metrohm

Acrylic acid is a kind of important monomer and basic organic chemical raw material. In the process of catalytic preparation of acrylic acid from lactic acid, in order to monitor the catalytic process effectively and timely, an anion-exchange chromatographic (AEC) method has been established for the simultaneous determination of lactic acid and acrylic acid. The separation was carried out on a Metrohm A Supp 5 anion-exchange column (150 mm x 4.0 mm) with 2 mmol/L Na2CO3 +2 mmol/L NaHCO3 as the mobile phase...

A non-alcoholic coulometric reagent based on N-methylformamide (NMF) was shown to eliminate the severe interference effect caused by the alcohol component of the conventional Karl Fischer (KF) reagent on the battery electrolyte lithium bis(oxalato)borate (LiBOB). For sample amounts up to 240 microg of water, the stoichiometry of the KF reaction deviated only slightly from the ideal 1:1 ratio for the best reagent composition. Both solid and dissolved (in acetonitrile, tetrahydrofuran (THF), and ethylene carbonate/ethyl methyl carbonate) LiBOB were titrated successfully using a Metrohm 756 KF Coulometer with a diaphragm cell...

Factors influencing the accuracy and precision for diaphragm-free Karl Fischer coulometric determinations of low mug-amounts of water have been studied using the Metrohm 756 (pulsed current) coulometer and eight different types of commercial coulometric reagents and some modifications of these. As in the case of diaphragm-free coulometric titration of large amounts of water, the positive errors, due to the formation of oxidizable reduction products (of sulfur dioxide) in the cathode reaction (besides hydrogen), were found to be minimized by the use of highest possible pulse current (in the range 100-400mA) in combination with the fastest possible titration rate...

The majority of anions found in beer are a consequence of impurities derived from the water used during the brewing process. The process of beer manufacture consists of malting, brewing and fermentation followed by maturation before filtration and finally storage. Strict quality control is required because the presence of certain anions outside strictly defined tolerance limits can affect the flavour characteristics of the finished product. The anions present were quantified using the technique of ion chromatography with the Metrohm modular system following sample preparation...

BACKGROUND: Low sulphate levels in blood may contribute to osteoarthritis by decreasing cartilage chondroitin sulphation. OBJECTIVE: To measure serum levels of sulphate during 3 h of fasting or glucose ingestion after overnight fasts to determine how much sulphate lowering may occur during this period. METHODS: Sera from 14 patients with osteoarthritis who fasted overnight were obtained every 15-30 min during 3 h of continued fasting and during 3 h after ingestion of 75 g of glucose...

BACKGROUND: and objective: Glucosamine is suggested to affect glucose transport and insulin resistance. The effects of oral glucosamine on serum glucose and insulin levels at the initiation and throughout the duration of a 3-h oral glucose tolerance test were examined. METHODS: Sera from 16 patients with osteoarthritis, but with no other diagnosed medical condition who had fasted overnight, were obtained every 15-30 min during the 3 h of continued fasting and during the 3 h after ingestion of 75 g of glucose with or without ingestion of 1500 mg of glucosamine sulphate...

Square-wave voltammetry with the hanging drop mercury electrode as the working electrode was used for the determination of ultratraces of explosives in aqueous solution. It was shown that the strong pressure dependence of the pneumatically controlled multimode electrode system of a conventional Metrohm apparatus could be compensated by an additional pressure regulation, through which the pressure variations could be decreased when switching from deaeration to the static measurements. By using square-wave voltammetry with this electrode system after this modification the limits of detection for 2,4,6-trinitrotoluene (TNT) and other TNT-metabolites could be decreased down to 0...

BACKGROUND: Oral glucosamine preparations are widely used as a treatment for osteoarthritis, purportedly functioning by a variety of mechanisms suggested by results of in vitro experiments, and generally using glucosamine concentrations well in excess of 100 micromol/l. OBJECTIVE: To use high performance liquid chromatography with a high sensitivity Metrohm-Peak instrument for pulsed amperometric measurement of human serum glucosamine; a detection limit of 0.5 micromol/l at 1:10 serum dilution allowed measurement of low levels of glucosamine in human serum, which previously has not been possible...

A new carbon paste electrode (CPE) for the determination of iodide ion based on a cetyltrimethylammonium iodide (CTMAI) ion pair as an electroactive material is described. The electrode shows a linear response for iodide ion over the concentration range of 4 x 10(-5) M to 1 x 10(-1) M with a lower detection limit of 4 x 10(-5) M at 25 degrees C. The electrode has a Nemstian slope of -55.0 +/- 0.4 mV/decade and a fast potential response of 45 s, which is almost constant over a pH range of 5.0 - 9.0. Selectivity coefficient data of the CTMAI-CPE for some common ions show negligible interference, and the electrode has high selectivity towards the iodide ion...

Textile finishing industry wastewater often contains high concentrations of surfactants. Non-ionic surfactants like alcohol ethoxylates are among the most used surfactants and are discharged from batch-processes in widely varying concentrations. The anaerobic biomass and especially methanogenic microorganisms have been shown to be inhibited by surfactants. To protect these microorganisms from irreversible inhibition a measurement of the surfactant concentration is useful for the process control, but most analytical methods are too complicated and expensive for an on-line process control...

Different designs of a semiopen, drainable cathode compartment of a medium-sized coulometric Karl Fischer (KF) cell for the determination of water in the range 0.1-500 microg were evaluated. The main criterion for the design was to keep the resistance between the anolyte and catholyte low enough to permit the generation of currents larger than 20 mA (for an output voltage of 28 V). It was found that a good compromise between the size of this current and a minimal influence from diffusing/migrating oxidizable reduction products from the catholyte was achieved by means of an interface having a channel length and diameter of 8 and 2...

A non-suppressed ion chromatographic method with conductometric detection is described for the simultaneous determination of six inorganic anions: fluoride, chloride, nitrite, bromide, nitrate and sulphate. The separation was achieved on a low-capacity anion-exchange column Metrohm IC Anion Column Super Sep, with a mobile phase consisting of phtalic acid dissolved in high-purity water, 2-amino-2-hydroxymethyl-1,3-propendiol and acetonitrile. In this work computer optimization procedures, using computer programs to select chromatographic conditions have been used, leading to the achievement of a desired separation...

Factors influencing the accuracy of water determinations using diaphragm-free, pulsed current Karl Fischer (KF) coulometry were investigated with the new Metrohm 756 instrument. Results obtained with commercially available reagents from Riedel-deHaen and Merck were compared with home-made ones that were especially designed to minimize the formation of iodine-consuming reduction products generated in the cathode reaction. Positive errors in the range 2-5% were found for the commercial reagents as compared to 0...

We have investigated the effect on the pH of the gastric fluid of a single dose of sodium citrate 0.3 mol litre-1 (antacid) and a solution containing sodium citrate dehydrate (100 mg ml-1) with citric acid monohydrate (66 mg ml-1) (buffer). The dose for both solutions was 0.4 ml kg-1 via a nasogastric tube. Each group comprised 10 patients undergoing neurosurgical operations of 5-7 h duration. A control group of 10 patients received no gastric solution. The pH of the gastric aspirate was measured hourly using a Metrohm 632 digital pH meter (Synectics Medical, Sweden)...

This double-blind randomized study compared the effects of an epidural injection of lidocaine hydrochloride 2% (HCl) (Group 1), alkalinized lidocaine 2% (1 ml NaHCO3 per 10 ml of solution) injected either immediately (Group 2) or one hour after preparation (Group 3) in 45 parturients (n = 15 per group) scheduled for elective Caesarean section. Each patient received 16 ml of one of the three solutions. The mean pH values measured just before administration with a pH-meter PHM 64 Metrohm AG were 6.77 for the HCl lidocaine 2% solution, 7...

A method for simultaneous determinations of noradrenaline (NA), adrenaline (A) and dopamine (DA) in tissue is described. After extraction from crude deproteinized homogenates by the batch mode aluminium oxide method individual catecholamines (CA) were separated in a high-performance liquid chromatography (HPLC) system by isocratic elution with pure aqueous buffers from an octadecyl column. These eluates were directly monitored with a new amperometric detector device (Metrohm VA E 641) in a wall-jet flow cell...

The urease method developed by Noone et al. for rapid bioassay of aminoglycoside antibiotics in serum is described in detail. The accuracy of the method was improved by using a BM 1-09 electrode assembly (Metrohm, CH-9100 Herisau, Switzerland) in conjunction with a digital pH-Meter (Metrohm E 500). The mean difference between spiked serum samples and measured concentrations was +0.37 +/-0.78 microgram/ml. The coefficient of determination between the urease and agar diffusion method was 0.94. Disadvantages of the method are a low sensitivity at concentrations below 1...