Microg Dm Research Articles

Development of a Compact System for the Determination of Lead Using a Liquid Core Waveguide and a Blue Diode as a Light Source

A simple and compact system was developed for the on-site analysis of lead in environmental water samples. The system consisted of a custom-made blue diode as a light source, a liquid core waveguide (LCW) as spectrophotometric cell and a compact UV-visible spectrometer. It weighed within 1.5 kg in total. Lead was detected using a spectrophotometric indicator reagent (TPPS: 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid, disulfuric acid, tetrahydrate) after masking interfering ions by coprecipitation with magnesium hydroxide. With an increase in the length of the LCW cell, the detection limit of lead was almost linearly enhanced, and the linear calibration range was shifted to a lower concentration range. The detection limit of lead by using 100 cm of a LCW cell was 2 nmol dm(-3). The observed value (9.6 +/- 0.4 microg dm(-3)) of lead in a river-water reference material (JSAC 0302-3) with this system was in good agreement with the certified value (9.9 +/- 0.2 microg dm(-3)).

Improved Solid-phase Spectrophotometry for the Microdetermination of Chromium(VI) in Natural Water

A simple and sensitive solid-phase spectrophotometry procedure was improved for the microdetermination of Cr(VI). A 0.06 cm3 portion of a cation exchanger, Muromac AG 50W-X2, was used to concentrate the target Cr(VI) in a 20 cm3 water sample, and resin beads were introduced in a flow cell of 1.5 mm diameter and having a 10 mm light path length for measurements using a UV-visible spectrophotometer. Three lenses were used for focusing the incident light beam and for recovering light scattered by the solid phase in the cell. The sensitivity achieved was higher by a factor of 277 compared with that of the solution method, and the detection limit was 0.014 microg dm(-3). The recovery on spiked real water samples by the standard addition method was 96-101%. Favorable working and performance characteristics made it possible to directly determine sub-microg dm(-3) amounts of Cr(VI) in natural water samples.

Arsenic exposure in Hungary, Romania and Slovakia

Inorganic arsenic is a potent human carcinogen and toxicant which people are exposed to mainly via drinking water and food. The objective of the present study was to assess current exposure to arsenic via drinking water in three European countries. For this purpose, 520 individuals from four Hungarian, two Slovakian and two Romanian countries were investigated by measuring inorganic arsenic and methylated arsenic metabolites in urine by high performance liquid chromatography with hydride generation and inductively coupled plasma mass spectrometry. Arsenic in drinking water was determined by atomic absorption spectrometry. Significantly higher concentrations of arsenic were found in both the water and the urine samples from the Hungarian counties (median: 11 and 15 microg dm(-3), respectively; p < 0.001) than from the Slovakian (median: 0.94 and 4.5 microg dm(-3), respectively) and Romanian (median: 0.70 and 2.1 microg dm(-3), respectively) counties. A significant correlation was seen between arsenic in water and arsenic in urine (R(2)= 0.46). At low water arsenic concentrations, the relative amount of dimethylarsinic acid (DMA) in urine was increased, indicating exposure via food. Also, high body mass index was associated with higher concentrations of arsenic in urine (p= 0.03), mostly in the form of DMA. Smokers had significantly higher urinary arsenic concentrations than non-smokers (p= 0.03). In conclusion, elevated arsenic exposure via drinking water was prevalent in some of the counties. Exposure to arsenic from food, mainly as DMA, and cigarette smoke, mainly as inorganic arsenic, are major determinants of arsenic exposure at very low concentrations of arsenic in drinking water.

A Kinetic Method for the Determination of Copper(II) by Its Catalytic Effect on the Oxidation of 3-Methyl-2-benzothiazolinone Hydrazone with Hydrogen Peroxide: A Mechanistic Study

A catalytic spectrophotometric method for the determination of traces of copper(II) is proposed. 3-Methyl-2-benzothiazolinone hydrazone (MBTH) is oxidized by hydrogen peroxide to form a yellowish-brown compound. The reaction is accelerated by trace amounts of copper(II), and can be followed by measuring the increase in the absorbance at 390 nm. Since the absorbance at 40 min from the reaction start increases with an increase in the copper(II) concentration, the absorbance value is used as a parameter for copper(II) determination. Under the optimum experimental conditions (8.4 x 10(-3) mol dm(-3) MBTH, 0.7 mol dm(-3) hydrogen peroxide, pH 5.2, 35 degrees C), copper(II) can be determined in the range 0-50 microg dm(-3). The relative standard deviations are 6.9, 3.5, 2.7% for 2, 20 and 40 microg dm(-3), respectively. The detection limit of this method (3sigma) is 0.27 microg dm(-3). It was successfully applied to a determination of copper(II) in river water, tap water and ground-water samples. According to the results of a kinetic study, a mechanism is proposed which leads to the following rate equation: R0(cat) = kK1K2[MBTH][H2O2][Cu(II)]0/{(1 + K2[H2O2])[H+]}.

A Case Study: Surface Contamination of Cyclophosphamide due to Working Practices and Cleaning Procedures in Two Italian Hospitals

The efficacy of preventive and organisational measures implemented in Italy to prevent the contamination of cytotoxic drug preparation rooms has been investigated, and oncologic wards of two Italian hospitals were examined. The sampling strategy was based not only on potential sources of contamination but also on responses to detailed questionnaires on workplace practices and work organisation. Wipe samples were taken from different surfaces of preparation rooms, before and after the work shift, over a span of a month. Cyclophosphamide was taken as the marker drug that reflects exposure to cytotoxic drugs, being measurable by GC/MS. In one of the two hospitals (Hospital A), a large amount of cyclophosphamide was found, both before and after shift, on the workbench (median value, 2.55 microg dm(-2), before shift), on the floor between the operator working position and the waste bin (>10 microg dm(-2), after shift), as also on door handles and storage shelves. No quantifiable levels of cytotoxic drug were detected in the second hospital investigated (Hospital B). These results could be attributed to the efficacy of cleaning procedures and working practices. In fact, both hospitals were provided with vertical-laminar airflow hoods and the (male) nurses had attended special training courses; but in Hospital A, cleaning procedures were carried out without substances used specifically for the cleaning of surfaces contaminated by cytotoxic drugs such as sodium hypochlorite. Working practices did not include Luer Lock devices. Cyclophosphamide concentrations found in both hospitals, compared with the quantities of drug handled, gave evidence of the importance of the correct handling of cytotoxic agents as a major tool in reducing contamination levels. The results reveal the insufficiency of the risk management measures which do not take into account working practices that are prevailing, and stress the necessity for periodic environmental monitoring, indispensable for evolving effective procedures to prevent antineoplastic drug exposure.

Determination of trace silica in highly purified water based on delayed quenching of Rhodamine B through nanoparticle formation with molybdosilicate

The development of a highly sensitive analytical method for trace silica is an urgent necessity for the real-time monitoring of highly purified water used in the semiconductor industry. However, there are no reports of a simple yet sensitive method for the determination of trace silica. Here we describe the delayed quenching phenomenon of Rhodamine B cation caused by nanoparticle formation with molybdosilicate ions in aqueous solution and its application to the one-step determination of trace silica at ppt to low ppb levels. We found that the quenching takes place over several minutes and the quenching time is dependent on the concentration of silica. The measurements made by a dynamic light scattering particle size analyzer indicated that the diameter of the particles were at nanometer levels. The detection limit was found to be 34 ng dm(-3) Si (1.2 x 10(-9) mol dm(-3)). The average quenching time for 1 microg dm(-3) was 239 s with an RSD of 2.2% (n= 7). The proposed method has been successfully applied to distilled and highly purified water samples. There was good agreement between the results obtained by the proposed method and those by ICP-three dimensions quadrupole MS/MS with 11-fold evaporation concentration. The main point of this method is that in the trace determination of silica, the signal is larger at lower concentrations. The advantages of the proposed method are that it can be used as real-time monitoring for trace silica in highly purified water, and will be a great aid to industries in which the quality control of water is crucial.

Determination of nitrite by flow injection spectrophotometry using a home-made flow cell detector.

A simple, rapid, low cost and accurate determination using flow injection spectrophotometry with a home made flow cell detector, in combination with green LED and photodiode, had been developed for nitrite based on the Griess-Saltzman reaction, measuring the absorbance at 525 nm. The proposed system is able to monitor nitrite in freshwater samples at a throughput of 60 samples per hour with a relative standard deviation (%RSD) of less than 2.4% and a detection limit of <7 microg dm(-3). The calibration graph was linear between 0.010 - 1.0 mg dm(-3).

Determination of indium by graphite furnace atomic absorption spectrometry after coprecipitation with chitosan.

A sensitive and simple method for the determination of trace amounts of indium in water samples by graphite furnace atomic absorption spectrometry (GFAAS) after coprecipitation with chitosan was investigated. Indium was quantitatively preconcentrated from water samples by coprecipitation with chitosan at pH 7.0-9.0. The coprecipitant was easily dissolved with acetic acid, and indium in the resulting solution was determined by GFAAS. The addition of lanthanum as a chemical modifier was more effective for the atomic absorbance of indium. The detection limit (S/N > or = 3) for indium was 0.04 microg dm(-3), and the relative standard deviations (n = 5) were 3.5-4.5% at 1.0 microg/100 cm3. The results obtained in this study indicate that the proposed method can be successfully applied to the determination of trace indium in water samples.

Simultaneous spectrophotometric determination of uranium and thorium by flow injection analysis using selective masking.

A flow injection system for the simultaneous determination of uranium and thorium has been developed by using selective masking and a spectrophotometric detector with two flow cells aligned with the same optical path. The injected sample solution was first mixed with a reagent solution containing Chromazurol S (CAS) and cetyltrimethylammonium chloride (CTMAC), and the total absorbance of uranium- and thorium-CAS complexes was measured in the first flow cell at 620 nm. The sample stream was then mixed with an EDTA solution in order to convert the thorium-CAS complex to a thorium-EDTA complex, and the absorbance of the uranium-CAS complex was measured in the second flow cell. The detection limits were 10 microg dm(-3) for uranium and 7 microg dm(-3) for thorium. The calibration graphs were linear (r < 0.9998) at least over the ranges of 0.1 to 10 mg dm(-3) for uranium and 0.08 to 8 mg dm(-3) for thorium. The RSDs were less than 1.5% (n = 3) in the calibration range. Uranium and thorium of up to the 6-fold concentration to each other could be determined in admixtures with relative errors of less than 3.3%. The sample throughput was 24 per hour. The proposed system was successfully applied to the analysis of a uranium-thorium ore mock solution by coupling with anion-exchange in a magnesium nitrate medium to eliminate interference from coexisting elements.

Levels of lead in atmospheric deposition in a large urban agglomeration in Poland.

Lead levels in wet and dry deposition were determined within this project. A network of 10 sampling stations was established. The stations were located in areas characterized by heavy traffic volumes, but away from industrial and/or municipal pollution sources. It was assumed, therefore, that lead in the samples collected was coming primarily from automobile emissions. Measurements were carried out over a period of one year. Both rain and snow samples were collected. Lead concentrations in the samples ranged from 0.6 to 141 microg dm(-3). They depended on street topography, traffic volume, average speed of the vehicles, frequency of traffic congestion and atmospheric conditions. The highest lead levels in deposition were observed during the cold season.