Multivariate monitoring of soybean oil ethanolysis by FTIR

In this work, an analytical procedure was developed to monitor the ethanolysis of degummed soybean oil (DSO) using Fourier-transformed mid-infrared spectroscopy (FTIR) and methods of multivariate analysis such as principal component analysis (PCA) and partial least squares regression (PLS). The triglycerides (reagents) and ethyl esters (products) involved in ethanolysis were shown to have similar FTIR spectra. However, when the FTIR spectra derived from seven standard mixtures of triolein and ethyl oleate were treated by PCA at the region that represents the CO stretching vibration of ester groups (1700-1800 cm⁻¹), only two principal components (PC) were shown to capture 99.95% of the total spectral variance (92.37% for the former and 7.58% for the latter PC). This observation supported the development of a multivariate calibration model that was based on the PLS regression of the FTIR data. The prevision capability of this model was measured against 40 reaction aliquots whose ester content was previously determined by size exclusion chromatography. Only small discrepancies were observed when the two experimental data sets were treated by linear regression (R²=0.9837) and these deviations were attributed to the occurrence of non-modeled transient species in the reaction mixture (reaction intermediates), particularly at short reaction times. Therefore, the FTIR/PLS model was shown to be a fast and accurate method to predict reaction yields and to follow the in situ kinetics of soybean oil ethanolysis.     

Performance validation of step-isothermal calorimeters

Isothermal calorimetry is becoming indispensable as a tool for the study of a wide variety of systems. As with all scientific instruments it is essential that robust calibration routines be developed in order to validate the data obtained. Chemical test reactions offer many advantages over (the traditionally used) joule effect heating methods, not least because they have the potential to validate instrument performance (i.e. they can be used to assess all aspects of calorimeter operation). In this work the results of a validation exercise, conducted by Thermal Hazard Technology as part of an installation routine, using the base catalysed hydrolysis of methyl paraben are discussed. In the case described, a systematic misreporting of the reported temperature of a calorimeter was identified, caused by an upgrade to the calorimeter's firmware, a discrepancy which may not have been noted using traditional electrical calibration methods and one which highlights the importance of both manufacturers and end-users adopting chemical test reactions into their test and validation routines.     

Simultaneous determination of albumin and immunoglobulin G with fluorescence spectroscopy and multivariate calibration

A method is proposed for the simultaneous determination of albumin and immunoglobulin G (IgG1) with fluorescence spectroscopy and multivariate calibration with partial least squares regression (PLS). The influence of some instrumental parameters were investigated with two experimental designs comprising 19 and 11 experiments, respectively. The investigated parameters were excitation and emission slit, detection voltage and scan rate. When a suitable instrumental setting had been found, a minor calibration and test set were analysed and evaluated. Thereafter, a larger calibration of albumin and IgG1 was made out of 26 samples (0-42 μg ml⁻¹ albumin and 0-12.7 μg ml⁻¹ IgG1). This calibration was validated with a test set consisting of 14 samples in the same concentration range. The precision of the method was estimated by analysing two test set samples for six times each. The scan modes tested were emission scan and synchronous scan Δ60 nm. The results showed that the method could be used for determination of albumin and IgG1 (albumin, root mean square error of prediction (RMSEP) <2, relative standard error of prediction (RSEP) <6% and IgG1, RMSEP <1, RSEP <8%) in spite of the overlapping fluorescence of the two compounds. The estimated precision was relative standard deviation (R.S.D.) <1.7%. The method was finally applied for the analysis of some sample fractions from an albumin standard used in affinity chromatography.     

便携式温度计校验仪的研制

介绍便携式温度计校验仪的工作原理及研制过程。对该仪器的恒温槽体机械结构、制冷器和散热器的设计、恒温槽体温度测量及控制等进行了详细叙述。该仪器提供的温度场稳定、均匀，在-20～100℃范围内可任意设定温度。解决了温度计现场快速校准的问题。     

Limit of detection estimator for second-order bilinear calibration

A new approach is developed for estimating the limit of detection in second-order bilinear calibration with the generalized rank annihilation method (GRAM). The proposed estimator is based on recently derived expressions for prediction variance and bias. It follows the latest IUPAC recommendations in the sense that it concisely accounts for the probabilities of committing both types I and II errors, i.e. false positive and false negative declarations, respectively. The estimator has been extensively validated with simulated data, yielding promising results.     

Calorimetric study of the immersion heats of lead(II) and chromium(VI) from aqueous solutions of Colombian coffee husk

Summary This work shows the result of the study of the Pb(II) and Cr(VI) ions adsorption by means of a Calvet type calorimeter of heat conduction that can operate at 150şC. The calorimeter was electrically calibrated to establish its sensitivity and reproducibility, obtaining K=12.95±0.05 W V^-1 and chemically it was examined with tris-(hydroxymethyl)-aminomethane (THAM)-HCl system, obtaining ΔH= -30.91±0.03 kJ mol^-1. The activated carbon sample obtained from coffee husk and the calorimetric results obtained were related to other techniques used to perform this type of studies.     

Estimation of the uncertainty of mass measurements from in-house calibrated analytical balances

The uncertainty evaluation of mass measurements when using “in-house” calibrated analytical balances is revisited according to the Guide to the expression of Uncertainty Measurement (GUM). The calibration of analytical balances is discussed according to the guidelines of several bodies such as ASTM, UKAS and DKD/PTB. The remainder components of uncertainty can be estimated from the balance data sheet specifications.     

凝胶渗透色谱法测定聚丙烯腈共聚物分子量中宽分布校正法的应用

应用宽分布校正法对凝胶渗透色谱(GPC)进行了校正，将校正曲线用于聚丙烯腈(PAN)共聚物分子量的计算。对扣除色谱峰扩展效应前后的测试结果与乌氏粘度法测得的数据进行比较。结果表明，应用宽分布校正法时，必须扣除色谱峰扩展效应，才能得到较为准确的测试结果。     

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.     

Calibration coefficient of a heat-flow DSC; Part II. Optimal calibration procedure

One-point (Mettler) and many-point (Netzsch) heat flow calibration of a DSC is discussed. It is shown that the two types of calibration are the alternative extremes between quick but rough procedure and time-consuming but accurate one. One-point calibration compares a typical function k(T) at the melting point of indium with the measured value for particular DSC and multiplies k(T) by a scaling factor. Many-point calibration is based on general mathematical procedure, namely fitting a set of experimental values of sensitivity to a polynomial. The polynomial coefficients are evaluated by the method of least squares. Based on the relationship between the sensitivity of a thermocouple and calibration coefficient of a DSC sensor made from it, two-point heat flow calibration is suggested. This is an optimal calibration procedure, for the relationship contains only two unknown coefficients. An example of how to perform the two-point calibration with Netzsch-Proteus Software is described in the Appendix.