EXPRESS: Landmark Publications in Analytical Atomic Spectrometry: Fundamentals and Instrumentation Development.

The almost-two-centuries history of spectrochemical analysis has generated a body of literature so vast that it has become nearly intractable for experts, much less for those wishing to enter the field. Authoritative, focused reviews help to address this problem but become so granular that the overall directions of the field are lost. This broader perspective can be provided partially by general overviews but then the thinking, experimental details, theoretical underpinnings and instrumental innovations of the original work must be sacrificed. In the present compilation, this dilemma is overcome by assembling the most impactful publications in the area of analytical atomic spectrometry. Each entry was proposed by at least one current expert in the field and supported by a narrative that justifies its inclusion. The entries were then assembled into a coherent sequence and returned to contributors for a round-robin review.

A Novel Method for the Background Signal Correction in SP-ICP-MS Analysis of the Sizes of Titanium Dioxide Nanoparticles in Cosmetic Samples.

We discuss the features involved in determining the titanium dioxide nanoparticle (TiO2NP) sizes in cosmetic samples via single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) in the millisecond-time resolution mode, and methods for considering the background signal. In the SP-ICP-MS determination of TiO2NPs in cosmetics, the background signal was recorded in each dwell time interval due to the signal of the Ti dissolved form in deionized water, and the background signal of the cosmetic matrix was compensated by dilution. A correction procedure for the frequency and intensity of the background signal is proposed, which differs from the known procedures due to its correction by the standard deviation above the background signal. Background signals were removed from the sample signal distribution using the deionized water signal distribution. Data processing was carried out using Microsoft Office Excel and SPCal software. The distributions of NP signals in cosmetic product samples were studied in the dwell time range of 4-20 ms. The limit of detection of the NP size (LODsize) with the proposed background signal correction procedure was 71 nm. For the studied samples, the LODsize did not depend on the threshold of the background signal and was determined by the sensitivity of the mass spectrometer.

Reversible Sorptive Preconcentration of Noble Metals Followed by FI-ICP-MS Determination.

In this paper, we propose the combined procedure of noble metal (NM) determination, including fire assay, acid digestion, and reversible dynamic sorptive preconcentration, followed by flow-injection ICP-MS. Reversible preconcentration of all NMs was carried out using micro-column packed new PVBC-VP sorbent and elution with a mixture of thiourea, potassium thiocyanate, and HCl, which recovers Pd, Ir, Pt, and Au by 95% and Ru, and Rh by 90%. The proposed procedure was approved using certified reference materials.

A novel photochemical vapor generator for ICP-MS determination of As, Bi, Hg, Sb, Se and Te.

A scheme of determination of As, Bi, Hg, Sb, Se and Te with photochemical generation of their volatile derivatives and inductively coupled plasma mass spectrometry (ICP-MS) detection was developed. The volatile compounds were produced using a novel photochemical reactor with direct contact of a sample with an ultraviolet (UV) lamp. Essential experimental parameters such as the concentrations of the reagents and the flow rates of the carrier gas and the sample were optimized. For each element, individual optimum values of these parameters were obtained. The detection limits in the optimal single element modes for As, Bi, Hg, Sb, Se and Te were 0.5, 13, 0.6, 0.3, 0.4 and 0.7 ng L-1 respectively. Compromise conditions were determined for simultaneous multielement analysis. The increase of the detection limit for each element in the multielement mode was experimentally estimated. The applicability of the proposed scheme was demonstrated by analysis of certified reference samples of water and fish muscle. Acceptable accuracy of determination of As, Se, Sb, Te and Hg in samples of local lake water was proved by spike recovery test. Possible matrix effects were screened using Placket-Berman design and further examined in detail.

Determination of the Maximum Temperature in a Non-Uniform Hot Zone by Line-of-Site Absorption Spectroscopy with a Single Diode Laser.

A new algorithm for the estimation of the maximum temperature in a non-uniform hot zone by a sensor based on absorption spectrometry with a diode laser is developed. The algorithm is based on the fitting of the absorption spectrum with a test molecule in a non-uniform zone by linear combination of two single temperature spectra simulated using spectroscopic databases. The proposed algorithm allows one to better estimate the maximum temperature of a non-uniform zone and can be useful if only the maximum temperature rather than a precise temperature profile is of primary interest. The efficiency and specificity of the algorithm are demonstrated in numerical experiments and experimentally proven using an optical cell with two sections. Temperatures and water vapor concentrations could be independently regulated in both sections. The best fitting was found using a correlation technique. A distributed feedback (DFB) diode laser in the spectral range around 1.343 µm was used in the experiments. Because of the significant differences between the temperature dependences of the experimental and theoretical absorption spectra in the temperature range 300⁻1200 K, a database was constructed using experimentally detected single temperature spectra. Using the developed algorithm the maximum temperature in the two-section cell was estimated with accuracy better than 30 K.

Data Processing Algorithm for Diagnostics of Combustion Using Diode Laser Absorption Spectrometry.

A new algorithm for the evaluation of the integral line intensity for inferring the correct value for the temperature of a hot zone in the diagnostic of combustion by absorption spectroscopy with diode lasers is proposed. The algorithm is based not on the fitting of the baseline (BL) but on the expansion of the experimental and simulated spectra in a series of orthogonal polynomials, subtracting of the first three components of the expansion from both the experimental and simulated spectra, and fitting the spectra thus modified. The algorithm is tested in the numerical experiment by the simulation of the absorption spectra using a spectroscopic database, the addition of white noise, and the parabolic BL. Such constructed absorption spectra are treated as experimental in further calculations. The theoretical absorption spectra were simulated with the parameters (temperature, total pressure, concentration of water vapor) close to the parameters used for simulation of the experimental data. Then, spectra were expanded in the series of orthogonal polynomials and first components were subtracted from both spectra. The value of the correct integral line intensities and hence the correct temperature evaluation were obtained by fitting of the thus modified experimental and simulated spectra. The dependence of the mean and standard deviation of the evaluation of the integral line intensity on the linewidth and the number of subtracted components (first two or three) were examined. The proposed algorithm provides a correct estimation of temperature with standard deviation better than 60 K (for T = 1000 K) for the line half-width up to 0.6 cm-1. The proposed algorithm allows for obtaining the parameters of a hot zone without the fitting of usually unknown BL.

VEGF- and VEGFR2-Targeted Liposomes for Cisplatin Delivery to Glioma Cells.

Targeted delivery of anticancer drugs to brain tumors, especially glioblastoma multiforme, which is the most frequent and aggressive type, is one of the important objectives in nanomedicine. Vascular endothelial growth factor (VEGF) and its receptor type II (VEGFR2) are promising targets because they are overexpressed by not only core tumor cells but also by migrated glioma cells, which are responsible for resistance and rapid progression of brain tumors. The purpose of the present study was to develop the liposomal drug delivery system combining enhanced loading capacity of cisplatin and high binding affinity to glioma cells. This was achieved by using of highly soluble cisplatin analogue, cis-diamminedinitratoplatinum(II), and antibodies against the native form of VEGF or VEGFR2 conjugated to liposome surface. The developed drug delivery system revealed sustained drug release profile, high affinity to antigens, and increased uptake by glioma C6 and U-87 MG cells. Pharmacokinetic study on glioma C6-bearing rats revealed prolonged blood circulation time of the liposomal formulation. The above features enabled the present drug delivery system to overcome both poor pharmacokinetics typical for platinum formulations and low loading capacity typical for conventional liposomal cisplatin formulations.

Inductively coupled plasma mass spectrometry for metallodrug development: albumin binding and serum distribution of cytotoxic cis- and trans-isomeric platinum(II) complexes.

Binding to plasma proteins is one of the major metabolic pathways of metallodrugs. In the case of platinum-based anticancer drugs, it is the interaction with serum albumin that affects most strongly their in vivo behavior. Since both the configuration, i.e. cis-trans-isomerism, and the nature of leaving groups have an effect on the reactivity of Pt(II) coordination compounds toward biomolecules, a set of cis- and trans-configured complexes with halide leaving groups (Cl(-), Br(-), and I(-)) and 2-propanone oxime as carrier ligands was chosen for this study. Binding experiments were performed both with albumin and human serum and the Pt content in ultrafiltrates was quantified using inductively coupled plasma mass spectrometry. In order to shed light on the binding mechanism, the albumin binding constant (KHSA) and the octanol-water partition coefficient (P) were experimentally determined and relationships between log KHSA and log P were explored. The correlation was found significant only for cis-configured platinum complexes (R(2)=0.997 and standard deviation=0.02), indicating a certain contribution of the nonspecific binding which is largely dominated by the lipophilicity of compounds. In contrast, for trans-complexes a specific molecular recognition element plays a significant role. The participation of albumin in drug distribution in blood serum was assessed using an equilibrium distribution model and by comparing the percentage binding in the albumin and serum-protein fractions. Irrespective of the compound polarity, albumin contributes from 85 to 100% to the overall binding in serum.

Metallomics for drug development: serum protein binding and analysis of an anticancer tris(8-quinolinolato)gallium(III) drug using inductively coupled plasma mass spectrometry.

The application of an inductively coupled plasma mass spectrometry (ICP-MS) assay for quantifying in vitro binding of a gallium-based anticancer drug, tris(8-quinolinolato)gallium(III), to serum albumin and transferrin and in human serum is described. The distribution of the drug between the protein-rich and protein-free fractions was assessed via ICP-MS measurement of total gallium in ultrafiltrates. Comparative kinetic studies revealed that the drug exhibits a different reactivity toward individual proteins. While the maximum possible binding to albumin (~10%) occurs practically immediately, interaction with transferrin has a step-like character and the equilibrium state (with more than 50% binding) is reached for about 48 h. Drug transformation into the bound form in serum, also very fast, results in almost quantitative binding (~95%). The relative affinity of protein-drug binding was characterized in terms of the association constants ranging from 10(3) to 10(4)M(-1). In order to further promote clinical testing of the gallium drug, the ICP-MS method was applied for direct quantification of gallium in human serum spiked with the drug. The detection limit for gallium was found to be as low as 20 ng L(-1). The repeatability was better than 8% (as RSD) and the achieved recoveries were in the range 99-103%.

Determination of gallium originated from a gallium-based anticancer drug in human urine using ICP-MS.

Urine analysis gives an insight into the excretion of the administered drug which is related to its reactivity and toxicity. In this work, the capability of inductively coupled plasma mass spectrometry (ICP-MS) to measure ultratrace metal levels was utilized for rapid assaying of gallium originating from the novel gallium anticancer drug, tris(8-quinolinolato)gallium(III) (GaQ(3)), in human urine. Sample dilution with 1% (v/v) HNO(3) as the only required pre-treatment was shown to prevent contamination of the sample introduction system and to reduce polyatomic interferences from sample components. The origin of the blank signal at masses of gallium isotopes, 71 and 69, was investigated using high-resolution ICP-MS and attributed, respectively, to the formation of (36)Ar(35)Cl(+) and (40)Ar(31)P(+) ions and, tentatively, to a triplet of doubly charged ions of Ba, La, and Ce. The accuracy and precision performance was tested by evaluating a set of parameters for analytical method validation. The developed assay has been applied for the determination of gallium in urine samples spiked with GaQ(3). The achieved recoveries (95-102%) and quantification limit of 0.2 µg L(-1) emphasize the practical applicability of the presented analytical approach to monitor renal elimination of GaQ(3) at all dose levels in clinical trials that are currently in progress.