Chemiluminescence Instrument Research Articles

Bioinformatics, expression, purification, and inflammation-inducing effect of Mycoplasma genitalium GroEL protein

To preliminarily understand the pathogenic mechanism of Mycoplasma genitalium (Mg) GroEL protein, we used bioinformatics tools to predict the structure and function of Mg GroEL protein and then constructed the recombinant plasmid pET-28a-GroEL. The protein expression was induced by 0.2 mmol/L IPTG, and the expressed protein was purified by Ni-iminodicitic acid (IDA) column affinity. Tohoku Hospital Pediatrics-1 (THP-1) cells were exposed to 2 μg/mL Mg rGroEL. The levels of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in the cell supernatant were measured by ELISA, and that of IL-6 was measured by an automatic chemiluminescence instrument. The activation of the nuclear factor-kappa B (NF-κB) signaling pathway was visualized by immunofluorescence and Western blotting. The results showed that Mg GroEL was a stable hydrophilic protein composed of 543 amino acid residues, with the relative molecular mass of 58.44 kDa, an isoelectric point of 5.68, and a molecular formula of C2568H4300N700O825S8. The secondary structure was mainly composed of α-helices and random coils. Mg GroEL contained 12 B-cell dominant epitopes and 10 T-cell dominant epitopes. It exhibited high homology with the GroEL proteins from Mycoplasma pneumoniae, M. agalactiae, M. arthritidis, M. hyopneumoniae, and M. bovis. Mg rGroEL activated the NF-κB signaling pathway and promoted the secretion of IL-1β, IL-6, and TNF-α in THP-1 cells. These results suggest that Mg GroEL exhibits substantial antigenicity and possesses the capability of triggering inflammation in host cells. This study establishes a theoretical basis for future investigations pertaining to the role and pathogenic mechanisms of Mg GroEL.

Development of a fully automated chemiluminescent immunoassay for the quantitative and qualitative detection of antibodies against African swine fever virus p72.

African swine fever (ASF), caused by ASF virus (ASFV), is a highly infectious and severe hemorrhagic disease of pigs that causes major economic losses. Currently, no commercial vaccine is available and prevention and control of ASF relies mainly on early diagnosis. Here, a novel automated double antigen sandwich chemiluminescent immunoassay (DAgS-aCLIA) was developed to detect antibodies against ASFV p72 (p72-Ab). For this purpose, recombinant p72 trimer was produced, coupled to magnetic particles as carriers and labeled with acridinium ester as a signal trace. Finally, p72-Ab can be sensitively and rapidly measured on an automated chemiluminescent instrument. For quantitative analysis, a calibration curve was established with a laudable linearity range of 0.21 to 212.0 ng/mL (R2 = 0.9910) and a lower detection limit of 0.15 ng/mL. For qualitative analysis, a cut-off value was set at 1.50 ng/mL with a diagnostic sensitivity of 100.00% and specificity of 98.33%. Furthermore, antibody response to an ASF gene-deleted vaccine candidate can be accurately quantified using this DAgS-aCLIA, as evidenced by early seroconversion as early as 7 days post-immunization and high antibody levels. Compared with available enzyme-linked immunosorbent assays, this DAgS-aCLIA demonstrated a wider linearity range of 4 to 16-fold, and excellent analytical sensitivity and agreement of over 95.60%. In conclusion, our proposed DAgS-aCLIA would be an effective tool to support ASF epidemiological surveillance.IMPORTANCEAfrican swine fever virus (ASFV) is highly contagious in wild boar and domestic pigs. There is currently no vaccine available for ASF, so serological testing is an important diagnostic tool. Traditional enzyme-linked immunosorbent assays provide only qualitative results and are time and resource consuming. This study will develop an automated chemiluminescent immunoassay (CLIA) that can quantitatively and qualitatively detect antibodies to ASFV p72, greatly reducing detection time and labour-intensive operation, and improving detection sensitivity and linearity range. This novel CLIA would serve as a reliable and convenient tool for ASF pandemic surveillance and vaccine development.

A-002 Analytical Validation of the Zybio High Sensitivity Cardiac Troponin I CLIA Assay

Abstract Background High-sensitivity cardiac troponin (hs-cTn) plays a pivotal role in the early diagnosis of Acute Coronary Syndrome (ACS). With technological advancements, the sensitivity of troponin assays has significantly improved. The International Federation of Clinical Chemistry (IFCC) criteria for hs-cTn assays include a total imprecision (Coefficient of Variation, CV) ≤10% at the gender-specific 99th percentile value and detectable levels in ≥50% of a healthy population. This study aims to evaluate the performance of Zybio's hs-cTnI assay against these high-sensitivity standards Methods This study involved 1661 individuals undergoing routine health checks at Chongqing Medical University Third Hospital. Exclusion criteria included recent medication use, abnormal NT-proBNP levels, significant cardiac silhouette changes in chest X-rays, age <20, incomplete data, pregnancy, or history of severe chronic diseases. Participants were classified into apparent healthy and healthy groups based on blood pressure, lipid profiles, and electrocardiogram results. Laboratory examinations included hs-cTn and NT-ProBNP concentrations using Zybio's chemiluminescence instrument EXI2400 and associated reagent kits, with other parameters measured using standard biochemical and high-performance liquid chromatography methods. Results Of the 1247 participants (556 males, 691 females) included in the final analysis, 1157 showed detectable hs-cTnI levels above the limit of detection (LOD), yielding an overall detection rate of 92.78%. Detection rates were 93.71% in males and 92.04% in females. The total imprecision (CV) of hs-cTnI at gender-specific 99th percentile values over 20 days was below 10%, meeting the high-sensitivity criteria. This finding was consistent across lower and higher concentration ranges. Conclusions The Zybio hs-cTnI assay demonstrated a high detection rate in a healthy population, with 92.78% detectability overall, 93.71% in males, and 92.04% in females. The assay met the high-sensitivity criteria of IFCC, with a total imprecision (CV) of less than 10% at the gender-specific 99th percentile levels. These results validate the utility of Zybio's hs-cTnI assay for clinical application in the early diagnosis of ACS.

Examination of Tumor-related Biomarkers in Women with Breast Cancer Referred to Naft Hospital of Ahvaz, Southwest Iran

Introduction: Breast cancer is acknowledged as the most prevalent form of cancer in women. The aim of the present study was to examine tumor-related biomarkers such as ER, PR, HER2/neu, P53, Ki-67, CEA, CA-125, and CA 15-3 in women with breast cancer referred to Naft Hospital of Ahvaz, southwest Iran. Methods: This research was a cross-sectional investigation. A total of 100 Iranian women patients were selected who were diagnosed with breast cancer tumors (stage 3). All tumor markers like CEA, CA 15-3, and CA-125 were determined using a chemiluminescent instrument. In addition, the immunohistochemical technique was used to analyze the expression of ER, PR, HER/neu, Ki-67 antigen, and P53 protein. Results: The mean of patients' age was 48.53 ± 9.57 years. ER accounted for the highest frequency (73, or 73%) out of 100 cases. There were 69 (69%), 55 (55%), and 53 (53%) positive cases for PR, HER2/neu, and P53, respectively. The chi-square analysis revealed a significant difference for HER2/neu and P53 biomarkers (p = 0.027). The odds ratio was 2.625 [95% CI: (1.167-5.906)], and the positive correlation between them was 0.236 (p = 0.018). Moreover, a significant difference was found for ER and PR biomarkers (p < 0.0001), and the odds ratio was 18.25 [95% CI: (7.039- 47.319)]. There was a significant positive correlation (r = 0.908, p < 0.0001) between ER and PR. A remarkable positive correlation (r = 0.256, p = 0.010) was also observed between CEA and CA 15-3 biomarkers. Conclusion: Our findings indicated that the highest frequency of tumor-associated biomarkers was ER, and there was a positive correlation between ER and PR, HER2/neu, and P53, as well as CEA and CA 15-3.

Observational Study to Compare Biological Drug Concentration Quantification Techniques and Immunogenicity in Patients with Immune-Mediated Diseases.

Measuring biological drugs' trough concentrations and the concentrations of anti-drug antibodies is a valuable practice for treatment optimization. ELISA techniques are the gold standard for biological drug concentration quantification, but new techniques such as chemiluminescence immunoassays present some advantages. The aim of this unicentric prospective observational study is to compare the infliximab, adalimumab, vedolizumab and ustekinumab trough levels and anti-adalimumab and anti-infliximab antibodies concentrations obtained when using a chemiluminescent instrument (i-TRACK®, Theradiag, Croissy-Beaubourg, France) and an ELISA instrument (TRITURUS®, Griffols, Barcelona, Spain). Linear regression, Pearson or Spearman tests, Bland-Altman plots and the Cohen kappa test were applied for every sample. The correlation was excellent for both assays in the measurement of all drug concentrations. In general, values were lower when measured using i-TRACK than when using TRITURUS, especially when the values were high. Both techniques proved valuable in clinical practice for monitoring adalimumab and infliximab drug concentration. However, the results were modest for ustekinumab and vedolizumab, so caution is recommended and further research is needed. The limited number of anti-drug antibody-positive samples precluded a comparison between the techniques.

A magnetic solid phase chemiluminescent immunoassay for quantification of Cystatin C in human serum

A chemiluminescent immunoassay for human serum Cystatin C (Cys C) was established using a direct-antibody sandwich model. The immunoassay kit uses magnetic separation technology, using magnetic particles as the reaction solid phase, alkaline phosphatase as the marker enzyme, and a new chemiluminescent substrate APLS as the substrate. It has the characteristics of high sensitivity and short reaction time. This product uses high-affinity antibodies, resulting in a high specificity. The established method showed good accuracy, uniformity, and stability. The limit of detection was 2.39 ng/mL. The intra-assay coefficient of variation (CV) was 3.36%–6.00%, the interassay CV was 4.12%–5.35%, and the recovery rate was 99.07%. The correlation coefficient (r) of Cys-C kit was 0.999388 ≥ 0.9900. The accuracy of the developed method was tested by automatic chemiluminescence instrument (P > 0.05). The lowest titer was 0.92500, and the highest was 1.10000. The developed method showed a good correlation with the product from Roche by comparing these two kits in 240 clinical samples from China. In total, 1392 clinical patient from China samples were measured using the reagent kit developed in this study.

Th1 or Th2 cytokines are correlated with Tregs and T cell subsets and pregnancy outcomes in patients with autoimmune thyroid disease during early, middle, late pregnancy, and postpartum period

Autoimmune thyroid disease (AITD) is a T lymphocytes-mediated autoimmune disorder affecting pregnant women. The current study sought to determine the correlations between T helper-1 (Th1)/T helper-2 (Th2) cytokines and regulatory T cells (Tregs) and T cell subsets and pregnancy outcomes in AITD patients during early pregnancy (T1), middle pregnancy (T2), late pregnancy (T3), and postpartum period (PP). A total of 60 patients with Graves’ disease, 60 patients with Hashimoto’s thyroiditis, and 30 healthy pregnant women were initially enrolled in the study. Thyroid hormones and antibodies, Th1 or Th2 cytokines, transforming growth factor-β, Tregs, CD4+ T helper cells (CD4+), CD8+ T helper cells (CD8+) levels were determined by means of Maglumi2000 automatic chemiluminescence instrument, enzyme-linked immunosorbent assay, and flow cytometry. Our findings demonstrated higher IFN-γ and IL-2 levels, along with lower IL-4, IL-10, TGF-β, Treg, and CD4+/CD8+ levels in AITD patients during T1, T2, T3, and PP. Furthermore, the TGF-β, Treg, and CD4+/CD8+ levels were lower in the IFN-γ/IL-2 high expression group but higher in the IL-4/IL-10 high expression group. The IFN-γ and IL-2 levels were higher, while IL-4 and IL-10 level were lower in AITD patients with adverse pregnancy outcomes. Lastly, Th1 cytokines were higher and Th2 cytokines were lower in AITD patients and elicited correlation with Tregs and CD4+/CD8+ levels. Collectively, our findings highlighted that up-regulation of Th1 cytokines may increase the percentage of adverse pregnancy outcomes in AITD patients.

Shrink polymer based electrochemical sensor for point-of-care detection of prostate-specific antigen

There is a growing but unmet need for point-of-care detection of prostate-specific antigen (PSA) in body fluid which may facilitate early diagnosis and therapy of prostate cancer in a cost-effective and user-friendly way. Low sensitivity and narrow detection range limits applications of point-of-care testing in practice. Here, an immunosensor is first presented based on shrink polymer and integrated into a miniaturized electrochemical platform for detecting PSA in clinical samples. The sensing electrode was prepared by sputtering a gold film on shrink polymer, followed by heating to shrink the electrode to a small size with wrinkles from nano-scale to micro-scale. These wrinkles can be directly regulated by the thickness of the gold film with high specific areas for enhancement of antigen-antibody binding (3.9 times). A distinct difference between electrochemical active surface area (EASA) and response to PSA of shrink electrodes was observed and discussed. The electrode was treated with air plasma and modified with self-assembled graphene to further enhance the sensor's sensitivity (10.4 times). The shrink sensor with gold 200 nm thick integrated into the portable system was validated by a label-free immunoassay for detection of PSA in 20 μL serum within 35 mins. It exhibited a limit of detection of 0.38 fg/mL, the lowest among label-free PSA sensors, and a wide linear response from 10 fg/mL to 1000 ng/mL. Moreover, the sensor demonstrated reliable assay results in clinical serums, comparable to the commercial chemiluminescence instrument, confirming its feasibility for clinical diagnosis.

Diagnostic efficacy of contrast-enhanced ultrasound, dynamic contrast-enhanced MRI combined with tumor markers AFP and DCP for primary hepatocellular carcinoma

ABSTRACT The purpose of this study was to investigate the diagnostic efficacy of contrast-enhanced ultrasound (CEUS) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) combined with tumor markers alpha-fetoprotein (AFP) and des-γ-carboxyl prothrombin (DCP) for primary hepatic carcinoma (PHC). A total of 70 patients with PHC (PHC group), 42 patients with liver cyst (benign liver disease group (BLDG)) and 30 healthy people (healthy group (HG)) were selected as the research objects. CEUS and DCE-MRI were performed by American GE Vivid E9 color Doppler ultrasound system and Siemens 1.5T magnetic resonance imager, respectively. The levels of AFP and DCP were detected by ABBOTT i2000SR chemiluminescence instrument and enzyme-linked immunoassay (ELISA), respectively. In DCE-MRI examination, the portal phase and prolonged phase were mostly low signal in T1-weighted imaging (T1WI) sequence, and arterial phase was mostly high signal in T2WI sequence. In CEUS, most lesions showed hyper-enhancement in arterial phase, and hypo-enhancement in portal phase and delayed phase. AFP and DCP levels in PHC group were significantly higher than that in BLDG group and HG group. There were statistically significant differences among the three groups. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of combined diagnosis were statistically significant when compared with CEUS, AFP and DCP alone and either AFP or DCP positive. CEUS, DCE-MRI combined with tumor markers AFP and DCP have high sensitivity, specificity and accuracy in the diagnosis of PHC, which can more accurately diagnose the lesion type, provide basis for further treatment, and is worthy of clinical application.

Chemiluminescence Sensor for miRNA-21 Detection Based on CRISPR-Cas12a and Cation Exchange Reaction

Herein, a chemiluminescence (CL) biosensor based on CRISPR-Cas12a and cation exchange reaction was constructed to detect the biomarker microRNA-21 (miRNA-21). The rolling circle amplification (RCA) reaction was introduced to convert each target RNA strand into a long single-stranded DNA with repeated sequences, which acted as triggers to initiate the transcleavage activity of CRISPR-Cas12a. The activated Cas12a could cleave the biotinylated linker DNA of CuS nanoparticles (NPs) to inhibit the binding of CuS NPs to streptavidin immobilized on the surface of the microplate, which strongly reduced the generation of Cu2+ from a cation exchange between CuS NPs and AgNO3, and thus efficiently suppressed the CL of Cu2+-luminol-H2O2 system, giving a "signal off" biosensor. With the multiple amplification, the detection limit of the developed sensor for miRNA-21 reached 16 aM. In addition, this biosensor is not only suitable for a professional chemiluminescence instrument but also for a smartphone used as a detection tool for the purpose of portable and low-cost assay. This method could be used to specifically detect quite a low level of miRNA-21 in human serum samples and various cancer cells, indicating its potential in ultrasensitive molecular diagnostics.

Validation Study of a New Random-Access Chemiluminescence Immunoassay Analyzer i-TRACK10® to Monitor Infliximab and Adalimumab Serum trough Levels and Anti-Drug Antibodies.

Background. Monitoring of biological TNF inhibitors is a very important tool to guide clinical decisions using specialized algorithms, especially in gastroenterology. A new chemiluminescent instrument (i-TRACK10® from Theradiag) could replace ELISA techniques to calculate the dosage of drugs and anti-drug antibodies. In this bi-centric study, we explored the analytical performances of i-TRACK10® using manual or automated (DS2®) ELISA Lisa-Tracker® assays, and compared the results. Patients and methods. Intra- and inter-run performances were evaluated with i-TRACK10® in two different laboratories and for two different ranges of values for infliximab, adalimumab, and their respective antibodies. Patients’ samples were used in the labs to compare the results obtained between the new instrument and either the manual Lisa-Tracker® or the automated DS2. Results. Intra- and inter-run performances were satisfactory, with values between 1.8% and 16.1% (for inter-run imprecision at low/medium values of infliximab). Results were generally comparable between assays. with the lowest value of correlation at 0.59 (anti-adalimumab dosage between i-TRACK10® and manual ELISA). Most often, values of drugs and anti-drug antibodies were higher with i-TRACK10® than with manual ELISA assay, and correlation values were better with automated ELISA. Agreements were globally acceptable, and the lowest coefficients of 0.7 was obtained for adalimumab values between i-TRACK10® and the two ELISA methods, and for anti-adalimumab values between i-TRACK10® and manual ELISA. The type of assay can potentially induce a change in the class of patients and lead to divergent therapeutic decisions. Conclusions. The new random-access instrument i-TRACK10® presents many advantages in a routine laboratory: rapidity, the possibility of standardization, usability, and expansion of the measurement range. Despite the relatively good agreement of results, it is preferable to use the same assay in longitudinal follow-up of a patient, because quantitative results were not completely equivalent especially for anti-drug antibodies.

Clinical Value of Pepsinogen in the Screening, Prevention, and Diagnosis of Gastric Cancer

To compare the levels of serum pepsinogen (PG) in patients with gastric cancer (GC), patients with atrophic gastritis (AG), and healthy donors. Also, we explored the clinical value of PG detection for the diagnosis and treatment of GC. The PG level in peripheral blood from patients and heathy donors was determined using an Abbott automatic chemiluminescence instrument. The study included 117 patients with GC confirmed by gastroscopy and histopathology, of whom 13 patients had cancer at stage I, 47 at stage II, 41 at stage III, and 16 at stage IV. The AG group included 122 patients, and the control group had 120 healthy donors. The relationship between serum PG levels and the occurrence and development of GC, as well as the evaluation of the clinical value of diagnostic tests based on serum PG detection, were investigated by receiver operating characteristic (ROC) curve analyses. Pepsinogen I (PGI) levels gradually decreased from the control group, the AG group, and the GC group. PGI exhibited high diagnostic value for GC (area under the curve [AUC], 0.834; cutoff, 51.2 ng/mL, sensitivity, 81.7%; specificity, 68.4%), PGII (AUC, 0.587; cutoff value, 13.05 ng/mL; sensitivity, 65.8%; specificity, 53.8%), and PGR (AUC, 0.752; cutoff, 5.65; sensitivity, 54.2%; specificity, 87.2%). The occurrence of GC was negatively correlated with serum levels of PGI (B = -0.054; OR = 0.947; 95% confidence interval [CI], 0.925-0.970; P <.001) and PGR (B = -0.420; OR = 0.657; 95% CI, 0.499-0.864; P = .003). The combined detection of PGI, PGII, and PGR has important clinical value for the screening, prevention, and diagnosis of GC and could allow for earlier detection, diagnosis, and treatment of GC.

Understanding chemiluminescence in catalytic oxidation of CO and hydrocarbons

A chemiluminescence (CL) instrument was developed to understand the CL behavior of catalytic oxidation of CO and hydrocarbons, which are major processes occurring in catalytic converters. The instrument is based on the cooperation among a gas mixer, a custom-made CL analyzer, and an on-line gas chromatography. The concept of the CL method was formulated by thoroughly investigating the CL emission during the catalytic oxidation of CO and C3H6 in the presence of O2 and/or NO under both stoichiometric and non-stoichiometric conditions. All the oxidation reactions were found to be CL-active, where the CL intensity increased exponentially with the temperature. The steady-state measurements showed good linearity between the CL intensity and the reaction rates, demonstrating that the CL emission is a direct product of the reactions. It was also found that the CL intensity per CO2 production was different among the reactions, most plausibly due to both/either the presence of multiple CL processes and/or the difference in the heat of the reactions. Based on the linear correlation between the CL intensity and the reaction rate, a feasibility study was successfully demonstrated for rapid catalyst evaluation in C3H6 oxidation.

The expression and significance of miR-29b and IGF-1 in type 2 diabetes mellitus patients with depression

Objective To detect the levels of serum micro RNA (miRNA) -29b and insulin growth factor-1 (IGF-1) in patients with type 2 diabetes mellitus (T2DM) and depression, and to analyze their clinical significance. Methods 504 patients with T2DM admitted to our hospital from February 2016 to February 2018 were selected, among them, 264 patients without depression, the other 240 patients with depression were selected as the study group, and 200 patients with physical examination were selected as the control group. Serum triglyceride (TG), cholesterol (TC), low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), glycosylated hemoglobin (HbA1c), fasting blood glucose (FPG) were measured by automatic biochemical analyzer. Levels of serum IGF-1 were measured by automatic chemiluminescence instrument in all subjects. The expression of miR-29b in serum was detected by quantitative real-time polymerase chain reaction (qRT-PCR). All subjects were scored with 24 Hamilton Scales (HAMD). Results The serum TC, TG, LDL, FPG, HbA1c, and HAMD scores of patients with depression in T2DM were significantly higher than those of control group and patients with T2DM (P<0.05); the serum TC, TG, FPG, HbA1c of patients with T2DM were significantly higher than those of the control group (P<0.05). The levels of serum miR-29b in patients with T2DM and depression were significantly lower than those in patients with T2DM and control group (P<0.05), while the level of IGF-1 was significantly higher than that in patients with T2DM and in control group (P<0.05); the level of serum miR-29b in patients with T2DM was significantly lower than that in control group (P<0.05), while the level of IGF-1 was significantly higher than that in control group (P<0.05). The levels of serum miR-29b in patients with severe depression and T2DM were significantly lower than those in patients with mild or moderate depression (P<0.05), while the level of IGF-1 showed the opposite (P<0.05). There was a significant negative correlation between serum miR-29b and IGF-1 level in patients with T2DM and depression (P<0.05). Logistic regression analysis showed that high levels of serum HbA1c (≥11.06%) and IGF-1 (≥25.74 ng/ml) were risk factors for depression in patients with T2DM, and high level of serum miR-29b (≥0.39) was protective (P<0.05). Conclusions The serum levels of IGF-1 increased and miR-29b decreased in patients with type 2 diabetes mellitus and depression. Serum levels of miR-29b were negatively correlated with the levels of IGF-1. High levels of IGF-1 were risk factors for depression in patients with type 2 diabetes mellitus, and high levels of miR-29b were protective factors. Key words: MicroRNAs; Insulin-like growth factor I; Diabetes mellitus, type 2; Depressive disorder

NOx instrument intercomparison for laboratory biomass burning source studies and urban ambient measurements in Albuquerque, New Mexico

ABSTRACTUnderstanding nitrogen oxides (NOx = NO + NO2) measurement techniques is important as air-quality standards become more stringent, important sources change, and instrumentation develops. NOx observations are compared in two environments: source testing from the combustion of Southwestern biomass fuels, and urban, ambient NOx. The latter occurred in the urban core of Albuquerque, NM, at an EPA NCORE site during February–March 2017, a relatively clean photochemical environment with ozone (O3) <60 ppb for all but 6 hr. We compare two techniques used to measure NOx in biomass smoke during biomass burning source testing: light absorption at 405 nm and a traditional chemiluminescence monitor. Two additional oxides of nitrogen techniques were added in urban measurements: a cavity attenuated phase shift instrument for direct NO2, and the NOy chemiluminescence instrument (conversion of NOy to NO by molybdenum catalyst). We find agreement similar to laboratory standards for NOx, NO2, and NO comparing all four instruments (R2 > 0.97, slopes between 0.95 and 1.01, intercepts < 2 ppb for 1-hr averages) in the slowly varying ambient setting. Little evidence for significant interferences in NO2 measurements was observed in comparing techniques in late-winter urban Albuquerque. This was also confirmed by negligible NOz contributions as measured with an NOy instrument. For the rapidly varying (1-min) higher NOx concentrations in biomass smoke source testing, larger variability characterized chemiluminescence and absorption instruments. Differences between the two instruments were both positive and negative and occurred for total NOx, NO, and NO2. Nonetheless, integrating the NOx signals over an entire burn experiment and comparing 95 combustion experiments, showed little evidence for large systematic influences of possible interfering species biasing the methods. For concentrations of <2 ppm, a comparison of burn integrated NOx, NO2, and NO yielded slopes of 0.94 to 0.96, R2 of 0.83 to 0.93, and intercepts of 8 to 25 ppb. We attribute the latter, at least in part, to significant noise particularly at low NOx concentrations, resulting from short averaging times during highly dynamic lab burns. Discrepancies between instruments as indicated by the intercepts urge caution with oxides of nitrogen measurements at concentrations <50 ppb for rapidly changing conditions.Implications: Multiple NOx measurement methods were employed to measure NOx concentrations at an EPA NCORE site in Albuquerque, NM, and in smoke produced by the combustion of Southwestern biomass fuels. Agreement shown during intercomparison of these NOx techniques indicated little evidence of significant interfering species biasing the methods in these two environments. Instrument agreement is important to understand for accurately characterizing ambient NOx conditions in a range of environments.

Field Measurement of NO2 and RNO2 by Two-Channel Thermal Dissociation Cavity Ring Down Spectrometer

A two-channel thermal dissociation cavity ring down spectroscopy (CRDS) instrument has been built for in situ, real-time measurement of NO2 and total RNO2 (peroxy nitrates and alkyl nitrates) in ambient air, with a NO2 detection limit of 0.10 ppbv at 1 s. A 6-day long measurement was conducted at urban site of Hefei by using the CRDS instrument with a time resolution of 3 s. A commercial molybdenum converted chemiluminescence (Mo-CL) instrument was also used for comparison. The average RNO2 concentration in the 6 days was measured to be 1.94 ppbv. The Mo-CL instrument overestimated the NO2 concentration by a bias of +1.69 ppbv in average, for the reason that it cannot distinguish RNO2 from NO2. The relative bias could be over 100% during the afternoon hours when NO2 was low but RNO2 was high.

Characterization and mitigation of water vapor effects in the measurement of ozone by chemiluminescence with nitric oxide

Abstract. Laboratory experiments were conducted to investigate the effects of water vapor on the reaction of nitric oxide with ozone in a gas-phase chemiluminescence instrument used for fast response and high sensitivity detection of atmospheric ozone. Water vapor was introduced into a constant level ozone standard and both ozone and water vapor signals were recorded at 10 Hz. The presence of water vapor was found to reduce, i.e. quench, the ozone signal. A dimensionless correction factor was determined to be 4.15 ± 0.14 × 10−3, which corresponds to a 4.15% increase in the corrected ozone signal per 10 mmol mol−1 of co-sampled water vapor. An ozone-inert water vapor permeable membrane (a Nafion dryer with a counterflow of dry air from a compressed gas cylinder) was installed in the sampling line and was shown to remove the bulk of the water vapor in the sample air. At water vapor mole fractions above 25 mmol mol−1, the Nafion dryer removed over 75% of the water vapor in the sample. This reduced the required ozone signal correction from over 11% to less than 2.5%. The Nafion dryer was highly effective at reducing the fast fluctuations of the water vapor signal (more than 97%) while leaving the ozone signal unaffected, which is a crucial improvement for minimizing the quenching interference of water vapor fluxes and required density correction in the determination of ozone fluxes by the eddy covariance technique.

Comparison of the Rancimat and the ACL Instrument for Measuring the Oxidative Stability of Corn Oil

AbstractA comparison was undertaken between two machines that utilise accelerated methods to measure oxidative stability: the Rancimat (Metrohm, Switzerland) and the single channel chemiluminescence instrument (ACL Instruments, Switzerland). The results from the machines showed good correlation for the measurement of the oxidation induction time of corn oil. For the ACL Instrument, the effect of the sample holder material (aluminium or borosilicate glass) was also investigated and clear differences were noted. Finally, a stability study was carried out over a period of 6 months, with corn oil, stored in the dark at three temperatures: ~4, ~27, ~40 °C and it was observed that it was possible to track subtle changes in oxidative stability using chemiluminescence.

Ozone dynamics and snow‐atmosphere exchanges during ozone depletion events at Barrow, Alaska

The behavior of lower atmospheric ozone and ozone exchanges at the snow surface were studied using a suite of platforms during the Ocean‐Atmosphere‐Sea Ice‐Snow (OASIS) Spring 2009 experiment at an inland, coastal site east of Barrow, Alaska. A major objective was to investigate if and how much chemistry at the snow surface at the site contributes to springtime ozone depletion events (ODEs). Between March 8 and April 16, seven ODEs, with atmospheric ozone dropping below 1.0 ppbv, were observed. The depth of the ozone‐depleted layer was variable, extending from the surface to ∼200–800 m. ODEs most commonly occurred during low wind speed conditions with flow coming from the Arctic Ocean. Two high‐sensitivity ozone chemiluminescence instruments were used to accurately define the remaining sub‐ppbv ozone levels during ODEs. These measurements showed variable residual ODE ozone levels ranging between 0.010 and 0.100 ppbv. During the most extended ODE, when ozone remained below 1.0 ppbv for over 78 h, these measurements showed a modest ozone recovery or production in the early afternoon hours, resulting in increases in the ozone mixing ratio of 0.100 to 0.800 ppbv. The comparison between high‐sensitivity ozone measurements and BrO measured by longpath differential absorption spectroscopy (DOAS) during ODEs indicated that at low ozone levels formation of BrO is controlled by the amount of available ozone. Measurements of ozone in air drawn from below the snow surface showed depleted ozone in the snowpack, with levels consistently remaining &lt;6 ppbv independent of above‐surface ambient air concentrations. The snowpack was always a sink of ozone. Ozone deposition velocities determined from ozone surface flux measurements by eddy covariance were on the order of 0.01 cm s−1, which is of similar magnitude as ozone uptake rates found over snow at other polar sites that are not subjected to ODEs. The results from these multiple platform measurements unequivocally show that snow‐atmosphere chemical exchanges of ozone at the measurement site do not exhibit a major contribution to ozone removal from the boundary layer and the formation of ODE.

A fast and precise chemiluminescence ozone detector for eddy flux and airborne application

Abstract. A commercially available dry chemiluminescence (CI) instrument for fast and precise measurement of ozone (O3) is specified. The sensitivity is ~9000 counts s−1 per ppbv of ozone. Its precision is entirely determined by the number of photons reaching the detector (being a photomultiplier), i.e. is quantum-noise limited. The relative precision (ΔO3/O3 in %) thus follows Poisson statistics and scales with the square root of the measurement frequency f and with the inverse O3 mixing ratio: ΔO3/O3 ∝ f0.5 · O3−0.5. At typical O3 mixing ratios between 10 and 100 ppbv (and 1 bar), the precision is 0.3–1.0% at f = 10 Hz. The maximum measurement frequency is 50 Hz. The mechanical and electronic set-up as well as the instrument performance is described. Recommendations on the adequate inlet tube configuration (inlet tube length, sampling flow) and on the way of calibration at stationary ground-based platforms and onboard aircraft are given.