Department of Chemistry, Faculty of Sciences, K.N. Toosi University of Technology, Tehran, Iran.
Spectrochim Acta A Mol Biomol Spectrosc. 2011 Jan;78(1):277-86. doi: 10.1016/j.saa.2010.10.007. Epub 2010 Oct 28.
Annihilation of the contribution of one chemical component from the original data matrix is a general method in rank annihilation factor analysis (RAFA). However, RAFA is not applicable for studying the protonation equilibria of multiprotic acids but in this study two-rank annihilation factor analysis (TRAFA) was used as an efficient chemometrics algorithm for determination of the protolytic constants (pKa) of tetracycline hydrochloride (TCHC) in some nonaqueous-water mixed solvents such as acetonitrile (AN)-water and methanol (MeOH)-water from the spectral pH-absorbance data. The spectral data was obtained from spectrophotometric acid-base titrations of different solutions of TCHC at (25.0±0.10)°C and an ionic strength of 0.10 M. In TRAFA algorithm the pKa values were obtained with relationship between residual standard deviation (R.S.D.) and hypothetical pKa values. In the case of TCHC, the spectra were divided in two consecutive subdivisions according to their pH range having two pKa and TRAFA was run twice. The validity of the obtained pKa values was checked with well-known chemometrics algorithms such as DATAN, EQUSPEC, SPECFIT/32 and SQUAD. The effects of changing solvent composition on the protolytic constants were explained by linear solvation energy relationships (LSER) utilizing solvatochromic parameters.
从原始数据矩阵中消除一个化学组分的贡献是秩消去因子分析（RAFA）的一种通用方法。然而，RAFA 不适用于研究多质子酸的质子化平衡，但在这项研究中，双秩消去因子分析（TRAFA）被用作一种有效的化学计量学算法，用于从光谱 pH-吸光度数据中确定盐酸四环素（TCHC）在一些非水-水混合溶剂中的质子化常数（pKa），如乙腈（AN）-水和甲醇（MeOH）-水。光谱数据是通过在（25.0±0.10）°C 和 0.10 M 离子强度下对 TCHC 的不同溶液进行分光光度酸碱滴定获得的。在 TRAFA 算法中，pKa 值是通过残余标准偏差（R.S.D.）与假设 pKa 值之间的关系获得的。在 TCHC 的情况下，根据其 pH 范围将光谱分为两个连续的子部分，具有两个 pKa 值，并进行了两次 TRAFA 运行。用 DATAN、EQUSPEC、SPECFIT/32 和 SQUAD 等知名化学计量学算法检查了所获得的 pKa 值的有效性。利用溶剂变色参数，通过线性溶剂化能关系（LSER）解释了溶剂组成变化对质子化常数的影响。
