单扫描极谱法快速测定牛奶中的三聚氰胺

三聚氰胺在KOH-Na2SO3体系中有一灵敏的氧化峰,峰电位为-0.34 V(vs.SCE),二阶导数峰峰电流与三聚氰胺浓度在1.0×10-2-10.0 mg/L范围内呈良好的线性关系(r=0.9992)。实验发现,将含有150 g/L NaCl的牛奶溶液在100℃中放置10 min,能够有效地避免胶体蛋白的干扰,从而将极谱法成功用于牛奶中三聚氰胺的检测。当牛奶中三聚氰胺含量在0.4~10.0 mg/L时,其浓度与峰电流成线性关系,检测限可达0.1 mg/L,回收率在78.2%~92.5%之间,整个检测时间不超过20 min。     

液相色谱-质谱/质谱法对多种食品基体中三聚氰胺的检测

采用超声、振荡、液液萃取、离心等方法提取14种复杂食品基体中的三聚氰胺,提取液经阳离子交换固相萃取柱净化后,采用液相色谱-质谱/质谱法测定多种食品基体中的三聚氰胺.涉及的食品基体包括豆类制品、饮料、糕点、含乳饼干、鲜蛋、蛋制品和调味品6类基体14种食品.方法的检出限为0.005 ～0.012 5 mg/kg,回收率为75% ～115%,RSD小于18%;定量下限为0.025 ～0.062 5 mg/kg,回收率为84% ～106%,RSD小于10%.中、高浓度添加回收率为82% ～110%,RSD小于12%.方法灵敏、准确、有效.     

应用亲水作用色谱检测鸡蛋和肉中三聚氰胺及三聚氰酸二酰胺

应用亲水作用色谱(HILIC)对从市场上购买的鸡蛋和肉中的三聚氰胺及三聚氰胺降解产物三聚氰酸二酰胺进行了检测。采用的色谱柱为ZIC-HILIC柱,流动相为3 mmol/L磷酸二氢铵溶液(pH 6.9)-乙腈(20:80, v/v),流速为0.8 mL/min,检测波长为220 nm。在该体系下,三聚氰胺和三聚氰酸二酰胺的保留时间适中,与样品中的内源性物质有良好的分离。样品经0.1%磷酸提取,偏磷酸及乙腈沉淀蛋白质和糖类物质,以及P-SCX固相萃取柱净化。三聚氰胺和三聚氰酸二酰胺在0.4～40 mg/L范围内与峰面积呈良好的线性关系,样品定量限(按信噪比(S/N)不小于10计)为2 mg/kg,在2～10 mg/kg添加水平下的平均回收率为80%～105%,相对标准偏差小于10%。该方法具有良好的分离选择性,可用于鸡蛋和肉中三聚氰胺和三聚氰酸二酰胺的同时检测。     

表面增强拉曼光谱法同时检测奶粉中三聚氰胺和二聚氰胺

本文建立了奶粉中同时检测三聚氰胺及二聚氰胺的表面增强拉曼光谱法.奶粉样品经15％三氯乙酸溶液提取,中性氧化铝吸附杂质后进行拉曼光谱检测.三聚氰胺线性范围为0.0050～0.075 mg/L,检出限为0.0015 mg/L,回收率在79.5％～124％之间,相对标准偏差小于8.8％(n=5);二聚氰胺线性范围为0.50～l0mg/L,检出限为0.15 mg/L,回收率在76.5％～112％之间,相对标准偏差小于9.4％(n=5).该方法相比常规表面增强拉曼光谱法,仅通过一种样品前处理手段即可对奶粉中的三聚氰胺或二聚氰胺进行定性检出及定量分析,相比色谱等检测方法具有样品前处理过程简单、耗时短等优点,在奶粉质量监控方面具有良好的应用前景.     

巴比妥酸衍生物荧光增强法快速测定牛奶中的三聚氰胺

建立了一种简单快速测定三聚氰胺的方法. 在pH=7.0的磷酸盐缓冲溶液中, 三聚氰胺与巴比妥酸衍生物(DBA)形成稳定的氢键, 使三聚氰胺的荧光强度显著增强, 由此建立了巴比妥酸衍生物荧光增强测定牛奶中三聚氰胺的新方法. 在优化的条件下, 该方法的线性范围为12.5~1250 μg/L, 检出限为7.5 μg/L, 相对标准偏差为2.06%, 样品平均加标回收率为96.62%. 本方法简便、快速、准确, 可用于大量牛奶样品中三聚氰胺的快速检测.     

毛细管气相色谱法测定小麦粉中的过氧化苯甲酰

在国标GB／T18415—2001的基础上,以OV-1701石英毛细管柱为分析柱、氢火焰离子化检测器为检测器,采用气相色谱法测定小麦粉中的过氧化苯甲酰。小麦粉中过氧化苯甲酰测量结果的相对标准偏差小于1.1％,加标回收率为96．5％～101．0％,检出限为10μg／mL,样品分析时间约为20min。与国标方法相比,该法不仅缩短了检测时间,而且提高了检测灵敏度。     

喷雾干燥法制备乳粉中三聚氰胺质控样品

建立乳粉中三聚氰胺质控样品的制备方法。将三聚氰胺标准溶液与乳粉复原乳通过混匀、均质、巴杀、浓缩、喷雾干燥、混合等步骤，制备得到乳粉基质的三聚氰胺质控样品，对均匀性和稳定性评估，由8家实验室依据GB/T22388—2008《原料乳与乳制品中三聚氰胺检测方法》对质控样品的三聚氰胺含量进行联合定值，评定定值结果的测量不确定度。结果表明采用喷雾干燥法制备得到的三聚氰胺质控样品，均匀性良好，稳定性达到24个月，定值结果为（2.22±0.38） mg/kg,k=2。     

用于乳制品中三聚氰胺含量测定的固相萃取富集流动注射紫外光度法

给出了一种新的流动注射在线自动固相萃取富集紫外光度分析方法和系统。对该系统相关的各种影响因素,如三聚氰胺溶液酸度、三聚氰胺紫外吸收光谱、柱洗脱-采样时间、样品定量环体积、系统流量、载流种类、沉淀剂、离心转速、共存离子干扰等影响因素进行了优选和考察;在最优条件下,成功测定了多种乳制品中的三聚氰胺含量,回收率在94.2%～105.4%范围内;分析范围为0.1～3.0 mg/L(r=0.9983),相对标准偏差小于3.6%,检出限为0.1 mg/L,每小时可自动处理15个样品左右。无需与高效液相色谱联用,实现了样品萃取、富集、杂质清洗、分离、样品洗脱、样品定量注入及测定过程的自动完成。     

高效毛细管电泳浊度法检测牛奶及奶粉中的三聚氰胺

建立高效毛细管电泳(HPCE)浊度法检测牛奶和奶粉中三聚氰胺的方法。样品中加入三氯乙酸水溶液,加热样品至沸腾后自然冷却,使蛋白质充分凝聚、沉降,并提取三聚氰胺。色谱条件为:毛细管柱长度50cm、内径75μm,分离电压13kV,进样量12.3kPa×3s,分离温度25℃,检测波长236nm。加标回收率为83%～98%之间,定量限为1mg/kg。测量结果的相对标准偏差为1.8%～3.4%(n=5)。该法可用于大量牛奶和奶粉样品中三聚氰胺的快速检测。     

拉曼光谱在感染性疾病诊断中的应用进展

感染性疾病危害人类健康,以及全球公共卫生安全.引起感染性疾病的病原微生物种类非常复杂,已有的检测技术通常检测时间长且检出率低,因此临床上急需可用于快速诊断感染性疾病的检测技术.拉曼光谱(Raman spectroscopy)技术为无标记非侵入式检测,无需复杂的前处理,具有无损伤、检测时间短等优点,在感染性疾病快速诊断中...     

Development of nanofibrillated cellulose coated with gold nanoparticles for measurement of melamine by SERS

The objective of this study was to develop nanofibrillated cellulose (NFC)-based substrate for rapid detection of melamine in milk by surface-enhanced Raman spectroscopy (SERS). NFC were served as a highly porous platform to load with gold nanoparticles (AuNPs), which can be used as a flexible SERS substrate with nanoscale roughness to generate strong electromagnetic field in SERS measurement. The NFC/AuNP substrate was characterized by UV–Vis spectroscopy and electron microscopy. Milk samples contaminated by different concentrations of melamine were measured by SERS coupled with NFC/AuNP substrate. The spectral data analysis was conducted by multivariate statistical analysis [i.e. partial least squares (PLS)]. Satisfactory PLS result for quantification of melamine in milk was obtained (R = 0.9464). The detection limit for melamine extracted from liquid milk by SERS is 1 ppm, which meets the World Health Organization’s requirement of melamine in liquid milk. These results demonstrate that NFC/AuNP substrate has improved homogeneity and can be used in SERS analysis for food safety applications.     

Rapid detection of melamine with 4-mercaptopyridine-modified gold nanoparticles by surface-enhanced Raman scattering

A surface-enhanced Raman scattering (SERS) strategy based on 4-mercaptopyridine (MPY)-modified gold nanoparticles (AuNPs) was developed for the rapid and sensitive detection of melamine in milk powder. The SERS measurement of melamine strongly relied on the “hotspot” effect, in which AuNPs immediately aggregated upon the addition of melamine, leading to significantly enhanced Raman intensity of the reporter molecule MPY and a color change for the solution from red to blue-gray. The limit of detection based on a signal to noise of 3 (S/N = 3) was found to be as low as 0.1 ppb of melamine, with an excellent linearity of 0.5–100 ppb, demonstrating a higher sensitivity and a wider quantitation range than direct SERS sensing methods based on enhanced substrate. An impressive specificity for melamine detection over various common metal ions and excipients in dairy products, even at concentrations of 100-fold higher than melamine, was achieved. Good recoveries of 88.5% and 111.7% were obtained from milk samples spiked to 20 and 100 ppb levels, respectively. The proposed method is potentially applicable for the rapid in situ determination of melamine in complex matrices.     

固相萃取-表面增强拉曼光谱法测定奶粉中三聚氰胺

建立了固相萃取-表面增强拉曼光谱法(SPE-SERS)测定奶粉中三聚氰胺的分析方法。待测物经乙腈提取、活性碳吸附及氢氧化钠溶液洗脱后进行SERS检测。该方法的线性范围为0.005 0~1.6 mg/L,检出限为0.100 mg/kg,回收率为75.3%~125%,相对标准偏差(RSD,n=5)不大于9.3%。该法灵敏度高、杂质干扰小、结果准确可靠,能满足奶粉中三聚氰胺的快速检测,在奶粉质量监控方面具有良好的应用潜力。     

Selective melamine detection in multiple sample matrices with a portable Raman instrument using surface enhanced Raman spectroscopy-active gold nanoparticles

Melamine adulteration of food and pharmaceutical products is a major concern and there is a growing need to protect the public from exposure to contaminated or adulterated products. One approach to reduce this threat is to develop a portable method for on-site rapid testing. We describe a universal and selective method for the detection of melamine in a variety of solid matrices at the 100–200 μg L⁻¹ level by surface enhanced Raman spectroscopy (SERS) with gold nanoparticles. With minimal sample preparation and the use of a portable Raman spectrometer, this work will lead to field-based screening for melamine adulteration. Citrate coated gold nanoparticles (Au NPs) were investigated for both colorimetric and Raman-based responses. Several non-hazardous solvents were evaluated in order to develop a melamine extraction procedure safe for field applications. Au NP agglomerates formed by the addition of isopropanol (IPA) prior to sample introduction enhanced the Raman signal for melamine and eliminated matrix interference for substrate formation. The melamine Raman signal resulted in a 10⁵ enhancement through the use of Au NP agglomerates. To our knowledge, we have developed the first portable SERS method using Au NPs to selectively screen for the presence of melamine adulteration in a variety of food and pharmaceutical matrices, including milk powder, infant formula, lactose, povidone, whey protein, wheat bran and wheat gluten.     

亲水作用色谱-电喷雾串联质谱法检测原料奶及奶制品中的三聚氰胺

建立了亲水作用色谱-电喷雾串联质谱测定原料奶及奶制品中三聚氰胺的方法。样品采用1%三氯乙酸水溶液-乙腈（体积比为1∶1）混合溶液提取,混合型阳离子交换反相固相萃取柱（MCX）富集净化,亲水作用色谱柱分离,电喷雾串联四极杆质谱仪进行检测。结果表明,三聚氰胺的质量浓度在0.05～10.0 mg/L范围内具有良好的线性关系。原料奶及奶制品中的三聚氰胺在0.5,2.5和10 mg/kg 3个添加水平下,平均回收率为76.3%～98.7%,相对标准偏差均小于6.8%;定量限（S/N＞10）为0.05 mg/kg。     

Detection of Melamine in Powdered Milk Using Surface-Enhanced Raman Scattering with No Pretreatment

We detected a trace amount of melamine in powdered milk using surface enhanced Raman scattering (SERS) on gold surfaces at an excitation wavelength of 632.8 nm. A detection limit of ～100 ppm (μg/g) melamine in milk was attained within a few minutes by the gold nanoparticle substrate from chemical reduction; whereas, better sensitivity, as low as ～200 ppb (ng/g), was achieved by the roughened gold substrate. Our method has the advantage of fast and sensitive detection of melamine in powdered milk without pre-treating the samples.     

Rapid determination of melamine in milk and milk powder by surface-enhanced Raman spectroscopy and using cyclodextrin-decorated silver nanoparticles

We have synthesized silver nanoparticles (AgNPs) decorated with α-cyclodextrin (CD) by using the traditional silver mirror reaction in the presence of CD. The CD-AgNPs were used as substrate in surface-enhanced Raman spectroscopy (SERS) for determining melamine. The intensity of the Raman band of melamine at 704 cm^?1 was used to determine melamine in milk and milk powder. The use of CD-AgNPs as the SERS substrate rather than classical silver nanoparticles makes the method more sensitive in giving an enhancement by a factor of up to?~?10⁶ in scattering efficiency. The effects of the volume of solutions (of CD-AgNPs, NaCl, NaOH, melamine) and of mixing time were optimized. The standard addition method was employed for quantitative analysis. The correlation coefficient of the calibration plot is 0.9995, and the limit of detection is 3.0 μg L^?1. The method was successfully applied to the determination of melamine in milk and milk powder, with relative standard deviations of <10 % and recoveries between 89 and 104 %.

Synthesis of magnetic polyphosphazene-Ag composite particles as surface enhanced Raman spectroscopy substrates for the detection of melamine

Magnetic polyphosphazene(MPZS) particles coated by Ag nanoparticles(MPZS-Ag) have been developed as surface enhanced Raman spectroscopy(SERS) substrates for sensitive detection of melamine in aqueous solutions and milk samples.5,5'-Dithiobis-(2-nitrobenzoic acid)(DTNB) was used as model analyte to test the SERS activity of the MPZS-Ag particles.The prepared MPZS-Ag particles possess both magnetic responsiveness and excellent SERS properties.SERS detection of different concentrations of melamine aqueous solutions and spiked milk samples were performed by the MPZS-Ag particles.The limit of detection(LOD) of the melamine in aqueous solutions was 10-7 mol/L(0.0126 mg/L) and 0.6 mg/L in real milk samples using the MPZS-Ag particles as SERS substrates.The LOD of the melamine are much lower than the safety values of Food and Drug Administration and Codex Alimentarius Commission.These results indicate that the MPZS-Ag particles have promising application prospect for SERS analysis in food safety fields.     

Detection of melamine in milk by surface-enhanced Raman spectroscopy coupled with magnetic and Raman-labeled nanoparticles

A new method based on surface-enhanced Raman spectroscopy (SERS) has been developed for sensitive and rapid detection of melamine. Spherical magnetic-core gold-shell nanoparticles (AuNPs) and rod-shaped gold nanoparticles (nanorods) labeled with a Raman-active compound were used to form a complex with the melamine molecules. 5,5'-Dithiobis(2-nitrobenzoic acid) was used as Raman-active compound because it is readily adsorbed by a gold nanoparticle surface forming a self-assembled monolayer (SAM) and has strong Raman scattering at 1330 cm(-1), because of the symmetric NO(2) stretch. The calibration curve was obtained by plotting Raman band area at 1330 cm(-1) against melamine concentration. A linear relationship was obtained with a high determination coefficient (R(2)=0.997). The method was validated for linearity, sensitivity, precision (intra-day and inter-day repeatability), and recovery. In the model system, the limits of detection (LOD) and quantification (LOQ) were 0.38 and 1.27 mg L(-1), respectively. For melamine-spiked milk samples, LOD and LOQ values were 0.39 mg L(-1) and 1.30 mg L(-1), respectively. Intra and inter-day precision were 3.73 and 4.94 %, respectively. This method was applied to samples of skimmed milk that had been spiked with melamine at different concentrations. The recovery of the method was 95-109 % in the concentration range 2-15 mg L(-1), and average RSD was 1.71 %. Total analysis time was less than 15 min.