The reliable quantification of carbidopa in biological samples at low concentrations is challenging because of the polar and highly unstable nature of the compound. In this paper, LC–MS/MS methods are described for the determination of carbidopa in 50 μL of human plasma and 25 μL of human urine in the concentration ranges 1–1,000 ng/mL and 100–50,000 ng/mL, respectively. After a simple protein precipitation (plasma) or dilution (urine) step, carbidopa is derivatized at its hydrazine moiety by reaction for one hour with 2,4-pentanedione under acidic conditions and at 40 °C. The product is a relatively non-polar molecule that is suitable for reversed-phase liquid chromatography (3.5 min run time) with detection by tandem mass spectrometry with electrospray ionization. A stable-isotope labeled internal standard is used for response normalization. Precision, accuracy and selectivity of the methods meet the criteria of international guidelines for bioanalytical method validation. Acidification of urine to pH 1.5 and the addition of two anti-oxidants (5 mg/mL sodium metabisulfite and 1 mg/mL butylated hydroxytoluene) to plasma, in combination with sampling and analysis on ice and under yellow light, ensure sufficient stability of carbidopa. The methods were successfully used to determine plasma pharmacokinetics and urinary excretion of carbidopa in healthy volunteers after a single 37.5 mg oral dose.

由于该化合物的极性和高度不稳定的特性，因此在低浓度的生物样品中对卡比多巴进行可靠的定量分析具有挑战性。本文介绍了LC-MS / MS方法，分别用于测定50μL血浆和25μL尿液中卡比多巴的浓度，浓度范围为1–1,000 ng / mL和100–50,000 ng / mL。在简单的蛋白质沉淀（血浆）或稀释（尿液）步骤之后，卡比多巴通过在酸性条件下和40°C下与2,4-戊二酮反应1小时，使其肼部分衍生化。该产物是相对非极性的分子，适用于反相液相色谱（运行时间3.5分钟），可通过串联质谱与电喷雾电离进行检测。稳定同位素标记的内标用于响应归一化。这些方法的精密度，准确性和选择性符合生物分析方法验证的国际准则的标准。将尿液酸化至pH 1.5，并在血浆中添加两种抗氧化剂（5 mg / mL偏亚硫酸氢钠和1 mg / mL丁基羟基甲苯），并在冰上和在黄光下进行采样和分析，确保卡比多巴具有足够的稳定性。单次口服37.5 mg后，该方法已成功用于确定健康志愿者中卡比多巴的血浆药代动力学和尿排泄。与冰和黄光下的采样和分析相结合，可确保卡比多巴具有足够的稳定性。单次口服37.5 mg后，这些方法已成功用于确定健康志愿者中卡比多巴的血浆药代动力学和尿排泄。与冰和黄光下的采样和分析相结合，可确保卡比多巴具有足够的稳定性。单次口服37.5 mg后，这些方法已成功用于确定健康志愿者中卡比多巴的血浆药代动力学和尿排泄。