Yen-Hsia Wen

Derivatization-GAS Chromatographic Determination of Perindopril

Abstract A capillary gas chromatographic method is described for the determination of perindopril, an anti-hypertensive agent. The method is based on the derivatization of perindopril with pentafluorobenzyl bromide in acetone, using potassium carbonate as a base catalyst. Under a mild condition, the highly polar and nonvolatile perindopril was derivatized into a derivative with suitable chromatographic properties. The resulting derivative was separated on an SE-54 capillary column and detected by a flame-ionization detector. Several parameters affecting the derivatization of perindopril were investigated. The linear range of the method for the determination of perindoplil was over 20–300 nmol. The detection limit (signal to noise ratio of 5) of perindopril in 0.2 mL acetone solution was about 3 nmol. Application of the method to the analysis of perindopril in tablets proved to be feasible.

Chiral separation of acebutolol by derivatization and high-performance liquid chromatography

Abstract A simple and specific high performance liquid chromatographic (HPLC) method is described for the determination of R-(+)- and S-(−)acebutolols. The method is based on the derivatization of the hydroxyl and amino functions of acebutolol with N-benzyloxycarbonyl-L-phenyl-alanine and acetic anhydride, respectively. The resulting derivatives were separated on a reversed phase C-18 column and monitored with a UV detector, leading to a base line resolution of the diastereomeric derivatives of S-(−) and R-(+) acebutolols.

A Bayesian Approach to Identifying New Risk Factors for Dementia: A Nationwide Population-Based Study.

AbstractDementia is one of the most disabling and burdensome health conditions worldwide. In this study, we identified new potential risk factors for dementia from nationwide longitudinal population-based data by using Bayesian statistics.We first tested the consistency of the results obtained using Bayesian statistics with those obtained using classical frequentist probability for 4 recognized risk factors for dementia, namely severe head injury, depression, diabetes mellitus, and vascular diseases. Then, we used Bayesian statistics to verify 2 new potential risk factors for dementia, namely hearing loss and senile cataract, determined from the Taiwans National Health Insurance Research Database.We included a total of 6546 (6.0%) patients diagnosed with dementia. We observed older age, female sex, and lower income as independent risk factors for dementia. Moreover, we verified the 4 recognized risk factors for dementia in the older Taiwanese population; their odds ratios (ORs) ranged from 3.469 to 1.207. Furthermore, we observed that hearing loss (OR = 1.577) and senile cataract (OR = 1.549) were associated with an increased risk of dementia.We found that the results obtained using Bayesian statistics for assessing risk factors for dementia, such as head injury, depression, DM, and vascular diseases, were consistent with those obtained using classical frequentist probability. Moreover, hearing loss and senile cataract were found to be potential risk factors for dementia in the older Taiwanese population. Bayesian statistics could help clinicians explore other potential risk factors for dementia and for developing appropriate treatment strategies for these patients.

Electron-Capture Gas Chromatographic Determination of Alkyl Thiophosphates as Pentafluorobenzyl Derivatives

Abstract An improved and sensitive gas chromatographic method has been established for the determination of four dialkyl thiophosphates including dimethyl phosphorothioate, diethyl phosphorothioate, dimethyl phosphorodithioate and diethyl phosphorodithioate. The method is based on the derivatization of the thiophosphates with pentafluorobenzyl bromide, using hexadecyltrimethylammonium bromide as a phase transfer catalyst. The resulting derivatives were separated on an SE-54 capillary column and detected by an electron-capture detector. Several parameters affecting the derivatization of the related thiophosphates were investigated. Determinations of the thiophosphates were attainable at pmol levels. The detection limits (signal to noise ratio of 5) of dimethyl phosphorothioate, diethyl phosphorothioate, dimethyl phosphorodithioate and diethyl phosphorodithioate in aqueous sample were at about 8.3, 6.0, 5.7 and 5.6 nM, respectively. Application of the method to the analysis of the thiophosphates spiked in p...

Antipsychotic medications and dental caries in newly diagnosed schizophrenia: A nationwide cohort study.

We investigated the association between antipsychotic medications and the risk of dental caries in patients with schizophrenia. We enroled a nationwide cohort of patients with newly diagnosed schizophrenia within 1 year of dental caries development. Exposure to antipsychotics and other medications was categorised according to their type and duration, and the association between exposure and dental caries was assessed through logistic regressions. Of the 3610 patients with newly diagnosed schizophrenia, 2149 (59.5%) exhibited an incidence of treated dental caries. Logistic regression analysis identified a younger age, female sex, high income, a 2-year history of dental caries, and exposure to first-generation antipsychotics, and antihypertensives as independent risk factors for treated dental caries in patients with schizophrenia. Hyposalivation, the adverse effect of first-generation antipsychotics and antihypertensives, was associated with an increased risk of treated dental caries. However, hypersalivation from first-generation antipsychotics for dental caries was associated with a protective factor. These findings suggest that clinicians should pay attention to the aforementioned risk factors for dental caries in patients with schizophrenia, particularly while prescribing first-generation antipsychotics and antihypertensives to such patients.

Determination of Methanol by 4-[N-Methyl, N-(1-naphthylmethyl)]-amino-4-oxo-butanoic Acid in Presence of 4-Dimethylaminopyridine and 1-Ethyl-3-(3-dimethylaminopropyl) Carbodiimide Hydrochloride as Catalysts

Abstract High performance liquid chromatography (HPLC) with chemically removable derivatizing reagents for the analysis of methanol has been developed. Methanol was derivatized with 4-[N-methyl, N-(1-naphthylmethyl)]-amino-4-oxo-butanoic acid (NAOB), using 4-dimethylaminopyridine (DMAP) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) as activators. NAOB and the activators are chemically removable and can be removed by aqueous base and acid treatment after derivatization to minimize reagent interference in chromatography. The method can simultaneously determine methanol, ethanol and 1-propanol. The proposed HPLC method was validated for linearity, specificity, accuracy and reproducibility. The method was applied to the analysis of methanol spiked in Ipecac fluid extract with a satisfactory recovery (>95%).

Trace analysis of acetaldehyde as fluorogenic derivative by high performance liquid chromatography.

A sensitive method is described for the determination of acetaldehyde as a fluorogenic derivative of decahydroacridin-1,8-dione by high performance liquid chromatography. The analytical derivatization is based on the reaction of acetaldehyde in an acidic aqueous system with 1,3-cyclohexanedione and ammonium acetate. The resulting derivative was separated by a reversed-phase C-18 column and monitored with a fluorescent detector (lambda ex, 375nm; lambda em, 512nm). Several parameters affecting the derivatization of acetaldehyde were studied. The linear range of the method for the quantitation of acetaldehyde was between 20 and 800 pmol in aqueous sample (0.5 mL). Application of the method to the analysis of acetaldehyde in plasma was performed.