A nomogram prediction model for postoperative seroma/hematoma in elderly subjects after TAPP.

BACKGROUND: Formation of seroma/hematoma is one of the most common postoperative complications following laparoscopic inguinal hernia repair. This study aimed to identify risk factors associated with seroma/hematoma and construct a prediction model. METHODS: Elderly subjects undergoing laparoscopic Transabdominal preperitoneal Patch Plasty (TAPP) were included in this study. The observation endpoint was set as the occurrence of seroma/hematoma within 3 months after TAPP surgery. Independent risk factors were identified through preliminary univariate screening and binary logistic regression analysis. These risk factors were then used to construct a nomogram predictive model using R software. RESULTS: A total of 330 patients were included in the analysis, of which 51 developed seroma/hematoma, resulting in an incidence rate of 15.5%. Obesity (OR: 3.54, 95%CI: 1.45-8.66, P = 0.006), antithrombotic drug use (OR: 2.73, 95%CI: 1.06-7.03, P = 0.037), C-reactive protein (CRP) ≥ 8 (OR: 2.72, 95%CI: 1.04-7.10, P = 0.041, albumin/fibrinogen ratio (AFR) < 7.85 (OR: 2.99, 95%CI: 1.28-7.00, P = 0.012), and lymphocyte/monocyte ratio (LMR) < 4.05 (OR: 12.62, 95%CI: 5.69-28.01, P < 0.001) were five independent risk factors for seroma/hematoma. The nomogram model has well predictive value for seroma/hematoma, with an AUC of 0.879. CONCLUSIONS: The nomogram model based on obesity, antithrombotic drug, CRP, AFR, and LMR has a proved good predictive value and it has potential in clinical practice.

Modified Frailty Index and Albumin-Fibrinogen Ratio Predicts Postoperative Seroma After Laparoscopic TAPP.

Background: Postoperative seroma is the most common minor complication after inguinal hernia repair surgery and can have negative consequences. The objective of this study was to identify potential risk factors for postoperative seroma. Methods: This study consecutively included 354 elderly patients with inguinal hernia who underwent laparoscopic Transabdominal preperitoneal Patch Plasty (TAPP). Seroma diagnosis was conducted by the same experienced surgeon based on the physical examinations combined with ultrasound. Risk factors for seroma were identified through univariate analysis and subsequently included in the binary multivariate logistic regression model. Results: A total of 40 patients experienced postoperative complications of seroma, with an incidence rate of 11.3% (40/354). The binary logistic regression analysis revealed that obesity (OR: 2.98, 95% CI: 1.20-7.41, P = 0.018), disease duration ≥ 4.5 years (OR: 4.88, 95% CI: 2.14-11.18, P < 0.001), albumin-fibrinogen ratio (AFR) level < 9.25 (OR: 6.13, 95% CI: 2.00-18.76, P = 0.001), and modified frailty index (mFI) score ≥ 0.225 (OR: 6.38, 95% CI: 2.69-15.10, P < 0.001) were four independent risk factors for postoperative seroma. Conclusion: Obesity, prolonged disease duration, decreased AFR level, and increased mFI score independently predict postoperative seroma after laparoscopic TAPP.

[Determination of four fatty acid ethyl esters in olive oil by solid phase extraction-gas chromatography].

The fatty acid ethyl ester (FAEE) content of olive oil is an important indicator of its quality. At present, the international standard method used to detect FAEEs in olive oil is silica gel (Si) column chromatography-gas chromatography (GC); however, this technique presents a number of disadvantages, including complex operation, long analysis times, and high reagent consumption. In this study, a method based on Si solid phase extraction (SPE)-GC was established to determine four FAEEs in olive oil, namely, ethyl palmitate, ethyl linoleate, ethyl oleate, and ethyl stearate. First, the effects of the carrier gas were investigated, and He gas was ultimately selected as the carrier gas. Next, several internal standards were screened, and ethyl heptadecenoate (cis-10) was determined as the optimal internal standard. The SPE conditions were also optimized, and the effects of different brands of Si SPE columns on the recoveries of analytes were compared. Finally, a pretreatment method in which 0.05 g of olive oil was extracted with n-hexane and purified through a Si SPE column (1 g/6 mL) was developed. A sample could be processed within approximately 2 h using a total reagent volume of about 23 mL. Validation of the optimized method revealed that the four FAEEs have good linearities within the range of 0.1-5.0 mg/L (coefficients of determination (R2)>0.999). The limits of detection (LODs) of the method were within 0.78-1.11 mg/kg, and its limits of quantification (LOQs) were in the range of 2.35-3.33 mg/kg. The recoveries ranged from 93.8% to 104.0% at all spiked levels tested (4, 8, and 20 mg/kg), and the relative standard deviations were 2.2%-7.6%. Fifteen olive oil samples were tested using the established method, and the total FAEEs of three extra-virgin olive oil samples were found to exceed 35 mg/kg. Compared with the international standard method, the proposed method has the advantages of simpler pretreatment process, shorter operation time, lower reagent consumption and detection cost, high precision, and good accuracy. The findings provide an effective theoretical and practical reference for improving olive oil detection standards.

[Determination of free amino acids in Eriocheir sinensis by ultra-high performance liquid chromatography-high resolution mass spectrometry].

Eriocheir sinensis is a unique freshwater crab found in China, which is well known for its rich nutrition and sweet and delicious taste. Free amino acids in Eriocheir sinensis are not only important nutrients but also are closely related to their unique taste and aroma. Therefore, the determination of the free amino acid contents in Eriocheir sinensis is of great significance for product quality evaluation, flavor research, authenticity, and origin identification. Herein we proposed an ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS)-based method for the determination of 17 free amino acids in Eriocheir sinensis. First, 5 g of the Eriocheir sinensis sample was weighed into a 50-mL polypropylene centrifuge tube. Then, 10 mL of extraction solvents was added to the centrifuge tube, and the resultant solution was mixed well using a vortex mixer. We compared a variety of solvents and finally selected 5%(v/v) perchloric acid aqueous solution as the optimum extraction solvent. The supernatant was transferred to another polypropylene centrifuge tube after centrifuging at 8000 r/min for 5 min. The extraction procedure was repeated according to the above-mentioned steps, and the extraction solution was combined with the supernatant. The extracts were then adjusted to pH 6.5 with 1 mol/L potassium hydroxide solution, and were diluted to 50 mL with water. After filtering by both qualitative filter paper and a 0.45-µm polyether sulfone syringe filter, the extracts were determined by UHPLC-HRMS. We compared three types of mobile phases and chose 0.1%(v/v) formic acid aqueous solution mixed with acetonitrile as the optimum one. Precise parent ion and ion source parameters were also optimized. The 17 analytes, viz. aspartic acid, threonine, serine, glutamic acid, proline, cystine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, lysine, arginine, glycine, alanine, and histidine, were separated on an XDB-C18 column (100 mm×4.6 mm, 1.7 µm) with gradient elution. The amino acids were then detected by HRMS in electrospray ionization and selected ion monitoring modes, and the analytes were quantified using external standards. The instrumental detection limit (IDL) and the instrumental quantification limit (IQL) were 0.3 mg/L and 1.0 mg/L, respectively. The linear correlation coefficients were all above 0.9990 in the concentration range of 10.0-200.0 mg/kg. Three levels of free amino acid standards were spiked into the edible parts of Eriocheir sinensis. The recoveries of the amino acids were between 78.4% and 105.3%. The intra-sample, intra-day, and inter-day repeatabilities were below 4.2%, 5.2%, and 11.4%, respectively, which were within reasonable ranges. Twenty samples of Eriocheir sinensis were tested using the proposed method. Thus, in this study, we developed an alternative method for the determination of free amino acids in Eriocheir sinensis with simple pretreatment, good selectivity, and high accuracy.

[Determination of four trihalomethanes in ship ballast water by gas chromatography-negative chemical ionization-mass spectrometry].

Ship ballast water can control the roll, trim, and draft of the ship, and thus ensuring the balance and stability of the ship in the course of sailing, and playing a vital role in the safe navigation of ships. The annual discharge of ship ballast water is very large in China. About three to five billion cubic meters of ship ballast water is discharged into offshore or inland waters every year. This water contains plankton, pathogens, and their larvae or spores. If not be handled appropriately, this will have a serious impact on the ecological environment of the discharge waters. Ballast water is usually treated by electrolysis before being discharged. Sodium hypochlorite can be generated, which can kill microorganisms; however, the by-products trihalomethanes (THMs) are cytotoxic and biotoxic. Studies have shown that THMs may cause fetal growth retardation, spontaneous abortion, or death. The concentration of THMs in drinking water is closely related to the risk of bladder cancer death. Hence, it is important to establish a method for the determination of THMs in ship ballast water. The four kinds of THMs are chloroform, dichlorobromomethane, chlorodibromomethane, and tribromomethane. At present, ship ballast water is mostly analyzed by gas chromatography (GC) using an electron capture detector (ECD) or by gas chromatography-mass spectrometry (GC-MS). Given the low boiling point of THMs, headspace injection and purge-and-trap can be used. Gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS), was adopted. NCI is a soft ionization technique that shows special response to compounds bearing electronegative elements or groups. THMs contain electronegative chlorine atoms and bromine atoms. Therefore, NCI is a good choice for their analysis. The samples were processed by the headspace injection technique. The NaCl content in 10 mL sample was optimized in headspace injection. The results showed that 3.0 g NaCl was the most suitable dosage. The analytes were separated on a DB-5MS UI capillary-column (30 m×0.25 mm×1.0 µm). The target compounds were quantified by using the external standard method in selected ion monitoring (SIM) mode. The four THMs were not only well separated but also showed a high response at 0.2 µg/L. The four THMs showed good linear relationships in the range of 0.2-50 µg/L, with correlation coefficients≥0.995. The limits of quantification (LOQs, S/N=10) were 0.1-0.2 µg/L, and the average recoveries of the four THMs were 90.3%-106.8% at the three spike levels of 0.2, 0.5, and 2.0 µg/L. The relative standard deviations were 1.4%-6.2%. The LOQs of the THMs in the GB/T 5750.8-2006 Standard Test Method of Drinking Water Organic Matter Index are 0.3-6.0 µg/L. It can be seen that the LOQs of the THMs are greatly reduced in this study. The proposed method is accurate, stable, and reliable, and it can be used for monitoring the four THMs in ship ballast water. The method was applied for the detection of 36 ship ballast water samples. In all cases, the detection rates of tribromomethane, chlorodibromomethane, dichlorobromomethane, and chloroform were 83.3%, 69.4%, 22.2%, and 19.4%, respectively. The detection values of tribromomethane, chlorodibromomethane, dichlorobromomethane, and chloroform were 34.25-221.5 µg/L, 3.52-41.87 µg/L, 1.52-8.56 µg/L, and 0.02-5.46 µg/L, respectively. Based on the analysis of several ship ballast water samples (electrolytic water), it was concluded that the greater the number of bromine atoms in the THMs, the higher are the detection rate and detection value in ship ballast water. Compared to chloroform, tribromomethane is more harmful to living beings. China has acceded to the International Convention on Ship Ballast Water and Sediment Control and Management. There is an urgent need to establish analysis methods with high sensitivity, good stability, and high accuracy in addition to determining standards and regulations for ship ballast water.

Research method of rapid determination of chiral pesticide fenpropathrin enantiomers in fruit and vegetable puree by supercritical fluid chromatography.

A method is first established for the separation and determination of fenpropathrin enantiomer residues in apple puree, strawberry puree, and tomato puree considered a supplementary food for infants by supercritical fluid chromatography. After the sample was extracted with acetonitrile and cleaned up by a solid-phase extraction column, then it was separated by a CHIRALPAK AD-3 chiral column with gradient elution at a flow rate of 1.5 mL/min using methanol and supercritical carbon dioxide as the mobile phase, detected by ultraviolet detector at 230 nm wavelength and quantified with the external standard method. The limits of quantification of the two fenpropathrin enantiomers were both 0.2 mg/kg, the linear ranges were 1.0-20.0 mg/L with linear correlation coefficients greater than 0.9992, the recoveries in the spiked samples at 0.2, 0.4 and 2.0 mg/kg were from 80.6 to 105%, and the relative standard deviation reached 2.6-7.7%. This method has the advantages of convenient operation, good resolution, and environmental protection, which can satisfy the requirement of determination for fenpropathrin enantiomer residues in fruit and vegetable puree as supplementary food for infants.

[Simultaneous determination of monochloropropanediol esters and glycidyl esters in vegetable oils by acidic transesterification-gas chromatography-mass spectrometry].

A comprehensive analytical method based on gas chromatography-mass spectrometry (GC-MS) was developed for the determination of 3-monochloropropanediol esters, 2-monochloropropanediol esters, and glycidyl esters in vegetable oils. Different parameters, such as bromination reaction temperature, bromination reaction time, derivatization reagent dosage, and derivative reaction time, were studied. The optimal conditions were as follows: 0.25 g of oil was weighed in a 10-mL glass tube, followed by the addition of 2 mL tetrahydrofuran, 25 µL of internal working standard solutions, and 30 µL of acid aqueous solution of NaBr, homogenized, and the mixture was incubated at 50 ℃ for 15 min. The reaction was stopped by the addition of 3 mL of an aqueous solution of sodium hydrogen carbonate. To separate the oil from the water phase, n-heptane was added, and the upper layer was transferred to an empty test tube and evaporated to dryness under a nitrogen stream. The residue was dissolved in 1 mL of tetrahydrofuran. 1.8 mL of sulfuric acid solution in methanol was added to the sample, and the resulting mixture was incubated at 40 ℃ for 16 h. The reaction was stopped by the addition of 0.5 mL of an aqueous solution of sodium hydrogen carbonate. After purification by n-hexane and derivatization of phenylboric acid, the derivatives were extracted with n-hexane. After nitrogen blowing, the residue was dissolved in 1 mL of n-hexane, and then filtered through a 0.45-µm membrane filter unit prior to GC-MS analysis. Temperature programming was applied at an initial temperature of 80 ℃. After 0.5 min, the temperature was raised to 180 ℃ at a rate of 20 ℃/min, held for 0.5 min, raised to 200 ℃ at a rate of 5 ℃/min for 4 min, and finally raised to 300 ℃ at a rate of 40 ℃/min for 4 min. The target compounds were separated on a DB-5MS column (30 m×0.25 mm×1 µm). Identification and quantification were achieved using an electron impact (EI) ion source in the positive ion mode with the selected ion monitoring mode. The internal standard method was used to quantify the 3-chloropropanediol esters, 2-chloropropanediol esters, and glycidyl esters. Under the optimal conditions, the correlation coefficients of the standard calibration curves were greater than 0.999 in the mass concentration range of 0.01-0.80 mg/L. The limits of detection were 25, 25, and 20 µg/kg (S/N=3), and the limits of quantification were 75, 75, 60 µg/kg (S/N=10). Four samples of different matrix types were selected for scaling experiments. At spiked levels of 250, 500, and 750 µg/kg, the recoveries of 3-chloropropanediol esters, 2-chloropropanediol esters, and glycidyl esters in spiked samples ranged from 89.0% to 98.7%, with relative standard deviations between 2.05% and 7.81% (n=6). This method was used to determine 112 commercially available vegetable oil samples, among which 84 samples were detected with 3-chloropropanediol esters, 2-chloropropanediol esters, or glycidyl esters. The method developed in this study was remarkably different from the standard method, which are mentioned in the national standard method (GB 5009.191-2016) and industry standard method (SN/T 5220-2019), especially in the pretreatment step that involved acidic transesterification. Use of the acidic transesterification method can avoid side reactions, such as the conversion of 3-chloropropanediol, 2-chloropropanediol, and 3-bromopropanediol to free glycidol under alkaline conditions. The method developed in this study was more efficient, and the results were more accurate and reproducible. It has theoretical and practical significance for the control of 3-chloropropanediol esters, 2-chloropropanediol esters, and glycidyl esters residues in vegetable oils, establishment of detection standards, and optimization of the production process.

Hydroxytyrosol and Oleuropein Inhibit Migration and Invasion via Induction of Autophagy in ER-Positive Breast Cancer Cell Lines (MCF7 and T47D).

Hydroxytyrosol (HT) and oleuropein (OL), the most abundant of the phenolic compounds in olives, have anticancer properties against breast cancer (BC). However, little attention has been paid to the mechanism of HT or OL in BC cells. The objective of this study was to identify the underlying molecular mechanisms of these compounds. ER-positive BC MCF7 and T47D cells were treated with HT and OL in combination with hepatocyte growth factor (HGF), rapamycin (Rapa, an agonist of autophagy) or 3-methyladenine (3-MA, an inhibitor of autophagy). Cell viability, metastasis capability and autophagy-related proteins were evaluated by wound healing assays, Transwell assays and Western blot. HT and OL reduced the cell viability of MCF-7 and T47D cells in a dose-dependent manner. Both cells were more sensitive to HT than OL. In addition, Rapa significantly inhibited HGF-induced migration and invasion, indicating that metastases of both BC cells could be inhibited by suppression of autophagy. Moreover, HT and OL significantly blocked HGF- or 3-MA-induced cell migration and invasion by reversing LC3II/LC3I and Beclin-1 downregulation and p62 upregulation. These findings revealed that HT and OL could suppress migration and invasion by activating autophagy in ER-positive BC cells, which might be a promising therapeutic strategy.

New versatile zincic sorbent for tobacco specific nitrosamines and lead ion capture.

New carbon-doped ferric zinc oxide sorbents were fabricated to capture the environment carcinogen tobacco specific nitrosamines (TSNA) efficiently in solution, following new adsorption model of electrostatic attraction instead of traditional geometric constraints. The influence of ferric content on the structure-property of the sorbents was systemically studied with XRD, N2 adsorption-desorption and SEM methods combined with the adsorption of TSNA in different solutions. New sorbent captured 99% of 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) in simulated surface water and 40% of TSNA in the tobacco extract solution, more than activated carbon or zeolites. Ferric ZnO sorbent took about 15 min to reach the adsorption equilibrium in the NNK or Pb(Ⅱ) solution, faster than NaZSM-5 zeolite. Moreover, the adsorbed NNK on ferric ZnO sorbent decomposed at mild conditions for the first time, providing a new way to control environment pollution.

[Determination of eight vitamin E in vegetable oils by gas chromatography-mass spectrometry and its application on authentication of sesame oil].

A method was established for the determination of eight vitamins E (α-, ß-, γ-, δ-tocopherol and α-, ß-, γ-, δ-tocotrienol) in vegetable oils using gas chromatography-mass spectrometry (GC-MS). The targets were extracted with methanol, and analyzed by GC-MS in the selected ion monitoring (SIM) mode after concentration to a constant volume, and quantified using the external standard method. Baseline separation were achieved for all the target compounds. The linearities of all the compounds were between 0.01 and 1 mg/L. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.03-0.25 mg/kg and 0.10-0.83 mg/kg, respectively. The average recoveries of all the targets in sesame oil samples were between 87.5% and 107.4% at three spiked levels (10, 50, and 250 mg/kg), and the RSDs were all less than 7.5%. The tocopherols and tocotrienols contents in sesame oil samples and in six lower-price vegetable oils (soybean, rapeseed, sunflower, peanut, corn and palm oils) were determined by the above mentioned method. The results showed that the vitamin E profiles of sesame oil were significantly different from those of the other six vegetable oils. Therefore, vitamin E can be used as a discriminating parameter for detecting the adulteration of sesame.

Hydroxytyrosol and Oleuropein Inhibit Migration and Invasion of MDA-MB-231 Triple-Negative Breast Cancer Cell via Induction of Autophagy.

BACKGROUND: Breast Cancer (BC) is the leading cause of cancer-related deaths among women. As such, novel chemotherapeutic agents are urgently needed, especially for Triple-Negative Breast Cancer (TNBC). Hydroxytyrosol (HT) and Oleuropein (OL) are rich in olive oil, which is associated with a low occurrence of BC. However, the effects and mechanisms of action of HT and OL in BC cells are still unclear. This study aimed to explore the molecular mechanisms underlying the antitumor effect of HT and OL in TNBC. METHODS: TNBC MDA-MB-231 cells were treated with HT and OL in combination with Hepatocyte Growth Factor (HGF), rapamycin (Rapa, an inducer of autophagy) or 3-methyladenine (3-MA, an inhibitor of autophagy). Cell viability, migration, invasion, and autophagy signaling were analyzed by scratch assays, transwell migration assays, and Western blot analysis. RESULTS: Treatment with HT or OL reduced MDA-MB-231 cell viability in a dose-dependent manner. MDAMB- 231 cells were more sensitive to HT treatment than OL treatment. Rapa treatment could significantly block HGF-induced MDA-MB-231 cell migration and invasion, suggesting that inhibition of autophagy could promote migration and invasion. Moreover, HT or OL treatment significantly suppressed HGF or 3-MA induced cell migration and invasion by reversing LC3-II/LC3-I and Beclin-1 downregulation and reversing p62 upregulation. CONCLUSION: These data indicated that HT and OL may inhibit migration and invasion of TNBC cells by activating autophagy. These findings provide potential therapeutic strategies that target autophagy to limit the pathogenesis and progression of BC.

[Determination of organo-tin residues in edible vegetable oil by positive chemical ionization-gas chromatography-mass spectrometry].

For the determination of organo-tin residues in edible vegetable oil, a method was developed based on gas chromatography-mass spectrometric (GC-MS) with positive chemical ionization (PCI). The edible oil samples were first dissolved by cyclohexane-ethyl acetate (1:1, v/v), and then purified by gel permeation chromatography (GPC). After derivatization by sodium tetraethylborate, the samples were analyzed by GC-MS with PCI source in the single ion monitor (SIM) mode. The seven organo-tin compounds showed good linear relationships in the range of 20-2000 µg/L and the correlation coefficients exceeded 0.99. The limits of quantitation (LOQs) and the average recoveries of the seven organo-tin compounds were 0.3-1.2 µg/kg and 66.2%-103.2%, respectively, and the relative standard deviations were less than 11.5% at three spike levels (0.05, 0.10, and 0.20 mg/kg). The method showed good linearity and high sensitivity and can be used for the determination of organo-tin residues in edible vegetable oil.

[Determination of five acylpyrazole pesticide residues in edible vegetable oils using gas chromatography-negative chemical ionization-mass spectrometry].

A method was established for the determination of five acylpyrazole pesticide residues in edible vegetable oils using gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The pesticides were extracted from a sample with acetonitrile under freezing conditions. A simple cleanup step known as QuEChERS was then conducted. After being identified by GC-NCI-MS, the extracts were quantified using an external standard method that employs a matrix correction standard curve. The linearity of the method was good between 20 and 1000 µg/L, and all limits of quantification were less than 2 µg/kg. Recoveries of all pesticides were in the range of 82.7%-112.4% at the three spiked levels of 0.01, 0.02, and 0.05 mg/kg, and all relative standard deviations were not more than 12.3%. Therefore, this method can be used to determine the residues of acylpyrazole pesticides in edible vegetable oils.

[Determination of 10 perfluorinated carboxylic acid compounds in water by gas chromatography-mass spectrometry coupled with negative chemical ionization].

A method was developed for the simultaneous determination of 10 perfluorinated carboxylic acid compounds in water by gas chromatography-mass spectrometry coupled with negative chemical ionization (GC-NCI-MS). Perfluorinated carboxylic acid compounds were derivatized by trifluoro-N-methyl-N-(trimethylsilyl) acetamide (MSTFA) as the trimethylsilyl derivatization reagent. The water sample was purified and enriched through a weak anion exchange solid phase extraction column and analyzed via GC-NCI-MS. The sample pretreatment, derivation and instrument conditions were optimized. The results showed that the linearity of the 10 perfluorinated carboxylic acid compounds was good in the range of 0.1-10 mg/L with correlation coefficients of 0.9956-0.9993. The limits of detection (LODs) and limits of quantification (LOQs) were 0.5-1.5 µg/L and 1.5-4.5 µg/L, respectively. The spiked recoveries of the blank samples ranged from 70.2% to 112.6% with the relative standard deviations (RSDs) between 2.1% and 14.5% (n=6). The method is simple, sensitive, accurate and precise, and can be used to detect the 10 perfluorinated carboxylic acid compounds in water.

[Determination of three organotin pesticide residues in apples and cabbages by gas chromatography-electron impact/positive chemical ionization mass spectrometry].

A method for the simultaneous determination of fenbutatin oxide, triphenyltin and cyhexatin in apples and cabbages was developed by gas chromatography-mass spectrometry coupled with two different ionization techniques, electron impact (EI) ionization and positive chemical ionization (PCI). At first, the samples were digested by hydrobromic acid, and extracted by acetone-hexane (1:2, v/v). The extracts were derivatized by sodium tetraethylborate as the derivatization reagent, and cleaned up by the Florisil SPE columns. Finally, the samples were analyzed by GC-EI/MS and GC-PCI/MS in selected ion monitoring (SIM) mode. The results showed that good linearities were obtained with correlation coefficients (r2) greater than 0.997 for fenbutatin oxide in the range of 75-500 µg/L in both foods, triphenyltin in the range of 50-1000 µg/L in cabbages and 50-500 µg/L in apples and cyhexatin in the range of 50-1000 µg/L in the two foods. The accuracy was checked at three spiked levels (50, 100 and 200 µg/kg) in cabbages and apples. The limits of detection (LODs, S/N=3) were 0.01-0.05 mg/kg (EI) and 0.01-0.02 mg/kg (PCI), and the limits of quantifications (LOQs, S/N=10) were 0.03-0.16 mg/kg (EI) and 0.02-0.06 mg/kg (PCI). The average recoveries ranged from 59.24%-97.36% (apples) and 50.54%-94.54% (cabbages) in the mode of EI, and the corresponding values were 65.38%-95.86% and 62.56%-90.44% in the mode of PCI. The relative standard deviations (RSDs) were all less than 6.9% (n=6). The PCI method can be used to improve the accuracy in comparing with the EI, in terms of good selectivity and high sensitivity.

[Determination of fipronil and its metabolites in eggs and egg products with gas chromatography-negative chemical ionization-mass spectrometry].

A method was established for the determination of fipronil and its metabolites in eggs and egg products with gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS). The targets were extracted from samples with acetonitrile, and followed by a simple cleanup step known as dispersive solid-phase extraction QuEChERS. The extracts were determined by GC-NCI-MS, and quantified by external standard method with matrix correction standard curves. The recoveries were in the range of 87.0% to 99.3% at four spiked levels (0.1, 2.0, 4.0 and 20.0 µg/kg), and all RSDs were not more than 12.7% for the four analytes. The linearity of the method was good between 0.005 and 0.10 mg/L, and all LOQs were less than 0.10 µg/kg. So this method can be used to determine the residues of fipronil and its metabolites in eggs and egg products.

[Determination of four insecticide residues in honey and royal jelly by gas chromatography-negative chemical ionization mass spectrometry].

A method was developed for the determination of four insecticide residues in honey and royal jelly by gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The honey and royal jelly samples were treated with different preparation methods as the result of the different components. The honey sample was extracted with ethyl acetate and cleaned up with primary second amine, and the royal jelly sample was extracted with acetonitrile-water (1:1, v/v), and cleaned up with a C18 solid-phase extraction column. Finally, the extracts of the honey and royal jelly were analyzed by GC-NCI/MS in selected ion monitoring (SIM) mode separately. External standard calibration method was used for quantification. The linearities of calibration curves of the four insecticides were good with the correlation coefficients greater than 0.99 in the range of 50-500 microg/L. The limits of the detection (LODs) of the four insecticides were in the range of 0.12- 5.0 microg/kg, and the limits of the quantification (LOQs) were in the range of 0.40-16.5 microg/kg. The recoveries of the four insecticides spiked in honey and royal jelly at three spiked levels (10, 15 and 20 microg/kg) were in the range of 78.2 -110.0%, and the relative standard deviations (RSDs) were all below 14%. The sensitivity and selectivity of this method were good with no interfering peaks. The proposed method is simple quick and effective to analyze the four insecticide residues in honey and royal jelly.

[Determination of trifluralin residue in aquatic products and edible oils by gas chromatography-negative chemical ionization mass spectrometry].

A confirmatory method was established for the determination of trifluralin residue in aquatic products and edible oils with the technique of offline disperse solid phase extraction and gas chromatography-negative chemical ionization mass spectrometry (DSPE-GC-MS/NCI). Trifluralin was extracted from aquatic products and edible oils with acetonitrile, and liquid-liquid partitioning formed by adding anhydrous magnesium sulfate followed by a simple cleanup step known as dispersive solid-phase extraction. The aliquot was analyzed by GC-MS/NCI using isotope internal standard method. The method was reliable and stable. The recoveries of trifluralin were in the range from 80% to 100% at three spiked levels of 1.0, 2.0, and 3.0 microg/kg, and the RSDs were not more than 10.3%. The linearity of method was good from 1 to 40 microg/L, and the LOD was 0.02 microg/kg. This method can be used as a conclusive evidence method for the determination of trifluralin residue in aquatic products and edible oils.

[Determination of 17 pyrethroid pesticide residues in vegetables by gas chromatography-mass spectrometry with negative chemical ionization].

A method was established for the determination of 17 pyrethroid pesticide residues in vegetables using QuEChERS (quick, easy, cheap, effective, rugged and safe) clean-up method and gas chromatography-mass spectrometry (GC-MS) with negative chemical ionization (NCI). The pyrethroid pesticides in the sample were extracted with acetonitrile. After QuEChERS clean-up with a mixture of primary secondary amine and graphitized carbon black packings, the extract was analyzed by GC-NCI-MS in selected ion monitoring (SIM) mode. An isotope internal standard of cypermethrin was employed to the quantification. The limits of quantification ranged from 0.02 to 5 microg/kg. The recoveries of the pyrethroid pesticides spiked in three different matrixes (peas, broccoli and Chinese onion green) at four spiked levels of 10, 20, 30 and 100 microg/kg were from 71.0% to 139.0%, and the relative standard deviations were less than 12.8%. This method can be used as a conclusive evidence method of the 17 pyrethroid pesticide residues in vegetables.