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Chinese Journal of Chromatography
2022, Vol. 40, No. 5
Online: 08 May 2022

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Research progress on interference in the identification of accelerants in a fire scene YIN Guo, QIAN Peiwen, LIQIU Fanzi, JIN Jing, LIU Ling, ZHANG Jinzhuan 2022, 40 (5):  401-408.  DOI: 10.3724/SP.J.1123.2021.10003 Abstract ( 225 )   HTML ( 179 )   PDF (1201KB) ( 94 )   Fire is one of the most common disasters threatening public safety and social development; arson, a typical violent crime, is a serious threat to people's lives and property. Suspects are likely to use accelerants to commit effective and rapid arson. Therefore, the identification of accelerants is of crucial importance in determining the nature of a fire. Fires are commonly complex and intricate, leading to remarkable interference in accelerant identification. During the development of a fire, thermal environment influences the preformed accelerant combustion residues, causing the characteristic components of the accelerant to volatilize/pyrolyze to different degrees, thus interfering with accelerant identification. There are numerous petrochemicals with characteristic components similar to those of accelerants in fire scenes, also contributing to the interference in the determination of the presence of accelerants. After the fire is extinguished, the combustion residues of the accelerant in the fire scene are influenced by the combined effects of heat, light, and pressure in the ambient environment, resulting in the loss of the mass fraction of characteristic components, mainly in the form of volatilization. In particular, with countless microorganisms in the soil, the characteristic components of the present accelerants are degraded, resulting in the reduction or absence of some components, which seriously influences the accuracy of accelerant identification. This study describes the progress of research on the interference in accelerant identification induced by various factors at fire scenes from four aspects: thermal environment, matrix interference, weathering effect, and microbial degradation, with emphasis on the interference from the first aspect. Based on the correlation between the matrix chemical composition/structure and interference degree, new results pertaining to the interference source in accelerant identification are also considered. The shortcomings of current research and the prospects for future research are put forward to provide a reference for accelerant identification at fire scenes. Many studies have been conducted on the above four types of interference in recent years, which provide important reference for accelerant identification regarding the arson caused by ignitable liquids. However, with the application of new materials and techniques, fire scenes have become increasingly complex, which demands higher requirements for accelerant identification in forensic science. Research on thermal environment interference is still in its infancy, and it is of great practical significance to conduct this research on other types of accelerants coupled with other interference factors. In addition, the principle of most of the current research on selecting objects is based on common appearance at fire scenes, rather than the functional group of the chemical structure of the matrix. Systematic and in-depth research on the interference law and mechanism is urgently required, and it is vital to further explore the interference law of the fire background from the perspective of the chemical composition and chemical structure of the substrate. Compared to foreign countries, there is less research on the interference of weathering and microbial effects on ignitable liquid identification in China. Most importantly, there is a lack of unified provisions, such as standard experimental methods to carry out such research, making it urgent to establish relevant standards and specifications. Additionally, while weathering is caused by multiple factors, the existing research on the interference of the weathering effect with ignitable liquid identification focuses merely on volatilization. Therefore, a more accurate experimental design is necessary. Improving the database of interferents under fire conditions, and combining the application of the chemometrics method for the artificial intelligence identification of the combustion residue spectrum, is an effective way to further improve the identification efficiency and accuracy.

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Determination of 44 foodborne stimulants and 6 progestogens in meat by QuEChERS and ultra-performance liquid chromatography-tandem mass spectrometry FENG Yuechao, WANG Jianfeng, HOU Fan, DING Qi, CHU Hongyu, LIU Yan 2022, 40 (5):  409-422.  DOI: 10.3724/SP.J.1123.2021.12005 Abstract ( 298 )   HTML ( 126 )   PDF (1792KB) ( 214 )   Supporting Information To ensure the success of large-scale sporting events, prevent the contamination of food by prohibited substances, and evaluate the risk of foodborne stimulants and other hormones in food, it is necessary to establish a high-throughput, rapid, and accurate detection method for foodborne stimulants and other hormones. In this study, a QuEChERS method is proposed for the simultaneous determination of 44 foodborne stimulants and 6 progestogens using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The analyzed foodborne stimulants include 19 β2-agonists, 3 β-blockers, 11 anabolic agents, 8 glucocorticoids, and 3 diuretics. A meat sample was crushed and homogenized, following which the internal standard was added. Subsequently, the sample was shaken and extracted with water and an acetonitrile solution containing 0.5% acetic acid, then dehydrated and centrifuged with sodium chloride and anhydrous magnesium sulfate. The supernatant was purified by PSA, C18, neutral alumina, and anhydrous magnesium sulfate. It was then dried with nitrogen and concentrated. The concentrated extracts were separated using an ACQUITY BEH C18 column (100 mm×2.1 mm, 1.7 μm) with gradient elution using 0.1% formic acid-5 mmol/L ammonium acetate solution and methanol as mobile phases. The target compounds were detected by ultra-performance liquid chromatography-tandem mass spectrometry with electrospray ionization and positive ion scanning (ESI+) in the multiple reaction monitoring (MRM) mode, and quantified by the internal standard method. The linear ranges of β2-agonists and β-blockers were 0.1-20 μg/L, the linear ranges of glucocorticoids were 0.5-200 μg/L, and those of the others were approximately 0.2-50 μg/L. The linear relationships of 50 compounds were good, with correlation coefficients >0.99 in the linear ranges, and limits of quantification (LOQs) in the range of 0.1-0.4 μg/kg. The recoveries of the 50 target compounds spiked in chicken, pork, beef, lamb samples at three levels ranged from 50.3% to 119.9%, while the relative standard deviations (RSDs, n=6) ranged from 0.42% to 15.1%. Nine meat samples (including 3 beef, 3 pork, 2 chicken, and duck samples) were tested by this method and the national standard method (GB/T 21981-2008). The t test was used for statistical analysis of the hydrocortisone and cortisone contents, and no significant difference was found between the results obtained by the two methods. The developed method was used to analyze 12 beef samples from a farm. In all, 4 compounds were detected, while the other 46 were not detected. The content ranges and detection rates of the compounds were as follows: hydrocortisone: 3.3-22.6 μg/kg, 100%; cortisone: 1.5-2.1 μg/kg, 67%; androstenedione: 0.7-1.2 μg/kg, 17%; and testosterone: 0.6-1.5 μg/kg, 42%. In conclusion, the proposed method is simple, accurate, and sensitive, and hence, is suitable for the detection of foodborne stimulants and progestogens in different kinds of raw meat.

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Determination and level investigation of 45 hormones in edible bird's nest by solid phase extraction-high performance liquid chromatography-tandem mass spectrometry XU Dunming, ZENG Sanmei, LIU Xuncai, WANG Luxiao, FAN Qunyan, ZHANG Xiaojiang, FANG Enhua 2022, 40 (5):  423-432.  DOI: 10.3724/SP.J.1123.2021.08008 Abstract ( 244 )   HTML ( 54 )   PDF (1819KB) ( 138 )   Edible bird's nests (EBNs), a food of animal origin, are temporary nests built by swiftlets to foster their offspring. As EBNs and their products are widely accepted by consumers, the safety of hormones in EBNs has also received increasing attention. The establishment of a method for hormone analysis in EBNs and the investigation of hormone levels based on the analytical method are the most effective measures to eliminate any safety concerns. In this study, a multi-residue method was developed for the simultaneous determination of 45 hormones in EBNs, including estrogens, progesterones, androgens, and cortical hormones. EBN samples (1.0 g) were weighed into 50 mL polypropylene centrifuge tubes and mixed with 8 mL of pure water. Then, the samples were extracted twice with 15 mL of acetonitrile and ethyl acetate (1∶1, v/v) under ultrasonic-assisted conditions for 30 min, and the protein in the EBN samples was precipitated at 4000 r/min for 5 min. The clear supernatants were loaded onto a hydrophilic-lipophilic balanced (HLB) SPE column, which was previously activated with methanol (3 mL) followed by pure water (3 mL). The cartridge was washed with 3 mL of pure water and 3 mL of 50% methanol aqueous solution. The hormones were eluted with 3 mL of methanol. A rapid analysis was performed using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The hormones in the extracting solution were separated on a Phenomenex Kinetex C18 column (100 mm×2.1 mm, 2.6 μm) and eluted by gradient elution with acetonitrile-0.1% formic acid aqueous solution (ESI+) or acetonitrile-water (ESI-). Qualitative and quantitative analyses were performed using the multiple reaction monitoring (MRM) mode. The HPLC-MS/MS results showed good linearity in the range of 0.20-20.0 μg/L with correlation coefficients (R2) ≥0.9990. For the 45 hormones, the limits of detection (LODs, S/N≥3) were 0.04-0.70 μg/kg and the limits of quantification (LOQs, S/N≥10) were 0.16-2.00 μg/kg. The recoveries of five hormones, namely, fluorometholone, budesonide, aldosterone, fluocinonide, and ethinylestradiol, were 40.2%-63.6%. Owing to the low recoveries, this method might be suitable only for qualitative testing of the five hormones. The recoveries of the other 40 target analytes were between 72.2% and 112.3% at spiked levels of 2.0, 4.0, and 20.0 μg/kg with relative standard deviations (RSDs) of 2.5%-11.6%. The method is characterized by easy operation, rapidness, high precision, and high sensitivity for the 40 compounds. Thus, this method is suitable for determination of the 40 hormones from EBNs for qualitative testing and quantitation. The proposed method was used to analyze 1021 EBN samples from Malaysia, Indonesia, Thailand, and Vietnam from 2017 to 2021. Only three hormones, progesterone, boldenone, and androstenedione, were identified in the EBN samples, while the levels of the other hormones were lower than their individual LODs. The detected rates of progesterone, boldenone, and androstenedione were 100%, 79%, and 89%, respectively. The contents of progesterone, boldenone, and androstenedione in the EBN samples were 0.097-3.58 μg/kg, 0-0.096 μg/kg and 0-1.77 μg/kg, respectively. The levels of hormones in EBNs were compared with those in eggs, pure milk, and dairy products, which were also animal-derived foods. Androstenedione was detected in all egg samples monitored, and its content was higher than that in EBN samples, pure milk, and dairy products. The content of boldenone was similar among the four products investigated in this study. Based on risk assessment using progesterone, the dietary intake was found to be 3.54 μg/d from milk >1.09 μg/d from eggs >0.0030 μg/d from EBNs. The results showed that the levels of hormones in EBNs were much lower than those in eggs, milk, and dairy products for daily consumption. Based on this investigation, the health effect of the hormones in EBNs may be insignificant.

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Fast screening and confirmation of 73 common prohibited compounds in cosmetics by ultra performance liquid chromatography-quadrupole-time-of-flight high resolution mass spectrometry LI Yangjie, HUANG Jiaying, FANG Jihui, HUANG Zhiye 2022, 40 (5):  433-442.  DOI: 10.3724/SP.J.1123.2021.09010 Abstract ( 235 )   HTML ( 40 )   PDF (4164KB) ( 162 )   Supporting Information A high throughput screening method based on ultra performance liquid chromatography-quadrupole-time-of-flight high resolution mass spectrometry (UPLC-Q-TOF HRMS) was developed for the simultaneous and rapid confirmation of 73 prohibited compounds in cosmetics. The sample was dispersed in a saturated sodium chloride solution and ultrasonically extracted using acetonitrile containing 0.2% (v/v) formic acid. The resultant solution was centrifuged and then cleaned using dispersive solid phase extraction using a primary secondary amine (PSA) sorbent. The purified solution was centrifuged, and the supernatant was filtered through a 0.22 μm membrane before determination. The optimal pretreatment method was determined by comparing the recovery rates obtained using different extraction solvents and different amounts of purifying agents. The chromatographic separation conditions and mass spectrometry scanning mode were also optimized. Chromatographic separation was performed on an Acquity UPLC HSS T3 column (100 mm×2.1 mm, 1.8 μm) with gradient elution using 0.1% (v/v) formic acid aqueous solution and methanol as mobile phases. The eluent from the column was further detected using Q-TOF HRMS with the high resolution multiple reaction monitoring (MRM HR) scanning mode. Retention time, precise mass of parent ion, isotope abundance ratio, and precise mass of fragment ions were the parameters considered for rapid untargeted screening and confirmation. The matrix effects of water- and cream-based cosmetics were investigated. The matrix effects could be addressed using the matrix matched standard curve method. The correlation coefficients for the 73 prohibited compounds were all >0.99 in the corresponding linear concentration range. The limits of detection (LODs) were in the range of 5-150 μg/kg, and the limits of quantification (LOQs) were in the range of 15-450 μg/kg. Average recoveries were in the range of 60.3%-130.3% at three spiked levels, and the intra-day and inter-day precisions were 0.8%-10.0% (n=6) and 1.1%-15.0% (n=3), respectively. A total of 692 cosmetics samples were screened; 16 positive samples were detected, namely, sulfamethoxazole, meprednisone, lincomycin, 4-acetamidophenol, trimethoprim, alfacalcidol, betamethasone 17-valerate, brimonidine, chloramphenicol, chlorpheniramine, clobetasol propionate, crotamiton, econazole, ketoconazole, prednisone 21-acetate, and prednisone, with content in the range of 0.5-1136.1 mg/kg. The optimized method is accurate, fast, and simple, and it is suitable for the routine detection and rapid screening of common prohibited compounds in cosmetics. In addition, a screening and confirmation library was established for the 650 prohibited compounds using SCIEX OS and Library View software, using information-dependent acquisition (IDA)-MS/MS mode for MS data acquisition. The database contains multiple types of information, including formulas, theoretical exact mass, retention time, precise mass of parent ion, isotope abundance ratio, and fragment ion distribution. The library can be used for the simultaneous and rapid confirmation of prohibited compounds in cosmetics.

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Highly sensitive determination of three kinds of amanitins in urine and plasma by ultra performance liquid chromatography-triple quadrupole mass spectrometry coupled with immunoaffinity column clean-up ZHANG Xiuyao, CAI Xinxin, ZHANG Xiaoyi, LI Ruifen, ZHAO Yunfeng 2022, 40 (5):  443-451.  DOI: 10.3724/SP.J.1123.2021.08018 Abstract ( 207 )   HTML ( 34 )   PDF (1360KB) ( 89 )   Supporting Information Cases of toxic mushroom poisoning occur frequently in China every year. In particular, mushrooms containing amanitins can cause acute liver damage, with high mortality rates. The symptoms of acute liver damage are experienced 9-72 h after consumption of the mushrooms. At this time, the concentration of amanitins in blood and urine is too low to be detected even by the highly sensitive ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS), thus rendering clinical diagnosis and treatment difficult. To this end, a method was developed for the determination of α-amanitin, β-amanitin and γ-amanitin in urine and plasma by UPLC-MS/MS. Urine and plasma samples were extracted and cleaned up by using an immunoaffinity column. A sample of 2.00 mL urine or 1.00 mL of plasma was diluted with 8.00 mL of phosphate buffer solution (PBS) and then loaded onto the immunoaffinity column at a flow rate of 0.5-1.0 mL/min. After washing the column with 10 mL of PBS and 13 mL of water successively, the bound amanitins were eluted with 3.00 mL of methanol-acetone (1∶1, v/v). The eluent was dried under nitrogen at 55 ℃. The residue was dissolved in 100 μL of 10% (v/v) methanol aqueous solution. The amanitins in urine were concentrated 20 times, while those in plasma were concentrated 10 times. Chromatographic separation was performed on a Kinetex Biphenyl column (100 mm × 2.1 mm, 1.7 μm) with gradient elution using methanol and 0.005% (v/v) formic acid aqueous solution as mobile phases. The three amanitins were detected by negative electrospray ionization tandem mass spectrometry in the multiple reaction monitoring (MRM) mode and quantified by the solvent standard curve external standard method. Method validation was performed as recommended by the European Drug Administration (EMEA). Four levels of quality control (QC) samples were prepared, which covered the calibration curve range, viz., the limit of quantification (LOQ), within three times the LOQ (low QC), medium QC, and at 85% of the upper calibration curve range (high QC), and used to test the accuracy, precision, matrix effect, extraction recovery, and stability. The calibration curves for the three amanitins showed good linear relationships in the range of 0.1-200 ng/mL, and the correlation coefficients (r) were greater than 0.999. The matrix effects and extraction efficiencies of the three amanitins in urine and plasma were 92%-108% and 90%-103%, respectively, and the coefficients of variation were less than 13%. The accuracies of the three amanitins in urine were within -9.4%-8.0%. The repeatability and intermediate accuracies were 3.0%-14% and 3.5%-18%, respectively. When the sampling volume was 2.00 mL, the limits of detection of the three amanitins in urine were 0.002 ng/mL. The accuracies of the three amanitins in plasma were within -13%-8.0%. The repeatability and intermediate accuracies were 3.9%-9.7% and 5.5%-12%, respectively. When the sampling volume was 1.00 mL, the limits of detection of the three amanitins in plasma were 0.004 ng/mL. The developed method is simple, sensitive, and accurate. During toxic mushroom poisoning detection, 0.0067 ng/mL of α-amanitin and 0.0059 ng/mL of β-amanitin were detected in the urine of poisoned patients 138 h after ingesting poisonous mushrooms. This method has successfully solved the problem of detecting ultra-trace levels of amanitins in the urine and plasma of poisoned patients. It has important practical significance for the early diagnosis, early treatment, and mortality reduction of suspected poisoning patients. This method can also provide reliable technical support for future research on the toxicological effects and in vivo metabolism of these toxins.

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Determination of 82 polychlorinated biphenyls in biological samples using accelerated solvent extraction-isotope dilution-high resolution gas chromatography-high resolution mass spectrometry WU Yinju, QU Bailu, HOU Yulan, YU Haibin, XU Renji, ZHENG Xiaoyan 2022, 40 (5):  452-460.  DOI: 10.3724/SP.J.1123.2021.10018 Abstract ( 173 )   HTML ( 32 )   PDF (1085KB) ( 96 )   Supporting Information In China, the detection methods for polychlorinated biphenyls (PCBs) in aquatic products are mainly effective for 6 indicative PCBs and 12 coplanar dioxin-like PCBs, which only account for a limited proportion of PCBs in organisms. In this study, to obtain the detailed concentration levels of PCBs in organisms, elucidate the metabolism and enrichment characteristics of PCBs in organisms, and accurately evaluate the exposure level and risks of PCBs to humans, an improved method for the simultaneous determination of 82 PCBs in fish and shellfish samples was developed using isotope dilution-high resolution gas chromatography-high resolution mass spectrometry (ID-HRGC-HRMS). The recovery and reproducibility of two extraction methods, i. e., oscillatory extraction and accelerated solvent extraction (ASE), were compared. Finally, ASE was chosen for subsequent experiments. Specifically, after adding 1 ng13C-labeled extraction internal standards, the samples were extracted under pressure by ASE using a mixture of n-hexane-dichloromethane (1∶1, v/v). The experimental conditions employed for this were a pressure of 10.3 MPa, heating temperature of 100 ℃, heating time of 5 min, static time of 8 min, flush volume of 60%, purging time of 120 s, and 34 mL cells. Subsequently, the extracts were loaded on an 8 g acid silica gel (44%) column (inner diameter: 15 mm) and eluted with 90 mL of n-hexane. After purification and concentration, the analytes were determined by HRGC-HRMS with a fused-silica capillary column (DB-5MS, 60 m×0.25 mm×0.25 μm). The temperature program was optimized to separate the most target compounds at the baseline. Specifically, the initial oven temperature was 120 ℃, which was held for 1 min, following by heating to 180 ℃ at 30 ℃/min, heating to 210 ℃ at 2 ℃/min and holding for 1 min, and further heating to 310 ℃ at 2.5 ℃/min and holding for 1 min. The injector and ion source temperatures were 270 ℃ and 280 ℃, respectively. With a static resolution of 10000, the HRMS instrument was operated in the selected-ion monitoring mode at an electron energy of 35 eV. The 82 PCBs were qualified by their retention time and two characteristic ions, and thereafter quantified using the mean relative corresponding factor (RRF). The results showed that the relative standard deviation (RSD) of the RRF obtained from six-point calibration standard solutions was less than 20%. The linearity ranges were from 0.1 to 200 μg/L, and the correlation coefficients (r2) were greater than 0.99. Under optimum conditions, the method detection limits (MDLs) for the PCBs of biological samples were in the range of 0.02-3 pg/g. To validate the method, the fish and shellfish samples were spiked with a low level (0.4 ng) and high level (3.6 ng) of native PCB standards. The spiked recoveries using low-concentration native PCBs were 71.3%-139% in fish and 76.9%-143% in shellfish, and the RSDs (n=7) were 2.1%-14% and 4.5%-14%, respectively. The spiked recoveries using high-concentration native PCBs were 77.6%-141% and 82.2%-131%, respectively, and the RSDs (n=7) were 1.4%-9.4% and 1.7%-11%, respectively. An analysis of fresh fish and shellfish samples showed that the contents of a single PCB ranged from “not detected” to 54.1 pg/g, where 12 coplanar dioxin-like PCBs were detected in the range of 12.6 pg/g to 74.5 pg/g, six indicative PCBs in the range of 30.9 pg/g to 62.1 pg/g, and 82 PCBs in the range of 174 pg/g to 672 pg/g. It was concluded that this method could be successfully applied for the determination of PCBs in biological samples with good accuracy and precision. This comprehensive analytical method of PCBs in aquatic products provides effective technical support for biological monitoring; it will also aid in ecological and environmental management and the implementation of the Stockholm Convention policies.

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Simultaneous determination of 35 organochlorine pesticides and polychlorinated biphenyls in the serum of the general population in Wuhan by solid phase extraction-gas chromatography-tandem mass spectrometry LI Xiang, WANG Limei, SONG Lulu, WAN Zhengce, KOU Jing, ZHANG Mingye, LÜ Yongman, WANG Youjie, MEI Surong 2022, 40 (5):  461-468.  DOI: 10.3724/SP.J.1123.2021.12013 Abstract ( 184 )   HTML ( 199 )   PDF (1240KB) ( 113 )   Owing to their persistence, ease of accumulation in organisms, and high toxicity, the use of persistent organic pollutants (POPs) has been limited ever since the Stockholm Convention on Persistent Organic Pollutants was signed in 2001 by the United Nations Environment Programme (UNEP). As typical POPs, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) can persist in the environment for long periods. They can enter human bodies through many pathways and pose a high exposure risk to humans. OCPs and PCBs can lead to endocrine disruption, neurotoxicity, immunotoxicity, reproductive toxicity, and cancer in human beings. Accurate quantification of pollutant load levels in vivo is crucial for the evaluation of health effects. In this study, a rapid and sensitive method based on solid phase extraction-gas chromatography-tandem mass spectrometry (SPE-GC-MS/MS) was developed for the simultaneous determination of 35 OCPs and PCBs in serum. Accordingly, 100 μL of the serum sample was gently mixed with the isotope-labeled internal standard solution (10 μL) to obtain a final mass concentration of 10 ng/mL for each internal standard. After incubation overnight, the samples were mixed with 100 μL purified water for dilution. After protein precipitation with 100 mg urea, the serum samples were passed through preconditioned Oasis® HLB cartridges, washed with 6 mL purified water, and eluted with 5 mL hexane-dichloromethane (1∶1, v/v). The SPE eluant was collected, evaporated to near dryness under a gentle nitrogen stream, and dissolved in 100 μL n-hexane. The reconstitution in the vial insert was injected into the GC-MS/MS instrument for analysis. The analytes were separated on an Agilent J&W DB-5MS capillary column (30 m×0.25 mm×0.25 μm) with temperature programming. The mass spectrometer was operated in the electron ionization (EI) mode. The optimal mass spectrometry conditions were realized by optimizing the instrument parameters such as ion pairs and collision energies. The analytes were detected in the multiple reaction monitoring (MRM) mode, and the internal standard method was used for quantitative analysis. The OCPs and PCBs had good linearities in the range of 0.05-50.0 ng/mL. The limits of detection (LODs, S/N=3) ranged from 1.2 to 71.4 ng/L. The recoveries of the 35 compounds were 72.6%-142% with relative standard deviations (RSDs) of less than 25% at the three spiked levels. The developed SPE-GC-MS/MS method was successfully applied to the simultaneous analysis of OCPs and PCBs in serum samples obtained from the general population in Wuhan. The results showed that the general population in Wuhan was widely exposed to OCPs and PCBs, especially the former. The detection frequencies of eight OCPs and seven PCBs were greater than 50%, and p,p'-DDE, p,p'-DDD, and methoxychlor were detected in all serum sample pools. Non-dioxin-like PCBs (NDL-PCBs) were the dominant PCB congeners, while PCB-28, PCB-153, and PCB-52 were the dominant PCBs in the general population of Wuhan. The concentration of OCPs increased with age. Moreover, the concentration of OCPs in individuals who were more than 66 years old was significantly higher as compared to that in younger individuals. The positive association differing by gender was significant in individuals over 60 years of age. There were no significant differences in PCB concentrations according to gender or age. There were no seasonal differences in the residue levels of OCPs and PCBs in the general population of Wuhan. The developed method is rapid and sensitive; it has the advantages of low limits of detection, satisfactory recoveries, accurate precision, and microsample volume, thus allowing for the simultaneous analysis of trace OCPs and PCBs in microserum samples in epidemiological studies. This robust analytical method also provides a powerful tool for the health risk assessment of OCP and PCB exposure.

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Modified QuEChERS method based on multi-walled carbon nanotubes coupled with gas chromatography-tandem mass spectrometry for the detection of 10 pyrethroid pesticide residues in tea XU Ruihan, XIE Qianwen, LI Xujun, ZHAO Hongli, LIU Xuebin, WEI Yuanlong, QIU Aidong 2022, 40 (5):  469-476.  DOI: 10.3724/SP.J.1123.2021.11015 Abstract ( 261 )   HTML ( 54 )   PDF (4365KB) ( 156 )   A modified QuEChERS method, based on multi-walled carbon nanotubes (MWCNTs), was established for the detection of 10 pyrethroid pesticides (cyfluthrin, flucythrinate, fenpropathrin, bifenthrin, cyhalothrin, permethrin, cypermethrin, etofenprox, fenvalerate, deltamethrin) in tea, in combination with gas chromatography-tandem mass spectrometry (GC-MS/MS). The purification effects and dosages of four carbon nanomaterials, viz. single-walled carbon nanotubes (SWCNTs), MWCNTs, amino-modified MWCNTs, and graphene, were compared. An orthogonal experimental design was used to determine the optimal experimental conditions for sample pretreatment. The experimental factors governing the process were analyzed using variance. The results showed that the optimized sample pretreatment parameters were as follows. Acetonitrile was used as the extraction solvent with ultrasonic extraction for 35 min, while 60 mg MWCNTs, 200 mg PSA, and 200 mg C18, were used as purifiers. The effects of the extraction solvent and the carbon nanomaterials used on the recoveries of the 10 pyrethroid pesticides were significantly different (p<0.001), and the effect of extraction time on the recoveries was statistically different (p<0.05). The dosage of carbon nanomaterials had no significant effect on the recoveries (p>0.05). Good linearities were observed for the 10 pyrethroid pesticides in the concentration range of 0.01-2 mg/L. The limits of detection (LODs) and limits of quantification (LOQs) were in the ranges of 0.001-0.01 mg/kg and 0.005-0.04 mg/kg, respectively. The average recoveries of the pyrethroid pesticides spiked into blank samples of green tea were 91.4%-109.7%, and the relative standard deviations were 0.12%-9.80% (n=6). Furthermore, the matrix effects (MEs) of scented green tea, green tea, and black tea were evaluated. It was found that the addition of MWCNTs to the purifier can effectively reduce the matrix effect in green tea and black tea matrices. The developed method and the national standard method were used to detect the residues of the 10 pyrethroid pesticides in 120 tea samples available in the market. The results showed that cyfluthrin, deltamethrin, fenvalerate, permethrin, fenpropathrin, cypermethrin, bifenthrin and cyhalothrin were detected, and the contents obtained with the two methods were similar. Although pyrethroids were detected in most tea samples, the contents of all pesticide residues were below the maximum residue limits (MRLs). Therefore, the developed method is suitable for the rapid quantitative analysis of pesticide residues in tea.

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Determination of 19 chlorophenols in fish by QuEChERS-gas chromatography-mass spectrometry MU Yinghua, XING Jiali, SHEN Jian, YING Lu, MAO Lingyan, XU Xiaorong, LOU Yongjiang, WU Xi 2022, 40 (5):  477-487.  DOI: 10.3724/SP.J.1123.2021.12002 Abstract ( 277 )   HTML ( 39 )   PDF (2184KB) ( 108 )   With the increasing use of chlorine-containing pesticides, hypochlorous acid disinfection water as well as aquatic product insecticides and fungicides are widely used in the cultivation of fish. This has led to the contamination of fish by chlorophenol compounds. However, currently, there is no standard method for the simultaneous determination of 19 chlorophenol compounds in fish. In this study, the optimum chromatography and mass spectrometry conditions were determined by investigating the instrument parameters. The 19 chlorophenol compounds were well separated using the DB-5MS capillary chromatographic column (30 m×0.25 mm×0.25 μm) with a carrier gas flow rate of 1 mL/min. Under this condition, the chromatographic peak was sharp and symmetric. An analytical method was developed for the simultaneous determination of the 19 chlorophenol compounds in fish using gas chromatography-mass spectrometry coupled with QuEChERS pretreatment. The improved QuEChERS method was used in sample preparation. The 19 chlorophenol compounds were extracted with organic solvents and purified with purifying agents. During the experiment, the effect of the kinds and volumes of the extraction solvent, as well as the types and dosages of the purifying agent, on the recoveries of the 19 chlorophenol compounds were investigated. Moreover, the temperature and time of derivatization, as well as the dosage of the derivatization agent, were optimized. All aforementioned analyses were conducted with the aim of determining the optimal pretreatment method. Finally, the optimized gas chromatography-mass spectrometry conditions were employed for the quantitative determination of 19 chlorophenol compounds in fish samples. Based on the experimental results, the best extraction method was determined to be the one where the extraction agent (10 mL ethyl acetate) was added to 3 g sodium chloride and 5 g anhydrous magnesium sulfate in the test tube, followed by ultrasonication for 15 min. The sample was centrifuged at 4500 r/min for 5 min, and 500 mg C18 was selected as the purifying agent to purify the supernatant. The purified supernatant was blown with nitrogen to less than 1 mL at 45 ℃, and then redissolved with ethyl acetate to 1 mL. Subsequently, the sample solution was passed through a 0.22 μm organic filter membrane, following which 50 μL bis(trimethylsilyl)trifluoroacetamide was added for derivatization at 45 ℃ for 30 min. Lastly, the 19 chlorophenol compounds were determined by gas chromatography-mass spectrometry with an electrospray ionization source and selecting ion monitoring mode. The 19 chlorophenol compounds were then quantitatively analyzed by the external standard method. The compounds showed good linearity in the concentration range of 0.4-10 μg/L, with correlation coefficients (R2) greater than 0.998. The limits of detection and limits of quantification were 0.01-0.05 μg/kg and 0.04-0.16 μg/kg, respectively. Moreover, the average recoveries of the 19 chlorophenol compounds were in the range of 70.6%-115.0% at three spiked levels, and the relative standard deviations were in the range of 2.6%-10.5%. The established method in this study was applied to detect and analyze chlorophenol compounds in actual samples. The experimental results showed that various levels of chlorophenol compounds could be detected in different fishes. Among them, the total amount of chlorophenol compounds detected in the Corvina was 8.74 μg/kg, followed by the Crucian carp at 7.59 μg/kg, and the minimum detected amount in rice fish (1.59 μg/kg). With its simple operation, high sensitivity, and good repeatability, the established method simplifies the pre-treatment of fish samples. It can also meet the requirements for the high-throughput detection of 19 chlorophenol compounds in fish, thereby significantly improving the detection efficiency of chlorophenols. Moreover, the method provides crucial technical support and a theoretical basis for the establishment of feasible detection standards for chlorophenols in China, as well as for the control of residue levels of chlorophenol compounds in fish. The findings have important practical significance to implement management measures during fish breeding and transportation.

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Improved generalized regression neural network for quantitative analysis of crude oil density by gas chromatography LIANG Haibo, DING Shuai, WEI Qi, ZOU Jialing 2022, 40 (5):  488-495.  DOI: 10.3724/SP.J.1123.2021.12001 Abstract ( 172 )   HTML ( 31 )   PDF (1457KB) ( 54 )   In the field of oil and gas exploration and development, the quick identification of reservoir crude oil properties has a guiding significance for engineers and technicians. Geochemical logging technology is a conventional method to evaluate the properties of crude oil in reservoirs, and it can provide professional knowledge for comprehensive evaluation of reservoirs. In this study, the principles of rock pyrolysis and gas chromatographic analyses in geochemical logging are studied. Moreover, a new method for quantitative analysis of crude oil density by chromatogram is proposed. Combined with the division standard of crude oil property density, the properties of reservoir crude oil can be quickly evaluated. In the experiment, first, the chromatogram was standardized and normalized using computer image processing software. The curve characteristic law of rock pyrolysis gas chromatogram was analyzed, and the corresponding characteristic parameter extraction method was proposed. The chromatogram was converted into a characteristic parameter matrix. Second, three types of artificial intelligence prediction and classification models were studied. The latest meta-heuristic optimization algorithm (sparrow search optimization algorithm) was used to optimize the hyperparameters of the generalized regression neural network, and the accuracy and convergence speed of the model were improved. To study the influence of different positions of rock samples on the experimental results, two groups of samples were utilized: cuttings samples and wall core samples. Based on a comprehensive comparison of the prediction results of the three models, it was found that the generalized regression neural network prediction model optimized by sparrow search algorithm provided the best effect, being a stable model, with small prediction density error, and strong generalization ability. The prediction error coincidence rate (absolute error < 0.02) of this model for cuttings and wall core samples was 95% and 100%, respectively. The root mean square errors were 0.0079 and 0.0069 respectively. The classification accuracy of crude oil properties was 95%. The analysis of the two groups of parallel experimental data indicated that the rock samples from the wall center can more accurately reflect the crude oil properties of the reservoir. Therefore, the method proposed in this study can provide reliable data support for reservoir comprehensive evaluation and on-site construction.