High-resolution Continuum Source Absorption Spectrometry Research Articles

A new concept of efficient therapeutic drug monitoring using the high-resolution continuum source absorption spectrometry and the surface enhanced Raman spectroscopy

In this study, a new therapeutic drug monitoring approach has been tested based on the combination of CaF molecular absorption using high-resolution continuum source absorption spectrometry (HR-CSAS) and surface enhanced Raman spectroscopy (SERS). HR-CSAS with mini graphite tube was successfully tested for clinical therapeutic drug monitoring of the fluorine-containing drug capecitabine in sweat samples of cancer patients: It showed advantageous features of high selectivity (no interference from Cl), high sensitivity (characteristic mass of 0.1 ng at CaF 583.069 nm), low sample consumption (down to 30 nL) and fast measurement (no sample pretreatment and less than 1 min of responding time) in tracing the fluorine signal out of capecitabine. However, this technique has the disadvantage of the total loss of the drug's structure information after burning the sample at very high temperature. Therefore, a new concept of combining HR-CSAS with a non-destructive spectroscopic method (SERS) was proposed for the sensitive sensing and specific identification of capecitabine. We tested and succeed in obtaining the molecular characteristics of the metabolite of capecitabine (named 5-fluorouracil) by the non-destructive SERS technique. With the results shown in this work, it is demonstrated that the combined spectroscopic technique of HR-CSAS and SERS will be very useful in efficient therapeutic drug monitoring in the future.

Detection of capecitabine (Xeloda®) on the skin surface after oral administration.

Palmoplantar erythrodysesthesia (PPE), or hand-foot syndrome, is a cutaneous toxicity under various chemotherapeutics contributing to the most frequent side effects in patients treated with capecitabine (Xeloda®). The pathomechanism of PPE has been unclear. Here, the topical detection of capecitabine in the skin after oral application was shown in 10 patients receiving 2500 mg/m 2 /day 2500 mg/m2/day capecitabine. Sweat samples were taken prior to and one week after oral administration of capecitabine. Using high-resolution continuum source absorption spectrometry, the changes in concentrations of fluorine, which is an ingredient of capecitabine, were quantified and statistically analyzed. Here, we show an increase in fluorine concentrations from 40±10 ppb 40±10 ppb (2±0.5 pM 2±0.5 pM ) before capecitabine administration to 27.7±11.8 ppm 27.7±11.8 ppm (14.6±6.5 nM 14.6±6.5 nM ) after application, p<0.001 p<0.001 . The results show the secretion of capecitabine on the skin surface after oral administration, indicating a local toxic effect as a possible pathomechanism of PPE.

Spectrometric analysis of process etching solutions of the photovoltaic industry—Determination of HNO3, HF, and H2SiF6 using high-resolution continuum source absorption spectrometry of diatomic molecules and atoms

The surface of raw multicrystalline silicon wafers is treated with HF–HNO3 mixtures in order to remove the saw damage and to obtain a well-like structured surface of low reflectivity, the so-called texture. The industrial production of solar cells requires a consistent level of texturization for tens of thousands of wafers. Therefore, knowing the actual composition of the etch bath is a key element in process control in order to maintain a certain etch rate through replenishment of the consumed acids.The present paper describes a novel approach to quantify nitric acid (HNO3), hydrofluoric acid (HF), and hexafluosilicic acid (H2SiF6) using a high-resolution continuum source graphite furnace absorption spectrometer. The concentrations of Si (via Si atom absorption at the wavelength 251.611nm, m0,Si=130pg), of nitrate (via molecular absorption of NO at the wavelength 214.803nm, m0,NO3−=20 ng), and of total fluoride (via molecular absorption of AlF at the wavelength 227.46nm, m0,F=13 pg) were measured against aqueous standard solutions. The concentrations of H2SiF6 and HNO3 are directly obtained from the measurements. The HF concentration is calculated from the difference between the total fluoride content, and the amount of fluoride bound as H2SiF6. H2SiF6 and HNO3 can be determined with a relative uncertainty of less than 5% and recoveries of 97–103% and 96–105%, respectively. With regards to HF, acceptable results in terms of recovery and uncertainty are obtained for HF concentrations that are typical for the photovoltaic industry. The presented procedure has the unique advantage that the concentration of both, acids and metal impurities in etch solutions, can be routinely determined by a single analytical instrument.

Spectral interferences of oxygen and water molecules in hydride generation atomic absorption spectrometry with quartz atomizers: Comparison of preconcentration and on-line atomization modes for As and Se determination

Absorption by molecular oxygen and gaseous water in the vicinity of As 193.7 nm and Se 196.0 nm analytical lines in quartz atomizers was studied by both line source atomic absorption spectrometry and high-resolution continuum source absorption spectrometry. Oxygen absorption has a structured spectrum whereas water has a pseudo-continuum structure in the studied range. The influence of relevant experimental parameters such as atomizer temperature, carrier gas flow rate, and oxygen/water concentration on absorption by oxygen/water molecules was investigated. Effect of molecular oxygen and water absorption on background correction and thus their influence on determination of As and Se by hydride generation atomic absorption spectrometry is discussed comparing two modes of operation: (i) conventional mode of hydride generation in absence of preconcentration and (ii) preconcentration (trapping) mode.

Determination of sulfur forms in wine including free and total sulfur dioxide based on molecular absorption of carbon monosulfide in the air–acetylene flame

A new method for the determination of sulfur forms in wine, i.e., free SO(2), total SO(2), bound SO(2), total S, and sulfate, is presented. The method is based on the measurement of the carbon monosulfide (CS) molecular absorption produced in a conventional air-acetylene flame using high-resolution continuum source absorption spectrometry. Individual sulfur forms can be distinguished because of the different sensitivities of the corresponding CS molecular absorption. The sensitivity of free SO(2) is about three times higher than the value for bound SO(2) and sulfate. The method makes use of procedures similar to those used in classic reference methods. Its performance is verified by analyzing six wine samples. Relative standard deviations are between 5 and 13% for free SO(2) and between 1 and 3% for total SO(2). For the validation of the accuracy of the new method, the results are compared with those of reference methods. The agreement of the values for total SO(2) with values of the classic method is satisfactory: five out of six samples show deviations less than 16%. Due to the instability of free SO(2) in wine and the known problems of the used reference method, serious deviations of the free SO(2) results are found for three samples. The evaluation of the limits of detection focuses on the value for free SO(2), which is the sulfur form having by far the lowest concentration in wine. Here, the achievable limit of detection is 1.8 mg L(-1). [figure: see text] Detection of non-metal elements using continuum source flame absorption spectrometry.

Determination of halogens via molecules in the air–acetylene flame using high-resolution continuum source absorption spectrometry, Part II: Chlorine

As continuation of the work on fluorine, the second part of the studies of halogens in the air–acetylene flame attends to the determination of chlorine using high-resolution continuum source absorption spectrometry and molecular absorption. In case of chlorine, the diatomic InCl molecule proved to be a suitable species. For an excess of In in the flame, chlorine is converted to InCl which produces a distinctive band head at 267.24 nm that could be evaluated analytically. The influence of concentrated inorganic acids and metallic matrices on the absorption at this band head was tested. In all cases the signal proved to be unaffected, i.e., no spectral interferences were observed. However, serious chemical interferences were found in the presence of sulfuric and phosphoric acids, which could be partially eliminated by adding Ca in the form of nitrate. Moreover, nitric and hydrofluoric acids as well as Cu and Ga matrices also produced significant chemical interferences. Therefore, the method of standard additions should be used for calibration purposes. Concerning the limit of detection, a value of 3 mg L − 1 was achieved for a measurement time of 5 s in the presence of 10,000 mg L − 1 In. The calibration curve was linear up to a chlorine concentration of 1800 mg L − 1 . Three certified reference materials (BCR 151, HISS-1, and PACS-2) were analyzed to test the performance of the new method, yielding good precision and accuracy.

Determination of halogens via molecules in the air–acetylene flame using high-resolution continuum source absorption spectrometry: Part I. Fluorine

The particular capabilities of a high-resolution continuum source absorption spectrometer were exploited to the determination of halogens in an ordinary air–acetylene flame. In the first part of the studies, a simple method was developed, which allows the determination of fluorine by measuring GaF molecular absorption. The molecules are generated in the presence of an excess of Ga in the flame. Under such conditions, all fluorine is converted into GaF, yielding an evaluable signal for the fluorine determination. Molecular bands of GaF were found between 211 and 214 nm; the strongest absorption band head at 211.248 nm was examined in detail to prove its applicability to analytical measurements. To this end, potential chemical and spectral interferences were tested, using various highly concentrated acids and metallic salt solutions. Since no serious interferences were found, the new method proved to be very reliable. As limit of detection, 1 mg L − 1 fluorine in the presence of 10 g L − 1 Ga was achieved, using a measurement time of five seconds. The linear dynamic range covers more than three orders of magnitude. Accuracy and precision were verified by analysis of a standard reference material (BCR No. 33).

Determination of non-metals via molecular absorption using high-resolution continuum source absorption spectrometry and graphite furnace atomization

This work describes investigations on the determination of the non-metals fluorine, chlorine, sulfur and phosphorus in a graphite furnace atomizer using high-resolution continuum source absorption spectrometry. With this technique, the general problem of limited accessibility to the non-metal resonance lines, all located in the vacuum ultraviolet wavelength region, could be avoided by evaluation of narrow-band molecular absorption in the ultraviolet spectral region. The absorption originates from diatomic molecules produced under certain conditions in the graphite atomizer in the presence of the element in question. In detail, an excess of the metals gallium and aluminium was used to convert fluorine and chlorine to their molecular forms GaF and AlCl, respectively. In a similar manner, sulfur could be converted to CS and phosphorus to PO molecules. For all species, narrow spectral structures, belonging to specific band heads or individual rotational lines, could be found at well-accessible wavelengths between 211 and 261 nm. Using these absorption structures, analytical parameters were evaluated for the determination of the four non-metals. The obtained values for the characteristic masses and the limits of detection are as follows: 13 pg and 9 pg for fluorine; 300 pg and 70 pg for chlorine; 12 ng and 2.3 ng for sulfur; 4.4 ng and 0.9 ng for phosphorus. All methods developed were confirmed by measurements on certified reference materials. In comparison to previous investigations with an air–acetylene flame system, an improvement of up to three orders of magnitude in the limits of detection was achieved.