多波长线性回归-矩阵法同时测定乙二醛、乙醛酸、草酸的含量

根据实验得出的乙二醛、乙醛酸、草酸三组分混合物中各组分在特定波长下呈现出的良好的线性关系,建立起三组分质量浓度与混合吸光度的回归方程组,形成了多波长线性回归-矩阵法,实现了乙二醛氧化制备乙醛酸体系中反应产物乙二醛、乙醛酸、草酸含量的同时测定.研究结果表明:当乙二醛检测下限为1.024 mg/L时,回收率为94%~98%...     

离子色谱法同时检测乙醛酸和草酸含量的研究

工业上生产乙醛酸的反应液中不仅含有副产物草酸,而且含有未反应的乙二醛,这给产品的检测带来了较大困难.由于乙二醛在溶液中不以离子形式存在,根据离子色谱的检测原理,其不能被检测.故本文用离子色谱法测定混合液中乙醛酸与草酸的含量,选用c(Na2CO3)=1.0mmol/L+c(NaHCO3)=1.25mmol/L作为流动相,流速为2.0 mL/min.在相同的分析条件下,从准确度、线性、检出限等方面进行了考察.结果表明:该方法乙醛酸与草酸的检测限分别为0.055和0.085 mg/L,标准偏差均小于1.2%,在一定范围内线性关系良好,其回收率均在94%～107%之间.     

离子色谱法测定氧气氧化乙二醛制备乙醛酸反应介质中乙醛酸和甲酸

应用离子色谱法测定了氧气氧化乙二醛法制备乙醛酸的反应介质中乙醛酸及甲酸的含量.采用YSA 8型8162A-1#阴离子色谱柱作为固定相,用4.8 mmol·L-1碳酸钠溶液和6.0 mmol·L-1碳酸氢钠溶液的混合溶液作为流动相,其流速为1.0 mL·min-1.测定中采用电导检测法测得甲酸及乙醛酸色谱峰的保留时间依次为3.015 min和4.282 min,以此作为此两种化合物的定性依据.以上述两种化合物的质量浓度作为横坐标,与其相应的峰面积制作标准曲线,作为对此两种化合物定量测定的基础.用标准加入法对两种化合物回收率作了试验,测得其回收率在98%～103%之间.     

紫外吸光光度法同时测定乙醛酸和乙二醛

利用醛基与羟胺在酸性条件下的加成反应产物乙醛酸肟和乙二醛二肟的不同紫外吸收峰,用双波长法同时测定溶液中的乙醛酸和乙二醛。结果表明,乙醛酸在 0.03~0.156 g·L-1范围内符合比耳定律,其回归方程为 y=0.109 4x-0.003 7,r=0.999 9(n=5),乙二醛在 0.1~0.5 g·L-1范围内符合比耳定律,其回归方程为y=0.223 11x-0.023 5,r=1.000 0(n=5)。乙醛酸和乙二醛质量比大于1,乙醛酸的回收率为 96.2%~101.5%,乙二醛的回收率为 101.6%~106 8%。方法操作简便、经济、精密度较好。     

The Research of Oxidation of Glyoxal to Glyoxylic Acid over Gold Catalyst

利用沉积-沉淀法和溶液相还原法制备了系列金催化剂,以氧气氧化乙二醛合成乙醛酸为探针反应,进行了反应条件的优化,并通过对催化剂进行XRD、AAS、UV-Vis和XPS表征,分析了影响催化剂活性的因素.结果显示：与沉积-沉淀法相比,采用溶液相还原法制备的催化剂Au/ZrO2（L）,金的实际负载量较高,表现出较高的催化活性,当溶液pH为7.7,反应温度为323 K时,乙醛酸收率达到6.2%.     

涂布2,4-二硝基苯肼的环形溶蚀器/滤膜系统和高效液相色谱法检测大气中二羰基化合物

建立了环形溶蚀器/滤膜系统(Annular denuder/filter pack system)和2,4-二硝基苯肼(DNPH)-高效液相色谱法(HPLC)采集和检测大气中气相和颗粒相二羰基化合物的方法。DNPH作为吸附剂分别涂布在环形溶蚀器的内壁和3层滤膜上,当大气样品经过环形溶蚀器时,含有气相二羰基化合物的气体吸附到环形溶蚀管内壁上与DN-PH发生反应,而颗粒相部分穿过环形溶蚀管,采集到滤膜上。样品经乙腈洗脱、浓缩后,采用HPLC进行分析。根据不同的采样流速、采样时间和DNPH的涂布量采集到的二羰基化合物的浓度,确定的最佳采样条件为:采样流速4 L/min,采样时间4~5 h,DNPH浓度0.47 g/L。使用Tedlar bag验证环形溶蚀器乙二醛和甲基乙二醛的采集效率(分别为82%和85%)。利用此方法对实际大气中的二羰基化合物进行了检测。     

金催化剂上乙二醛氧气氧化合成乙醛酸的研究

利用沉积-沉淀法和溶液相还原法制备了系列金催化剂,以氧气氧化乙二醛合成乙醛酸为探针反应,进行了反应条件的优化,并通过对催化剂进行XRD、AAS、UV-Vis和XPS表征,分析了影响催化剂活性的因素.结果显示:与沉积-沉淀法相比,采用溶液相还原法制备的催化剂Au/ZrO2(L),金的实际负载量较高,表现出较高的催化活性,当溶液pH为7.7,反应温度为323 K时,乙醛酸收率达到6.2%.     

乙二醛电氧化制备乙醛酸

本文介绍了一种用电化学法合成乙醛酸的新方法 ,采用以DSA作阳极材料的离子交换膜电解槽和周期性间歇操作方式 ,研究了乙二醛和盐酸混合体系中各种工艺条件对电流效率(CEa)和乙醛酸收率 (RSa)的影响 ,得最佳电解条件 :反应温度 30～ 40℃ ,电解液流速 1.4m/s,电极电流密度 45 0A/m2 ,乙二醛初始浓度 (wt%以下同 ) 9.1%～ 16 .0 % ,盐酸初始浓度 4%～ 6 % ,在此条件下电解乙二醛 ,乙醛酸收率 91.1% ,电流效率 80 .0 % .     

乙二醛与乙醛酸的比值导数波谱法同时测定

利用比值导数波谱法同时检测乙二醛(GLY)和乙醛酸(AGLY),为GLY催化氧化过程的实时、快速分析提供了新的手段.研究表明,GLY的催化氧化副产物草酸(OX)对GLY、AGLY的分析没有干扰.AGLY的质量浓度(p)在1.47～7.33 ms/L范围内与其吸光度比值导数值(y)呈良好的线性关系,回归方程:y=0.016 31 p-0.013 5,r=0.999 0(n=5);GLY的质量浓度在1.68～9.13 mg/L范围内与其吸光度比值导数值呈良好的线性关系,回归方程:Y=-0.5374 P 0.010 4,r=1(n=5).AGLY与GLY的质量比为0.37～3.35时,AGLY的回收率为95%～103%,GLY的回收率为98%～105%.     

偏二甲肼衍生-高效液相色谱法测定水产品中甲醛

在高效液相色谱法(HPLC)测定水产品中甲醛时采用偏二甲肼作为衍生化试剂对甲醛进行预衍生化.经在中性溶液中反应10 min后定量生成衍生化产物偏二甲腙,偏二甲腙在紫外光区呈现强吸收,其吸收峰在237 nm波长处,可不经任何富集处理直接进行HPLC测定.偏二甲腙(方法中以甲醛表示)的质量浓度与其吸光度之间在0.12～1 200 mg·L-1范围内呈线性关系.测得方法的检出限(3S/N)为0.5μg.·g-1.对3种水产品样品进行了分析并对方法的精密度做了检测,求得其相对标准偏差均小于6%,以3种不同的水产品样品作为基体,加入不同浓度的标准甲醛进行了回收试验,测得结果在88%～110%之间.     

V_2O_5/C催化氧化乙二醛制备乙醛酸

利用等体积浸渍法制备了V2O5/C催化剂,并应用于乙二醛的液相氧化反应,采用XRD、TEM手段对催化剂进行了物化性质表征.结果表明,V2O5/C对乙二醛的氧化表现出较高的催化活性和乙醛酸选择性,反应10h,乙二醛的转化率达29.2%,乙醛酸得率13.6%.与贵金属Pd-Bi/C催化剂相比,V2O5/C催化剂的稳定性和重复使用效果都比较好.     

Oxidation of glyoxal to glyoxylic acid by oxygen over V2O5/C catalyst

A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.     

固定床电解槽变电流成对电解合成乙醛酸

对电解氧化乙二醛合成乙醛酸过程 ,固定床电解槽和变电流电解效果明显优于平板型电解槽和恒电流电解效果 .当阳极液中乙二醛和盐酸初始质量分数 (WCHOCHO 和WHCI)分别等于7.0 %和 8.0 %、阴极液为始终饱和的草酸溶液和微量的添加剂时 ,采用平均电流密度 (i)为 15 35A/m2 的变电流方式电解 ,阳极电流效率 (CEa)为 85 .3%、乙醛酸选择性 (RSa)为 93.9% ;阴极电流效率 (CEc)为 86 .7% ,乙醛酸选择性 (RSc)为 94 .0 % .阳极初产品中WCHOCOOH∶WCHOCHO≥ 4 0∶3,克服了阳极产品中乙二醛难以除去的困难     

Improved synthesis of 3-methoxy-4-hydroxymandelic acid by glyoxalic acid method

The most important industrial process for the synthesis of vanillin is performed in two steps involving an condensation reaction of glyoxalic acid with guaiacol followed by an oxidative decarboxylation of the intermediary 3-methoxy-4-hydroxymandelic acid (MHPA) formed, thereby producing not only vanillin, but also byproducts, which have to be eliminated. In the present study, we focused our efforts on the first step of vanillin synthesis, namely, the condensation reaction governing the yield of vanillin. The factors influencing the stability of glyoxalic acid were preliminarily evaluated to provide significant referential value for suppressing the dismutation of glyoxalic acid in the condensation reaction, and the results indicate that the stability of glyoxalic acid largely depends on the pH, temperature, and holding time of the feed solution. Then the process of the condensation reaction was optimized under the factors affecting the stability of glyoxalic acid, as well as the molar ratio of guaiacol to glyoxalic acid. Under the optimized conditions, the maximum yield of the condensation reaction can reach to 88%.     

Glyoxal sample preparation for high-performance liquid chromatographic detection of 2,4-dinitro-phenylhydrazone derivative: Suppression of polymerization and mono-derivative formation by using methanol medium

Some difficulties on a sampling of gaseous glyoxal using DNPH-silica cartridge were discussed, and an alternative sampling procedure was proposed. When glyoxal was sampled using the cartridge, it partially formed mono-hydrazone with various degrees, whereas it was quantitatively converted into its bis-hydrazone when sample gas was directly bubbled into a DNPH acidic solution. Additionally, glyoxal polymerized on the inner wall of the system during trapping to the silica cartridge. We found that the polymerization of glyoxal was effectively suppressed by dissolving glyoxal into methanol under reduced pressure; glyoxal in methanol readily reacted with DNPH in a hydrochloric acid solution and gave bis-hydrazone derivative, without any interference of methanol and any formation of mono-hydrazone derivative. When glyoxal was sampled by the proposed method, 102% of recovery was obtained, whereas it was reduced to 92.7% when the trapped glyoxal was dissolved into methanol under atmosphere.     

毛细管电泳法同时分析水、乳、膏类化妆品中5种有机酸

建立了毛细管电泳同时分析5种有机酸的间接紫外检测法。优化了背景电解质溶液中表面活性剂十四烷基三甲基溴化铵（TTAB）的浓度和溶液pH。优化后的电泳分析条件如下：含0.4 mmol/L TTAB的15 mmol/L邻苯二甲酸氢钾溶液为背景电解质（pH 5.6）；分离电压-15 kV；检测波长254 nm；分离温度25℃；进样压力5 kPa；进样时间5 s。在此条件下，可在6 min内完成5种有机酸的同时分离检测，线性范围为甲酸15~600 mg/L、苹果酸30~800 mg/L、柠檬酸20~700 mg/L、乙醇酸40~500 mg/L和乳酸30~5000 mg/L，线性相关系数为0.9983~0.9998；检出限为0.1~2.0 μg/g。该方法可用于检测水状、乳状、膏状3类化妆品中的5种有机酸。在3个加标水平下，有机酸分析的回收率为95.0%~101.6%，RSD在2.0%以内。该方法操作简单，分析快速，安全环保，灵敏度高，重现性好，有望用于化妆品生产和保存过程中有机酸的监测。     

Catalytic oxidation of glyoxal to glyoxalic acid over Au-Pd alloy nanoparticles on hydrotalcite

Synthesis of glyoxalic acid by selective oxidation of glyoxal at ambient temperatures with O₂ as an oxidant is an important problem. We found that gold nanoparticles supported on hydrotalcite (Au/HT) exhibit an appreciable catalytic activity for this reaction in the liquid phase. Moreover, Au-Pd/HT, prepared by the deposition-precipitation method is superior in the catalytic behavior to monometallic Au/HT and Pd/HT catalysts. Introduction of palladium enhances ability of the catalysts to oxidize carbonyl to carboxyl, weakens the power to rupture C-C bond and in this way improves the catalytic performance. Furthermore, the Au: Pd ratio also influences the properties of the alloy catalysts. The 1.5Au-1.5Pd/HT catalysts show the highest activity for the selective oxidation at ambient temperature producing glyoxalic acid in 13.4% yield at pH 7.7. Moreover, due to basic properties of hydrotalcite, glyoxalic acid could be synthesized over 1.5Au-1.5Pd/HT in 8.0% yield without adding a base. It is hoped that results of this study can fuel further research in designing new catalysts with alloy nanoparticles supported by hydrotalcite that can be used for the selective oxidation of other useful compounds.     

毛细管区带电泳法测定卷烟中的生物碱

在磷酸缓冲体系中采用毛细管区带电泳法测定卷烟中的生物碱时,检测灵敏度低,分离度差。考察了卷烟中生物碱的 提取条件,分离缓冲溶液的类型、pH值和浓度,卷烟中生物碱测定方法的线性范围、检出限、重现性和回收率。结果发 现,当采用410 mmol/L的酒石酸溶液（pH 2.8）为缓冲体系时,卷烟中生物碱的检测灵敏度和分离度均有明显改善,烟碱 的线性范围为0.06~0.80 mg/L（其他生物碱为0.006~0.10 mg/L）,检出限为0.002~0.01 mg/L,相对标准偏差为2.2%~10%,回收率为87.6%~102%。