Multivariate data analysis of quality parameters in drinking water

The quality of water destined for human consumption has been treated as a multivariate property. Since most of the quality parameters are obtained by applying analytical methods, the routine analytical laboratory (responsible for the accuracy of analytical data) has been treated as a process system for water quality estimation. Multivariate tools, based on principal component analysis (PCA) and partial least squares (PLS) regression, are used in the present paper to: (i) study the main factors of the latent data structure and (ii) characterize the water samples and the analytical methods in terms of multivariate quality control (MQC). Such tools could warn of both possible health risks related to anomalous sample composition and failures in the analytical methods.     

Flow system exploiting multicommutation to increase sample residence time for improved sensitivity. Simultaneous determination of ammonium and ortho-phosphate in natural water

A flow system for the simultaneous determination of ammonium and phosphate in river water at the mug ml(-1) level employing a low expensive LED-based photometer is described. The manifold of the flow system comprised four analytical pathways containg a set of three-way solenoid valves and an automatic injector commutator. The signal measurements of both analytes were carried out using two LED-based photometers attached to the flow cells. A microcomputer running a programme written in quickbasic 4.5 provided facilities to control the system and to carry out simultaneously two analytical procedures also performing data acquisition. For the determination of ortho-phosphate the method based on reaction with molybdate and ascorbic acid was employed, while for ammonium the method based on reaction with hypochlorite and salicylic acid was selected. The four-pathway structure of the manifold allowed the sample incubation time to be increased to 130 s to permit the reaction to occur without a decrease in sample throughput. The usefulness of the system was ascertained by analyzing a set of water samples. Applying the paired t-test to results obtained employing reference methods, no significant difference at the 95% confidence level was observed for both analytes. Other profitable features such as an analytical throughput of 112 analyte determination per hour; relative standard deviations of 1.1 and 0.7% (n=6) ammonium and phosphate, respectively, reagent consumption of 0.3 mg ammonium molybdate, 0.75 mg salicylic acid, 3.3 mg ascorbic acid and sodium hypochlorite per determination; detection limits of 7.0 mug l(-1) NH(4)(+) and 17.0 mug l(-1) PO(4)(3-) were also achieved.     

MSFIA-LOV system for Ra isolation and pre-concentration from water samples previous radiometric detection

An automatic system based on multisyringe flow injection analysis (MSFIA) and lab-on-valve (LOV) flow techniques for separation and pre-concentration of ²²⁶Ra from drinking and natural water samples has been developed. The analytical protocol combines two different procedures: the Ra adsorption on MnO₂ and the BaSO₄ co-precipitation, achieving more selectivity especially in water samples with low radium levels.     

Determination of lasalocid with sensitized terbium(III) luminescence detection

The luminescence of the lasalocid-terbium(III) system in the presence of Triton X-100 and trioctylphosphine oxide has been studied by obtaining kinetic and equilibrium measurements and using the stopped-flow mixing technique. The initial rate and luminescence signal of this system are directly proportional to the lasalocid concentration, which allows one to develop very simple, fast, automatic methods for the determination of this analyte. Kinetic and equilibrium data can be obtained in only 0.1 and 10 s, respectively. The calibration graphs were linear over the range 0.004-5.0 mug ml(-1) (kinetic method) and 0.01-5.0 mug ml(-1) (equilibrium method) and the detection limits achieved were 1 and 3 ng ml(-1), respectively, equivalent to 2 and 6 ng g(-1) lasalocid in a chicken liver sample, which are similar to those afforded by the chromatographic methods described for this determination. The relative standard deviation of both methods was close to 2%. The analytical recoveries obtained by applying the kinetic and equilibrium methods to drinking water, poultry feed and chicken liver samples ranged from 95.6 to 102.1% and from 95.9 to 104.9%, respectively.     

Recent trends in solid phase spectrometry: 2003-2009. A Review

Around 100 papers published from 2003 to the present are reviewed concerning analytical methods for the direct light measurement of a solid phase in which a target colored or fluorescent analyte is concentrated. Recent attention has been paid to the development of flow injection-solid phase spectrometry as a simple and inexpensive tool for routine analysis of organic compounds or pharmaceuticals. Due to some improvements in flow injection analysis, such as sequential injection and lab-on-a-valve, it is possible not only to reduce the reagent consumption but also to devise fully automatic and miniaturized systems with minimal maintenance needs. This may have the potential of becoming one of the green analytical methods. Flow injection-solid phase spectrometry is expected to be applied to the speciation of trace chemical components (e.g., specific determination of trace metal ions in different existent oxidation states) in real samples in the environment.     

Cooperative Study of Precision and Accuracy on the Determinations of Around-Ppb Levels of Copper and Lead in Environmental Waters

The results of a series of inter-laboratory cross-check on the determinations of ppb and sub-ppb levels of copper and lead in environmental samples are described. Thirteen laboratories participated during a five-stage comparison. Seven analytical methods and two pre-concentration procedures were performed on certified and real samples. For controlled and blind standards at higher concentration levels (10 ppb or above) the data reported by different participants show good agreement for both elements regardless of the method chosen. However, for samples having lower concentrations (1-10 ppb level), the relative standard deviation (R.S.D.) and bias increased. A high degree of scattering on data were demonstrated for a deep ocean water at less than 1 ppb level. The results of the present study give direct comparison between different analytical methods, and also reflect the average aptitude of analytical laboratories in Taiwan on the measurements of copper and lead in environmental samples.     

Determination of acidic drugs in sewage water by gas chromatography-mass spectrometry as tert.-butyldimethylsilyl derivatives

A procedure is described for the determination of five acidic non-steroidal anti-inflammatory pharmaceuticals (ibuprofen, naproxen, ketoprofen, tolfenamic acid and diclofenac) in sewage water. The analytical method involves the concentration of water samples using a solid-phase extraction polymeric sorbent, functionalized with N-vinylpyrrolidone. Analytes were eluted with ethyl acetate. derivatized using N-methyl-N-(tert.-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) and analyzed by GC-MS. Influence of time, temperature and volume of MTBSTFA in the yield of the derivatization step were studied in detail using a factorial central composite design. Quantification limits of the analytical procedure for 500 ml of sewage water ranged from 20 to 50 ng/l. Recoveries from 90 to 115% were found for sewage water samples spiked with the studied compounds at the low ng/ml level. Results obtained for real samples show the presence of ibuprofen and naproxen in both influent and effluent of a sewage water treatment plant.     

Determination of titratable acidity and ascorbic acid in fruit juices in continuous-flow systems

Summary Two continuous-flow systems for the determination of titratable acidity and ascrobic acid in fruit juice samples are described. The assemblies permit on-line dialysis of analytes prior to the reaction step, thus improving selectivity and performing sample dilution. Flow systems are built with a channel carrying the donor phase (sample in both determinations) and another channel carrying an acceptor phase, both of them entering the dialyser. The outcoming stream transporting the dialysed sample fills the valve loop, permitting its injection into a carrier stream which continuously passes through the spectrophotometric detector. For the titratable acidity, acceptor phase and carrier are distilled water, the reagent merged with the carrier channel being a buffered solution of bromothymol blue (pH 7). The analytical signal obtained is then monitored at 616 nm. For ascorbic acid, the acceptor phase was a Fe(III) solution, which reacts with the dialysed analyte to form Fe(II). A buffered solution of o-phenanthroline (pH 4.5) is used as carrier, reacting with Fe(II) to give the analytical signal, which is monitored at 510 nm. Chemical and physical parameters are optimized for both systems. The analytical features of the determination are established. Finally, the proposed procedures are compared with the official volumetric AOAC methods for both parameters. The FIA methods turn out to be suitable for a rapid and accurate control of fruit juice samples, compared with the reference methods; additionally they compete advantageously with the volumetric methods in the case of turbid and highly coloured samples.     

Monitoring of Sulfonamides by a Multicommutation Flow-Analysis Assembly: Use of Quenching Effect on Terbium Luminescence

Sulfonamide drugs are an important class of antimicrobial agents employed in both medicine and veterinary practice. Although there have been a variety of proposed analytical methods for their determination, many of them are not suitable for routine quality control, due to time-consuming procedures or expensive instrumentation. In this paper, we propose a simple methodology, based on the direct quenching effect produced by several sulfonamide compounds (sulfasalazine, sulfanilamide, and sulfamethoxazole) on the terbium (III) luminescence. The flow assembly was designed making use of the automatic methodology multicommutation, and the proposed method allowed the determination of up to 50 samples per hour.     

A computer program for ranking analytical methods according to their fitness for purpose

A program for conducting automatic searches for analytical methods, selecting the most suitable ones according to quality requirements, and ranking them based on quality indices calculated from various pre-selected quality parameters is proposed. The program uses an externally updated database (Analytical Abstracts CD-ROMs or other) and customised quality schemes based on accuracy, precision, sensitivity, applicability to real samples, determination range (ratio), throughput and impact factor (from the Citation Index). It can, therefore, be used for a variety of purposes in analytical chemistry.     

High‐throughput microscale extraction using ionic liquids and derivatives: A review

Ionic liquids and derivatives—mainly polymeric ionic liquids and magnetic ionic liquids—have been extensively used in microscale extraction over the past few years. Current trends in analytical sample preparation gear toward linking microextraction approaches with high‐throughput sample processing to comply with green analytical chemistry requirements. A variety of high sample throughput strategies that are coupled to both ionic‐liquid‐based solid‐phase microextraction and ionic liquid‐based liquid‐phase microextraction are herein reported. The review is focused on microscale extraction methods that use (i) custom‐made and dedicated extraction devices, (ii) parallel extraction, (iii) magnetic‐based separation, and (iv) miniaturized systems employing semi‐automatic or fully automatic flow injection methods, related micro/millifluidic devices, and robotic equipment.     

The effect of organic nitrogenous compound content and different pretreatments on agricultural lignocellulosic biomass characterization methods

Considering the diverse compounds contained in lignocellulosic biomasses, especially in agricultural biomass, and the complexity of the different chemical and physical structural connections between these compounds, appropriate analytical methods must be used to characterize these biomasses. In this study, two extraction processes and two analytical methods were used to characterize the main compounds in corn stover residue before and after different pretreatments. The results of this study suggest that pretreatment and organic nitrogenous compound content greatly affect the most common extraction processes and analytical methods used for biomass characterization. For raw corn stover biomass residue, the extraction process using neutral detergent fiber solvent removed more extractives and more organic nitrogenous compounds (18.5 and 2.4%, respectively) than the combination of extractions using water and ethanol (13.4% of extractives and 1.8% of organic nitrogenous compounds). This study also showed that the different pretreatments improve the efficiency of both extraction processes and that these processes seem to be more effective with the neutral detergent solvent extraction than the combination of extractions with water and ethanol. Organic nitrogenous compounds represent a significant proportion of agricultural biomasses; therefore, insufficient organic nitrogenous compound extraction can cause interference with different characterization methods. It was observed that, for the same analytical method and with the raw biomass, the value of insoluble lignin after the extractions with water and ethanol was higher than that obtained after the extraction with the neutral detergent solvent 16.1 and 13.2%, respectively. This can be explained by the fact that there are more organic nitrogenous compounds in the samples after the extraction with water and ethanol than in the samples after the extraction with the neutral detergent solvent. This result was also observed for the pretreated samples. These results, therefore, show that the extraction step is very important because it can remove more organic nitrogenous compounds before the main compounds are characterized (lignin, carbohydrates).     

Kinetic determination of atrazine in foods based on stopped-flow fluorescence polarization immunoassay

A very simple and fast method for the direct determination of atrazine in food samples based on the use of stopped-flow fluorescence polarization immunoassay is described. Unlike other immunoassay methods where the analytical signal is obtained when the immunochemical reaction has reached or is close to the equilibrium, this method uses the initial rate of this reaction as the analytical parameter, which is measured in only 4-5 s. This approach minimizes the static signal from the sample matrix, allows the direct analysis of the samples and can be easily adapted to the routine automatic determination of atrazine. The dynamic range of the calibration graph was 0.7-100 ng ml(-1) and the detection limit was 0.2 ng ml(-1). The precision and selectivity of the method were also studied. The analytical recoveries obtained by applying the method to white and red wine, orange juice and tea samples ranged from 80 to 104%.     

顺序注射在线稀释微量进样技术及其在自动光度法测定水中亚硝酸盐的应用

以测定环境水样中的亚硝酸盐为例,采用顺序注射技术,提出了一种智能化在线微量进样稀释分析系统(SIA系统).将测定过程中分光光度计输出的模拟电压信号,反馈至顺序注射仪,判断是否需要稀释.当获得的电压信号值小于305 mV(约相当于吸光度值0.8)时,SIA系统进入稀释程序,否则,则进入直接测定程序,两种程序均自动完成.直接测定和稀释测定的线性范围分别为1～50μmol·L-1和50～500μmol·L-1NO2-.分别在NO2-浓度水平为10,200μmol·L-1时作精密度试验,测得相对标准偏差(n=11)依次为0.7%和1.0%.该分析系统特别适合于自动分析过程中被测物质浓度变化较大而需要在线稀释的情况.     

Application of flowing-stream techniques to water analysis Part II. General quality parameters and anionic compounds: halogenated, sulphur and metalloid species

In the first part of this review [Talanta 60 (2000) 867], flowing-stream methods (namely, segmented flow analysis (SFA), continuous-flow analysis (CFA), flow-injection analysis (FIA), sequential-injection analysis (SIA), multicommuted flow-injection analysis (MCFIA) and multisyringe flow-injection analysis (MSFIA)) were presented as powerful analytical tools for nutrient determination in water samples when coupled to photometric/fluorimetric detection, flow-through ion-selective electrodes or amperometric sensors.In the present paper, relevant flow methods applied to the monitoring of anionic species as well as to the determination of general parameters for water quality evaluation (such as pH, alkalinity, chemical and biochemical oxygen demand, conductivity and total ionic content) are reviewed, and their background, detection technique and noteworthy analytical features are detailed. Furthermore, other techniques, such as flow systems connected to hydride-generation atomic absorption spectrometry, should be highlighted as practical approaches for metalloid determination since a series of speciation schemes are demonstrated to be readily adaptable.     

Organic substances in potable water and in its precursor. III. The closed-loop stripping procedure compared with rapid liquid extraction.

An attempt is made to define the role of gas chromatography in the investigation of organic substances in water, which is important because the handling of water samples before gas chromatographic (GC) analysis depends entirely on the information expected from the subsequent separation, identification and quantification. Practical long-term experience with the previously published closed-loop stripping procedure (with intermediate adsorption on activated carbon) is described and further refinements are reported. A rapid and simple liquid extraction method is described, based on shaking 11 of water with a small volume (0.5-1 ml) of solvent and subsequent high-resolution GC analysis of the extract. Qualitative and semi-quantitative information at the parts per 10(12) level is easily obtained. Further studies of recovery rates under conditions where the volatility and polarity of extracted organic substances are varied are described for both methods. The suitability of both methods for the analysis of different types of water samples is discussed.     

A review on sequential injection methods for water analysis

The development of fast, automatic and less expensive methods of analysis has always been the main aim of flow methodologies. The search for new procedures that still maintain the reliability and accuracy of the reference procedures is an ever growing challenge. New requirements are continually added to analytical methodologies, such as lower consumption of samples and reagents, miniaturisation and portability of the equipment, computer interfaces for full decision systems and so on. Therefore, the development of flow methodologies meeting the extra requirements of water analysis is a challenging work.Sequential injection analysis (SIA) presents a set of characteristics that make it highly suitable for water analysis. With sequential injection analysis, most routine determinations in waters can be performed more quickly with much lower reagent consumption when compared to reference procedures. Additionally, SIA can be a valuable tool for analyte speciation and multiparametric analysis. This paper critically reviews the overall work in this area.     

Pesticides in water and the performance of the liquid-phase microextraction based techniques. A review

The control of pesticides in surface, drinking and groundwater is nowadays a real necessity. In the European Community, their concentration must comply with the established parametric and environmental quality standards (EQSs). Regarding the new legislation, this article updates the information concerning the monitoring of pesticides and the technical specifications for their measurement in water samples where ultra-sensitive analytical methods are required. For some compounds, like pesticides, there is still a need to improve the performance of the existing methods. High sensitive techniques like gas chromatography tandem mass spectrometry (GC–MS/MS) and liquid chromatography coupled with mass spectrometry (LC–MS) have been developed. However, for most of the substances present at trace and ultra-trace levels the extraction and preconcentration steps are so far essential for their detection. Advances at a micro scale have been made and different types of microextractions are being developed. Liquid-phase microextraction (LPME) is an example. The study of this technique has increased in the last years and some innovations have been recently reported for pesticides water analysis. This article reviews the new developed LPME-based techniques and compares its performance with the analytical specifications established for pesticides water monitoring. The results show that LPME-based techniques can be a promising tool to improve the nowadays performance of methods used in pesticides water control.     

Neutron activation analysis of trace elements in sea water samples (author's transl)

Analytical values of trace elements in sea water samples have been fluctuated according to the sampling locations, the analytical procedures and so on. It is very important in marine chemistry to elucidate the cause of such concentration variations. This report is the analytical results of the samples obtained in the Pacific Ocean, the Indian Ocean and the Sea of Japan, by means of neutron activation analysis. As the preconcentration, APDC-chelate extraction and freeze-drying were adopted. The specimens obtained by this extraction from 500 or 800 ml samples were irradiated by KUR reactor for 1 min, 1 hr to 10 hrs and the gamma-ray spectrometry with a Ge(Li) detector was used for the determination of V, Mn, Cu, Zn, U, Fe, Co, Ni, Ag, Sb and Au. By about 80 hrs irradiation of the specimens obtained by freeze-drying from 20 ml samples and their gamma-ray spectrometry, Sc, Cr, Fe, Co, Zn, Rb, Sr, Ag, Sb and Cs were determined. The former procedure gives concentrations of elements in species reactable with APDC, but the latter method shows entire concentrations of the elements in the sea water samples. Some considerations on the analytical values and the comparisons of the both methods are described.     

Comparison of a non-aqueous capillary electrophoresis method with high performance liquid chromatography for the determination of herbicides and metabolites in water samples

A method of capillary electrophoresis (CE) for the determination of triazine herbicides and some of their main metabolites in water samples has been developed. The proposed CE method includes an off-line solid-phase extraction (SPE) procedure with LiChrolut EN sorbent coupled to a non-aqueous capillary electrophoresis (NACE) separation with UV detection. The target compounds were the chloro-s-triazines simazine, atrazine, propazine; the methyltio-s-triazines ametryn and prometryn and three main derivatives from the atrazine degradation products; namely, deethylatrazine, deethylhydroxyatrazine and deisopropylhydroxyatrazine. The analytical characteristics of the CE method are reported. The repeatability of the method was studied considering the different steps of the method separately in order to determine the contributions of each step to the total variability of the method. The NACE-UV results are compared with those obtained with a high performance liquid chromatography with UV detection (HPLC-UV) method. The same off-line SPE procedure was applied to both techniques. The results obtained show that both methods afford the same results in the analysis of surface and drinking water samples, with a level of significance regarding the F- and t-tests greater than 0.05 in all the cases. The detection limits in surface water samples were in the 0.04-0.32 microg l(-1) and 0.11-1.2 microg l(-1) ranges for the NACE-UV and HPLC-UV methods, respectively. The recoveries (spiked/found) were significantly 100% in all cases.