气相色谱-质谱联用分析三聚氰胺的方法研究

建立了使用气相色谱一质谱(GC-MS)测定食品中三聚氰胺含量的分析方法.利用三乙胺、水、甲醇(10/30/60)超声革取样品中的三聚氰胺,将提取液离心、过滤、衍生后采用GC-MS的单反应离子选择模式(SIM)进行检测.方法在0.1～50mg/L范围内呈现良好的线性关系,而且灵敏度高,最低检测限0.1 μ g/g.应用所建立的方法测定了奶粉食品中的三聚氰胺含量,为三聚氰胺滥用的检测和判断提供了方法.     

银杏叶荷叶总黄酮的提取及保健饮料的研制

以总黄酮为评价指标,优化银杏叶和荷叶的浸提工艺;以感官质量为评价指标,在单因素试验的基础上,采用正交试验设计优化银杏叶荷叶保健饮料工艺.结果表明:银杏叶总黄酮的最佳浸提工艺为:80℃浸提50 min,此条件下银杏叶总黄酮提取率为8.78 mg/g;荷叶总黄酮的最佳浸提工艺为:90℃浸提50 min,此条件下荷叶总黄酮提取率为53.50 mg/g.银杏叶荷叶保健饮料的最优配方为:银杏叶浸提液15%(体积百分比浓度),荷叶浸提液20%(体积百分比浓度),白砂糖10%(质量百分比浓度),柠檬酸0.15%(质量百分比浓度).此条件下,银杏叶荷叶保健饮料酸甜适中,色泽均匀,总黄酮含量为0.68 mg/mL.     

环境友好型水处理剂阻垢缓蚀性能研究

聚天冬氨酸(PASP)具有缓蚀和阻垢双重功能,但用做缓蚀剂时用量较大(100 mg/L).为了降低成本,对聚天冬氨酸、苯并三氮唑(BTA)、钨酸钠和葡糖酸钠进行四元复配研究,得到最佳配方为10 mg/L PASP+0.5 mg/L BTA+20 mg/L钨酸钠+10 mg/L葡萄糖酸钠(总浓度为40.5 mg/L).通过静态阻垢试验、旋转挂片试验、小型动态模拟试验、扫描电镜分析和生物降解试验,对复合配方阻垢缓蚀性能进行了全面研究,该配方对铜的阻垢率和缓蚀率分别为99.22%和0.000 6 mm/a,生物降解率在28 d时高达75.1%,试验结果表明,该配方水处理剂具有较好的阻垢缓蚀效果,且易生物降解,属于环境友好型水处理剂范畴.     

罗丹明6G在多孔硅-银粒子复合基底上的表面增强拉曼散射

多孔硅与货币金属(Au、Ag、Cu)的复合材料在表面增强拉曼光谱领域有很大的应用前景。本文采用恒电流电解法分别制备了具有均匀纳米孔洞的低阻多孔硅和具有多层次微纳米结构的高阻多孔硅，并开发了一种将铈掺杂进入银胶体中形成铈掺杂的银纳米粒子的方法。作为固态SERS基底的一种制备方式，将银颗粒在多孔硅表面固定化，获得了具有很强选择性的复合基底。以罗丹明6G(Rhodamine 6G, R6G)作为探针分子的拉曼测试表明：多孔硅-银粒子复合基底对较大拉曼位移的拉曼峰(1 590 cm^-1)更加敏感，铈掺杂则进一步增强1 360 cm^-1处的拉曼峰；且复合基底能够检测到10^-9 mol/L浓度的R6G。     

高效液相色谱法测定鸡蛋中三聚氰胺含量

根据三聚氰胺性状,对鸡蛋中三聚氰胺检测进行了方法建立及实际样品测定.试样用三氯乙酸溶液-乙酸铅提取,用C8柱进行分离,在240nm紫外波长下检测,外标法定量.三聚氰胺在0.200～1.500 mg/L浓度范围内呈良好线性.三聚氰胺添加回收率在94%～108%之间,相对标准偏差均＜5%,满足鸡蛋中三聚氰胺含量测定的要求.     

三聚氰胺对吉富罗非鱼的急性毒性研究

采用接触、腹腔注射及口服3种致毒方式,对吉富罗非鱼(GIFT Oreochromis niloticus)进行三聚氰胺的急性毒性研究.口服急性毒性实验中,在饲料中添加不同浓度的三聚氰胺,进行21d的吉富罗非鱼摄食养殖实验,实验鱼初体重为(55.00±0.05)g.实验结果表明:三聚氰胺溶解度较低,在接触实验中其水溶液没有表现出毒性,96LC50>3500mg/L;而在腹腔注射致毒方式下,三聚氰胺对吉富罗非鱼的半致死剂量LD50=1311.90mg/kg;LD5095%可信限为1169.06～1472.21mg/kg;在21d口服急性毒性实验中,添加三聚氰胺后不同程度地降低了吉富罗非鱼的摄食率和特定生长率,但对存活率和饲料系数均无显著影响.三聚氰胺对吉富罗非鱼21d的最大未观察到有害作用剂量(no-observed-adverse-effect-level,NOAEL)为31.00mg/(kg*d).     

固相萃取与高效液相色谱联用快速测定鲜奶中的三聚氰胺

采用固相萃取-高效液相色谱法测定鲜奶样品中的三聚氰胺.固相萃取柱为Strata-X-C,液相色谱柱Thermo BDS HYPERSIL C8(4.6 mm×250 mm,5μm);流动相为乙腈:0.01 mol/L辛烷磺酸钠-柠檬酸缓冲溶液(10:90,V:V),检测波长为 238 nm.三聚氰胺峰的保留时间为 8.25 min.三聚氰胺在 1.0～50μg/mL 范围内具有良好的线性关系(R=0.997),在添加量为30,60,90 mg/kg 时,三聚氰胺标准加入回收率为90.40%～91.10%,RSD为1.14%～1.88%.方法检出限为0.1 mg/kg.     

喷墨打印纸质SERS基底应用于水果中福美双的检测

采用喷墨打印技术在疏水性相片纸表面沉积银纳米薄膜，制备了一种高效的纸质表面增强拉曼散射（SERS）基底（银纳米薄膜/相片纸），并利用接触角测量仪与扫描电子显微镜（SEM）表征相片纸书写前后的浸润性和表面形貌.通过模拟福美双在果皮表面及果汁中的残留状态，对银纳米薄膜/相片纸基底的应用潜力进行评价.研究发现，该基底可以直接识别出果汁溶液或果皮表面掺杂的福美双分子，不需作任何预处理.对掺杂福美双的果汁最低检测的质量浓度低至0.024 mg∙L^-1，且特征峰强度与浓度间具有较好的线性关系；对果皮表面残留福美双分子的检测限为0.25 ng∙cm^-2.此外，在吸附福美双/果汁的基底表面随机选取10个点，研究银纳米薄膜/相片纸的均匀性，经计算1 142和1 377 cm^-1处的特征峰的相对标准偏差分别为7.8%和5.7%.结果表明：银纳米薄膜/相片纸在农药残留检测方面具有潜在的应用前景.     

反相离子对HPLC法同时测定盐酸二甲双胍中双氰胺和三聚氰胺的含量

建立一种简单的反相离子对HPLC方法测定盐酸二甲双胍中的双氰胺和三聚氰胺的含量.使用Hypersil ODS C18反相色谱柱(5μm;250×4.6 mm),乙腈-离子对试剂水溶液(10 mmol/L戊烷磺酸钠+10 mmol/L柠檬酸,pH为3.0,体积比10∶90)为流动相,流速1.0 mL/min,检测波长217 nm,柱温25℃.结果表明:双氰胺在0.02²0μg/mL浓度范围内线性关系良好,相关系数R=0.999 9,平均回收率为97.6%,RSD=0.29%;三聚氰胺在0.0220μg/mL浓度范围内线性关系良好,相关系数R=0.999 9,平均回收率为97.6%,RSD=0.29%;三聚氰胺在0.02⁵0μg/mL浓度范围内线性关系良好,相关系数R=0.999 9,平均回收率96.5%,RSD=0.32%.双氰胺和三聚氰胺的检出限分别为4.0 ng/mL和6.0 ng/mL.该方法简单、快速、准确、灵敏,适于同时测定盐酸二甲双胍制剂中的双氰胺和三聚氰胺的含量.     

三聚氰胺降解菌的分离鉴定及其生物炭固定化研究

从农田土壤中分离筛选出一株能以三聚氰胺为唯一氮源和碳源生长的细菌MB4,经形态学观察、生理生化特征和16SrRNA序列分析,初步鉴定为洋葱伯克霍尔德菌(Burkholderia cepacia).菌株在10d内对30mg/L三聚氰胺的降解率达到81.67%,其最适生长条件为初始pH7~8,温度32~37℃.动力学研究显示,在底物浓度为10~50mg/L时,米氏方程常数Km=2.545mg/L,最大降解速率为1.24mg/(L·h).经过35d实际土壤培养后,生物炭固定化降解菌MB4对黑土中50~400 mg/kg三聚氰胺的降解效率可达52.83%~70.33%,其降解动态符合Logistic方程.     

银纳米颗粒溶胶表面增强红外基底对低浓度福美双农药的快速检测

采用水热法制备了一种银纳米颗粒溶胶,通过乙醇洗涤后得到银纳米颗粒表面增强红外基底,用于检测低浓度福美双农药。结果表明,该增强基底可检测低至10^-7mol/L的福美双农药,且不同浓度下福美双溶液的表面增强红外光谱强度呈现良好的线性关系,该基底对福美双分子的红外光谱增强能力高达150倍。银纳米颗粒的富集作用、电荷转移机制和电磁增强机制的共同作用使福美双的红外光谱得到显著增强。     

Organic media enhanced spectrofluorimetric determination of L-ascorbic acid

A novel spectrofluorimetric method for the determination of L-ascorbic acid is proposed. It is based on the inhibition of L-ascorbic acid on the formation of 2,3-diaminophenazine, which is an oxidation product ofo-phenylenediamine catalyzed by laccase. The fluorescence (at λ_cx/λ_cm=464 nm /530 nnm) was enhanced strongly in the presence of organic media. The mechanism ofo-phenylenediamine oxidation reaction catalyzed by laccase in the presence of L-ascorbic acid is discussed. L-ascorbic acid is determined in the ethanol, 1,4-dioxane and acetone over the linear range of 4.0×10⁻⁷≈1.2×10⁻⁴ mol/L, 4.0×10⁻⁷≈8.0×10⁻⁵ mol/L and 4.0×10⁻⁷≈1.0×10⁻⁴ mol/L with a detection limit of 1.20×10⁻⁵ mol/L, 1.19×10⁻⁵ mol/L and 1.24×10⁻⁸ mol/L, respectively. The method has been successfully applied to the simple and rapid determination of L-ascorbic acid in pharmaceuticals and milk powder. Supported by National Natural Science Foundation of China and the Special Funds of State Education Committe for Doctorate Research Huang Zuyun: born in Aug. 1963. Ph.D     

乳酸菌计数结果的比较研究

通过流式细胞术(FCM),利用SYTO?24与PI双染色对发酵乳制品即发酵乳饮料和发酵乳中的乳酸菌进行快速检测,并将检测结果与用现行国标中推荐的平板计数法检测得到的结果相比较,两者对发酵乳饮料和发酵乳中乳酸菌的计数结果的相关性系数分别为:0. 9014;和0. 9653,都符合较好.而且FCM稳定性更好,活性细菌的变异率为3. 46%,非活性细菌的变异率为3. 56%;检测速度更快,单样品检测时间不超过10 min;灵敏度更高(10~3AFU·mL~(-1)) FCM在需要快速放行的液体产品检测领域中具有广阔的应用前景.     

Highly sensitive detection of melamine based on reversed phase liquid chromatography mass spectrometry

In this work, we developed a highly sensitive method to detect melamine based on reversed phase liquid chromatography mass spectrometry. A mass spectrometry compatible ion pair, heptafluorobutyric acid(HFBA), was used to separate melamine by reversed phase liquid chromatography prior to electrospray mass spectrometry. The incorporation of isotope internal standard and multiple reaction monitoring improved the accuracy and linearity of quantification. Based on this strategy, the method limit of quantification was 0.1 ng/g. The limits of quantification were 8 ng/g for liquid milk and 15 ng/g for dry milk powder. This method provided a reproducible and stable approach to sensitive detection and quantification of melamine. Supported by the National Natural Science Foundation of China (Grant No. 30425021) and National High Technology Research and Development Program of China (Grant No. 2007AA02Z334)     

Determination of the total concentration of casein and β-lactoglobulin by indirect competitive ELISA in milk and dairy products

The main purpose of this work was to develop an assay as a means of quality control in milk and dairy products. As specific and high abundant proteins in milk and diary products, casein and β-lactoglobulin were chosen as the targets, and an indirect competitive enzyme-linked immunosorbent assay （ELISA） was developed for determination of the total concentration of casein and β-lactoglobulin. The detection limit of the assay was 79.07 ng/mL, and a working range of the calibration curve was from 140.6 to 36,000 ng/mL. The intrassay and inter-assay coefficients of variations were 4.7 % and 6.5 %, respectively. The recoveries ranged from 94.1% to 106.6 %. The developed ELISA assay was used to detect the total con- centration of casein and β-lactoglobulin in liquid milk and milk powder. The results indicated that the developed assay was very specific, and the addition of nonprotein nitrogen （such as melamine, cyanuric acid, and urea） and vegetable protein did not affect the detection. The good performance of the assay makes it suitable for use in the quality control of milk and dairy products.     

我国奶粉的质量安全问题与控制现状

主要分析了目前我国奶粉包括原料奶粉和婴儿配方奶粉行业的技术发展现状和质量控制水平,并着重探讨了乳粉加工过程中的质量控制与食品安全现状,同时对未来奶粉行业的技术发展方向、质量控制措施和食品安全管理进行了展望。     

Nitric oxide produced by cumulus cells stimulates maturation of mouse oocytes

The effect of sodium nitroprusside (SNP), a donor of nitric oxide, on meiotic maturation of mouse oocytes was studied by injecting N^w-nitro-L-arginine methyl ester (L-NAME) intra-peritoneal (ip), a nitric oxide synthase inhibitor, or culturing oocytes in the medium supplemented with L-NAME or hypoxanthine (HX) to arrest the spontaneous oocyte maturation in vitro. The results showed that the inhibitory effect of L-NAME by injecting 10 mg/kg ip on extrusion of the first polar body only could be reversed by injecting 2.5 mg/kg SNP with L-NAME simultaneously (P < 0.05). Half an hour later ten mice died when given 10 mg/kg SNP ip. The treatment of some concentrations of SNP (10^–7, 10^–6, 10^–5mol/L) significantly stimulated meiotic maturation to metaphase Ⅱ stages in cumulus enclosed oocytes in the presence of HX. However, other concentrations of SNP (10^–8, 10^–4, 10^–3 mol/L) had no effect on HX-arrested oocyte meiotic maturation. The optimal concentration of SNP on CEOs had no effect on DOs. The dose of 10^–3 mol/LL-NAME demonstrated a significant suppression in formation of PB₁, but not in GVBD. This inhibition was reversed by the addition of SNP. These results indicated that the physiological levels of NO produced by cumulus cells could stimulate meiotic maturation of mouse oocytes both in vivo and in vitro.     

Adsorption and reduction of palladium (Pd<Superscript>2+</Superscript>) by <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> R08

Preliminary study on the mechanism of Pd²⁺ biosorption by resting cells of Bacillus licheniformis R08 biomass has been carried out by means of chemical kinetics and AAS, TEM, XRD and FTIR methods. The results showed that at 30℃ and pH 3.5, when dry R08 biomass powder (800 mg/L) was mixed with Pd²⁺ (100 mg/L) for 45 min, the rate constant k of biosorption of Pd²⁺ attained a maximum of 5.97×10^-2 min^-1 and the half life period of the reaction reached 12 min. The part of Pd²⁺ adsorbed by R08 biomass was reduced to elemental, cell-bound Pd⁰ at the same condition. The cell wall of R08 biomass was the primary location for accumulating Pd²⁺ , and aldoses, i. e. hydrolysate of a part of polysaccharides on the peptidoglycan layer in the acidic medium, serving as the electron donor, in situ reduced the Pd²⁺ to Pd⁰.     

氯过氧化物酶与苯酚降解菌株的协同降解动力学研究

氯过氧化物酶(CPO)催化苯酚与H_2O_2发生过氧化反应生成邻苯二酚,能减轻苯酚对降解菌株的抑制作用,加快降解菌株对苯酚的生物降解.实验结果表明:在2 h内适量的H2O2存在时10 U/L的CPO可以使300 mg/L苯酚降解率达到67.85%,而CPO与降解菌株协同作用下苯酚降解率则可达到70.72%,比单一菌株降解率8.52%提高了62.2%.在降解体系中补充邻苯二酚进一步揭示了CPO氧化苯酚的中间产物有利于菌体细胞形成共基质效应,提高细胞的苯酚生物降解效率.降解动力学分析显示:在苯酚质量浓度为100~1 200 mg/L时,CPO与菌株协同降解体系的最大比降解速率qmax=0.000195 h-1,基质饱和常数Ks=1.0501 mg/L,基质抑制常数KI=5.1272 mg/L.     

Study on the flow injection micro-column pre-separation system coupled with high performance liquid chromatography for the determination of ecdysterone in traditional Chinese medicine

A flow injection (FI) micro-column system coupled with high performance liquid chromatography (HPLC) was proposed for the pre-separation and determination of active organic component (ecdysterone) in traditional Chinese medicine, Loulu. The factors influencing separation performance were investigated and optimized. Under the optimal conditions, the contents of ecdysterone in Loulu were determined by HPLC system using MeOH-H₂O (40∶60,V/V) as the mobile phase at a flow rate of 1.0 mL/min. The calibration curve was linear in the range of 0.5∼100 mg/L of ecdysterone concentrations. The detection limit of the analyte was 0.11 μmol/L (3σ) with a precision of 0.38% RSD (n=7,c=10.0 mg/L). The average recovery of the method was 98.7%. The proposed method has been applied to determine ecdysterone in practical samples, and the determined values by both external standard method and standard addition method were in good agreement. Compared to the traditional solid extraction method, the system proposed has the advantages of simple procedure, good reproducibility, minimum volume requirement, reduction of matrix interference and low contamination risk. Foundation item: Supported by Education Ministy Foundation for Chinese Returned Scholars and Nature Science Foundation of Hubei province (98J054). Biography: SHUAI Qin (1963-), famale, Ph.D. Candidate.