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Standard dilution analysis (SDA) is a new calibration method that combines the principles of internal standardization and standard additions. The current work evaluated the feasibility of SDA automation using a flow-injection system (FIA). The FIA-SDA system was applied to sodium determination in biodiesel samples and certified reference materials (CRMs) by flame atomic emission spectrometry (FAES). Lithium was employed as internal standard in all determinations. The results for Na determination in five CRMs using FIA-SDA were in agreement with certified values at the 95% confidence level (t-test). For comparison purposes, Na was also determined by the traditional methods of external standard (ES), standard additions (SA) and internal standardization (IS). Recoveries showed increased accuracy following the sequence ES (181-202%) b IS (67-72%) b SA (111-126%) b FIA-SDA (94-98%). FIA-SDA provided more accurate and precise results than ES, SA and IS for Na determination in biodiesel and CRMs by FAES.

Establishing fast, simple, low-cost, and efficient sample preparation procedures to determine elements in foodstuffs is a relevant aspect for nutritional and health purposes. For this reason, the recently proposed closed-vessel conductively heated digestion system (CHDS) was evaluated for the digestion of milk powder, chocolate powder, and soluble coffee samples aiming for Ca, Cu, Fe, K, Mg, Mn, Na, and Zn determinations by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and Cd, Mo, and Se determinations by inductively coupled plasma mass spectrometry with tandem configuration (ICP-MS/MS). The accuracy was evaluated by analyzing two milk certified reference materials digested by the CHDS and a microwave oven for comparison. When using the CHDS, recoveries for the analytes varied from 91 to 104 %. For microwave digestions, recoveries within the 94-109 % intervals were obtained. The method was then applied to the samples. For comparative purposes, the analytes were also determined in the samples after microwave digestion, and the results between the two digestion systems showed no differences based on a paired t test at a 95 % confidence level. Similar analytical blanks were obtained because quartz digestion tubes were used in both digestion systems. The CHDS with quartz tubes is an interesting alternative for laboratories dedicated to large-scale routine analysis because volatile elements usually found in very low concentrations in food samples such as Cd and Se can also be determined.

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