Dear all,

I am working on estimation of trace metals in the ambient fine particulate matter using Agilent 4200 MP-AES. In this study, Quartz fiber filters (47mm d) have been used for the collection of particulate matter in the ambient air. The sampled filters were extracted with HNO3+HCl+HF using a microwave reactor. The extracts were then further diluted to 50 mL using 6% HNO3 and injected in MP-AES for the estimation of trace metals present. However, I have observed some abnormal intensities for Sb (antimony) from the quartz filter extracts.

What could be the reason for the negative intensities and how to overcome this negative intensities.

I am attaching the intensities for Sb in standards, blanks and quartz filter samples.

Sample Type Element Wavelength Selected Intensity

Standard (100 ppb) Sb 217.581 nm 302.61

Standard (500 ppb) Sb 217.581 nm 1152.02

Milli Q Water Blank 1 Sb 217.581 nm 330.63

Milli Q Water Blank 2 Sb 217.581 nm 477.08

Milli Q Water Blank 3 Sb 217.581 nm 739.47

Quartz filter sample 1 Sb 217.581 nm -1285.54

Quartz filter sample 2 Sb 217.581 nm -1163.47