Determination of aminopolycarboxylic acids at ultra-trace levels by means of online coupling ion exchange chromatography and inductively coupled plasma-mass spectrometry with indirect detection via their Pd-complexes

A new indirect IC-ICP-MS method for the determination of aminopolycarboxylic acids in water samples is described. It is based on the addition of an excess of Pd(II) to water samples. The analytes are forced into very strong and negatively charged palladium complexes, separated by ion exchange chromatography and detected by their palladium content, utilizing an on-line coupled ICP-MS. This method is suitable to determine the concentration of 8 aminopolycarboxylic acids (nitrilotriacetic acid (NTA), (2-carboxyethyl) iminodiacetic acid (β-ADA), methylglycinediacetic acid (MGDA), 2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA), diethylene triamine pentaacetic acid (DTPA), ethylendiamine tetraacetic acid (EDTA), 1,3-diaminopropane tetraacetic acid (1,3-PDTA) and 1,2-diaminopropane tetraacetic acid (1,2-PDTA) at the ng kg⁻¹ level. The method is faster and easier than the established gas chromatography (GC)-method ISO 16588:2002 [1] and up to two orders of magnitude more sensitive than the ion pair chromatography based method of DIN 38413-8. Analytic performance is superior to ISO 16588:2002 and the comparability is good.     

Investigations of oxidative UV photolysis

Summary Oxidative UV photolysis according to DIN standard 38406 E 16 [1] has been investigated as a sample preparation method for voltammetry. UV photolysis has decisive advantages compared with mineral acid digestion owing to the simple procedure and the very low blank values, which in turn are due to the minimal reagent addition required. For UV photolysis with a high pressure mercury lamp, an apparatus has been used that employs a new type of sample cooling and that allows the simultaneous irradiation of 12 samples. The sample preparation for the voltammetric determination of zinc, cadmium, lead, copper, nickel and cobalt has been optimized using a model water solution and subsequently tested with real matrices. The type of organic matrix and the irradiation temperature determine the irradiation time required. To digest aromatic compounds, it is advantageous to work at reaction temperatures of ca. 90°C. The application of UV photolysis centers on water samples slightly polluted with organic compounds; however, it can also be used with more heavily polluted wastewaters. As the digestion times are at most 60 min, the method is of interest for routine analysis.     

On-line sample preparation and determination of phenols with a Flow-Analysis method

Summary A Flow-Analysis system has been developed to automate the phenol determination according to the German standard method DIN 38409-H16-2. The automation leads to a significant acceleration of the procedure. One analysis only lasts 3 min while the complete manual determination requires 3 h. Also the sample, solvent and reagent volumes are reduced to a tenth of the volumes demanded by the standard method. The described phenol determination is based on the integration of an airsegmented (Airsegmented-Flow-Analysis SFA) part in a Flow-Injection-Analysis (FIA) system. The main steps of the analytical procedure are: Reproducible inserting of the sample in a carrierstream, sample pretreatment and sample measuring. In the first step the sample is injected into the carrierstream. It transports the sample in the reactioncoil and than through the distillation unit. The steam distillation represents the sample preparation step; therefore an airsegmented stream is necessary. Afterwards the different phases (liquid and gas) were singled again and the distilled solution is fed into the FIA manifold. The determination itself takes place inside the FIA system. The limit of determination amounts to 0.01 mg l^–1 with a standard deviation of 1.5%. Different waste, surface and drinking water samples have been analyzed without any problems. The results correspond very well to those obtained by manual procedure.     

Harmful azo colorants in leather. Determination based on their cleavage and extraction of corresponding carcinogenic aromatic amines using modern extraction techniques

This study concerns the possibilities of using microwave-assisted extraction (MAE) or supercritical fluid extraction (SFE) for detection of harmful azo colorants in leather. After degreasing of the leather sample with SFE there follows a reductive cleavage of the azo colorants to their corresponding aromatic amines in the MAE or SFE equipment. The aromatic amines are subsequently extracted using either MAE or SFE and then finally determined by liquid chromatography with diode-array detection. The results have been compared with recoveries obtained using the German DIN method 53316. This standard method, based on conventional solvent extraction, is used in several European countries. Overall much better recoveries were obtained using MAE or SFE. With both MAE and SFE the amine recoveries of spiked leather samples were generally above 50%. The average recoveries were 62% for MAE and 60% for SFE (solvent collection) compared to 24% with the DIN method. For genuine leather samples the recoveries decreased, especially for benzidine. In this case the average values for MAE, SFE and DIN were 54, 38 and 19%, respectively. The quantification limits in leather samples using MAE or SFE were below 1 mg/kg for all amines investigated. The within-laboratory precision was generally better than 10%, varying somewhat with the analyte considered. With the proposed methodology, the amount of hazardous organic solvents used could be decreased and the sample throughput increased with at least a factor of two with less manual handling compared to the DIN method.     

Molar mass determination by end group analysis - amino group determination in aliphatic and partially aromatic polyamides with 1-fluoro-2,4-dinitrobenzene in benzyl alcohol

End group analysis is the most important absolute method of obtaining number-average molar mass values for polymers of the step-growth polymerization type. A great number of methods are available which primarily differ in the detection of the end group concerned. Special chemical methods based on the formation of covalent derivatives of the end groups (e.g. introduction of UV/VIS chromophores) are important if there is a need to demonstrate, with the aid of gel permeation chromatography, that damage to the polymer (e.g. onset of cross-linking) has occurred. In the case of fibre-forming polycondensation products, the applicability of end group analysis is often restricted by the lack of suitable reagents and solvents. This is also true of the determination of amino end groups in polyamides by means of 1-fluoro-2,4-dinitrobenzene, as is already contained in the German Standards specification (DIN 54 274) - albeit only for polyamide 6 and 6,6. This contribution describes a modified version of the 1-fluoro-2,4-dinitrobenzene method. The analytical principle and practical procedure correspond to those of DIN 54 274, but the solvent used for the reaction with the reagent is benzyl alcohol, and that for the photometric evaluation is 1,1,1,3,3,3-hexafluoro-2-propanol. The scope of the method is thus increased. Examples of applications for this method are commercial products based on aliphatic polyamides (6; 11; 12; 6,6; 6, 12), partially aromatic polyamides (2,4,4-trimethylhexamethylenediamine, terephthalic acid; copolyamides with bis-(4-aminocyclohexyl)propane(2), isophthalic acid, ω-aminododecanoic acid) and multicomponent systems with the abovementioned polyamides (bicomponent fibres, blends). It is shown that large differences may arise between the value determined by titration and the actual amino end group content. In addition, the presence of secondary amino groups can be demonstrated in polyamides of the Trogamid T type.     

The oxidative resistance of polymeric geosynthetic barriers (GBR-P) used for road and railway tunnels

The results of autoclave tests according to DIN EN ISO 13438 (method C) and conventional oven tests in line with DIN EN 14575 are presented for the evaluation of the resistance to oxidation of geosynthetic barriers GBR-P based on polyethylene. These GBR-P products are used as a barrier layer against water in road and railway tunnels. The residual mechanical stability of the exposed materials was determined by tensile testing. The remaining activity of the stabiliser was investigated using the OIT method. The results of both accelerating test methods are discussed and compared in detail. Based on autoclave tests at three temperatures (e.g. 60, 70 and 80 °C) and 50 bar oxygen pressure, and additionally two more measurements at 80 °C and 10 and 20 bar oxygen pressure, a modified Arrhenius extrapolation is used for an assessment of the expected service time of one of the GBR-P products.     

Mikrobestimmung von freiem Silicium in Siliciumcarbid

Zusammenfassung Der teilweise sehr niedrige Gehalt an freiem Silicium in den Siliciumcarbid-Hüllschichten beschichteter Kernbrennstoffteilchen für einen Hochtemperatur-Reaktor sowie die geringe Probenmenge machte eine Modifizierung des BestimmungsVerfahrens nach DIN 51075 erforderlich.Die Apparatur wurde stark verkleinert. Die Bestimmung des Wasserstoffs, der bei der Umsetzung des freien Siliciums mit Natronlauge entsteht, wurde von der volumetrischen Methode auf die sehr viel empfindlichere Messung mit der Wärmeleitfähigkeitszelle umgestellt. Aufgrund der Eichmessungen mit Eichhähnen sowie Blindwertmessungen wurde eine Nachweisgrenze von 100 ppm für die Probeneinwaage von 100 mg erreicht. Diese Bestimmungsmethode ist bei entsprechend niedrigen Probeneinwaagen auch für die Bestimmung sehr hoher Gehalte von freiem Silicium geeignet.

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Micro determination of free silicon in silicon carbide

Summary The in part very low content of free silicon in the silicon carbide claddings of nuclear fuel particles for a high-temperature reactor, as well as the small sample quantity, made it necessary to modify the method of determination according to DIN 51075.The apparatus has been considerably scaled down. The determination of hydrogen arising during the conversion of free silicon with caustic soda lye has been changed from the volumetric method to much more sensitive measurements with a thermal conductivity cell. By means of calibration measurements with calibration volumes, and also blank value measurements, a detection limit of 100 ppm was achieved for the weighed sample quantity of 100 mg. With correspondingly low weighed sample quantities, this determination method is also suitable for determining very high contents of free silicon.

     

A convenient and sensitive method for haloacetic acid analysis in tap water by on‐line field‐amplified sample‐stacking CE–ESI‐MS

In this study, we propose a simple strategy based on flow injection and field‐amplified sample‐stacking CE–ESI‐MS/MS to analyze haloacetic acids (HAAs) in tap water. Tap water was passed through a desalination cartridge before field‐amplified sample‐stacking CE–ESI‐MS/MS analysis to reduce sample salinity. With this treatment, the signals of the HAAs increased 300‐ to 1400‐fold. The LODs for tap water analysis were in the range of 10 to 100 ng/L, except for the LOD of monochloroacetic acid (1 μg/L in selected‐ion monitoring mode detection). The proposed method is fast, convenient, and sensitive enough to perform on‐line analysis of five HAAs in the tap water of Taipei City. Four HAAs, including trichloroacetic acid, dichloroacetic acid, dibromoacetic acid, and monobromoacetic acid, were detected at concentrations of approximately 1.74, 1.15, 0.16, and 0.15 ppb, respectively.     

Determination of hydroxyproline in meat products by flow injection analysis

Summary A modification of the German standard method for the determination of hydroxyproline (DIN 10144) is described. By applying a thermostatted reaction coil the relatively slow developing colour reaction between pyrrols and 4-dimethylaminobenzaldehyde could be adapted to FIA-conditions. The presented FIA-method allows for an injection frequency of 80/h and a sample throughput, on routine basis, of about 40/h. The reproducibility of multiple injections in the range 20–200 mg hydroxyproline/l hydrolysate is 1.5% r.s.d. Sulfuric and hydrochloric acid have been used for hydrolysis.

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Bestimmung des Hydroxyprolingehaltes von Fleischerzeugnissen mit Hilfe der Fließ-Injektionsanalyse