用半量溴素合成溴硝醇新工艺

为了降低溴硝醇生产的溴素消耗,采用甲醛和硝基甲烷经过缩合、中和、溴化和氯化过程合成了溴硝醇。优化反应条件为缩合反应温度0~4℃,反应时间60 min;中和反应温度0~4℃,反应时间67 min;溴化反应温度-4℃以下,反应时间90 min,溴素过量5%。新工艺溴硝醇收率79.1%,含量99.7%,最大杂质含量0.09%。与传统工艺相比溴素平均消耗降低48%,原料成本降低约27.2%。     

布罗波尔的合成新方法

通过对硝基甲烷先进行溴代反应生成溴代硝基甲烷，再与甲醛进行加成反应的新方法合成布罗波尔，不仅避免了使用有毒易燃非极性有机溶剂，而且使产品的总收率达到９１２％。     

The impact of the various chemical and physical factors on the degradation rate of bronopol

Bronopol (2‐bromo‐2‐nitropropane‐1,3‐diol) is used as preservative in cosmetic industry. Its main role in commercial products consists in protection of the cosmetic composition stability by inhibiting the development of micro‐organisms. Unfortunately, preservatives can also undergo the degradation processes. The aim of examinations was to prove that bronopol decomposes in aqueous solutions and storage conditions have a significance influence on its degradation rate. High‐performance liquid chromatography method (methanol/water with hydrochloric acid 5:95 v/v) with spectrophotometric detection (210 nm) was used for examining the decomposition rate of bronopol. The impact of chemical (addition of cosmetics components: citric acid and/or sodium dodecylsulfate) and physical (elevated and ambient temperature, sunlight or ultraviolet radiation and air access) factors has been elaborated. Bronopol decomposes most rapidly (independently on the sample surrounding conditions) when it is in solution with sodium dodecylsulfate, the inverse dependence is observed in the presence of two compounds – citric acid and sodium dodecylsulfate. Additionally, the elevated temperature causes the acceleration of decomposition. Bronopol degradation by‐products were also identified as methanol, formic acid, tris(hydroxymethyl)methane and 2‐bromo‐2‐nitroethanol.     

Short communication: Analytical method and amount of preservative added to milk samples may alter milk urea nitrogen measurements

Milk urea N (MUN) is used by dairy nutritionists and producers to monitor dietary protein intake and is indicative of N utilization in lactating dairy cows. Two experiments were conducted to explore discrepancies in MUN results provided by 3 milk processing laboratories using different methods. An additional experiment was conducted to evaluate the effect of 2-bromo-2-nitropropane-1, 3-diol (bronopol) on MUN analysis. In experiment 1, 10 replicates of bulk tank milk samples, collected from the Pennsylvania State University's Dairy Center over 5 consecutive days, were sent to 3 milk processing laboratories in Pennsylvania. Average MUN differed between laboratory A (14.9 ± 0.40 mg/dL; analyzed on MilkoScan 4000; Foss, Hillerød, Denmark), laboratory B (6.5 ± 0.17 mg/dL; MilkoScan FT + 6000), and laboratory C (7.4 ± 0.36 mg/dL; MilkoScan 6000). In experiment 2, milk samples were spiked with urea at 0 (7.3 to 15.0 mg/dL, depending on the laboratory analyzing the samples), 17.2, 34.2, and 51.5 mg/dL of milk. Two 35-mL samples from each urea level were sent to the 3 laboratories used in experiment 1. Average analyzed MUN was greater than predicted (calculated for each laboratory based on the control; 0 mg of added urea): for laboratory A (23.2 vs. 21.0 mg/dL), laboratory B (18.0 vs. 13.3 mg/dL), and laboratory C (20.6 vs. 15.2 mg/dL). In experiment 3, replicated milk samples were preserved with 0 to 1.35 mg of bronopol/mL of milk and submitted to one milk processing laboratory that analyzed MUN using 2 different methods. Milk samples with increasing amounts of bronopol ranged in MUN concentration from 7.7 to 11.9 mg/dL and from 9.0 to 9.3 mg/dL when analyzed on MilkoScan 4000 or CL 10 (EuroChem, Moscow, Russia), respectively. In conclusion, measured MUN concentrations varied due to analytical procedure used by milk processing laboratories and were affected by the amount of bronopol used to preserve milk sample, when milk was analyzed using a mid-infrared analyzer. Thus, it is important to maintain consistency in milk sample preservation and analysis to ensure precision of MUN results.     

关于合成2-溴-2-硝基-1,3-丙二醇新方法的研究

通过硝基甲烷先溴化再缩合的方法合成了2-溴-2-硝基-1,3-丙二醇,合成最佳反应条件为：在溴化反应中,NaOH与CH3NO2的物质的量比为1．1：1．0,NaOH溶液的质量浓度为25％,成盐温度为-5～0℃,溴化温度为15℃;在缩合反应中．溶液pH5～6,缩合温度为25℃,V镕剂：V反应原料=2．0：1．0。质量分数为98％,产品总收率为83．5%。     

杀菌剂布罗波尔合成工艺研究进展

介绍了现行杀菌剂布罗波尔合成的各种方法，对每一种方法进行了分析和评价，并对今后的工艺改进与发展方向提出了可行性建议。     

布罗波尔的合成与精制

采用先羟甲基化后溴化反应的方法合成布罗波尔,通过正交试验考察了原料配比、反应时间、反应温度对反应结果的影响,得到的较佳反应条件如下：n（硝基甲烷）：n（氢氧化钠）：n（甲醛）：n（溴素）=1：1：2：1,羟甲基化反应温度20℃,反应时间1．5h,溴化反应温度15℃。考察了布罗波尔在单一及复配溶剂中的溶解度和重结晶试验,确定的较佳复配溶剂比m（乙酸乙酯）：m（氯仿）=1：1。在较佳反应条件下,反应过程收率可达90％,重结晶单程收率可达83％,得到的产品纯度在99％以上。     

抗菌剂溴硝醇的合成

硝基甲烷与25%氢氧化钠溶液同时滴加入甲醛溶液中反应,然后滴加溴反应得到溴硝醇;通过正交实验得出的优化条件为:烷羟基化反应中,n(硝基甲烷)∶n(甲醛)=1∶2.2,反应温度45℃,反应时间1.5 h,n(硝基甲烷)∶n(氢氧化钠)=1∶0.8;溴化反应中,n(硝基甲烷)∶n(溴)=1∶1,反应温度20℃,反应时间1.5 h,在此优化条件下收率达90.5%;产品用红外光谱和高效液相色谱进行分析确认,产品含量为99%。     

溴硝醇的合成研究

以硝基甲烷和甲醛为原料 ,在碱性条件下经烷羟基化和溴化两步反应合成了溴硝醇。考察了反应温度、反应时间、溶剂中水与醇的体积比以及溶剂用量对产品收率的影响。最佳反应条件为 :V(水 )∶V(醇 ) =0 4∶1 0 ,V(溶剂 )∶V(反应原料 ) =2 1∶1 0 ,烷羟基化反应时间为 1 5h ,反应温度为 5℃ ;溴化反应时间为 0 5h ,反应温度为 10℃。产品收率可达到 78% ,质量分数为98%。产物经高效液相色谱、红外、质谱确证。     

Effect of preservatives on the accuracy of mid-infrared milk component testing

Our objective was to determine the effect of commonly used milk preservatives on the accuracy of fat, protein, and lactose content determination in milk by mid-infrared (mid-IR) milk analysis. Two producer raw milks (Holstein and Jersey) and 2 pasteurized modified milks, 1 similar to Holstein milk and 1 similar to Jersey milk were used as the 4 different milk sources. Seven different milk preservative approaches (K₂Cr₂O₇ and 6 different bronopol-based preservatives) and a portion of unpreserved milk for each of the 4 different milks sources were tested for fat B, lactose, protein, and fat A. The experiment was replicated 3 times (28 d each) for a total of 84 d. Two mid-infrared (mid-IR) transmittance milk analyzers (an optical and a virtual filter instrument) were used. A large batch of pilot milk was prepared from pasteurized, homogenized, unpreserved whole milk, split into vials, quick frozen by immersion in liquid nitrogen, and transferred into a −80°C freezer. Pilots were thawed and analyzed on each testing day during the study. Significant increases were observed in all uncorrected readings on the pilot milks over the 84 d of the study, but the increases were gradual and small on each instrument for all components. Results from the study were corrected for these changes. A significant difference in mid-IR fat A readings was observed, whereas no differences were detected for fat B, lactose, or protein between unpreserved and preserved milks containing 0.02% K₂Cr₂O_7. Therefore, K₂Cr₂O₇ has little or no effect on mid-IR test results. All bronopol-based preservative approaches in this study differed in mid-IR test results compared with K₂Cr₂O₇-preserved and unpreserved milks, with the largest effect on protein results. Mid-IR uncorrected readings increased with time of refrigerated storage at 4°C for all preservative approaches, with the largest increase for protein. The rate of increase in uncorrected readings with time of storage was always higher for raw milks than for pasteurized milks, and the stability of instrument zero was lower for raw milks than for pasteurized milks. The largest economic effect of a systematic bias caused by a preservative occurs when the milks used for calibration and routine testing for payment do not contain the same preservative or when calibration milks are preserved and milks for routine testing are unpreserved. These effects can create errors in payment for large dairy processing plants ranging from several hundred thousand to over a million dollars annually.