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1.
A colorimetric immunoassay has been developed based on the reduction and precipitation of silver ions catalyzed by colloidal gold. This method was evaluated for a noncompetitive heterogeneous immunoassay to detect ovalbumin as a model protein and Escherichia coli as model bacterium. The influence of relevant experimental variables, including the reaction time of antigen with antibody, the dilution ratio of the colloidal gold-labeled protein, time allowed for silver reduction/precipitation reaction and other parameters were examined and optimized. This colorimetric method of detection is convenient, easy to use and economic. The presence of the target molecules or antigens can be visually inferred based on the color change that occurs in a short time without using major instrumentation. This method is widely amenable for detection of proteins, viruses and bacteria.  相似文献   

2.
Vibrational spectroscopic characteristics of melamine, cyanuric acid, and melamine cyanurate were measured using surface-enhanced Raman spectroscopy (SERS) coupled with gold nanosubstrates. Trace amounts of melamine and its analogues (cyanuric acid and melamine cyanurate) were characterized and quantified quickly and accurately by SERS in combination with partial least squares (PLS) analysis. Based on the relationship between the Raman intensity of the most prominent peak at around 676 cm−1 and log values of melamine concentrations, the limit of detection (LOD) of SERS for melamine was estimated to be 2.6 × 10−7 mol L−1 (∼33 ppb). An approximately 3 × 104 fold of enhancement factor for SERS signals of melamine on gold nanosubstrates was obtained. This result was based upon the comparison of the peak at around 676 cm−1 in the SERS spectra with that of normal Raman spectra of melamine in aqueous solutions. SERS spectra of cyanuric acid acquired from its solid form differ significantly from this compound in an aqueous solution, indicating a possible keto-enol isomerization reaction of cyanuric acid in water. When equal amounts of melamine and cyanuric acid were added together, spoke-like crystals of melamine cyanurate formed instantly, which could be measured and characterized by SERS. This study demonstrates that SERS could provide a fast and ultra-sensitive tool for detection and characterization of melamine and its derivative compounds in aqueous solutions.  相似文献   

3.
We report a facile method for sample preparation and sensitive on-site detection of melamine in powdered infant formula and chocolate using Raman spectroscopy on sharp-edged gold nanostars (AuNSs). The aggregation of AuNSs by sodium chloride (1.2 M) facilitates the more sensitive detection of melamine in comparison with spherical gold nanoparticles (AuNPs). Density functional theory quantum mechanical calculations were performed to determine the energetic stability on gold cluster atoms. Our spectroscopic data indicated that AuNSs are an efficient platform for detecting melamine in food mixtures. The detection limits of melamine in powdered infant formula and chocolate were found to be ~0.1 mg/kg and ~1 mg/kg, respectively, on AuNPs, whereas they were observed to be ~0.01 mg/kg and ~0.1 mg/kg, respectively, on AuNSs. Using a handheld Raman spectrometer, a sub-mg/kg detection of melamine in both powdered infant formula and chocolate could be achieved within a few minutes.  相似文献   

4.
微生物法在原料奶验收中的应用   总被引:1,自引:0,他引:1  
对微生物法的应用进行了研究。采用对抗生素最敏感的嗜热链球菌为实验菌,从产酸能力和凝乳时间两个因素来检测牛乳中抗生素的残留,并定量得出该嗜热链球菌对青霉素类抗生素的最低检出量为0.04单位。结果表明,该方法操作简便。  相似文献   

5.
This paper introduces novel methods for detecting blemishes in potatoes using machine vision. After segmentation of the potato from the background, a pixel-wise classifier is trained to detect blemishes using features extracted from the image. A very large set of candidate features, based on statistical information relating to the colour and texture of the region surrounding a given pixel, is first extracted. Then an adaptive boosting algorithm (AdaBoost) is used to automatically select the best features for discriminating between blemishes and non-blemishes. With this approach, different features can be selected for different potato varieties, while also handling the natural variation in fresh produce due to different seasons, lighting conditions, etc. The results show that the method is able to build “minimalist” classifiers that optimise detection performance at low computational cost. In experiments, blemish detectors were trained for both white and red potato varieties, achieving 89.6% and 89.5% accuracy, respectively.  相似文献   

6.
高效液相色谱法分析原料乳和奶粉中三聚氰胺   总被引:1,自引:0,他引:1  
许家胜  张杰  刘连利 《食品科技》2011,(7):275-277,282
建立了二极管阵列检测器-高效液相色谱测定原料乳及奶粉中三聚氰胺的方法。奶粉样品经三氯乙酸超声提取,乙酸铅沉淀蛋白,三氯甲烷除去脂肪和非极性杂质,PROELUTPXCSPE阳离子交换固相萃取小柱进一步除去样品基质干扰,氨化甲醇洗脱。实验对色谱分离条件进行了优化,三聚氰胺的质量浓度在1.0~100.0μg/mL范围内与色谱峰面积呈良好的线性关系,回归方程为y=89.763x-113.72,相关系数为R2=0.9988。加标回收率为90.5%~105.0%,相对标准偏差(RSD)小于4.0%。该方法简单、快速,结果准确可靠。  相似文献   

7.
The monitoring of synthetic dyes in foods is very important due to their potential harmfulness to human beings. Herein, a carbon-paste electrode (CPE) that is chemically modified with gold nanoparticles (nAu) was fabricated and used for the determination of Sunset yellow (SY) and Tartrazine (Tz). Cyclic and differential pulse voltammetry (CV and DPV) results revealed two well-resolved anodic peaks for SY and Tz with remarkably increase in oxidation signals of these colourants. Based on this, a novel electrochemical method was developed for the simultaneous determination of SY and Tz. High sensitivity and selectivity, sub-micromolar detection limit, high reproducibility and regeneration of the electrode surface by simple polishing make the nAu-CPE electrode very suitable for the determination of SY and Tz in commercially available soft drinks. The detection limits was 3.0 × 10−8 and 2.0 × 10−9 mol l−1 for SY and Tz, respectively, which are remarkably lower than those reported previously for SY and Tz using other modified electrodes.  相似文献   

8.
Zhang M  Cao X  Li H  Guan F  Guo J  Shen F  Luo Y  Sun C  Zhang L 《Food chemistry》2012,135(3):1894-1900
A simple, rapid and sensitive fluorescent assay for determination of melamine has been developed based on inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs). When thioglycolic acid-capped CdTe QDs was mixed with citrate-stabilized AuNPs, the fluorescence of CdTe QDs was significantly quenched via the IFE of AuNPs. With the presence of melamine, melamine could induce the aggregation and corresponding absorbance change of AuNPs, which then resulted in the recovery of IFE-decreased emission of CdTe QDs. Under the optimum conditions, the detection limit for melamine in raw milk was 0.02mgL(-1). The application of this method in samples of melamine-spiked raw milk suggested a recovery between 103% and 104%. Therefore, the obvious merits provided by the present assay, such as simplicity, rapidity, low cost, and high sensitivity, would make it promising for on-site screening of melamine adulterant in raw milk.  相似文献   

9.
A new spectrophotometric method has been developed in this paper to determine melamine in milk by applying rank annihilation factor analysis (RAFA) based on pH gradual change-UV spectral data (pH-spectra). In the proposed method, the spectra of the sample solutions at different pH data points were recorded and the pH-spectra bilinear data matrix was generated. Based on these data, the RAFA was then applied to calculate the concentration of melamine in milk. The experiments have been conducted and the results were satisfactory. Under the optimised conditions, linearity of the proposed method was in the range of 0.04–4.0 μg mL−1 for calibration samples, and 0.04–3.5 μg mL−1 for the mixed solutions of melamine with the background milk components. The detection limit (DL) was 12 ng mL−1. The relative predictive error (RPEs) and root mean square error of prediction (RMSEP) of applying RAFA were 0.91% and 0.0151, respectively.  相似文献   

10.
原料乳中蜡样芽孢杆菌的快速检测   总被引:2,自引:1,他引:2  
目前原料乳中蜡样芽孢杆菌的检测方法繁琐费时耗力,针对此缺点建立一种操作简便快速检测方法,采用过滤富集菌体后PCR技术来检测原料乳中蜡样芽孢杆菌.整个过程只需6 h左右即可完成.检测灵敏度高达101 mL-1.这种方法是对传统检测方法的有效改进,并且达到了原料乳检测快速、准确、灵敏的要求.  相似文献   

11.
Water-soluble CdTe quantum dots of different sizes capped with thioglycolic acid (TGA-CdTe QDs) were synthesised via a microwave-assisted method. It was found that melamine could quench the fluorescence emission of TGA-CdTe QDs in aqueous solution. Based on this, a novel method for the determination of melamine has been developed. Under optimum conditions, the fluorescence intensity of TGA-CdTe QDs versus melamine concentrations gave a linear response according to the Stern-Volmer equation. The proposed method has been successfully used to detect melamine in liquid milk with a detection limit of 0.04?mg?L?1, and the whole process including sample pre-treatment could be accomplished within 30?min. The obvious merits provided by this method, such as simplicity, rapidity, low cost and high sensitivity would make it promising for on-site screening of melamine adulterant in milk products. The possible mechanism involved in the interaction of melamine with TGA-CdTe QDs is discussed.  相似文献   

12.
We applied urease-induced silver metallization on the surface of gold nanorods (AuNR) to improve colorimetric ELISA for the rapid and sensitive detection of Salmonella enterica Choleraesuis. To this end, we introduced a biotin-streptavidin system as a bridge to determine the correlation between urease and S. enterica Choleraesuis concentrations. The captured urease can catalyze the hydrolysis of urea into carbon dioxide and ammonia, and the generated ammonia can then induce the deposition of silver shell on the surface of AuNR in the presence of silver nitrate and glucose. With the decreased aspect ratio (length divided by width) of AuNR, a multicolor change of AuNR solution and a significant blue shift in the longitudinal localized surface plasmon resonance absorption peak (Δλmax) of AuNR were obtained at the target concentrations of 1.21 × 101 to 1.21 × 108 cfu/mL. Consequently, the detection limits of our proposed colorimetric ELISA were as low as 1.21 × 102 cfu/mL for qualitative detection with naked eyes, and 1.21 × 101 cfu/mL for quantitative detection, in which changes in Δλmax of AuNR were recorded with a microplate reader. These values were at least 2 to 3 orders of magnitude lower than those obtained with conventional horseradish peroxidase-based ELISA. The analytical performance of our developed colorimetric ELISA in terms of selectivity, accuracy, reliability, and practicability were investigated by analyzing S. enterica Choleraesuis-spiked pasteurized whole milk samples.  相似文献   

13.
Chloride ion concentration in milk was determined by pulsed amperometric detection in a flow injection system. Results showed that the Au electrode lost 3 electrons at 1.10 V and formed chloroaurate ions (AuCl4?) by combining with chloride ions, after which AuCl4? was partly reduced to Au at 0.6 V. Based on the electrochemical process, a triple waveform with detection potential of 1.15 V, detection time of 150 ms, oxidation potential of 1.4 V, oxidation time of 550 ms, reduction potential of 0 V, and reduction time of 400 ms was applied to the Au electrode for detecting chloride ion concentration in milk. The approach is rapid and automatic and features a detection limit of 0.005 g/L. The relative standard deviation obtained by 60 repetitive injections reached 1.48% at 2 g/L of NaCl. The method developed using the Au electrode without modification was used to analyze the chloride ion concentration in raw milk without preprocessing. The method showed good agreement with potentiometric titration.  相似文献   

14.
A rapid and simple method was established based on gold nanoparticle‐labelled monoclonal antibody probes for the detection of melamine pollution in raw milk. The conditions for conjugation between the antibody and gold nanoparticles were optimised (pH 8.0, antibody concentration 5 μg mL?1). It gives a single proportional to melamine concentration with a performance time of only 3 min. A practical calibration curve was established with a reader system with limit of detection calculated as 4.47 and 8.34 μg L?1 with naked eyes. Three structural analogues, atrazine, desethyl‐desisopropyl‐atrazine and cyromazine, were used to test the specificity of the immunochromatographic strip, and small colour changes on the strip test line were found even at the 500 ng mL?1 spiked level. Fifty raw milk samples were detected with this strip method, and the resulting data coincided well with results from gas chromatography tandem mass spectrometry. The above‐mentioned results showed that this test strip can be used for melamine screening in the daily monitoring of milk.  相似文献   

15.
生鲜牛乳中抗生素检测方法的新问题   总被引:2,自引:0,他引:2  
国家标准中明确规定了生鲜牛乳中不得检出抗生素,GB/T4789.27-2003中也规定了鲜乳中抗生素残留的检测方法,但目前使用较多的β-内酰胺酶的使用,在一定程度上对检测工作带来了困难,掩盖了抗生素的残留量.本文从牛乳中抗生素的残留来源、检测方法和β-内酰胺酶的现状、检测两个方面进行论述.  相似文献   

16.
建立高效液相色谱法测定测定原料乳与乳制品中三聚氰胺质量分数的不确定度评定方法,采用GB/T22388-2008高效液相色谱法测定测定原料乳与乳制品中三聚氰胺质量分数。建立数学模型,根据《测量不确定度评定与表示》(JJF1059—1999)中有关规定评估其不确定度。结果表明,按数学模型计算奶粉中三聚氰胺质量分数为2.70mg/kg,扩展不确定度为0.064mg/kg,结果表达为(2.70±0.064)mg/kg。该方法建立的数学模型合理、可靠。  相似文献   

17.
金纳米粒子在食品检测领域中的研究进展   总被引:1,自引:0,他引:1  
随着纳米技术的快速发展,作为纳米材料中化学性质最稳定的金纳米粒子,以其独特地光学、电学性质和良好地生物兼容性广泛的被应用于食品检测领域.文章综述了金纳米粒子在食品检测领域的最新研究进展,讨论了金纳米粒子在当前食品安全与检测领域的优势和不足,并对金纳米粒子在食品检测领域的未来发展趋势做了展望.  相似文献   

18.
通过用超声波破碎的宋内氏志贺氏菌和福氏志贺氏菌的菌体碎片为免疫原免疫BALB/c小鼠,获得4株能稳定分泌抗志贺氏菌单克隆抗体的杂交瘤细胞株,选取其中一株制备单抗,并用胶体金标记。同时抗志贺氏菌的兔多抗和驴抗鼠抗体(二抗)分别喷涂于硝酸纤维素膜作为检测线(T线)和质控线(C线),研制了志贺氏菌胶体金快速检测试纸条。结果显示试纸条的灵敏度为105mL-1,并只与两株志贺氏菌有阳性反应外,而与其它23株常见的细菌无交叉反应。同时在检测添加有阪崎肠杆菌和长双歧杆菌的牛奶样品中,结果显示试纸条的灵敏度为106mL-1。志贺氏菌免疫胶体金试纸条的建立,为加强食品中志贺氏菌的检测工作,建立一种快速、简便的筛查方法具有重要的意义。  相似文献   

19.
The increasing availability of relatively low cost, portable and sensitive A T P bioluminometers has prompted exploration for other applications of A T P bioluminescence in the dairy industry. A protocol for detecting antibiotic residues in raw milk by A T P bioluminescence is described which is less complex than similar procedures described previously. The traditional assay based on acid production is slower and less sensitive but still has a significant cost advantage.  相似文献   

20.
Taqman荧光实时PCR快速检测原料乳中EPEC   总被引:1,自引:0,他引:1  
建立可对原料乳中肠致病性大肠埃希氏菌(enteropathogenic Escherichia coli,EPEC)进行快速检测的Taqman光实时PCR方法.以eae致病基因为靶基因,用特异性引物和Taqman探针进行实时PCR扩增,研究反应的特异性和检测限,并用所建立的方法对16份市售原料乳进行EPEC检测.结果表明,所用引物和探针可高效扩增出目的片段,与原料乳中其他常见致病菌无交叉反应,经2 h增菌后检测限为8.8 mL-1.对16份市售原料乳样品,检出2份含有EPEC,血清型分别为O111:K58(B4)和O127a:K63(B18).全部检测过程只需5h,可用于原料乳中EPEC的快速检测和污染调查.  相似文献   

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