Evaluation of the pH, titratable acidity and viscosity of various brands of syrups sampled from various pharmacy stores in Benin

Background: For so long now, medicated syrups have been used in paediatric practice for the treatment of disease conditions, as palliatives and even as food supplements / haematinics. Pharmaceutical firms sweeten liquid preparations with sucrose to aid compliance, and this in turn increases their viscosity. Some of the constituents of these syrups are acidic and are capable causing erosion of the dentiture.

Objectives: This in vitro study aims to evaluate the endogenous pH, titratable acidity and viscosity of different syrups sampled from different pharmacy stores in Benin City.

Methods: Sixteen (16) commonly used syrups were evaluated. The pH of each syrup was determined using a digital pH meter. The titratable acidity was assessed by titrating 0.1 N sodium hydroxide solution against 30 ml of each syrup until a pH of 8.2 was reached. The viscosity of the syrups was determined using a suspended level viscometer.

Results: The pH of the syrup brands ranged from 3.25 to 6.18. All the syrups had an acidic pH and 82% of the samples showed pH below the critical value of 5.5 which is capable of causing enamel dissolution. The titratable acidity of the syrups ranged from 0.93-7.50 g/100 ml while the kinematic viscosity of the syrups ranged from 6.51- 2 -1 75.96 mm S .

Conclusion: The outcome of this study confirms that all syrups investigated had high values of pH, titratable acidity and viscosity.

1 背景：长期以来，药用糖浆已广泛应用于儿科临床（paediatric practice），用于疾病治疗、对症姑息治疗，甚至作为食品补充剂/造血补充剂（haematinics）。制药企业常以蔗糖对液体制剂进行矫味，以提升患者用药依从性，但此举会同时增加制剂的黏度。此类糖浆的部分成分呈酸性，可造成牙体侵蚀。
2 研究目的：本体外研究（in vitro study）旨在评估采自贝宁城各药房的不同糖浆的自身pH值、可滴定酸度（titratable acidity）及黏度。
3 研究方法：本研究共纳入16种临床常用糖浆进行评估。采用数字pH计测定各糖浆的pH值；通过以0.1 N氢氧化钠溶液滴定30 mL待测糖浆至pH值达8.2，以测定其可滴定酸度；采用悬式粘度计（suspended level viscometer）测定糖浆的黏度。
4 研究结果：受试糖浆的pH值范围为3.25~6.18，所有样品的pH值均呈酸性，其中82%的样品pH值低于可造成牙釉质溶解的临界值5.5。糖浆的可滴定酸度范围为0.93~7.50 g/100 mL，运动黏度（kinematic viscosity）范围为6.51~75.96 mm²·s⁻¹。
5 研究结论：本研究结果证实，所有受试糖浆的pH值、可滴定酸度及黏度均处于较高水平。