红外光谱-偏最小二乘法定量分析三组分纤维混纺比

红外光谱法已被应用于两组分混纺纤维混纺比的测定,其在三组分混纺纤维混纺比测定中的应用少有研究,文章旨在研究红外光谱结合偏最小二乘法在三组分混纺纤维混纺比测定中的应用。利用红外光谱仪,采集棉、羊毛、腈纶纤维的红外光谱图,应用TQ Analyst软件中的偏最小二乘法,选择合适的峰范围,建立棉/羊毛/腈纶的定量分析模型。通过定量分析模型的回归系数、均方根误差的大小,以及与化学溶解法对比分析的结果,得出红外光谱法结合偏最小二乘法可以准确测定三组分混合纤维混纺比的结论。     

用偏最小二乘紫外光谱法同时测定维生素B混合物

用偏最小二乘紫外光谱法同时测定了B族维生素4组分混合物，采用相关系数－标准偏差法从4组分混合物（波长范围330nm－210.5nm）的紫外光谱中选出11个波长点，根据预测集残余误差选择8个因子，应用偏最小二乘法成功地实现了对VB1，VB2，VB6和NA（nicotinamide）的同时测定，相关系数分别为0.99993,0.99988,0.99998和0.99984，标准偏差分别为0.0234,0.0162,0.0205和0.0986。     

鲫鱼新鲜度近红外定量预测模型的建立

为实现鲫鱼新鲜度的快速测定,本文基于近红外漫反射光谱定量分析技术和化学计量学方法,采集了144个鲫鱼鱼肉样品在1000~1799 nm范围内的光谱数据,测定了鲫鱼样品的p H、TVB-N含量、TBA含量和K值四种新鲜度指标;在确定近红外光谱数据最佳预处理方法和适宜波段的基础上,分别采用偏最小二乘法、主成分分析和BP人工神经网络技术、偏最小二乘法和BP人工神经网络技术建立了鲫鱼新鲜度定量预测模型。结果表明,鲫鱼样品四种指标数据范围均较大,可满足建模要求。以p H为鲜度指标时,采用偏最小二乘法和BP人工神经网络技术建立的模型最好,其定标相关系数为0.9945;以TVB-N、TBA和K值为鲜度指标时,采用偏最小二乘法建立的模型最好,其定标相关系数分别为0.9857、0.9985和0.9952。建立的四种鲜度指标定量模型均具有较好的预测能力。     

光谱重叠的高级醇混合物的同时定量分析

目的 对同时测定光谱重叠严重的异丁醇、异戊醇和正丙醇3组分体系的方法进行研究.方法 根据醇类与对二甲氨基苯甲醛反应的显色特征选择最佳试验条件,采用偏最小二乘法(PLS)对光谱重叠严重的异丁醇、异戊醇和正丙醇3组分进行分析.结果 对模拟混合试样,异丁醇、异戊醇、正丙醇回收率分别为99.8％、99.6％和99.9％,相对预报误差(RPEs)分别为0.88％、1.81％和0.90％;回收率和RPEs在允许范围内.结论 使用偏最小二乘法测定异丁醇、异戊醇和正丙醇3组分,测量体系稳定、结果可靠.     

基于多酚类物质差异性判别普洱生茶的贮藏年限

以茶叶中多酚类物质作为判别普洱茶贮藏年限的指标,开展贮藏年限研究。以18种代表性多酚类成分作为特征物质,通过高效液相色谱仪测定,结合主成分分析、聚类分析和偏最小二乘判别法研究不同贮藏年限普洱生茶中多酚类物质的变化特征。结果表明:随着贮藏时间的延长,普洱生茶中儿茶素类组分含量呈逐渐下降的趋势,茶黄素类组分含量呈逐渐上升的趋势,黄酮及黄酮苷类成分中部分组分呈下降趋势,而部分组分呈上升趋势。化学计量学分析表明:相同贮藏年限的普洱生茶样品可聚集在一起,而不同贮藏年限样品之间呈现分离结果。经偏最小二乘判别法分析,不同贮藏年限普洱生茶样品呈现明显的分离趋势。依据偏最小二乘法分析中变量(变量值1)重要性分析结果,结合含量差异性分析结果,没食子酸、山奈酚、茶黄素-3-没食子酸酯、表没食子儿茶素、表儿茶素、没食子儿茶素、没食子儿茶素没食子酸酯7种多酚成分被视为特征性标志成分,可用于鉴别普洱生茶贮藏时间。     

电子舌对啤酒的区分识别研究

采用电子舌对不同品牌的啤酒及其混合样品进行识别,对所获得的数据进行主成分分析、判别因子分析和偏最小二乘回归分析。结果表明：电子舌能够有效识别不同品牌的啤酒及不同品牌啤酒的混合样品;对不同品牌啤酒的混合样品建立了偏最小二乘回归分析预测模型,电子舌响应信号和啤酒混合比例之间有很好的相关性(相关系数为0.9436),偏最小二乘回归分析模型预测误差在1.43%～3.00%之间。证明电子舌可用于啤酒的识别。     

用混合线性分析法建立苹果糖度近红外光谱预测模型

用混合线性分析法的一种变形算法建立了苹果糖度近红外光谱预测模型，并与偏最小二乘模型进行比较。结果表明：虽然最佳的混合线性分析法模型（18个主因子）比最佳偏最小二乘模型（11个主因子）复杂．但其精度却明显优于偏最小二乘模型：利用梗正集的28个苹果样本建立的糖度混合线性分析法校正模型，其相关系数r^2和标准偏差SEC分别为0．92509和0．40618；该校正模型经预测集的11个样本验证，相关系数r^2和标准偏差SEP分别达到0.87611和0．48480。混合线性分析法建立的糖度模型对苹果光谱的校正标准偏差SEC和预测标准偏差SEP分别比PLS法的SEC（0．41473）和SEP（0．50473）减小了2％和3．9％。结果表明：在诸如苹果糖度这一类农产品品质综合指标（非纯组分含量指标）的光谱检测中，应用混合线性分析法进行定量分析是完全可行的。并且其结果可与偏最小二乘法（PLS）的结果相媲美。     

电子舌对鸡汤和人工勾兑高汤及其混合样品的识别

运用电子舌对鸡汤与人工勾兑高汤及其混合样品进行识别,对所获得的数据进行主成分分析、判别因子分析和偏最小二乘回归分析。结果表明:电子舌能够有效识别鸡汤与各种人工勾兑的汤,以及其混合样品;对不同混合比例的鸡汤建立了偏最小二乘回归分析预测模型,电子舌响应信号和鸡汤混合比例之间有很好的相关性(相关系数为0.958 71),偏最小二乘回归分析模型预测误差在15%以内。证明电子舌可用于鸡汤与人工勾兑汤的识别。     

偏最小二乘速差动力学分光光度法同时测定酪氨酸和色氨酸

本实验采用速差动力学分光光度法对酪氨酸和色氨酸的混合物进行不经分离的同时测定.在碱性介质下,KMnO4可以氧化酪氨酸和色氨酸,同时KMnO4被还原为浅绿色的MnO42-,测定反应过程中MnO2-的吸光度可推知其浓度的变化情况.测定所得的数据采用化学计量学.偏最小二乘方法解析,从而可对酪氨酸和色氨酸分别进行测定.     

二组分食用调和油组成的近红外光谱检测定量分析

分别取花生油、大豆油、玉米油和葵花籽油调和成不同比例的二组分食用调和油样品,采集样品在4 000 cm-1～10 000 cm-1范围内的近红外漫反射光谱,光谱经一阶导数等预处理后,采用偏最小二乘法建立二组份调和油中各组分含量的定标模型,并用Leave-one-out内部交叉验证法对模型进行验证.四种食用油定标模型的相关系数R分别为0.999 6,0.993 1,0.998 5和0.998 8,校正均方根RMSEC分别为0.83%,3.81%,1.76%和1.57%.采用不同品牌的玉米油和大豆油配制成二组分调和油样品,建立的PLS定标模型其R和RMSEC分别为0.998 5和1.42%.研究结果表明,采用近红外光谱法可以实现二组分调和食用油中不同成分含量的准确定量检测,检测结果不受食用油生产厂家的影响.     

电位滴定结合偏最小二乘算法用于溶液中肉桂酸和L-苯丙氨酸的同时测定

结合自动电位滴定和化学计量学算法,建立同时测定溶液中肉桂酸、L-苯丙氨酸和硫酸铵的方法。通过正交设计25组校正集溶液,通过留一验证法对校正集最佳主成分进行选择,得到偏最小二乘法较佳模型,并对模拟样品进行分析。结果显示：肉桂酸、L-苯丙氨酸、硫酸铵的回收率分别在92.9%～104.4%、94.9%～101.5%、96.6%～105.1%之间。基于PLS的方法可以方便解析重叠的滴定图谱,不需要预先分离即可预测成分浓度。     

Biofilm formation, cellulose production, and curli biosynthesis by Salmonella originating from produce, animal, and clinical sources

The ability of 71 strains of Salmonella enterica originating from produce, meat, or clinical sources to form biofilms was investigated. A crystal violet binding assay demonstrated no significant differences in biofilm formation by isolates from any source when tested in any of the following three media: Luria-Bertani broth supplemented with 2% glucose, tryptic soy broth (TSB), or 1/20th-strength TSB. Incubation was overnight at 30 degrees C under static conditions. Curli production and cellulose production were monitored by assessing morphotypes on Luria-Bertani agar without salt containing Congo red and by assessing fluorescence on Luria-Bertani agar containing calcofluor, respectively. One hundred percent of the clinical isolates exhibited curli biosynthesis, and 73% demonstrated cellulose production. All meat-related isolates formed curli, and 84% produced cellulose. A total of 80% of produce-related isolates produced curli, but only 52% produced cellulose. Crystal violet binding was not statistically different between isolates representing the three morphotypes when grown in TSB; however, significant differences were observed when strains were cultured in the two other media tested. These data demonstrate that the ability to form biofilms is not dependent on the source of the test isolate and suggest a relationship between crystal violet binding and morphotype, with curli- and cellulose-deficient isolates being least effective in biofilm formation.     

Direct determination of lactulose in heat‐treated milk using diffuse reflectance infrared Fourier transform spectroscopy and partial least squares regression

The aim of this work was the direct determination of lactulose (LCT) concentration in freeze‐dried heat‐treated milks using diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) without any chemical pretreatment of the milk. The ‘actual’ lactulose concentrations estimated by means of high‐performance liquid chromatography (HPLC) were correlated with the spectral region 1286–754 cm^?1 of DRIFTS spectra in the second‐derivative form of the milk samples using partial least squares (PLS) regression. A linear relationship was established between the ‘actual’ and the concentrations recalculated using the built model. The proposed DRIFTS method is simple, rapid and low cost.     

Direct Determination of Saccharin and Acesulfame-K in Sweeteners and Fruit Juices Powders

A simple and rapid analytical procedure for determination of saccharin (SAC) and acesulfame-K (AC-K) based on UV-vis measurements and partial least squares (PLS) was proposed. Thus, an experimental design at levels 2 and 15 mg l⁻¹ for SAC and 2 and 20 mg l⁻¹ for AC-K was applied. Because real samples usually contain SAC and AC-K combined with aspartame (ASP), this interference was also included in the model. The procedure was successfully applied for SAC and AC-K simultaneous determination in sweeteners and fruit juice powders, without any separation step to remove ASP. The results were validated by using spiked samples, and the obtained recoveries were satisfactory.     

近红外光谱法非破坏快速检测生菜中硝酸盐含量

运用傅里叶变换近红外光谱仪,以二阶导数处理光学数据,用偏最小二乘法(Partial Least-Squares Regression,PLSR)进行统计分析,对58个外观形状不同的生菜样品建立了硝酸盐含量快速检测模型。其预测结果与国标方法相比相关系数为0.9819,检测相对误差在0.56%～6.79%范围内。该方法简单、快速,无需消耗任何试剂,可满足现场快速检测的需要。     

养殖水中孔雀石绿、隐色孔雀石绿、结晶紫、 隐色结晶紫、亚甲基蓝残留量的测定

目的建立一种高效液相色谱-串联质谱同时测定养殖水体中孔雀石绿、结晶紫及其代谢物和亚甲基蓝残留量的方法。方法将水样用盐酸羟胺-对甲苯磺酸溶液和乙腈提取,二氯甲烷萃取2次后浓缩,用1 mL乙腈-5 mmol/L乙酸铵(1:1,V:V)定容。以乙腈-5 mmol/L乙酸铵(85:15,V:V)混合溶液为流动相进行色谱分离,然后进入串联质谱仪,选用电喷雾离子源,在正离子、多反应监测扫描模式下进行定性,孔雀石绿和结晶紫通过内标法定量,亚甲基蓝通过外标法定量。结果在优化条件下,孔雀石绿、隐色孔雀石绿、结晶紫、隐色结晶紫在0.025~0.600 ng/mL浓度范围内,亚甲基蓝在0.05~1 ng/mL浓度范围内均满足线性关系,相关系数r0.99,方法检出限为0.2 ng/mL。加标浓度在0.2~2.0 ng/mL时,孔雀石绿、隐色孔雀石绿、结晶紫、隐色结晶紫和亚甲基蓝的平均回收率均在70%~110%之间,相对标准偏差均在10%以内。结论该方法简单快速、灵敏度高、前处理成本低、重现性好、回收率高,适用于同时检测养殖水体中孔雀石绿、隐色孔雀石绿、结晶紫、隐色结晶紫、亚甲基蓝残留量。     

Simultaneous Spectrophotometric Determination of 2-Thiouracil and 2-Mercaptobenzimidazole in Animal Tissue Using Multivariate Calibration Methods: Concerns and Rapid Methods for Detection

ABSTRACT: Two multivariate calibration methods, partial least squares (PLS) and principal component regression (PCR), were applied to the spectrophotometric simultaneous determination of 2-mercaptobenzimidazole (MB) and 2-thiouracil (TU). A genetic algorithm (GA) using partial least squares was successfully utilized as a variable selection method. The concentration model was based on the absorption spectra in the range of 200 to 350 nm for 25 different mixtures of MB and TU. The calibration curve was linear across the concentration range of 1 to 10 μg mL⁻¹ and 1.5 to 15 μg mL⁻¹ for MB and TU, respectively. The values of the root mean squares error of prediction (RMSEP) were 0.3984, 0.1066, and 0.0713 for MB and 0.2010, 0.1667, and 0.1115 for TU, which were obtained using PCR, PLS, and GA-PLS, respectively. Finally, the practical applicability of the GA-PLS method was effectively evaluated by the concurrent detection of both analytes in animal tissues. It should also be mentioned that the proposed method is a simple and rapid way that requires no preliminary separation steps and can be used easily for the analysis of these compounds, especially in quality control laboratories.     

Analysis of incurred crystal violet in Atlantic salmon (Salmo salar L.): comparison between the analysis of crystal violet as an individual parent and leucocrystal violet and as total crystal violet after oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone

Due to on-going concern about the occurrence of triphenylmethane dye residues in fish destined for human consumption, a depletion study of crystal violet in salmon was carried out. Atlantic salmon less than 12 months old were exposed to crystal violet in fresh water at 15°C and subsequently sampled at 1, 7, 14, 28, 63 and 91 days after exposure. The salmon were then analysed by two analytical methods. In the first method, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) was used to oxidise leucocrystal violet to its parent form. Total parent crystal violet was then analysed by LC-MS/MS. In the second method, crystal violet and leucocrystal violet were analysed individually by LC-MS/MS without oxidation. Both methods gave comparable results for total crystal violet concentrations, with a correlation of r(2)=0.69. Statistical treatment for 88 incurred salmon samples showed no significant difference between the two sets of results with t=1.68 and t(crit)=1.99. Up to 98% of crystal violet was metabolised to its leuco form in the salmon after 1 day of exposure and could be detected at significant concentrations (approximately 20 μg kg(-1)) 91 days after exposure. The depletion data also suggest that crystal violet has a half-life of approximately 15-16 days in salmon.     

Effect of gamma irradiation on microorganisms and components in empty fruit bunch and palm press fibre of oil palm wastes

The effects of irradiation on microbiological load and chemical components of empty fruit bunch (EFB) and palm press fibre (PPF) were investigated as the preliminary study for upgrading of oil palm wastes to animal feeds by fermentation. The initial contamination of microorganisms in both EFB and PPF was very high and there is no significant difference between the samples collected from various palm oil mills. The dose required to eliminate below the detectable level was more than 15 kGy for total aerobic bacteria, but 5–6 kGy is enough for fungi. The contents of holocellulose and lignin were c 60% and 25%, respectively, in both EFB and PPF, and the change in components by irradiation was small. EFB and PPF have a high water holding capacity suggesting that they are suitable substrates for fermentation. These results show that the irradiation by 5–10 kGy on EFB and PPF is applicable for the pasteurisation of fermentation media without any significant change in components.