An homologous series of benzodiazepine retention index standards for gas chromatography

An homologous series of benzodiazepine retention index standards (the R-series) has been synthesized and the gas chromatographic behavior of the series investigated on NB-54 and NB-1701 capillary columns. The compounds were stable, exhibited symmetrical peak shapes, and fairly linear retention behavior was observed on both columns. The series can be coinjected with every sample to enable the high precision analysis of toxicological samples; screening for 20 benzodiazepine drugs was possible in 23 minutes (including cooling). The R-series method was compared with a retention index method based on a series of benzodiazepine drugs as standards and with a method employing relative retention times. The precision of the R-series method was found to be generally better than that of the two other methods in both long- and short-term studies.     

药物RP-HPLC保留值的标准化方法──保留指数系统研究

以烷烃甲基酮类作为标准参照物,建立了反相高效液相色谱(RP-HPLC)的保留指数系统,并探讨了流动相、有机修饰剂浓度对保留指数的影响。这种RP-HPLC保留数据标准化方法可以减小RP-HPLC保留值的变异性。药物保留指数随色谱条件变化改变较小,可在实验室间进行比较。该系列参照物不仅可用于紫外检测系统,还可用于示差折光检测系统,本文所建立的RP-HPLC保留指数系统已在ODS和苯基柱上测定了70多种药物及其代谢物。     

Evaluation of hydrophobic interaction between acidic drugs and bovine serum albumin by reversed-phase high-performance liquid chromatography

The contribution of hydrophobic interaction to the protein binding of acidic drugs has been evaluated in terms of a new hydrophobic index (r-value), defined as the slope of the log-log plots of capacity factor vs. reciprocal of methanol concentration in an aqueous binary mobile phase, measured by the reversed-phase high-performance liquid chromatography. The logarithms of the binding constants (log K1) of the selected acidic drugs and the related aromatic carboxylic acids indicated linear relationship with their r-values, suggesting that the effect of hydrophobicity on protein binding can be explained similarly to that on the retention onto the reversed-phase stationary ligand.     

An overview on the standardization of chromatographic methods for screening analysis in toxicology by means of retention indices and secondary standards

Summary A review is presented on the methods of standardization of HPLC data as used in systematic toxicological analysis. In straight-phase HPLC, the best results were obtained with a series of selected drugs as retention standards. In reversed-phase HPLC, various retention index systems were introduced. However, these systems alone cannot compensate large differences in selectivities of nominally identical, but commercially different reversed-phase column packings. Much better results were achieved with selected drugs as retention index markers. The practical applicability of such a standardized HPLC system is demonstrated.Part I see [1]Dedicated to Prof. Dr. Dr. Marika Geldmacher-von Mallinckrodt in recognition of her pioneering contributions in clinical and forensic toxicology     

The advantage of dual-column approach and retention indices combined with refined reporting in gas chromatographic drug screening

A dual-column gas chromatographic retention index method was evaluated for the toxicological screening for basic drugs in autopsy blood samples. The dual-column approach with DB-5 and DB-1701 capillary columns doubles the Identification Power of the corresponding single column methods. The long-term intralaboratory variation of the dialkylfluoroaniline series based retention indices of drugs in blood ranged from 0.03% to 0.2% which was generally better than that obtained using the relative retention time. Novel software is described for the processing and reporting of the dual-column chromatographic data in analytically useful form. Besides retention data, the response factors served as an additional identification factor.     

The system of universal retention indices and aspects of its application in gas chromatography

Summary The universal retention index has been developed on the basis of a critical analysis of the forms of chromatographic retention data presentation. Methods are presented for the determination of the universal retention index. The advantages of the universal retention index system in the evaluation of the selectivity and classification of stationary phases and in the determination of the composition of binary and polynary stationary phases are discussed. The thermodynamic aspect of the suggested system of chromatographic retention data presentation is also considered.     

Collection of analytical data for benzodiazepines and benzophenones

On April 1st, 1986, amendments were made to Schedule 2 to the Misuse of Drugs Act 1971 such that 33 benzodiazepines became controlled as Class C drugs in the U.K. An analytical database has been prepared to aid the detection and identification of controlled benzodiazepines. Chromatographic properties have been measured including gas chromatography (GC) retention index values, high-performance liquid chromatography (HPLC) capacity factors and thin-layer chromatography (TLC) RF x 100 values. UV spectroscopic and mass spectrometric (MS) data have also been recorded. Analytical data (GC, TLC and MS) are also presented for benzophenones which were produced by acid hydrolysis of the parent benzodiazepines.     

Determination of the lipophilicity of some anti-hypoxia drugs: Comparison of TLC and HPLC methods

Summary The lipophilicity of 14 anti-hypoxia drugs has been determined by reversed phase thin-layer (RPTLC) and reversed phase high performance liquid chromatography (RPHPLC) in eluent systems containing different concentrations of acetonitrile and potassium dihydrogen phosphate. There was significant correlation between lipophilicity and the specific hydrophobic surface area of the drugs in RPTLC, indicating that the drugs behave as an homologous series of compounds. In RPTLC the concentration of buffer has a negligible effect on the retention of the drugs whereas in RPHPLC the buffer concentration influenced the retention. This discrepancy can be explained by the lower sensitivity of RPTLC. There was strong correlation between lipophilicity values determined by both methods, proving that both are suitable for the determination of molecular lipophilicity.     

Fast gradient elution reversed-phase liquid chromatography with diode-array detection as a high-throughput screening method for drugs of abuse. II. Data analysis

In Part I of this work, we developed a method for the detection of drugs of abuse in biological samples based on fast gradient elution liquid-chromatography coupled with diode array spectroscopic detection (LC-DAD). In this part of the work, we apply the chemometric method of target factor analysis (TFA) to the chromatograms. This algorithm identifies the target compounds present in chromatograms based on a spectral library, resolves nearly co-eluting components, and differentiates between drugs with similar spectra. The ability to resolve highly overlapped peaks using the spectral data afforded by the DAD is what distinguishes the present method from conventional library searching methods. Our library has a mean list length (MLL) of 1.255 and a discriminating power of 0.997 when both retention index and spectral factors are considered. The algorithm compares a library of 47 different compounds of toxicological relevance to unknown samples and identifies which compounds are present based on spectral and retention index matching. The application of a corrected retention index for identification rather than raw retention times compensates for long-term and column-to-column retention time shifts and allows for the use of a single library of spectral and retention data. Training data sets were used to establish the search and identification parameters of the method. A validation data set of 70 chromatograms was used to calculate the sensitivity (correct identification of positives) and specificity (correct identification of negatives) of the method, which were found to be 92% and 94%, respectively.     

酸性药物在微乳液相色谱体系中的保留行为

以酸性药物萘普生、布洛芬、双氯芬酸、苯丙氨酸和2,4-二氯苯氧基乙酸为研究对象,探讨了酸性药物在微乳液相色谱体系中保留机理,建立了酸性药物的容量因子(k′)与表面活性剂浓度、助表面活性剂浓度、亲脂性有机溶剂浓度以及流动相pH值之间的相关模型。结果表明,表面活性剂、助表面活性剂和亲脂性有机溶剂的浓度以及流动相pH值的变化对酸性药物的容量因子的影响完全与理论模型相吻合。所建立的保留模型能较好地反映在微乳液相色谱体系中微乳液组成和pH值对酸性药物保留行为的影响。     

非等间隔PCBs保留指数体系在光解行为研究中的应用

利用Ｃｈｕ等已建立的多氯联苯（ＰＣＢｓ）非等间隔保留指数体系,由文献中的相对保留时间计算出全部２０９种ＰＣＢｓ同类物（Ｃｏｎｇｅｎｅｒ）的保留指数（ＩＰＣＢ）。利用ＩＰＣＢ结合ＧＣ－ＭＳ对ＰＣＢ８７、ＰＣＢ１３８和ＰＣＢ１６９三种同类物的光解产物进行了定性分析,发现其光解产物主要为低氯代联苯。实验结果证明,非等间隔保留指数体系ＩＰＣＢ在ＰＣＢｓ同类物的定性分析中具有准确、实用、快捷、方便等优点。     

High-pressure liquid chromatography of drugs: II. An evaluation of a microparticulate cation-exchange column

A microparticulate cation-exchange column has been evaluated for the chromatography of thirty compounds selected as representative of a wide variety of drug substances. Although the column exhibited a strong partition effect besides the expected ion-exchange mechanism, the retention of drugs could be predictably influenced by variation of the eluent ionic strength and organic solvent content.

For acidic drugs the column showed little selectivity (although a salting-out effect increased retention at high eluent ionic strengths), but for basic substances Partisil SCX may afford a useful separative medium offering reasonable chromatographic efficiency (HETP ≈ 0.1 mm). The column longevity, however, is at present questionable.     

Use of a novel cation-exchange restricted-access material for automated sample clean-up prior to the determination of basic drugs in plasma by liquid chromatography

A new kind of silica-based restricted-access material (RAM) has been tested in pre-columns for the on-line solid-phase extraction (SPE) of basic drugs from directly injected plasma samples before their quantitative analysis by reversed-phase liquid chromatography (LC), using the column switching technique. The outer surface of the porous RAM particlescontains hydrophilic diol groups while sulphonic acid groups are bound to the internal surface, which gives the sorbent the properties of a strong cation exchanger towards low molecular mass compounds. Macromolecules such as proteins have no access to the internal surface of the pre-column due to their exclusion from the pores and are then flushed directly out. The retention capability of this novel packing material has been tested for some hydrophilic basic drugs, such as atropine, fenoterol, ipratropium, procaine, sotalol and terbutaline, used as model compounds. The influence of the composition of the washing liquid on the retention of the analytes in the pre-column has been investigated. The elution profiles of the different compounds and the plasma matrix as well as the time needed for the transfer of the analytes from the pre-column to the analytical column were determined in order to deduce the most suitable conditions for the clean-up step and develop on-line methods for the LC determination of these compounds in plasma. The cationic exchange sorbent was also compared to another RAM, namely RP-18 ADS (alkyl diol silica) sorbent with respect to retention capability towards basic analytes.     

模拟生物膜色谱用于预测药物的小肠吸收

采用涂敷磷脂的硅胶为模拟生物膜色谱固定相,与传统的凝胶体相比固定相的机械强度及磷脂固载能力均有较大提高,且有较好的稳定性。研究发现氢化可的松等6种药物在模拟生物膜色谱上pH5.4、pH7.0及pH7.4三种缓冲环境下的色谱保留值迭加的结果能够与药物的肠吸收指数押送好的拟合,线性相关系数为0.9365,该结果高于单一pH条件下拟合结果,并将此结果与药物在C18反相色谱上的保留值及辛醇-水系统下的分配系数与药物的小肠吸收的拟合结果进行比较,表明与这两种模型相比模拟生物膜色谱预测药物的小肠吸收有更高的准确度。     

An accurate and easy procedure to obtain isothermal Kováts retention indices in gas chromatography

Isothermal Kováts retention indices may be used in GC for identification purposes, but they are also useful in characterisation of stationary phases and for studying structural and physico-chemical properties of both the analyte and the stationary phase. They are currently reported as whole numbers with an accuracy of one index unit for non-polar stationary phases. The method recommended for their calculation uses a linear regression model, although non-linear models have also been applied with good results. In both cases, a computer programme and the retention times of a series of n-alkanes that elute correctly and resolved from the other compounds are needed, conditions which cannot always be fulfilled. However, it is possible to calculate retention indices with an accuracy of 0.1 retention index units (0.2 units for packed columns) with the help of only three n-alkanes using just a pocket calculator or a computer spreadsheet. The main requirement is that at least one of the n-alkanes has a retention index differing by no more than one hundred retention index units from that of the analyte being investigated. Examples are given for different stationary phases.     

High-performance liquid chromatography systems for the separation of benzodiazepines and their metabolites

The high-performance liquid chromatographic (HPLC) retention characteristics of 21 benzodiazepine drugs and some of their metabolites have been examined on both silica and ODS-silica packing materials. Four HPLC systems have been considered and retention data are presented for the drugs on these systems. The correlation of retention data on the systems is considered with reference to the problem of identifying unknown benzodiazepines.     

广义α_N指数及其应用 Ⅲ.酸性磷类和中性磷类萃取剂的广义α_N指数与其物理性质的相关分析

本文将化合物的α_N指数扩展为广义α_N指数,并将其用于一些酸性和中性磷类萃取剂的纸上层析,比移值,校正保留时间,保留指数,纸上电泳泳动值及分子折射度等物理化学性质的相关性研究,取得了满意的结果。     

Application of retention indices based on the alkylarylketone scale to the separation of the local anaesthetic drugs by high-performance liquid chromatography

The separation of the local anaesthetic drugs by reversed-phase high-performance liquid chromatography using a Hypersil ODS column has been examined in order to identify critical factors in the establishment of a retention database for interlaboratory comparisons. An eluent of methanol-aqueous orthophosphoric acid (15:85, v/v) (pH 2.5) containing 0.7% hexylamine has been used. The effects of small changes in the eluent composition, pH, temperature and the use of different column packing materials on the retentions of the analytes have been studied. The use of capacity factors, relative capacity factors and retention indices based on the alkylarylketone scale have been compared.