茶叶中铅含量分析方法研究

研究分光光度法测定茶叶中铅含量的方法。显色剂4-（2-吡啶偶氮）-间苯二酚（PAR）与铅反应形成二元络合物。结果显示,铅含量在0．0mol／L～2．8×10^-5mol／L范围内,符合朗伯比耳定律,方法的表观摩尔吸光系数为3．26×10^4L／（mol·cm）,相关系数r为0．9983,精密度（RsD）小于2．2％,检出限为1．1mg／L,加标回收率在94．9％～104．2％之间,符合分析要求。     

离子色谱法测定饮用水中的8种阴离子

利用MIC型离子色谱仪,对饮用水中F^-、Cl^-、NO2^-、NO3^-、P04^3-和SO4^2-阴离子进行检测。采用Supp5-4．0mm＊150mm离子色谱柱,3．2mol/L碳酸钠和1．0mol／L碳酸氢钠淋洗液,抑制型电导检测。结果表明,利用这个离子色谱的最佳条件可以对饮用水中的8种阴离子同时准确快速地定性定量检测。F^-、HCOO^-、Cl^-、NO2^-、Br^-、NO3^-、PO4^3-和SO4^2-的相对标准偏差为：1．588％-3．270％,检出限为：0．012mg／L-5．076mg／L,回收率为：94．0％～105．2％。实验结果发现有水样中的F含量超出国家标准。     

微波程序消解-流动注射化学发光法快速测定彩色小麦中的微量铬

为了建立一种快速测定小麦中微量铬的新方法,以南阳彩色小麦粉为样品,经微波程序消解后,用亚硫酸将高价铬还原为Cr3＋,利用Cr3＋对Lumin01．H202化学发光体系的线性催化作用测定南阳彩色小麦中的总铬含量。结果表明：样品中的铬含量为2．211～6．088mg／kg,线性相关系数r=-0．9988,对5．0×10^-8mol／L Cr3＋测定的RSD为4．5％（n=11）,按3倍标准偏差（3S）计算的检出限为3．75×10^-11mol／L,灰麦加标回收率为93．66％~99．09％。该法快速简便、灵敏度高、选择性好,用于彩色小麦中微量铬的测定,结果令人满意。     

冻藏时间对速冻水饺品质影响的试验研究

主要考查冷冻保藏时间对于速冻水饺的理化性质、微生物指标及感官性状的影响。结果表明,随保藏时间延长,饺皮的水分含量呈线性规律下降,从最初的（37．25±0．44）％降至试验末期的（32．5±0．92）％。而对于样品的酸价,随保藏时间延长,酸价升高,从初始的（2．01±0．01）mg KOH／g升至试验末期的（2．38±0．02）mgKOH／g。菌落总数及嗜冷菌菌落总数结果相似,都随保藏时间延长而增加,菌落总数从（1．27±0．09）×10^5 cfu／g升至（3．26±0．08）×10^5 cfu／g,而嗜冷菌菌落总数从（2．44±0．06）×10^5 cfu／g升至（3．73±0．15）×10^5 cfu／g。结合对水饺饺皮和饺馅的感官评价表明,速冻水饺的食用品质随保藏时间呈下降趋势,相对来讲,保藏时间越短,样品的食用品质越好。     

微波消解-浓度直读法快速测定食品中的蛋白质

为建立一种快速测定食品中蛋白质的新型分析方法,选择小麦为样品,用微波程序压力消解技术进行处理,用氨气敏电极一浓度直读法直接读取数据,快速测定了小麦中的蛋白质。结果表明：粗蛋白质含量在12．56％～14．19％之间,RSD为1．4％～3．2％（n=5）,加标回收率为97．16％～104．7％,线性范围为1×10^-5～1×10^-2mol／L,相关系数为0．9991,检出下限为：1．4682μmol／L。分析结果与国标法对照无显著性差异。该法具有简便、灵敏、快速、准确、直观、无需蒸馏和滴定操作等显著优点,结果令人满意。     

不同多糖对玉米醇溶蛋白膜性质的影响

利用差示扫描量热仪（DSC）测定玉米醇溶蛋白溶液与多糖混合溶液的变性温度范围为80℃-95℃,在玉米醇溶蛋白和山梨醇体系中加入不同的多糖后（果胶、玉米淀粉、魔芋精粉、羧甲基纤维素和阿拉伯胶）测定膜性质,结果表明添加果胶的效果最好,加入果胶的膜透水率为0．760×10^-4kg·mm／（kPa·h·m^2）,拉伸强度为23．5×10^-5N／m^2。     

含酯基位阻季铵盐阳离子表面活性剂的合成

以十二烷基二甲基叔胺与环氧氯丙烷为原料,合成中间体（2,3-环氧丙基）十二烷基二甲基氯化铵,再进一步合成含酯基位阻季铵盐阳离子表面活性剂（2-羟基-3-月桂酰氧基丙基）十二烷基二甲基氯化铵,研究合成工艺,优化反应条件。目的产物经FTIR、^1HNMR、^13CNMR进行结构签定,测得产物的cmc为8．91×10^-4mol／L及γcmc为34．12mN／m,证明所合成的含酯基位阻季铵盐阳离子表面活性剂具有较高的表面活性。     

牛乳中有机磷农药残留分析方法

将农药残留的气相色谱测定方法开发应用于基质较为复杂的牛乳中，应用丙酮、乙腈（体积比1：4）的混合溶剂提取，离心，收集并浓缩处理样品。此方法的检出限在0．006mg／kg到0．17mg／kg的范围内。牛奶中加标有0．2×10^-6,0．4×10^-6,0．6×10^-6mg／kg三个浓度水平，回收率为87．86％～113．77％；标准偏差〈7％。可以应用此方法监控牛乳样品中有机磷农药残留情况。     

端视ICP-AES测定蜂产品中重金属有害元素残留

采用微波消解-端视等离子体发射光谱（ICP—AES）测定蜂产品中重金属微量元素铅、镉、砷，并对ICP—AES工作参数及条件进行了优化和选择，Pb、cd、As的检出限分别为2．9×10^-3mg／L、0．056×10^-3mg／L、5．2×10^-3mg／L，线性范围为0-500μg/L，相对标准偏差范围为2．9％-8．5％；回收率范围为91％-102％。该方法与国标法比较，结果无显著性差异，能满足蜂产品测定要求。     

卷烟纸中钾含量的快速检测

目的：为卷烟厂车间提供一种简单、快速测定卷烟纸中钾含量的方法。方法：采用离子选择性电极法,比较卷烟纸样品的预处理方法,比较钾离子选择电极在不同缓冲溶液中的电位响应行为。结果：钾离子选择电极在醋酸锂缓冲溶液(0.1 mol/L,pH 7.0)中具有优异的响应性能,对K+的线性响应范围为1.0×10-5~1.0×10-2mol/L,线性响应斜率为55.79 mV/dec (25 ℃),检测下限可达到2.14×10-6mol/L。钾离子选择性电极对卷烟纸样品的日内测试平均相对标准偏差为0.55%,日间测试相对标准偏差为2.8%,均＜5%。电极方法与离子色谱法的测试结果一致,平均相对偏差为4.1%(n=10),回收率为95.0%~101.9%,在连续1周的测试过程中展示出良好的时效性。结论：卷烟纸样品预处理方法中,采用1%稀醋酸超声萃取30 min提取钾离子快速简单,环保易行,离子选择性电极法准确可靠,适用于卷烟纸中钾含量的快速检测。     

A novel potentiometric pH electrode based on sulfated natural Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and analytical application in food samples

A novel solid state potentiometric pH electrode based on sulfated natural Fe₃O₄ silicone was fabricated. The optimum potentiometric performances such as Nernstian response, response time, selectivity, life-time and reproducibility of pH electrodes were investigated by using a computer-controlled potentiometric device. Moreover, the potentiometric performance of the solid state pH electrodes was studied with different mixtures sulfated natural Fe₃O₄, silicone and graphite powder. The best potentiometric behavior of proposed pH electrode was obtained with a composition of 20% (w/w) sulfated natural Fe₃O₄, 40% (w/w) graphite powder and 40% (w/w) silicone. The sub-Nernstian response for pH electrode was exhibited with a slope of 30.8?±?1.4 mV/pH (r?=?0.9963) from pH 2 to pH 12. In addition, the dynamic response time was found as 10 s in acidic medium and further the proposed pH electrode can be used for at least 1 year without any significant slope of the pH–potential curve. The selectivity coefficient of pH electrode was interpreted according to fixed interference method in the presences of Na⁺, Li⁺, K⁺, NH₄⁺, SO₄^2?, CH₃COO^? and NO₃^? ions. The reproducibility of pH electrode was calculated in pH 4 and pH 6 phosphate buffers and it was found as 0.24 RSD (%) and 0.27 RSD (%) respectively. The proposed pH electrode was used to determine of pH in acid?bases titration compared with glass pH electrode and is highly stable in corrosive systems including HF solution. Terminally, the pH value was successfully determined in some soft drinks and milk samples by proposed solid state pH electrode at 95% confidence level with satisfactory agreement compared with glass pH electrode.     

极谱络合吸附波法测定微量镍的研究

在pH5.8的0.4mol/L(CH2)6N4-HCl缓冲溶液中,镍与3-噻唑偶氮-5-氨基苯酚络合物有一灵敏的络合吸附波,其峰电位在-0.44V(vs.SCE)。该波的二阶导数峰峰电流与镍浓度在0.05～5.00mg/L范围内呈线性关系(r=0.9992,n=10)。检出限为0.02mg/L。本方法回收率在95.2%～106.5%之间。经多种电化学方法证明该波为络合物吸附波,其电极过程为不可逆过程,电子转移数为2。此外还实验了多种离子对峰电流ip’’的影响。该方法可用于水果、饮料中微量镍(II)的测定。     

Potentiometric Determination of Aluminum in Foods, Pharmaceuticals, and Alloys by AlMCM-41-Modified Carbon Paste Electrode

A new chemically modified electrode is constructed by incorporating AlMCM-41 into carbon paste matrix (AlMCM-41-MCPE) and used as a sensitive sensor for detection of aluminum in aqueous and nonaqueous solutions. The rapid exchange kinetics in the membrane results in a near-Nernstian behavior of the modified electrode and makes it a suitable potentiometric sensor for detection of aluminum. A linear response in concentration range from 1.0?×?10^?6 to 1.0?×?10^?1 mol/L (0.027 μg/mL–2.7 mg/mL) was obtained with a detection limit of 4.6?×?10^?7 mol/L for the potentiometric detection of aluminum. Selectivity coefficients of a number of interfering cations have been estimated. The interference from many of the investigated ions is negligible. The AlMCM-41-MCPE is suitable for use in aqueous solution of pH 2–6 and in partially nonaqueous medium. The modified electrode exhibited a fast response time (~8 s), good stability, and an extended lifetime. The developed sensor was used successfully for the determination of Al³⁺ in some alloys, drugs, and food products.     

Potentiometric sensor for sorbic acid determination in food products

The construction, evaluation and application of a new potentiometric sensor, namely, Pt|Hg|Hg₂(SOB)₂ |Graphite, where SOB stands for sorbate ion, are described. This electrode has a wide linear dynamic range between 5.0 × 10⁻⁷ and 1.0 × 10⁻² mol L⁻¹ with a near-Nernstian slope of (−58.6 ± 1.3) mV decade⁻¹ and a detection limit of 4.3 × 10⁻⁷ mol L⁻¹. The potentiometric response is independent of the pH of the solution in the pH range 6.0–9.0. The electrode is easily constructed at a relatively low-cost with fast response time (within 15–30 s) and can be used for a period of 4 months without significant change in its performance characteristics. The proposed sensor displayed good selectivities over a variety of other anions (carboxylates and inorganic anions). The potentiometric sensor was successfully applied to the determination of sorbic acid in real food samples, that is, soft drinks, skim yogurts, jams and sauces.     

Direct potentiometric determination of diastase activity in honey

A novel method for the determination of diastase activity is reported. The method is based on a direct potentiometric measurement of triiodide ion that is released when a starch-triiodide complex is hydrolysed by honey diastase. The increase of free triiodide ion concentration in a sample is found to be directly proportional to the diastase activity of the sample. A response mechanism of the platinum redox electrode is proposed, allowing a calculation of the diastase activity factor (F). The sensor and analyte parameters, including F, were obtained by least squares fitting of potentiometric data using the optimisation function of the Solver add-in of Microsoft Excel. The values of F obtained by the new direct potentiometric method were compared with those obtained using the standard Phadebas method (DN values), and the two values were found to agree within experimental error. Finally, the diastase activity of nine varieties of honey was determined using the novel method developed here.     

POTENTIOMETRIC TITRATION OF CHLORIDE IN BEER AND WORT USING AN ION-SELECTIVE ELECTRODE

A silver electrode — reference electrode pair connected to a pH/mV meter may be used as a potentiometric indicator of the equivalence point in silver nitrate titration of chloride. The method, applied to beer and wort, is sensitive and reproducible and gives good recovery of added chloride.     

纳米氧化铁修饰电位型抗坏血酸传感器的研制

将纳米氧化铁修饰电极制备成电位型传感器用于抗坏血酸的测定,并研究其性能、测定条件及干扰物质的影响。结果表明：该传感器在pH6.5的磷酸缓冲溶液中对抗坏血酸标准溶液的线性范围1.0×10-6～1.0×10-3mol/L呈良好的线性关系(r＝－0.9969),斜率为－30.2,检出限为8.9×10-7mol/L。利用该传感器测定橙汁和VC药片中的抗坏血酸,获得令人满意的结果。     

Determination of sodium in processed foodstuffs using a bis(12-crown-4) derivative-based poly(vinyl chloride) membrane electrode

A poly(vinyl chloride) matrix membrane sodium selective electrode based on bis[(12-crown-4)ylmethyl] 2-dodecyl-2-methylmalonate ((12-crown-4)yl = 1,4,7,10-tetraoxacyclododecyl) was utilised for the determination of sodium in various foodstuffs such as soup stocks, instant noodle stocks and milk powders. Good agreement was obtained between the proposed electrode and flame photometric methods. Also, the electrode exhibits minimum interference from potassium, calcium, magnesium, iron(III), copper(II) and glucose, and from the synthetic colours tested.     

Injection of synthetic human growth hormone-releasing factors in dairy cows. 1. Effect on feed intake and milk yield and composition

Eighteen multiparous Holstein cows in the second half of their lactation were used to determine the effect of human growth hormone-releasing factor (1-44)NH2 and a fragment of growth hormone-releasing factor (1-29)NH2 on lactational performance and feed intake. Saline, the 44-amino acid peptide or the 29-amino acid fragment, at the same dose per injection (.2 nmol.kg-1) was injected intravenously at 4-h intervals for 10 d. Average milk yield, milk composition, feed intake, and feed efficiency were compared for the second half of each 10-d preinjection, injection, and post-injection period. Injections of the 44-amino acid peptide and the 29-amino acid fragment increased milk yield 18.6 and 14.6%, respectively. Feed intake was not changed, but feed efficiency was increased 23.9 and 18.8% over control following 44-amino acid peptide and the 29-amino acid fragment injection, respectively. The lactational response was not different between the two peptides for any of the variables measured. This study demonstrates the feasibility of using a growth hormone-releasing factor fragment as an alternative method of elevating milk yield in cattle via somatotropins.     

Determination of chlorine ions in raw milk by pulsed amperometric detection in a flow injection system

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.