These results could be attributed to the analytes physical–chemical properties influencing the extraction efficiency of the CPE technique, and thus the analytical responses [26]. At the working pH 3 TC and ABC were in their molecular form, while EFV and NFV were in their ionic forms. They show different water solubility behavior (Table 1) coherent with their analytical responses. In this sense, it is expected to obtain the lowest responses for 3 TC and ABC since they are the most polar analytes and the surfactant is no-ionic, limiting thus the affinity between them and the micelles. The performance of EFV could be attributed to the fact that at the lowest surfactant concentration assayed, the extraction efficiency was the maximum. Higher concentration led to higher surfactant reach phase volume; therefore, concentration of the extracted analytes was lower due to a dilution effect. In this sense, NFV reported the highest analytical response at intermediate concentration, falling for dilution into the resulting coacervate phase when higher surfactant was used. The most polar analytes contain higher number of polar atoms into their structure. This leads to higher molecular effective radio due to the solvatation, reducing their interaction with micelles. Therefore, 3 TC and ABC require higher surfactant concentration to achieve a successful extraction and analytical response.
Based on these experiment results, 5% (w/v) Triton X-114 was adopted as working condition considering it as the best compromise concentration that lead to successful analytical response for the studied ARV. This fact is relevant for the development of an analytical methodology for a multi-component analysis.
3.3. Effect of pH
To the knowledge of the authors, CPE was not previously applied for ARV extraction in any matrix; therefore there was no evidence of which could be the pH effect on analytical signal for this methodology. Analytical responses would be conditioned by CPE and instrumental efficiency. CPE is strongly conditioned by physicochemical properties of the analytes, sample matrix, as well as CPE particularities (surfactant type and concentration, matrix modifiers, etc). On the other hand, instrumental efficiency is also conditioned by sample matrix characteristic and analytes physicochemical properties, additionally to the particularities of the detection system. It is well know that plasma matrix contains dissolved proteins (6–8%) (i.e. albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na+, Ca2+, Mg2+, HCO3−, Cl−, etc.), hormones and carbon dioxide [27] and [28] which could affect the extraction efficiency of the CPE technique [29]. Considering that the studied ARV are ionizable species according to their pKa (Table 1), it was expected that extraction pH could affect their analytical responses as follows: the extraction pH may condition the ionizable equilibrium of the ARV, and thus it molecular form, which affect their affinity for micelles, and consequently their extraction efficiency. On the other hand, it is important to highlight that due to the nonionic character of the surfactant, it is not expected to see a pH effect on micelles [16] and [17]. Considering this information, the effect of pH on the analytical response of ARV was analyzed. As shown in Fig. 3, at pH 2.5 the lowest relative responses were obtained for all ARV (
ผลลัพธ์เหล่านี้อาจเกิดจากคุณสมบัติทางกายภาพ – เคมี analytes มีอิทธิพลต่อประสิทธิภาพการสกัดของเทคนิค CPE ตอบวิเคราะห์ [26] ที่ pH ทำ 3 TC และ ABC ได้ในแบบฟอร์มของโมเลกุล ขณะ EFV และ NFV ในฟอร์มของ ionic พวกเขาแสดงพฤติกรรมการละลายน้ำต่างกัน (ตารางที่ 1) กับการตอบรับวิเคราะห์ ในความรู้สึกนี้ มันคาดว่าจะได้รับการตอบสนองต่ำ 3 TC และ ABC ตั้งแต่จะ analytes สุดขั้ว และ surfactant เป็น no-ionic จำกัดความสัมพันธ์ระหว่างพวกเขาและ micelles นี้จึง อาจเกิดจากประสิทธิภาพของ EFV ในความเป็นจริงที่ว่า ที่สุด surfactant ความเข้มข้น assayed ประสิทธิภาพการสกัดสูงสุด ความเข้มข้นสูงให้ surfactant สูงถึงระยะเสียง ดังนั้น ความเข้มข้นของ analytes แยกเป็นต่ำเนื่องจากผลเจือจาง ในนี้รู้สึก NFV รายงานตอบวิเคราะห์สูงสุดที่ความเข้มข้นปานกลาง ตกสำหรับเจือจางในระยะ coacervate ผลลัพธ์เมื่อใช้ surfactant ที่สูงกว่า Analytes สุดขั้วประกอบด้วยจำนวนอะตอมขั้วสูงเป็นโครงสร้าง นี้นำไปสู่สูงวิทยุมีประสิทธิภาพโมเลกุลเนื่องจาก solvatation ลดการโต้ตอบกับ micelles ดังนั้น 3 TC และ ABC ต้อง surfactant ความเข้มข้นสูงเพื่อให้ประสบความสำเร็จในการสกัดและวิเคราะห์ตอบสนองBased on these experiment results, 5% (w/v) Triton X-114 was adopted as working condition considering it as the best compromise concentration that lead to successful analytical response for the studied ARV. This fact is relevant for the development of an analytical methodology for a multi-component analysis.3.3. Effect of pHTo the knowledge of the authors, CPE was not previously applied for ARV extraction in any matrix; therefore there was no evidence of which could be the pH effect on analytical signal for this methodology. Analytical responses would be conditioned by CPE and instrumental efficiency. CPE is strongly conditioned by physicochemical properties of the analytes, sample matrix, as well as CPE particularities (surfactant type and concentration, matrix modifiers, etc). On the other hand, instrumental efficiency is also conditioned by sample matrix characteristic and analytes physicochemical properties, additionally to the particularities of the detection system. It is well know that plasma matrix contains dissolved proteins (6–8%) (i.e. albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na+, Ca2+, Mg2+, HCO3−, Cl−, etc.), hormones and carbon dioxide [27] and [28] which could affect the extraction efficiency of the CPE technique [29]. Considering that the studied ARV are ionizable species according to their pKa (Table 1), it was expected that extraction pH could affect their analytical responses as follows: the extraction pH may condition the ionizable equilibrium of the ARV, and thus it molecular form, which affect their affinity for micelles, and consequently their extraction efficiency. On the other hand, it is important to highlight that due to the nonionic character of the surfactant, it is not expected to see a pH effect on micelles [16] and [17]. Considering this information, the effect of pH on the analytical response of ARV was analyzed. As shown in Fig. 3, at pH 2.5 the lowest relative responses were obtained for all ARV (<50%). At this pH the analytes were in the molecular form, thus it was expected to have the highest affinity for nonionic micelles.
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