Development and validation of a multianalyte method for quantification of aflatoxins and bongkrekic acid in rice and noodle products using PRiME-UHPLC-MS/MS method.

An analytical method based on PRiME (process, robustness, improvements, matrix effects, ease of use) HLB purification followed by the ultra-high liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection has been developed for the determination aflatoxin B1, B2, G1 and G2 and bongkrekic acid in rice and noodle products. Five toxins were separated on a Waters BEH C18 column by gradient elution, scanned by ESI+ and ESI- dynamic switching and detected with MRM mode. LOD, LOQ, matrix effects, accuracy and precision of the developed method were investigated. Under the optimal sample pretreatment conditions, high sensitivity (LOQs: 0.20-0.40 µg/kg), good recoveries (80.5%-106.6%) and acceptable precision (2.4%-7.2%) were obtained for the analysis of the four aflatoxins and bongkrekic acid. This method was successfully applied to the analysis of rice and noodle products, demonstrating its applicability and suitability for the routine analysis of aflatoxins and bongkrekic acid in rice and noodle products.

Fragmentation pathway of hypophosphite (H2PO2-) in mass spectrometry and its determination in flour and flour products by LC-MS/MS.

The fragmentation pathway of H2PO2- in MS was obtained by Orbitrap HRMS and the reverse confirmation was carried out by the neutral loss detection experiment. The results showed that H2PO2- with even electron ion would produce the neutral loss of 2H and form a new even electron ion with a pair of lone-pair electrons. Based on this, a LC-MS/MS method was developed for the determination of H2PO2- in flour and flour products. The H2PO2- was separated on an Acclaim Trinity P1 composite ion exchange column, and then detected by MS/MS under MRM mode. Finally, the developed method was validated in terms of the linearity, selectivity, accuracy, precision and matrix effect. The method showed a good linearity (R2＞0.999) in the concentration range of 50 âˆ¼ 1500 µg/L. The LOD and LOQ for H2PO2- were 10.0 mg/kg and 30.0 mg/kg, respectively. The average recoveries and RSDs (n = 6) were 93.0%∼102.9% and 2.6 âˆ¼ 5.6%, respectively.

Banana-peel-derived magnetic porous carbon as effective adsorbent for the enrichment of six bisphenols from beverage and water samples.

Functionalized magnetic nanoporous carbon derived from banana peel was synthesized through carbonization, porogenesis, carboxylation and magnetization using banana peel and was successfully used as a magnetic solid phase extraction (MSPE) material for the enrichment of six bisphenols (BPs) from beverage and water samples. After the optimization of MSPE process, the enrichment factors of six target analytes were in the range of 74-112 for water samples, and 15-22 for beverage samples. Then, high-performance liquid chromatography-quadrupole-Orbitrap high-resolution mass spectrometry (HPLC-Q Orbitrap-HRMS) was used for the separation and determination of the target analytes. Results showed that the extraction recoveries for 6 BPs were in the range of 71.9-108.4% with an RSD of 2.5-7.5% (n = 6). These results demonstrated that the as-prepared material could efficiently enrich some aromatic compounds and the proposed method is reliable and robust for the determination of BPs in water and beverage samples.

Perchlorate occurrence in foodstuffs and water: Analytical methods and techniques for removal from water - A review.

Perchlorate (ClO4-), a type of contaminant with high diffusivity and durability, has been widely detected in water and foodstuffs, arousing a global concern. It can interfere with normal function of the human thyroid gland, affecting human health. Therefore, determination of perchlorate in water and foodstuffs, and removal from water are important. This review focuses on the occurrence of perchlorate, mainly in water and foodstuffs, and provides an overview of analytical methods for determination of perchlorate over the last two decades. In addition, merits and drawbacks of the various methods have been considered. This review also highlights the most commonly used approaches for removal of perchlorate from water. Finally, current trends and future perspectives in determination of perchlorate and removal from water are proposed. This review provided a comprehensive understanding of perchlorate occurrence and its removal from water, and had practical significance in reducing the harm of perchlorate to human.

Determination of bongkrekic acid and isobongkrekic acid in rice noodles by HPLC-Orbitrap HRMS technology using magnetic halloysite nanotubes.

The existing extraction and detection methods of bongkrekic acid (BKA) and isobongkrekic acid (IBKA) are complex, time-consuming and solvent-consuming. In this work, a simple and fast pre-concentration procedure based on Fe3O4/HNTs was developed for the determination of BKA and IBKA in rice noodles using HPLC-Orbitrap HRMS. The structure and morphology of Fe3O4/HNTs was characterized by means of XRD, SEM, FT-IR and VSM. Parameters affecting the extraction efficiency including adsorbent amount, pH, extraction time, type and volume of eluent were investigated by employing the response surface method. Results indicated that the proposed method had favorable linearity in the concentration range of 2-200 µg/L with a correlation coefficient >0.998. Method LOD and LOQ were 0.3 µg/kg and 1.0 µg/kg, respectively. Finally, the method was successfully applied to determine BKA and IBKA in rice noodle samples from southern China with recoveries ranging from 79.8% to 102.6% and relative standard deviation (RSD) of 4.2%-7.1%.

Fluorine and nitrogen functionalized magnetic graphene as a novel adsorbent for extraction of perfluoroalkyl and polyfluoroalkyl substances from water and functional beverages followed by HPLC-Orbitrap HRMS determination.

Most of the reported magnetic adsorbents are difficult to absorb multi-class of per- and polyfluoroalkyl substances (PFASs), especially the short-chain PFASs. In this work, a novel fluorine and nitrogen functionalized magnetic graphene (G-NH-FBC/Fe2O3) was first synthesized and characterized by scanning electron microscope (SEM), Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The as-prepared G-NH-FBC/Fe2O3 was utilized as adsorbents for the magnetic solid-phase extraction (MSPE) of 19 PFASs from water and functional beverages and showed excellent adsorption capacity probably due to the hydrophobic interaction. Under the optimal pretreatment and instrumental conditions, a selective and sensitive high performance liquid chromatography Orbitrap high resolution mass spectrometry (HPLC-Orbitrap HRMS) method was developed for the determination of PFASs. Results indicated that the proposed method had favorable linearity (R2 ≥ 0.994) within a wide range of concentrations. Limit of detection (LOD) and limit of quantification (LOQ) for the developed method ranged from 3 ng/L to 15 ng/L and 10 ng/L to 49 ng/L, respectively. Finally, the method was successfully applied to determine PFASs in drinking water, river water, tap water, factory drainage and functional beverages with recoveries ranging from 71.9% to 117.6% and relative standard deviation of <10%. The prepared G-NH-FBC/Fe2O3 was easy to recycle and could be reused for five times without significant decrease in extraction recoveries of PFASs. These results demonstrated that this novel magnetic G-NH-FBC/Fe2O3 could efficiently enrich PFASs and the proposed method is reliable and robust for the determination of PFASs in water and beverage samples.

High throughput analysis of 21 perfluorinated compounds in drinking water, tap water, river water and plant effluent from southern China by supramolecular solvents-based microextraction coupled with HPLC-Orbitrap HRMS.

The present work reported a high-throughput strategy for the analysis of 21 perfluorinated compounds (PFCs) in drinking water, tap water, river water and plant effluent from southern China by supramolecular solvent (SUPARS) vortex-mixed microextraction combined with high performance liquid chromatography-Orbitrap high resolution mass spectrometry (HPLC-Orbitrap HRMS). The SUPRAS without heating assistance is less solvent-consumption, meeting the requirements for green environmental protection and sustainable development. Parameters in the microextraction such as volume of dodecanol and tetrahydrofuran (THF), vortexing extraction and centrifugation time, salt concentration were investigated. The optimal extraction conditions were 250 µL of undecanol, 1.0 mL of THF and 20.0% (w/v, 4 g) NaCl. Under the optimum conditions, method limit of detection and method limit of quantitation in the ranges of 0.01-0.08 µg/L and 0.03-0.25 µg/L, good recoveries (72.5-117.8%) and intra-day precision (1.1-11.2%, n = 6), high enrichment factors (48-78) were obtained. The developed method was successfully applied for analysis of PFCs in 13 drinking water, tap water, river water and plant effluent samples collected from southern China. Perfluorobutane sulfonic acid was detected in one river water with concentration of 0.48 µg/L and 1H,1H,2H,2H-Perfluorooctane sulfonic acid was detected in one river water and two plant effluent samples with concentrations in the range of 0.14-0.67 µg/L.

Analysis of heterocyclic aromatic amine profiles in Chinese traditional bacon and sausage based on ultrahigh-performance liquid chromatography-quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap-HRMS).

Ultrahigh-performance liquid chromatography coupled to quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap-HRMS) was used for the screening and determination of 14 heterocyclic aromatic amines (HAAs) in Chinese traditional bacon and sausage. HAAs were extracted from samples using sodium hydroxide solution with acetonitrile, and purified by solid-phase extraction. UHPLC-Q-Orbitrap-HRMS acquired full MS data for quantification, and UHPLC-Q-Orbitrap-Full MS/dd-MS2 (i.e., data-dependent scan mode) obtained product ion spectra for identification. Quantification was achieved using matrix-matched standard calibration curves along with the use of isotope labeled standards as internal standards. Linearity was observed in the range of 0.2-500 µg/L for 14 HAAs, with determination coefficients (R2) greater than 0.997. Limits of detection and limits of quantification were in the ranges of 0.1-0.8 µg/kg and 0.3-2.5 µg/kg, respectively. UHPLC-Q-Orbitrap-HRMS demonstrated acceptable performance for quantification and confirmation of HAAs, while UHPLC-Q-Orbitrap-Full MS/dd-MS2 along with library matching showed great potential for screening and confirmation of unknown HAAs in meat products.

Quantitative analysis of fourteen heterocyclic aromatic amines in bakery products by a modified QuEChERS method coupled to ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS).

Heterocyclic aromatic amines (HAAs) are harmful by-products naturally formed during the heating process of foodstuffs. The present work reported an analytical method for HAAs analysis for the first time in bakery products by QuEChERS technique combined with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Bakery products were ultrasonically extracted with acetonitrile and sodium hydroxide solution (1 mmol/L). The obtained extracting solution was nearly dried under nitrogen stream and subsequently purified by QuEChERS technique using primary secondary amine (PSA) as adsorbents. Fourteen HAAs were separated on a C18 column with the mobile phase of a mixture of acetonitrile and 1 mmol/L ammonium acetate water solution (containing 0.04% acetic acid), and detected by MS/MS under multiple reaction monitoring (MRM) mode. The developed method was validated in terms of linearity, matrix effect, accuracy and precision. The method showed a good linearity (R2 > 0.999) for all analytes in their corresponding concentration ranges. The method limit of quantifications (LOQs, S/N = 10) of 14 HAAs were in the range of 0.3-4.5 µg/kg. The average recoveries (n = 6) at 3 spiked levels ranged from 62.8 to 96.8% with relative standard deviations (RSDs) of 1.2-7.6%. The validated method was applied in HAAs analysis in 20 bakery products and 4 kinds of HAAs (harman, norharman, AaC, PhIP) were detected with the concentrations ranging from 0.6 to 35.6 µg/kg.

Ice-bath assisted sodium hydroxide purification coupled with GC-MS/MS analysis for simultaneous quantification of ethyl carbamate and 12 N-nitrosoamines in yellow rice wine and beer.

Ethyl carbamate (EC) and N-nitrosoamines (NAs) are toxic contaminants which can be typically formed in fermented alcoholic beverages. In the present work, a novel approach for simultaneous analysis of EC and NAs in beer and yellow rice wine based on ice-bath assisted sodiumhydroxide purification and GC-MS/MS was firstly established. Samples were extracted with acetonitrile-ethyl acetate after addition of internal standards. The extraction solution system was purified by sodiumhydroxide solid under ice-bath. After concentration, target analytes were separated on a HP-INNOWAX quartz capillary column and determined under dynamic multiple reactions monitoring mode of MS/MS. The limits of detection and quantification (LOD and LOQ), matrix effect, recovery and precision of the method were evaluated. Results were linear in the concentration range 2-200 µg/L for all analytes of interest, with regression coefficients higher than 0.999. LODs and LOQs were in the ranges of 0.1-0.5 µg/kg and 0.5-1.5 µg/kg, respectively. The mean recoveries at three spiked levels were between 81.5% and 121.0%. The intra- and inter-day precisions were in the ranges of 2.2-9.4% and 1.6-7.9%, respectively. The validated method was successfully applied to determine thirteen targets in commercial beer and yellow rice wine. EC was detected in all beers and yellow rice wines with the concentrations ranging from 1.18 to 22.90 µg/L. Results indicated wide EC contamination and confirmed its urgency for monitoring EC in fermented alcoholic beverages.

Modified QuEChERS purification and Fe3O4 nanoparticle decoloration for robust analysis of 14 heterocyclic aromatic amines and acrylamide in coffee products using UHPLC-MS/MS.

Based on QuEChERS dispersed purification, Fe3O4 nanoparticle decoloration and UHPLC-MS/MS, a robust and sensitive method was established for simultaneous analysis of 14 heterocyclic aromatic amines (HAAs) and acrylamide (AA) in coffee products. Sample was extracted by 90% acetonitrile water (v/v), dispersed with primary secondary amine (PSA) and further purified with Fe3O4 nanoparticle. Then, 15 analytes were detected using ESI positive ion under MRM mode. Good linearity was observed for all analytes in the range of 0.2-100 µg/L with the determination coefficients being above 0.996. Limits of detection (S/N ≥ 3) and limits of quantification (S/N ≥ 10) were in the range of 0.02-0.15 µg/L and 0.2-0.7 µg/L, respectively. The intra-day average recoveries were between 81.6% and 100%, and the intra-day precisions ranged from 4.3% to 9.0%. The inter-day average recoveries were in the range of 81.0-101% with precisions ranging from 5.0% to 7.8%. Results indicated that the combination of PSA and Fe3O4 exhibited superior purification and adsorption effects for removing pigments and acid compounds. Real samples analysis indicated that coffee products were widely contaminated with AA, harman and norharman.

Development and comparison of single-step solid phase extraction and QuEChERS clean-up for the analysis of 7 mycotoxins in fruits and vegetables during storage by UHPLC-MS/MS.

A robust and sensitive UHPLC-MS/MS method was developed for the analysis of seven mycotoxins in fruits and vegetables. The variations of seven mycotoxins concentrations during storage were also determined for the first time. Solid phase extraction (SPE) and QuEChERS clean-up were compared, and extraction was finally performed with acetonitrile under acidic conditions followed by HLB SPE purification. Seven mycotoxins were separated on a C18 column by gradient elution, scanned by ESI+ and ESI- dynamic switching and detected with MRM mode. LOD and LOQ, matrix effect, accuracy and precision of the developed method were investigated. Results were linear in their concentration ranges for all mycotoxins with R2 being greater than 0.999. LODs and LOQs were ranged from 0.05 to 3.0 µg/kg and 0.2 to 10.0 µg/kg, respectively. Average recoveries were between 81.1% and 116% with intraday- and interday-precision being in the ranges of 3.0-6.2% and 4.2-6.1%, respectively. The validated method provides sufficient selectivity, sensitivity and accuracy to screen for seven mycotoxins at trace levels, without using standard addition or matrix-matched calibration to compensate for matrix effects. The method was successfully applied for mycotoxins analysis in fruits and vegetables. None were detected in fresh samples, but AOH and AME were detected in strawberry, and TeA was detected in tomato fruits during long-term storage. Their concentrations were in the range of 3.6-165.3 µg/kg from 3 days to 60 days and significantly increased along with storage time.

A novel approach for simultaneous analysis of perchlorate (ClO4-) and bromate (BrO3-) in fruits and vegetables using modified QuEChERS combined with ultrahigh performance liquid chromatography-tandem mass spectrometry.

Perchlorate (ClO4-) and bromate (BrO3-) are mainly determined by ion chromatography methods. The present work aims to develop a modified QuEChERS combined with ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for simultaneous analysis of ClO4- and BrO3- in fruits and vegetables including cherry tomato, strawberry, tomato, potato, lettuce and pakchoi. Two target inorganic anions were separated on a Diamonsil C18(2) column by gradient elution, scanned in ESI negative mode and detected under multiple reactions monitoring (MRM). Limit of detection (LOD) and method limit of quantification (MLOQ), matrix effect, accuracy and precision of the developed method were investigated. Results were linear in their concentration ranges, with coefficients of determination (r2) bigger than 0.999. LODs for ClO4- and BrO3- were 0.1 µg/L and 0.5 µg/L, respectively. The validated method provided sufficient selectivity, sensitivity and accuracy to screen for ClO4- and BrO3- with ignorable matrix effects. Recoveries for different kinds of negative samples at 3 spiked levels were between 82.0% and 99.5%. Both intraday-precision and interday-precision were satisfactory, showing RSDr values in the range of 2.1-7.1% and RSDR values in the range of 7.2-10.8%. The proposed method was successfully applied to determine target inorganic anions in several fruits and vegetables. Perchlorate was detected in 12 vegetable samples with the concentrations ranged from 21 µg/kg to 162 µg/kg. Results indicated that there was wide ClO4- contamination in vegetables, confirming its urgency for monitoring harmful inorganic anions in our daily consumed vegetables.

Development and validation of a screening and quantification method for simultaneous determination of seven fluorescent whitening agents in commercial flour using UPLC-MS/MS.

A sensitive UPLC-MS/MS method was established for the simultaneous determination of seven fluorescent whitening agents in flour matrix. Samples were ultrasonically extracted by trichloromethane-acetone. Then analytes were separated on a C18 column and detected by MS/MS. The developed method was validated in terms of the linearity, matrix effect, accuracy and precision. The method showed a good linearity (r>0.997) for all analytes in their respective concentration ranges. The LOQ for seven analytes were in the range of 2.5-25.0µg/kg. The matrix effect was not significant and almost negligible. The average recoveries of seven analytes from the negative samples spiked at three different concentrations were in a range from 81.5% to 105%. The intra-day precision and inter-day precision were in the ranges of 2.9-9.0% and 6.7-11.2%. The developed method was successfully applied to analyze forty commercial flours and FWA184 was detected in three samples with the concentrations of 31-60µg/kg.

Authenticity determination of honeys with non-extractable proteins by means of elemental analyzer (EA) and liquid chromatography (LC) coupled to isotope ratio mass spectroscopy (IRMS).

The present work aims to systematically demonstrate the authenticity of honeys with non-extractable proteins for the first time, by means of EA-IRMS and LC-IRMS. Fifty-three pure honeys of various botanical and geographical origins were studied and a criterion on the basis of the stable carbon isotope ratio characterization of total honey and the main sugars was established for pure honeys. Parameters such as δ13C values of total honey and the main sugars were well utilized to identify honeys with non-extractable proteins. Thirty-five honeys from which protein could not be extracted were all identified as adulterated with C-4 sugars or C-3 sugars. The use of isotopic compositions and some systematic differences permit the honeys with non-extractable proteins to be reliably identified. The findings obtained in this work could supplement the AOAC 998.12 C-4 sugar method, with regard to honeys from which protein cannot be extracted.

A modified quick, easy, cheap, effective, rugged, and safe cleanup method followed by liquid chromatography-tandem mass spectrometry for the rapid analysis of perchlorate, bromate and hypophosphite in flour.

A selective, sensitive and useful method, based on modified QuEChERS cleanup combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the negative-ion electrospray ionization (ESI-) mode, was developed and validated for the simultaneous determination of three inorganic anions including perchlorate (ClO4-), bromate (BrO3-) and hypophosphite (H2PO2-) in flour. The extraction parameters and LC-MS/MS conditions were optimized by single-factor experiment and sorbent combination in modified QuEChERS clean-up was optimized through response surface analysis. Three target analytes were separated on a normal-phase Phenomenex Luna Silica (2) column (150mm×2.0mm, 5µm, 100Å) with the mobile phase of a mixture of 5mmol/L ammonium acetate water solution and acetonitrile, detected by MS/MS under multiple reaction monitoring and quantified by external standard method. The developed method was validated in terms of the sensitivity, linearity, accuracy and precision, and matrix effect. The method showed a good linearity (R2>0.999) for all analytes in their respective concentration ranges. The ILOQs and MLOQs for perchlorate, bromate and hypophosphite were 0.1, 0.5, 5.0µg/L and 2.0, 6.0, 60.0µg/L, respectively. The average recoveries of three target analytes from the negative samples spiked at three different concentrations were in a range from 84.6% to 104.9%. The intra-day precision (n=6) and inter-day precision (n=5) of the target analytes were in the ranges of 2.9%-6.9% and 6.4%-8.2%. The matrix effect of this method was observed between 0.83 and 1.17 and was acceptable. The validated method was successfully applied to determine the concentrations of these inorganic anions in flour. Results found that perchlorate and hypophosphite were detected in 33 out of 50 and 7 out of 50 flour samples.

Dispersive micro solid phase extraction (DMSPE) using polymer anion exchange (PAX) as the sorbent followed by UPLC-MS/MS for the rapid determination of four bisphenols in commercial edible oils.

The present work presents a novel and rapid analytical method for the simultaneous analysis of bisphenol A (BPA), bisphenol B (BPB), bisphenol F (BPF) and bisphenol S (BPS) in edible oil based on dispersive micro solid phase extraction (DMSPE) for the first time followed by isotope dilution-ultra high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The edible oil sample was dispersed by n-hexane and extracted with ammoniated methanol-water solution. Then the target analytes were dispersedly absorbed using the polymer anion exchange (PAX) as the sorbent and eluted by acidic methanol. After that, four bisphenols were separated on a C18 column by gradient elution with methanol and 0.05% ammonium hydroxide in water as mobile phase, detected by MS/MS under multiple reactions monitoring (MRM) mode and quantified by internal standard method. The PAX amounts, adsorption time, concentrations of formic acid in the elution solvent and volume of elution solvent for the DMSPE technique were optimized. The limit of detection and quantitation (LOD and LOQ), matrix effect, recovery and precision of the developed method were investigated. Results indicated that BPS and the rest three bisphenols displayed excellent linearity in the concentration ranges of 0.1-50µg/L and 0.5-250µg/L, respectively, with correlation coefficients (R2) all larger than 0.998. Achieved MLODs (S/N=3) varied between 0.1-0.4µg/kg for all bisphenols. The mean recoveries at three spiked levels in edible oil were in the range of 87.3-108%. Intra-day precision (n=6) and inter-day precision (n=5) were <9% and <11%, respectively. This method is of rapid-and-simple pretreatment, accurate and sensitive, and suitable for the simultaneous determination of bisphenols in edible oil.

QuEChERS-based purification method coupled to ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to determine six quaternary ammonium compounds (QACs) in dairy products.

QuEChERS-based purification coupled with UPLC-MS/MS method, was developed for six quaternary ammonium compounds (QACs) determination in dairy products. Powder samples were firstly dispersed by water. Protein in liquid milk was precipitated and sample solution was extracted by acetonitrile. QuEChERS-based purification was used to purify the solution. QACs were finally separated by HILIC column and detected in MRM mode of MS/MS under ESI(+). The stable isotope benzyl-2,3,4,5,6-d5-dimethyltetradecylammonium bromide (C14-BAC-d5) was used as an internal standard. This method was validated in terms of linearity, sensitivity, precision, accuracy. Linear relations were favorable for QACs over the selected concentration ranges of 0.2-50µg/L, with correlation coefficients greater than 0.999. The limits of detection (LODs) were in the range of 0.4-14.5µg/kg. Recoveries were between 91.2% and 115% with RSDs of 2.8-7.5% for intra-day precision and 3.7-6.7% for inter-day precision. This validated method was successfully applied to determine the QACs concentrations in dairy products.

A salting out-acetonitrile homogeneous extraction coupled with gas chromatography-mass spectrometry method for the simultaneous determination of thirteen N-nitrosamines in skin care cosmetics.

A sensitive gas chromatography-mass spectrometry method was established for the simultaneous determination of thirteen N-nitrosamines (NAs) in skin care cosmetics. The cosmetics samples were firstly dispersed by water and subsequently extracted and purified using salting out-acetonitrile homogeneous extraction method. Finally, the extracting solution was concentrated by slow nitrogen gas blowing. All of the samples were separated by INNOWAX capillary chromatographic column, and detected by selected ion monitoring (SIM) mode of gas chromatography-mass spectrometry (GC-MS) and quantified by isotope internal standard method. The method was validated for linearity and range, accuracy, precision and sensitivity. Under the optimized condition, the calibration curves were linear over the selected concentration ranges of 2-500µg/L for all the thirteen analytes, with calculated coefficients of determination (R(2)) of greater than 0.996. The limits of detection (LODs) and the limits of quantitation (LOQs) of the method were 3-15µg/kg and 10-50µg/kg, respectively. Recoveries were calculated at three levels of concentration spiked in two kinds of cosmetics (skin care cream and water). The values were found between 93.8% and 121.0% with relative standard deviation (RSD) values of 2.5-7.2% for intra-day precision (n=6) and 3.3-6.7% for inter-day precision (n=5). The method was successfully applied to analyze twenty-two cosmetics samples and N-nitrosodimethylamine (NDMA) was detected in one sample with the concentration of 207µg/kg.