Raman spectroscopic determination of norbixin and tartrazine in sugar

In this paper, a method for the detection of norbixin and tartrazine in sugar by means of resonance Raman spectroscopy is presented. The extraction was done in four steps using methanol and the measurements were performed in aqueous solution. The excitation wavelength was 514?nm for norbixin and 488?nm for tartrazine samples. The characteristic resonance Raman signals of the dyes were fitted by different functions. Depending on the R ² values of the different fits, each spectrum was classified as positive or negative response. A detection limit of 250?ng?g^?1 for norbixin and 989?ng?g^?1 for tartrazine in solid sugar samples could be reached by logistic regression.     

自动电位滴定法测定钙片中钙含量的不确定度评定

目的评估自动电位滴定法测定钙片中钙含量的不确定度。方法对自动电位滴定法测定钙片中钙含量的全过程进行分析,建立数学模型,分析各不确定度分量。根据JJF 1059.1-2012《测量不确定度评定与表示》对各个不确定度分量进行评估,计算扩展不确定度。结果自动电位滴定法测定某品牌钙片中钙含量为(17.85±0.17) g/100 g, k=2。结论该方法不确定度较低,结果可靠。     

电位滴定法测定槟榔中游离碱度的不确定度评定

目的对电位滴定法测定槟榔中游离碱度含量进行不确定度评定。方法建立影响槟榔中游离碱度测量结果的数学模型,并对电位滴定法测量槟榔中游离碱度的测量结果进行不确定度评定。结果样品槟榔中游离碱度含量为6.5 mg/g时,测定结果的合成标准不确定度为0.065 mg/g,扩展不确定度为0.13 mg/g。结论DB43/132-2004《食用槟榔》标准方法测定槟榔中游离碱度不确定度的最主要来源是盐酸标准滴定溶液体积引入的不确定度,因此在实验过程中应该严格控制滴定终点,确保实验结果准确可靠。     

Application of an enzyme immunoassay for the quantitative determination of azo dye (Orange II) in food products

This paper reports the preparation of polyclonal antibodies against a synthetic azo dye, Orange II, and the development of an indirect ELISA to detect Orange II in foods. The sulfonic group of Orange II was modified and linked with carrier protein to synthesise an artificial antigen. Based on the checkerboard titration, the method showed excellent sensitivity (IC₅₀?=?0.61 ng?g^?1) to Orange II in the linear range of 0.05–10?ng?g^?1. The antibody had little cross-reactivity with Chromotrope FB, Gardenia Yellow, Ponceau 4R, Sunset Yellow and Sudan dyes. The ELISA had limits of detection (LOD) of 0.22, 0.97 and 0.74?ng?g^?1 in chilli powder, chilli oil and braised pork, respectively. The limits of quantification (LOQ) of the assay were 0.91?ng?g^?1 in chilli powder, 1.48?ng?g^?1 in chilli oil and 1.10?ng?g^?1 in braised pork. For food products fortified with 1–10?ng?g^?1 Orange II, the inter- and intra-assay variations were all less than 24.0% and 18.0%, respectively. Therefore, the proposed test could be used as a rapid screening method for Orange II detection in food samples.     

Electrochemical determination of theophylline in foodstuff,tea and soft drinks based on urchin-like CdSe microparticles modified glassy carbon electrode

A simply electrochemical method based on CdSe microparticles modified glassy carbon electrode (GCE) was developed to determine theophylline using cyclic voltammetry and differential pulse voltammetry. Theophylline showed a well-defined oxidation peak at the fabricated electrode in phosphate buffer solution and the oxidation peak current is much higher than that at the bare GCE, indicating that CdSe can effectively improve the oxidation of theophylline. Several effect factors on theophylline determination were optimised, such as CdSe amount, solution pH, scan rate and accumulation time. Under the optimal conditions, the oxidation peak current of theophylline was proportional to its concentration in the range of 1.0–40 and 40–700 μM with a correlation coefficient of 0.9974 and 0.9956, respectively. The limit of detection was estimated to be 0.4 μM (S/N = 3). The developed method showed good reproducibility and excellent selectivity. The fabricated electrode was successfully used to determine theophylline in tea, carbonated cola drink, fruit juice drink, fermented milk drink and preserved fruit with acceptable recovery.     

A novel sensitive electrochemical method for the detection of ractopamine in meat food via polycitrulline-modified electrode

ABSTRACT

In this paper we report the modification with citrulline of the surface of a glassy carbon electrode (GCE) through cyclic voltammetry to prepare a polycitrulline-modified electrode (PCit/GCE). The electrochemical behaviour of ractopamine on this PCit/GCE was then investigated by cyclic voltammetry, to establish a novel electrochemical method for the detection of ractopamine residues in animal tissue. The optimum preparation conditions for the modified electrode were found to include a polymerisation solution pH of 6.8. The cyclic voltammetry required 12 scan cycles at a scan rate of 40 mV/s with a potential range of ?1.6 to 2.3 V. The optimum conditions to determine ractopamine were in a solution of pH 6.0 with cyclic voltammetry performed at a scan rate of 60 mV/s and a potential range of 0.4 to 1.0 V. To analyse meat, the tissue sample was extracted with ethanol, filtered, evaporated to dryness and diluted with phosphate buffered saline at pH of 6.0 before being analysed in the electrochemical cell. The limit of detection of the new method for ractopamine was 1.0 ng/g and the correlation coefficient (R) was 0.9991 in the concentration range of 140–5410 ng/g. Ractopamine residue levels in spiked beef and mutton samples were detected by the modified electrode and the recovery was in the range of 96%-101%, giving results consistent with a validated HPLC method. This study provides a new method for detection and quantification of ractopamine residues in animal tissue.     

亮橙色荧光碳点探针快速检测水产品中孔雀石绿

摘 要：目的 建立以亮橙色荧光碳点（bright orange fluorescent carbon dots, BO-CNDs）为探针的荧光检测法快速灵敏测定水产品中的孔雀石绿（malachite green,MG）。方法 对工作参数进行优化后,研究该检测方法的线性范围、灵敏度、选择性及抗干扰性,探究BO-CNDs和MG之间的相互作用,进而提出MG对BO-CNDs荧光猝灭的机制,最终将该方法应用到水产品中MG含量的测定。结果 在最佳检测条件下,BO-CNDs对MG检测的线性范围为0.01~10.00 μmol/L,检测限低至4.23 nmol/L,表现出反应快、选择性好、灵敏度高的优势。MG对BO-CNDs的荧光猝灭是内滤效应（inner filter effect, IFE）和动态猝灭协同作用的结果。最终将该检测方法应用于白鲢鱼、黑鱼、武昌鱼、鲤鱼、草鱼等鱼类样品中MG含量的测定,回收率在96.00%~102.00%之间,相对标准偏差(relative standard deviations, RSDs)低于1.01%。结论 该方法检测限低、灵敏度高、准确性好,具有应用于水产品中MG快速检测的巨大潜力。     

Development of antipeptide enzyme‐linked immunosorbent assay for determination of gelatin in confectionery products

The gelatin sources have become a controversial issue with regard to religious and health concern. Thus, the aims of this study were to develop and evaluate the efficiency of polyclonal antibodies against peptide immunogen of collagen α2 (I) chain for determination of gelatin sources in confectionery products by competitive indirect enzyme‐linked immunosorbent assay (ELISA). Collagen α2 (I) chain protein showed resistance against heat treatment and detectable in certain commercial products when analysed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS‐PAGE). The established ELISA exhibited low cross‐reactivity to fish and chicken gelatin. The IC₅₀ value was 0.39 μg mL^?1, and the limit of detection (IC₁₀) was 0.05 μg mL^?1. There were no false‐positive results from forty‐eight commercially processed products. The present method is useful for determination of gelatin in confectionery products.     

Development and single-laboratory validation of an HPLC method for the determination of cyclamate sweetener in foodstuffs

A method for the determination of cyclamate has been developed and single-laboratory validated for a range of foodstuffs including carbonated and fruit-juice drinks, fruit preserves, spreads, and dairy desserts. The method uses the peroxide oxidation of cyclamate to cyclohexylamine followed by derivatization with trinitrobenzenesulfonic acid and analysis by a modified reversed-phase high-performance liquid chromatography-ultraviolet light (HPLC-UV). Cycloheptylamine is used as an internal standard. The limits of detection were in the range 1–20 mg kg^?1 and the analysis was linear up to 1300 mg kg^?1 cyclamic acid in foods and up to 67 mg l^?1 in beverages. Analytical recovery was between 82% and 123%, and results were recovery corrected. Precision was within experimentally predicted levels for all of the matrices tested and Horrat values for the combined standard uncertainty associated with the measurement of cyclamate between 0.4 (water-based drinks) and 1.7 (spreads). The method was used successfully to test three soft drink samples for homogeneity before analytical performance assessment. The method is recommended for use in monitoring compliance and for formal testing by collaborative trial.     

Development of a new method for determination of exopolysaccharide quantity in fermented milk products and its application in technology of kefir production

An easy-to-use method for quantitative analysis of bacterial exopolysaccharides (EPS) was developed. The acid treatment was resultant in removing proteins and lactose and allowed to avoid long-term operation as dialysis. It was shown that, as opposed to anthron and phenol–sulphuric acid methods, reducing sugars method after EPS hydrolysis with glucose as standard provided reliable results, no matter to the EPS monosaccharide composition.     

A novel nanosensor based on Pt:Co nanoalloy ionic liquid carbon paste electrode for voltammetric determination of vitamin B9 in food samples

In this work we describe a novel nanoalloy (Pt:Co) room temperature ionic liquid (RTIL) modified carbon paste electrode as a high sensitive sensor for voltammetric determination of vitamin B₉ in food samples. The sensor exhibits an enhanced effectiveness for the electro-oxidation of vitamin B₉ in aqueous solution. The oxidation peak potential for this matter at a surface of the ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) Pt:Co carbon paste electrode (Pt:Co/IL/CPE) appeared at 685 mV that was about 110 mV lower than the oxidation peak potential at the surface of the traditional carbon paste electrode (CPE) under similar condition. The mechanism of the electro-oxidation process on the surface of the modified electrode was analyzed. Square wave voltammetry (SWV) was applied as a very sensitive electrochemical method for the determination of sub-micro-molar amounts of vitamin B₉. The linear response range and detection limit were found to be 1.0 × 10⁻⁷ to 5.0 × 10⁻⁴ M and 4.0 × 10⁻⁸ M, respectively. The prepared modified electrode shows several advantages such as simple preparation method, high stability, high sensitivity, and excellent catalytic activity, long-term stability and remarkable voltammetric reproducibility for eletrooxidation of vitamin B₉. The proposed sensor was successfully applied for the determination of vitamin B₉ in food samples.     

玉米及其制品和小麦及其制品中白僵菌素和恩镰孢菌素的高效液相色谱-串联质谱检测方法的建立

目的建立了玉米及其制品和小麦及其制品中白僵菌素(beauvericin,BEA)、恩镰孢菌素A(enniatin A,ENA)、恩镰孢菌素A_1(enniatin A_1,ENA_1)、恩镰孢菌素B(enniatin B,ENB)和恩镰孢菌素B_1(enniatin B_1,ENB_1)的高效液相色谱-串联质谱检测方法。方法样品经乙腈-水(85∶15,V/V)提取、室温静置、固相萃取柱净化后,以2 mmol/L乙酸铵水-乙腈作为流动相,采用电喷雾电离正离子多反应监测模式进行检测。结果该方法对玉米及其制品和小麦及其制品中BEA和4种恩镰孢菌素(ENNs)的检出限范围分别为0.01~0.12和0.02~0.21μg/kg,定量限范围分别为0.02~0.44和0.05~0.68μg/kg,平均加标回收率范围分别为91.6%~149.7%和100.5%~128.2%,基质抑制或增强效应分别为88.0%~101.5%和55.8%~106.5%,且BEA和4种ENNs在所测基质中线性关系和精密度良好,相关系数均0.99,相对标准偏差均15%。结论所建立的方法操作简便、灵敏度高、准确性好,可用于玉米及其制品和小麦及其制品中BEA和4种ENNs的测定。