Fiber optic-based radiochromic dosimetry
Sam Beddar, Luc Beaulieu in Scintillation Dosimetry, 2018
One generally accepted definition of detection limit in analytical chemistry is as minimum concentration or mass of analyte that can be detected at a known confidence level, and is typically taken as signal from blank plus three times standard deviation (1σ) of a blank (Skoog et al. 1998). If the signal is greater than this value, then one can say with confidence that the analyte is present. If the signal is below this value, then analyte is considered undetected. As discussed in Section 16.2, the increase in netOD of radiochromic material is due to increase in the number of conjugated polymer backbones, which can be considered similar to a chemical analyte that has specific absorbance properties. Intensity of transmitted photons through an unirradiated film can therefore be used as the blank, and ideally this value is as close to the
Development and Evaluation
Joseph Chamberlain in The Analysis of Drugs in Biological Fluids, 2018
Because most drugs developed today are administered in very small doses, the analyst is continually being challenged to devise methods of detection and measurement of very small concentrations of drug. As explained in Chapter 1, for pharmacokinetic studies, it is at the low level of drug that the quantitation becomes extremely important. Thus the limit of detection obtained using a particular method is of prime importance in such studies. Many reports use the term sensitivity for this parameter; however, sensitivity is also used to describe the slope of a concentration-response line (i.e., a measure of how sensitive the end point is to the change in concentration). Thus the author recommends that the term limit of detection is more appropriate in this context. Of all the parameters used to characterize a method, it is probably the one that has the most varied treatment from analysts, so that a statement that “the sensitivity is x ng ml−1,” should only be accepted in the context of the definition given by the author of that particular paper or its description.
Inherited Abnormalities in Thyroid Hormone Transport Proteins
Geraldo Medeiros-Neto, John Bruton Stanbury in Inherited Disorders of the Thyroid System, 2019
Refetoff2 defines complete TBG deficiency when the serum concentration of TBG is less than 0.5 μg/dl. This is the current limit of detection by the most sensitive assays.15 It affects individuals from all races and ethnic backgrounds and the incidence is around 1 to 15,000 newborn males. Heterozygous females (two X chromosomes) usually express the defect partially by having approximately half the normal concentration of TBG (Figure 1). None of the subjects with TBG-CD belonging to 16 unrelated families had detectable TBG in serum.2
Peripheral clock system circadian abnormalities in Cushing’s disease
Published in Chronobiology International, 2020
Vinicius Reis Soares, Clarissa Silva Martins, Edson Zangiacomi Martinez, Leonardo Domingues Araujo, Silvia Liliana Ruiz Roa, Lucas Ravagnani Silva, Ayrton Custodio Moreira, Margaret De Castro
We studied 13 healthy women and 12 CD patients. Patients were investigated between 2015 and 2017 in the Division of Endocrinology at HCFMRP-USP, one of the referral services for Cushing’s syndrome in Brazil. The diagnosis of Cushing’s syndrome was based on clinical signs and symptoms and subsequent confirmation of hypercortisolism by biochemical testing, according to international established criteria (Nieman et al. 2008). Briefly, biochemical diagnosis was based on increased levels of urinary-free cortisol and/or late-night salivary cortisol (LNSC), and non-suppression of plasma or salivary cortisol after low-dose (1 mg overnight) dexamethasone suppression test (LDDST). To diagnose endogenous hypercortisolism, we used as a cutoff for LNSC values above 350 ng/dL (or 9.8 nmol/L) and salivary cortisol levels after LDDST above 150 ng/dl (or 4.2 nmol/L) (Elias et al. 2014). The criteria for a normal salivary cortisol circadian rhythm was late-night cortisol (2300 h) lower than 83.5% of morning basal cortisol (0900 h) and lower than 350ng/dl (9.65 nmol/l) (Castro et al. 1999). Values below the limit of detection of the method, for statistical analysis, were substituted by the limit of detection.
Development and validation of HPLC method for simultaneous determination of Leflunomide and folic acid in the nanoparticulate system by reversed-phase HPLC
Published in Drug Development and Industrial Pharmacy, 2023
Bazla Siddiqui, Haroon Ahmed, Ihsan-ul- Haq, Asim.ur. Rehman, Naveed Ahmed
A facile reversed phase HPLC technique was developed to simultaneously detect and analyze both LEF and FA from the nanocarriers for the first time. In addition to the novelty of method to simultaneously detect both components in less retention time, the method is also simple, fast, robust, sensitive, precise, and produced reproducible results in accordance with the ICH guidelines. The response of the detector was found to be linear for both of the components at a wider concentration range. Moreover, the lower value of limit of detection enabled this technique to analyze the samples at relatively lower concentrations. No interference of the formulation matrix was observed, and method was successfully employed for determination of entrapment efficiency and loading capacity. Another advantage of the proposed developed method was the utilization of same mobile phase for determination of both components from the nanocarriers. In comparison to the previously developed method of Leflunomide detection, the method produced precise results at a relatively shorter time period. Hence, the method can be recommended for evaluation of further parameters of the prepared nanocarriers, e.g. dissolution studies, release studies. In future, the method can also be utilized for evaluating the concentration of both agents in serum and plasma for in vivo drug analysis and for monitoring pharmacokinetic drug profile.
Evaluation of association between parameters related to penetration into cerebrospinal fluid and the microbiological efficacy of vancomycin in patients with bacterial meningitis
Published in Journal of Chemotherapy, 2022
Masayuki Ishikawa, Masashi Uchida, Shingo Yamazaki, Yuki Shiko, Yohei Kawasaki, Takaaki Suzuki, Yasuo Iwadate, Itsuko Ishii
VMser and VMCSF were measured by a chemiluminescence immunoassay with an ARCHITECT® analyzer (Abbott Laboratories, Irving, TX). The method was fully validated over a concentration range of 3.0–100.0 μg/mL. The lower limit of quantification and the lower limit of detection were 3.0 μg/mL and 0.24 μg/mL, respectively. SA concentrations were measured by the bromocresol green or bromocresol purple method. The SA value measured by the bromocresol green method is known to be about 0.3 mg/dL higher than that measured by the bromocresol purple method. Therefore, if the SA was measured by the bromocresol green method, we subtracted 0.3 mg/dL from the measured value based on the guidelines [14]. CSF proteins and CSF glucose concentrations were measured by the pyrogallol red and hexokinase methods, respectively. CSF cell counts were performed manually. The MIC for bacteria was determined via the broth microdilution method of the Clinical and Laboratory Standards Institute. Creatinine clearance was calculated by the Cockcroft–Gault formula, using actual body weight [15].
Related Knowledge Centers
- Sensitivity & Specificity
- Type I & Type II Errors
- Statistical Significance
- Analytical Chemistry
- Sensitivity & Specificity
- Blank Value
- Standard Deviation
- Accuracy & Precision
- Type I & Type II Errors
- False Positives & False Negatives
- Matrix
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