Detection limit

About: Detection limit is a research topic. Over the lifetime, 34379 publications have been published within this topic receiving 644817 citations. The topic is also known as: limit of detection & lower detection limit.

Synthesis of silica gel immobilized thiourea and its application to the on-line preconcentration and separation of silver, gold and palladium

Abstract: A new silica gel based chelating sorbent with thiourea as a functional group was used for the flow injection (FI) on-line preconcentration and separation of trace levels of silver, gold and palladium. Its sorption characteristics were evaluated by FI-FAAS. The selected metal ions were adsorbed on a column packed with thiourea modified silica gel (TuSG) with a sampling flow rate of 5.0 ml min1, eluted with 5% thiourea with a flow rate of 2.5 ml min1 and determined by FAAS. Common co-existing ions did not interfere with the preconcentration and determination. The detection limits, defined as three times of the standard deviation of the blank (3σ), of Ag, Au and Pd are 1.3, 14 and 21 ng ml1, respectively, with a 1 min sample loading time. The RSD is not more than 3.0% for 0.040 µg ml1 of Ag, 0.20 µg ml1 of Au and 0.30 µg ml1 of Pd. With 40 min of the sample loading time, 1.0 ng ml1 of Ag, 5.0 ng ml1 of Au and 7.5 ng ml1 of Pd were successfully preconcentrated. The total dynamic capacity of TuSG was 24.5, 50.9 and 30.3 mg g1 for Ag, Au and Pd, respectively. The sorbent exhibited excellent stability. Its sorption properties did not change after 1000 cycles of use. The selected metals in a secondary nickel alloy, an anode slime, an electrolytic solution and three national certified ore samples were determined satisfactorily using the proposed method.

Quantitative Determination of Sarcosine and Related Compounds in Urinary Samples by Liquid Chromatography with Tandem Mass Spectrometry

Abstract: The current prostate cancer (PCa) diagnosis, based on the blood prostate-specific antigen (PSA) level measurement, is not a precise science. The widely used PSA biomarker for PCa has poor sensitivity and specificity and often leads to false-negative and false-positive test results. Recently, sarcosine, proline, kynurenine, uracil, and glycerol 3-phosphate were found in higher concentrations in metastatic prostate cancer urine samples. By measuring all five of these metabolites, doctors may be better able to diagnose prostate cancer with high accuracy. However, there is no method reported for simultaneous detection of these compounds in urine samples. In this study, a novel method was developed to separate and quantify six urinary metabolites including creatinine in urine samples by using liquid chromatography/tandem mass spectrometry. Chromatographic separations of the analytes were carried out using a phenyl-hexyl column with 0.1% formic acid in water and acetonitrile, respectively, under a gradient program. The six metabolites were detected in the multiple reaction monitoring modes with the ESI-positive mode. The linear range of the analytes was from 0.003 to 40 μmol/L. The limit of detection was from 0.05 to 4 nmol/L, and the limit of quantification ranged from 3 to 20 nmol/L. The factors affecting the separation and quantification of the six metabolites, such as mobile-phase and MS conditions, were also investigated. The technique developed in this study is simple, fast, sensitive, and selective. It can be used for quantifying these six metabolites in urine samples for potential early cancer screening.

Elemental Analyses Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) of Geological Samples Fused with Li2B4O7 and Calibrated Without Matrix-Matched Standards

Abstract: Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used as a complementary technique to X-ray fluorescence (XRF), for multi-element analysis of geological samples fused with lithium-tetraborate Li2B4O7). Different calibration strategies using external non-matrix matched reference materials were investigated. Various internal standards were tested, including the use of Li from the flux, and the use of the naturally occurring internal standards, Si or Ca. The use of a naturally occurring standard is not as efficient as this required a prior analysis of the samples using XRF. The obtained values for the analysis of geological reference materials were compared with consensus literature values, and satisfactory agreement was found. Laser pits, which were formed, had a diameter of 80 μm and 3–5 replicates on each fused disc were measured. The reproducibility of the method was better than 10% for concentrations above 1 μg/g and better than 15% for lower concentrations. The use of Li as the internal standard offers the possibility of multi-element determinations in geological samples, which have an unknown composition when the laser ablation analysis is carried out. However, using the calculated stoichiometric composition of the lithium-tetraborate for the calculation of the Li concentration leads to a constant deviation from the recommended values. Therefore, it was necessary to determine the Li concentration within each sample batch using at least one lithium tetraborate fused geological reference material. This resulting Li concentration in the beads was then used for all subsequent samples in a run. Limits of detection, reproducibility, deviation from reference values indicate the potential of LA-ICP-MS for such bulk analysis without matrix matched calibration standards.

Highly Selective and Sensitive 1-Amino BODIPY-Based Red Fluorescent Probe for Thiophenols with High Off-to-On Contrast Ratio

Abstract: A highly selective and sensitive turn-on red fluorescent 1-amino BODIPY-based probe (where BODIPY denotes indole-based boron-dipyrromethene) with high off-to-on contrast ratio has been developed. The probe displayed selective response to thiophenols over aliphatic thiols. Probe 1 is promising for the quantitative detection of thiophenol with a linear response from 6 × 10–6 M to 1 × 10–4 M, and the detection limit for thiophenol (PhSH) reaches 4 × 10–6 M measured in acetonitrile/PBS buffer. The detection limit could be improved to 37 nM (detection limit to 4 ppb) in water when 1% Tween 20 was used to assist the dissolvation of probe 1 in water. Probe 1 is also a useful fluorescent probe for detecting thiophenols in living cells in red emission, which may greatly improve the detectable sensitivity.