Marit Andersson

Determination of bromine, chlorine, sulphur and phosphorus in peat by X-ray fluorescence spectrometry combined with single-element and multi-element standard addition.

Bromine (20-40 ppm), chlorine (200-500 ppm), sulphur (0.2-3%) and phosphorus (300-1000 ppm) in peat have been determined by X-ray fluorescence spectrometry (XRFS) combined with the standard-addition method. Chlorine, sulphur and phosphorus have also been determined by other methods and agreement between the results is good. Theoretical calculations based on the Sherman equation were made to validate the linearity of the standard-addition curves. A multi-element standard-addition technique has been tested with addition of all elements at the same time. The results for chlorine were high but after correction for the difference in attenuation coefficient between the sample and added compound the results agreed with those from single-element standard addition.

Proteins in aqueous humor from cataract patients with and without pseudoexfoliation syndrome

The aim of this study was to investigate the protein content in aqueous humor in eyes with and without pseudoexfoliations (PEX) and to evaluate the quantitative proteomics method, isobaric tagging for relative and absolute protein quantification (iTRAQ), in combination with two separation methods followed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and tandem mass spectrometry (MS/MS). During cataract surgery, samples of aqueous humor were collected from 20 eyes with PEX and from 18 control eyes. The relative concentrations of proteins in the pooled samples of ten PEX eyes and eight controls were evaluated after trypsin digestion and labeling of the peptides with (iTRAQ) reagent. Two separation methods, liquid chromatography (LC) and capillary electrophoresis (CE) were used, followed by MALDI mass spectrometry and MS/MS. Furthermore, 1D gel electrophoresis was performed on the remaining ten pooled PEX samples and ten control samples. The gel material was separated by nano-liquid chromatography (nano-LC) followed by linear-ion-trap quadrupole Fourier transformation ion cyclotron resonance (FT-ICR). Fifty four proteins were identified in the LC runs and 24 with CE. The relative concentrations of β-crystallines B2 and S were raised and those of angiotensinogen and osteopontin lowered in the PEX sample compared to the control. The trends regarding β-crystallines B2, angiotensinogen and osteopontin were confirmed by the 1D gel electrophoresis.

Investigation of matrix effects in boron determination using organic solvents as modifiers for liquid chromatography coupled to ICP-MS

The extent and the causes of the reduction in boron signal by organic modifiers typically used in liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS) have been investigated. Three boron containing compounds in three organic solvents were analysed with both ICP-MS and ICP-AES to distinguish between ion effects in the interface to the mass spectrometer and other effects. A large decrease in the boron signal could be seen with all organic solvents used, but the responses of the different boron containing compounds were similar. When compared with elements that have similar mass and ionization energies to boron, the boron signal still decreased more than the signal for other elements. Studies of analyte fractionation in the sample introduction system showed no difference in analyte transport between different elements. A new technique, utilising the introduction of gaseous boron, was developed to distinguish between sample introduction phenomena and plasma or mass spectrometer related effects. The gas introduction experiments showed that the decrease of signal intensity is independent of the sample introduction system and must be caused by a plasma related effect. The decrease was greater in ICP-MS than in ICP-AES, probably because of mass discrimination in the ion optics or vacuum interface caused by polyatomic ions from the solvents.

Determination of lead in fly-ash from a garbage incinerator by atomic-absorption and x-ray fluorescence spectrometry

The lead content in fly-ash collected by an electrostatic precipitator has been determined by atomic-absorption spectrometry (AAS) after decomposition by four different leaching/dissolution techniques, and also determined by X-ray fluorescence spectrometry (XRFS) by the standard-addition method. The XRFS data were evaluated by non-linear regression since the standard additions affected the attenuation coefficient of the sample. Good agreement was obtained between the results obtained with AAS and XRFS. It is concluded that lead is quantitatively extracted by hot 1M nitric acid or treatment with hydrofluoric acid/nitric acid. Direct measurement of briquetted samples by XRFS is suggested for rapid monitoring of the lead content in fly-ash from garbage incineration.

Protein content in aqueous humor from patients with pseudoexfoliation (PEX) investigated by capillary LC MALDI-TOF/TOF MS

Analysis of proteins in human body fluids is challenging since the composition of the sample often is rather complex. Here we present a method for analysis of proteins in aqueous humor from two groups of cataract patients, with and without pseudoexfoliation (PEX). Aqueous humor is an extracellular fluid contained in the anterior chamber of the eye between the cornea and iris. The limited volume of sample requires sophisticated analysis techniques. Our method is based on a total tryptic digestion of the sample followed by capillary LC‐MALDI MS and MS/MS analysis of the peptides. The method is rapid, efficient and suitable as a complement or alternative to more commonly used methods based on gel electrophoretic experiments. With this method we found and unambiguously identified 30 nonredundant proteins. Proteins found include general transport proteins such as albumin and apolipoprotein A1 but also specific proteins involved in immune response, such as complement factors. Cystatin C, clusterin, and crystallins were also found. Although the number of proteins was roughly the same in both groups there was a significant difference in their identities. These findings may give some new insights into the pathophysiology of the PEX syndrome.

A miniature x-ray fluorescence setup

A miniature low-power x-ray fluorescence(XRF) setup has been designed, realized, and tested in vacuum. The experimental setup is centimeter sized and consists of an x-ray source and an electrically cooled silicon detector. The x-ray source has diamond membrane electrodes; the cathode is a field emitting microstructure and the anode is a metal film deposited on a diamond membrane. Anode radiation emergent through one of the diamond membrane electrodes induces characteristic x-ray radiation from a sample. By miniaturization of an XRF setup extremely low power consumption with acceptable yield and signal level is possible because of the small distances involved between source and sample and between sample and detector. The lightweighted XRF setup is intended for in situ materials analysis, e.g., for spacecraft applications, or probe mounted for portable mineralogy, archaeometry, or forensic equipment. In this article an initial test of the fluorescence setup is described and qualitative experimental results are presented and analyzed.

Quantification of 10 elements in human cerebrospinal fluid from chronic pain patients with and without spinal cord stimulation.

Neuropathic pain affects 1-10% of the general population and is caused by a lesion or disease of the somatosensory nervous system. Spinal cord stimulation (SCS), a method where implanted electrodes stimulate the spinal cord, has been successfully used to treat drug-resistant neuropathic pain, but the mechanism of action is largely unknown. Studies show that SCS changes the protein levels in CSF (cerebrospinal fluid) of pain patients. Several neurological conditions have been shown to alter the elemental composition of CSF. Therefore changes in the levels of ions and trace elements in the CSF may correspond to SCS use. This study used ICP-MS (Inductively coupled plasma mass spectrometry) and ICP-AES (Inductively coupled plasma atomic emission spectroscopy) to quantify 10 elements in CSF from chronic neuropathic pain patients using SCS. The element concentrations in CSF from patients with SCS treatment on/off, were measured. No effect on the element concentrations in CSF from treatment with SCS could be detected. Also, the elemental concentrations in pooled CSF from patients without chronic neuropathic pain was determined and compared to the patients using SCS. The concentration of the elements Ca, Sr, Na, K, P, Mg and Ti were, significantly higher in patients compared to the CSF-control.

Screening and identification of aluminium-containing biomolecules by column-switched LC-ICP-MS and LC-ESI-MS/MS

Column-switching liquid chromatography followed by low resolution ICP-MS was evaluated as a tool for speciation analysis of aluminium-containing biomolecules. The strategy was applied on siderophores, small organic molecules (Mr < 1500) which normally act as strong iron chelators. The drawbacks normally encounterd with aluminium detection using low resolution ICP-MS are the formation of polyatomic ions causing isobaric overlaps and space-charge effects. When adding a carbon rich solvent, such as methanol or acetonitrile, the 13C14N+, 12C15N+ and 12C14N1H+ with the same mass as 27Al+ will form in the plasma. The nitrogen is either entrained from the surrounding atmosphere or added with the constituents in the mobile phase. These disadvantages were successfully counteracted by the use of nitrogen free organic modifier in the mobile phase and the use of cool plasma conditions. Detection limits for standard solutions of aluminium-chelated ferrichrome in sub-nanomolar range were obtained by monitoring the aluminium-27 isotope. The combined use of LC-ICP-MS and LC-ESI-MS/MS was also evaluated as a tool to identify unknown metal complexes, here siderophores, in field soil solution samples. Two aluminium-chelated siderophores, Al-desferrichrom and Al-desferricrocin, were identified and quantified. Both aluminium-siderophore complexes were present in the low nanomolar range (1.1 and 0.7 nM, respectively).

A modified standard addition method in X-ray fluorescence spectrometry.

A modified standard addition method for single element determination by X-ray fluorescence spectrometry has been studied. The attenuation properties of the standard added samples are kept constant by adding decreasing amounts of an attenuation modifier along with increasing amounts of a standard. In this way the standard addition curve will be a straight line in cases where the ordinary standard addition curve is non-linear, and linear regression can be used to evaluate the concentration of the analyte. Standard additions of oxides of a number of elements, with and without modifier, have been made to cellulose powder or a mixture of aluminium oxide and polyethylene as matrices in order to test the method. The method has been applied to the determination of zinc in fly-ash from a steel work and of iron in cement. The fly-ash contained about 5% of zinc and the cement samples between 2 and 5% of Fe(2)O(3). The results were compared with those obtained by ICP-AES after decomposition of samples in lithium tetraborate or lithium metaborate and dissolution of the melt in 10%(v/v) nitric acid. The results agreed within 2%, relative, for fly-ash and within 3-6%, relative, for cement samples.

Determination of lead in household refuse fly-ash by X-ray fluorescence spectrometry and a modified standard-addition technique

Lead in fly-ash from a garbage incinerator has been determined by X-ray fluorescence spectrometry (XRFS) and a modified standard-addition method. To keep the attenuation properties of the spiked samples constant, decreasing amounts of an attenuation modifier [mercury (II) acetate] were added together with increasing amounts of the standard (lead nitrate). Linearity between fluorescence intensity and amount of lead was thus obtained, so the amount of lead in the sample could be evaluated by linear regression. The amount of modifier needed could be calculated from a simple expression. The method was validated by comparison with the results obtained by applying atomic-absorption spectrometry (AAS) to solutions made by leaching the fly-ash with strong acid. For 8 fly-ash samples, containing between 0.8 and 1.35% lead, the largest absolute difference between the two sets of results was 0.03%. Theoretical calculations based on a simplified version of the Sherman equation were performed to confirm the linearity of the modified standard-addition curves.