Simple automated generation of gradient elution conditions in sequential injection chromatography using monolithic column

The paper deals with the concept of simple automated creation of gradient profile of the mobile phase for gradient-elution sequential injection chromatography (GE-SIC). The feasibility and merits of this concept are demonstrated on the separation and simultaneous assay of indomethacin as active principle and of its two degradation products (5-methoxy-2-methylindoleacetic acid and 4-chloro-benzoic acid) in a topical pharmaceutical formulation.The GE-SIC separation was performed with a FIAlab^® 3000 SIC set-up (USA) equipped with an Onyx™ Monolithic C18 (25 mm × 4.6 mm, Phenomenex^®) column, a six-port selection valve, a 5-mL syringe pump and a fiber-optics UV CCD detector. Ketoprofen was used as an internal standard (IS). The gradient elution was achieved by automated reproducible mixing of acetonitrile and aqueous 0.2% phosphoric acid in the holding coil of the SIC system. Different profiles of the gradient elution were tested. The optimal gradient using two mobile phases 30:70 and 50:50 of acetonitrile/0.2% phosphoric acid (v/v) was achieved under the optimum flow rate 1.2 mL min⁻¹. The chromatographic resolution R between the peaks of all solutes (including the IS) was >2.00. The repeatability of retention times was characterized by the RSD values 0.18-0.30% (n = 6). Net separation time was 3.5 min and the mobile phase consumption was 4.5 mL for a single GE-SIC assay. The figures of merit of the novel GE-SIC method compared well with those of conventional HPLC.     

Multivariate analysis of remote laser-induced breakdown spectroscopy spectra using partial least squares,principal component analysis,and related techniques

Quantitative analysis with laser-induced breakdown spectroscopy traditionally employs calibration curves that are complicated by chemical matrix effects. These chemical matrix effects influence the laser-induced breakdown spectroscopy plasma and the ratio of elemental composition to elemental emission line intensity. Consequently, laser-induced breakdown spectroscopy calibration typically requires a priori knowledge of the unknown, in order for a series of calibration standards similar to the unknown to be employed. In this paper, three new Multivariate Analysis techniques are employed to analyze the laser-induced breakdown spectroscopy spectra of 18 disparate igneous and highly-metamorphosed rock samples. Partial Least Squares analysis is used to generate a calibration model from which unknown samples can be analyzed. Principal Components Analysis and Soft Independent Modeling of Class Analogy are employed to generate a model and predict the rock type of the samples. These Multivariate Analysis techniques appear to exploit the matrix effects associated with the chemistries of these 18 samples.     

Modeling gradient elution in countercurrent chromatography: efficient separation of tanshinones from Salvia miltiorrhiza Bunge

Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifugal fields to hold the liquid stationary phase. CCC has been widely applied in the separation of various natural and synthetic components using a variety of biphasic liquid systems. The related hexane or heptane/ethyl acetate/methanol or ethanol/water biphasic liquid systems demonstrated their significance in CCC. Gradient is difficult in CCC since any composition change in one phase induces a composition change of the other phase to maintain phase equilibrium. This work provides a new insight into linear gradient elution in CCC that is feasible with some biphasic liquid systems such as selected compositions of the hexane/ethyl acetate/ethanol/water systems. The equations modeling solute motion inside the CCC column are proposed. Particular compositions of the liquid system, namely the hexane/ethyl acetate/ethanol/water 8:2:E:W compositions with E + W = 10, were studied from W = 1 to 9. They showed moderate changes in the upper organic phase compositions. The model is tested with the separation of tanshinones from the rhizome of Salvia miltiorrhiza Bunge. Different linear solvent gradient profiles were experimentally performed between 8:2:5:5 and 8:2:3:7 compositions and the results were evaluated using the proposed model. Five tanshinones including dihydrotanshinone I, cryptotanshinone, tanshinone I, 1,2-dihydrotanshinquinone, and tanshinone IIA have been successfully separated (>95% purities) using a gradient profile optimized by the developed model. The gradient model can be used only with biphasic liquid systems in which one phase shows minimum composition changes when the other phase composition changes notably. This case is not the general case for biphasic liquid systems but can be applied with specific compositions of the quaternary hexane or heptane/ethyl acetate/methanol or ethanol/water most useful CCC liquid systems.     

Ion-exclusion chromatography with the direct UV detection of non-absorbing inorganic cations using an anion-exchange conversion column in the iodide-form

An ion-exclusion chromatographic method for the direct UV detection of non-absorbing inorganic cations such as sodium (Na⁺), ammonium (NH₄⁺) and hydrazine (N₂H₅⁺) ions was developed by connecting an anion-exchange column in the I⁻-form after the separation column. For example, NH₄⁺ is converted to a UV-absorbing molecule, NH₄I, by the anion-exchange column in the I⁻-form after the ion-exclusion separation on anion-exchange column in the OH⁻-form with water eluent. As a result, the direct UV detection of Na⁺, NH₄⁺ and N₂H₅⁺ could be successfully obtained as well as the well-resolved separation. The calibration graphs of the analyte cations detected with UV at 230 nm were linear in the range of 0.001-5.0 mM. The detection limits at S/N = 3 of the cations were below 0.1 μM. This method was applied to real water analysis, the determination of NH₄⁺ in river and rain waters, or that of N₂H₅⁺ in boiler water, with the satisfactory results. This could be applied also to low- or non-absorbing anions such as fluoride or hydrogencarbonate ions by the combination of a weakly acidic cation-exchange resin in the H⁺-form as the separation column and the anion-exchange conversion column.     

紫外分光光度法测定12种药材中的微量硒

采用紫外分光光度法，以邻苯二胺为显色剂测定了12种药材中微量硒的含量。本法回收率为98．95％，变异系数1．34％．     

硅胶整体柱离子对色谱快速分析碘离子

建立了用硅胶整体柱和直接电导检测的离子对色谱快速分析碘离子的方法。采用Chromolith Speed ROD RP-18e色谱柱,以氢氧化四丁铵(离子对试剂)-邻苯二甲酸+乙腈(有机改进剂)为淋洗液,讨论了离子对试剂浓度、有机改进剂浓度、pH、流速和色谱柱温度对碘离子保留的影响。确定最佳色谱条件为:0.25 mmol/L氢氧化四丁铵-0.18 mmol/L邻苯二甲酸+体积分数7%乙腈(pH5.5)作为淋洗液,流速6.0 mL/min,色谱柱温30℃。在此条件下,碘离子的保留时间在0.5 min之内,其它常见阴离子(Cl-、NO3-、SO42-)及SCN-、ClO4-不干扰测定。方法的检出限为0.86 mg/L,标准曲线的线性范围为1.6～85.0 mg/L,峰面积的相对标准偏差为2.3%。将方法应用于测定地下水和果汁中的碘离子,加标回收率为98.5%～104.2%。     

Rapid analysis of triazolopyrimidine sulfoanilide herbicides in waters and soils by high-performance liquid chromatography with UV detection using a C18 monolithic column

In this work, the simultaneous analysis of five triazolopyrimidine sulfoanilide herbicides (flumetsulam, florasulam, metosulam, cloransulam-methyl, and diclosulam) by HPLC using UV detection and a C18 monolithic column is proposed. The mobile phase which was composed of ACN, water, and formic acid was pumped at a high flow rate (5 mmL/min) providing an analysis time of all the compounds in less than 2.3 min. The LODs were in the low microg/L range (i.e. between 60 microg/L for flumetsulam and 90 microg/L for florasulam) and the calibration curves showed good linearity (R2 > 0.9949). The method was applied to the analysis of these compounds in spiked mineral and tap waters and soils after an SPE preconcentration procedure using C18 cartridges. Mean recovery values ranged between 35 and 110% for water samples providing LODs of the whole procedure in the low ng/L level, down to 280 ng/L, and between 77 and 92% for soil samples with LODs down to 9.38 microg/kg. This is the first time that this family of pesticides is simultaneously analyzed in both types of samples by HPLC and also using a monolithic column.     

Purification of compounds from Lignum Dalbergia Odorifera using two-dimensional preparative chromatography with Click oligo (ethylene glycol) and C18 column

Purification of compounds from traditional Chinese medicines (TCMs) is an important task for understanding the chemical composition of TCMs. However, it is difficult to obtain compounds with high enough purity for identification by NMR due to the complexity of TCMs in chemical composition. In this study, a two‐dimensional purification method based on a Click oligo (ethylene glycol) column and a C18 column was developed to realize an orthogonal separation in preparative level for purifying compounds efficiently. The first dimensional preparation was performed on a Click oligo (ethylene glycol) column to simplify the sample into the fractions with good separation repeatability. On the first dimension, 7.2 g sample was separated into 11 fractions with a recovery of 86% within 6 h. A C18 column was taken as the second dimension to realize the high‐performance separation and rapid preparation from the fractions collected from the first dimension. Eight compounds in fraction 6 and 2 compounds in fraction 8 were isolated and identified after optimizing the separation and collection parameters. This method is a high‐efficient and orthogonal preparation method to improve the separation of a complex sample and increase the purity of the compounds, which benefits from the application of novel materials in the preparation and purification.     

Classification of polymer batch variations by dynamic headspace/capillary gas chromatography/multivariate data analysis

Gas chromatographic profiles have been generated from different batches of a polypropylene/polyethylene copolymer. The profiles generated from polymer pellets have been obtained by dynamic headspace/capillary gas chromatography analysis. Initially 10 to 40 peaks were chosen at random from the quantitative reports and transferred to a data table. After appropriate scaling the table has been analyzed by a multivariate statistic program, SIMCA (Soft Independent Modeling of Class Analogy) a pattern recognition technique. The method has been used to differentiate batches according to sensory qualities of the final packaging product and changes in polymer peilet production.     

Trace-level monitoring of chloroanilines in environmental waters using on-line trace-enrichment and liquid chromatography with UV and electrochemical detection

Summary An on-line procedure is described for the trace-level determination of mono-, di- and methyl-chloroanilines in aqueous samples using selective preconcentration with a cation-exchanger and liquid chromatography with UV and electrochemical detection. Because direct percolation through a cation-exchanger has to be avoided owing to the high content of inorganic anions present in natural waters, a two-step on-line preconcentration was carried out: chloroanilines were first trapped on a precolumn packed with an apolar polymeric sorbent (PRP-1) in their neutral form. Then the PRP-1 precolumn was coupled in series with a second precolumn containing cation exchange material. The chloroanilines were removed from the first precolumn with 3 mL of deionised water: acetonitrile (31) at pH 1 and retained by the cation exchange column. The contents of the cation exchange column were finally desorbed onto the analytical column and eluted with a water: acetonitrile gradient. The combination of selective trace enrichment and sensitive electrochemical detection allows the simultaneous determination of chloroanilines from 150 mL of river water samples with detection limits below 30 ng/l. Identification is confirmed by the selective preconcentration and the two detection modes.     

Rapid analysis of phthalic acid esters in environmental water using fast elution gas chromatography with mass spectrometry and adaptive library spectra

A method for the fast determination of the components in a complex sample by using gas chromatography with mass spectrometry was developed and used for the quantitative analysis of phthalic acid esters in environmental water. In the method, the adaptively corrected mass spectra were used to compensate for the differences between the library spectra and the measured ones in the experiment. The correction was obtained by the iterative transformation of the library spectra using iterative target transformation factor analysis, and the resolution was performed by non‐negative immune algorithm using the corrected spectra. Rapid analysis of 16 phthalic acid esters in water samples was achieved using fast elution gas chromatography with mass spectrometry measurements. The results show that the mass spectra and chromatographic profiles of the phthalic acid esters can be obtained from the overlapping signal of 13 min elution, and accurate quantitative analysis can be obtained. The recoveries of the phthalic acid esters obtained by standard addition are between 90.3 and 107.4%, and the relative standard deviations obtained in repeated measurements are less than 9%.     

Multivariate data analysis approach to understand magnetic properties of perovskite manganese oxides

Here we apply statistical multivariate data analysis techniques to obtain some insights into the complex structure-property relations in antiferromagnetic (AFM) and ferromagnetic (FM) manganese perovskite systems, AMnO₃. The 131 samples included in the present analyses are described by 21 crystal-structure or crystal-chemical (CS/CC) parameters. Principal component analysis (PCA), carried out separately for the AFM and FM compounds, is used to model and evaluate the various relationships among the magnetic properties and the various CS/CC parameters. Moreover, for the AFM compounds, PLS (partial least squares projections to latent structures) analysis is performed so as to predict the magnitude of the Néel temperature on the bases of the CS/CC parameters. Finally, so-called PLS-DA (PLS discriminant analysis) method is employed to find out the most influential/characteristic CS/CC parameters that differentiate the two classes of compounds from each other.     

Quantitative and qualitative analysis of triglycerides using gradient elution with UV detection

Summary A gradient reverse phase system is reported which was compatible with UV detection at 220 nm and was suitable for fats containing a wide range of carbon number.Cis andtrans isomers were well resolved and better precision was obtained for poly-unsaturated fats than by capillary GC. Diode array detection with an isocratic system enabled the absorbance ratio at 220/225 nm to be monitored and this appears to give a useful indication of the type of unsaturation present in eluted triglycerides.     

Quantitative determination of UV filters in sunscreen lotions using microemulsion electrokinetic chromatography

Microemulsion electrokinetic chromatography (MEEKC) has been applied to the separation of some UV filters (Eusolex 4360, Eusolex 6300, Eusolex OCR, Eusolex 2292, Eusolex 6007, Eusolex 9020, Eusolex HMS, Eusolex OS, and Eusolex 232) commonly used in sunscreen lotions. Use of a MEEKC buffer with a mixed surfactant system to stabilize the oil droplets and an organic modifier in the aqueous phase allowed separation of most of the selected analytes in a single run in a system fitted with a diode array detector recording three wavelengths (240 nm, 300 nm, and 380 nm) simultaneously. The microemulsion employed consisted of 2.25 g of SDS, 0.75 g of Brij 35, 6.6 g 1‐butanol, 0.8 g n‐octane, 17.5 g 2‐propanol, and 72.1 g of 10 mM borate buffer (pH 9.2). Detection limits from 0.65 to 6.0 μg/mL were obtained and the calibration plots were linear over at least one order of magnitude for all analytes. The developed method could be applied to the determination of UV filters in several sun protection products including lotions, milks, and oils. Comparison of the obtained data with those from an HPLC method described in the literature showed acceptable agreement.     

A new strategy based on cholesterol-functionalized iron oxide magnetic nanoparticles for determination of polycyclic aromatic hydrocarbons by high-performance liquid chromatography with cholesterol column

This study reported for the first time the use of cholesterol-functionalized magnetic nanoparticles (Fe₃O₄@SiO₂@Chol) for the determination of polycyclic aromatic hydrocarbons (PAHs) in traditional Chinese medicine samples (TCMs) by high performance liquid chromatography (HPLC) coupled with fluorescence detection. The method was efficient, environmentally friendly, and fast. The solvent consumption of the proposed column is only half of the conventional column but with higher efficiency. Influencing factors, including sorbent amount, desorption solvent, sample volume and extraction time, were investigated in detail. Under the optimum conditions, good linearity (R² > 0.991) was obtained over the range of 5–400 ng g⁻¹, with limits of detection (LOD) 0.75, 0.50, 1.0, 0.56, 0.60, 0.84 and 0.80 ng g⁻¹ for anthracene, fluoranthene, pyrene, chrysene, benzo[a]anthracene, benzo(b)fluoranthene and benzo(k)fluoranthene, respectively.     

Phytochemical analysis of traditional Chinese medicine using liquid chromatography coupled with mass spectrometry

Traditional Chinese medicine (TCM) is commonly considered to operate due to the synergistic effects of all the major and minor components in the medicines. Hence sensitive and comprehensive analytical techniques are needed to acquire a better understanding of the pharmacological basis of the herb and to enhance the product quality control. The present review mainly focuses on the phytochemical analysis of TCMs using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS). Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) are the two commonly used ion sources. Triple quadrupole, ion trap (IT), Fourier transform ion cyclotron resonance (FTICR) and time-of-flight (TOF) mass spectrometers are used as on-line analyzer. The relationship between structural features and fragmentation patterns should be investigated as thoroughly as possible and hence be applied in the on-line analysis to deduce the structures of detected peaks. Characteristic fragmentation behaviors of the reference standards, as well as information regarding polarity obtained from retention time data, on-line UV spectra, data from the literature and bio-sources of the compounds allowed the identification of the phytochemical constituents in the crude extracts. Although a mass spectrometer is not a universal detector, high-performance liquid chromatography coupled with multistage mass spectrometry (HPLC-MS(n)) technique was still proved to be a rapid and sensitive method to analyze the majority of the many constituents in herbal medicines, particularly for the detection of those present in minor or trace amounts. The methods established using HPLC-MS techniques facilitate the convenient and rapid quality control of traditional medicines and their pharmaceutical preparations. However, the quantitative analysis is not the topic of this review.     

Surface chemistry of lanthanum chromite powders II. Multivariate data modelling of the isoelectric point by the use of surface composition data achieved from X-ray photoelectron spectroscopy measurements

 Electrophoretic mobility measurements and X-ray photoelectron spectroscopy (XPS) analysis have been performed on several lanthanum chromite powders with different dopants. Principal component analysis of both deconvoluted XPS data and differentiated overall XPS spectra showed a clustering of the powders. From loading plots it was seen that high amounts of La and O on the surface gave highest isoelectric points (IEP). Partial-least-squares, multivariate response modelling was used to calibrate the IEPs from both deconvoluted XPS data and from differentiated overall XPS spectra. The best model was obtained when second-order differentiated overall XPS spectra were used, with an average predictive error of pH ± 0.25. This is promising considering that the IEP has been determined with an accuracy of pH_IEP± 0.3. When deconvoluted data was used, the average predictive error rose to pH ± 1.1. It is therefore an advantage to use multivariate data analysis which is a nonsubjective latent variable decomposing technique in contrast to deconvolution which is an even more time-consuming method for calibration of IEP values from XPS. Received: 8 October 1998 Accepted in revised form: 27 January 1999     

Static headspace‐multicapillary column with gas chromatography coupled to ion mobility spectrometry as a simple approach for the discrimination of crude and processed traditional Chinese medicines

The processing procedure can alter the nature and chemical transformation of traditional Chinese medicine to accommodate different clinical dispensing and preparation requirements. In this study, static headspace‐multicapillary column with gas chromatography coupled to ion mobility spectrometry was developed for the rapid and sensitive discrimination of crude and processed traditional Chinese medicine. Using Radix Paeoniae Alba as a traditional Chinese medicine model, the combined power of this approach was illustrated by classifying the crude and processed Radix Paeoniae Alba samples into two main categories. The contents of the main components in Radix Paeoniae Alba varied significantly. The established method could promote the use of ion mobility spectrometry in intrinsic quality control and differentiation of herbal medicines from other processed products or preparations.