QuEChERS结合GC-MS/MS法快速测定小麦中20种农药残留量（网络首发、推荐阅读）

建立QuEChERS结合气相色谱-串联质谱法（GC-MS /MS）检测小麦中20种农药残留量的方法。在实验过程中对不同含量净化吸附剂对小麦样品提取液的净化效果进行了研究,并且考察了小麦中20种农药的基质效应。结果表明：（1）与GB 23200.113—2018中7.1.2前处理方法相比,通过对净化吸附剂的优化,节约了无水MgSO4、PSA、C18的用量,将无水MgSO4添加量从1 200 mg减少到了400 mg,将PSA的添加量从400 mg减少到了100 mg,将C18的添加量从400 mg减少到了200 mg,另外加入了100 mg GCB可以有效去除小麦提取液中的色素。（2）小麦中20种农药在GC-MS/MS上色谱峰响应值与其质量浓度（5~500 ng/mL）之间线性关系良好,相关系数超过0.99,检出限范围是0.01~0.16 μg/kg,定量限范围是0.04~0.52 μg/kg;另外20种农药的基质效应强度差异较大;（3）在添加水平为80、200、400 μg/kg时20种农药平均回收率分别在75.24%~98.29 %、82.01%~105.71%、94.91%~ 106.14%范围内,RSD分别为0.57%~3.13%、0.67%~3.98%、1.26%~3.08 %,符合农药残留分析要求。     

基于QuEChERS-GC-MS/MS法同时测定豇豆中15种有机磷农药残留

建立了三重四极杆气质联用仪（GC-MS/MS）结合改良的QuEChERS方法同时检测豇豆中15种有机磷农药多残留的分析方法。样品前处理采用QuEChERS方法，用乙腈-乙酸乙酯（1∶1,v/v）作为样品农药残留提取溶剂，经C组净化管（100 mg PSA+200 mg C18+40mg GCB+300 mg无水MgSO4）固相分散净化，浓缩定容后用GC-MS/MS在多反应监测（MRM）下分析检测，外标法定量。其结果显示，在所测线性浓度为0.025～0.4μg/mL范围内，各农药的线性关系良好，线性回归方程的相关系数（R）均大于0.998，方法检出限为0.0012～0.3648μg/kg，分别向阴性豇豆样品中添加15种农药标准品浓度为0.2、0.6和0.8 mg/kg的3个水平，其加标平均回收率为77.45%～103.2%，相对标准偏差RSD%(n=6)为0.21%～9.87%。该方法具有净化效果好、重复性强、灵敏度高等优势，可为豇豆质量安全监控提供有效技术支持。     

QuEChERS-LC-MS/MS联用技术对浆果中多种农药残留的测定

为建立检测浆果中多种农残的方法,运用QuEChERS前处理技术,结合高效液相色谱与串联质谱联用（HPLC-MS/MS）技术同时测定浆果中10种农药残留。结果显示,最优分散剂组合为10 g样品中加入PSA 50 mg,GCB 2.5 mg和C18 50 mg进行基质的净化,此条件下平均回收率达到75.38%。10种农药对照品在1～100 μg/L范围内,呈现良好的线性关系,测定蓝莓中10种农药残留的加标回收率为95.31%～111.26%,相对标准偏差为0.90%～4.16%,测定葡萄中10种农药残留的加标回收率为90.37%～116.20%,相对标准偏差为0.80%～5.09%。该方法简便、快速、准确,适用于常见浆果中农药残留的分析。     

QuEChERS/气相色谱三重四级杆质谱法测定枸杞籽油中多环芳烃类物质

建立了同时检测保健食品枸杞籽油中16种多环芳烃(PAHs)的QuEChERS/气相色谱三重四级杆质谱(GC-MS/MS)方法。样品(0. 5 g)经3 mL乙腈提取2次,采用含200 mg PSA和100 mg C18吸附填料粉进行净化,净化后采用GC-MS/MS进行分析测定。结果表明:在优化条件下,16种PAHs分离度良好,在1. 0～200 ng/mL范围内线性关系良好;回收率为60. 04%～119. 00%,RSD在2. 92%～13. 03%之间;检出限在0. 2～3. 5μg/kg之间,定量限在0. 7～11. 5μg/kg之间。该方法数据可靠、简便快速、灵敏度高,适合保健食品枸杞籽油中多环芳烃的测定。     

QuEChERS-三重四极杆液相色谱质谱联用法快速筛查花生中52种农药残留

目的 基于QuEChERS 前处理方法,建立了HPLC-MS/MS快速筛查花生中52种农药残留的筛选和确认。方法 样品经0.1%甲酸乙腈提取,提取液经MgSO4、PSA和C18净化后,采用Waters C18(100 mm×2.1 mm×1.7 μm)色谱柱分离,在三重四级杆正离子反应监测（MRM）测定,基质标准曲线结合外标法定量。结果52种农药在0.001μg/mL~0.1μg/mL范围内线性良好,相关系数均大于0.998,方法的定量限（LOQ）1.0~5.0μg/Kg,通过实际样品加标回收试验,52种农药在10μg/Kg的加标回收率为76.6%~107.6%,相对标准偏差（RSD）为3.5%~12.3%,结论 该方法适用于花生中农药残留的筛查检测及定量分析。     

水果中26种有机氯及拟除虫菊酯农药残留GC-ECD测定

利用气相色谱(GC)建立了水果中26种有机氯农药同时测定的方法。试样中农药残留在超声波振荡条件下用乙腈提取,经PSA、C18净化,GC-电子捕获检测器(ECD)检测。方法的检出限为0.001～0.005mg/kg,回收率为84.5%～104.5%,相对标准偏差为1.1%～6.7%。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求。     

基于QuEChERS-GC-MS/MS法同时测定猕猴桃中15种有机磷农药残留

建立改良的QuEChERS方法结合气相色谱-三重四极杆串联质谱（GC-MS/MS）法同时检测猕猴桃中15种有机磷农药残留的分析方法。样品前处理采用改进的QuEChERS方法,乙腈-乙酸乙酯（1∶1,V/V）作为提取溶剂,经100 mg乙二胺-N-丙基硅烷（PSA）、200 mg十八烷基硅烷键合硅胶（C18）、40 mg石墨化碳黑（GCB）、300 mg无水硫酸镁固相分散净化,用GC-MS/MS法在多反应监测（MRM）模式下分析检测,内标法定量。结果表明,15种有机磷农药在质量浓度0.05～1.00 μg/mL范围内线性关系良好,相关系数R2均＞0.998,方法检出限为0.001 2～0.326 5 μg/kg,定量限为0.004～1.088 μg/kg;其平均加标回收率为76.95%～101.2%,精密度试验结果的相对标准偏差（RSD）（n=6）为0.21%～10.05%。该方法具有净化效果好、重复性强、灵敏度高等优势,适用于猕猴桃样品中多种农药残留的同时检测。     

QuEChERS-HPLC-MS/MS测定蔬菜中29种农药残留

建立了QuEChERS-高效液相色谱-串联质谱（HPLC-MS/MS）同时快速测定蔬菜中29种农药残留的分析方法。样品以乙腈提取,氯化钠盐析,以十八烷基硅烷键合硅胶（C18）和N-丙基乙二胺（PSA）净化,以Waters XBridge C18色谱柱分离,电喷雾正离子扫描,多反应监测（MRM）模式检测,基质匹配标准溶液外标法定量。在此优化条件下,29种农药分子在不同加标水平下的平均回收率为64.62%～123.55%,相对标准偏差（RSD）为0.7%～14.3%,方法定量限（LOQ）为0.40～8.00 μg/kg。该方法简便快速、灵敏度高、重现性好,能满足蔬菜中农药残留的快速检测要求。     

分散固相萃取-气相色谱-串联质谱法测定茉莉花茶中86种农药残留

以QuEChERS（Quick,Easy,Cheap,Effective,Rugged,Safe）法为前处理技术,优化净化吸附剂组合和用量,改进净化方式,并以气相色谱-串联质谱（gas chromatography-tandem mass spectrometry,GC-MS/MS）法为检测手段,建立茉莉花茶中86 种农药残留筛查检测方法。样品用乙腈提取,提取液经饱和的氯化钠溶液萃取,取有机相,转移至装有混合吸附剂和有机滤膜的针筒中完成净化与过滤,GC-MS/MS测定,外标法定量。86 种农药线性范围在5～400 μg/kg之间线性关系良好,相关系数（r2）在0.98以上,方法定量限为0.1～8.0 μg/kg。当添加水平为80 μg/kg时,91.8%的农药平均加标回收率在70.1%～116.0%之间,相对标准偏差为1.9%～11.4%。     

烟草中有机磷农药残留的GC/MS快速分析

为快速检测烟草中多有机磷农药残留,建立了乙腈提取,PSA吸附剂净化,气相色谱/质谱联用法测定烟草中有机磷农药残留量的方法。结果表明,20种有机磷农药的回收率为70%～118%,相对标准偏差0.5%～11.9%。该方法适合批量烟草样品中多有机磷农药残留的快速检测。     

Effect of temperature on the cell wall composition of raisins during storage under a modified atmosphere

 Raisins obtained from seedless grapes ("Flame" variety) were kept under a modified atmosphere (MA) composed of CO₂ (60%) and N₂ (40%), and stored at 10  °C (10MA), 20  °C (20MA), 30  °C (30MA) and 40  °C (40MA). An additional sample was stored under air at 20  °C (20A). Colour, and changes in cell wall components were monitored during storage. At the end of the storage period, the 40MA and 20A samples showed a significant decrease (∼18–19%) in the yield of cell wall material (CWM), whereas less than 6% of CWM had been degraded in the 10MA sample. The decrease in CWM was mainly due to pectic polysaccharide degradation, although for 20A and 40MA samples, hemicelluloses were also affected. Throughout storage, 10MA, 20MA and 30MA samples exhibited similar CWM solubility; however, that of the 40MA sample underwent a significant decrease, from 10% to 4.5%, probably due to the formation of new pectic chains of higher molecular weight. In contrast, the CWM solubility of sample 20A increased from 10% to 15%, suggesting that MA may have promoted the inhibition of pectic-polysaccharide-degrading enzymes. In general, the combined use of relatively low temperatures and a MA helped to preserve both the colour of raisins and maintain the levels of their CWMs at values similar to initial concentrations. Received: 5 October 1998     

PRODUCTION AND BINDING OF MALONALDEHYDE DURING STORAGE OF COOKED PORK

Cooked pork samples were stored at 3°C and analyzed for malonaldehyde (MA). MA increased to a maximum and remained there, typical behavior for a food but contrasting with pure lipid oxidation in which MA increases and then decreases as volatile MA is lost. The failure to lose MA in food products may be attributed to MA binding. Water extracts of cooked pork samples (representing approximately l /3 of the total MA) were fractionated on G-10 Sephadex and analyzed for MA. With increasing storage time, a definite change in elution pattern from free MA to bound MA took place; the binding was not to protein or amino acids.     

Effects of in-package atmospheric dielectric barrier discharge cold plasma treatment on the antimicrobial efficacy of whey protein isolate-based edible films that incorporate malic acid against Salmonella in chicken breast processed meat

Effects of in-package atmospheric dielectric barrier discharge cold plasma (CP) treatment on the antimicrobial efficacy of malic acid-incorporated whey protein isolate (MA–WPI) coating and MA diffusion in MA–WPI-coated skinless chicken breast processed meat (CBPM) were evaluated. MA–WPI coating followed by CP treatment (MA–WPI + CP) inactivated Salmonella (5.6 log CFU/g) in CBPM by 1.8 log CFU/g. CP treatment increased Salmonella reduction rates in MA–WPI-coated samples during storage at 4 and 10 °C and the diffusion coefficients of MA in the coating, which was confirmed by comparing results of MA–WPI + CP-treated and MA–WPI-coated samples. CP treatment facilitates MA diffusion in the coating, thereby increasing the Salmonella inhibition efficacy of the coating. MA–WPI + CP treatment did not influence the color and lipid oxidation of CBPM during storage at 4 °C and the water vapor permeability, elongation, and elastic modulus of MA–WPI films.Industrial relevanceThrough the technological development of in-package cold plasma treatment for decontamination of food in the industrial production line, the microbiological safety of ready-to-eat foods coated with antimicrobials can be effectively increased by exposing the coated foods to cold plasma to accelerate the diffusion of the antimicrobials in the coating to the site of microbial contamination at the surface. The effect of cold plasma treatment on the antimicrobial efficacy of the antimicrobial coating is useful, especially during the initial stages when the coating is expected to exhibit highly efficacious antimicrobial function.     

Measurement of malonaldehyde in apple juice using GC–MS and a comparison to the thiobarbituric acid assay

Malonaldehyde (MA) in gamma-irradiated apple juice was measured using a GC–MS method and in comparison to the thiobarbituric acid (TBA) assay. The profiles of MA content as a function of radiation dose were similar using both methods, however, MA content was higher when measured with the TBA assay compared to the GC–MS method. The overestimation of MA using the TBA assay increased as the amount of MA decreased. Use of the GC–MS method demonstrated MA content in irradiated juice declined rapidly during storage at 5 °C. MA content appeared to decrease much less when the TBA assay was used. The GC–MS method also allowed measurement of formaldehyde and acetaldehyde in addition to MA.     

Correlation between methyl anthranilate level and percentage of pollen in Spanish citrus honey

The common level of methyl anthranilate (MA) in Spanish citrus honey and the correlation between this compound and the percentage of citrus pollen (sometimes underrepresented) are evaluated. The MA analysis methodology was validated before analysing the honeys (harvested in 2011 and 2012), which were characterised by pollen, MA, hydroxymethylfurfural, electrical conductivity, moisture and colour. Pollen ranged 1–88% and MA 0.5–5.9 mg kg^?1, and there was no quantitative correlation between both. However, significant correlations with moderate Pearson coefficients were observed: MA/electrical conductivity (?0.678); MA/colour (?0.559); pollen/electrical conductivity (?0.553); and pollen/colour (?0.556). 89.2% of samples from 2011 and 95.4% from 2012 had the required level of citrus pollen (at least 10%), although only 53.5% and 61.4%, respectively, had the commercially required level of MA (2 mg kg^?1). Only about half of the samples satisfied both parameters. The MA value should be recommended only when the honey has an unexpectedly low percentage of citrus pollen, and after assessing organoleptic and physicochemical parameters.     

Modified Atmosphere Storage of Rockfish Flllets

A modified atmosphere (MA) of 80% CO₂ and 20% air was effective in extending shelf life of fresh rockfish fillets. Aerobic plate counts and trimethylamine levels were significantly lower (P < 0.1%) for the fillets held in MA compared to those held in air. A decline in surface pH was observed on fillets stored in MA, presumably due to the absorption of CO₂ and its hydration to carbonic acid. Oxidation-reduction potentials suggested a more aerobic environment on fillets stored in MA. There were no significant differences in weight loss between control and MA samples. Sensory evaluations indicated that fillets held under MA were of good quality for at least 13 days of storage.     

The response of unripe Conference pears to modified atmosphere retail packaging

Unripe green Conference pears with initial firmness values of 46–55 N were sealed in modified atmosphere (MA) low density polyethylene (LDPE, 30μ) pillow packs and in perforated control packs on three dates during 1985–1986. Changes in pack atmosphere composition, skin chlorophyll content, flesh firmness and sensory quality were monitored during 14–20 days simulated shelf-life at 20°C. In MA packs, equilibrated atmospheres containing 5–9% CO₂ and < 5% O₂ developed within c. 3 days. Chlorophyll degradation was completely inhibited by MA and resumed when packs were perforated, but MA only partially retarded the rate of flesh softening. Variations in the rate of ripening changes in duplicate MA packs could not be explained simply by differences in pack atmospheres. Furthermore, pears retarded by MA packaging failed to develop the normal sweet, aromatic flavour and succulent, juicy texture of 'eating-ripe' fruit, even when the packs were perforated after 4 days.
The differences in the responses of pears and apples to MA packaging, and the limitations of using this technique for the commercial marketing of English pears are discussed.     

Large-scale isolation of highly pure malaxinic acid from immature pear (Pyrus pyrifolia Nakai) fruit

Malaxinic acid [4-(O-β-d-glucopyranosyl)-3-(3′-methyl-2′-butenyl)benzoic acid; MA] is one of the main compounds contained in pear fruit. The antifungal, antibacterial, and anticancer effects of MA have been reported. However, additional evaluations on the biological activity of MA have not been fully performed due to the lack of an MA standard. Therefore, in the present study, we established a large-scale isolation method to obtain highly pure MA from immature pear (Pyrus pyrifolia Nakai) fruit. The EtOAc-soluble acidic fraction (134.75 g) of pear fruit (18 kg fresh wt.) 60% EtOH extract (1,081.9 g) was purified by Amberlite XAD-2 (H₂O/EtOH, stepwise), Diaion HP-20 (H₂O/MeOH, stepwise), and Sephadex LH-20 (80% MeOH) column chromatographies. Then, the fractions containing MA were finally purified by high performance liquid chromatography using an Amide RP-C16 column on semi-preparative scale. The isolated MA (793 mg) was >99% pure, and total recovery was estimated to be 61.7%.     

Formation of Malonaldehyde, Formaldehyde, and Acetaldehyde in Apple Juice Induced by Ionizing Radiation

ABSTRACT: We investigated the effects of ionizing radiation on the formation of malonaldehyde (MA), formaldehyde (FA), and acetaldehyde (ACT) in apple juice. The formation of MA, FA, and ACT in both pasteurized and fresh juice increased with radiation dose. The G values (number of species formed per 100 eV absorbed) for MA, FA, and ACT in pasteurized juice were 0.0056, 0.061, and 0.044, respectively. MA concentration decreased rapidly during storage at 5°C, while ACT and FA did not. Irradiation-induced formation of MA, FA, and ACT decreased with decreasing irradiation temperature. Exclusion of oxygen during irradiation reduced formation of ACT and FA, but not MA. Adding 1000 ppm of ascorbate, sorbate, or sulfite to juice before irradiation also decreased MA formation.     

植物乳杆菌MA2的生物学特性研究

对Kefir源植物乳杆菌MA2的生物学特性进行了研究,结果显示,MA2菌株在MRS培养基初始pH为6.60,接种量为4%,37℃厌氧条件下培养18 h,活菌数可达到1.2×109cfu/mL。乙酸和乳酸为发酵液中的优势有机酸,且厌氧条件下发酵液中的有机酸的含量较高,厌氧发酵液中检测出的6种脂肪酸中C18∶1的含量最高。降胆固醇试验证明,低聚葡萄糖(GOS)可以促进MA2的胆固醇移除能力,移除率可达到70%;菌体细胞脂肪酸的测定结果显示MA2菌株降胆固醇的机理主要是吸附、吸收同化机理。MA2菌株的牛乳发酵试验结果显示其具有良好的产黏特性,在乳清培养基中胞外多糖产量可达380 mg/L。结合其良好的耐酸、耐胆盐特性,植物乳杆菌MA2具有良好的益生菌应用潜力。