Mixed Solid Phase Research Articles

Antisolvent crystallization of rare earth sulfate hydrates: Thermodynamics, kinetics and impact of iron

The thermodynamics and kinetics of ethanol antisolvent crystallization of rare earths from sulfate solutions has been explored, with a view towards separating the rare earths as part of a NdFeB magnet recycling process. The solubility of single and binary metal (Nd, Pr, Fe) phases in aqueous ethanol solutions has been determined. The impact of Fe and Pr on the crystallization of Nd is evaluated, the oxidation kinetics of Fe(II) to Fe(III) quantified, and the influence of Fe oxidation state on the thermodynamics and kinetics of crystallization investigated. Oxidation to Fe(III) is slow, with a half life of approx. 600 h. For pure Nd, the solubility of the obtained, stable sulphate octahydrate decreases exponentially with increased molar organic:aqueous (O/A) ratio, and is well described by the OLI model until O/A=0.2. Pr crystallizes as an isostructural octahydrate with similar solubility. Fe(II) precipitates as a mixed solid phase, with a solubility approximately 40 times higher than the rare earths at O/A=0.2. Fe(III) solutions exhibit liquid–liquid phase separation without precipitation at all evaluated concentrations. Nd and Pr coprecipitate together in proportion to their relative concentrations, with Pr precipitating at concentrations well below its pure component solubility. Fe(II) does not precipitate with Nd at O/A≤0.2 even at high concentration, with significant precipitation as separate particles at higher O/A for all concentrations. The crystallization kinetics and the morphology of the Nd phase is affected by the Fe oxidation state. The work highlights the potential of antisolvent crystallization for selective and efficient separation of REE from Fe.

Enrichment of Terbium(III) under synergistic effect of biosorption and biomineralization by Bacillus sp. DW015 and Sporosarcina pasteurii.

A weak microbially induced calcium carbonate precipitation (MICP) promotes the enrichment of Tb(III) by bacteria, while a strong MICP leads to the release of Tb(III). However, existing explanations cannot elucidate these mechanisms. In this study, the morphology of the bioprecipitation and the degree of Tb(III) enrichment were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The data revealed that MICP could drive stable attachment of Tb(III) onto the cell surface, forming a Tb-CaCO3 mixed solid phase. Excessive rapid rate of calcite generation could disrupt the Tb(III) adsorption equilibrium, leading to the release of Tb(III). Therefore, in order for Tb(III) to be stably embedded in calcite, it is necessary to have a sufficient number of adsorption sites on the bacteria and to regulate the rate of MICP. This study provides theoretical support for the process design of MICP for the enrichment of rare earth ions.

Determination of Ten Plant Growth Regulators in Bean Sprouts by Mixed Solid Phase Extraction Columns Separation and LC-MS/MS

(1) Background: Plant growth regulators (PGRs) can accelerate growth or improve the quality and quantity of bean sprouts but are forbidden to use in bean sprout cultivation, as the sprouting process’s increased chemicals will disturb the PGRs analysis. This article aimed to increase the accuracy and level of sensitivity of the LC-MS/MS method for the simultaneous analysis of 10 PGRs after mixed solid phase extraction (SPE) purification. (2) Methods: An LC-MS/MS detection method for 10 kinds of PGRs was established based on ESI ionization in the positive ion mode for 6-furfurylaminopurine (6-KT), paclobutrazol (PBZ), indole-2-acetic acid (IAA), and indole-3-butyric acid (IBA) and in the negative ion mode for gibberellin A3 (GA3), 2,4-dichlorophenoxy acetic acid (2,4-D), 4-chlorophenoxyacetic acid (4-CPA), forchlorfenuron (FCF), thidiazuron (TDZ), and 6-benzyl adenine (6-BA). (3) Results: The 10 PGR compounds were detected within a concentration range of 1.0–50 ng/mL. The average recovery was 68.3–97.3% with relative standard deviations (RSD) of 4.6–15.2% (n = 6); the limit of detection (LOD) and limit of quantification (LOQ) were found to be 2 and 5 ng/g, respectively. PGRs were surveyed in 36 soybean sprouts and 33 mungbean sprouts; the results showed that 4-CPA and IAA were detected in 10 soybean sprouts and 10 mungbean sprouts, respectively. Five samples contained both 4-CPA and IAA. (4) Conclusions: The established method is simple, rapid, accurate, and highly sensitive for the detection of PGR residues in bean sprout products.

Magnetic solid phase extraction of Sunitinib malate in urine samples assisted with mixed hemimicelle and spectrophotometric detection

The mixed hemimicelle-based solid phase extraction method using the coated sodium dodecyl sulfate by magnetic iron oxide nanoparticles as adsorbent was developed for extraction and determination of Sunitinib malate in real samples prior to determination by UV–Visible spectrophotometry. For the characterization of synthesized nanoparticles, Fourier transform infrared spectroscopy, and scanning electron microscopy was used. The influences of different factors affecting the extraction efficiency of Sunitinib malate, including the pH, the adsorbent amount, the volume and eluent type, the amount of the surfactant, the ionic strength, extraction, and desorption time, were investigated. At the optimized conditions, a good linearity with correlation coefficients of 0.998 and 0.999 was obtained over the concentration ranges of 1–22 and 1–19 µg/mL for water and urine samples, in order. The good recoveries of 97% and 99% and also, the limits of detection equal with 0.9, and 0.8 µg/mL for water and urine samples were enhanced, respectively. These results demonstrate that mixed hemimicelle solid phase extraction is a fast, efficient, economical and selective sample preparation method for the extraction and determination of Sunitinib malate in different water and urine sample solutions.

Pollution, Exposure and Risk of Biogenic Amines in Canned Sea Fish: Classification of Analytical Methods Based on Carbon Spheres QuEChERS Extraction Combined with HPLC.

This study investigated the pollution characteristics, exposure levels and health risk assessments of seven kinds of biogenic amines (BAs) in eight varieties of canned sea fish products (n = 131) on the Chinese market. Carbon spheres QuEChERS mixed dispersion solid phase extraction combined with HPLC was used for the classification and analysis of batch samples. The average recovery of single BAs obtained by this method is 92.3~97.7%, and the relative standard deviation is 1.9~4.8%. Different varieties of samples have different degrees of pollution, the mass concentration of single BAs range 0.45~27.74 mg/kg, and the total concentration of ΣBAs range 18.77~368.50 mg/kg, of which the concentration of Σ4BAs range 11.53~368.50 mg/kg. The composition of four BAs is mainly putrescine, cadaverine, histamine and tyramine, which always play an important role in the exposure level and risk assessment of samples. The exposure level of BAs in the human body ranges 67.03~209.52 μg∙kg−1∙d−1. The health risk assessment shows that the gender trend of exposure risk level of BAs is male > female (young age), female > male (middle and old age), the age trend is young age > old age > middle age, and the regional trend is city > countryside. The food safety index of BAs in samples is 0.0062~0.0195, which is far less than 1, so the risk is within the controllable range.

Mixed Hemimicelles Solid phase Extraction of Atrazine and Simazine from Environmental Water Samples Using Alumina-Coated Magnetite Composite Material

Mixed Hemimicelles Solid phase Extraction of Atrazine and Simazine from Environmental Water Samples Using Alumina-Coated Magnetite Composite Material

Magnetic nano-carbon core shell as potent mixed hemimicelle solid phase extraction strategy for determination of acrylamide from potato chips coupled by high-performance liquid chromatography

Magnetic nano-carbon core shell was applied as mixed hemimicelle magnetic solid phase extraction adsorbent to introduce a novel sample preparation method for determination of acrylamide from potato chips. Acrylamide is identified as neurotoxic, a probable human carcinogen (group 2A) compound. Effective extraction parameters such as type and amount of extracting solvent, type and amount of adsorbent, time of extraction and desorption, the effect of pH, time of ionic liquid loading on the adsorbent and stirring rate (rpm) were studied and optimized. Under optimized extraction conditions, a good linearity was observed in the concentration range of 100–1500 ng/g. Limit of detection was observed as 30 ng/g. Application of the proposed method was surveyed by analysis of some potato chips brands available in the local supermarkets. The satisfactory results with the recovery of 95.58% revealed that the proposed method could be applied in food analysis laboratories.

Distribution of synthetic opioids in postmortem blood, vitreous humor and brain

In the US, the use of synthetic opioids (e.g. fentanyl and derivatives) has become an increasing health issue with thousands of overdose deaths being observed since 2013. With the high mortality rate associated with these substances, postmortem analyses and interpretation of synthetic opioids has become extremely important. However, due to the novelty of these compounds, the available data are limited and provides challenges to toxicologists. The objectives of this study were (1) to develop and validate analytical methods for the determination of synthetic opioids in vitreous humor and brain, and (2) to investigate the postmortem distribution of new synthetic opioids in blood, vitreous humor, and brain tissue. Vitreous humor (0.5mL) and brain tissue (5g) homogenized in water (diluted 1:3, w/w) were extracted by mixed mode cation exchange-reversed phase solid phase extraction. Extracts were analyzed by liquid chromatography tandem mass spectrometry (LC–MSMS). The chromatographic separation was performed by reversed-phase with 0.1% formic acid in water and in acetonitrile as mobile phases in gradient mode, with a total run time of 21min. Data were acquired with ESI+ in dynamic multiple reaction mode (dMRM), monitoring 2 transitions per compound. The methods were succesfully validated following SWGTOX guidelines, with limits of quantification of 0.1ng/mL in vitreous humor and 0.1ng/g in brain. Fifty-eight authentic case samples from the New York City Office of the Chief Medical Examiner (NYC-OCME) were analyzed to assess the distribution and detectability of synthetic opioids in these postmortem samples. Of the fifteen synthetic opioids included in the method, six synthetic opioids and metabolites (4-ANPP, acetylfentanyl, fentanyl, furanylfentanyl, norfentanyl, U-47700) were detected in the authentic cases. Concentrations for most analytes were within the 0.1 to 100ng/mL or ng/g calibration range across all three matrices, with only concentrations from acetylfentanyl and U-47700 exceeding 100ng/mL or ng/g. The highest concentrations were observed in brain (except norfentanyl), followed by blood and vitreous humor. Most analytes were detected in all three matrices in a given case. This was followed by detection of an analyte in combinations of brain and another matrix or brain only. Through the case analyses, vitreous humor and brain demonstrated to be viable alternatives to blood when performing postmortem analyses of synthetic opioids. Brain exhibited a higher detectability for most analytes when compared to blood and vitreous humor.

Mixed hemimicelles solid phase extraction based on sodium dodecyl sulphate-coated nano-magnets Fe3O4 for the simultaneous separation and preconcentration of cobalt and nickel

A simple nano-sized magnetic particles solid phase extraction (MSPE) was developed for simultaneous extraction and preconcentration of cobalt and nickel in water and food samples prior to their determination by flame atomic absorption spectrometry. This method was based on the reaction of trace amounts of cobalt and nickel from aqueous solutions with 2-nitroso-1-naphthol and adsorption of formed complexes on sodium dodecyl sulphate-coated Fe3O4 nanoparticles (NPs). The crucial factors affecting the efficiency of the developed method such as pH and amount of surfactant were optimized. The detection limits of the developed method were 0.09 and 0.40 μg L−1 (300.0 mL of samples), for Ni(II) and Co(II), respectively. The relative standard deviations were 2.3 and 2.4% for six replicate measurements of Ni (10.0 μg L−1) and Co (5.0 μg L−1). The method was successfully applied for the determination of cobalt and nickel in spinach, tea and water samples.

Study of Cr(VI) adsorption onto magnetite nanoparticles using synchrotron-based X-ray absorption spectroscopy

In this study, the efficiency of Cr(VI) adsorption onto nano-magnetite was examined by batch experiments, and the Cr(VI) adsorption mechanism was investigated using synchrotron-based X-ray absorption spectroscopy. Magnetite nanoparticles with a mean diameter of 10 nm were synthesized using an inexpensive and simple co-precipitation method. It shows a saturation magnetization of 54.3 emu/g, which can be recovered with an external magnetic field. The adsorption data fitted the Langmuir adsorption isotherm well, implying a monolayer adsorption behavior of Cr(VI) onto nano-magnetite. X-ray absorption spectroscopy results indicate that the adsorption mechanism involves electron transfer between Fe(II) in nano-magnetite (Fe2+OFe3+2O3) and Cr(VI) to transform into Cr(III), which may exist as an Fe(III)–Cr(III) mixed solid phase. Moreover, the Cr(III)/Cr(VI) ratio in the final products can be determined by the characteristic pre-edge peak area of Cr(VI) in the Cr K-edge spectrum. These findings suggest that nano-magnetite is effective for Cr(VI) removal from wastewater because it can transform highly poisonous Cr(VI) species into nontoxic Cr(III) compounds, which are highly insoluble and immobile under environmental conditions.

Novel Two-Dimensional Liquid Chromatography–Tandem Mass Spectrometry for the Analysis of Twenty Antibiotics Residues in Dairy Products

A novel two-dimensional hydrophilic interaction chromatography/reversed phase liquid chromatography–tandem mass spectrometry system was developed to analyze seven categories of antibiotics residues in dairy products. The seven categories were β-lactams, tetracyclines, macrolides, aminoglycosides, amphenicols, quinolones, and sulphonamides, and involved 20 antibiotics. Samples of milk powder or milk samples were extracted by mixed matrix solid phase dispersion using C18 and CN material. The analytes were eluted by acetonitrile and water, and were dried with rotary evaporation. Finally, the residues were dissolved with mobile phase and then analyzed. Under sample pretreatment conditions, chromatographic and mass spectrometric parameters were optimized. Twenty analytes showed good linearities with correlation coefficients of 0.9945 ~ 0.9998. The limits of detection and quantification for milk powder and milk samples were 0.10 ~ 2.40 and 0.33 ~ 7.92 μg/kg, respectively. The proposed method has been applied to the determination of antibiotics residues in milk powder and milk samples.

Mixed hemimicelles solid-phase extraction of cephalosporins in biological samples with ionic liquid-coated magnetic graphene oxide nanoparticles coupled with high-performance liquid chromatographic analysis

A novel mixed hemimicelles solid phase extraction based on magnetic graphene oxide (Fe3O4/GO) and ionic liquid (IL) was developed for the simultaneous extraction and determination of trace cephalosporins in spiked human urine. The high surface area and excellent adsorption capacity of the graphene oxide after modification with1-hexadecyl-3-methylmidazoliumbromide(C16mimBr) were utilized adequately in the solid phase extraction(SPE) process. A comprehensive study of the parameters affecting the extraction recovery, such as the zeta-potential of magnetic graphene oxide, amounts of magnetic graphene oxide and surfactant, pH of solution, ionic strength, extraction time, and desorption condition were optimized. A comparative study on the use of different surfacant-coated Fe3O4/GO NPs as sorbents was presented. Good linearity (R2>0.9987) for all calibration curves was obtained. The LODs were ranged between 0.6 and 1.9ng mL−1 for the cephalosporins and the LOQs were 1.5 to 5.5, respectively. Satisfactory recoveries(84.3% to 101.7%)and low relative standard deviations from 1.7% to 6.3% in biological matrices were achieved. The mixed hemimicelles magnetic SPE (MSPE) method based on ILs and Fe3O4/GO NPs magnetic separation has ever been successfully used for pretreatment of complex biological samples.

Quantitative Relationship between Monolayer Domain Structure and Interfacial Shear Rheology

With micro-disc rheometry, we have been able to map out the viscosity of dipalmitoylphosphatidylcholine monolayers, and determine how the viscosity changes with additions of cholesterol and/or palmitic acid, which are common additives to clinical lung surfactants. We find that 1-3 wt% cholesterol (similar to that found in Infasurf, a clinical replacement surfactant) induces a two-three order of magnitude drop in the interfacial rheology. This drop correlates very well with the decrease in molecular coherence of the DPPC lattice as measure with synchrotron X-ray diffraction when used in a free-area model of the viscosity. However, palmitic acid induces a two order of magnitude increase in the viscosity of DPPC which is only partly correlated with the increase in molecular coherence of DPPC. Instead, a better explanation of the effects of PA on DPPC is the formation of a highly organized, low tilt phase that is about 1:1 DPPC:PA that appears at low surface pressure. For mixtures in which the PA fraction is below equimolar, we obtain a mixed solid phase of the 1:1 DPPC:PA cocrystal and a liquid phase of nearly pure DPPC. This phase separation is exacerbated by the presence of cholesterol, which segregates to the liquid phase. As the surface pressure increases, a second crystal forms of nearly pure DPPC. This is accompanied by a dramatic change in the rate of change of the surface viscosity vs surface pressure. This solid-solid phase coexistence is likely common in many complex biological monolayers.

Development of a novel mixed hemimicelles dispersive micro solid phase extraction using 1-hexadecyl-3-methylimidazolium bromide coated magnetic graphene for the separation and preconcentration of fluoxetine in different matrices before its determination by fiber optic linear array spectrophotometry and mode-mismatched thermal lens spectroscopy

This study aims at developing a novel, sensitive, fast, simple and convenient method for separation and preconcentration of trace amounts of fluoxetine before its spectrophotometric determination. The method is based on combination of magnetic mixed hemimicelles solid phase extraction and dispersive micro solid phase extraction using 1-hexadecyl-3-methylimidazolium bromide coated magnetic graphene as a sorbent. The magnetic graphene was synthesized by a simple coprecipitation method and characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The retained analyte was eluted using a 100 μL mixture of methanol/acetic acid (9:1) and converted into fluoxetine-β-cyclodextrin inclusion complex. The analyte was then quantified by fiber optic linear array spectrophotometry as well as mode-mismatched thermal lens spectroscopy (TLS). The factors affecting the separation, preconcentration and determination of fluoxetine were investigated and optimized. With a 50 mL sample and under optimized conditions using the spectrophotometry technique, the method exhibited a linear dynamic range of 0.4–60.0 μg L−1, a detection limit of 0.21 μg L−1, an enrichment factor of 167, and a relative standard deviation of 2.1% and 3.8% (n = 6) at 60 μg L−1 level of fluoxetine for intra- and inter-day analyses, respectively. However, with thermal lens spectrometry and a sample volume of 10 mL, the method exhibited a linear dynamic range of 0.05–300 μg L−1, a detection limit of 0.016 μg L−1 and a relative standard deviation of 3.8% and 5.6% (n = 6) at 60 μg L−1 level of fluoxetine for intra- and inter-day analyses, respectively. The method was successfully applied to determine fluoxetine in pharmaceutical formulation, human urine and environmental water samples.

Mixed solid phase model using equation of state based on hole-theory for solubility prediction of pharmaceutical compound in supercritical CO2

A mixed solid phase model using an equation of state based on hole-theory is developed for solubility calculation in supercritical CO2 considering the dissolution of CO2 into solid phase at high-pressure condition. Parameters in the equation of state were obtained from the molecular information calculated by a quantum calculation based on conductor-like screening model (COSMO). Twenty-three species of pharmaceutical compounds are mentioned as the target for the correlation or prediction of solubility in supercritical CO2. The predicted results of the solubility in supercritical CO2 by the mixed solid phase model are compared with those by the conventional pure solid phase model. It is found that the results for the pharmaceutical compounds with S, N, F, Cl and I atoms using the mixed solid phase model give the calculation performance better than those of the pure solid phase model. The mixed solid phase model was also applied for calculation of the CO2 solubility in solid phase.

Simultaneous and enantioselective determination of cis-epoxiconazole and indoxacarb residues in various teas, tea infusion and soil samples by chiral high performance liquid chromatography coupled with tandem quadrupole-time-of-flight mass spectrometry

A novel and sensitive method for simultaneous enantiomeric analysis of two pesticides—cis-epoxiconazole and indoxacarb—in various teas, black tea infusion, and soil samples has been developed. The samples were initially subjected to acetonitrile extraction followed by cleanup using lab-made florisil/graphitized carbon black mixed solid phase extraction (SPE) column (for the different teas and soil samples) and a BondElut C18-SPE column (for the black tea infusion samples). Separation of the analytes was performed on a chiral stationary phase using high performance liquid chromatography (HPLC) under a reversed-phase isocratic elution mode followed by tandem quadrupole time-of-flight mass spectrometry (Q-TOF/MS) detection. The mobile phase components, mobile phase ratios, flow rates, column temperatures, and MS parameters were all optimized to reach high sensitivity and selectivity, good peak shape, and satisfactory resolution. The performance of the method was evaluated based on the sensitivity, linearity, accuracy, precision, and matrix effects. Under optimal conditions, for the various teas (green tea, black tea, and puer tea), fresh tea leaf, soil and black tea infusion samples spiked at low, medium, and high levels, the mean recoveries for the four enantiomers ranged from 61.0% to 129.7% with most relative standard deviations (RSDs) being 17.1% or below. Good linearity can be achieved with regression coefficients (R) of 0.9915 or above for all target enantiomers, and matrix-matched calibration concentration ranging from 5.0 to 1000μg/L. The limits of detection (LODs) for all four target enantiomers were 1.4μg/kg or below in the different teas and soil samples and 0.05μg/kg or below in the black tea infusion, whereas the limits of quantification (LOQs) for those did not exceed 5.0μg/kg and 0.2μg/L, respectively. The proposed method is convenient and reliable and has been applied to real tea samples screening. It has also been extended for studies on the degradation kinetics and environmental behaviors in the field trials, providing additional information for reliable risk assessment of these chiral pesticides.

Determination of ractopamine in pig hair using liquid chromatography with tandem mass spectrometric detection

A quantitative analytical procedure for the determination of ractopamine in pig hair has been developed and validated. The hair samples were washed and incubated at 75°C with isoxuprine and hair extraction buffer. The drug present was quantified using mixed solid-phase extraction and liquid chromatography with tandem mass spectrometric detection. The limit of quantization (LOQ) was 10pg/mg and the intra-day precision at 25pg/mg and 750pg/mg was 0.49% and 2.8% respectively. Inter-day precision was 0.88% and 3.52% at the same concentrations. The hair extraction percentage recovery at 25pg/mg and 50ng/mL was 99.47% and 103.83% respectively. The extraction percentage recovery at 25pg/mg and 50ng/mg was 93.52% and 100.26% respectively. Our results showed that ractopamine residues persist in hair in 24days of withdrawal and also showed the possibility to test ractopamine from pig hair samples.

Mixed hemimicelle solid-phase extraction based on magnetic carbon nanotubes and ionic liquids for the determination of flavonoids

A novel mixed hemimicelles solid phase extraction (SPE) based on magnetic carbon nanotubes (MCNTs) and ionic liquid (IL) is developed for the simultaneous extraction and determination of trace flavonoids in spiked human urine. In this novel SPE, the formation of C16mimBr with mixed hemimicelles on the surface of MCNTs@SiO2 nanoparticles (NPs) causes retention of analytes by strong hydrophobic, π–π and electrostatic interactions. This SPE technique combines the advantages of mixed hemimicelles and MCNTs. In order to establish the guidelines for the preparation of mixed hemimicelles on composite materials, different main factors affecting the preconcentration of analytes, such as material type, amount of surfactant, pH of solution, ionic strength, extraction time, desorption condition and regeneration property, were investigated and optimized. Under the selected conditions, the accuracy of the method was evaluated by recovery measurements on spiked samples, and good recoveries with low relative standard deviations from 3.5% to 4.9% were achieved. No interferences were caused by endogenous compounds in human urine. For our knowledge, this is the first development of a mixed hemimicelles SPE based on MCNTs and IL for the extraction of trace analytes in complex biological samples.

Systematic replacement of amides by 1,4-disubstituted[1,2,3]triazoles in Leu-enkephalin and the impact on the delta opioid receptor activity

Using Cu(I)-catalyzed azide–alkyne cycloaddition in a mixed classical organic phase and solid phase peptide synthesis approach, we synthesized four analogs of Leu-enkephalin to systematically replace amides by 1,4-disubstituted[1,2,3]triazoles. The peptidomimetics obtained were characterized by competitive binding, contractility assays and ERK1/2 phosphorylation. The present study reveals that the analog bearing a triazole between Phe and Leu retains some potency, more than all the others, suggesting that the hydrogen bond acceptor capacity of the last amide of Leu-enkephalin is essential for the biological activity of the peptide.

Simultaneous determination of melamine and cyanuric acid residues in water and urine by solid phase extraction-hydrophilic interaction liquid chromatography-electrospray tandem mass spectrometry method

We aimed to establish a sensitive quantified method for the simultaneous determination of melamine and cyanuric acid residues in water and urine by hydrophilic interaction liquid chromatography coupled with electrospray tandem mass spectrometry (HILIC-ESI-MS/MS) with the pretreatment of hydrophilic functional silica gel and cation exchange resin mixed solid phase extraction column(MCT), and to investigate the melamine and cyanuric acid residues in 501 water and 216 urine from several province and city. About 100 ml water (or 10 ml urine) was adjusted to pH 3.0 with concentrated hydrochloric acid, and then mixed with the internal standard solution((15)N3-melamine and (15)N3-(13)C3 -cyanuric acid) and 100 ml acetonitrile (10 ml for urine). The solution was cleaned with MCT solid-phase extraction column, and eluted once by 3 ml methanol and twice by 2.5 ml methanol (containing 5% ammonia water). The effluent was collected and dried by N2 flow at 40 °C, and then diluted to 2 mmol/L ammonium acetate containing 90% volume fraction acetonitrile. The completely dissolved solution was then filtered with 0.22 µm organic membrane; and the filtrate was detected by high performance liquid chromatography-tandem mass spectrometry and quantified with internal standards. The repeatability and sensitivity of the assay were evaluated. Then we detected the melamine and cyanuric acid residues in 501 water and 216 urine samples collected from several province and city. By the quantification of internal standard (15)N3-melamine and (15)N3-(13)C3-cyanuric acid, the melamine and cyanuric acid were linear in the range of 2.0-1000.0 µg/L with correlation coefficient of 0.9998 and 0.9997. The detection limits of the method were separately 0.4 ng/L (melamine) and 0.3 ng/L (cyanuric acid) for water, and 4.0 ng/L (melamine) and 3.0 ng/L (cyanuric acid) for urine. The average recovery rate was around 95.3%-100.1% with the relative standard deviation (RSD) was <4.02%. Out of the 501 water samples, melamine was detected out in 19.9% (100/501) and cyanuric acid was detected out in 5.2% (26/501). The content was around 0.03-5.00 g/L. Melamine or cyanuric acid was detected out in 24.5% of the urine samples (53/216), with the content around 0.01-1.00 g/L. The established method of solid phase extraction-hydrophilic interaction liquid chromatography-electrospray tandem mass spectrometry can satisfy the requirement for detection of melamine and cyanuric acid residues in all sorts of water and urine. Meanwhile, the two substances widely existed in water and Chinese population.