A simple and highly sensitive spectrophotometric determination of Cr(VI) in food samples by using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH)

A simple, rapid, sensitive and inexpensive method has been developed for the determination of trace amounts of chromium(VI) using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH). The metal ion gives a yellow coloured complex with 3,4-DHBINH in acetate buffer of pH 5.5 with 1:1 (metal:ligand) composition. The complex shows a maximum absorption at 400 nm. Beer’s law is obeyed in the range 0.5–7.7 ppm of Cr(VI). The molar absorptivity, Sandell’s sensitivity and detection limit were found to be 1.35 × 10⁴ L mol⁻¹ cm⁻¹, 0.0075 μg cm⁻² and 0.0045 μg mL⁻¹, respectively. The correlation co-efficient and regression co-efficient of the Cr(VI)–3,4-DHBINH complex were 0.99 and 0.12, respectively. Major cations and anions did not show any interference. The developed method has been successfully applied for the analysis of Cr(VI) in food samples (leafy vegetables), comparing the results simultaneously with those obtained using an Atomic Absorption Spectrophotometer, whereby the validity of the method has been tested.     

Simultaneous determination of trace amounts of vanadium and molybdenum in water and foodstuff samples using adsorptive cathodic stripping voltammetry

A new procedure is presented for the simultaneous determination of ultra trace amounts of vanadium and molybdenum based on adsorptive cathodic stripping voltammetry (AdCSV). Adsorptive accumulation of the V(V) and/or Mo(VI) with chromoxane cyanine R (CCR) onto a hanging mercury drop electrode, followed by reduction of the adsorbed species using differential pulse voltammetry method. Optimised conditions include a 60 s adsorption period at ?0.10 V, 8.0 μm of CCR in 0.1 m acetate buffer, pH 3.6, and a voltammetric scan using differential pulse mode with 25 mV s^?1 scan rate. Detection limits of 0.1 and 0.08 ng mL^?1 were achieved for V(V) and Mo(VI), respectively, which can be lowered down to 0.06 and 0.04 ng mL^?1 by extending the adsorption time to 180 s. The reduction currents are linear in the range of 0.3–24.0 ng mL^?1 and 0.1–30.0 ng mL^?1 for V(V) and Mo(VI), respectively. The relative standard deviation for ten replicates determination of 4.0 ng mL^?1 V(V) and Mo(VI) were 1.8% and 1.1%, respectively. The proposed method applied for the determination of vanadium and molybdenum in river water, tap water, well water and plant foodstuff such as cucumber, tomato, carrot and tea.     

Simultaneous and rapid determination of added phosphorus(V) compounds in meat samples by capillary isotachophoresis

One-dimensional capillary isotachophoretic method (CITP) for the simultaneous determination of added phosphorus(V) compounds (ortho-, pyro- and tripolyphosphates) in pork meat is described. The calibration curves were obtained for KH₂PO_4, K₄P₂O₇, Na₂H₂P₂O₇, Na₃P₃O_9, Na₅P₃O₁₀ resulting in linearity (R² = 0.9996, 0.9998, 0.9991, 0.9978 and 0.9994, respectively). Detection limits ranged from 0.4 mg P/L for potassium pyrophosphate (PP) to 1.1 mg P/L for trisodium trimetaphosphate (TTP) and quantification limits ranged from 1.2 mg P/L for PP to 3.7 mg P/L for TTP. The repeatabilities of within-day and between-days analysis were ≤2.27% and ≤4.89% for relative step height, respectively. The developed procedure was applied for added phosphates determination in meat samples. The minimal sample pretreatment and presented results make CITP an alternative to the existing methods of meat analysis.     

A Sensitive, Selective New Analytical Reagent, 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone for Extractive Spectrophotometric Determination of Mo(VI) in Food Samples

Synthesized a new reagent 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2, 6-DAPBPTSC) characterized and is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of molybdenum(VI) at pH 3.5 to form a yellowish orange colored 1:1 chelate complex. The absorbance was measured at a maximum wavelength, 500 nm. This method obeys Beer’s law in the concentration range 0.90–9.00 μg mL⁻¹ and the correlation coefficient of Mo(VI)–2,6-DAPBPTSC complex is 0.954, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 1.212 × 10⁴ L mol⁻¹cm⁻¹, 0.0079 μg cm⁻², respectively. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.894% and the detection limit value is 0.0056 μg mL⁻¹. The instability constant of the method has been calculated by Asmus’ method as 6.476 × 10^–5, at room temperature. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Mo(VI) in food and water samples. The validity of the present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which indicates the significance of the present method an inter comparison of the experimental values, using atomic absorption spectrometer.     

Solid‐phase extraction and spectrophotometric determination of Allura Red (E129) in foodstuff,soft drink,syrup and energy drink samples: a comparison study

Amberlite XAD‐7 and XAD‐8 resins were used as adsorbents for preconcentration and determination of Allura Red (AR) food dye in aqueous medium. The effects of pH, sample volume, sample and eluent flow rates on the extraction of AR were optimised. The determination of dye was performed at 506.0 nm using spectrophotometry. Interference effects of matrix ions and some dyes were also investigated under optimised conditions. The methods permitted low detection limits which were 1.2 and 0.6 μg L^?1 for XAD‐7 and XAD‐8, respectively. Adsorption behaviours were investigated by adsorption isotherms and zero charge pH experiments. Validations of the method were performed by determination of AR contents in some foodstuffs. AR contents of liquid samples were found between 58 and 440 μg mL^?1. AR concentrations of solid samples were between 416 and 432 μg g^?1. The XAD‐7 and XAD‐8 resins presented a fast and reliable potential to determine AR dye in real samples.     

超高效液相色谱法同时快速测定多种动物源食品中9种生物胺的含量

目的建立超高效液相色谱(ultra performance liquid chromatography,UPLC)同时测定动物源性食品中色胺、苯乙胺、腐胺、尸胺、组胺、章鱼胺、酪胺、亚精胺、精胺等9种生物胺的含量。方法样品经高氯酸溶液提取,丹磺酰氯柱前衍生化,加入氨水终止反应,乙腈定容。采用Acquity UPLC BEH C_(18)(2.1mm×100 mm,1.7μm)色谱柱,以5 mmol/L乙酸铵和乙腈作为流动相进行梯度洗脱,流速为0.4 mL/min,采用二极管阵列检测器在波长254 nm下检测。结果 9种生物胺在0.1~20μg/mL的范围内呈现良好的线性关系(r0.999)。样品在20、50和100 mg/kg 3个浓度水平的加标回收率为75.6%~97.2%,相对标准偏差为0.12%~5.32%(n=6);9种生物胺的方法定量限均为10 mg/kg。结论该方法简便、快捷、准确,可以用于动物源性食品中9种生物胺的同时测定。     

黑曲霉菌丝体-壳聚糖的制备及对Cr(Ⅵ)的吸附性能研究

研究了黑曲霉菌丝体-壳聚糖对Cr(Ⅵ)的吸附特性。以废弃黑曲霉菌丝体、壳聚糖作为吸附剂制备原料,采用环氧氯丙烷进行交联,三聚磷酸钠进行固化,制备成黑曲霉菌丝体-壳聚糖复合型吸附剂。探究了pH值、黑曲霉菌丝体-壳聚糖的投加量对Cr(Ⅵ)的吸附影响。实验结果表明,黑曲霉菌丝体-壳聚糖的用量为0.5 g时对Cr(Ⅵ)吸附率最高达到92.30%,pH=6时对Cr(Ⅵ)吸附率最高达84.32%。动力学数据分析表明黑曲霉菌丝体-壳聚糖生物吸附剂对Cr(Ⅵ)的吸附过程符合准二级动力学模型(R2=1)。同时该吸附过程符合Freundlich等温线模型,最大吸附量为108.23mg/g;扫描电镜和红外光谱证实吸附反应发生吸附剂的颗粒表层,主要活性基团为-OH,-COOH。上述结果表明,黑曲霉菌丝体-壳聚糖对Cr(Ⅵ)吸附性能良好,绿色环保,应用前景广泛。     

石墨化碳黑净化-分光光度法测定明胶空心胶囊中的六价铬

目的建立石墨化碳黑净化-二苯碳酰二肼衍生-分光光度法测定着色明胶空心胶囊中六价铬的含量。方法样品经磷酸盐缓冲液Ⅰ提取,80℃水浴振荡1 h,碱性条件下用石墨化碳黑脱除色素,二苯碳酰二肼丙酮溶液酸性条件下衍生显色,10 mm石英比色皿比色,采用分光光度法在540 nm波长下检测,扣除本底后以外标法定量。结果 50 mg石墨化碳黑粉末(graphitized carbon black,GCB)对于明胶空心胶囊的着色剂具有较好的脱除效果,GCB在待净化液pH大于12.5的条件下对Cr(Ⅵ)的吸附作用不明显,回收率可达90%以上。样品中Cr(Ⅲ)的存在对于本方法测定Cr(Ⅵ)无显著影响。根据使用的比色皿光程,方法检出限为1.6 mg/kg或更低。结论本方法快速准确,适用于明胶空心胶囊中六价铬的检测。     

印染废水中聚乙烯醇浆料的高效去除及六价铬的协同还原

聚乙烯醇(PVA)是印染废水有机污染物的主要来源,同时含铬显影剂的使用导致部分印染废水含有六价铬(Cr(Ⅵ)),高浓度PVA及高毒性Cr(Ⅵ)的协同处理技术亟待突破。利用过硫酸盐热活化可引发聚合物发生自由基交联反应的特点,研究印染废水中PVA及Cr(Ⅵ)协同处理的方法。考察了过硫酸盐投加量、反应温度、初始pH值、Cr(Ⅵ)初始浓度等因素对二者去除效率的影响,借助X射线光电子能谱、凝胶渗透色谱等手段分析了反应沉淀物及剩余废水中残留物,探索了PVA及Cr(Ⅵ)的协同处理机制。结果表明：当过硫酸盐质量浓度为8.0 g/L、反应温度为70℃、废水pH值小于6时,模拟印染废水的化学需氧量去除率达91.9%,PVA去除率可达98.0%,Cr(Ⅵ)还原率为94.3%;过硫酸盐热活化引发PVA自由基交联及PVA的还原性是PVA高效沉淀及Cr(Ⅵ)有效还原的主要原因,此类浆料与重金属污染物的协同处理在印染废水方面具有一定的应用前景。     

Optimization of microwave-assisted extraction with saponification (MAES) for the determination of polybrominated flame retardants in aquaculture samples

The efficiency of microwave-assisted extraction with saponification (MAES) for the determination of seven polybrominated flame retardants (polybrominated biphenyls, PBBs; and polybrominated diphenyl ethers, PBDEs) in aquaculture samples is described and compared with microwave-assisted extraction (MAE). Chemometric techniques based on experimental designs and desirability functions were used for simultaneous optimization of the operational parameters used in both MAES and MAE processes. Application of MAES to this group of contaminants in aquaculture samples, which had not been previously applied to this type of analytes, was shown to be superior to MAE in terms of extraction efficiency, extraction time and lipid content extracted from complex matrices (0.7% as against 18.0% for MAE extracts). PBBs and PBDEs were determined by gas chromatography with micro-electron capture detection (GC-μECD). The quantification limits for the analytes were 40–750 pg g^?1 (except for BB-15, which was 1.43 ng g^?1). Precision for MAES-GC-μECD (%RSD?<?11%) was significantly better than for MAE-GC-μECD (%RSD?<?20%). The accuracy of both optimized methods was satisfactorily demonstrated by analysis of appropriate certified reference material (CRM), WMF-01.     

柳絮纤维生物质炭的制备及其对染料废液中Cr(Ⅵ)的吸附性能

针对目前酸性媒染染料废水中的六价铬Cr(VI)对水体环境污染严重的问题,以柳絮纤维为原料,通过限氧裂解法制备了KOH活化生物质炭(CBK)、NaOH活化生物质炭(CBN),采用吸附批实验法研究模拟染料废液pH值、吸附剂投放量、温度效应等对柳絮纤维生物质炭吸附处理Cr(VI)的影响,利用动力学和热力学相关模型对吸附过程进行拟合,探究柳絮纤维生物质炭对Cr(VI)的吸附机制。结果表明:CBK较CBN比表面积显著增大,表面吸附位点增多;在模拟废液pH值为2时,CBK、CBN对Cr(VI)的理论最大吸附量分别为82.68、47.16 mg/g,且吸附过程符合Freundlich热力学模型和准二级动力学模型,吸附过程主要为多分子层吸附,同时还伴随着化学吸附,该吸附反应是自发进行且为吸热反应,温度升高可显著提高柳絮纤维生物质炭对Cr(VI)的吸附量。     

Analytical applications of 2,6-diacetylpyridine bis-4-phenyl-3-thiosemicarbazone and determination of Cu(II) in food samples

New synthesized reagent 2,6-diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2,6-DAPBPTSC) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of copper(II) at pH 3.0 to form a yellowish orange colored 1:1 chelate complex. The maximum absorbance was measured at 370 nm. This method obeys Beer’s law in the concentration range 0.63–6.30 g ml⁻¹ and the correlation coefficient of Cu(II)–2,6-DAPBPTSC complex is 0.942, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 0.847 × 10⁴ l mol⁻¹ cm⁻¹ and 0.0075 g cm⁻², respectively. The instability constant of complex calculated from Asmus′ method is 1.415 × 10⁻⁴ at room temperature. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.777% and the detection limit value is 0.0056 g ml⁻¹. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Cu(II) in food samples. The performance of present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which is indicates the significance of present method is an inter comparison of the experimental values, using atomic absorption spectrometer (AAS).     

Optimisation of microwave assisted extraction (MAE) for polycyclic aromatic hydrocarbon (PAH) determination in smoked meat

A rapid extraction method involving microwave assisted extraction (MAE), followed by sample clean-up on a silica cartridge, reversed-phase high performance liquid chromatography (RP-HPLC) and spectrofluorimetric detection, was optimised for polycyclic aromatic hydrocarbon (PAH) determination in smoked meat. Compared to solvent extraction assisted by sonication, MAE, carried out with n-hexane on 2g of lyophilised sample at 115°C for 15min, allowed to obtain better extraction efficiencies. Limits of quantification (LOQ, s/n=10) lower than 0.2μg/kg wet weight were found for all PAHs, except for Fl (0.3μg/kg), P (0.6μg/kg) and IP (0.4μg/kg). The optimised procedure, that presented good analytical performances (with recoveries ranging from 77% to 103%, and precision within 10% for most of the PAHs), was applied to determine PAH content in different smoked meat products from the Italian market.     

真空气流细胞破壁技术对橄榄总黄酮提取的影响

以橄榄为原料,通过单因素及Box-Benhnken中心组合法研究橄榄切片厚度、质构保护液浓度及真空气流细胞破壁技术（VAPB）对橄榄总黄酮提取率及破果率的影响。结果表明,切片橄榄最适宜厚度为4⁵ mm;质构保护最佳处理工艺为:首先在浓度为0.20 g/100 m L的海藻酸钠溶液中浸泡20 min,接着在浓度为0.15 g/100 m L的氯化钙溶液中浸泡60 min;真空气流细胞破壁前处理最佳工艺为:泄压温度110℃、压力差122 k Pa、停滞时间16 min、泄压重复次数3次;最后采用亚临界水提取,其总黄酮提取率为64.93%,破果率20.60%,相比切片后直接进行亚临界水提取对照组,总黄酮提取率提高了21.23%,而破果率仅增加了3.89%。提取过总黄酮的橄榄切片79.40%结构保持完整,可以作为广式凉果原料。      

Dilute-and-shoot procedure for the determination of mineral constituents in vinegar samples by axially viewed inductively coupled plasma optical emission spectrometry (ICP OES)

Samples of commercial wine vinegar were introduced in an axially viewed inductively coupled plasma optical emission spectrometry instrument (AX-ICP OES) equipped with different sample introduction systems: a cross-flow nebulizer combined with a double-path spray chamber (CF-DP) and cone spray associated with a cyclone spray chamber (CS-CC). Samples of white and red wine vinegar were diluted with water before analysis. Higher magnesium Mg II/Mg I ratios (11 and 10 for CS-CC and CF-DP, respectively) were obtained using a nebulization gas flow rate of 0.6 l min^-1 and an applied power of 1.3 kW. The background equivalent concentrations (BEC) and signal-to-background ratio (SBR) of analytes were improved using scandium (Sc) as the internal standard. The limits of detection (LOD) and limits of quantification (LOQ) for mineral constituents were similar for both introduction systems. Best recoveries values were obtained using a plasma under robust conditions, CS-CC system and Sc as the internal standard. The concentration determined in 13 commercial samples of wine vinegars varied between 0.2 and 3.0, between 0.02 and 0.4, between 8.5 and 100.0, between 0.01 and 0.05, between 27.0 and 540.0, between 4.0 and 79.0, between 0.4 and 10.0, and between 0.01 and 2.0 for aluminium (Al), barium (Ba), calcium (Ca), copper (Cu), potassium (K), magnesium (Mg), manganese (Mn), and zinc (Zn), respectively.     

成革中Cr(Ⅵ)的测定及影响因素

使用国际标准的DIN53314方法测定成革中的Cr(Ⅵ)，讨论了成革中Cr(Ⅲ)转化为Cr(Ⅵ)的基本原理。从加热、光照和浸汗时间观察了对成革中Cr(Ⅵ)含量的影响，并阐述了可能的原因。结果表明加热、浸汗和光照对六价铬含量都有影响，光照的干扰最大。     

Chemical analysis of French beans (Phaseolus vulgaris L.) by headspace solid phase microextraction (HS-SPME) and simultaneous distillation/extraction (SDE)

Headspace Solid Phase Microextraction (HS-SPME) involving divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre and simultaneous distillation/extraction (SDE) techniques were applied to study the volatile and semi volatile compounds of thawed and cooked Phaseolus vulgaris L. A total of 104 compounds were detected by GC and GC/MS. Thereof, 76 compounds were identified for the first time in this species. The major differences between HS-SPME and SDE were found in the content of identified alcohols (23.62% SDE versus 62.20% SPME), terpenoids (39.15% SDE versus 2.45% SPME), heterocyclic compounds (13.78% SDE versus 1.21% SPME), hydrocarbons (2.22% SDE versus 13.87% SPME) and esters (0.98% SDE versus 12.98% SPME). The SPME technique was found to be useful for rapid and routine quality controls of thawed French beans, while SDE is favourable to study the entire set of flavour volatiles in the corresponding cooked samples.     

分散式固相萃取结合高效液相色谱法测定植物油中苯并(a)芘含量的不确定度分析

目的建立适用于分散式固相萃取结合高效液相色谱法测定植物油中苯并(a)芘含量的不确定度分析方法。方法样品用正己烷稀释后,加入适量吸附剂和去离子水,经分散式固相萃取净化,浓缩定容后应用Eclipse XDB-C18色谱柱(4.6 mm×150 mm,5μm)对苯并(a)芘含量进行分析,流动相以乙腈-水(v:v=88:12)进行等度洗脱,采用荧光检测器(激发波长Ex=384 nm,发射波长Em=406 nm)检测,外标法定量。依据JJF 1135-2005《化学分析测量不确定度评定》中相关规定,考查称量、定容体积、标准曲线、仪器测量重复性和回收率等引入不确定度的主要因素,并对不确定度的各分量进行计算和合成。结果当植物油中苯并(a)芘含量为4.33μg/kg时,在95%的置信区间下,其扩展不确定度为0.66μg/kg(k=2)。评定结果表明,标准曲线拟合和标准溶液的配置产生的不确定度对合成不确定度的影响较大,而样品称量所引入的不确定度较小可忽略不计。结论该评定方法客观准确,适用于分散式固相萃取结合高效液相色谱法测定植物油中苯并(a)芘含量的不确定度分析,对检测结果准确度的提高具有参考意义。