Dilution Liquid Chromatography-tandem Mass Spectrometry Research Articles

Neonatal vitamin D status in relation to autism spectrum disorder and developmental delay in the CHARGE case-control study.

Vitamin D appears essential for normal neurodevelopment and cognitive and behavioral function. We examined neonatal vitamin D in relation to the child's later diagnosis of autism spectrum disorder (ASD) or developmental delay (DD). Children aged 24-60 months enrolled in the population-based CHARGE case-control study were evaluated clinically for ASD (n = 357), DD (n = 134), or typical development (TD, n = 234) at the MIND Institute (Sacramento, CA) using standardized assessments. Total 25-hydroxyvitamin D (25[OH]D) was measured using sensitive isotope dilution liquid chromatography-tandem mass spectrometry in archived dried blood spots collected for the California Department of Public Health's Newborn Screening Program. Multinomial logistic regression was used to calculate ORs as measures of the associations between 25 nmol/L change in 25(OH)D and ASD and DD. Associations between 25(OH)D and scores on Mullen Scales of Early Learning and Vineland Adaptive Behavior Scales were assessed using robust linear regression. Effect modification was examined using stratified models and interaction product terms. Unadjusted mean (SD) 25(OH)D was lower for DD (73.2 [37.6]) than for TD (82.7 [39.3]) and ASD (80.1 [37.4]). After adjustment for maternal prepregnancy body mass index and education, a 25 nmol/L increase in total 25(OH)D was not associated with ASD (OR = 0.97; CI: 0.87-1.08) or DD (OR = 0.91; 95% CI: 0.78-1.06). Neonatal 25(OH)D was associated with significantly reduced ASD only in females (adjusted OR = 0.74; 95% CI: 0.55-0.99, Pinteraction = 0.03), and significantly reduced DD only in non-Hispanic white children (adjusted OR = 0.79; 95% CI: 0.63-0.98, Pinteraction = 0.11 for Hispanic, Pinteraction = 0.31 for other), driven by DD children with trisomy 21. This study provides evidence that neonatal vitamin D could be associated with ASD in females and with DD in non-Hispanic white children. Autism Res 2019, 12: 976-988. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Vitamin D appears essential for brain development and function. We examined neonatal total 25-hydroxyvitamin D (25[OH]D) measured in dried blood spots in relation to later diagnoses of autism spectrum disorder (ASD) or developmental delay (DD) and related assessment scores. Higher neonatal 25(OH)D was associated with a 26% reduction in the odds for ASD only in females. After taking into account factors that could contribute to vitamin D status, a significant association with 21% reduced odds for DD was found only in non-Hispanic white children. Though results were nonsignificant overall, certain subgroups might benefit from higher neonatal vitamin D.

Analytical Method of Multi-Mycotoxins in Table-Ready Foods for a Total Diet Study Using Stable Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry.

Background: Determining the multi-mycotoxins present in table-ready foods is necessary for a total diet study. However, so far, most methods of analyzing multi-mycotoxins apply to raw foods. Therefore, a reliable method for analyzing multi-mycotoxins in table-ready foods is needed. Objective: We developed and validated methods of multi-mycotoxin analysis that employed stable isotope dilution with LC-tandem MS (LC-MS/MS) using two representative matrices. Methods: Samples were fortified with [13C]-labeled mycotoxins as internal standards and extracted with 50% acetonitrile in water for high-carbohydrate foods and 3% formic acid in acetonitrile for high-protein and/or high-fat foods, cleaned up with n-hexane and the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, and followed up by LC-MS/MS. Results: Validation of the methods was performed, and the results were as follows: the correlation coefficient, R², was 0.99; method detection limit, 0.01-2.4 μg/kg; recoveries, 83.6-114%; precision, 0.8-10 (intraday) and 3.1-22% (interday); interlaboratory reproducibility, ≤15%; and uncertainty, 3.5-19%error. The applicability of the methods was evaluated by analyzing table-ready foods spiked with standards. Conclusions: These methods were successfully evaluated and deemed appropriate for determining the multi-mycotoxins in table-ready foods. Highlights: This work demonstrates that stable isotope dilution with LC-MS/MS can be effectively used to analyze multi-mycotoxins simultaneously in a total diet study.

Identification and quantification of isoguanosine in humans and mice

Isoguanine (2-hydroxyadenine), considered to be a non-natural nucleobase has, however, been shown to occur in the croton bean, butterfly wings and a mollusk. For the first time, to the best of our knowledge, we report the identification of isoguanosine (2-hydroxyadenosine), the ribonucleoside, in humans and mouse. Isoguanosine is identified and quantified in RNA from mouse liver samples and in human urine and cerebrospinal fluid. Isoguanine could not be detected as the 2′-deoxyribonucleoside in mouse liver DNA. It could be speculated that the source of isoguanosine was formation from adenosine during oxidative stress in the body. However, the urinary concentrations of isoguanosine and the levels in the liver found here by using isotope dilution liquid chromatography–tandem mass spectrometry are identical to or exceed those of 8-oxo-7,8-dihydro-2′-deoxyguanosine and 8-oxo-7,8-dihydro-guanosine. Guanine is the nucleobase that is oxidized the easiest, so it appears spectacular that the levels of isoguanosine are higher than the levels of 8-oxo-7,8-dihydro-2′-deoxyguanosine and 8-oxo-7,8-dihydro-guanosine. It also appears intriguing that it was only possible to detect the ribonucleoside isoguanosine and not the 2′-deoxyribonucleoside. These observations could indicate that the isoguanosine found is not formed by oxidative stress and could have biological functions.

Corbicula fluminea rapidly accumulate pharmaceuticals from an effluent dependent urban stream

Corbicula fluminea rapidly accumulate pharmaceuticals from an effluent dependent urban stream

Development and validation of a simple isotope dilution-liquid chromatography-tandem mass spectrometry method for detecting vitamins A and E in serum and amniotic fluid

Development and validation of a simple isotope dilution-liquid chromatography-tandem mass spectrometry method for detecting vitamins A and E in serum and amniotic fluid

Plasma concentration of trimethylamine-N-oxide and risk of gestational diabetes mellitus

Plasma concentration of trimethylamine-N-oxide and risk of gestational diabetes mellitus

Indoor, outdoor, and night work and blood concentrations of vitamin D and parathyroid hormone.

Objectives The aim of this study was to examine blood concentrations of 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) among indoor, outdoor, permanent and rotating night workers and the association with hours spent outdoors on and off work days. Methods Blood samples were collected from 425 workers (162 indoor, 112 outdoor, 118 rotating night and 33 permanent night workers) throughout all seasons. Serum concentrations of 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) were analyzed by isotope dilution liquid chromatography-tandem mass spectrometry (LC MS/MS) and an automated immune analyzer, respectively. Personal light exposure levels were continuously recorded and used to estimate hours spent outdoors (all workers). Results Permanent night workers had 25.3% (95% CI 11.9-36.6) lower 25OHD concentration, 4.55 (95% CI 1.39-14.94) higher odds of vitamin D insufficiency (<50 nmol/L) and 14.5% [95% confidence interval (CI) 0.1-31.1] higher PTH concentration than indoor workers. Outdoor workers had similar 25OHD concentrations but 7.5% (95% CI -0.5-14.9) lower PTH concentration compared to indoor workers. Rotating night workers 25OHD and PTH concentrations did not differ from indoor workers. Concentration of 25OHD increased by 5.2% (95% CI 1.1-9.5) per hour spent outdoor at workdays in the summer. Conclusion Clinicians should be aware that vitamin D insufficiency may be more prevalent among permanent night workers and human resources should consider the positive effect of allowing workers to spend time outdoor during work hours.

The internal standard diquat-d4 causes errors in diquat analysis by LC–MS/MS

We report a more reliable method for determination of the herbicide diquat (DQ) in human biological samples using stable isotope dilution liquid chromatography–tandem mass spectrometry (LC–MS/MS). DQ-d8, a newly synthesized stable isotope was used as the internal standard (IS) for quantification of DQ instead of DQ-d4 typically used so far. The use of DQ-d8 could completely prevent errors like the misdetection of DQ and inaccurate quantification probably caused by using DQ-d4. Additionally, we developed a method for simultaneous determination of DQ and the similar herbicide paraquat (PQ) in urine, serum and whole blood by stable isotope dilution LC–MS/MS after solid-phase extraction. The stable isotopes DQ-d8 and PQ-d6 were synthesized and used as ISs. The DQ and PQ in the samples were extracted by solid-phase extraction using an EVOLUTE® WCX. The extracted DQ and PQ were separated and detected by LC–MSMS using a ZIC®-pHILIC column. The recovery rates ranged from 82.0 to 99.7%. Calibration curves showed good linearity in the 0.01–2 μg/mL. The intraday accuracy and intraday precision [% relative standard deviation (RSD)] ranged from 92.1 to 106% and from 0.4 to 4.7%, respectively. The interday precision (%RSD) ranged between 0.8 and 6.7%. The stable isotopes DQ-d8 and PQ-d6 allowed for accurate and precise quantification. Especially for analysis of DQ, the use of DQ-d8 could completely prevent errors caused by using DQ-d4. Therefore, the proposed method would be of great use in criminal investigations and emergency medicine.

Mycotoxins in infant/toddler foods and breakfast cereals in the US retail market

ABSTRACTThe objective of this study was to conduct a mycotoxin survey of commercial infant/toddler foods (cereals and teething biscuits) and breakfast cereals in the United States. A total of 215 retail samples were collected from three geographical locations and analysed for aflatoxins, fumonisins, deoxynivalenol, HT-2 toxin, ochratoxin A, T-2 toxin, and zearalenone using a stable isotope dilution liquid-chromatography tandem mass spectrometry (LC-MS/MS) method. One or more mycotoxins were found in 69% (101/147) of the infant/toddler foods and 50% (34/68) of breakfast cereals. Mycotoxin co-occurrence was observed in 12% of infant/toddler foods and 32% of breakfast cereals. However, the concentrations of detected mycotoxins were lower than the current FDA action and guidance levels. Aflatoxins and HT-2 toxin were not detected in any of the samples, while deoxynivalenol was the most frequently detected mycotoxin. Rice-based cereals appeared to be less susceptible to mycotoxin contamination than other cereal types.

Improved LC-MS/MS method for the quantification of hepcidin-25 in clinical samples.

Mass spectrometry-based methods play a crucial role in the quantification of the main iron metabolism regulator hepcidin by singling out the bioactive 25-residue peptide from the other naturally occurring N-truncated isoforms (hepcidin-20, -22, -24), which seem to be inactive in iron homeostasis. However, several difficulties arise in the MS analysis of hepcidin due to the "sticky" character of the peptide and the lack of suitable standards. Here, we propose the use of amino- and fluoro-silanized autosampler vials to reduce hepcidin interaction to laboratory glassware surfaces after testing several types of vials for the preparation of stock solutions and serum samples for isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS). Furthermore, we have investigated two sample preparation strategies and two chromatographic separation conditions with the aim of developing a LC-MS/MS method for the sensitive and reliable quantification of hepcidin-25 in serum samples. A chromatographic separation based on usual acidic mobile phases was compared with a novel approach involving the separation of hepcidin-25 with solvents at high pH containing 0.1% of ammonia. Both methods were applied to clinical samples in an intra-laboratory comparison of two LC-MS/MS methods using the same hepcidin-25 calibrators with good correlation of the results. Finally, we recommend a LC-MS/MS-based quantification method with a dynamic range of 0.5-40μg/L for the assessment of hepcidin-25 in human serum that uses TFA-based mobile phases and silanized glass vials. Graphical abstract Structure of hepcidin-25 (Protein Data Bank, PDB ID 2KEF).

At the Intersection of Urbanization, Water, and Food Security: Determination of Select Contaminants of Emerging Concern in Mussels and Oysters from Hong Kong.

Aquaculture, which is growing 3-5 times faster than terrestrial agriculture, will play an important role to meet future global food production needs. However, over 80% of global sewage production is returned to the environment untreated or poorly treated. In developing nations, these nontraditional waters of diverse quality are being recycled for aquaculture, yet chemical residues are differentially studied. Here, we examined pharmaceuticals, pesticides, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), and flame retardants in marine bivalves using isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) and low-pressure gas chromatography-tandem mass spectrometry (LP GC-MS/MS). Green-lipped mussels from the field and oysters from aquaculture net pens, which are harvested as food products, were collected adjacent to point source municipal wastewater and landfill leachate effluent discharges, respectively, in Hong Kong, the fourth most densely populated country in the world. Multiple classes of pharmaceutical, pesticides, PAHs, and phosphorus-based flame retardants were detected at low μg/kg levels. Acceptable servings per week indicated minimal risk for a number of chemicals; however, such calculations could not be performed for other contaminants of emerging concern. Future efforts are needed to better understand contaminant influences on marine bivalve populations and aquaculture product safety, particularly in rapidly urbanizing regions of developing countries with limited wastewater infrastructure.

Quantification of cardiac troponin I in human plasma by immunoaffinity enrichment and targeted mass spectrometry.

Quantification of cardiac troponin I (cTnI), a protein biomarker used for diagnosing myocardial infarction, has been achieved in native patient plasma based on an immunoaffinity enrichment strategy and isotope dilution (ID) liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The key steps in the workflow involved isolating cTnI from plasma using anti-cTnI antibody coupled to magnetic nanoparticles, followed by an enzymatic digestion with trypsin. Three tryptic peptides from cTnI were monitored and used for quantification by ID-LC-MS/MS via multiple reaction monitoring (MRM). Measurements were performed using a matrix-matched calibration system. NIST SRM 2921 Human Cardiac Troponin Complex acted as the calibrant and a full-length isotopically labeled protein analog of cTnI was used as an internal standard. The method was successfully demonstrated on five patient plasma samples, with cTnI concentrations measuring between 4.86μg/L and 11.3μg/L (signifying moderate myocardial infarctions). LC-MS/MS measurement precision was validated by three unique peptides from cTnI and two MRM transitions per peptide. Relative standard deviation (CV) from the five plasma samples was determined to be ≤14.3%. This study has demonstrated that quantification of cTnI in native plasma from myocardial infarction patients can be achieved based on an ID-LC-MS/MS method. The development of an ID-LC-MS/MS method for cTnI in plasma is a first step for future certification of matrix-based reference materials, which may be used to help harmonize discordant cTnI clinical assays. Graphical abstract A schematic of the workflow for measuring cardiac troponin I (cTnI), a low-abundant protein biomarker used for diagnosing myocardial infarction, in human plasma by isotope-dilution LC-MS/MS analysis.

Quantification of estrogens in infant formulas by isotope dilution liquid chromatography-tandem mass spectrometry

Isotope dilution liquid chromatography-tandem mass spectrometry without any derivatization step was developed to screen estrogens in real infant formula samples.

Analysis of chloramphenicol in drinking water using an evaporation preparative step and isotope dilution liquid chromatography–tandem mass spectrometry

A reliable isotope dilution method for the determination of chloramphenicol (CAP) in drinking water was developed by using an evaporation preparative step. Each sample was monitored by ultrahigh-pressure liquid chromatography (UHPLC) coupled to tandem mass spectrometry (MS/MS) using an electrospray ionization interface (ESI) in negative ion modes. Recoveries of spiked samples were in the range from 93.2% to 95.7% with intra-day relative standard deviation lower than 6.7% and inter-day relative standard deviation lower than 8.2%. Limit of quantification (LOD) was 0.002 ng/mL. The developed method was successfully applied to the analysis of CAP in drinking water of Shannan region of Tibet.

Simultaneous analysis of six aldehyde-DNA adducts in salivary DNA of nonsmokers and smokers using stable isotope dilution liquid chromatography electrospray ionization-tandem mass spectrometry.

Simultaneous analysis of six aldehyde-DNA adducts in salivary DNA of nonsmokers and smokers using stable isotope dilution liquid chromatography electrospray ionization-tandem mass spectrometry.

Androstenedione and testosterone levels correlate with in vitro fertilization rates in insulin-resistant women

BackgroundThe free androgen index (FAI) calculated using total testosterone measured by immunoassay does not correlate with oocyte fertilization rates; however, there is considerable cross-reactivity for testosterone with other androgens by...

Identification and Quantification of Dityrosine in Grain Proteins by Isotope Dilution Liquid Chromatography-Tandem Mass Spectrometry

A novel liquid chromatography-tandem mass spectrometry method was developed and validated for identification and quantification of dityrosine in zein protein. The zein samples spiked with a dityrosine standard and 3,3-13C6-dityrosine, as the internal standard were hydrolysed in a mixture of 6 N hydrochloric acid and propionic acid followed by cleaning-up using Sep Pak C18 cartridges. Good linear regression (R 2 = 0.999) was obtained in the range 1–1000 ng/mL. Method limit of detection and method limit of quantification were 42.1 and 140 ng/g, respectively. Recoveries were from 92 to 95.2%. Precision and inter-day reproducibility expressed as relative standard deviation were from 3.9 to 22.1% and from 4.4 to 16.6%, respectively. The validated method was applied to quantify dityrosine in various grain proteins. The levels of dityrosine ranged from 0.38 to 1.92 ng/mg. This validated method will be of great value for understanding the role of dityrosine in grain food texture.

Assessing Volumetric Absorptive Microsampling Coupled with Stable Isotope Dilution Assay and Liquid Chromatography-Tandem Mass Spectrometry as Potential Diagnostic Tool for Whole Blood 5-Methyltetrahydrofolic Acid.

Volumetric absorptive microsamplers (VAMS) have been developed recently as a promising tool for clinical blood sampling. Compared to dried blood spot samples analyzed by accurate stable isotope dilution assays (SIDAs), the new technique could provide further substantial miniaturizing of folate assays by eliminating hematocrit effects and uneven analyte distribution within the sample. Herein, we present a miniaturized SIDA coupled with LC-MS/MS measurement of 5-methyltetrahydrofolic acid as main folate vitamer in whole blood (WB) using [13C5]-5-methyltetrahydrofolic acid as internal standard. Elution and extraction of only 10.8 μL-dried WB were carried out by centrifugation followed by enzymatic treatment for polyglutamate deconjugation. Matrix separation was achieved by heating and centrifugation. To verify applicability, WB folate status of 11 volunteers was screened. Limits of detection and limits of quantitation were 9 and 26 nmol·L−1, respectively, which is sufficiently low for screening folate status. Recoveries were 97 (±5.8), 99 (±2.8), and 96 (±6.1)% for 800, 400, and 200 nmol L−1 5-methyltetrahydrofolic acid, respectively. Precision of the LC-MS/MS instrument and inter-assay precision trials revealed CVs of 8.1 and 3.5% (294 nmol L−1), respectively, thus confirming reproducible and precise quantitation. Compared to fresh WB, no significant degradation of 5-methyltetrahydrofolate was observed after 2.5 h of drying at room temperature. VAMS 5-CH3-H4folate was stable for at least 3 weeks at −20°C. In our pilot study, accurate and diagnostically conclusive determination of folate status was verified. Nevertheless, blood sampling should be performed by trained individuals to avoid substantial errors concerning the absorbed volume. Endogenous folate in rat serum and chicken pancreas caused a significant background especially at low blood 5-CH3-H4folate levels and, thus, for polyglutamate deconjugation, these background folates or alternative mixtures need to be removed. The superior feasibility of a minimized blood collection with VAMS allows further progress regarding time- and cost-effective methodologies in newborn or population screenings for 5-methyltetrahydrofolate status. Further steps toward minimization could include an automated assay coupled with UPLC-MS/MS.

Targeted lipidomics profiling of acute arsenic exposure in mice serum by on-line solid-phase extraction stable-isotope dilution liquid chromatography-tandem mass spectrometry.

Lipidomics is the area of study dedicated to the comprehensive analysis and characterization of the functions and metabolism of lipids in biological samples. One of the most comprehensively studied classes of lipids is polyunsaturated fatty acids (PUFAs). Eicosanoids are a series of bioactive lipid mediators that are metabolized from PUFAs and generated majorly from the precursor arachidonic acid. This study identified the profiles of target eicosanoids after acute exposure to arsenic. The principle objective was to determine and validate 10 eicosanoids in mouse serum using on-line solid-phase extraction integrated with liquid chromatography-electrospray tandem mass spectrometry. Intra-day and inter-day repeatability was 82.4-119.2 and 86.7-124.4%, respectively. The limit of detection and limit of quantification were from 0.003 to 0.288ng/mL and from 0.009 to 0.962ng/mL, respectively. The levels of 7 of the 10 eicosanoids-namely 8-isoPGF2α, PGF2α, PGE2, 13(s)-HODE, 15(s)-HETE, 12(s)-HETE, and 5(s)-HETE-in mouse serum significantly and dose-dependently increased after arsenic exposure compared with the levels in the vehicle control group. To our knowledge, this is the first study to quantify eicosanoids in mouse serum. This approach provides simple sample preparation, small sample volumes, and a precise and accurate method for determining changes in the profile of these eicosanoids in mouse serum after acute exposure to arsenic.

Quantifying bisphenol A in maternal and cord whole blood using isotope dilution liquid chromatography/tandem mass spectrometry and maternal characteristics associated with bisphenol A

Quantifying bisphenol A in maternal and cord whole blood using isotope dilution liquid chromatography/tandem mass spectrometry and maternal characteristics associated with bisphenol A