聚酰胺吸附-高效液相色谱法测定蜜饯中的七种水溶性偶氮着色剂

利用聚酰胺吸附-高效液相色谱法测定蜜饯中的7种水溶性偶氮着色剂:柠檬黄、新红、苋菜红、胭脂红、日落黄、诱惑红和偶氮玉红,确定了检测条件为:色谱柱:Agilent 5 TC-C18(2)4.6×250mm;柱温:35℃;流动相:乙腈-乙酸铵(0.02mol/L,pH=4)(梯度洗脱);流速:1.0mL/min;进样量:20μL;检测波长:428nm和508nm。结果表明,7种水溶性偶氮着色剂在1.000～50.00μg/mL范围内线性关系良好,R2=0.99950～0.99961,加标回收率为89.1%～107%;平均相对偏差(RSD)为0.63%～2.9%。该方法灵敏度高,分离效果好,准确度高,适用于蜜饯中7种水溶性偶氮着色剂的测定。     

人工合成色素偶氮玉红标准样品的研制

建立了一种快速有效的制备食用合成色素偶氮玉红标准样品的方法。采用凝胶色谱技术对筛选的偶氮玉红原料纯化后,再用无水乙醇对产物进行沉降、洗涤,室温真空干燥,粉碎,过筛,可得偶氮玉红纯品;然后通过核磁共振(~1HNMR谱、~(13)CNMR谱)、红外光谱、LC-MS/MS法对样品进行定性分析,结构确认后进行均匀性和稳定性检验;经8家具有资质实验室进行协同定值,偶氮玉红纯度为99.23%±0.38%,满足标准样品的要求。     

固相萃取-高效液相色谱法同时测定海米中10 种合成色素

建立固相萃取-高效液相色谱法同时测定海米中新红、柠檬黄、日落黄、胭脂红、偶氮玉红、苋菜红、诱惑红、亮蓝、赤藓红、罗丹明B 10 种合成色素的方法。海米中的合成色素用氨化乙醇提取、固相萃取柱净化,ODS-3 C18柱为分离柱,甲醇和0.02 mol/L乙酸铵为流动相梯度洗脱,采用二极管阵列检测器,在360 nm波长处检测,外标法定量。10 种合成色素在0.2～50 mg/L质量浓度范围内与其峰面积成良好的线性关系;10 种合成色素的检出限为0.4～1.0 mg/kg。3 个不同加标水平的回收率为74.3%～90.0%,相对标准偏差小于4.3%。该方法能同时完成10 种合成色素的测定,可用于海米中合成色素的检测分析。     

纺织品中4-氨基偶氮苯的还原条件和检测方法探讨

对4-氨基偶氮苯的还原条件进行了初步探讨,研究了pH值对4-氨基偶氮苯回收率的影响;对4-氨基偶氮苯的测定方法的线性范围、准确性进行了验证,研究了线性范围、准确度、重复性、检出限。方法的样品加标回收率值在60%～90%之间,3个加标水平6次平行测定的相对标准偏差分别为3.60%、3.10%、5.69%,方法的检出限为0.5mg/kg。     

可变波长液相色谱法同时测定食品中18种常用食品添加剂研究

建立可变波长高效液相色谱法同时测定食品中2种甜味剂(安赛蜜、糖精钠),6种防腐剂(苯甲酸、山梨酸、脱氢乙酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、纳他霉素),9种着色剂(柠檬黄、新红、苋菜红、靛蓝、胭脂红、日落黄、诱惑红、亮蓝、偶氮玉红)及咖啡因共18种常见食品添加剂的联测方法。以Shimpack VP–ODS色谱柱(250 mm×4.6 mm,5μm)为分析柱,以甲醇∶0.02mol/L乙酸铵溶液为流动相进行梯度洗脱,紫外检测器可变波长程序进行检测,18种组分均很好分离,分别在0.10⁵0.0 mg/L浓度范围内均有良好的线性关系,相关系数r2为0.999 5150.0 mg/L浓度范围内均有良好的线性关系,相关系数r2为0.999 51⁰.999 99,平均加标回收率为85.0%0.999 99,平均加标回收率为85.0%¹09.7%,相对标准偏差为0.1%109.7%,相对标准偏差为0.1%².9%,方法的最低检出限为0.12.9%,方法的最低检出限为0.1¹.8mg/kg,满足实验室日常分析食品中常见食品添加剂的工作需求。     

高效液相色谱法同时检测虾制品中合成色素

采用高效液相色谱与二极管阵列检测器联用,建立了虾制品中柠檬黄、日落黄、偶氮玉红、苋菜红、胭脂红、赤藓红、红色2G和诱惑红等8种合成色素的多组分同时检测方法。样品采用甲醇-尿素溶液提取,提取液经固相萃取聚酰胺柱净化后,在XDB-C 18色谱柱上,由甲醇-乙腈和乙酸钠溶液组成流动相梯度洗脱条件下8种合成色素在17 min内实现了成功分离。各色素在0.05 mg/L～50 mg/L范围内具有良好的线性关系,方法的检出限在0.02 mg/L～0.10 mg/L之间。在实际样品的检测中合成色素的加标回收率在85.2%～98.9%之间,相对标准偏差在1.49%～5.64%之间。方法简单、高效,可用于虾制品中合成色素的日常检测。     

倍数滴定法快速测定面粉增白剂过氧化苯甲酰

用倍数滴定法测定面粉中的增白剂———过氧化苯甲酰,操作简便、测定快速,且灵敏度较常规碘量法滴定提高10倍以上,检测限可达0.002 g/kg,精密度试验和实样测定的相对标准偏差为0.6%~0.8%,加标回收率为96.6%~101.4%,平均回收率达98.9%。最后,比较倍数滴定法对面粉增白剂的测定结果与碘量法滴定的结果和用HPLC法测定的结果相一致。     

紫外-可见分光光度法快速检测蛋黄中苏丹红Ⅳ的研究

采用紫外一可见分光光度计对新鲜鸭蛋蛋黄的石油醚一丙酮的提取液进行光谱扫描,建立了纯蛋黄液、标准苏丹红Ⅳ样品以及含有苏丹红Ⅳ的蛋黄液的光谱扫描曲线.通过对光谱扫描曲线的相似度比较及对光谱扫描原始曲线图的数学处理,分别运用波长差和一级微分两种方法,快速检测出新鲜鸭蛋黄中苏丹红Ⅳ.实验结果表明.波长差法的回收率高于一次微分法,而且数值分布相对集中,在对被检测样品中的苏丹红Ⅳ的定量上的精确性和稳定性优于一次微分法,而一次微分法则可直观对苏丹红Ⅳ定性.运用波长差法计算样品RSD(%),得备检样品加标苏丹红Ⅳ 2μg/mL的RSD(%)为14.2,平均回收率为106.01%,加标4μg/mL的RSD(%)为9.4,平均回收率为105.68%;运用一次微分法进行计算,得备检样品加标苏丹红Ⅳ 2μg/mL的RSD(%)为10.41,平均回收率为82.46%,加标4μg/mL的RSD(%)为6.73,平均回收率为94.21%.数据表明样品中加标苏丹红Ⅳ浓度越大.该方法对样品检测的稳定性越好.     

微波消解-离子选择性电极法快速检测水产品中镉的研究

以微波消解对样品做前处理,采用多功能水质仪连接镉离子选择性电极测定水产品中镉含量.实验对溶液DH值、总离子强度调节缓冲液用量的选择、电极的性能进行分析探讨,并对鸢乌贼内脏中镉含量进行实样检测.结果表明,方法的加标回收率为94.3%～113.9%,RSD为0.9%～1.3%,准确度与精密度较好,完全适用于水产品中镉的快速检测.     

水蒸汽蒸馏—分光光度法测定卷烟中山梨酸的研究

本研究采用水蒸汽蒸馏分离、吸附树脂微型柱净化,硫代巴比妥酸光度法测定卷烟中的山梨酸。确定了最佳显色条件并探讨了蒸馏条件和吸附树脂种类对回收率的影响。对实样进行加标回收测定.回收率在86%～95%范围内。7次测定,标准偏差和变动系数分别为0.016和1.70%.具有满意的结果,符合工业分析要求。     

Differences in polymeric proteins among grains in spring wheat spikes

A uniform amount and size distribution of polymeric proteins within grains in a spike might determine the stability of wheat quality. Two cultivars were grown to maturity in solution culture in a climate chamber. Nitrogen (N) in the form of nitrate was added daily and replaced with ¹⁵N before harvest. Plants were harvested during grain development. Protein composition and relationships of labelled N in grains from different spikelets within the spike were determined. Higher percentages of large unextractable polymeric proteins (%‐LUPP) and total unextractable polymeric proteins (%‐TUPP) were found in the lower‐ and uppermost spikelets in the spike compared with the middle ones for cv. WL, but not for cv. Sport. Both cultivars showed variations in the percentage of large unextractable monomeric proteins (%‐LUMP) and total SDS‐extractable protein (Tote) in the spikelets within the spike. The amount of total SDS‐unextractable protein (Totu) did not vary for either of the cultivars. The spikelets within the spike showing high and low %‐LUMP and Tote at maturity showed a similar behaviour shortly after flowering in cv. WL, but not in cv. Sport. The N concentration of SDS and sonicated extracts varied along the spikelets of the spike for both cultivars. The atom‐% excess ¹⁵N decreased in cv. Sport SDS‐extractable and ‐unextractable proteins and cv. WL albumins + globulins, gliadins and glutenins from grains at different spikelet positions along the spike. Copyright © 2005 Society of Chemical Industry     

Dough characteristics of wheat flour milled from wheat grains stored in spike form

This study compares the effects of storage form (grain and spike) of wheat as well as grain moisture content (12%, 14% and 16%), storage time (0, 3, 6 and 9 months) and temperature (10, 20 and 30 °C) on rheological (farinograph and extensograph) characteristics of dough obtained from stored wheat. While water absorption, stability and degree of softening of wheat stored in spike form were 61.2%, 15.8 min and 25.9 Brabender unit (BU), these values of wheat stored in grain form were 60.8%, 14.1 and 29.1 BU, respectively. Resistance to extension and dough energy of wheat stored in grain form were significantly higher than those of wheat stored in spike form, while extensibility was significantly lower. Storage in spike form had a positive effect on all farinograph and extensograph characteristics of wheat stored under nonoptimal storage conditions such as high grain moisture content, high temperature and long storage time.     

Screening method for the detection of artificial colours in saffron using derivative UV-Vis spectrometry after precipitation of crocetin

A screening method for the detection of artificial colours (naphthol yellow, tartrazine, quinoline yellow, Sunset yellow, Allura red, amaranth, azorubine, Ponceau 4R and Red 2G) in saffron is described. The method involves removal of crocins by precipitation of crocetin (pH 0.1, 90°C) before adsorption of the artificial colours on polyamide SPE cartridges (pH 2). After washing with methanol, acetone and methanol, elution was done with a methanol:ammonia solution (95:5 v/v), and detection was performed by derivative spectrometry. Sample pretreatment changes the UV-Vis saffron extract profile in such a way that second derivative spectra can be used to identify the presence of added colours. Erythrosine, which was found to be pH dependent, could not be detected under the above conditions. The lowest detectable amount for each colour was strongly dependent on chemical structure. The recovery of carminic acid was very low possibly due to irreversible retention on the polyamide. This procedure can replace the current ISO TLC method (2003) and be used alternatively or in combination with HPLC procedures adopted in the same standard.     

Consideration of fluorescence properties for the direct determination of erythrosine in saffron in the presence of other synthetic dyes

Direct selective detection of erythrosine in saffron in the presence of other synthetic dyes considers its fluorescence at 532 nm excitation/548 nm emission. Saffron pre-treatment was according to the ISO 3632-2 trade standard test methods. On account of calculated quantum yield values, none of the yellow dyes is expected to interfere. Among red ones, reservations about allura red AC, azorubine and red 2G were not verified by experimentation, signifying excellent method specificity. Detection and quantification limits (0.56 and 1.70 nM) were of the same magnitude as those reported in the literature after chromatographic separation of erythrosine. The percentage recovery from spiked saffron samples ranging from 63 to 141 was acceptable for residue levels in foods. The matrix effect from crocins (saffron pigments) was evidenced only at a lower spiking level (0.02 mg kg(-1)). The minimum required performance limit (MRPL) was 0.04 mg kg(-1), indicating that the method is appropriate for determining traces of erythrosine in saffron. The approach offers improved sensitivity (by three orders of magnitude) and specificity than the direct spectrophotometric detection of certain synthetic dyes in saffron and deserves attention by the ISO Technical Committee for 'Herbs, culinary spices and condiments'.     

A comparison of the functional characteristics of wheat stored as grain with wheat stored in spike form

In this study, wheat grain and wheat spike with 12%, 14% and 16% moisture content were stored at 10, 20 and 30 °C for 0, 3, 6 and 9 months. After storage, wheat samples were investigated for hectolitre weight, gluten content, Zeleny sedimentation volume, enzyme activity, acidity, phytic acid and L colour value. Storage of wheat at different storage forms (spike and grain) and storage conditions showed considerable changes in grain quality. In general, the storage period of 3 months positively affected wheat quality. However, hectolitre weight, gluten, Zeleny sedimentation, enzyme activity, acidity and colour of wheat got worse at storage periods beyond 3 months. Hectolitre weight, wet and dry gluten, Zeleny sedimentation, phytic acid content and L Colour value of wheat stored in both spike and grain form significantly decreased during storage. However, the increase in grain moisture content, storage time and temperature resulted in significant increase in total titratable acidity and falling number values of wheat. Falling Number and phytic acid values of wheat stored in spike form were generally lower than wheat stored in grain form. Storage in spike form had a positive effect on especially wet gluten content of wheat stored at non-optimal storage conditions such as high grain moisture content and high temperature. Wet gluten of wheat stored in spike form was higher than that of wheat stored grain form after storage at 30 °C for 6 and 9 months. Wheat stored in spike form is more resistant than wheat stored in grain form against adverse storage conditions such as high moisture content and temperature and longer storage time.     

番茄、辣椒、茄子中甲基毒死蜱残留量测定

采用高效液相色谱-二极管阵列检测器对番茄、辣椒和茄子中甲基毒死蜱残留量进行测定。样品用乙腈提取后,经Carb/NH2固相萃取小柱净化,用C8液相色谱柱、二极管阵列检测器,对甲基毒死蜱残留量的测定可取得满意的结果。该方法样品平均加标回收率为80.7%～92.4%,相对标准偏差为1.1%～4.6%;蔬菜中甲基毒死蜱检出下限为0.02mg/kg。     

烟草柜式喂料机的改进

柜式喂料机在使用过程中存在的出料结团、喂料流量骤降、堵料、尾料过长等问题,主要由拨辊及侧面弧板挤压、布料不均及缺少尾料输送装置导致。为此对柜式喂料机进行了改进:优化了喂料机拨辊与底带速比配置,改造了侧面弧形板,更换了光电管的选型并启用了柜中检测器,增大了进料振槽落料斜口角度,重新设计了导流板,实施了尾料拨辊反转等。改进后的应用效果表明,出料结团、流量骤降及堵料频次分别降低了92.5%,88.9%及94.1%,平均尾料时间减少了18.1 min,烟堆高度分布均匀,出料顺利,避免了烘丝流量瞬时骤降而引起含水率标准偏差超标的问题,提高了产品工艺质量。     

An experimental proficiency test for ability to screen 104 residual pesticides in agricultural products

An experimental proficiency test program for ability to screen 104 residual pesticides in agricultural products has been conducted. Eight Japanese laboratories joined the program. Items tested in the present study were limit of detection, internal proficiency test (self spike) and external proficiency test (blind spike). All 104 pesticides were well detected and recovered from agricultural foods in the internal proficiency test. However, the results of the external proficiency test did not completely agree with those of the internal proficiency tests. After 5 rounds of the blind spike test, the ratio of the number of correctly detected pesticides to that of actually contained ones (49 total) ranged from 65% to 100% among laboratories. The numbers of mistakenly detected pesticides by a laboratory were 0 to 15. Thus, there was a great difference among the laboratories in the ability to screen multiresidual pesticides.     

超高效液相色谱-质谱法测定蔬菜水果中茚虫威的残留量

建立蔬菜、水果中的茚虫威残留的超高效液相色谱- 质谱法(UPLC-MS/MS)检测方法。样品经乙腈提取,旋转蒸发仪浓缩,SEP-PAK C18 固体萃取小柱分离净化;采用Waters BEH C18 色谱柱为分离柱,以乙腈-20mmol/L乙酸铵水溶液(含0.1% 甲酸)为流动相,在正离子模式下以电喷雾电离串联质谱仪进行测定。分别加标1.0 μg/kg 和5μg/kg 进行回收实验,平均回收率达90% 以上,平行测试6 次相对标准偏差RSD<5.0%,方法的检出限(S/N=3)为0.05μg/L。     

高效液相色谱法测定食品中亮蓝同分异构体

建立高效液相色谱法检测食品中亮蓝的新方法,初步证实食品中亮蓝主要为3种异构体的混合物。用聚酰胺层析柱净化,高效液相色谱法分离。色谱柱为Inertsil ODS-SP C18 (150mm×4.6mm,5μm),流动相为甲醇-0.02mol/L乙酸铵溶液,检测波长629nm。加标回收率为91.1%～94.7%。