Laser-induced acoustic desorption coupled with electrospray ionization mass spectrometry for rapid qualitative and quantitative analysis of glucocorticoids illegally added in creams.

We present a strategy for the coupling of laser-induced acoustic desorption (LIAD) with electrospray ionization (ESI) mass spectrometry. Different from desorption electrospray ionization (DESI) or paper spray ionization (PSI), the technique decouples the desorption of analytes from the subsequent ionization. The desorption is initiated by a shock wave induced in 10 µm titanium (Ti) foil coated with the sample, irradiated from the rear side by a laser beam, and then the desorbed neutral analytes are post-ionized by ESI and finally characterized by quadrupole/time-of-flight (Q-TOF) mass spectrometry (MS). Separating desorption from the ionization event makes this technique flexible and decreases the matrix effect and salt effect. Various kinds of common creams containing glucocorticoids are investigated using LIAD/ESI/MS without sample pretreatment. The results show that volatile and nonvolatile analytes in creams are sampled simultaneously by LIAD, providing a convenient way for high-throughput screening of the target compounds. In addition, quantitation of glucocorticoids in creams was performed by analyzing samples with decreasing concentrations of analytes (dexamethasone (20 µg g-1) used as an internal standard (IS)), until no more signal was observed. The limits of detection (LODs) of glucocorticoids were determined experimentally to be ranging from 0.7 µg g-1 for triamcinolone acetonide to 10 µg g-1 for beclomethasone dipropionate, which are two orders of magnitude lower than the regular usage of glucocorticoids (beclomethasone dipropionate 0.25 mg g-1, triamcinolone acetonide 0.25 mg g-1). Overall, LIAD/ESI/MS is demonstrated to be of great practical importance for rapid qualitative and quantitative analysis of glucocorticoids in creams, and good sensitivity can be achieved without tedious sample pretreatment and time-consuming chromatographic separation, irrespective of the presence of complex matrices.

Confirmatory surface analysis of equivocal documents with pigment-based gel inks via laser desorption laser postionization mass spectrometry imaging.

Laser desorption laser postionization time-of-flight mass spectrometry (L2MS) was applied for unambiguous discrimination of pigment-based inks in blue, black, and red gel pens and molecular imaging of equivocal documents in a quasi-non-destructive way. In comparison to laser desorption mass spectrometry (LD-MS), additional discriminatory information on ink components is acquired uniquely, facilitating the distinct differentiation of various pigmented gel inks. More importantly, diversified images of additional characteristic ions achieved using L2MS offer reliable support to discriminate forged documents and decipher important hidden contents. Apart from minimized matrix effect and maximized ionization yield, direct and confirmatory identification of forged documents is achieved successfully without solvent or matrix involved, not only eliminating unwanted damage and contamination to the samples but significantly shortening the overall analysis time. In addition, L2MS is a minimally destructive approach with tiny analyte consumption. With these appealing qualities, L2MS imaging is poised to be a powerful tool for confirmatory surface analysis of complex pigment-based samples. Graphical Abstract Weight and see: Highly distinct and comprehensive images of counterfeit documents with blue-pigmented gel inks are achieved successfully, due to the high sensitivity and increased ion yield of laser desorption laser postionization time-of-flight mass spectrometry. The hidden important contents of the obliterated documents are visually deciphered with the help of the additional chemical information.

Microtrace Analysis of Rare Earth Element Residues in Femtogram Quantities by Laser Desorption and Laser Postionization Mass Spectrometry.

A newly developed laser desorption and laser postionization time-of-flight mass spectrometer (LD-LPI-TOFMS) for the direct microtrace determination of rare earth elements (REEs) in residues has been presented. Benefiting from spatially and temporally separated processes between desorption and ionization, LD-LPI-TOFMS plays a dual role in alleviating the barriers of deteriorating spectral resolution at high irradiance, serious matrix effects and elemental fractionation effects at low irradiance. Compared with the conventional laser desorption/ionization (LDI) method, this technique offers unambiguous full-elemental determination of 15 REEs with more uniform relative sensitivity coefficients (RSCs) ranging from 0.5 to 2.5 for all REEs investigated, satisfying the semiquantitative analysis criteria. More importantly, a highly sensitive analysis of REEs with very little consumption was achieved by getting the utmost out of desorbed neutral atoms instead of increasing the amount of the sample, resulting in outstanding relative and absolute limits of detection (LODs and ALODs) of ∼ng/mL and ∼femtogram. The results presented here indicate that LD-LPI-TOFMS offers great potential in microtrace determination for elements in solution samples with minor sample preparation.

Three-Dimensional Elemental Imaging of Nantan Meteorite via Femtosecond Laser Ionization Time-of-Flight Mass Spectrometry.

Femtosecond laser ionization time-of-flight mass spectrometry (fs-LI-TOFMS) is introduced for the three-dimensional elemental analysis of a Nantan meteorite. Spatially resolved multielemental imaging of major and minor compositions in a meteorite are presented with a lateral resolution of 50 µm and a depth resolution of 7 µm. Distinct 3D distributions of siderophile, lithophile, and chalcophile elements are revealed. Co and Ni are highly siderophile (Iron-loving), mainly enriched in the metal phase. Cr, Cu, V, and Mn are enriched in the sulfide for their chalcophile (S-loving) tendency. S, P, and C aggregate together in the analytical volume. Silicate inclusion, containing lithophile elements of Al, Ca, Mg, K, and so on, is embedded within the metal phase for the immiscibility between silicate inclusion and the melted metal phase. These 3D distributions of elements aid the exploration of the formation and evolution of the meteorite. They also reveal the feasibility of fs-LI-TOFMS as a versatile tool for 3D imaging.

Pulsed microdischarge with inductively coupled plasma mass spectrometry for elemental analysis on solid metal samples.

Pulsed microdischarge employed as source for direct solid analysis was investigated in N2 environment at atmospheric pressure. Compared with direct current (DC) microdischarge, it exhibits advantages with respect to the ablation and emission of the sample. Comprehensive evidence, including voltage-current relationship, current density (j), and electron density (ne), suggests that pulsed microdischarge is in the arc regime while DC microdischarge belongs to glow. Capability in ablating metal samples demonstrates that pulsed microdischarge is a viable option for direct solid sampling because of the enhanced instantaneous energy. Using optical spectrometer, only common emission lines of N2 can be acquired in DC mode, whereas primary atomic and ionic lines of the sample are obtained in the case of pulsed mode. Calculations show a significant difference in N2 vibrational temperatures between DC and pulsed microdischarge. Combined with inductively coupled plasma mass spectrometry (ICPMS), pulsed microdischarge exhibits much better performances in calibration linearity and limits of detection (LOD) than those of DC discharge in direct analysis of samples of different matrices. To improve transmission efficiency, a mixture of Ar and N2 was employed as discharge gas as well as carrier gas in follow-up experiments, facilitating that LODs of most elements reached ng/g.

Thermal diffusion desorption for the comprehensive analysis of organic compounds.

Comprehensive analysis of organic compounds is crucial yet challenging considering that information on elements, fragments, and molecules is unavailable simultaneously by current analytical techniques. Additionally, many compounds are insoluble or only dissolve in toxic solvents. A solvent- and matrix-free strategy has been developed which allows the organic compound analyzed in its original form. It utilizes thermal diffusion desorption with the solid analyte irradiated with high energy laser. It is capable of providing explicit elemental, fragmental, and molecular information simultaneously for a variety of organic compounds. Thermal diffusion desorption has many advantages compared to the electrospray and MALDI techniques. The protons that form the protonated molecular ions originate from the analyte itself. All the elements and fragments are also derived from the analyte itself, which provides abundant information and expedites the identification of organic compounds.

Minimizing matrix effect by femtosecond laser ablation and ionization in elemental determination.

Matrix effect is unavoidable in direct solid analysis, which usually is a leading cause of the nonstoichiometric effect in quantitative analysis. In this research, experiments were carried out to study the overall characteristics of atomization and ionization in laser-solid interaction. Both nanosecond (ns) and femtosecond (fs) lasers were applied in a buffer-gas-assisted ionization source coupled with an orthogonal time-of-flight mass spectrometer. Twenty-nine solid standards of ten different matrices, including six metals and four dielectrics, were analyzed. The results indicate that the fs-laser mode offers more stable relative sensitivity coefficients (RSCs) with irradiance higher than 7 × 10(13) W·cm(-2), which could be more reliable in the determination of element composition of solids. The matrix effect is reduced by half when the fs-laser is employed, owing to the fact that the fs-laser ablation and ionization (fs-LAI) incurs an almost heat-free ablation process and creates a dense plasma for the stable ionization.

Single-cell elemental analysis via high irradiance femtosecond laser ionization time-of-flight mass spectrometry.

In modern bioanalytics, elemental analysis of single cells is important yet challenging due to the complicated biological matrices and elemental contents. We have developed the high irradiance femtosecond laser ionization orthogonal time-of-flight mass spectrometry (fs-LI-O-TOFMS) to determine the elemental composition of individual cells. The sample preparation procedure is simple and fast through heating and drying the cells. Under typical operating conditions, elements above femtogram levels in a single cell can be clearly observed in the spectrum with reasonable isotope ratios. Some of the nonmetallic elements that are difficult to measure by ICPMS, such as P, S, and Cl, can be easily determined by fs-LI-O-TOFMS. Replicate analyses show that signal variations are 15-35% for metallic elements and 25-50% for nonmetallic elements. The results demonstrate that fs-LI-O-TOFMS is a simple, rapid, and practical tool for the elemental determination of single cells.

High irradiance laser ionization orthogonal time-of-flight mass spectrometry: a versatile tool for solid analysis.

This article reviews the development of and applications for high irradiance laser ionization orthogonal time-of-flight mass spectrometry (LI-O-TOFMS). LI-O-TOFMS has solved the bottleneck problems in traditional high irradiance laser ionization mass spectrometry, which allows the instrument to acquire explicit spectra with high resolution. A buffer-gas-assisted ion source effectively reduces the kinetic energy of the ions and suppresses the multiply charged ion interference. The pulse train data acquisition technique was applied to reduce the spectrum interference from multiply charged ions and polyatomic ions according to the temporal profiles of different ion packets in the repelling region. Relatively high laser irradiance (≥10(10) W/cm(2)) is preferable for achieving uniform relative sensitivities for different elements in the samples of different matrices. LI-O-TOFMS has been used in the standardless, semiquantitative analysis of solids, which is proved to be a fast and convenient technique for solid sample analysis. By increasing the laser irradiance and reducing the buffer gas pressure, the determination of nonmetallic elements in solids can also be achieved without losing spectral explicity. Recent applications, such as elemental analysis of a single egg cell and acquiring elemental, fragmental, and molecular information of chemicals, were given to demonstrate the potential of the new technique. All of these results reveal that LI-O-TOFMS is an advanced tool in the elemental analysis of solids in terms of modern mass spectrometry.

Molecular Characterization Analysis of Prevalent Infectious Bronchitis Virus and Pathogenicity Assessment of Recombination Strain in China.

Avian coronavirus infectious bronchitis virus (IBV) is a respiratory pathogen of chickens, resulting in severe economic losses in the poultry industry. This study aimed to monitor and isolate the molecular identity of IBV in broiler flocks with respiratory symptoms in eight provinces of China. In total, 910 samples (oropharyngeal and cloacal mixed swabs) from broiler flocks showed IBV positive rates of 17.6% (160/910) using PCR assay. Phylogenetic analysis of the complete S1 genes of 160 IBV isolates was performed and revealed that QX-type (GI-19), TW-type (GI-7), 4/91-type (GI-13), HN08-type (GI-22),TC07-2-type (GVI-1), and LDT3-type (GI-28) exhibited IBV positive rates of 58.15, 25, 8.12, 1.86, 5.62, and 1.25%. In addition, recombination analyses revealed that the four newly IBV isolates presented different recombination patterns. The CK/CH/JS/YC10-3 isolate likely originated from recombination events between strain YX10 (QX-type) and strain TW2575-98 (TW-type), the pathogenicity of which was assessed, comparing it with strain GZ14 (TW-type) and strain CK/CH/GD/JR07-7 (QX-type). The complete S1 gene data from these isolates indicate that IBV has consistently evolved through genetic recombination or mutation, more likely changing the viral pathogenicity and leading to larger outbreaks in chick populations, in China.

Recombinant Muscovy Duck Parvovirus Led to Ileac Damage in Muscovy Ducklings.

Waterfowl parvovirus (WPFs) has multiple effects on the intestinal tract, but the effects of recombinant Muscovy duck parvovirus (rMDPV) have not been elucidated. In this study, 48 one-day-old Muscovy ducklings were divided into an infected group and a control group. Plasma and ileal samples were collected from both groups at 2, 4, 6, and 8 days post-infection (dpi), both six ducklings at a time. Next, we analyzed the genomic sequence of the rMDPV strain. Results showed that the ileal villus structure was destroyed seriously at 4, 6, 8 dpi, and the expression of ZO-1, Occludin, and Claudin-1 decreased at 4, 6 dpi; 4, 6, 8 dpi; and 2, 6 dpi, respectively. Intestinal cytokines IFN-α, IL-1ß and IL-6 increased at 6 dpi; 8 dpi; and 6, 8 dpi, respectively, whereas IL-2 decreased at 6, 8 dpi. The diversity of ileal flora increased significantly at 4 dpi and decreased at 8 dpi. The bacteria Ochrobactrum and Enterococcus increased and decreased at 4, 8 dpi; 2, 4 dpi, respectively. Plasma MDA increased at 2 dpi, SOD, CAT, and T-AOC decreased at 2, 4, 8 dpi; 4, 8 dpi; and 4, 6, 8 dpi, respectively. These results suggest that rMDPV infection led to early intestinal barrier dysfunction, inflammation, ileac microbiota disruption, and oxidative stress.

Simultaneous acquisition of elemental, fragmental, and molecular information on organometallic compounds.

A novel method for obtaining elemental, fragmental, and molecular information of organometallic compounds has been developed using high irradiance laser induced time-of-flight mass spectrometry (LI-TOFMS) with a buffer-gas-assisted ion source. This technique permits direct and matrix-free analysis of solid analyte with minimal sample preparation. In addition, it shows special advantages in integrated acquisition of elemental, fragmental, and molecular information from a single target, on the basis of which identification of organometallic complexes is simplified and expedited.

Elemental imaging via laser ionization orthogonal time-of-flight mass spectrometry.

An elemental imaging method using a laser ionization orthogonal time-of-flight mass spectrometer system was developed for the simultaneous detection of all metal and nonmetal elements. The instrument control and data processing were realized by self-developed programs. This system is capable of simultaneous detection of metal and nonmetal elements, with a spatial resolution of 50 µm, the lowest detection limits of 3 × 10(-7) g/g (Li), and a dynamic range of 7 orders of magnitude. Moreover, this technique does not require standards for quantitative analysis and can be a powerful and versatile tool for elemental imaging.

Two-dimensional separation in laser ionization orthogonal time-of-flight mass spectrometry.

The capabilities of two-dimensional separation using a high irradiance laser ionization orthogonal time-of-flight mass spectrometer (LI-O-TOFMS) were demonstrated in this paper. Ions were separated via their initial kinetic energy in one dimension and their mass-to-charge ratios in the other dimension. Investigation of the transient ion profiles after laser pulses revealed that the separation of analyte ions from multiply charged ions and gas species ions was achieved. Comparison of mass spectra in the normal accumulation mode and in the two-dimensional separation mode indicated that the relative sensitivity coefficients are stable and close to their true values in the two-dimensional separation mode, especially for trace elements that are prone to interference.

Laser ionization orthogonal time-of-flight mass spectrometry for simultaneous determination of nonmetallic elements in solids.

The simultaneous determination of nonmetallic elements in solid samples is difficult owing to their discrepant physical and chemical properties. We developed a high-irradiance laser ionization orthogonal time-of-flight mass spectrometry (LI-O-TOFMS) system and applied it for the determination of nonmetallic elements in solids. Helium was used as the buffer gas at 250 Pa in the source chamber; the laser irradiance was about 7 x 10(10) W/cm(2). A series of artificial standards containing B, C, N, O, F, Si, P, S, Cl, As, Br, Se, I, and Te were used. Explicit spectra were obtained with only a little interference from gas species and doubly charged matrix ions. Standardless semiquantitative analysis could be accomplished with a novel sampling methodology to obtain near-uniform sensitivity coefficients for different elements. Limits of detection (LOD) at microgram per gram level and a dynamic range of 6 orders of magnitude were achieved for most nonmetallic elements.

Direct infusion mass spectrometry or liquid chromatography mass spectrometry for human metabonomics? A serum metabonomic study of kidney cancer.

Serum samples from kidney cancer patients and healthy controls were analyzed by both direct infusion mass spectrometry (DIMS) and liquid chromatography-mass spectrometry (LC-MS) with a high resolution ESI-Q-TOFMS. The classification and biomarker discovery capacities of the two methods were compared, and MS/MS experiments were carried out to identify potential biomarkers. DIMS had comparable classification and prediction capabilities to LC-MS but consumed only ~5% of the analysis time. With regard to biomarker discovery, twenty-three variables were found as potential biomarkers by DIMS, and 48 variables were obtained by LC-MS. DIMS is recommended to be a fast diagnostic method for kidney cancer, while LC-MS is necessary when comprehensive screening of biomarkers is required.

[Speciation analysis of cadmium in cadmium-enriched plants with SE-HPLC combined with ICP-MS and ESI-MS].

Different species of ferns (pyrrosia lingua, Lepisorus thunbergianus, Lycopodium japonicum, Elaphoglossum yoshinagae and Woodwardia japonica) were cultivated using different species of cadmium as cultivation solution. The results showed that there were differences in enrichment amounts of cadmium in different parts of plants (amounts in root > in stem > in leaves). And it was found that different species of cadmium could induce synthesization of plant--chelated peptides (PCs) with different extents. And then PCs was coordinated with cadmium to decrease the toxicity from cadmium. There are some kinds of peptides ligands found in plants, which are mainly PC3, iso-PC3(betaAla) and iso-PC2(betaAla). In the present paper, the distribution of cadmium in different parts of ferns was studied after the ferns were intimidated with different species of cadmium. And the species of PCs-Cd coordination compounds were also investigated to explain the detoxification mechanism aroused by it.

Nanoscale laser-induced breakdown spectroscopy imaging reveals chemical distribution with subcellular resolution.

Understanding chemical compositions is one of the most important parts in exploring the microscopic world. As a simple method for elemental detection, laser-induced breakdown spectroscopy (LIBS) is widely used in materials, geological and life science fields. However, due to the long-existing limitation in spatial resolution, it is difficult for LIBS to play an analytical role in the field of micro-world. Herein, we first report a reliable nanoscale resolution LIBS imaging technique by introducing a sampling laser with a micro-lensed fiber. Through the emission enhancement using the double-pulse laser, we obtained the spectral signal from a sampling crater of less than 500 nanometers in diameter, and visualized the chemical distribution of the self-made grid sample, SIM chip and nano-particles in single cells. The relative limits of detection (RLODs) of In and absolute limits of detection (ALODs) of Al can reach 0.6% and 18.3 fg, respectively.

Applicability of standardless semiquantitative analysis of solids by high-irradiance laser ionization orthogonal time-of-fight mass spectrometry.

A compact high-irradiance laser ionization time-of-flight mass spectrometry system has been developed for the multielemental analysis of solids. Helium was introduced into the ion source as a buffer gas to cool high kinetic energy ions and suppress the interference of multicharged ions. A special pulse train repelling mode was used to achieve explicit spectra. Two quantitative methods are described for the laser ionization mass spectrometry in this paper. The first of these is the routine calibration curve quantitation, in which various matrix-matched standards are required; the second method, which is based on the uniform correlation between the signal and elemental concentration of different samples, is more convenient and covers a typical dynamic range of 6 orders. All the investigations and results indicate satisfactory performance of the newly developed instrument and its applicability for simultaneous multielemental analysis of solid samples.

Femtogram detection and quantitation of residues using laser ionization orthogonal time-of-flight mass spectrometry.

A newly developed high irradiance laser ionization orthogonal time-of-flight mass spectrometer (LI-O-TOFMS) was employed for the elemental analysis of residues, which were prepared by evaporating mixed salt solutions. The residues were first characterized in terms of shape and elemental distribution. In TOFMS detection, all of the metal elements in the residue can be observed in the spectra. Relative sensitivity coefficients for different elements were within 1 order of magnitude, which meets semiquantitative analysis criteria. By calculating the individual masses from the ablated area due to a single laser shot, the absolute detection limit reached 7 x 10(-15) g for most metal elements. The results indicate that LI-O-TOFMS is capable of performing ultratrace elemental qualification and quantification, with an absolute limit of detection and an absolute limit of quantitation at the femtogram level.