Multidimensional chromatography in food analysis

In this work, the main developments and applications of multidimensional chromatographic techniques in food analysis are reviewed. Different aspects related to the existing couplings involving chromatographic techniques are examined. These couplings include multidimensional GC, multidimensional LC, multidimensional SFC as well as all their possible combinations. Main advantages and drawbacks of each coupling are critically discussed and their key applications in food analysis described.     

基体溶液改进-原子荧光法测定食品中的汞

探讨改进基体溶液双道原子荧光光谱法测定食品样品中的汞。样品消解后用6mol/L盐酸、硫脲+抗坏血酸(50g/L)作为基体溶液进行仪器测定。本方法检出限0.051μg/g,最低检出质量浓度0.10μg/L,相对标准偏差为7.45%、6.76%,回收率为88.6%—113.2%。方法具稳定性好、灵敏度高、检出限低等优点。     

火焰原子吸收法测定吉林地区63种食物中锌铜铁的含量

用火焰原子吸收法对吉林地区６３种食物中锌、铜、铁的含量进行了测定。结果表明，肝、瘦肉及蛋黄中上述元素含量较多，植物性食物次之，而水果类含量甚微。在各种食物中这三种元素的含量呈正相关，加工精制的面粉会使其含量下降。     

火焰原子吸收法测定多种加工食品中的钙,镁和铁

本文研究了湿法灰化火焰原子吸收法测定多种加工食品中的钙、镁和铁。实验表明,氧化镧溶液的加入对测定钙、镁元素的干扰有较好的抑制作用。给出了钙、镁和铁校准曲线的线性回归方程及相关系数,其添加回收率分别为91.5%,100%,107.5%。相对标准偏差分别为2.8%,7.1%,3.2%。     

Printed electrochemical sensor for ascorbic acid determination

Simple, strip-type sensors based on 7,7,8,8-tetracyanoquinodimethane-modified graphite were prepared using screen printing techniques. The electrochemical strips operated at low potentials [50 mV at pH 7.0 or 100 mV at pH 4.8 vs. Ag/AgCl (printed)] and had a sensitivity of 3.5–7.1 μA 1 mmol^?1L-ascorbic acid. Determination of ascorbic acid concentration was achieved in 30 s and required samples of ca. 30 μl. The current output of the electrodes was found to be relatively insensitive to variations in pH over the range 5.0–8.5. Between 15 and 35 °C, the temperature coefficient was 2.7% °C^?1. The printed electrodes were suitable for single determinations but demonstrated adequate stability for periodic re-use. The ascorbic acid concentration in the juice of fresh fruit was determined using the electrochemical printed electrodes and a commercially available enzymatic test kit. Close agreement was observed between the two methods [r=0.9997 (n=12),slope=0.9798]. The limit of detection using the printed sensor for real samples was calculated as 4mg l^?1(22 μM).     

Investigations on adsorption potentiometry Part I. Derivative adsorption chronopotentiometry of the iron(III)-2-(5′-bromo-2′-pyridylazo)-5-diethylaminophenol system

An electroanalytical method, based on derivative chronopotentiometry of the iron complex with 2-(5′-bromo-2′- pyridylazo)-5-diethylaminophenol (5-Br-PADAP) accumulated adsorptively on the surface of a hanging mercury drop electrode, for determining trace iron in food has been developed. The dependences of the peak height on the dt/dE vs. E curve on the preconcentration time, preconcentration potential and electrode area are discussed. Optimum experimental conditions include 0.005 mol 1^?1 NH₃NH₄Cl, 2 × 10^?7 mol 1^?1 5-Br-PADAP and a preconcentration potential of ?0.40 V (vs. SCE). Under these conditions, the detection limit and the linear range are 2 × 10^?9 and 6.7 × 10^?9?1.7 × 10^?7 mol 1^?1, respectively. The relative standard error of the method is 1.5% for 6.7 × 10^?8 mol 1^?1 Fe(III). The method was applied to samples of microwave digested food.     

石墨炉原子吸收法测定食品中毒害元素铅

本文对光控ＧＦＡＡＳ测定食品中痕量铅进行了较深入的研究和探讨。并为国家食品标准所确证。     

Non-chromatographic screening procedure for arsenic speciation analysis in fish-based baby foods by using electrothermal atomic absorption spectrometry

A procedure for the speciation analysis of arsenic in fish-based baby foods is presented. Inorganic arsenic, methylarsonic acid (MA), dimethylarsinic acid (DMA) and arsenobetaine (AB) were determined by electrothermal atomic absorption spectrometry (ETAAS) using suspensions prepared in a 0.01 mol L⁻¹ tetramethylammonium hydroxide (TMAH) solution. Speciation is based on the use of three different chemically modified ETAAS atomizers to obtain the analytical signals. Using a palladium salt as the chemical modifier, the signal corresponding to the total arsenic concentration is obtained. When palladium is replaced by Ce(IV), the signal is solely due to inorganic arsenic (III and V) + MA. If no signal is obtained in this latter case, it is possible to distinguish between DMA and AB using a zirconium coated atomizer. The signal obtained in this way is due solely to DMA, and the concentration of AB can be obtained by the difference with the total arsenic content. Determinations by ETAAS require the use of the standard additions method. The limits of detection for the determination of AB, DMA and inorganic arsenic (+MA) are 15, 25 and 50 ng g⁻¹ expressed as arsenic, respectively. These detection limits are good enough for the procedure to be appropriate for the rapid determination of these compounds, avoiding extraction processes and/or chromatographic separations. Data for commercial samples, as well as for four standard reference materials, are given.     

Evaluation of a method based on liquid chromatography-diode array detector-tandem mass spectrometry for a rapid and comprehensive characterization of the fat-soluble vitamin and carotenoid profile of selected plant foods

The feasibility of using reversed-phase liquid chromatography/diode array/tandem mass spectrometry (LC-DAD-MS/MS) for a rapid and comprehensive profiling of fat soluble vitamins and pigments in some foods of plant origin (maize flour, green and golden kiwi) was evaluated. The instrumental approach was planned for obtaining two main outcomes within the same chromatographic run: (i) the quantitative analysis of ten target analytes, whose standards are commercially available; (ii) the screening of pigments occurring in the selected matrices. The quantitative analysis was performed simultaneously for four carotenoids (lutein, zeaxanthin, β-cryptoxanthin, and β-carotene) and six compounds with fat-soluble activity (α-tocopherol, δ-tocopherol, γ-tocopherol, ergocalciferol, phylloquinone and menaquinone-4), separated on a C30 reversed-phase column and detected by atmospheric pressure chemical ionization (APCI) tandem mass spectrometry, operating in Selected Reaction Monitoring (SRM) mode. Extraction procedure was based on matrix solid-phase dispersion with recoveries of all compounds under study exceeding 78 and 60% from maize flour and kiwi, respectively. The method intra-day precision ranged between 3 and 7%, while the inter-day one was below 12%. The mild isolation conditions precluded artefacts creation, such as cis-isomerization phenomena for carotenoids. During the quantitative LC-SRM determination of the ten target analytes, the identification power of the diode array detector joined to that of the triple quadrupole (QqQ) allowed the tentatively identification of several pigments (chlorophylls and carotenoids), without the aid of standards, on the basis of: (i) the UV-vis spectra recorded in the range of 200-700nm; (ii) the expected retention time; (iii) the two SRM transitions, chosen for the target carotenoids but also common to many of isomeric carotenoids occurring in the selected foods.     

VA-90氢化物发生-原子吸收光谱法测定食品中痕量铅

本文研究了用氢化物发生－原子吸收光谱法测定食品中痕量铅的方法。该法简便、快速,扩大了火焰原子吸收的分析范围,具有良好的精密度和准确度。测定结果的相对标准偏差为２．３９％,平均回收率为９２．４６％。