(2,2'‐bipyridyl)ruthenium(II) occurred in the end‐column detection cell. Under the optimal conditions, gatifloxacin can be assayed within 10 min over the concentration range of 5.0×10^?8?5.0×10^?6 g/mL with the theoretical plate numbers of 18 000. The intra‐day and inter‐day precision of the signal intensity and the migration time shows acceptable reproducibility for the analysis of gatifloxacin. The presented method has been successfully applied to determine the concentrations of gatifloxacin in urine and blood samples after clean‐up using C₁₈ SPE column.     

Investigation of commercial sorbents for the analysis of opioid peptides in human plasma by on‐line SPE‐CE

In this study, we investigated the performance of several commercial sorbents (Sep‐pack^® C18, ^tC18, C8 and ^tC2, Oasis^® HLB, Isolute^® ENV+, Strata^?‐X and Oasis^® MCX) for the determination of opioid peptides by solid‐phase extraction coupled on‐line to capillary electrophoresis (SPE‐CE). First, standard solutions were analyzed in order to achieve the lowest LOD and the best electrophoretic separations using UV detection. The best results were obtained using C18, C8 and ^tC2 sorbents, which were examined for the analysis of spiked human plasma samples. A double‐step sample clean‐up pretreatment, which consisted of precipitation with acetonitrile and filtration, was needed to prevent saturation of the on‐line SPE microcartridge. The filtration step was critical to obtain optimum analyte recovery and to clean up the sample matrix. A range of centrifugal filters and filtration conditions were tested and the recoveries of the sample pretreatment were evaluated by CE‐ESI‐MS. The LODs attained through SPE‐CE‐UV were approximately ten‐fold better with C18 than with C8 and ^tC2. The 0.1 μg/mL LODs achieved by C18‐SPE‐CE‐UV were further improved until we could detect 1 ng/mL concentrations of opioid peptides in plasma samples by C18‐SPE‐CE‐ESI‐MS, due to the outstanding selectivity of the MS detection.     

Simultaneous Determination of Caffeine and Theophylline in Human Plasma with a Weak Cation Monolithic SPE-column

A simple reversed‐phase high performance liquid chromatography (RP‐HPLC) method was developed to determine the level of caffeine and theophylline in human plasma samples. The sample clean‐up step involved the on‐line solid‐phase extraction (SPE) of the analytes from plasma samples into a weak cation monolithic column using a column switching system. Separation was performed on a C₁₈ column (5 µm, 150 mm×4.6 mm) with ultraviolet detection at 274 nm. The mobile phase consisted of methanol‐water (32/68, V/V) under isocratic conditions at a flow rate of 0.6 mL·min⁻¹. The measured concentration of caffeine and theophylline showed a good linear relationship over the concentrations range, 0.1–80.0 µg·mL⁻¹. The absolute recoveries ranged from 77.10% to 85.39%, and the inter‐day and intra‐day relative standard deviations (RSD) were all less than 5%. This method avoids a tedious pretreatment and provides an economic, repeatable and effective method for assaying trace drugs in biological samples.     

A rapid MCM‐41 dispersive micro‐solid phase extraction coupled with LC/MS/MS for quantification of ketoconazole and voriconazole in biological fluids

A rapid dispersive micro‐solid phase extraction (D‐μ‐SPE) combined with LC/MS/MS method was developed and validated for the determination of ketoconazole and voriconazole in human urine and plasma samples. Synthesized mesoporous silica MCM‐41 was used as sorbent in d ‐μ‐SPE of the azole compounds from biological fluids. Important D‐μ‐SPE parameters, namely type desorption solvent, extraction time, sample pH, salt addition, desorption time, amount of sorbent and sample volume were optimized. Liquid chromatographic separations were carried out on a Zorbax SB‐C₁₈ column (2.1 × 100 mm, 3.5 μm), using a mobile phase of acetonitrile–0.05% formic acid in 5 mm ammonium acetate buffer (70:30, v /v). A triple quadrupole mass spectrometer with positive ionization mode was used for the determination of target analytes. Under the optimized conditions, the calibration curves showed good linearity in the range of 0.1–10,000 μg/L with satisfactory limit of detection (≤0.06 μg/L) and limit of quantitation (≤0.3 μg/L). The proposed method also showed acceptable intra‐ and inter‐day precisions for ketoconazole and voriconazole from urine and human plasma with RSD ≤16.5% and good relative recoveries in the range 84.3–114.8%. The MCM‐41‐D‐μ‐SPE method proved to be rapid and simple and requires a small volume of organic solvent (200 μL); thus it is advantageous for routine drug analysis.     

A fully validated isotope dilution HPLC-MS/MS method for the simultaneous determination of succinylcholine and succinylmonocholine in serum and urine samples

A high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) method for the simultaneous detection of succinylcholine (SUX) and its metabolite succinylmonocholine (SMC) in serum and urine is presented. For internal standardization using isotope dilution, the deuterated compounds SUX-d(18) and SMC-d(3) were employed. Full validation was performed according to international guidelines. Solid-phase extraction (SPE) of acidified samples was accomplished using Strata-X polymeric reversed phase cartridges together with heptafluorobutyric acid (HFBA) as ion-pairing reagent. Separation was achieved within 13 min on a Phenomenex Synergi Hydro RP C18 column (4 microm, 150 x 2 mm) using a gradient of 5 mM ammonium formate buffer pH 3.5 and acetonitrile.To ensure the method's applicability in forensic as well as clinical toxicology, the specific demands of both research fields were taken into account, and the method was thus validated for a low and high concentration range. For both serum and urine as sample matrix, the validation revealed good intraday and interday precisions, consistently ranging below 15% for the lowest and below 10% for elevated concentrations. Accuracy was likewise good and never exceeded 10%. Extraction recovery was excellent, ranging between 88.1 and 103.9% for SUX and SMC in both tested matrices. Matrix effects were significant, the otherwise optimized extraction and detection methods, however, allowed for a very satisfactory sensitivity of the described method: For serum, the limits of detection and quantitation were determined to be 1.9 and 6.0 ng/ml for SUX, as well as 2.5 and 8.6 ng/ml for SMC, respectively; for urine, the corresponding values were established to be 1.4 and 4.0 ng/ml (SUX), as well as 1.5 and 4.9 ng/ml (SMC).The presented method was successfully applied to authentic samples of two forensic cases investigated in the institute of forensic medicine in Bonn, allowing the diagnosis of SUX intoxications.     

HPLC‐MS/MS analysis of anthocyanins in human plasma and urine using protein precipitation and dilute‐and‐shoot sample preparation methods,respectively

A high‐performance liquid chromatography tandem–mass spectrometry (HPLC‐MS/MS) method has been developed to analyze anthocyanins in urine and plasma to further understand their absorption, distribution, metabolism and excretion. The method employed a Synergi RP‐Max column (250 × 4.6 mm, 4 μm) and an API 4000 mass spectrometer. A gradient elution system consisted of mobile phase A (water–1% formic acid) and mobile phase B (acetonitrile) with a flow rate of 0.60 mL/min. The gradient was initiated at 5% B, increased to 21% B at 20 min, and then increased to 40% B at 35 min. The analysis of anthocyanins presents a challenge because of the poor stability of anthocyanins during sample preparation, especially during solvent evaporation. In this method, the degradation of anthocyanins was minimized using protein precipitation and dilute‐and‐shoot and sample preparation methods for plasma and urine, respectively. No interferences were observed from endogenous compounds. The method has been used to analyze anthocyanin concentrations in urine and plasma samples from volunteers administered saskatoon berries. Cyanidin‐3‐galactoside, cyanidin‐3‐glucoside, cyanidin‐3‐arabinoside, cyanidin‐3‐xyloside and quercetin‐3‐galactoside, the five major flavonoid components in saskatoon berries, were identified in plasma and urine samples.