Interference-free determination of Sudan dyes in chilli foods using second-order calibration algorithms coupled with HPLC-DAD

This paper presents a new method for the determination of Sudan dyes contained in hot chilli samples. The method employs second-order calibration algorithms to handle the recorded data. The second-order calibration algorithms are based on the popular parallel factor analysis (PARAFAC), alternating trilinear decomposition (ATLD) and self-weighted alternating trilinear decomposition (SWATLD), respectively. These chemometric methodologies have the second-order advantage, which is the ability to get accurate concentration estimates of interested analytes even in the presence of uncalibrated interfering components. The results on a set of spiked chilli test shows that low contents of Sudan I and Sudan II in complex chilli mixtures can be accurately determined using the new method. The sample preparation was based on solvent extraction, and internal standard was not required. Quantification was carried out with simple mobile phase.     

三维荧光光谱结合自加权交替三线性分解算法检测农药类混合物

三维荧光光谱技术与自加权交替三线性分解(SWATLD)算法相结合,对三类农药混合溶液进行检测。在乙腈溶剂中配制西维因、速灭威和三唑磷不同浓度比的混合溶液为测量样品(西维因、速灭威及三唑磷的最佳激发波长/发射波长分别为285/325,305/345和265/305 nm),利用荧光光谱仪获取样品的三维荧光光谱,经过空白扣除以及激发与发射校正,有效地去除仪器误差以及散射产生的影响,得到样品的真实光谱。采用基于自加权交替三线性分解算法对测得的光谱数据进行分析,得到的三种农药的平均回收率为96.9%±1.9%,99.8%±1.0%和100.8%±3.2%。根据SWATLD算法预测结果,计算三类农药的预测均方根误差(RMSEP)值为0.616×10-2,0.539×10-2和0.374×10-2 μg·mL-1,低于平行因子(PARAFAC)分析法预测结果的RMSEP值,且最低检测限均在0.005~0.022 μg·mL-1范围内。和PARAFAC算法相比较,突出了SWATLD算法的优势,表明该算法对光谱重叠严重的三类农药混合物有较好的分解能力。     

基于四组分同时测定的PARAFAC和SWATLD算法及比较

邻苯二酚和对苯二酚是有毒物质,酪氨酸和色氨酸是天然氨基酸中仅有的会发光的组分,由于四组分光谱重叠,很难用常规方法直接定量检测。实验中采用三维荧光光谱结合平行因子和自加权交替三线性分解算法,邻苯二酚、对苯二酚、酪氨酸和色氨酸进行直接定量测定;同时,比较两种算法在定性测定和定量测定上的差别。当测量体系的成分数预估计值为4时,两种方法分辨后的回收率分别为(101.2±2.7)%,(99.3±3.0)%,(98.7±4.5)%,(101.6±4.7)%和(109.0±8.0)%,(91.3±11)%,(99.7±13)%,(98.1±11)%。试验结果表明,两种方法可用于四组分直接快速定量测定;通过对两种算法的比较,PARAFAC算法更具优势。     

Strategies for solving matrix effects in the analysis of sulfathiazole in honey samples using three-way photochemically induced fluorescence data

A widely employed compound for honey treatment, sulfathiazole (ST), was determined in commercial honey samples, employing a combination of photochemically induced fluorescence excitation-emission matrices (EEMs) and chemometric processing of the recorded second-order data. Parallel Factor Analysis (PARAFAC) and Self-Weighted Alternating Trilinear Decomposition (SWATLD) methods were used for calibration. An appropriately designed calibration with a set of standards composed of 18 samples, coupled to the use of the second-order advantage offered by the applied chemometric techniques, allowed quantitation of sulfathiazole in spiked commercial honey samples. No previous separation or sample pretreatment steps were required. The results were compared with other calibration methods such as N-PLS and PLS-1 that produced good results on synthetic samples but not on the investigated commercial honey samples.     

Photoinduced spectrofluorimetric determination of fluoroquinolones in human urine by using three- and two-way spectroscopic data and multivariate calibration

Multivariate methods comprise of a group of chemometric tools allowing the analysis of different analytical data, i.e., spectroscopic, chromatographic obtained from multichannel detector systems. Second-way data are widely used in analytical applications in combination with multivariate calibration methods, but three- and higher-way data are yet not as widely applied. In complex biological samples, the employment of the three-way data is of special interest, as they may be combined with methods that exploit the second-order advantage allowing calculating individual concentrations of the analytes of interest in the presence of unknown interferences in untreated samples. A very sensitive and selective method is proposed, by coupling photoinduced fluorescence and multivariate analysis of the three-way data excitation-emission fluorescence matrices (EEMs), of the photoproducts obtained from UV irradiation of three fluoroquinolones: enoxacin (ENO), norfloxacin (NOR) and ofloxacin (OFLO). The application of a previous photoirrradiation process allows the determination of mixtures of ENO, NOR and OFLO, in urine samples at biological levels without sample pretreatments. The resolution ability of N-way partial least squares (N-PLS), parallel factor analysis (PARAFAC) and self weighted alternating trilinear decomposition (SWATLD), is compared with partial least squares (PLS) and unfolded-PLS (U-PLS), in the analysis of ENO, NOR and OFLO in human urine samples.     

Simultaneous determination of 6-methylcoumarin and 7-methoxycoumarin in cosmetics using three-dimensional excitation-emission matrix fluorescence coupled with second-order calibration methods

This paper reports a simple, rapid, and effective method for quantitative analysis of 6-methylcoumarin (6-MC) and 7-methoxycoumarin (7-MOC) in cosmetics using excitation–emission matrix (EEM) fluorescence coupled with second-order calibration. After simple pretreatments, the adopted calibration algorithms exploiting the second-order advantage, i.e., parallel factor analysis (PARAFAC) and self-weighted alternating tri-linear decomposition (SWATLD), could allow the individual concentrations of the analytes of interest to be predicted even in the presence of uncalibrated interferences. In the analysis of facial spray, with the external calibration method, the average recoveries attained from PARAFAC and SWATLD with the factor number of 3 (N = 3) were 101.4 ± 5.5 and 97.5 ± 4.1% for 6-MC, and 103.3 ± 1.7 and 101.7 ± 1.8% for 7-MOC, respectively. Moreover, in the analysis of oil control nourishing toner, the standard addition method (SAM) was suggested to overcome the partial fluorescence quenching of 6-MC induced by the analyte–background interaction, which also yielded satisfactory prediction results. In addition, the accuracy of the two algorithms was also evaluated through elliptical joint confidence region (EJCR) tests as well as figures of merit (FOM), including sensitivity (SEN), selectivity (SEL) and limit of detection (LOD). It was found that both algorithms could give accurate results, only the performance of SWATLD was slightly better than that of PARAFAC in the cases suffering from matrix effects. The method proposed lights a new avenue to determine quantitatively 6-MC and 7-MOC in cosmetics, and may hold great potential to be extended as a promising alternative for more practical applications in cosmetic quality control, due to its advantages of easy sample pretreatment, non-toxic and non-destructive analysis, and accurate spectral resolution and concentration prediction.     

交替拟合残差算法与高效液相色谱-二极管阵列检测方法结合同时测定两种抗结核药物

本文利用化学计量学交替拟合残差(AFR)算法与高效液相色谱-二极管阵列检测(HPLC-DAD)方法相结合,同时测定两种抗结核药物异烟肼和吡嗪酰胺的含量。该法与交替三线性分解算法(ATLD)、自加权交替三线性分解(SWATLD)算法相比较,从预测均方差、预测相对误差以及平均回收率等结果来看,其预测结果更接近实际值。研究表明,基于交替拟合残差等算法的二阶校正法,可以迅速准确地给出色谱重叠情况下两个组分的预测结果,是复杂体系成分直接定量分析的一个有力的化学计量学工具。     

Simultaneous determination of tyrosine and dopamine in urine samples using excitation-emission matrix fluorescence coupled with second-order calibration

A "green" and quick analytical method for complex compounds was developed for simultaneous determination of tyrosine (Tyr) and dopamine (DA) in urine samples in this paper. The three-way responsive data recorded by excitation-emission matrix fluorescence (EEM) spectrometer was analyzed using second-order calibration methods based on both parallel factor analysis (PARAFAC) and selfweighted alternating trilinear decomposition (SWATLD) algorithms. The EEM spectra of the analytes were overlapped with the background in urine samples. However the second-order advantage of both PARAFAC and SWATLD methods was exploited, even in the presence of unknown interferences and the satisfactory results can be obtained. Furthermore, the linear ranges of Tyr and DA were determined to be 0.042-6.42 μg/mL and 0.18-4.43 μmg/mL, respectively, and the accuracies of both methods were validated by the analytical figures of merit (FOM).     

三维荧光校正法直接测定尿液中的利血平

利用化学计量学三维数据校正方法中的交替三线性分解算法(ATLD)和自加权交替三线性分解算法(SWATLD), 不经化学分离, 对采用激发-发射矩阵荧光法所得到的三维响应数据阵进行三线性成分分解, 再基于标样已知浓度, 利用简单回归法直接测定尿液中利血平(Reserpine)的含量. 结果表明, 当体系的主要组分数取3时, 两种方法均可迅速、 快捷地得到待测物的浓度, 有效地解决了荧光法定量测定时未知背景及干扰物光谱严重重叠而引起的问题.     

Identification and quantification of carbamate pesticides in dried lime tree flowers by means of excitation-emission molecular fluorescence and parallel factor analysis when quenching effect exists

A non-separative, fast and inexpensive spectrofluorimetric method based on the second order calibration of excitation-emission fluorescence matrices (EEMs) was proposed for the determination of carbaryl, carbendazim and 1-naphthol in dried lime tree flowers. The trilinearity property of three-way data was used to handle the intrinsic fluorescence of lime flowers and the difference in the fluorescence intensity of each analyte. It also made possible to identify unequivocally each analyte. Trilinearity of the data tensor guarantees the uniqueness of the solution obtained through parallel factor analysis (PARAFAC), so the factors of the decomposition match up with the analytes. In addition, an experimental procedure was proposed to identify, with three-way data, the quenching effect produced by the fluorophores of the lime flowers. This procedure also enabled the selection of the adequate dilution of the lime flowers extract to minimize the quenching effect so the three analytes can be quantified. Finally, the analytes were determined using the standard addition method for a calibration whose standards were chosen with a D-optimal design.