Evaluation of Modifier Chemical for Metal and Metaloids Analysis by Graphite Furnace Atomic Absorption Spectrometry

Graphite Furnace Atomic Absorption Spectrometry (GF-AAS) is not a new method in chemical analysis, especially for metals and metalloids, unfortunately there are a lot of laboratories in Indonesia that still not used it correctly, whereas if used it correctly, the method will be an excellent and can be a reference method. This review focus on the kinds of interferences in the GF-AAS such as spectral, physic and chemical interferences and alsoon the use of a lot of kinds of chemical modifier that very important part in analysis by GF-AAS, however it is often unused because of the difficulty. It is noted that highest absorption level from each analyte is different even though used the same modifier and ashing temperature, therefore the selection of chemical modifier is important to find the appropriate modifier for each analyte and their matrixes

Pengembangan Material Serbuk Silika Untuk Identifikasi Sidik Jar!

Development of powder material for fingerprint identification has become Indonesian Department of Safety and Defense priority, especially it was written in the National Research Agenda 2006 -2009. Until now Indonesia still imported thepowder from United States and Japan. Powder fineness is one of the important factors, because finer the powder, more easily it stick to the latent fingerprint and better visualization result will be obtained. In this research, nanosilica was fabricated by used TEOS (tetraethoxysilane) as precursor. Nanosilica is an adhesive material in fingerprint powder while carbon is a coloring agent. In this research nanosilica and carbon black composition was optimized, and the powders were characterized and tried in order to get afingerprint powder which have a better quality to be used by National Police and therefore it can support Indonesian autonomy in safety and defense

Penentuan Kadmium Dalam Produk Perikanan Dengan Graphite Furnace Atomic Absorption Spectrometry

Penentuan kadmium dalam produk perikanan telah dilakukan menggunakan Graphite Furnace AtomicAbsorption Spectrometry (GF-AAS) dengan magnesium nitrat sebagai matrix modifier, platform atomizationtype A dengan sensitifitas yang tinggi untuk pengukuran kadmium, dan koreksi latar belakang Zeeman. Metodeanalisis telah divalidasi berdasarkan parameter-parameter kimia analitik. Sebanyak 0,5 g sampel produkperikanan didestruksi menggunakan microwave digestion systems dengan menambahkan 5 mL asam nitrat pekatdan 2 mL hidrogen peroksida 30%, kemudian larutan hasil destruksi diencerkan hingga 25 g. Dari larutan inidibuat sederet larutan untuk pengukuran secara adisi standar, dan diukur dengan GF-AAS. Akurasi metodedilakukan dengan menganalisis bahan acuan bersertifikat DORM 3 Fish Protein Certified Reference Materialfor Trace Metals dari National Research Council Canada dengan nilai recovery sebesar 99,9 ± 0,8%. Dari hasilpenelitian ini diperoleh kadar kadmium dan ketidakpastiannya sebesar 0,273 ± 0,025 mg kg-1berdasarkan beratkering

Penentuan Logam Besi Dan Seng Total Dalam Produk Perikanan Menggunakan Flame Atomic Absorption Spectrometry Dan Pengukuran Nilai Ketidakpastiannya

Besi (Fe) dan Seng (Zn) merupakan unsur yang berguna bagi manusia. Keberadaan logam Fe dan Zn dalam produk perikanan yang cukup kecil (trace), mudah tekontaminasi oleh kondisi lingkungan, dan metoda preparasinya yang komplek menyebabkan penentuan logam Fe dan Zn ini cukup sulit, sehingga perlu dicari suatu metoda uji yang valid dan akurat. Dalam penelitian ini dilakukan pengembangan metoda standar American of Analytical Chemistry (AOAC) tahun 2005 no. 999.10 dengan menggunakan bahan acuan bersertifikat DORM 3 (Fish Protein Certified Reference Material for Trace Metal) dari National Research Council of Canada (NRCC) untuk menguji keakuratan dan ketertelusuran hasil ke Standard Internasional (SI). Metoda ini sudah divalidasi berdasarkan parameter-parameter kimia analitik. Hasil penelitian menunjukkan rata-rata kadar Fe dan Zn dalam sampel perikanan sebesar 178 ± 14 mg.Kg-1 dan 59,8 ± 6,6 mg.Kg-1 (berat kering) dengan faktor cakupan 2 dan tingkat kepercayaan 95%, yang berada pada rentang yang ditentukan 183,5 ± 4,3 mg Kg-1 and 60 ± 1,1 mg Kg-1.Kata kunci : Fe, Zn, trace, CRM, perikanan Iron (Fe) and Zink (Zn) are essential elements for human being. Determination of this elements in fish products is quite difficult because of Fe and Zn content in trace level, easy to be contaminated by the environmental conditions, and, complex preparation methods so that it is needed to find a good and accurate method. In this paper, we have developed a standard method from American of Analytical Chemistry (AOAC), 2005, no. 999. using DORM 3 as Certified Reference Materials (CRMs) to check accuracy and traceability’s results to Standard International (SI). The method has been validated according to analytical parameters. The results showed that means of Fe and Zn concentration in the investigated fish product were 178 ± 14 mg.Kg-1 and 59.8 ± 6,6 mg.Kg-1 respectively with coverage factor 2 and 95% level of confident, and in range of expected mass were 183,5 ± 4,3 mg.Kg-1 and 60 ± 1,1 mg.Kg-1in dry basis

Rapid, precise quantification of large DNA excisions and inversions by ddPCR.

The excision of genomic sequences using paired CRISPR-Cas nucleases is a powerful tool to study gene function, create disease models and holds promise for therapeutic gene editing. However, our understanding of the factors that favor efficient excision is limited by the lack of a rapid, accurate measurement of DNA excision outcomes that is free of amplification bias. Here, we introduce ddXR (droplet digital PCR eXcision Reporter), a method that enables the accurate and sensitive detection of excisions and inversions independent of length. The method can be completed in a few hours without the need for next-generation sequencing. The ddXR method uncovered unexpectedly high rates of large (> 20 kb) excisions and inversions, while also revealing a surprisingly low dependence on linear distance, up to 170 kb. We further modified the method to measure precise repair of excision junctions and allele-specific excision, with important implications for disease modeling and therapeutic gene editing

Systematic decoding of cis gene regulation defines context-dependent control of the multi-gene costimulatory receptor locus in human T cells

Cis-regulatory elements (CREs) interact with trans regulators to orchestrate gene expression, but how transcriptional regulation is coordinated in multi-gene loci has not been experimentally defined. We sought to characterize the CREs controlling dynamic expression of the adjacent costimulatory genes CD28, CTLA4 and ICOS, encoding regulators of T cell-mediated immunity. Tiling CRISPR interference (CRISPRi) screens in primary human T cells, both conventional and regulatory subsets, uncovered gene-, cell subset- and stimulation-specific CREs. Integration with CRISPR knockout screens and assay for transposase-accessible chromatin with sequencing (ATAC-seq) profiling identified trans regulators influencing chromatin states at specific CRISPRi-responsive elements to control costimulatory gene expression. We then discovered a critical CCCTC-binding factor (CTCF) boundary that reinforces CRE interaction with CTLA4 while also preventing promiscuous activation of CD28. By systematically mapping CREs and associated trans regulators directly in primary human T cell subsets, this work overcomes longstanding experimental limitations to decode context-dependent gene regulatory programs in a complex, multi-gene locus critical to immune homeostasis