Determination of phosphate concentration and pH in artificial tear drops.

Abstract Objective To determine phosphate concentration and pH in artificial tear eye drops commercially available in Spain. Materials and methods A total of 71 examples of artificial tear preparations were identified in a search of Vademecum 2014 and the Spanish Medicines Agency website. In the 24 artificial tear products containing phosphates, quantification of these was performed by ultraviolet molecular absorption spectrophotometry, and the determination of pH was performed using scan image analysis algorithms of pH strips. Results Of the 71 artificial tears tested, 24 contained phosphate among their excipients in the data sheet, three of which had a concentration level below detection limit ( p  = 0.0196) and hyaluronate ( p  = 0.0067). Statistically significant differences were found between products containing preservatives (32.39 ± 20.91 mM), and preservative free ones (8.49 ± 11.98 mM) ( p  = 0.0498). However, no difference was found between multidose (20.21 ± 26.91 mM) and unidose (9.31 ± 14.39 mM) samples, or between brand name (15.44 ± 23.3 mM) and generic eye drops (20.81 mM). The mean pH was 6.93 ± 0.26 (6.2–7.22). No statistical correlation was detected between phosphate concentration and pH (Spearman's Rho −0.1089 and p  = 0.6125). Conclusion A total of 24 (33.8%) of the 71 artificial tears contained phosphate. We believe identifying the phosphate concentration of artificial tears is useful information in order to avoid complications in high-risk patients.