1-(4-偶氮苯基苯)-3-丙基-三氮烯键合硅胶修饰碳糊电极溶出伏安法测定饲料中镉的研究

以1 - (4 - 偶氮苯基苯) - 3 - 丙基 - 三氮烯键合硅胶(ABPT - SG)为修饰剂,液体石蜡为粘合剂,制备了ABPT - SG修饰碳糊电极.在pH8.0、浓度为0.2 mol/L的氨性缓冲底液中,于-1.2 V(Vs.SCE,下同)的电位下富集,将Cd2+以Cd - ABPT - SG络合物的形式吸附在电极上,用阳极溶出伏安法测定.在-0.60 V处Cd有一灵敏的阳极溶出峰,峰电流与Cd2+的浓度在5.0×10-6～1.0×10-3 mol/L范围内呈良好的线性关系,测定饲料中的镉,检出限为1.0×10-8 mol/L.     

Zn(Ⅱ)-PYPAPT-Triton X-100光度法测定食品中微量锌

研究了1-吡啶-3-[4-(苯基偶氮)苯基]-三氮烯(PYPAPT)与锌离子(Zn2 )的光度法测定微量锌。在非离子表面活性剂TritonX-100存在下和NaOH介质中,Zn2 与PYPAPT形成1∶2红色配合物。配合物最大吸收波长位于520nm,表观摩尔吸光系数ε520为1.54×105L·mol-1·cm-1,Zn2 含量在0～0.32mg/L范围内符合比尔定律。研究测定微量锌的新光度法灵敏度高,操作简便,应用于食品中微量锌的测定,结果满意。测定结果与国标(GB)双硫腙方法测定的结果吻合。     

四-(对甲基苯基)-卟啉柱前衍生,高效液相色谱法测定食品中痕量铅、镉、汞

研究了用四-(对甲基苯基)-卟啉柱前衍生,高效液相色谱法测定食品中痕量铅、镉、汞的方法。食品样品用湿法消化后,消化液中的铅、镉、汞用四-(对甲基苯基)-卟啉(T4MPP)柱前衍生,然后用甲醇(内含0.01mol/L四氢吡咯-醋酸缓冲盐)和四氢呋喃(内含0.01mol/L四氢吡咯-醋酸缓冲盐)为流动相梯度洗脱,WatersXterraTMRP18(3.9150mm,5μm)色谱柱为固定相分离铅、镉、汞的T4MPP络合物,用二极管矩阵检测器检测,铅、镉、汞含量在0.01～3mg/L范围内与峰面积成线性关系,根据信噪比(S/N=3),方法检测限为:铅2.3μg/L、镉1.8μg/L和汞2.5μg/L,方法相对标准偏差为2.1%～3.5%,标准回收率为93%～106%,该方法用于测定食品中的铅、镉、汞,结果令人满意。     

高效液相-紫外法检测三孢布拉霉菌发酵液中2-氨基-6-甲基吡啶

建立高效液相色谱-紫外法对三孢布拉霉菌发酵液中2-氨基-6-甲基吡啶含量检测的方法。采用AlltimaC18(250mm×4.6mmi.d.,5μm)色谱柱,以甲醇:水:1%乙酸=85:10:5(v/v/v)为流动相,流速为1.0mL/min时,2-氨基-6-甲基吡啶及其他杂质得到良好分离,紫外光谱231nm检测。在该色谱条件下,2-氨基-6-甲基吡啶浓度5～500mg/L时,其峰面积与相应的浓度线性关系良好(R2=0.9994),回收率99.76%～101.4%,精密度RSD<2.17%。该方法简便、快速、准确可靠,为三孢布拉霉菌发酵液中2-氨基-6-甲基吡啶的检测和含量控制提供了可靠的分析方法。     

Candida etchellsii产2(5)-乙基-4-羟基-5(2)-甲基-3(2H)-呋喃酮的影响因素

在埃切假丝酵母(Candida etchellsii)发酵过程中,通过盐度调控和氨基酸添加,强化目标产物HEMF(2(5)-乙基-4-羟基-5(2)-甲基-3(2H)-呋喃酮)的合成效率。分阶段调控发酵体系的盐度(初始阶段控制CaCl浓度为200 g/L,发酵40 h后提升至220 g/L),结合氨基酸添加(向发酵体系中添加丙氨酸、精氨酸和甘氨酸各1.67 g/L)。摇瓶结果表明:酵母C.etchellsii合成HEMF,其产量为110.74 mg/L。7 L发酵罐上罐验证,HEMF产量达到121.51 mg/L,相比空白(200 g/L CaCl浓度下且没有添加氨基酸)提高了21.2倍。分阶段盐度调控结合氨基酸添加策略显著强化了C.etchellsii对HEMF的合成。     

电化学免疫传感器法快速测定粮油食品中的苯并(a)芘

采用2.0 G聚酰胺-胺(PAMAM)、石墨烯(GS)和1-丁基-3-甲基咪唑基四氟硼酸盐复合膜修饰玻碳电极(PAMAM/GS/IL/GCE),包埋固定多环芳烃抗体,构建了一种纳米免疫传感器,用于快速测定粮油食品中的苯并(a)芘(Ba P)。在p H为7.0含1mmol/L K3[Fe(CN)6]和0.1 mmol/L KCl的磷酸盐缓冲溶液中,基于多环芳烃抗体与抗原之间的特异性免疫反应,以K3[Fe(CN)6]为探针,利用循环伏安法和差分脉冲伏安法研究其免疫反应对传感器响应电流的影响。在优化实验条件下,免疫传感器的峰电流随溶液中Ba P浓度的增大而减小,且峰电流与Ba P浓度在0.1~100 ng/m L范围内呈线性关系,其检测限为0.03 ng/m L(S/N=3)。该免疫传感器的稳定性和重现性较好,利用该法对玉米油和菜籽油等样品中的苯并(a)芘进行检测,回收率在94.46%~103.36%,检测结果与HPLC法基本一致,用于粮油食品中苯并(a)芘的快速检测是可行的。     

1,4-二氢-2,6-二甲基-4-(2-硝基苯基)-3,5-吡啶二甲酸甲异丁酯的合成

1,4-二氢-2,6-二甲基-4-(2-硝基苯基)-3,5-吡啶二甲酸甲异丁酯为一抗高血压新药,作者报道了其三步法的合成方法,并对Hanstzch合成法中制备邻硝基苯亚甲基乙酰乙酸异丁酯的方法进行了改进,反应时间缩短,得率提高至58%.对产物分子结构采用元素分析、红外光谱(IR)、核磁共振氢谱(1H-NMR)及碳谱(13C-NMR)进行了鉴定.     

双波长分光光度法测定食盐中硒含量

在聚乙烯醇(PVA)存在下,在pH10.4的NaHCO3-NaOH缓冲溶液中,硒(IV)与1-(2-吡啶偶氮)-2-萘酚(PAN)、溴化十六烷基吡啶(CPB)反应形成稳定的络合物,该络合物在410 nm处有正吸收峰,529 nm处有负吸收峰,据此建立了双波长光度法测定痕量硒(IV)的新方法。硒(IV)浓度在0~0.12μg/mL内符合比尔定律,方法检出限为1.82μg/L,表观摩尔吸光系数ε为3.38×105L.mol-1.cm-1。方法用于硒强化营养盐和健康平衡盐中硒含量的测定,结果与荧光法测定值一致,相对标准偏差为0.82%~1.16%(n=5),加标回收率为99.7%~101.0%。     

微生物发酵法生产去氢表雄酮检测方法的建立

建立了一个微生物发酵生产去氢表雄酮(DHEA)的检测方法,采用气相色谱法同时测定发酵液中雄甾-4-烯-3,17-二酮(4-AD)、去氢表雄酮甲氧基甲基醚和DHEA含量。发酵液经乙酸乙酯萃取,可直接进样分析。气相色谱条件为:FID检测器,DB-1型(30 m×0.53 mm×0.25 m)毛细管柱;柱温280℃,进样口280℃,检测器310℃;载气为高纯N2,流速1 m L/min。在实验室条件下,发酵液中各主要成分分离情况良好。结果表明:4-AD、去氢表雄酮甲氧基甲基醚和DHEA的浓度线性范围分别为:4-AD为0.2~1.0 g/L(R2=0.996);去氢表雄酮甲氧基甲基醚为0.1~0.9 g/L(R2=0.992);DHEA为0.2~1.0 g/L(R2=0.998),平均回收率依次为(97.88±0.74)%,(99.39±1.07)%和(98.91±1.09)%。该方法具有步骤简单,重现性好,准确度和灵敏度高的特点。     

香豆素类荧光衍生试剂的合成及其柱前衍生氟虫腈HPLC-FLD检测方法的建立

以4-(二乙氨基)水杨醛为原料,经缩合成环、水解反应合成一种结构新颖的香豆素类荧光衍生试剂7-(二乙氨基)-2-氧-2H-色酮-3-羧酸（记为L1）;建立并优化L1与氟虫腈衍生化反应体系,优化后条件如下：催化缩合剂为1-(3-二甲基氨基丙基)-3-乙基碳二亚胺盐酸盐/4-二甲氨基吡啶,反应溶剂为二氯甲烷,L1与氟虫腈用量比为11∶1,反应时间为60 min,衍生温度为45 ℃;对衍生产物N-(3-氰基-1-(2,6-二氯-4-(三氟甲基)苯基)-4-((三氟甲基)亚磺酰基)-1H-吡唑-5-基)-7-(二乙氨基)-2-氧-2H-色酮-3-甲酰胺（记为SF1）进行分离和鉴定;在此基础上,建立氟虫腈柱前衍生化高效液相色谱-荧光检测方法,方法的检出限达到0.01 μg/L,定量限为0.036 μg/L。该方法具有较好的灵敏度、精确性和可靠性,可应用于农产品中氟虫腈残留的检测。     

快速检测饮用水中铬(VI)的光电型传感器的建立

利用二苯碳酰二肼与铬络合显色的原理,将二苯碳酰二肼固定化制成试纸条,插入自制的便携式单色光反射计中,组装出检测饮用水中铬的光电型传感器。实验结果表明:当铬的浓度范围处于0.0019～0.58mmol/L时,光反射率与铬浓度呈现良好的线性关系。经过检测条件优化后,该技术的检出限为0.00019mmol/L,检测时间为3min。此种方法检测饮用水中的铬灵敏度高、检测时间短、操作简便,能够实现铬的现场检测。     

光电型传感器在快速检测食品中过氧化氢的应用

实验建立的光电型传感器将显色剂-酶固定化制成试纸条,经过显色反应后,通过单色光照射试纸条,采集绿色反射光,并将其转化为电信号,制备光电型快速检测H2O2仪器测定食品中过氧化氢。结果表明,H2O2与试条反应75s后,试条显色后反射率与相应的H2O2浓度呈现良好的线性关系,线性回归方程为Y=-0.52913X 2.14664,相关系数r=0.99465(p<0.0001),检测范围为0.5mg/L至30mg/L,准确率为99.5%,RSD为2.3%,平均回收率为95.7%,检测时间低于2min,可实现过氧化氢现场快速无试剂检测。     

Characteristic Anthocyanin Pattern from Onions and other Allium spp

Three red onion (Allium cepa) cultivars, top onion (A. cepa var. vivi-parum), A. altaicum and chive (A. schoenoprasum) contained several or all of the following anthocyanins: 3-(6′-malonyl-3′-glucosylglucoside), 3-(3′,6′-dimalonylglucoside), 3-(6′-malonylglucoside), 3-(3′-malonyl-glucoside), 3-(3′-glucosylglucoside) and 3-glucoside of cyanidin. Trace amounts of two pelargonidin derivatives and the 3,5-diglucosides of cyanidin and peonidin were for the first time reported in red onion. Carbon NMR data showed that the sugars of the 3-(6′-malonyl-3′-glu-cosylglucoside), 3-(6′-malonylglucoside) and 3-glucoside of cyanidin were pyranoses. Substitution either by sugar or acid in the sugar 3-position of an anthocyanin has never been reported outside the genus Allium.     

表没食子儿茶素没食子酸酯对米饭中污染物镉的肠吸收转运的影响

近年随着水体和土壤污染的加剧,我国大米镉污染的形势也愈发严峻。人体的镉暴露途径主要是膳食,镉消化后主要在机体内的小肠部位吸收。本研究首先测定大米及蒸煮米饭中污染物镉的含量,利用已建立的体外口腔-胃-肠消化模型来测定米饭消化后镉的生物可给性,最后采用Caco-2/HT-29细胞共培养肠吸收模型来研究表没食子儿茶素没食子酸酯（(-)-epigallocatechin-3-gallate,EGCG）干预对米饭中镉吸收转运率的影响。结果表明：胃消化2 h的生物可给性为（73.58±1.92）%,肠消化7 h的生物可给性为（36.29±1.25）%;EGCG干预后米饭消化液中镉的吸收转运率显著降低,与对照组相比,21.82 μmol/L和43.64 μmol/L EGCG使镉的吸收转运率分别降低了5.56%和13.89%,该研究为镉暴露地区人群的膳食策略提供了新的思路。     

Identification of the key odorants in raw French beans and changes during cooking

 By application of aroma extract dilution analysis (AEDA) to an extract prepared from raw French beans, 25 odour-active compounds with flavour dilution (FD) factors in the range 4–2048 were detected and subsequently identified. Among them, (Z)-3-hexenal (green, leaf-like), 1-octene-3-one (mushroom-like), 3-isobutyl-2-methoxypyrazine (earthy, beany) and (E,Z)-2,6-nonadienal (cucumber-like) showed the highest FD factors. In an extract prepared from the same amount of cooked beans, 3-isobutyl-2-methoxypyrazine was identified as the most potent odorant, followed by 1,5-(Z)-octadiene-3-one (geranium-like), 3-isopropyl-2-methoxypyrazine (earthy, beany), 3-(methylthio)propanal (methional; cooked potato), 4,5-epoxy-(E)-2-decenal (metallic) and an unknown compound (FD 256) with a smell of geranium leaves. A decrease in (Z)-3-hexenal and 1-pentene-3-one (etheral, pungent) and an increase in methional during cooking were shown to be mainly responsible for the flavour changes induced by cooking the beans. Received: 22 January 1998 / Revised version: 16 March 1998     

Identification of the key odorants in raw French beans and changes during cooking

 By application of aroma extract dilution analysis (AEDA) to an extract prepared from raw French beans, 25 odour-active compounds with flavour dilution (FD) factors in the range 4–2048 were detected and subsequently identified. Among them, (Z)-3-hexenal (green, leaf-like), 1-octene-3-one (mushroom-like), 3-isobutyl-2-methoxypyrazine (earthy, beany) and (E,Z)-2,6-nonadienal (cucumber-like) showed the highest FD factors. In an extract prepared from the same amount of cooked beans, 3-isobutyl-2-methoxypyrazine was identified as the most potent odorant, followed by 1,5-(Z)-octadiene-3-one (geranium-like), 3-isopropyl-2-methoxypyrazine (earthy, beany), 3-(methylthio)propanal (methional; cooked potato), 4,5-epoxy-(E)-2-decenal (metallic) and an unknown compound (FD 256) with a smell of geranium leaves. A decrease in (Z)-3-hexenal and 1-pentene-3-one (etheral, pungent) and an increase in methional during cooking were shown to be mainly responsible for the flavour changes induced by cooking the beans. Received: 22 January 1998 / Revised version: 16 March 1998     

烟叶中多菌灵胶体金定量试纸条的研制及应用

为了建立烟叶中残留的多菌灵的快速定量检测方法,利用胶体金免疫层析技术并配套胶体金读数仪,确定更适用于现场检测的多菌灵试纸条的产品形式,明确温度对胶体金试纸条定量结果的影响,用恒温孵育器控制检测温度,基于胶体金读数仪绘制标准曲线。结果表明:①研制的定量胶体金试纸条检测限为0.017 mg/kg,检测范围为0.020~2.0 mg/kg,定量范围为0.020~0.50 mg/kg,加标回收率为95.6%~128.9%,批内变异系数为6.2%~11.2%;②与高效液相色谱-串联质谱法的检测结果相比,阴性样品检测结果准确率大于95%,阳性样品的检测结果在定量范围0.020~0.50 mg/kg内线性关系良好;③对于与多菌灵结构相似的药物,试纸条与其无交叉反应,可特异性定量检测烟叶中残留的多菌灵。本研究中研制的多菌灵定量试纸条具有操作简便、检测速度快、准确性高、稳定性好等优点,适用于基层实验室的大批量样品检测及现场快速检测。      

ARO10基因在Saccharomyces cerevisiae中的克隆表达及其对3-甲硫基丙醇合成代谢的影响

研究了脱羧酶ARO10基因克隆与过量表达对酿酒酵母INVSc1 3-甲硫基丙醇合成途径的代谢流量影响。将脱羧酶基因ARO10与穿梭质粒pYES2连接,构建其酿酒酵母表达质粒(载体)pYES2-ARO10,LiAc/SSD-NA/PEG方法转化酿酒酵母菌株INVSc1中进行表达,验证ARO10基因过量表达对发酵产物3-甲硫基丙醇影响。结果表明,构建的酿酒酵母转化子SC10-1发酵120 h时,3-甲硫基丙醇生成量达到0.90 g/L,与未导入脱羧酶ARO10基因的对照菌株相比,3-甲硫基丙醇产量提高55.2%。因此,S.cerevisiae s288c中脱羧酶(EC 4.1.1.72)是3-甲硫基丙醇生物合成途径的关键限速酶,其增强脱羧酶基因ARO10的克隆及基因表达,有利于提高3-甲硫基丙醇的合成代谢流量。     

超高效液相色谱串联-质谱法同时测定香辛料中7种真菌毒素

建立了同时测定香辛料中7种真菌毒素的超高效液相色谱-串联质谱分析方法(UPLC-MS/MS)。选用香辛料中的辣椒、花椒和八角为研究对象,粉碎后的样品用70%甲醇水溶液提取,6合1免疫亲和柱净化,ACQUITY UPLC HSS T3色谱柱分离,超高效液相色谱-串联质谱测定,电喷雾正离子(ESI+)多反应离子监测方式监测,外标法定量。结果表明,7种真菌毒素在各自的线性响应范围内线性关系良好,相关系数均不低于0.995,7种真菌毒素的定量限为0.5~20 μg/kg。低、中、高3个加标水平平均回收率(n=6)为67.25%~113.47%,相对标准偏差(RSD)为1.07%~10.20%。该方法具有前处理简单、净化效果好、灵敏度高和高通量检测的优点,适用于香辛料中多组分真菌毒素残留的分离和检测。     

INT reduction as a basis for determining bakers' yeast viability

Two rapid and simple methods for determining the reduction of 2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyltetrazolium chloride (INT) to INT-formazan by bakers' yeast were compared. The first method involves counting with a light microscope the number of yeast cells containing INT-formazan crystals. In the second method, INT-formazan is extracted from cells retained on membrane filters, using dimethyl sulphoxide. The INT-formazan is then quantitated by absorption spectrophotometry. Several brands of bakers' yeast of various ages were tested. Results obtained with the two methods were closely correlated. The extraction method is the more rapid and convenient of the two assays investigated and may be used to follow change in activity with time, compare various yeast brands or investigate the effect of various environmental conditions on yeast INT-dehydrogenase activity.