Measurement of solution properties and molecular weight of hydroxyethyl starches using multi-angle laser light scattering: An interlaboratory comparison.

The solution properties of hydroxyethyl starch (HES) vary significantly owing to different measurement parameters adopted and sample structures. Here, a round-robin study was conducted to compare inter-laboratory measurements of solution properties, weight-average molecular weight (Mw), and molecular weight distribution of four HES candidates covering the low- and medium-molecular-weight range, and 50 commercially available HES 130/0.4 drug samples. Analysis was performed using size exclusion chromatography (SEC) combined with multi-angle laser light scattering (MALLS) and differential refractive index (dRI) detectors. The results indicate that HES molecules in the Mw range of 17,000-130,000, with varying degrees of substitution (between 0.4 and 0.8), yielded a refractive index increment (dn/dc) value of 0.145 ± 0.003 mL/g (solvent: acetic acid-sodium acetate buffer; wavelength: 658 nm) and that the second virial coefficient (A2) is correlated with Mw. The SEC-MALLS-dRI method for Mw determination of HES demonstrated good inter-laboratory reproducibility; however, the study findings suggest that column specifications should be added for HES quality standards. Comparing Mw results obtained using common and experimentally corrected dn/dc and A2 values revealed an influence of dn/dc and A2 on Mw, indicating that the Mw acceptance criteria of HES quality standards should be adjusted.

[A survey of first molar caries among primary school students in Lishui].

PURPOSE: To elucidate school age students' oral health status in Lishui city and monitor caries tendency of their first molars. METHODS: Four hundred and forty-eight primary school students of the first and second grades were cluster sampled from the urban and suburb districts. The first molar crown caries were measured and their oral health caring measures were investigated. RESULTS: The results showed that suburb children's DMFT and first molar caries prevalence were both higher than the children in the urban district, but the time of tooth brushing was obviously lower. The results also showed the most important influencing factors of caries were tooth brushing, followed by age, districts, and gender etc. CONCLUSION: It is suggested that we should enforce the oral health care education and promotion, especially in the suburb area.