Photon-counting microcolorimeter with 40-nl cuvette

1991 ◽  
Vol 261 (1) ◽  
pp. F203-F206
Author(s):  
T. L. Pallone
Keyword(s):  
Lower Limit ◽  
Plasma Volume ◽  
Fiber Optic ◽  
Limit Of Detection ◽  
Photon Counting ◽  
Injection Port ◽  
Photon Counter ◽  
Sample Injection ◽  
Lowry Assay

A colorimeter with a 40-nl cuvette has been constructed. The wall of standard capillary glass was perforated to produce a sample injection port. A section of the capillary glass was drawn to a length of 1/2 cm and 80 microns ID by heating on a microforge. This produced a cuvette volume of approximately 40 nl. Two fiber-optic filaments, 80 microns in diameter, were fixed into the cuvette to transmit and receive light from the sample. The output of the colorimeter was measured with a microscope photon-counting detection assembly. It has been shown that the colorimeter enables a reduction of the plasma volume requirements of the Lowry microprotein assay from several nanoliters to 60 pl. The linearity and reproducibility of the microcolorimeter when used with the Lowry assay has been verified. The colorimeter output is several orders of magnitude above the lower limit of detection of the photon counter.

Skin exposure: requirements to methods determining active ingredient of pesticides in washings

2019 ◽  
pp. 43-48
Author(s):  
V. N. Rakitskii ◽  
N. E. Fedorova ◽  
I. V. Bereznyak ◽  
N. G. Zavolokina ◽  
L. P. Muhina
Keyword(s):  
Lower Limit ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Absorbed Dose ◽  
Ambient Air ◽  
Safety Coefficient ◽  
Limit Value ◽  
Calculated Risk ◽  
Nature Studies ◽  
Active Substances

The article presents results of studies exemplified by diquat on analysis concerning influence of lower limit value of quantitative assessment in washing sample for safety coefficient in exposure and in absorbed dose, if acting substance is absent in workplace ambient air samples and in dermal washings of workers. To control diquat in dermal washings, there is a method based on ion-pair liquid chromatography with ultraviolet detection (working wavelength 310 nm). To concentrate sample, cartridges for solid-phase extraction, containing ion exchange sorbent (Oasis MCX 6cc/500 mg), are used. Lower limit of assessment in washing sample — 0,15 micrograms. Experimentally set washing completeness is within range of 80–92%, standard deviation of repetition is 7,0% at most. The method created was tested in nature studies determining dermal exposure in workers subjected to 5 various preparations based on diquat dibromide when used for surface spraying from tractor and from aircraft. For lower limit of detection in washing sample (0,15 micrograms/washing), calculated risk value of exposure varied within 0,26–0,36; risk of absorbed dose was low — 0,23 (the allowable one ≤1). Findings are that present measuring methods which provide lower limit of detection 1 and 5 micrograms in washing sample could result in unallowable risk establishment even with absence of the substance in all samples of workplace air and dermal washings. The calculation formula suggested enables to give theoretic basis for requirements to lower limit of detecting active substances in dermal washing samples for evaluating risk of pesticides use in agriculture.

Eco-Friendly Green Liquid Chromatographic Separations of a Novel Combination of Azelastine and Fluticasone in the Presence of their Pharmaceutical Dosage form Additives

2020 ◽  
Vol 16 (3) ◽  
pp. 277-286
Author(s):  
Amal A. El-Masry ◽  
Mohammed E. A. Hammouda ◽  
Dalia R. El-Wasseef ◽  
Saadia M. El-Ashry
Keyword(s):  
Lower Limit ◽  
Dosage Form ◽  
Limit Of Detection ◽  
Sodium Dodecyl ◽  
Uv Detection ◽  
Simultaneous Estimation ◽  
Limit Of Quantification ◽  
Chromatographic Separations ◽  
Pharmaceutical Dosage Form ◽  
Liquid Chromatographic

Background: The first highly sensitive, rapid and specific green microemulsion liquid chromatographic (MELC) method was established for the simultaneous estimation of fluticasone propionate (FLU) and azelastine HCl (AZL) in the presence of their pharmaceutical dosage form additives (phenylethyl alcohol (PEA) and benzalkonium chloride (BNZ)). Methods: The separation was performed on a C18 column using (o/w) microemulsion as a mobile phase which contains 0.2 M sodium dodecyl sulphate (SDS) as surfactant, 10% butanol as cosurfactant, 1% n-octanol as internal phase and 0.3% triethylamine (TEA) adjusted at pH 6 by 0.02 M phosphoric acid; with UV detection at 220 nm and programmed with flow rate of 1 mL/min. Results: The validation characteristics e.g. linearity, lower limit of quantification (LOQ), lower limit of detection (LOD), accuracy, precision, robustness and specificity were investigated. The proposed method showed linearity over the concentration range of (0.5-25 µg/mL) and (0.1-25 µg/mL) for FLU and AZL, respectively. Besides that, the method was adopted in a short chromatographic run with satisfactory resolution factors of (2.39, 3.78 and 6.74 between PEA/FLU, FLU/AZL and AZL/BNZ), respectively. The performed method was efficiently applied to pharmaceutical nasal spray with (mean recoveries ± SD) (99.80 ± 0.97) and (100.26 ± 0.96) for FLU and AZL, respectively. Conclusion: The suggested method was based on simultaneous determination of FLU and AZL in the presence of PEA and BNZ in pure form, laboratory synthetic mixture and its combined pharmaceutical dosage form using green MELC technique with UV detection. The proposed method appeared to be superior to the reported ones of being more sensitive and specific, as well as the separation was achieved with good performance in a relatively short analysis time (less than 7.5 min). Highly acceptable values of LOD and % RSD make this method superior to be used in quality control laboratories with of HPLC technique.

scholarly journals Graphite Studded with Facile-Synthesized Cu2O Nanoparticle-Based Cubes as a Novel Electrochemical Sensor for Highly Sensitive Voltametric Determination of Mebeverine Hydrochloride

Chemosensors ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 35
Author(s):  
Ahmed H. Naggar ◽  
Ahmed Kotb ◽  
Ahmed A. Gahlan ◽  
Mahmoud H. Mahross ◽  
Abd El-Aziz Y. El-Sayed ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Lower Limit ◽  
Electrochemical Behavior ◽  
Cuprous Oxide ◽  
Density Functional ◽  
Limit Of Detection ◽  
Biological Fluids ◽  
Chemical Reduction ◽  
Anodic Stripping Voltammetry ◽  
Mebeverine Hydrochloride

Herein, a feasible chemical reduction method followed by intensive mixing was applied for the preparation of an attractive material based on graphite studded with cuprous oxide nanoparticle-based cubes (Cu2ONPs–C@G). Transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV) were utilized for characterization. Cuprous oxide nanoparticles (Cu2ONPs), with a diameter range mainly distributed from 4 to 20 nm, aggregate to form microcubes (Cu2ONPs–C) with an average diameter of about 367 nm. Paste electrode was prepared using Cu2ONPs–C@G (Cu2ONPs–C@G/PE) for voltametric quantification of the musculotropic antispasmodic drug: mebeverine hydrochloride (MEB). The electrochemical behavior of MEB was studied using CV, and the optimum analytical parameters were investigated using square wave adsorptive anodic stripping voltammetry (SWAdASV). Moreover, density functional theory (DFT) was used to emphasize the ability of MEB to form a complex with Cu2+, confirming the suggested electrochemical behavior of MEB at Cu2ONPs–C@G/PE. With good stability and high reproducibility, SWAdASV of Cu2ONPs–C@G/PE shows successful quantification of MEB over the concentration range of 5.00 × 10−11–1.10 × 10−9 M with lower limit of detection (LOD) and lower limit of quantification (LOQ) values of 2.41 × 10−11 M and 8.05 × 10−11 M, respectively. Finally, accurate quantification of MEB in dosage forms (tablets) and biological fluids (spiked human urine and plasma samples) was achieved using Cu2ONPs-C@G/PE.

scholarly journals Application of an LC–MS/MS Method for the Simultaneous Quantification of Homovanillic Acid and Vanillylmandelic Acid for the Diagnosis and Follow-Up of Neuroblastoma in 357 Patients

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3470
Author(s):  
Narae Hwang ◽  
Eunbin Chong ◽  
Hyeonju Oh ◽  
Hee Won Cho ◽  
Ji Won Lee ◽  
...  
Keyword(s):  
Lower Limit ◽  
Large Scale ◽  
Homovanillic Acid ◽  
Limit Of Detection ◽  
Method Comparison ◽  
Vanillylmandelic Acid ◽  
Limit Of Quantification ◽  
Spot Urine ◽  
Minimal Sample ◽  
Clinical Biomarkers

Homovanillic acid (HVA) and vanillylmandelic acid (VMA) are end-stage metabolites of catecholamine and are clinical biomarkers for the diagnosis of neuroblastoma. For the first time in Korea, we implemented and validated a liquid chromatography tandem mass spectrometry (LC–MS/MS) assay to measure urinary concentrations of HVA and VMA according to Clinical and Laboratory Standards Institute guidelines. Our LC–MS/MS assay with minimal sample preparation was validated for linearity, lower limit of detection (LOD), lower limit of quantification (LLOQ), precision, accuracy, extraction recovery, carryover, matrix effect, and method comparison. A total of 1209 measurements was performed to measure HVA and VMA in spot urine between October 2019 and September 2020. The relationship between the two urinary markers, HVA and VMA, was analyzed and exhibited high agreement (89.1% agreement, kappa’s k = 0.6) and a strong correlation (Pearson’s r = 0.73). To our knowledge, this is the first study to utilize LC–MS/MS for simultaneous quantitation of spot urinary HVA and VMA and analyze the clinical application of both markers on a large scale for neuroblastoma patients.

scholarly journals Development and Application of an UHPLC-MS/MS Method for Comparative Pharmacokinetic Study of Eight Major Bioactive Components from Yin Chen Hao Tang in Normal and Acute Liver Injured Rats

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Yun Wang ◽  
Xinrui Xing ◽  
Yan Cao ◽  
Liang Zhao ◽  
Sen Sun ◽  
...  
Keyword(s):  
Lower Limit ◽  
Limit Of Detection ◽  
Injury Model ◽  
Relative Standard ◽  
Limit Of Quantitation ◽  
Liquid Chromatography Tandem Mass ◽  
Bioactive Ingredients ◽  
Aloe Emodin ◽  
Plasma Pharmacokinetics ◽  
Ultrahigh Performance Liquid Chromatography

Yin Chen Hao Tang (YCHT) is one of the most famous hepatoprotective herbal formulas in China, but its pharmacokinetic investigation in model rats has been rarely conducted. In this study, the hepatic injury model was caused by intraperitoneal injections of carbon tetrachloride (CCl4), and YCHT was orally administered to the model and normal rats. An ultrahigh performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method was established to analyze the plasma pharmacokinetics of eight major bioactive ingredients from YCHT in both the normal and liver injured rats. The calibration curves presented good linearity (r > 0.9981) in the concentration range. The relative standard deviation (RSD%) of inter- and intraday precision was within 9.55%, and the accuracy (RE%) ranged from -10.72% to 2.46%. The extraction recovery, matrix effect, and stability were demonstrated to be within acceptable ranges. The lower limit of detection (LLOD) and lower limit of quantitation (LLOQ) were around 0.1 ng/mL and 0.5 ng/mL, respectively, which were much lower than those in other related researches. Results reveal that there are significant differences in the pharmacokinetics of scoparone, geniposide, rhein, aloe-emodin, physcion, and chrysophanol in hepatic injured rats as compared to those in control except for scopoletin and emodin. Our experimental results provide a meaningful reference for the clinical dosage of YCHT in treating liver disorders, and the improvement of LLOD and LLOQ can also broaden the range of our method’s application, which is very suitable for quantitating these eight compounds with low levels.

Digital Droplet PCR (ddPCR) for Detection and Quantitation of Hepatitis Delt Virus

2021 ◽  
Author(s):  
Ling Xu ◽  
Xiangying Zhang ◽  
Yaling Cao ◽  
Zihao Fan ◽  
Yuan Tian ◽  
...  
Keyword(s):  
Liver Failure ◽  
Lower Limit ◽  
Limit Of Detection ◽  
Quantitative Detection ◽  
Rt Pcr ◽  
Rna Detection ◽  
Detection Rates ◽  
Digital Droplet Pcr ◽  
Droplet Pcr ◽  
Hdv Infection

Abstract Background & Aims The prevalence of hepatitis delt virus (HDV) far exceeds our expected level, there remains a lack of reliable quantitative assays for HDV RNA detection. We sought to develop a new method based on digital droplet PCR (ddPCR) for HDV RNA quantitative detection. Methods With plasmid (pMD19T) containing HDV full-genome, we determined the method for ddPCR-based HDV RNA quantification. To compare various assays for HDV detection, 30 cases diagnosed hepatitis D and 14 controls were examined by ELISA, RT-PCR and ddPCR. 728 HBV-related patients including 182 chronic hepatitis B (CHB), 182 liver cirrhosis (LC), 182 hepatocellular carcinoma (HCC) and 182 liver failure (LF) were screened for HDV infection. Results The limit of detection of ddPCR for HDV is significantly low, which lower limit of detection (LLoD) and lower limit of quantitation (LLoQ) to be 5.51 copies/reaction (95% CI: 1.15–6.4*105) and 0.18 copies/reaction (95% CI: 0.0012151- 0.76436), respectively. Among the 44 samples, ELISA detected 30 cases positive for anti-HDV, ddPCR reported 24 samples and RT-PCR reported 10 samples positive for HDV RNA. Moreover, the positive rates of anti-HDV IgG were 1.1%, 3.3%, 2.7% and 7.1% in patients with CHB, LC, HCC, and LF; the detection rates of RT-PCR in HDV RNA were 0%, 16.67%, 15.4% and 20%, however, the detection rates of ddPCR were 0%, 33.33%, 30.77% and 60%. Conclusion We establish a high sensitivity and high specificity quantitative HDV RNA detection method based on ddPCR compared to RT-PCR. HBV-related end-stage liver disease, especially liver failure, are associated with a remarkably high rate of HDV infection.

Determination of Sulfonylurea Herbicides in Grains by Capillary Electrophoresis

1995 ◽  
Vol 78 (4) ◽  
pp. 1091-1096 ◽  
Author(s):  
Alexander J Krynitsky ◽  
Douglas M Swtneford
Keyword(s):  
Capillary Electrophoresis ◽  
Lower Limit ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Residue Analysis ◽  
High Sensitivity ◽  
Sulfonylurea Herbicides ◽  
Optical Cell ◽  
Liquid Chromatographic ◽  
Tribenuron Methyl

Abstract A capillary electrophoresis (CE) method was developed to separate and determine residues of 5 sulfonylurea herbicides in grains (wheat, barley, and corn). This work demonstrated the practicality of using CE for residue analysis of sulfonylureas. The method yielded good recoveries and adequate sensitivities at tolerance levels (0.05–0.1 ppm). The compounds investigated were metsulfuron methyl (Ally), thifensulfuron methyl (Harmony), chlorsulfuron (Glean), rimsulfuron (DPX-E9636), and tribenuron methyl (Express). Acetonitrile extracts of grain samples were partitioned with hexane and then cleaned up with cation exchange solid-phase extraction cartridges. Quantitation was performed by micellar electrokinetic capillary chromatography using a high-sensitivity optical cell. Average recoveries at the 0.05 ppm level ranged from 72.9 to 118.5%. The lower limit of detection was approximately 0.02 ppm, except for rimsulfuron and tribenuron methyl, for which the lower limit of detection was 0.035 ppm. The method was less complicated and showed better sensitivity than current single-analyte liquid chromatographic enforcement methods.

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