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2020 Volume 38 Issue 6
2020, 38(6): 621-626
doi: 10.3724/SP.J.1123.2019.10016
Abstract:
In recent years, red tide pollution in China has become increasingly serious, leading to a number of shellfish poisoning cases, thereby posing a threat to human health and safety. Okadaic acid (OA) and its analogs (dinophysistoxins, DTXs) are the most widely distributed diarrhetic shellfish poisons, which result in acute diarrheal toxicity and various types of chronic toxicity. It is imperative to establish a method for determination of OA related toxin residues in biological fluid samples, so that accurate diagnosis of poisoning in patients is possible. The present paper briefly introduced the main physicochemical properties, poisoning incidents, toxicological effects for the toxins, also summarized recent progress on the metabolic rules and detection methods for OA related toxins in biological samples.
In recent years, red tide pollution in China has become increasingly serious, leading to a number of shellfish poisoning cases, thereby posing a threat to human health and safety. Okadaic acid (OA) and its analogs (dinophysistoxins, DTXs) are the most widely distributed diarrhetic shellfish poisons, which result in acute diarrheal toxicity and various types of chronic toxicity. It is imperative to establish a method for determination of OA related toxin residues in biological fluid samples, so that accurate diagnosis of poisoning in patients is possible. The present paper briefly introduced the main physicochemical properties, poisoning incidents, toxicological effects for the toxins, also summarized recent progress on the metabolic rules and detection methods for OA related toxins in biological samples.
2020, 38(6): 627-638
doi: 10.3724/SP.J.1123.2019.12007
Abstract:
The first commercial interface for hyphenating liquid chromatography with isotope ratio mass spectrometry (LC-IRMS) was not available until 2004, and it was commercialized under the name LC IsoLink by Thermo Finnigan. LC-IRMS, a method of compound-specific isotope analysis, has enabled the detection of stable carbon isotope ratios (δ13C) in targeted substances in order to determine their origin and authenticity. This paper provides an overview of IRMS and LC-IRMS techniques, the history and detailed classification of the latter over the past twenty years. The application of LC-IRMS to the fields of food safety, environment and ecology, life sciences, and archeology are reviewed. Finally, the technical limitations, current challenges, and future development trends of LC-IRMS are outlined.
The first commercial interface for hyphenating liquid chromatography with isotope ratio mass spectrometry (LC-IRMS) was not available until 2004, and it was commercialized under the name LC IsoLink by Thermo Finnigan. LC-IRMS, a method of compound-specific isotope analysis, has enabled the detection of stable carbon isotope ratios (δ13C) in targeted substances in order to determine their origin and authenticity. This paper provides an overview of IRMS and LC-IRMS techniques, the history and detailed classification of the latter over the past twenty years. The application of LC-IRMS to the fields of food safety, environment and ecology, life sciences, and archeology are reviewed. Finally, the technical limitations, current challenges, and future development trends of LC-IRMS are outlined.
2020, 38(6): 639-646
doi: 10.3724/SP.J.1123.2019.10012
Abstract:
A novel solid phase microextraction fiber of polyaniline coated titania composite nanotube (PANI@TiO2NTs/Ti) array was fabricated on a titanium wire by in situ oxidation. The effects of the inorganic acid medium, aniline concentration, and oxidation voltage on the electropolymerization of aniline were discussed. The best forming conditions for the composite fiber obtained by analyzing the surface morphology and composition of the fibers were as follows:electrolyte composing, 0.5 mol/L aniline-1 mol/L H2SO4; electropolymerization, 10 V for 60 min. The developed fibers were used in conjunction with high performance liquid chromatography for the extraction and determination of ultraviolet filters in samples, and the extraction conditions optimized were as follows:extraction time 40 min, desorption time 4 min, extraction temperature 40℃, stirring rate 600 r/min. The average recoveries of the target analytes spiked in real samples ranged from 78.2% to 118%, and the relative standard deviations ranged from 4.4% to 8.9%. The developed method is simple, rapid, and accurate, and it is suitable for the sensitive determination of UV filters in environmental water samples.
A novel solid phase microextraction fiber of polyaniline coated titania composite nanotube (PANI@TiO2NTs/Ti) array was fabricated on a titanium wire by in situ oxidation. The effects of the inorganic acid medium, aniline concentration, and oxidation voltage on the electropolymerization of aniline were discussed. The best forming conditions for the composite fiber obtained by analyzing the surface morphology and composition of the fibers were as follows:electrolyte composing, 0.5 mol/L aniline-1 mol/L H2SO4; electropolymerization, 10 V for 60 min. The developed fibers were used in conjunction with high performance liquid chromatography for the extraction and determination of ultraviolet filters in samples, and the extraction conditions optimized were as follows:extraction time 40 min, desorption time 4 min, extraction temperature 40℃, stirring rate 600 r/min. The average recoveries of the target analytes spiked in real samples ranged from 78.2% to 118%, and the relative standard deviations ranged from 4.4% to 8.9%. The developed method is simple, rapid, and accurate, and it is suitable for the sensitive determination of UV filters in environmental water samples.
2020, 38(6): 647-654
doi: 10.3724/SP.J.1123.2019.10021
Abstract:
A method based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with a small homemade mixed column was developed for the simultaneous determination of seven metabolites of organophosphate esters (OPEs) and 8-hydroxy-2'-deoxyguanosine (8-OHdG), an DNA oxidative damage marker, in urine. The urine samples were extracted by acetonitrile and enriched by the self-made column. All the samples were separated by gradient elution with acetonitrile-0.2% (v/v) ammonia solution, and then analyzed by an electrospray ionization source in negative ion multiple reaction monitoring mode. The results showed that the eight targets had good linearities in the range of 0.1-200 μg/L. The recoveries of the seven metabolites of OPEs and 8-OHdG in urine samples were in the ranges of 52.36% to 114.56% and 88.63% to 97.72%, respectively. The established method was successfully applied for the determination of the abovementioned eight target compounds in real urine samples, with the mass concentrations of the seven metabolites of OPEs and 8-OHdG being 6.24-46.07 μg/L and 5.90-16.71 μg/L, respectively. In addition, significant correlations were found between 8-OHdG and the total content of the seven metabolites of OPEs. The established method is simple, sensitive, accurate, and reproducible, and it provides reliable technical support for a more comprehensive evaluation of the level of human exposure to OPEs and the resulting health hazards.
A method based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with a small homemade mixed column was developed for the simultaneous determination of seven metabolites of organophosphate esters (OPEs) and 8-hydroxy-2'-deoxyguanosine (8-OHdG), an DNA oxidative damage marker, in urine. The urine samples were extracted by acetonitrile and enriched by the self-made column. All the samples were separated by gradient elution with acetonitrile-0.2% (v/v) ammonia solution, and then analyzed by an electrospray ionization source in negative ion multiple reaction monitoring mode. The results showed that the eight targets had good linearities in the range of 0.1-200 μg/L. The recoveries of the seven metabolites of OPEs and 8-OHdG in urine samples were in the ranges of 52.36% to 114.56% and 88.63% to 97.72%, respectively. The established method was successfully applied for the determination of the abovementioned eight target compounds in real urine samples, with the mass concentrations of the seven metabolites of OPEs and 8-OHdG being 6.24-46.07 μg/L and 5.90-16.71 μg/L, respectively. In addition, significant correlations were found between 8-OHdG and the total content of the seven metabolites of OPEs. The established method is simple, sensitive, accurate, and reproducible, and it provides reliable technical support for a more comprehensive evaluation of the level of human exposure to OPEs and the resulting health hazards.
2020, 38(6): 655-662
doi: 10.3724/SP.J.1123.2019.10011
Abstract:
An analytical method was established for the determination of 15 lipid regulators in fish meat by QuEChERS combined with ultra performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry (UPLC-Q/Orbitrap-MS). The samples were purified by optimized QuEChERS methods. The amounts of the adsorbent materials (primary secondary amine (PSA) (20, 60, 100, 140 and 180 mg), C18 (40, 100, 160, 220 and 280 mg) and sodium acetate (0.2, 0.6, 1.0, 1.4 and 1.8 g)) were optimized by the response surface method to obtain the best purification effect. The target compounds were separated on an XBridge-C18 column (100 mm×2.1 mm, 3.5 μm) using acetonitrile-0.1% (v/v) formic acid aqueous solution (containing 1.5 mmol/L ammonium acetate) as the mobile phases by a gradient elution program. Qualitative and quantitative analysis of the target compounds were performed in the full scan and secondary mass spectrometry scan (dd-MS2) modes with positive and negative ionization. The target compounds showed good linear relationships in their respective ranges, with correlation coefficients (R2) greater than 0.99. The limits of detection (LOD, S/N=3) and limits of quantification (LOQ, S/N=10) were in the range of 0.2-1.0 μg/kg and 0.3-3.1 μg/kg, respectively. The average recoveries were 76.4%-116.0% at LOQ, 2-fold LOQ, and 10-fold LOQ levels. The intra-day relative standard deviations (RSDs) were 1.0%-7.9%, and the inter-day RSDs were 1.7%-18.4%. The method is simple, sensitive and accurate, and it is suitable for the determination and quantification of lipid regulators in fish meat.
An analytical method was established for the determination of 15 lipid regulators in fish meat by QuEChERS combined with ultra performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry (UPLC-Q/Orbitrap-MS). The samples were purified by optimized QuEChERS methods. The amounts of the adsorbent materials (primary secondary amine (PSA) (20, 60, 100, 140 and 180 mg), C18 (40, 100, 160, 220 and 280 mg) and sodium acetate (0.2, 0.6, 1.0, 1.4 and 1.8 g)) were optimized by the response surface method to obtain the best purification effect. The target compounds were separated on an XBridge-C18 column (100 mm×2.1 mm, 3.5 μm) using acetonitrile-0.1% (v/v) formic acid aqueous solution (containing 1.5 mmol/L ammonium acetate) as the mobile phases by a gradient elution program. Qualitative and quantitative analysis of the target compounds were performed in the full scan and secondary mass spectrometry scan (dd-MS2) modes with positive and negative ionization. The target compounds showed good linear relationships in their respective ranges, with correlation coefficients (R2) greater than 0.99. The limits of detection (LOD, S/N=3) and limits of quantification (LOQ, S/N=10) were in the range of 0.2-1.0 μg/kg and 0.3-3.1 μg/kg, respectively. The average recoveries were 76.4%-116.0% at LOQ, 2-fold LOQ, and 10-fold LOQ levels. The intra-day relative standard deviations (RSDs) were 1.0%-7.9%, and the inter-day RSDs were 1.7%-18.4%. The method is simple, sensitive and accurate, and it is suitable for the determination and quantification of lipid regulators in fish meat.
2020, 38(6): 663-671
doi: 10.3724/SP.J.1123.2019.10025
Abstract:
An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the quantitative detection of bovine lactoferrin in dairy products. The samples were treated by degreasing and tryptic hydrolysis. Proteins of bovine lactoferrin and peptides were identified using ultra performance liquid chromatography-quadrupole/electrostatic orbitrap-high resolution mass spectrometry (UPLC-Q/Exactive-HRMS) and analyzed by Protein Pilot software. Eight species-specific marker peptides of bovine lactoferrin were identified by comparison of the basic local alignment search tool (BLAST) with the Uniprot database. Three markers with high response strength and stability were chosen for further quantitative research by UPLC-triple quadrupole mass spectrometry (QqQ-MS). The method showed a good linear relationship within its own range. The limits of detection and limits of quantification were 0.023-0.041 and 0.077-0.137 mg/kg, respectively. The observed recoveries were in the range of 93.8%-103.9%. The intra-day and inter-day RSDs were lower than 8.8% and 9.5%, respectively. This method presents various advantages such as strong anti-interference, high sensitivity and reproducibility, and it is suitable for the quantitative analysis of bovine lactoferrin in dairy products.
An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was established for the quantitative detection of bovine lactoferrin in dairy products. The samples were treated by degreasing and tryptic hydrolysis. Proteins of bovine lactoferrin and peptides were identified using ultra performance liquid chromatography-quadrupole/electrostatic orbitrap-high resolution mass spectrometry (UPLC-Q/Exactive-HRMS) and analyzed by Protein Pilot software. Eight species-specific marker peptides of bovine lactoferrin were identified by comparison of the basic local alignment search tool (BLAST) with the Uniprot database. Three markers with high response strength and stability were chosen for further quantitative research by UPLC-triple quadrupole mass spectrometry (QqQ-MS). The method showed a good linear relationship within its own range. The limits of detection and limits of quantification were 0.023-0.041 and 0.077-0.137 mg/kg, respectively. The observed recoveries were in the range of 93.8%-103.9%. The intra-day and inter-day RSDs were lower than 8.8% and 9.5%, respectively. This method presents various advantages such as strong anti-interference, high sensitivity and reproducibility, and it is suitable for the quantitative analysis of bovine lactoferrin in dairy products.
2020, 38(6): 672-678
doi: 10.3724/SP.J.1123.2019.11008
Abstract:
A method based on dispersive solid-phase extraction-high performance liquid chromatography-tandem mass spectrometry (DSPE-HPLC-MS/MS) was developed for the simultaneous determination of five analytes scutellarein, 4'-hydroxywogonin, norwogonin, baicalein, and wogonin in healthy product tablets. The samples were extracted with 10 mL acetone and purified on 75 mg C18. The types and dosages of the extracted solvents and adsorbents were optimized. The results showed that these five analytes exhibited good linear relationships in their respective linear ranges. The correlation coefficients (r) were more than 0.99. The detection limits and quantitative limits were 0.5-40 μg/kg and 2.0-120 μg/kg, respectively. Recovery tests were carried out using three kinds of health product tablet matrices. The concentrations were one, five, and ten times the quantitative limit. The average recovery of these five targets was 83.1% to 106.5%, with relative standard deviations (RSDs) ranging from 0.97% to 4.52%. This method is easy to operate, and it shows high sensitivity and good reproducibility. Thus, it is suitable for the simultaneous determination of the target compounds in health tablets.
A method based on dispersive solid-phase extraction-high performance liquid chromatography-tandem mass spectrometry (DSPE-HPLC-MS/MS) was developed for the simultaneous determination of five analytes scutellarein, 4'-hydroxywogonin, norwogonin, baicalein, and wogonin in healthy product tablets. The samples were extracted with 10 mL acetone and purified on 75 mg C18. The types and dosages of the extracted solvents and adsorbents were optimized. The results showed that these five analytes exhibited good linear relationships in their respective linear ranges. The correlation coefficients (r) were more than 0.99. The detection limits and quantitative limits were 0.5-40 μg/kg and 2.0-120 μg/kg, respectively. Recovery tests were carried out using three kinds of health product tablet matrices. The concentrations were one, five, and ten times the quantitative limit. The average recovery of these five targets was 83.1% to 106.5%, with relative standard deviations (RSDs) ranging from 0.97% to 4.52%. This method is easy to operate, and it shows high sensitivity and good reproducibility. Thus, it is suitable for the simultaneous determination of the target compounds in health tablets.
2020, 38(6): 679-686
doi: 10.3724/SP.J.1123.2019.10027
Abstract:
A rapid method for the determination of five organophosphorus flame retardants (OPFRs) in textile wastewater was established by dispersive liquid-liquid microextraction (DLLME) based on solidification of floating organic drop (SFO) coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The analytes were extracted from the water samples by SFO-DLLME, which was performed using a mixture of an extraction solvent that was less dense than water, 1-undecanol, and a dispersive solvent, methanol. The influences of the SFO-DLLME parameters on the extraction efficiencies were studied. 1-Undecanol (extraction solvent, 400 μL) and methanol (dispersive solvent, 300 μL) were added to textile wastewater (containing 2 g NaCl) with pH between 6 and 9, and the solution was shaken for 2 min. Under optimum conditions, the linear ranges of the proposed method were from 2 μg/L to 100 μg/L with correlation coefficients (R2) above 0.99 for all the analytes. The limits of detection (S/N=3) ranged from 2 μg/L to 5 μg/L. The precision of the method was evaluated in terms of repeatability; the relative standard deviations varied from 2.7% to 11.2% (n=6). The relative recoveries ranged from 71.6% to 117.6% for all analytes. Only 3 of the 11 selected samples were tested positive for OPFRs, and the total concentrations of OPFRs in them were in the range of 2.6-3.4 μg/L. Hence, this method is accurate, environmentally friendly, fast, and convenient for the routine analysis of OPFRs in textile wastewater.
A rapid method for the determination of five organophosphorus flame retardants (OPFRs) in textile wastewater was established by dispersive liquid-liquid microextraction (DLLME) based on solidification of floating organic drop (SFO) coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The analytes were extracted from the water samples by SFO-DLLME, which was performed using a mixture of an extraction solvent that was less dense than water, 1-undecanol, and a dispersive solvent, methanol. The influences of the SFO-DLLME parameters on the extraction efficiencies were studied. 1-Undecanol (extraction solvent, 400 μL) and methanol (dispersive solvent, 300 μL) were added to textile wastewater (containing 2 g NaCl) with pH between 6 and 9, and the solution was shaken for 2 min. Under optimum conditions, the linear ranges of the proposed method were from 2 μg/L to 100 μg/L with correlation coefficients (R2) above 0.99 for all the analytes. The limits of detection (S/N=3) ranged from 2 μg/L to 5 μg/L. The precision of the method was evaluated in terms of repeatability; the relative standard deviations varied from 2.7% to 11.2% (n=6). The relative recoveries ranged from 71.6% to 117.6% for all analytes. Only 3 of the 11 selected samples were tested positive for OPFRs, and the total concentrations of OPFRs in them were in the range of 2.6-3.4 μg/L. Hence, this method is accurate, environmentally friendly, fast, and convenient for the routine analysis of OPFRs in textile wastewater.
2020, 38(6): 687-694
doi: 10.3724/SP.J.1123.2019.11003
Abstract:
A method was established for the determination of 64 pesticide residues in shellfish using accelerated solvent simultaneous extraction and purification coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS). The target compounds were extracted from shellfish using 90% (v/v) acetonitrile aqueous solution with 60% of the pool volume at 85℃ via a single cycle of accelerated solvent extraction. The extracts were synchronously purified with primary secondary amine (PSA) and graphitized carbon black (GCB) added to the extracting cell. After concentration, the target compounds were detected by GC-MS/MS in the multiple reaction monitoring (MRM) mode, and quantified by using the external standard method. Under the optimized conditions, good linearities were obtained for the 64 pesticides in the range of 10.0-1000 μg/L, with coefficients of determination greater than 0.989. The limits of quantification for the method were between 2.0 μg/kg and 10.0 μg/kg. At four spiked levels (5.0, 10.0, 100 μg/kg, and the LOQ level) in clam, the recoveries of all the pesticides were between 69.4% and 129.7%, with the relative standard deviations varying from 0.7% to 16.0% (n=6). The method is simple, repeatable and sensitive, and it is suitable for the screening of various pesticide residues in shellfish products.
A method was established for the determination of 64 pesticide residues in shellfish using accelerated solvent simultaneous extraction and purification coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS). The target compounds were extracted from shellfish using 90% (v/v) acetonitrile aqueous solution with 60% of the pool volume at 85℃ via a single cycle of accelerated solvent extraction. The extracts were synchronously purified with primary secondary amine (PSA) and graphitized carbon black (GCB) added to the extracting cell. After concentration, the target compounds were detected by GC-MS/MS in the multiple reaction monitoring (MRM) mode, and quantified by using the external standard method. Under the optimized conditions, good linearities were obtained for the 64 pesticides in the range of 10.0-1000 μg/L, with coefficients of determination greater than 0.989. The limits of quantification for the method were between 2.0 μg/kg and 10.0 μg/kg. At four spiked levels (5.0, 10.0, 100 μg/kg, and the LOQ level) in clam, the recoveries of all the pesticides were between 69.4% and 129.7%, with the relative standard deviations varying from 0.7% to 16.0% (n=6). The method is simple, repeatable and sensitive, and it is suitable for the screening of various pesticide residues in shellfish products.
2020, 38(6): 695-701
doi: 10.3724/SP.J.1123.2019.11030
Abstract:
A method based on precolumn derivatization along with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was developed for the determination of nitrapyrin and its metabolite, 6-chloropicolinic acid, in crops. The samples were extracted by acid acetonitrile, and subjected to precolumn derivatization using a sulfoacid. The quantification of the analytes was performed by the internal standard method. Good linear relationships between the peak areas and mass concentrations of the analytes were obtained in the range of 0.025-0.2 mg/L with correlation coefficients greater than 0.995 (n=6). The limits of quantification (LOQs) were 0.05 mg/kg. The recoveries of the analytes in crops at three spiked levels (0.05, 0.1, and 0.2 mg/kg) were in the range of 80.4%-98.4%, with relative standard deviations between 1.0% and 10.1% (n=6). This new method satisfies the related regulations for the determination of nitrapyrin and its metabolite in crops.
A method based on precolumn derivatization along with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was developed for the determination of nitrapyrin and its metabolite, 6-chloropicolinic acid, in crops. The samples were extracted by acid acetonitrile, and subjected to precolumn derivatization using a sulfoacid. The quantification of the analytes was performed by the internal standard method. Good linear relationships between the peak areas and mass concentrations of the analytes were obtained in the range of 0.025-0.2 mg/L with correlation coefficients greater than 0.995 (n=6). The limits of quantification (LOQs) were 0.05 mg/kg. The recoveries of the analytes in crops at three spiked levels (0.05, 0.1, and 0.2 mg/kg) were in the range of 80.4%-98.4%, with relative standard deviations between 1.0% and 10.1% (n=6). This new method satisfies the related regulations for the determination of nitrapyrin and its metabolite in crops.
2020, 38(6): 702-707
doi: 10.3724/SP.J.1123.2019.11012
Abstract:
A reliable gas chromatography-flame ionization detector (GC-FID) method was developed for the accurate determination of trace CO and CO2 in high concentration of SF6. Using a combination of dual Porapak Q chromatographic columns with valve switching, SF6 was separated from the tested samples and blown out of the detection system, with the aim of ruling out the possibility of conversion column poisoning. Meanwhile, CO and CO2 were on-line separated and subsequently converted to CH4 in the presence of a nickel catalyst to increase the sensitivity for the determination of carbon-borne gases. The results showed that neither gas interfered with the determination of the other. Satisfactory linearities were achieved in the range 2-500 μL/L for both CO and CO2, with highly accurate and reproducible determination (RSD<2%). The developed GC-FID method is applicable to the determination of gases lodged in high-voltage circuit breakers toward the analysis of trace CO and CO2, thus providing a tool for probing the potential breakdown of SF6-insulated equipment.
A reliable gas chromatography-flame ionization detector (GC-FID) method was developed for the accurate determination of trace CO and CO2 in high concentration of SF6. Using a combination of dual Porapak Q chromatographic columns with valve switching, SF6 was separated from the tested samples and blown out of the detection system, with the aim of ruling out the possibility of conversion column poisoning. Meanwhile, CO and CO2 were on-line separated and subsequently converted to CH4 in the presence of a nickel catalyst to increase the sensitivity for the determination of carbon-borne gases. The results showed that neither gas interfered with the determination of the other. Satisfactory linearities were achieved in the range 2-500 μL/L for both CO and CO2, with highly accurate and reproducible determination (RSD<2%). The developed GC-FID method is applicable to the determination of gases lodged in high-voltage circuit breakers toward the analysis of trace CO and CO2, thus providing a tool for probing the potential breakdown of SF6-insulated equipment.
2020, 38(6): 708-714
doi: 10.3724/SP.J.1123.2019.11029
Abstract:
A new method was established for the sensitive determination of artificial synthetic sweetener acesulfame-K in soy sauce by capillary electrophoresis (CE) with field-amplified sample injection (FASI)and capacitively coupled contactless conductivity detection (C4D). Liquid-liquid extraction (LLE) technology was employed to eliminate the complex matrix interference co-existing in soy sauce. Ethyl acetate was used as the extraction solution. The pH of the sample solution was adjusted to 1.7, and both inorganic salts and organic compounds causing interferences were effectively removed by LLE. The type and volume of the extraction solvents, pH of the sample solutions, extraction method and extraction time were investigated in detail. Under the optimized experimental conditions, acesulfame-K in soy sauce was well separated and sensitively detected. The limit of detection and limit of quantification were 0.15 mg/kg and 0.48 mg/kg, respectively. The accuracy was tested by spiking acesulfame-K into soy sauce samples, and the recoveries ranged from 92.3% to 108.1%. The relative standard deviations were below 8.0%. The proposed method can meet the requirements for the fast screening and sensitive detection of acesulfame-K in soy sauce samples.
A new method was established for the sensitive determination of artificial synthetic sweetener acesulfame-K in soy sauce by capillary electrophoresis (CE) with field-amplified sample injection (FASI)and capacitively coupled contactless conductivity detection (C4D). Liquid-liquid extraction (LLE) technology was employed to eliminate the complex matrix interference co-existing in soy sauce. Ethyl acetate was used as the extraction solution. The pH of the sample solution was adjusted to 1.7, and both inorganic salts and organic compounds causing interferences were effectively removed by LLE. The type and volume of the extraction solvents, pH of the sample solutions, extraction method and extraction time were investigated in detail. Under the optimized experimental conditions, acesulfame-K in soy sauce was well separated and sensitively detected. The limit of detection and limit of quantification were 0.15 mg/kg and 0.48 mg/kg, respectively. The accuracy was tested by spiking acesulfame-K into soy sauce samples, and the recoveries ranged from 92.3% to 108.1%. The relative standard deviations were below 8.0%. The proposed method can meet the requirements for the fast screening and sensitive detection of acesulfame-K in soy sauce samples.
2020, 38(6): 715-721
doi: 10.3724/SP.J.1123.2019.10031
Abstract:
A sensitive and accurate method was developed to quantify eight polycyclic aromatic hydrocarbon (PAH) metabolites in human urine by liquid-liquid extraction-high resolution gas chromatography-high resolution dual-focus magnetic mass spectrometry (LLC-HRGC-HRMS). About 2 mL urine was mixed with a deuterium- or 13C-labeled isotopic internal standard, and the conjugated targets were enzymatically digested in the presence of ascorbic acid. The free compounds were extracted with toluene-pentane (1:4, v/v) and condensed to near dryness. Then, the target compounds were redissolved in toluene. After derivatization, they were separated and quantified by HRGC-HRMS. The linear ranges of the 1-hydroxynaphthalene, 1-hydroxyphenanthrene, and 2-hydroxyphenanthrene were 0.14-41.6 μg/L, 0.05-8.33 μg/L, and 0.04-8.33 μg/L, respectively, and those for the other five PAH metabolites were 0.02-8.33 μg/L. The correlation coefficients were greater than 0.99. The limits of detection were in the range of 0.006-0.042 μg/L, and the recoveries were 81.4%-127.0%. The intra-day and inter-day relative standard deviations (RSDs) were less than 6.9% and 10.9%, respectively. This method was utilized for the determination of 330 human urine samples. The results showed that 3-hydroxychrysene and 6-hydroxychrysene were not detected, and the detection rate of the other six PAH metabolites was 100%. This method is sensitive, accurate and stable, and it is suitable for the determination of the eight PAH metabolites in human urine.
A sensitive and accurate method was developed to quantify eight polycyclic aromatic hydrocarbon (PAH) metabolites in human urine by liquid-liquid extraction-high resolution gas chromatography-high resolution dual-focus magnetic mass spectrometry (LLC-HRGC-HRMS). About 2 mL urine was mixed with a deuterium- or 13C-labeled isotopic internal standard, and the conjugated targets were enzymatically digested in the presence of ascorbic acid. The free compounds were extracted with toluene-pentane (1:4, v/v) and condensed to near dryness. Then, the target compounds were redissolved in toluene. After derivatization, they were separated and quantified by HRGC-HRMS. The linear ranges of the 1-hydroxynaphthalene, 1-hydroxyphenanthrene, and 2-hydroxyphenanthrene were 0.14-41.6 μg/L, 0.05-8.33 μg/L, and 0.04-8.33 μg/L, respectively, and those for the other five PAH metabolites were 0.02-8.33 μg/L. The correlation coefficients were greater than 0.99. The limits of detection were in the range of 0.006-0.042 μg/L, and the recoveries were 81.4%-127.0%. The intra-day and inter-day relative standard deviations (RSDs) were less than 6.9% and 10.9%, respectively. This method was utilized for the determination of 330 human urine samples. The results showed that 3-hydroxychrysene and 6-hydroxychrysene were not detected, and the detection rate of the other six PAH metabolites was 100%. This method is sensitive, accurate and stable, and it is suitable for the determination of the eight PAH metabolites in human urine.
2020, 38(6): 722-729
doi: 10.3724/SP.J.1123.2019.11005
Abstract:
β-casein (β-CN) is one of the major casein proteins in cow milk. There are 13 different variants documented for β-CN in cow milk, among which A1 and A2 are the major variants. The separation and quantitation of A2 β-CN are imperative for A2 dairy products. A new capillary zone electrophoresis (CZE) method with UV detection at 214 nm was established for the separation and quantification of the A2 variant and total β-CN content in cow milk and milk powders. The separation of β-CN variants was achieved on bare fused silica capillaries (50 μm×30/40 cm (effective/total length)). The separation buffer was a mixture of 4 mol/L urea, 0.2% (mass fraction) hydroxypropyl methylcellulose, 140 mmol/L citric acid, and 50 mmol/L disodium hydrogen phosphate buffer (pH 2.7). The corrected peak areas and the concentrations of total β-CN and the A2 variant showed good linearity, with correlation coefficients (r2) ranging from 0.9968 to 0.9997. The intra-day precisions for A2 β-CN and total β-CN determination in four samples (two pasteurized milk samples and two milk powder samples) were in the ranges of 2.4%-4.7% and 2.6%-4.8%, respectively. The inter-day precisions for A2 β-CN and total β-CN determination in four samples were in the ranges of 4.0%-6.3% and 3.9%-6.7%, respectively. The recoveries of A2 and total β-CN ranged from 85.5% to 106.4%. With the established CZE method, the A2 β-CN variant and total β-CN protein in liquid and powder bovine milk products could be separated and accurately quantified. By calculating the A2 β-CN content in the total β-CN, the quality of A2 dairy products can be evaluated, and this in turn would aid in the protection of consumer rights.
β-casein (β-CN) is one of the major casein proteins in cow milk. There are 13 different variants documented for β-CN in cow milk, among which A1 and A2 are the major variants. The separation and quantitation of A2 β-CN are imperative for A2 dairy products. A new capillary zone electrophoresis (CZE) method with UV detection at 214 nm was established for the separation and quantification of the A2 variant and total β-CN content in cow milk and milk powders. The separation of β-CN variants was achieved on bare fused silica capillaries (50 μm×30/40 cm (effective/total length)). The separation buffer was a mixture of 4 mol/L urea, 0.2% (mass fraction) hydroxypropyl methylcellulose, 140 mmol/L citric acid, and 50 mmol/L disodium hydrogen phosphate buffer (pH 2.7). The corrected peak areas and the concentrations of total β-CN and the A2 variant showed good linearity, with correlation coefficients (r2) ranging from 0.9968 to 0.9997. The intra-day precisions for A2 β-CN and total β-CN determination in four samples (two pasteurized milk samples and two milk powder samples) were in the ranges of 2.4%-4.7% and 2.6%-4.8%, respectively. The inter-day precisions for A2 β-CN and total β-CN determination in four samples were in the ranges of 4.0%-6.3% and 3.9%-6.7%, respectively. The recoveries of A2 and total β-CN ranged from 85.5% to 106.4%. With the established CZE method, the A2 β-CN variant and total β-CN protein in liquid and powder bovine milk products could be separated and accurately quantified. By calculating the A2 β-CN content in the total β-CN, the quality of A2 dairy products can be evaluated, and this in turn would aid in the protection of consumer rights.
