Occurrence and Exposure Assessment of Lipophilic Shellfish Toxins in the Zhejiang Province, China.

Although lipophilic shellfish toxins (LSTs) pose a significant threat to the health of seafood consumers, their systematic investigation and risk assessment remain scarce. The goals of this study were as follows: (1) analyze LST levels in commercially available shellfish in Zhejiang province, China, and determine factors influencing LST distribution; (2) assess the acute dietary risk of exposure to LSTs for local consumers during the red tide period; (3) explore potential health risks of LSTs in humans; and (4) study the acute risks of simultaneous dietary exposure to LSTs and paralytic shellfish toxins (PSTs). A total of 546 shellfish samples were collected. LSTs were detected in 89 samples (16.3%) at concentrations below the regulatory limits. Mussels were the main shellfish species contaminated with LSTs. Spatial variations were observed in the yessotoxin group. Acute exposure to LSTs based on multiple scenarios was low. The minimum tolerable exposure durations for LSTs calculated using the mean and the 95th percentile of consumption data were 19.7 and 4.9 years, respectively. Our findings showed that Zhejiang province residents are at a low risk of combined exposure to LSTs and PSTs; however, the risk may be higher for children under 6 years of age in the extreme scenario.

A ng/L Level LC-MS Method Using Membrane SPE as Sampling Technology: Determination of Nine Halobenzoquinones in Potable Water.

A promising method was established for the determination of nine halobenzoquinones (HBQs) in potable water by membrane solid-phase extraction (MSPE) pretreatment and the liquid chromatography-mass spectrometry (LC-MS) method. A 500 mL water sample was taken for enrichment by the SDB-RPS membrane, which was previously activated by methanol and ultrapure water. The sample was eluted with methanol and re-dissolved with the initial mobile phase after nitrogen blowing. Then, it was detected in negative ion mode using the working curve, and HBQs were quantified by the external standard method. The linearity was satisfactory in the concentration range of 4-1000 ng/L, with correlation coefficients of 0.9963~0.9994. The recoveries were 73.5~126.6% at three spiked levels, with relative standard deviations (RSDs) of 6.8~15.5%. The limits of detection (LOD, S/N = 3) values were 0.1~0.7 ng/L. The results demonstrate that the MSPE-LC-MS method is reliable, rapid, and sensitive for the simultaneous analysis of nine HBPs in potable water.

[Identification method of 2-methylisoborneol and geosmin in water by purge and trap-gas chromatography-mass spectrometry].

OBJECTIVE: To establishe an analysis and identification method for 2-methylisoborneol(2-MIB) and geosmin(GSM) in water using purge and trap-gas chromatography-mass spectrometry. METHODS: The samples were enriched and analyzed using a purge and trap system, followed by the separation on a DB-624(30 m×0.25 mm, 1.4 µm) chromatographic column. Quantification was performed using gas chromatography-mass spectrometry with the selected ion monitoring and internal standard calibration. RESULTS: The calibration curves for 2-MIB and GSM showed an excellent linearity in the range of 1 to 100 ng/L with R~2 values greater than 0.999. The detection limit and quantification limit for both 2-MIB and GSM were 0.33 ng/L and 1.0 ng/L, respectively. Spike recovery experiments were further carried on the source water and drinking water at three concentration levels. It showed that the average recoveries were from 82.0% to 111.0% for 2-MIB while 84.0% to 110% for GSM. Additionally, the test precision of 2-MIB and GSM ranged from 1.9% to 7.3% and 1.9% to 5.0%(n=6), respectively. The analysis of multiple samples including the local source water, treated water and distribution network water confirmed the existence of 2-MIB and GSM. CONCLUSION: Compared to the national standard(GB/T 5750.8-2023), the proposed method enables fully automated sample introduction and analysis without the extra pre-treatment. It provides the advantages of simplicity, good repeatability and high accuracy.

Optimization of Physical Refining Process of Camellia Oil for Reduction of 3-Monochloropropane-1,2-Diol (3-MCPD) Ester Formation Using Response Surface Methodology on a Laboratory Scale.

Refined and deodorized camellia oil has been reported to contain a high amount of 3-monochloropropane-1,2-diol esters (3-MCPDE) due to the high-temperature deodorization step. To reduce 3-MCPDE in camellia oil, the physical refining process of camellia oil was simulated on a laboratory scale. Response surface methodology (RSM) was designed to modify and optimize the refining process with five processing parameters (water degumming dosage, degumming temperature, activated clay dosage, deodorization temperature and deodorization time). The optimized new refining approach achieved a 76.9% reduction in 3-MCPDE contents, in which the degumming moisture was 2.97%, the degumming temperature was 50.5 °C, the activated clay dosage was 2.69%, the deodorizing temperature was 230 °C, and the deodorizing time was 90 min. A significance test and analysis of variance results demonstrated that the deodorization temperature and deodorization time contributed significantly to the reduction of 3-MCPD ester. The joint interaction effects of activated clay dosage and deodorization temperature were significant for 3-MCPD ester formation.

Determination of ß2-Agonist Residues in Fermented Ham Using UHPLC-MS/MS after Enzymatic Digestion and Sulfonic Resin Solid Phase Purification.

ß2-agonists are a class of synthetic sympathomimetic drugs with acute poisoning effects if consumed as residues in foods. To improve the efficiency of sample preparation and to overcome matrix-dependent signal suppression in the quantitative analysis of four ß2-agonists (clenbuterol, ractopamine, salbutamol, and terbutaline) residues in fermented ham, an enzyme digestion coupled cation exchange purification method for sample preparation was established using ultra-high performance liquid chromatography and tandem mass spectrometry (UHPLC-MS/MS). Enzymatic digests were subject to cleanup treatment on three different solid phase extraction (SPE) columns and a polymer-based strong cation resin (SCR) cartridge containing sulfonic resin was found to be optimal compared with silica-based sulfonic acid and polymer sulfonic acid resins based SPEs. The analytes were investigated over the linear range of 0.5 to 10.0 µg/kg with recovery rates of 76.0-102.0%, and a relative standard deviation of 1.8-13.3% (n = 6). The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1 µg/kg and 0.3 µg/kg, respectively. This newly developed method was applied to the detection of ß2-agonist residues in 50 commercial ham products and only one sample was found to contain ß2-agonist residues (clenbuterol at 15.2 µg/kg).

[Occurrence and exposure assessment of fumonisins from grains and grain products in Zhejiang Province in 2018-2019].

OBJECTIVE: To monitor fumonisins(FBs) in grains and grain products in Zhejiang and assess the exposure risks of FBs to local residents. METHODS: Liquid chromatography coupled with tandem mass spectrometry method was used to determine the occurrence of FBs in rice, millet, dried noodles, instant noodles, and maize grains, and food frequency questionnaires were used to collect the food consumption data of Zhejiang population. Then, the simple probability distribution model was used to assess the exposure risk. RESULTS: The levels of FBs in rice, millet, dried noodles and instant noodles were relatively low. The occurrence of FB_1, FB_2 and FB_3 in these foods was 0-23.7%, 0-16.7% and 0-5.4%, respectively, and the mean levels were not detected(ND)-22.36, ND-20.63 and ND-7.19 µg/kg correspondingly. However, the levels of FBs in maize grains were relatively high. The occurrence of FB_1, FB_2, and FB_3 in maize grains was 100%, 93.6% and 90.3%, respectively, and the mean levels were 638.99, 103.54 and 59.69 µg/kg correspondingly. In 12.9% of the maize grain samples, the levels of FBs were higher than the standard reference. The residents were at low exposure risk overall. The mean estimated daily intake(EDI) of FBs was far lower than the provisional maximum tolerable daily intake of 2 µg/(kg·BW·d). However, 0.30% of the residents were at high risk. Among people of different ages, the mean EDI of children, adults, and elderly were 0.43, 0.28 and 0.29 µg/(kg·BW·d) respectively, and children were in the highest exposure levels of FBs. Among the tested five foodstuffs, rice and maize grains were the main sources of FBs exposure. CONCLUSION: Except for maize grains, the levels of FBs in grains and grain products were relatively low, and Zhejiang residents were at low FBs exposure risk generally.

Determination of Polycyclic Aromatic Hydrocarbons in Traditional Chinese Medicine Raw Material, Extracts, and Health Food Products.

The four polycyclic aromatic hydrocarbon markers (PAH4) of benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbF), and benzo[a]pyrene (BaP) are indicators showing polycyclic aromatic hydrocarbon (PAH) contamination levels in Chinese medicine raw materials (CMRMs), extracts and health food products; Samples of herbal medicine, herbal extracts, and food supplements were extracted with n-hexane, then cleaned up sequentially on Florisil and EUPAH solid-phase extraction (SPE) columns. A gas chromatography-mass spectrometry method for the determination of four polycyclic aromatic hydrocarbon markers in Chinese medicine raw material, extracts, and health food products was established; In spiked-recovery experiments, the average recovery was about 78.6-107.6% with a precision of 2.3-10.5%. The limit of quantification (LOQ) and limit of detection (LOD) of the PAH4 markers in this method were 2.0 µg/kg and 0.7 µg/kg, respectively. When the developed method was utilized to determine PAH4 contents in 12 locally available health food products, 3 samples contained over 10.0 µg/kg BaP, and 5 samples contained over 50.0 µg/kg PAH4. The European Union (EU) limits for BaP and PAH4 are 10 and 50.0 µg/kg, respectively; therefore, more attention must be drawn to the exposure risk of BaP and PAH4 in CMRMs, their extracts, and health food products. According to the risk assessment based on the Margin of Exposure (MOE) method, it is recognized that the products mentioned in this study pose a low risk.

[Characterization and investigation of 16 European priority polycyclic aromatic hydrocarbons in commercial infant formula milk powder in Hangzhou].

OBJECTIVE: A gas chromatography-mass spectrometry(GC-MS) method for the determination of 16 European priority polycyclic aromatic hydrocarbons(16 EUPAHs) in infant formula milk powder was established, and the characterization and investigation of 16 EUPAHs in 70 milk formula powders were carried out in 2020. METHODS: After hydrolysis, extraction, saponification and solid phase extraction, infant formula milk powder was detected by GC-MS using DB-EUPAH capillary column(20 m×0.18 mm, 0.14 µm)and quantified by internal standard method. RESULTS: The average recoveries ranged from 67.8% to 116.2% and the relative standard deviations ranged from 2.0% to 15.1%(n=6). The limits of quantification and detection of the method were 0.5 and 0.2 µg/kg, respectively. The content of 16 EUPAHs was <0.2-0.48 µg/kg, including PAH4 content in the range of <0.2-0.91 µg/kg, the characterization and investigation of infant formula powder in 16 EUPAHs mainly chrysene, cyclopenta[c, d]pyrene, benz[a]anthracene, benzo[b]fluoranthene, benzo[g, h, i]perylene. CONCLUSION: The method is simple, accurate and suitable for the determination of 16 EUPAHs in infant formula milk powder. The result showed that the content of 16 EUPAHs in commercially available infant formula milk powder in Hangzhou was low and all of them met the limit requirement of European Union.

[Determination of 4 polycyclic aromatic hydrocarbons in spicy strips by vacuum concentration coupled with isotope dilution gas chromatography-mass spectrometry].

OBJECTIVE: A method based on isotope internal standard dilution was established for the determination of four polycyclic aromatic hydrocarbons(PAH4) including chrysene, benzo [a] anthracene, benzo [b] fluoranthene and benzo [a] pyrene in spicy strips sold in the markets. METHODS: The hot strips were homogenized and the target compounds were extracted with n-hexane, concentrated in vacuum, saponified and purified by solid phase extraction column, then the pretreated samples were separated by DB-EUPAH column(20 m×0. 18 mm, 0. 14 µm), detected by gas chromatography-mass spectrometry(GC-MS)and quantified by internal standard of isotope. RESULTS: The recoveries of PAH4 in different concentration levels of hot noodles were 91. 0%-103. 5%, and the relative standard deviation(RSD)was 1. 89%-6. 73%(n=6). The detection limit was 0. 30 µg/kg and the quantitative limit was 1. 0 µg/kg. The content of PAH4(sum) in 27 collected samples ranged from 1. 35 µg/kg to 11. 44 µg/kg, and the detection rate was 100%. CONCLUSION: With less solvent consumption, good purification effect and blank control, the method is simple, rapid and accurate and meets the detecting requirements of PAH4 in hot strips.

[Detection and content investigation of benzo[a]pyrene in infant milk powder].

OBJECTIVE: To develop a method for determination of benzo[a]pyrene and to analysis of benzo[a]pyrene content in commercially available infant milk powder. METHODS: Firstly, infant milk powder was extracted with ether-petroleum ether(1∶1, V/V) under alkaline conditions, then saponified with 1. 5 mol/L potassium hydroxide ethanol solution. After purification by solid phase extraction column, it was separated on DB-EUPAH chromatographic column(20 m×0. 18 mm×0. 14 µm) and detected by gas chromatography-mass spectrometry, and quantified using D_(12)-benzo[a]pyrene internal standard. RESULTS: When the benzo[a]pyrene in infant formula was spiked 0. 3, 1. 0, 5. 0 µg/kg, the average recoveries were 116. 7%、86. 0% and 96. 4%, respectively, and the relative standard deviations were 10. 5%、4. 2% and 4. 4%, respectively(n= 6). The limit of quantification was 0. 3 µg/kg, and the detection limit was 0. 1 µg/kg. A total of 40 domestic and imported infant milk powders sold in Hangzhou supermarkets were analyzed. The range of benzo[a]pyrene was <0. 1-0. 25 µg/kg, and the detection rate was 32. 5%. CONCLUSION: The method has the advantages of rapid operation, good purifying effect, sensitiveness and accuracy, and meets the requirements for detection of benzo[a]pyrene in infant milk powder. The investigation reveals that the benzo[a]pyrene content in the currently marketed infant milk powder is at a low level.

[Simultaneous determination of 16 polycyclic aromatic hydrocarbons in source water and tap water by performance liquid chromatography with ultraviolet detector tandem fluorescence detector combined with solid phase extraction].

OBJECTIVE: To establish a rapid method for simultaneous determination of 16 polycyclic aromatic hydrocarbons(PAHs) in source water and tap water by performance liquid chromatography(HPLC) with ultraviolet detector(UV) tandem fluorescence detector(FLR). METHODS: Source water was filtered by GF/C glass fiber filters and tap water were added ascorbic acid of 60 mg per liter to remove the residual chlorine when sampling. 500 mL water sample were sampled and adjusted pH 2 with phosphoric acid, then 10 mL methanol were added. Then samples were concentrated by styrene stilbene polymer solid phase extraction column, after loading samples, 50 percent methanol aqueous solution adjust pH 2 were used for washing bottle and the washed solution were continuum loaded. Then 80 percent methanol aqueous solution was used for removing impurity interference and elution with dichloromethane. The eluent was nitrogen blow to near dry after adding 100 µL 10 percent tween-20 methanol solutions(m/V). Acetonitrile was used for reconstitution, and then separated by PAH chromatography column using acetonitrile and pure water at gradient elution, and detected by UV tandem FLR detector. RESULTS: The linear ranges of 16 PAHs were 0. 5 to 500 ng/mL and the correlation coefficients were greater than 0. 999. The method detection limit and limits of quantification were 0. 3 to 5. 0 ng/L and 1. 2 to 20. 0 ng/L, respectively. The recoveries were in the range of 67. 2%-114. 1% with the relative standard deviations ranging from 1. 5%-14. 0%(n=6). Then the established method was used for the determination of 17 water samples, 8 kinds, 6 kinds and 7 kinds of PAHs were detected in source water, tap water and pipe net tap water, respectively. CONCLUSION: The method is rapid, sensitive and selective, and has been successfully applied for determination of 16 PAHs in source water and tap water.

[Determination of zearalenone and α-zearalenol in vegetable oil and grain products by C_(18)-Al_2O_3 solid phase extraction column purification coupled with ultra-performance liquid chromatography tandem mass spectrometry].

OBJECTIVE: To develop a method for simultaneous determination of zearalenone( ZEN) and α-zearalenol( α-ZEL) in vegetable oil and grain products by solid phase extraction column purification coupled with ultra-performance liquid chromatography tandem mass spectrometry. METHODS: Firstly, ZEN and α-ZEL in grain products were extracted by hexane/ethyl acetate( 50 : 50, V/V), and then extracted as vegetable oil by acetonitrile-water solution( 90: 10, V/V), and purified by C_(18)-Al_2O_3 solid phase extraction column. ZEN and α-ZEL was separated by UPLC with acetonitrile-water gradient elution on C_(18) column( 2. 1 mm × 100 mm, 1. 6 µm), and qualified/quantified by mass spectrometry with ESI negative MRM mode with ~(13)C_(18)-zearalenone as internal standard. RESULTS: The linearity of ZEN and α-ZEL ranged from 1. 0-500 ng/mL. The limit of detection for ZEN and α-ZEL in vegetable oil and grain products was 0. 3 and 0. 2 µg/kg, respectively. The limit of quantification for ZEN and α-ZEL in vegetable oil and grain products was 1. 0 and 0. 5 µg/kg. The average recoveries of ZEN and α-ZEL for spiked samples of 1. 0-100 µg/kg were 93. 5%-108. 0% and 92. 0%-105. 0%. The relative standard deviations of ZEN and α-ZEL were 3. 2%-8. 5% and 4. 6%-7. 8%( n = 6). 55 samples sold in Hangzhou supermarkets were analyzed. ZEN was detected in all corn germ oil with median and maximum contents of 126. 2 and 453. 1 µg/kg. α-ZEL was detected in 50% corn germ oil with median and maximum contents of 2. 0 and 5. 0µg/kg. CONCLUSION: The method possesses several advantages including sensitivity, precision, good efficiency of purification, simplicity and economy, and it is applicable to the batch analysis of zearalenone and α-zearalenol in vegetable oil and grain products.

[Determination of 3-monochloropropane-1,2-diol in grease food by solid phase extraction-derivatization-gas chromatography-mass spectrometry].

OBJECTIVE: To establish the method of determination of 3-monochloropropane-1,2-diol( 3-MCPD) in grease food by gas chromatography-mass spectrometry( GC-MS). METHODS: 3-MCPD in grease food represented by bean paste was extracted by ultrasound,purified by alkaline earth solid phase extraction column,derivatived using phenylboronic acid( PBA) and detected by GC-MS. RESULTS: The linearity of 3-MCPD ranged from 1-100 ng/mL,with correlation coefficient at 0. 9993.The limits of quantitation( LOQ) in soy sauce,bean paste,pepper oil were 0. 6,0. 5 and7. 0 µg/kg and limits of detection( LOD) were 1. 9,1. 6 and 18. 8 µg/kg,respectively.Average recovery rate and relative standard deviation was 78. 3%-106. 7% and 1. 9%-11. 6%( n = 6), when 3-MCPD was added in grease food at 2. 5-1000 µg/kg. CONCLUSION: The method has good purification effect and the detection sensitivity and accuracy,and can be used for the determination of 3-MCPD in grease food.

[Determination of phthalate ester metabolites in urine by solid-phase extraction and gas chromatography-mass spectrometry].

OBJECTIVE: A method for the determination of 5 kinds of phthalate monoesters in urine by solid-phase extraction and gas chromatography-mass spectrometry was developed. METHODS: After urine enzymatic hydrolysis by ß-glucuronidase, the sample was pretreated by SPE. Phthalate monoesters were eluted by boron trifluoridemethanol complex, and determined by gas chromatograph-mass spectrometer with DB-5 ms Phenomenex( 30 m × 0. 25 mm, 0. 25 µm). RESULTS: Within the concentration range of25. 0-1000 µg/L, the relationship between peak area and concentration of 5 kinds of phthalate monoesters presented linear relation. The correlation coefficient was 0. 9989-0. 9996, and the determination limit was 10. 0-15. 0 µg/L. The recoveries of phthalate monoesters were in the range of 80. 2%-97. 8% when set at 15. 0, 200 and 500 µg/L concentration levels, and the relative standard deviation was in the range of 4. 2%-10. 2%( n = 6). A total of 81 pregnant women were detected by this method and thedetection rate was 98. 7%. CONCLUSION: This method could be used in the simultaneous determination of 5 kinds of phthalate monoesters.

Isotope dilution gas chromatography with mass spectrometry for the analysis of 4-octyl phenol, 4-nonylphenol, and bisphenol A in vegetable oils.

By the combination of solid-phase extraction as well as isotope dilution gas chromatography with mass spectrometry, a sensitive and reliable method for the determination of endocrine-disrupting chemicals including bisphenol A, 4-octylphenol, and 4-nonylphenol in vegetable oils was established. The application of a silica/N-(n-propyl)ethylenediamine mixed solid-phase extraction cartridge achieved relatively low matrix effects for bisphenol A, 4-octylphenol, and 4-nonylphenol in vegetable oils. Experiments were designed to evaluate the effects of derivatization, and the extraction parameters were optimized. The estimated limits of detection and quantification for bisphenol A, 4-octylphenol, and 4-nonylphenol were 0.83 and 2.5 µg/kg, respectively. In a spiked experiment in vegetable oils, the recovery of the added bisphenol A was 97.5-110.3%, recovery of the added 4-octylphenol was 64.4-87.4%, and that of 4-nonylphenol was 68.2-89.3%. This sensitive method was then applied to real vegetable oil samples from Zhejiang Province of China, and none of the target compounds were detected.

[Determination of chlorfenapyr and indoxacarb in tea by gas chromatography-mass spectrometry with solid phase extraction].

OBJECTIVE: To establish a method for simultaneous determination of chlorfenapyr and indoxacarb in tea by gas chromatography-mass spectrometry. METHODS: The tea samples were homogenized and extracted with acetonitrile. Extracts obtained through centrifugation were cleaned up by CARB / NH2 cartridges, and further purified with SLH cartridges. After separated by DB-5MS capillary column( 30 m × 0. 25 mm × 0. 25µm), the analytes were measured by gas chromatography-mass spectrometry in selective ion monitoring( SIM) mode and quantified by external standard method. RESULTS: The linear range was 0. 10- 10 µg / m L for both of the two pesticides. The detection limits of chlorfenapyr and indoxacarb in tea samples were 0. 01 and 0. 008 mg / kg, and the quantitation limits were 0. 03 and 0. 025 mg / kg, respectively. The recoveries were from75. 6% to 92. 7%, and the relative standarddeviations( RSDs) were 3. 6%- 11. 4%( n =6). CONCLUSION: The proposed method has good purification effect and high accuracy, which is capable for simultaneously detecting the chlorfenapyr and indoxacarb in tea samples.

[Determination of 16 polycyclic aromatic hydrocarbons in edible oils by gas chromatography-mass spectrometry combined with molecularly imprinted solid phase extraction].

OBJECTIVE: To establish a method for determination of 16 polycyclic aromatic hydrocarbons( PAHs) in edible oils by gas chromatography-mass spectrometry( GC/MS) combined with molecularly imprinted solid phase extraction( MISPE-GC/MS). METHODS: Oil samples were diluted with n-hexane, purified by SPE cartridges based on molecularly imprinted polymer. The cartridges were washed by n-hexane to remove impurities, then eluted with dichloromethane. After being concentrated to a volume of 200µL, the analytes were separated by capillary column( 30 m×0. 25 mm×0. 25 µm) and analyzed by GC/MS with selected ion monitoring( SIM) mode. Isotope internal standard method was adopted for quantification. RESULTS: The 16 kinds of PAHs showed good linearity in the range of 2-20 µg/L( r > 0. 998). The detection limits ranged from 0. 1 to0. 6 µg/kg. The recoveries of spiked samples at the level of 2 µg/kg and 10 µg/kg were in the range of 75. 5%-125. 2%( n = 6), the relative standard deviations( RSD) were all less than 15%. CONCLUSION: The proposed method is selective, fast, and presentsexcellent purification effect as well as high sensitivity, which makes it capable for rapid determination of 16 PAHs in edible oils with satisfactory accuracy.

[Determination of eleven fluorescent whitening agents in paper food packaging materials by UPLC-FLD/PDA with series double-detector].

OBJECTIVE: To establish a new qualitative and quantitative ultraperformance liquid chromatography-fluorescence detector / photodiode array detector with series double-detector method for the determination of eleven fluorescent whitening agents in paper food packaging materials. METHODS: The sample was extracted with 40%acetonitrile water solution, separated by Waters ACQUITY UPLC BEH C_(18)column( 1. 7µm, 2. 1 mm × 100 mm) and eluted gradient. The excitation wavelength and emission wavelength of fluorescence detector( FLD) were 350 nm and 430 nm, and the wavelength of photodiode array detector( PDA) was 350 nm. The detectors were used in series to achieve qualitative and quantitative detection. RESULTS: In the substrates of paper cups, paper bowls, paper trays and paper boxes, those eleven fluorescent whitening agents were separated properly. For both detectors, in the linear range of 25- 1000 ng / m L, the correlation coefficient was greater than 0. 99, and the recoveries of spiked recoveries were between 82. 2%- 104. 1% with the RSD less than 10%( n = 6). The detection limits ofthose eleven fluorescent whitening agents were 0. 20- 0. 28 mg / kg for FLD and 1. 4- 2. 5mg / kg for PDA. CONCLUSION: The eleven fluorescent whitening agents could be separated properly with complete separation, good shapes and high recovery rate. This method is easy to operate also. Thus it's an effective method to detect the fluorescent whitening agents in paper food packaging materials.

Comparison of different calibration approaches for chloramphenicol quantification in chicken muscle by ultra-high pressure liquid chromatography tandem mass spectrometry.

Matrix-dependent signal suppression often occurs in quantitative analysis by ultra-high pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS). In this study, we investigated three calibration methods for compensation of signal suppression on chloramphenicol (CAP) quantification in chicken muscle. The data showed that the spiking recoveries by solvent standard calibration with a stable isotope labelled internal standard (SIL-IS) and matrix-matched standard calibration with a SIL-IS were significantly higher than by external matrix-matched standard calibration (P < 0.05). When the SIL-IS was used, standards prepared in the mobile phase solvent showed no significant difference as those prepared in the matrix (P > 0.05). The limit of detection (LOD) for external matrix matched standard calibration was 0.1 µg kg(-1), and that for SIL-IS calibration (including matrix matched and solvent dissolved standard) was 0.03 µg kg(-1).

Determination of three kinds of banned drugs in milk powder by hybrid solid-phase extraction purification combined with gas chromatography and mass spectrometry.

A gradient clean-up method for the quantification of five kinds of banned drugs (two hormones, two sedatives, and one chloramphenicol) in milk powder was developed. We used the combination of solid-phase extraction purification with gas chromatography and mass spectrometry. Milk powder was initially hydrolyzed by ß-glucuronidase/arylsulfatase, and then the hydrolyzed solution was concentrated and purified using a C8 and cation resin solid-phase extraction column. To isolate hormones and chloramphenicol drugs, products from the previous step were diluted with methanol and further purified using a silica and diatomite solid-phase extraction column. After derivatization, the drugs were analyzed by gas chromatography with mass spectrometry, and the hydrolyzed solution was diluted with 5% ammoniated methanol to purify sedatives before gas chromatography with mass spectrometry analysis. Results showed that after adding the banned drugs at concentrations of 0.3-10.0 µg/kg, the average recovery range was 78.2-97.3% with relative standard deviations of 5.3-12.5%. The limit of quantification of the banned drugs (S/N ≥ 10) was 0.3-5.0 µg/kg, whereas the limit of detection (S/N ≥ 3) was 0.1-2.0 µg/kg. The solid-phase extraction gradient purification system was simple, rapid, and accurate, and could satisfy the detection requirements of hormone, sedatives, and chloramphenicol drugs when used together with gas chromatography and mass spectrometry.